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TECHNICAL REPORT NO. 12068 /

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DRIVELINE ANALYZER M151 1/4-TON UTILITY TRUCK

FINAL REPORT

10 JULY 1975

TACOM MOBILITY S\

C2~ Northrop Corporation

,m At/ Anaheim, California

D D C

DEC 19 1975

D

For Diagnostic Equipment Function Research, Development and Engineering Directorate

MOBILITY SYSTEMS LABORATORY

ARMY TANK AUTOMOTIVE COMMAND Warten. Michu

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Technical Report No. 12068

ÜRIVELINE ANALYZER

M151 1/4-TON UTILITY TRUCK 0 /

/ fl ^FINAL REPirr, - I

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A. D./ßeBolt^

P. J./Leibert /

L. V./Rennlck f

Northrop Corporation

Electro-Mechanical Division

Anaheim, California

For

Propulsion Systems Laboratory

U.S. Army Tank. Automotive Command

Warren, Michigan

£ Contract/DAAE#7-73-C-0116 7

Distribution Halted to U.S. Oov't. agencies onlyf Test and Evaluation; JJJJ£C 1975. Other requests for this "document must bo referred to US/TlT^COM

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DEC 19 1975

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The findings in this report are not to be construed as

an official Department of the Army position, unless so

designated by other authorized documents.

2 station of c«.rcU1 produc[s ln

not constitute an official -„,< -=h product8.

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ABSTRACT

The objectives of this development program were to determine the feasibility

of using data obtained from measuring discrete selected parts of vibration

signatures for Army vehicle driveline diagnosis and to provide the U.S. Army

Tank Automotive Command (TACOM) with an advanced development model driveline

analyzer designed to identify faulty driveline assemblies of an Army M151A2

1/4-ton utility truck. The development program performed by Northrop included

the correlation of simplified analytical models to empirical data, and the

design, fabrication, and functional test of one portable driveline analyzer

test set complete with sensors and a ramote display console.

Analytical models to determine how driveline components and assemblies gen-

erate excessive vibration were developed and used to identify vibration fea-

tures that were potentially good indications of faulty components. Following

this initial effort, the driveline assemblies of an M151 vehicle were instru-

mented for vibration and shaft rotation data. During road test, the data was

recorded on magnetic tape and was analyzed on Northrop computers to develop

power spectral density plots. These plots were used to provide empirically

derived excessive vibration features of good and bad assemblies.

The analytically derived vibration features then were correlated to the

empirically derived features to identify errors in either of the processes.

Good correlation of analytical and empirical data was used as criteria for \

selecting features that would provide the highest probability of detecting

faulty driveline assemblies and the lowest probability of identifying a good

assembly as being bad. From this analysis, vibration features were selected

that were compatible with a simplified road test and that were practical for

this application.

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A portable test set was designed and constructed, consisting of a driveline

analyzer chassis, a remote display console, and a set of sensor assemblies. ]

The driveline analyzer chassis contains amplifiers, programmable filters, i

counters, phase-locked loop circuits, and a digital computer with both random

access and read-only memories. The remote display console contains vehicle

operator instruction displays.

Digital computer programs were prepared for use witli the driveline analyzer \

test set to provide the vehicle operator instructions, gather the vibration

data during the vehicle road test, analyze the data, and display test results

in terms of faulty driveline assemblies. |

The driveline analyzer set was tested utilizing simulated test data and data

recorded on magnetic tape. Sensor installation compatibility, test sequence,

and vehicle control data acquisition processing and display have been verified I

on the M151 vehicle.

The test set was demonstrated to TACOM personnel using simulated and recorded

data in the labcratorv. Installation of the test set on an M151 vehicle was f

also demonstrated. After this demonstration to TACOM, Northrop conducted a j

number of road tests which demonstrated the ability of the driveline analyzer

to detect drive shaft, U-joint, engine vibration, and differential types of

faults.

I

This contract was conceived to assist TACOM in their goal of advancing the

technology in the field of Army vehicle diagnostics. The M151 driveline t

analyzer feasibility model has been delivered to TACOM for test and evalua-

tion. The driveline analyzer has verified many of the diagnostic concepts;

however, further testing and engineering improvements are necessary to deter- \

mine the adequacy of the diagnostic concepts.

1

FOREWORD

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This report is submitted in accordance with Contract Data Requirements List

sequence number A003 of the U.S. Army Tank Automotive Command (TACOM) Contract.

DAAE07-73-C-0116. The contract was awarded in February 1973 and called for

Northrop Corporation to determine the feasibility of using vibration-diagnostic

techniques for Army vehicle driveline maintenance, and to provide TACOM, for

their test and evaluation, with an advanced development model Driveline

Analyzer designed to identify faulty driveline assemblies of an Army M151A2

1/4-ton utility truck. Work on the contract was performed at Northrop Corpo-

ration, Electro-Mechanical Division, Anaheim, California, under the technical

guidance of the TACOM Diagnostic Equipment Function Project Engineer, Peter Carland.

v/vi

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CONTENTS

P;ij...

I 1

INTRODUCTION 1-1

1.1 Background 1-1 1 .2 Ob H'ct i ves I -J 1.3 Scope ol Work I-.'

ESTABLISHMENT OF HARDWARE DESIGN REQUIREMENTS 2-1

2.1 Empirical Approaches 2-1 2.2 Analytical Approaches 2-2 2.3 Technical Approach 2-3 2.4 Selection of Fault Types 2-8 2.5 Analytical Analysis 2-10 2.5.1 Discrete Frequency Models 2-11 2.5.2 Vibration Due to Impulsive Forces 2-21 2.5.3 Cross-Coupled Vibration 2-22 2.6 Empirical Techniques 2-26 2.6.1 Vibration Recording and Analysis 2-27 2.6.2 Impulse Response Measurements 2-29 2.6.3 Analysis of Recorded Vibration 2-31 2.. Comparison of Analytical and Empirical

Results 2-38 2.8 Selection of Test Techniques 2-43 2.8.1 Wheels, U-.Joints and Drive Shafts 2-49 2.8.2 Differential, Transmission and Engine 2-5 2 2.8.3 Clutch 2-55 2.8.4 Selected Test Techniques 2-55

IMPLEMENTATION OF THE DRIVELINE ANALYZER DESIGN .... 3-1

3.1 Overall Concept 3-1 3.2 Central Processor Requirements 3-3 3.2.1 Central Processor Implementation 3-4 3.3 Vehicle Operational Display Requirements . . . 3-8 3.3.1 Operator Display Implementation 3-8 3.3.2 Description of the Displays 3-9 3.4 Test Result Display Requirements 3-10 3.4.1 Test Result Display Implementation 3-12 3.4.2 Description of the Test Result Messages .... 3-12 3.5 Sensor and Signal Conditioning Requirements . . 3-13 3.6 Driveline Analyzer Specifications 3-14 3.7 Hardware Pictorials 3-17

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CONTENTS (Cont iniied)

Section Pajje

4 TEST AND EVALUATION 4-1

4.1 Bench Tests of the Drivelino Analyzer 4-2 4.2 Vehicle Compatibility Tests 4-6 4.) On-the-Rond Tests 4-6 4.1.1 Drive Shaft U-.loint Tests 4-7 4.3.2 No Weight on Drive Shaft Test 4-H 4.3.1 6-Ounce Weight on Rear Drive Shaft lest .... 4-10 4.1.4 6-Ounce Weight on Front Drive Shaft Test . . . 4-11 4.1.5 On-tbe-Road Differential Test 4-14 4.1.6 On-the-Road Test at Wheels 4-16 4.4 Summary of Test Results 4-lb

5 SUMMARY 5-1

6 CONCLUSIONS 6-1

7 RECOMMENDATIONS 7-1

7.1 Fault Simulation 7-1

8 DISTRIBUTION LIST 8-1

I)D FORM 14 73

ILLUSTRA'i IONS

Figure Page

2-1 Driveline Analyzer Development Procedure 2-4 2-2 Ball Bearing Relative Frequencies 2-12 2-3 M151 Basic Drive Train Data and Sensor Locations .... 2-17 2-4 Third-Gear Driveline Shaft and Gear Mesh Races 2-18 2-5 Effects of Worn Teeth on Vibration Spectrum 2-21 2-6 Typical Coupled Vibrations 2-23 2-7 Generalized Technique Used to Identify Excessive

Vibration with Elimination of the Effects from Other Assemblies 2-24

2-8 Data Process 2-28 2-9 I' 'ilse Response Measurement 2-30 2-lü M 1A2 Driveline Impulse Responses 2-30 2-11 Typical Analysis of Vibration 2-31 2-12 Synchronous Analysis of Vibration 2-32 2-13 Typical Computer Printout 2-33 2-14 Interpretation of PSD Amplitude and Frequencies .... 2-36 2-15 Relationship of Plot to Shaft Rotation 2-38 2-16 PSD of Rear Differential 2-39

viii

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I 7.2 Test Program 7-1 i 7.1 Rotation Sensors 7-2

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2-17 2-18

3-1 3-2 3-3 3-4 3-5 3-6 3-7 i-8 3-9 4-1 4-2

4-3

5-1

High-Frequency PSD Plot Driveline Analyzer Feature Extraction and Analysis Processes

Drive line Analyzer Block Diagram Power/Performance Comparison of Various Minicomputers, Nortlirop CMOS Processor Remote Display Console Panel Drivellne Analyzer Chassis In Place Remote Display Console in Place Front Differential Sensor Assembly Instated Rear Differential Sensor Assembly Installed Transmission Sensor Assembly Installed Synchronous Signal Simulation riench Test - Input Synchronous Signal Amplitude Versus Driveline Analyzer Reading Operated in Drive Shaft Test Mode

Laboratory Tests Using Magnetic Tape Recordings from On-the-Road Test

Driveline Analyzer Block Diagram . -

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2-41

2-46 3-2 3-6 3-7 3-9

3-18 3-18 3-19 3-19 3-20 4-4

4-4

4-6 5-3

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2-2 2-3 2-4 3-1 1-2 4-1

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TABLES

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Compliance to Hardware e Summary nf w ,a,uwar<? Specif loan y ot Hardware/Snff.. IIlcation . .

'«-/Software Verify verification.

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I I I 1 I I 1 I I I

SECTION 1

INTRODUCTION

This document is the final technical report for a Northrop Corporation advanced

development contract for one experimental model driveline analyzer. The per-

formance goal of the M151 vehicle driveline analyzer is to identify the faulty

driveline subassembly that is the source of abnormal vibrations.

The report is in accordance with Contract Data Requirements List sequence

number A003 of the U.S. Army Tank Automotive Command (TACOM) contract, DAAE-07-

73-C-0116. The contract was awarded in February 1973 and called for Northrop

Corporation to design and fabricate for TACOM test and evaluation, a driveline

analyzer designed to detect faulty driveline subassemblies for the Army's

M151 1/4-ton utility truck. Work on the contract was performed at the

Electro-Mechanical Division, Anaheim, California, under the technical guidance

of the TACOM Dia^ostic Equipment Function Project Engineer.

1.1 BACKGROUND

In the U.S. Army vehicle maintenance system there exists a difficulty for even

the most experienced mechanic to correctly diagnose a driveline subassembly

rnaifunction. Good assemblies are invariably sent to the depot level for repair

when such repair is not appropriate. After one of the driveline subassemhlies

is replaced, it also becomes necessary to validate the repair afte is made, :er replacement

This driveline analyzer has been developed with a long term developmental

objective to become an aid to the Army mechanic in solving the diagnostic prob-

lem of accurately identifying a faulty and/or misaligned driveline assembly

within an Army vehicle and also to serve as an aid in verifying that the sub-

assembly replaced is installed correctly and did, in fact, correct the fault.

1-1

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1.2 OBJECTIVES

The objectives of this development program were to determine if it is feasible

to use vibration techniques for Army vehicle driveline diagnosis and to pro-

vide TACOM with a.i advanced development model driveline analyzer designed to

identify faulty driveline assemblies of the M151 1/4-ton utility truck. The

development program performed by Northrop included the correlation of simpli-

fied analytical models CO empirical data, and the design, fabrication, and

functional test of one portable driveline analyzer set complete with sensors and remote display console.

1.3 SCOPE OF WORK

The contract specification required Northrop to furnish the supplies and ser-

vices necessary to design and fabricate, for TACOM test and evaluation, a

driveline analyzer designed to detect faulty driveline assemblies in the M151 series 1/4-ton trucks.

The general performance requirements for the driveline analyzer were estab- lished as:

a. Design hardware that will detect t*e following:

1. Slipping clutch

2. Drive sh^ft imbalance

3. Drive shaft misalignment

4. Excessive differential vibration

5. Wheel assembly imbalance or bent axle

6. Excessive engine vibration

7. Excessive vibration due to wheel U-joints

8. Excessive transmission vibration

9. Excescive vibration due to drive shaft U-joints

b. Have packaging dimensions approximately 12 x 18 x 18 inches

c. Be insensitive to vibration during transportation and suitable for

use on a moving test vehicle

I 1-2

d. He powered by vehicle's electrical system

1 1 !

I I 1 I i I I I I I I I I 1

e. Be simple enough to be installed and operated by one mechanic at

Direct Support level of maintenance

f. Have self-testing capabilities to determine if it is operating

properly and within tolerances

g. Have automatic test capabilities in which each driveline subassembly

is tested and results are displayed to indicate good or bad condition

h. Be capable of being installed in less than 10 minutes and having a

te.'t time of less than 8 minutes.

The following project tasks outline the approach used in reaching the objec-

tives and meeting the hardware performance requirements above.

a. Perform ai. analytical projection of the specific sources of vibra-

tion expected to be found in the M151 driveline subassemblies.

b. Obtain empirical data and correlate to the analytically determined

features. From this, make the final selection of test technique and

finalize the driveline analyzer configuration.

o. Design, construct, and test the driveline analyzer set.

1-3

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SECTION 2

ESTABLISHMENT OF HARDWARE DESICN REQUIREMENTS

Wlien Northrop established the technical approach to defining the design require-

ments for the driveline analyzer hardware, consideration was taken of the suc-

cesses and failures of similar programs that had attempted to use vibration as

a diagnostic tool.

2.1 EMPIRICAL APPROACHES

1 1 I I i I I r i i

Empirical approaches involved gathering large volumes of machinery vibration

data for various types of machines. Vibration data was analyzed using var-

ious statistical techniques to develop discernable features. Maintenance and

failure reports were gathered for each of these machines. Attempts were then

made to correlate specific vibration features to types of machinery fault.

Theoretically, this approach is sound and should provide good diagnostic and

prognostic features.

One of the empiri-'U approaches has met with some success when applied to

simple rotating machinery; however, this approach has been frustrated with

failure when Northrop attempted to develop reliable diagnostic and prognostic

tools for complex gear train vibrations. This failure could be related to the

highly complex nature of the vibration spectrum and amplitude. Each component

radiated at a variety of frequencies and amplitudes which were dependent on

machine speed and load and the good or bad condition of the part. A faulty

component also coupled mechanical stresses to good components and caused them

to modify their vibration characteristics.

Our attempt to cross-correlate highly complex vibration data to sets of com-

plex, unreliable failure reports resulted In frustrating lack, of success.

2-1

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1). It was impractical to expect to maintain or even locate a vehicle

with only one controlled fault. Normally, there would be cases where

unexpected faults would exist.

c. The data required to define the vibration related to a particular

raulty assembly must not contain a large number of complex terms.

Complicated terns would require extensive development and would indi-

cate test equipment too ; implex to be practical for this application.

d. it would be impractical to expect the vehicle to be operated under

precisely controlled conditions during the test.

e. Output data must not require interpretation by experienced personnel.

It must identify the most probable part causing excessive vibration.

f. It would be impractical to solve both the diagnostic and prognostic

problems in one step. The initial objective should be limited to the

identification of driveline assemblies which were causing excessive

vibration.

g. It is impractical to expect universal agreement as to the goodness or

badness of the vehicle's components.

h. The approach must recognize the limitations of empirical and analy-

tical approaches.

2.3 TECHNICAL APPROACH

Procedures used to develop the driveline analyzer technology are shown in Fig-

ure 2-1. The approach uses both analytical and empirical techniques. The two

techniques complement each other in a way to overcome some of their individual

disadvantages. The limitations of the analytical and empirical approaches, the

time available to conduct tests and develop test techniques, and the limited

availability of vehicles with various faults were constraints on the combined

approach.

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DRlVFUNE ANALYZER DEIIVtRED 10 TACOM

Figure 2-1. DRIVELINE ANALYZER DEVELOPMENT PROCEDURE

2-4

1 i 1 I

As depicted in the driveline analyzer development procedure of Hgure 2-1,

t lie following steps were taken:

a. LsLablisiiment oi 1'erj ormance Requirements and Constraints

1. Development application w is limited to one chicle to reduce the

complexity of having to test several vciiicles. This allowed more

time to concentrate on one vehicle, thii." enhancing probability of

success and proof of feasibility,

2. Failure levels were define ' s excessive vibration; thai is,

vibration levels tnat would cause a vehicle operator to request

maintenance ai.tiin. This allowed the basic principles of selected

techniques to be tes'ed and also eliminated the time-consuming

tasks of determining whether a marginal assembly was good or bad.

This constraint eliminated tests that related more to the engi-

neering design evaluation or to the production testing requirements

for the venicle.

3. The test set was to be designed to detect which of the driveline

assemblies was causing the most serious vibration. There would

be no attempt to detect which component within the assembly

had failed.

4. The test .^et was to be practical for use on a simple road test.

This meant that precise speeds and loads could not be a require-

ment and that road vibration must be expected as an input to the

system during the diagnostic test.

5. All techniques considered must be compatibl with the concept of

a test set that is portable, low cost, and practical for attachment

and use by a Direct Support level mechanic.

k* Selection of Candidate Test Techniques - Candidate techniques were

selected from various machinery vibration test techniques that had

been developed by Ncrthrop and others. This selection process took

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into consideration the constraints and test requirements developed

by the previous step. Techniques that required large expensive equip-

ment or which did not provide identification of faulty assemblies

without manual interpretation were discarded. Techniques that required

large volumes of empirical data or involved long expensive analysis

were also discarded. The probability of success based on experience

with the technique and engineering judgement was also used as a

selection criteria.

Analytical Analysis of Drivellne Assemblies - The Ml51 vehicle

driveline assemblies were analyzed to determine characteristic vibra-

tion features that were applicable to the selected test techniques.

Quantitative data was provided for frequency and qualitative data was

provided for amplitudes or left for empirical evaluation. Also, math-

ematical models were developed for cross-coupling factors between

assemblies.

In all cases, attempts were made to limit the analytical work to prac-

tical levels that could be accomplished within the time and cost con-

straints of the program.

Empirical Analysis of Driveline Assemblies - This analysis consisted

of recording and analyzing vibration data to develop power spectral

density plots. These data were recorded while operating the vehicle

on the road. Analysis was oriented to supporting selected test tech-

niques and to complement the analytical analysis. Other tests were

conducted to determine the relative coupling of vibration between

assemblies.

Comparison of Analytical and Empirical Data - Analytical data was

used to identify sources of frequency lines in the vibration data and

to provide explanations for vibration characteristics. The empirically

derived data was used to provide characteristic amplitudes and coupl-

ing factors that are much more difficult to derive analytically. The

comparison process provides an accuracy check on both analytical and

empirical work. Areas which did not correlate and could not be ex-

plained pointed to the need for additional analytical and empirical

2-6

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work. In ill cases, these investigations wen- limited to areas t li.it

would support tin' objectives of the driveline analyzer and would

support the selected test techniques. The end result was a set of

vibration features that .:ould he used for driveline diagnostic

analysis.

f. Test Technique Design - A detailed design ol the selected test

techniques was conducted. This design was based on test requirements,

selected test techniques, and on the analytical and empirical data.

This process considered the impact on hardware and the possibility of

using common hardware to conduct more than one test.

8- Design and Manufacture - This procedure involved the selection of a

■pecific test equipment design and the fabrication of an experimental

model of the driveline analyzer. Trade-off studies were conducted

to determine whether analog or digital processes should be used, and

to determine whether or not the driveline analyzer test set should use

a hard-wired or stored program technique. The use of commercially

available or specially designed equipment was also considered. The

design was completed and an experimental model of the driveline

analyzer was manufactured using good commercial practices.

h Test of the Experimental Model - Bencli tests were conducted to

demonstrate that the driveline analyzer performed to the design re-

quirements. These bench tests were conducted using laboratory equip-

ment to provide simulated vibration data. In some cases, actual

vibration data recorded on magnetic tape was used.

The driveline analyzer test set was attached to the M151 vehicle to

demonstrate compatibility with the vehicle and performance of the

test. Limited evaluation of the driveline analyzer test set on the

vehicle, using good and bad assemblies, was conducted.

2-7

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2.4 SELECTION OF FAULT TYPES

The requirement for fault detection was to identify driveline assemblies that

were causing excessive vibration. Excessive vibration was defined as an on-

the-road vibration level that would cause the vehicle operator to request

maintenance action. In addition, the driveline analyzer was to provide an

indication of the relative degree of badness. The clutch assembly was to be

tested for slippage.

Driveline assemblies were fault identified for excessive vibration due to:

a. Engine

b. Transmission

c. Rear drive shaft imbalance

d. Rear drive shaft alignment or U-joint bad

e. Front drive shaft imbalance

f. Front drive shaft alignment or U-joint bad

g. Rear differential

h. Front differential

i. Rear right wheel imbalance, bent wheel, or bent axle

j. Hear right wheel U-joints

k. Rear left wheel imbalance, bent wheel, or bent axle

1. Rear left wheel U-joints

m. Front right wheel imbalance, bent wheel, or bent axle

n. Front right wheel U-joints

o. Front left wheal imbalance, bent wheel, or bent axle

p. Front left wheel U-joints

q. Excessive clutch slippage

During the course of the contract, it became desirable to define the above

qualitative faults ir: terms of quantitative mechanical deviations and to pro-

vide examples of these faulty assemblies. It was also desirable that these

faults be typical of thosa in field occurrences and that the probability of

occurren.-'u be known.

2-8

This requirement to provide definitive data became on<> of the more difficult

tasks in the program and was only partially fulfilled. The Army could not

provide statistically significant failure reports on the driveline assemblies.

The only significant failure identified was a manufacturing deviation in the

differential which was causing failure in the field. Also identified was that

axle U-joints and drive shaft U-joints were also major sources of failure.

itne example of a differential assembly that had failed in the field and one

example of a differential housing that had a manufacturing flaw was provided

by the customer.

ihe alternative to the lack of other actual failed assemblies was to modify

good assemblies in an attempt to simulate faults that might occur. Some of

the techniques used to simulate failures were:

a. Removing of a needle bearing from a U-joinf

j b. Adding weight to drive shaft to cause imbalance

c. Adding weight to wheels to cause imbalance

d. Improperly adjusting the differential I I e. Hlsadjusting the clutch pedal to cause clutch slippage

f. Adding wrong size shims and spacers.

in many cases, the degree of part modification did not cause sufficient vibra-

tion to be considered excessive. Only one M151 vehicle with one set of spare

parts was used or. the program. As ,',. result of these deficiencies, it became

necessary to estimate the vibration that would be caused by bad parts using

extrapolation from good part data. One exception was the wheel and drive shaft

imbalance which was simulated by adding weights to the drive shaft and wheels.

The combination of empirical and analytical analysis was used to identify

vibration frequencies that were due to various gears, bearings, and shafts

within the driveline assembly. By assuming that these various parts had

failed, a partial estimate of the effects of failure were made. Road tests

later showed that these estimates were within reasonable ranges.

1 I I I I I 2-9

J.5 ANALYTICAL ANALYSIS

Theories liave been developed that relate the amplitude and frequency charac-

teristics of machinery vibration to moving parts within the machine. The

theories were used in conjunction with M151 driveline dimensional and rate of

motion data to predict the nature of its vibration and to predict how fre-

quencies and amplitude would change when various components within the drive-

line failed. Both qualitative and quantitative types of information were

derived. Quantitative data was primarily limited to frequencies generated by

moving parts. Amplitude data, changes as a function of degree of failure, and

the effects of cross-coupling between assemblies were limited to qualitative

derivation. These theories could also be used to predict how vibr.ition char-

acteristics would change as a function of vehicle speed, transmission ,;ear in

use, vehicle load, and path of operation.

The vibration characteristics derived in this way could be grouped according

to type of source and information provided. They are:

a. Vibration frequencies that can be directly related to the movement

of a specific part. The sources are mass imbalance, misalignment of

shafts, meshing of gear teeth, and bearing contact.

b. Mechanical ringing that is similar to the ringing of a bell when

impacted by the clapper. Frame assemb ies, shafts, ind gear disks

vibrate in this manner. The frequency of vibration is characteristic

of the part dimensions, material, and how it is mounted. The vibra-

tion mode, amplitude, and modulation is a function of the mechanical

forcing function.

c. Cross-coupling of forces and vibration from one assembly to another.

There are two modes of coupling: those related to variations 1n tor-

sional force transmitted along the coupling shaft, and vibration

coupled through frame and shaft members.

The analytically derived data was compared to data from actual vehicle test.

Differences indicated the need to revise analytical approaches or to improve

the data acquisition and analyses processes.

2-10

1 I I J I I

—!r~4 -,.—— •

As iho theoretical models wore confirmed by experimentell data, the model could

he treated with more confidence and extrapolated to cases that were not practical

to he confirmed by experiment. This theoretical understanding oi how vibration

is generated ami the nature of iis change as a (unction of part failure was used

to develop and select Improved test techniques.

2.5.1 IH_screte •" rJ'_9ü^l_ll<' Models

Moving parts such as shafts, bearings, and gears within a machine generate dis-

crete frequencies that can be directly correlated to the motion of the part

and to the repetitive contact of one part with another. The amplitude jf the

frequency is proportional to mass rate of displacement, contact force, and

their time rate of change.

For example, sinusoidal force or vibration generated by a mass imbalance in a

rotating member is known to have a frequency equal to the rotation rate, and

its amplitude is known to bo proportional to the mass rate ot displacement. In

their pure state, these vibrations are single frequencies that are coherent with

shaft rotation. Bent or misaligned shafts generate a similar set of frequencies.

A ball, bearing generates a family of frequencies that are functions of shaft

rate, inner and outer race dimensions, number of balls, etc. Figure 2-2 shows

a derivation of these frequency elements.

The inner race is allowed to rotate through an angle ..>. such that the original

contact points (A) of ball and inner race are now at B. and B , respectively,

and the ball contact point with the outer race is at point B . The contact o

surface covered on the inner race C. = contact surface covered on the ball (• l s

= contact surface covered on the outer race C , because there was no slippage.

= Angle through which the ball has rotated about the bearing axis.

(ball train angular motion)

= Angle through whicli the ball has rotated about its own axis.

Angle through which the inner race rotated.

2-11

'*■2\1 Bt>Jfing Relat Ive Frequencies

Consider ball bearing where r = inner rate radius,

and r, ■ ball radius. b rQ = outer rate radius,

No slippage between races and balls has been assumed in the followinj derivations.

I I I !

3300

J

3

I i

Figure 2-2. BALL BEARING RELATIVE FREQUENCIES

2-12

I I I I I !

1 1 i

1 I I

|! •" Diameter nf outer race o

D ■ Diameter of inner race

Ball Turn Kate

c = c = t; 1 ll s

b =

2C o

I) 0

(' V'o 0 2

'h =

2C. l

I).

(1)

(2)

(3)

u. D Combining 1 and 2r C, = -H-2

i 2

and combining this with 3: (. - . ) U = . (U ) i b i bo

solving for ., in terms of . . b i

i). i

'b I), + I> 'i (4) 1 o

This is the rate of precision of the ball train about the bearing axis; irreg-

Ball Spin :. ,

t ularity of ball's size,

1 I

C C 2 so

~s 1) " u s s

i 2C = J, Ü

o bo

combining 5 and 6 we get

I I) o

"'s "b I)

(5)

(6)

(7)

2-13

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Replacing .. with . from 4 wc got:

1) 1) . . . L--S. (8) s i I) + I) L> v y

i o s

is the spin rate of the ball; a flat spot on the ball will cause a dis-

turbance at twice tliis rate due to its passing over the inner and outer race.

Inner Race Rate

(;i " (i " V T (9)

Frora4 b " (iTT-5")i i o

Ci ° (wi" innr -i> Di 1 o

ci ■ "i (1 -D-TV) Di (10)

i o

If there are M Balls, their angular spicing is < = — ^nd the distance between

balls along the inner race is C... = OÜ./2, in l

2« Di CiM = IT (11)

Ci

A point on the inner race will contact a new ball at the rate of -—. IM

From 10 and 11

C| ^ (1 " ITTD-> UI

i _ 1 o

CiM ä °i

Ci '"i Di ~- = — (1 " n * n ) M (12) CiM n Di + Do

This is the rate of a disturbance generated by a fault on the inner race.

2-14

I I I I I I

Outer Kace Kate

C = ... D (13) o bo

TT The distance spacinc of the balls on the outer race is C .. = — 1)

on M o

C ,, D u).M q_ b o _ b

L'oM -" D M o

and from 4

^- - - °i M C M i n X n ? (14) oM D, + D TT

i o

This is the rate of disturbance generated by a fault on the outer race.

NOTE: The above equations are in terms of radians; when used in

terms of frequency, they are 2nf.

For practical calculations of bearing frequency, the following were used for

normalized multipliers of the bearing shaft rate.

Nf ■ 1 ■ shaft frequency

= ball train precision frequency DJ + F) i o

D N =» 2N, (-—) = bail spin frequency s b b

s

N. = (1 - N )M = inner race frequency

2-15

N = (N, M) = outer race frequency o b

The above numbers apply to Timkin roller bearings as well as ball bearings

that do not have angular contact. For angular contact ball bearing, the con-

tact angle must be known.

mm*m*i* ...m-nun'Warn »ft, . ,r , ,- ,u,„; -*~U..~;«Ä^ÄSSÄ *.a>JW«- '

(»ear Frequencies N, UETH

INPUT«

N,

OUTPUT n7

NjTEETH 3300

R2 " N^l

f = t< = eccentric gear or shaft on input

Nl f„ " R_ » — f * eccentric gear or sliaft on output »2 £ W» 81

f " N R = N f = gear mesh frequency gm 1 1 1 Sj

N - N2 f , ■ —- f„ = gear beat frequency gb N2 gi

Normalizing to input sliaft, we have

N,

g2

I ft'

gm

gb

Nl-N2

Determination of various shaft speeds as a function of vehicle speed and

transmission gear is necessary for this type of analytical analysis. Figure

2-3 is a model of the M151 drive train showing the various speed ratios and

proposed sensor locations. From these data, the wheel, drive shaft, and engine

speeds were derived as a function of transmission gear ratio and speed in miles

per hour as shown in Table 2-1.

"I

1 I I I I

2-16

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I 7 R. in, si

6 ;i7

IGNITION SENSOR

(SI SLIP

ENGINE

ROTATION SENSOR

DRIVE SHAM

Figure 2-3. M151 BASIC DRIVE TRAIN DATA AND SENSOR LOCATIONS

30 IN

Table 2-1. SHAFT SPEEDS AS A FUNCTION OF MILES PER HOUR AND TRANSMISSION GEAR RANGE

1

Speed (miles/hr)

Wheel Speed

(re"/sec)

Drive Shalt

(rev/sec)

Transmission Input Speed or Kngine Speed (rev/sec)

1st (5.712)

2nd (3.179)

3rd (1.674)

4th

(1)

5 0.93 4.5 25.6

10 1.8b 9.0 40.5 28.6

20 3.72 18. 1 57.2 30.1

40 7.44 36.3 ol.O 36.3

65 UA 59.0 59.0

t I I I I I

Wheel speed and drive shaft speed are related to vehicle speed as follows:

Wheel Speed, Rev/Sec = 0.186 ~'-—- x (miles/hr) Mil-Sec

Drive shaft Speed, Rev/Sec = 0.904 -^"^ x (miles/ ir)

The easiest to Implement and the most promising vehicle operating conditions

for measurement of clutch slippage appears to be a road test in which the

2-17

.<-.-■ •.- .-- »' ■< I ,-M, ■

vehicle accelerates in fourth gear to approximately 35 miles per hour. Con-

ducting the test in fourth gear eliminates the requirement to insert elec-

tronic dividers to compensate for transmission fjear ratio. It also provides

a maximum load on the clutch at a reasonably high revolution rate.

The above- formulas were used to derive discrete frequencies generated by com-

ponents in the K151 driveline. Figure 2-4 is an example of gear mesh and

shaft rates for third gear. These rates are given in terms of drive shaft

rate. A complete list of sources and frequencies as a function of vehicle

speed in mph and transmission gears used is shovn in Table 2-2. Frequencies

generated by various bearings in the transmission, differential, and wheels

are shown in Table 2-}. In this later case, the bearings are identified by

tiieir part number. For each bearing, the frequency for inner race and outer

race, ball spin, and precision rate are given. Frequencies for speed values

from 5 to 45 miles per hour are given.

TO CLUTCH

i TRANSMISSION

1= 7

35* 20*

■11 J2i_r o>d

SHAFT SPEED OAR MESH RATIO

1 • wt 1 • 20 wd

2 • -066wd J) • 20 Ud

3 • wd 3 " 20 Wd

4 • wd 4 ■ 35u>d

5 • -0.897(jd 5 • 34.98u>d

6 • -0.0W7wd 6 ■ 42.20 wd

< • l.bHuifj ■ <"d / ■ 30.13 «d

DIFFERENTIAL

SHAFT SPED GEAR MESH RATIO

1 • u>c 1 • lijtf

A • 4.86wd A • 7wd

B • 4.86(i>d B ■ 7ud

1903

Figure 2-4. THIRD-GEAR DRIVELINE SHAFT AND GEAR MESH RATES

2-18

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2-20

I

2.5.2 Vibration^JHic to !inpu 1 s i ve Forces

I.

Wien moving parts that come in contact with each other fail, they have n ten-

dency to develop flat spots or spall pieces from the contacting surface. When

in good condition, t lie parts transmit force from one part to the other in a

smooth transition. A galled part transfer« force with sharp steps or discon-

tinuities. These forces are shown in terms o! gear teeth in Figure 2-3. The

smooth force transition of good gears generates a relative low amplitude

frequency at the fundamental toolh rate. Harmonics of this tooth rate are

usually quite low. In the case of bad gears, the sharp transition in force

generates a high amplitude signal at the fundamental and has many harmonics of

high amplitude. In a classical sense, the spectrum lias a sine x over x

envelope.

[ 1 i i i I I

J^Xn

GOOD GEAR

BAD GEAR

TOOTH RATF

TIMt.

-—S

TIME

FREU'JFNCY

Figure 2-5. EFFECTS OF GOOD TEETH AND WORN TEETH ON VIBRATION SPECTRUM

i-^UiC'i^ i.vi'V-.i^".:J -;..-.-;-.i=-->-;

2-21

v,^.^;;^«:.*;-^^ ^■44««^*^^«^Sfi5^^K^^^^^^^8^1ÄiS

W

The important diagnostic feature is the ratio of i In- iniplitude of I he higher

harmonics Lo the fundamental. For the same sei .>1 ;•,. irs, the amplitude of

the fundamental will be sensitive to the speed and load. The raLio of the

amplitude of the harmonics to the amplitude of the fundamental can be expected

to be sensitive to the amount of wear.

From an analytical point of view, specific amplitudes ot the fundamental and

its harmonics could be calculated if the forcing wave shape is known. This,

however, is lmpractic.il for complex machinery, sino tue amount of wear and

discontinuity is generally unknown. As a qua]itat ivi concept, this under-

standing of hew vibration is generated is useful. i! Identifies potential

approaches to the design of diagnostic tools and can he used to explore diagnos-

tic features using empirical techniques.

A second characteristic of the impulsive forcing fund ions are that they

excite higher frequency modes of ringing in structural elements.

in summary, failures that cause repetitive impulsive forces excite the higher

frequencies and the rates of high frequency energy tu low frequency increases

as the part fails.

2.5.3 Cross-Coupled Vibration

Vibration measured at the surface of an assembly consists of components that

are due to mechanical disturbances internal to the assembly and due to dis-

turbances that are transmitted to the subject assembly from other assemblies.

These transmitted or coupled disturbances occur in the following ways:

a. Torque variations developed by other assemblies are transmitted

through coupling shafts to the subject assembly. These torque var-

iations set up mechanical disturbances which result in additional

vibration that take on the repetitive nature of the variations in

torque. These torques can also cause gears, bearings, and shafts of

the subject assembly to generate greater amplitudes of vibration at

their characteristic frequencies.

2-22

i

b. Another assembly t_ii.it is vibrating will transmit a pan of this

vibration to the subject assembly through shafts and vehicle frame.

These vibrations are typically characteristic of the vibrating assem-

bly modified by the vibration transfer characteristics of the coupling

structures and the response characteristics of the subject assembly.

Sharp force transitions coupled through frame elements can also cause

the subject assembly to vibrate or ring in its characteristic modes.

When the subject assembly induces vibration in another assembly, this

induced vibration can be reflected back or coupled back to the sub-

ject assembly. This reflected vibration will be modified by the

coupling transfer functions and response functions of both assemblies

and their connecting members.

Ihe direction of flow of coupled vibration is shown in Figure 2-6. It should

be noted that reciprocity of coupled vibration does not always apply. There-

tore, the coupling factors in one direction is different than the coupling

in the opposite direction. A generalized technique for separating or isolat-

ing the cross-coupled effects t

Figure 2-7. -om the aetual assembly vibration i

s shown in

REAR VIBRATION INDUCED IN THE TRANSMISSION BY WHEEL FACTORS

VIBRATION INDUCED IN THE WHEEL BY TRANSMISSION FACTORS

3300

Figure 2-6. TYPICAL CUUPLEI) VIP.RAT TIONS

2-2'J

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2-24 I I

If t lit- vibration generated by assembly B is V(B) and the coupling factor

from assembly B to assembly A is KJ , then the vibration induced in assembly

A by assembly B is Kl V(B). Where VB is made up of a number of complex

vibration and mechanical stresses, Kl is the respective coupling or transfer

function factor from assembly B to assembly A and includes the response

functions of assembly A.

11 assembly A vibrates with a vibration V(A) that is due to internal sources,

then the total vibration of assembly A is V(A) + K VU. Similarly, assembly B

will have a V(B) + K VA vibration where K is the coupling factor from

assembly A to assembly B.

These expressions can be taken as the vibration detected by sensors mounted

on the assemblies and to include the transfer functions of the sensor. As

expressed in this manner, thr equation V(A) + K VB represents a voltage

output of an accelerometer mounted on assembly A.

If the accelerometer output is applied to a feature extractor that has a

transfer function F, then the output of the feature extractor is a set of

values representing long time averages of extracted features. These fea-

tures may be numbers or analog voltage representing the magnitude of a

specific frequency, average peak values over a specific time period, the

power within a specific band of frequencies, etc. In addition, an essential

quality of the feature extractor is that its averaging time be much longer

than the transport delay between assemblies and must be much longer than

the period of the lowest vibration frequency of concern. The output of the

feature extractor is therefore a set of stationary values represented by

the equation

FA x V(A) + FA x K. V(fl) A A i

2-25

,-*-.:J,.vH---:^;^--^-v.--. ■ .z*i ^i->i,.W.''>&- &£&i&9&ffii&&ii': ■-'.- ■

where F is the transfer function of the A assembly feature extractor,

Assembly B has a feature extractor output:

lß VfB) + FB x K„ V(A)

The B assembly feature may he multiplied DV a constant ''., and subtracted from

assembly A features as shown in Figure 2-7. Tills results in an output

F, x V(A) x (1-K.K,) which ccntaiis onlv the assembly A 1 eat lire and is Inde- A 12

pendent of vibrations generated by assembly H. Threshold or comparison teeh-

niques may then be applied to these features to determine whether or not the

assembly is faulty.

As derived here, the approach is qualitative in natuti, .A.i.i l< t ical derivation

of numbers for the coupling factors and constants i> impractical for complex

mechanical systems but can be evaluated experiment.! 11>. The derivation does

help in the understanding of the interactive eiiects o! one assembly on another

and to indicate processing techniques that can be used Lo separate the effects

of cross-coupling. The understanding of this process is useful in the

interpretation of power spectrum plots of vibration dat-a from the various--,

assemblies. Analysis of vibration data from tin assemblies operated under a

variety of conditions can be used to empirical!', derive values for the

coupling factor and constants.

2.6 EMPIRICAL TECHNIQUES

Empirical techniques involve the gathering, analysis, interpretation, and

evaluation of vibration data from the various assemblies while the vehicle is

I ',v.

ft r

2-26

operated. The vibrations of the vehicle assembly may be classified as being

made up of the following characteristics and related sources:

a. Those vibrations which are coherent with specific time rates of change

of components within the assemblies. These functions may be corre-

lated to functions of output shafts and their frequency value will

varv with the machine speed.

h. Ringing frequencies of frames and components within the assembly.

These frequencies are relatively constant with respect to shaft

speeds.

c. Rattles that are usually due to loose or cracked parts. These usually

have low frequency repetitive characteristics that occur at random

intervals.

d. Random vibrations that are due to road roughness, etc.

A second approach uses vibrations induced by an external source, such as a

vibration machine or impulsive driver, attached to an assembly. Northrop used

an electrically operated hammer to develop an impulsive excitation applied to

various assemblies.

2.6.1 Vibration Recording and Analysis

The equipment used to record and process vibration data is illustrated in

Figure 2-8. The M151 vehicle was equipped with accelerometers mounted on the

engine-transmission housing, rear differential, and front differential. Rota-

tion sensors were mounted to detect rear drive shaft rotation, engine rotation

and to detect each of the four wheel rotations. Signal conditioning ampli-

fiers and filters were ustd to condition the accelerometer signals for mag-

netic tape recording. The output of t ,e rotation sensjrs was processed to

sharpen the pulse shape and to condition for magnetic tape recording.

2-27

S

o^^:rU

"1 I r

VIBRATION ROTATION

COHTRINTAWRAC.I -

PtOTS

POWER SPECTRAl _ DENSITY PIOTS

NOP ?7'j-lbS

COM PURR

i

DIGITI/fD DATA j, ,__jC)

I ON MAC 1APE

SIGNAL CONDITIONER

VIBRATION ROTATION OUT OUT

! SYNCHRONOUS DIGITIZING

RATE I . J

ROTATION

• o

NCI STA'.D-

AlONE DIGITIZER

Q (k j) — /

RECORDER

<~>

Vi if

RECORDER

O VIBRATION

/ RECORDED DATA

Figure 2-8. DATA PROCESS

A portable magnet ic tape instrument recorder was used in record the accelerorr.-

eter and rotation signals. Data was recorded while operating the vehicle under

the following conditions.

a. At various speeds and gears while jacked up and suspended op spring

blocks. Each axle was supported on a spring that would permit the

wheel to vibrate.

b. While operating the vehicle on a dynamomet. .

c. While operating the vehicle on the ro.id at various speeds .nd in

various gears.

These data were analyzed ii. the following ways.

a. In real time observing the general nature and amplitude of the vibra-

tion signal.

b. Preliminary spectral analysis using a Tektronix spectrum analyzer.

2-28

i

I 1 I I I I 1 I I I I

c. Computer processing to develop coherent average and synchronous power

spectral density plots.

The process used for the computer analysis is illustrated in Figure 2-8. The

recorded data was played back on the magnetic tape recorders. Analog data

was filtered to prevent aliasing and amplified for input to Northrop Rssearch

& Technology ("enter digitizing systems. Digitization rate was selected and

controlled by a synchronous digitizing unit. The digitizing s.-.iit used recorded

shaft rotatior pulses to generate N digitizing pulses per sha '' revolution.

These digitizing pulses were phase locked to the shaft rate. Tu« digitized

analog values were therefore coherent with various mechanical functions in the

assemblies. This digitized data was recorded on computer compatible magnetic

tape.

These magnetic tapes were then procef -ed on Northrop 370-165 IBM computer to

develop coherent average plots and power spectral density plots.

2.6.2 Impulse Response Measurements

The impulse response technique involves inducing an impulsive stress in an

assembly, measuring the resulting vibration of that assembly and measuring the

vibration induced at other driveline assemblies through connecting shafts and

structure. This technique is illustrated in Figure 2-9.

An electrically operated hammer that delivers a controlled repetitive impulse

was used to excite the transmission assembly. Accelerorneters placed on the

transmission and on the differential were used to pick up the resulting vibra-

tions. Thi_ ringing frequency f1 and amplitude A. at the transmission were

observed. Similarly, the coupled frequency f„ and amplitude A„ induced in

the differential were observed. In this case, a frequency of 6 kHz and ampli-

tude of .10g peak was induced in the transmission and resulted in a frequency

of 1.5 kHz and amplitude of ,05g in the differential. The ratio of amplitudes

is —— = 7.00 or 46 dB. Other frequencies and amplitudes can be derived by

analysis of the two waveforms. If the case is reversed, a 2.5 kHz signal is

induced in the differential and a 5 khz signal is coupled to the transmissions

that is attenuated by 25 dB.

2-29

-■■■■■.;, ".-■ .i:**;^'--'

IMPULS! Drivw

tj — 6 kHz

M LOG

COUPLING fACTOR

M 10

OR IVI SHAH

JU--

DIWSENTIAl

ACCfLLROMfTTRi

FORCING fUNCTION

A2 0 05 200-46dB

I 1

Figure 2-9. IMPULSE RESPONSE MEASUREMENT

As seen in Figure 2-10, the coupling trom transmission Lo rear differential was

depicted by an error from transmission to differential indicating a 6 kHz sig-

nal in the transmission and a 1.5 kHz signal in the differential with 46 dB

attenuator.

Nf ■ FREQUENCY NOT DLFINED

REAR FRONT

Figure 2-10. M151A2 DRIVELINE IMPULSE RESPONSES

2-30

1903

I i

I I I

I I I I I !

I 1 1

The fundamental coupling factors between major assemblies Is illustrated in

Figure 2-10.

2.6. ) Analysis of Recorded Vibrat ion

Vibration signals from accelerometers were recorded on magnetic tape and then

played back for analysis. One technique used by Northrop was spectrum anal-

ysis. The effects of using different spectral line bandwidth in the analysis

is illustrated in Figure 2-11. Note that octave band and 1/3 octave band

analyses shows only the general energy content over the spectrum. The narrow

band 4 percent filter analysis shows more detail at the lower frequencies, but

is similar to Liie wider band responses.

1 500 1000

RKQUCNCYOt)

I 1 I I I

Figure 2-11. TYPICAL ANALYSIS OF VIBRATION

The 2 Hz bandwidth filter shows that the vibration is made up of a large

number of discrete frequencies. These discrete frequency lines were identified

as belonging to specific mechanical sources as illustrated in Figure 2-12. A

smaller bandwidth analysis with higher signal-to-noise ratio would reveal

additional detail.

2-31

1 ■■■*

4

.»

0 1 10

DRIVE SHAFT ROTATION

40

Figure 2-12. SYNCHRONOUS ANALYSIS 01' VIBRATION

High resolution frequency analysis required sampling periods of one or two

seconds to provide frequency resolutions uf 1. Lo 1/2 Hz. To provide high

signal-to-noise ratios that reject road and other random vibtations, a number

of spectrums were averaged to obtain signatures of the mechanical parts. An

impractical requirement of holding the machine speed constant within a few

percent is imposed if the high resolution frequence analysis is done from a

constant time base. One alternative is » ■> analyze the vibration data refer-

enced and synchronized to a shaft rotation. J The spectral lines are now expressed i.i terms of shaft rotation. To accom-

plish thi?, the driveline vibratior data was digitized in synchronism at

various multiples of the drive r'naft or axle speed. This digitized data

was then subjected to a power spectral density (PSD) analysis and plotted as

illustrated in Figure 2-13.

The abscissa of these plots are those functions of N times the shaft rate

where N may vary from a number less than 1 to a number greater than 1.

Typically, a plot contains 256 spectral lines, each one of which is called a bin.

2-32

7?

i

I I I I I

J

!

> i i r r > r i * i i * 7 1 ft J T » r s i » i x 7 I ff S J 7 * J r T f » » * T T r i T T j J * 7 7 I 7 7 9 7 T 7

i 7 -9 i a 7 a 7 » » » > 1 ? ft J 7 ft 3 3» j :* a * > ft J » » > J * > J ft f * ft :• ft ft ft ? * ft 3 > 3 > ft » a a > * a ft ft ft ft ft 1 1 » » 1 > » X ft ft y r * i ft. > ) * > ft « > i ft a ft > x > » - r i s Til 7 » i ft ft * I » ? 7 1 ft ft ? ft

*• f 1 J ft a

> r > ft » ft » > » > ft a i > > > ft > ft > » ft » i J » > ft ft > * > » » > » a > ft ft

> ft > J > ft l > ft i > ft » a i a > ft ft ■> > a i > a ft a > z ft a a a ft ft ft a > » ft i J a » i ft a ft ft » > j > ? a > » > a » ft > a 7 a a ? a. a ft a j a » » ft > * s : a. > a. a 2 a » a ft a ft ? * j r T 7 ft ? r

r : > j »

i .■« * :* ft

•»\j^«^r--*r^OJ,(y'^'NO'**^CrO',j'\I,j'*»*-^'Sjw^'*-»-jfk-< 'N N 4 ,/ « CO' j j^ *^ r* a

' (V (" ■# If1 4 >• (T ^ O ■ ry rf\ .f ir O I ■ »*» Id <** *•■> (•*■ m r ■*# .f .ft ^ .ft ,» ^4'^^f^/^^^'J^|J^^^l^'l^^^^rl^•O■O•^«0'^•C'i,•

r

A*

s»»»>iiif»i> » i i J i -I»>>J>JII>J— -.»»— ** *« r 1 s. x * .>>>**>>>> **i#a»>». <»>1»»>J>» >* j > J * » > ► *»t*a»»»»l**»*»)*j»>»»»**»»T » * » j J * * J a i»»»2»*i*ikxii»?>»>:i»>>)»»>}-r i * » i z » i z x t

i»ixij»ai^»»»»i>i»»>*»»>*»>»»»»»*,»»l,i****

» * » a » > »t ii * * * * * y » » » ? I »I>J»>»*:»:»»>:»I»**>»*

t»>>!i9>»*>>>ri>»a?>>>>>i>f>>*>*>'*a,*v:l'

»ii**»>iii*j»i>»»*»;.»»»»*»»».>»J:*»a,a-,-lllx

»»!»>! 1 1 > 1 1 I » I 1 1 I ) I I )»>)>>'»»'» ''', '^ * "

*5»»f**i*»j»»i#iti**f?f»»-> *■''»>*»*?****''''* * 5 » • »s*«***i»i •»>>**>*»>* » j »» } J» !> 1 M M > » I ) ) t 1 I I I I ! I t I S t • I ! -JJTJi-r-JJJJJJ?: > X » * » 3 » » i J i » ' i > i*» f I t I • f r > i 7 ) i ? J n M M > ) M I i r i n ,,v,.,;';;,;;,,;;«;:i?«>«?*>*39*xxz»?izxz i*^^*i*i»»«l*»»-»l3*sSJ*i»x:,»XXJ»:.'Xl.f'»¥l»•,» i»ii**'.J'iS»;»*-J**-«-***>*y>*',?*»Sl'*X-r**

« ) 1 > i > i 5 > « ! i ' I j i ' i > ' ) ■ > » J ' 5 J ' > ) M r J > J 1 J > f

i —• 'J " *J"^Na fl <*v -f ' * #■ » ff o -* * »or *~* c* — -* -* -

■ ** • ^ <r c

Figure 2-13. TYPICAL COMPUTER PRINTOUT

2-33/2-34

.i«*<SS*; ;..-,,_-■ ;.,.'..:

,V^ iffiÄ «si :■,;;■,'-;;; l-®&&i

The exact shaft rate frequency may be (for example) In bin 16 (N*16). Bin

4 would therefore contain the magnitude of vibration that occurs at one fourth

of the shaft rate and the 80th bin would contain the magnitude of vibration

that is 5 times the shaft rate. In the computer printouts the abscissa con-

tains two sets of numbers as shown in Figure 2-1). The lower set (first

column at the bottom of the page), ranging from 1 to 256, is the bin number

and corresponds to N+l. Therefore, bin 17, in this case, corresponds to the

shaft rate and bin T2 corresponds to two times the shaft rate. The upper set

of numbers (second column at the bottom of the page) aJong the abscissa repre-

sents the relative vibration amplitude in dB.

An explanation of this type of power spectrum density plot is as follows:

T ■ Period of the sample

N * Number of clocks per sample period; 128, 256, 512 or 1024 C = Clock Rate = NT

f = Maximum frequency resolved max

= £ _ I _ CT-2 2 T " 2T (f-')l

min 1 f

K = N The bin number with values from 1 to —

Bin separation frequency = ~ T

•k - Frequency of the Kth bin = (K-l) I T

Note that bin 1 K=l TU„ r "in x K=I. The frequency is al ways equal to zero.

2-35

.'.'.;;;-;:.'..,.,.■:.,'-.-■,''■ , . ..- » i -. - ' * * « • *• s " *< -»- "«-'■■*-'■'

EXAMPLE

N is picked to be S12 clocks per period

T = 0.1 second (600 rpm)

f I . 10 Hz (appears in Bin 2) nun

max . (All , \ J_ = 25S0 Hz

2 f 0.1

= i = 10 Hz T

K = 256

.'he plot would appear as shown in rig Kifiure 2-14.

i x i 2 S 8

a -m-

XXX

8 % I

J U 1

fi s s

Figure 2-14. INTERPRETATION OF PSD AMPLITUDE AND FREQUENCIES

In Terms of Shaft Rotation

1 T

1 DT

where T is the shaft period and —— s T s

— = shaft frequency, f

2-36

max

min

= Number of docks per sample period (T)

I-JL -I, T DT I) o

s

1 . I f DT D o

s

!'he bin numbers can now be expressed In terms of f

fk - (K-l) i - (K-l) I fo

Note that this gives the ability to plot frequencies below the shaft frequency

and gives a higher resolution plot.

An example is shown in Figure 2-15 and is interpreted as follows:

Assume f = 600 rpm or 10 Hz o r

D - 8

N = 512

max

8 (f0> 31.87 3 f

min

= 318.7 Hz

fo m 10 8 ~ 8

1.25 Hz

~ f - 1.25 Hz D o

2-37

*wi'3*;s.M-.-:!'-«.*-.i'.. : -i .:«i->.-w;-fa.i*s .*i^iAAh«Jii^wu*tffe«/!vVJ:-'*"S-&-:>

a

K < 3s

H n n ir-

u. < 5

-4f- 2 £

K t < s £

J L

Figure 2-15. RELATIONSHIP OF PLOT TO SiiAF! ROTATION

2.7 COMPARISON OF ANALYTICAL AND EMPIRICAL RESULTS

Analytical analysis indicated that there would be a large number of discrete

frequencies that could be attributed to specific components within an assembly.

The majority of these frequencies were below TOO hertz. A typical PSD com-

puter plot from a differential is shown in Figure 2-16. In this case, the

M151A2 vehicle was operated in third gear at approximately 23 miles per hour.

By using analytical techniques, the various lines can be identified as belong-

ing to specific mechanical components.

Sources of lines are identified on the plot in Figure 2-16. Many of the lines

show spectral lines that are due to other assemblies such as wheels, wheel-U-

joints, drive shaft, etc. The effects of the drive -haft U-joints on the

differential gear mesh frequency is identifiable as the gear mesh frequency

minus and plus the drive shaft and U-joint frequency.

The plot illustrates the highly complex nature of the vibration and how i£ is

mac'e un of frequency components attributable to components within the subject

assembly, frequencies from other assemblies, and induced frequencies that are

frame-coupled due to torque variations.

A high-frequency plot from a differential is illustrated in Figure 2-17. Be-

cause of the broad band of frequencies covered, the frequency resolution is

2-38

\

5 o

3? u_ u. 5 $ «/> 1/1

3 t 3

r

IT

I

3

S3

8

5

Q

e

5

s

a t

2 v/l in

2

or

5 o z

Of

o

400 HZ

,#J--O*-. f '« 3 • — , -l.«.#-%-j-i »*-•«. / N »••- .( -ü — «• 0 ^ • ) ^ N i» # ( O^^AAjl^A/f^' . -* D w * '5 -• -

#^>««»»»0""',fc*

-TMT

J 2

100 HZ

FRAM£ VIBRATION 0OIS NOT CHANGE WITH VtHICU SPUO

taoHZ

I 9 l % 1

> * i >

• f • I » t

T iJ - - U ? • • ou«: i w -• D^^ -• -i -v ■« # .# * » c *•-*»- r> a o a .

*i » 1 — '„ — 4 iT e ? * > y ;

.i.„. „ _.J_Jt-.

3

DirrtRCNTIAL RLAR 3RD GEAR 25MPH

ACTUAlFREQUENCY IS APPROXIMATELY 4 (BIN NUMBER - 11

4POIE IOVY POS FILTER SET TO 800 HZ

KEY TO VlBRATIONLINE IDENTIFICATION

EXAMPIE . . . . 2!ÜIFF.GEAR.MESHt.-<CYU,\DER.RATE>

MEANS TWO TIMES THE DIHfRENTIAl GEAR MESH RATE MINUS THE ENGINE CYLINDER FIRING RATE. SEE BIN NO. 61

\

S t -r- ~", r> *• £> j-. t~ a * >*•■ j*. i |««i< • 4 * * *

«N^MNNNNf

, ■•» Jt ^ C — BOO — «v ••* * W «•-«-<* O — 'S. ■« .* r«»«.-p»rt-t-n^*^rfi~ «»^-a-w-M«*»«

Figure 2-16. PSD OF REAR DIFFERENTIAL

2-39/2-40

■i,'.'.-..».-. ~~~" -*T

I I I I

1. 1 1

or

Z g 3

5 i

13

r

or

5 o

«CO HZ 2

3

.. _ _

I.

■"■■r «-*»■»»»■

s FRAM£ VIBRATU'N

1000 HZ 6» HZ

:*.

y \ x v i » » v : » t r •

> ■ » a i. - x. > * ' X >

-—>*:* — O-i^f ■ü c £ x. T

■»^■»iii» ■»■■■, M,..*^.

""" -~^—~> — sir - ~—

r ip.

1600 HZ

DIFFERENTIAL REAR 3RD GEAR 20MPH ACTUAL FREQUENCY IS APPROXIMATELY 8 (BIN NUMBER-II

4 POLE LOW POS FILTER i a TO 2000 HZ

t • t I 1 1 1

*»>*»*>» * a i->-i-'--»»ria*

M ) i • I i > M a, »a>k**t *^.a»!ta»:»»>»aa

• *'^*»i:«»t-»Ta>i»«XX J a * - : * a » a >i-:->a>?»*r?a r -•• i * y i i » -. > i » T i j i j > 7 r i » j * i ) U ' r l > * i i t >M t : > - ^ . i M ) i L i t — . --I:..,. .- , . , . j . , : .> a » $* x f

: *»-s»a**-«»a :-»„»»>■. • a « T a » r r * r • * • - : ■> * : ■ * s' j • a i » j a !> X i »

-»>.•■.■.-,. a «» «r;rrr'«Trr/ictffi

• * - - i ". ' ► T at I■ K - -»; IT»:*.* xiKvrxxa ! ■ J i ■ * ' ■ ■• i : > v » - * ' i. » *. v * « a >- 1 * r »- r r * ■ » •-■>**■». -• i 4 >--*■•>;>■ i *'*..-. t r. y x a *■ r j- i r r !»■--<:. *. *a-*y»i »*»»*- *tr»T»*'">»'»>rarrT_-,.J.-.H«__*^

* s • ••» - * a . ' r > J • n n »i » i < n H » U :-'^-*'* J», i > v i r : ü r i it ^ I r > n n t | ( * t 1 1

- * - *»>'•»/"*■«. *»*;>*» >>..x» a. ai«».ir:.aa.J»«'rrx II ;*>»*-**i.»*> *»■ •►»■-^■'Ji»»a»yii»r»»ar»<:a,i»'cx

»■> »•--»•jar»* -»• ': f r»i < TT* wrMrici »i »u. t f r i r t , > « . > r •*>>**. * ay i*-.-..*a-*a>a»a:">aa*»aa»'Txxa-xr»xx

?-.. *'» »>■*»*#.-. ' t k > i > > > >. M i , > i M ' r ; r ic > r i i t t i i . . >« »-. . «>..••')»» j >>,»>)>»> i :»>» i »»»» i >»•>> i > i i i j «'*»•»> a ai~**"*:xx*a>»»"\-*J«ir»'*ra«»1 if ■/»«»?»*"» a- *jrj JI»J. >. 1 ' i J •>»>»»'«»» > a J a a > >. >>>ajt>>}, aA.a.aa.a>. a » * »»»»■'•«. »»»■*' ' > : * ■ * . a a > * . .4,>>i" k > > 1 ) k It I M t 4| ^ | • » > * ->•*>. •/>■#_>- i < ■ i i i ,* ; t ) ^ i i » i i r ;: > i t >■ t ^ A i t. i

> a j - - a I ■ ••: < ^ • ' ;. ' . f > . (. > i • i r * « i > £ ' < ). k t i < t > ^ ) .■?,■»■•*•:'.: *.».*i,i+.*>*ii4.:if>*»i.*i«.:?j.x*;«rji.x a >*•■-_,* ,■ *. * > - •«*•»- a i -* a -•>>•»>, a*j»--rr*ij>r».t» , » j » . . a » .» ■ : »*. . : M > U > > > » > > i > 1 » > i 1 i, M i m >. »i-JT».

. • .?•-'.. - i - : J . : :■ *. r a « > > > n < ) ;-■ >>a, -.«-. aa»j-ji.T» • a . r » • t »*»t> * : /j»y>>»,i-*i*7>aaiTiar»ji-:>-fa)'aaJa:a.a • i * ,« ->»: - • * 7 * . - ». > >/**--'.-. • . ; J i * i ■ J < T ' J ' 1 T » f * » T • »*?■- ».' ^ * r » ) u ; :• J » u > i .* i j j M > i ; ,* i m i i ;, t s. n »*»-i>. :;' '»v»: >>/■ ,>>rr>.-:*'--i>;li-^JXj: t x. a » » a

- : i . * »- i .. 4 t ■ ' *' •■» * i - ■ . : a = > ? > * : > a. r > ■<. J. * *. a a .. a i. a: ^ a ., » , a * a .■•> ■- «*. a*.*i-* * ? i » * * a* L. a a • a •-* a. i I :,. a a x *. a a. a a

X ' » T I

a a * x a. a * a X > » X -*■ a » * * r > a. i ;-. > a. X l. - A J- *■ .■ ■ >. » X * r * » * a a a » fill a a r a X a a. x X '-'■ X X 1

a a

a a

i a >. a

> > ' J a a

a. r ? a *. ■> x » > » a » v a a r > -. x T a > »f a a

v. a a a ; T a

I x x x X X

* > it a x x

J r o o - - 'ir- JJ--< OO' J » » ^ o o — a

Figure 2-17. HIGH-FREQUENCY PSD PLOT

2-41/2-<'2

-A-^..

low. All of the data from the previous Figure 2-16 is grouped in the first

15 or 20 bins of this plot. This plot illustrates the effects of frame ringing

and high frequency elements. Those areas that are due to frame ringing do not

change frequency as the speed of the vehicle varies. The amplitude varies con-

siderably as a function of speed, load, and the goodness or badness of the

part. These bands of frequencies followed Hie characteristics qualitatively predicted using analytical techniques.

By using botli analytical and empirical analyses, it was possible to identify

specific sources of vibration and to measure their amplitudes. Frequency com-

ponents that were not predicted analytically were observed empirically and

were then traced to their source analytically o.- shown to be an error in instru-

mentation. A summary of these features is shown in Table 2-4.

As a part of this comparison analysis, Northrop concluded that discrete fre-

quency techniques were useful to identify specific parts. Not only could

wheels, drive shafts, U-joints, etc., be identified, but gears, bearing races and balls could be identified.

For this program, the discrete frequency technique was useful for identifying

the wheel, wheel U-joint, drive shaft and drive shaft U-jolnt problems, but

was not practical for identifying transmission and differential assemblies.

Each of these assemblies generated between 50 and several hundred frequencies

which would require individual measurement and comparison to specific limits.

The memory and time required to do these measurements and comparisons was not compatible with a low-cost portable system.

The ratio of frequencies in selected low and high bands did, however, prove

to be good indicators that something was wrong in an assembly as predicted analytically and identified empirically.

2'8 SELECTI™ 0F TEST TECHNIQ„ES

Any drlveli„e a„al„er t av

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"UK»

DATA ACQUISITION AND FEATURE EXTR ACTION

MATURE ANAtYSIS

VIBRATION SENSOR

ROTATION

SENSOR

TEA TÜRE EXTRACTION

>!♦

VEHICLE OPERATIONAL CONDITION

ANALYZE* AND DISPLAY

MATURE ANALYSIS

EXTRACT ION Of CONSTANTS COUPLING

»ACTORS AND NORMALIZING

IIMITS ANALYSIS AND ORDERING

Of FAULTS

FAULT

DISPLAY

Figure 2-18. DRIVEUNE ANALYZER FEATURE EXTRACTION AND ANALYSIS PROCESSES

involves the instrumentation needed to convert mechanical responses such as

vibration and shaft rotation into electrical signals. Feature extraction in-

volves the processing of these signals in any one of a variety of ways to

identify and measure specific characteristics. Typical feature extraction

techniques include spectrum analysis, peak detection bandpass analysis, cor-

relation techniques, etc. In any case, the output of the feature extractor is

a series of voltages or numbers representing the magnitude of specific features.

Typically, this may be the amplitude of a specific frequency or the energy

within a specific band of frequencies. Others may be the rotation speed of a

shaft or the phase relationship of two shafts or frequencies.

The outputs of the feature extractor are used for two purposes:

a. To provide inputs to the vehicle operation display. These, are used

to indicate to the vehicle operator whether or not he is operating

the vehicle within the require 1 limits.

b. To provide inputs to the feature analysis portion of the system.

2-46

..-.,.-,*.,.„ ,,■.-,„■.,,

Feature analysis consists of performing a set of specific operations on one or

a collection of basic features to convert them into one voltage or number that

is an indication of degree of fault. Typical operations include offset and

scaling, normalizing, applying cross-coupling factors, combining several

measurements, comparing to test limits and fault ordering. Also included as

a part of this function are the test results displays.

Some of the initial considerations in selecting test techniques were:

a. The driveline faults could be grouped into two categories.

1. Faults related to a specific part or type of part rather than an

assembly that contained a large number of parts. Specific part

faults included the following:

Wheel imbalance or bent

Wheel axle U-joints

Bent axles

Drive shaft imbalance

Drive shaft U-joints

Drive shaft misalignment

Clutch slippage

Faults related to complex assemblies that were made up of a num-

ber of moving parts, any one of which could be faulty. The

requirement in this category was to identify the assembly with

no requirement to identify the specific part causing the excessive

vibration. The assemblies in this category were:

• Differentials

• Transmissions

• Engine

2-47

k^jJAUiiUui--. :- '■,*■>■■ ■ "-..-■-- - __^_ ^ , ■--.*.-"' 'v^J^ÄVJe^-

Analytical analysis and empirical data indicated the following:

a. Discrete parts faults such as wheel imbalance and U-joints generate

frequencies that aro functions of the shaft rotation and whose ampli-

tude is a function of speed, load, and degree of fault. These parts

when faulty also generate higher frequencies and excite the trans-

mission and differential into generating additional frequencies.

In general, faults due to imbalance and bent shafts generate

sinusoidal frequencies that are at the shaft rate. U-joints

generate frequencies that are at twice the shaft rate and have a

tendency to be richer In harmonic content.

One major factor to consider is that all four wheels generate very

close to the same frequency since the diameter of the wheels are

nearly the same. A similar condition exists with the front and rear

drive shafts.

A rough running engine such as skip, missfire, etc., has a tendency

to generate frequencies at the engine rate and twice the engine rate.

Knocks generate frequencies at the engine rate, but are characterized

by generating a sin x over x envelope for higher harmonics. They

also set up ringing conditions in various frame members as well as

causing the transmission and differential to increase the amplitude

of the gear mesh frequencies, etc.

b. The transmission and differential will potentially generate up to

several hundred discrete frequencies related to gear meshes, bearings,

and shafts within the assembly. In general, these frequencies or

their near harmonics are higher than those due to wheels and drive

shafts. Faulty parts within these assemblies also have a tendency to

generate a large number of high amplitude harmonics. Faults in the

transmission and differential may be categorized as an increase of

mid-frequencies with a larger amplitude increase of the higher

frequencies. Gear and bearing faults also have a tendency to excite

the higher modes of frame ringing.

I 1 I I I

2-48

2.8.1 Wheels, 11-Joints and J)rive_ Shafts

The wheels, U-jolnts, and drive shafts all generate single frequencies that are

in synchronization with the shaft rates and whose amplitudes are proportional

to the degree of fault. This indicates a test technique that is very narrow

band to eliminate potentially interfering frequencies, and is phase locked to

the shaft rates. Since cross-coupling from other components are negligible at

the phase-locked frequencies, normalizing limit setting and fault ordering is

all that is required. For these applications, Northrop considered synchronous

integration or discrete frequencv feature extraction technique as being the

most practical approach to these problems. The technique uses a rotation

sensor to generate pulses in synchronization with the rotating member and then

phase locks the analyzer to either the fundamental or second harmonic of the

rotating shaft frequency. The feature to be extracted is the amplitude of the

frequency that is phase locked to the shaft of interest.

Since some of the rotating parts of the vehicle may rotate at very nearly the

same frequencies, some means must be used to introduce a change in rotation

rate or change in phase. To apply synchronous integration techniques to the

detection and measurement of wheel, axle, and some differential faults, it is

necessary to develop different angular rates for left and right components.

This can be thought of as developing different frequencies or ensuring that

there is 2 or more phase angle differences between wheels.

The knowledge of wheel rate differences as a function of vehicle path is

necessary to the design of diagnostic equipment and for the analysis of vibra-

tion data. Consider the following ; "oblem.

2-49

p

'p 'A'p

s

S ♦ AS

RADIUS OF INSIDE WHEEL PATH

RADIUS OF OUTSIDE WHEEL PATH

OISTANCE "RAVELED BY INSIDE WHEEL

DISTANCE TRAVELED BY OUTSIDE WHEEL

VEHICLE PATH

Op • ANGLE THROUGH WHICH VEHICLE TURNS

'„ - RADIUS OF WHEEL

u>„ - ANGLE THROUGH WHICH WHFEL TURNS

I?or the inside wheel t! ie angular motion is w = 1

wi r

F°r the °UtSlde wh«l the angular motion i

The difference in angular

w

WO r w

»tlon. of inside dnd outslde whteis

w^ WO wi = s +AS • s 2-^5 _ AS

«- , +AS . (% +Arp)6n

AS

s (■

P P

5 = e p

Ar P

_ G Ar —P-

1 P r

2-50

I 1

1 I I 1 1 I

"w •

Note that the phase differences between inside ind outside wheels is a function

of vehicle path angle and is independent of radius.

^w ') 1.467

P

J^r P

T 52 1 r = 15 1

For the Ml5.1

J.8.1.1 Typical > l.tues - If tiie vehicle is driven on a circular path of

300-foot radius at a speed of 10 miles per hour, the angular rate about the

path is.

10 mi/hr (5280 A/ml) . n._ „ ,, 6 ■ -,,vnn /,- v ,:mf = 0.049 Rad/sec p (3600 sec/hr) 300A

The difference in wheel frequencies is:

= 0 3.467 = (0.049X3.467) w p

w = 0.18 Rad/sec

f - v - 0.0272 Hz w 2

The average wheel rate = f = 1.77 Hz at 10 mph.

An imbalance vibration frequency would be:

Inside wheel « 1.77 =—^- = 1.756 Hz

Outside wheel = 1.77 +°'0.2.7 = 1.734 Hz.

The imbalance frequencies are sensed at the differential and are made up of

both inside wheel and outside wheel imbalances. The sensing device must mea-

sure the amplitude of frequencies at 1.756 Hz and 1.784 Hz to discriminate be-

tween right and left wheels.

2-51

_"2£^M

.".8.1.2 Kstlmates of Analysts Requirements - Some preliminary estimates of

analysis requirements can he developed. Consider the NCL PSD analysis technique:

to differentiate between right anil left wheels, the two frequencies should be

separated h\ .;t least one bin; that is, the two frequencies cover three bins. 0 0 '8K

The bin width is then ■-—~— or «0.01 Hz the sample period (T) should then be 1

~—. = 100 seconds.

If we use r)12 samples, there will be 25b bins giving the highest frequency in

the plot at 2.55 hertz. The inside wheel component would be in bin 177 and the

outside wheel component in bin 179. To analyze the r-joint frequencies at

3.512 and 3.568 hertz, a separate run would have to be made. Synchronization

must be held to about 1.5 percent over the digitizing period. The distance

around the circle the vehicle must be driven for one sample is 100 seconds x

.18 rad/sec, or 18 rad = 5 tines around the circular track.

This approach will effectively resolve right and left wheel faults, etc. It

is impractical to expect circular or oval tracks at most Army installations,

and the approach would require some modification of path requirements. An

approximate right angle turn will introduce a wheel phase difference of approx-

imately 300°. If the vehicle was driven along several legs of a block square

(or rectangular area) and a phase-lock analysis is conducted for each wheel

along each leg and an average for sp"°ral legs is taken, the interference from

other wheels would average out, leaving cnly the component related to the

wheel of interest.

The future extraction approach selected for wheels is a phase-locked synchro-

nous-integration analysis that is phase averaged for four different right wheel

to left wheel phase shifts equal to or greater than 90°.

2.8.2 Differential, Transmission and Engine

The analysis of the vibrations generated by faulty components in the trans-

mission showed the following:

a. Each gear generated a fundamental frequency at its tooth rate and

each bearing generated frequencies corresponding to inner-race,

r. 2-52

5 •wr

outer-race, hall spin rates, and hall pre« ision rate. bach shaft

generated frequencies .it thus.- rates.

h. All of the above gear and bearing frequencies have a tendency to be

rich in harmonic content.

c. Cross-coupling within an assembly and Iron assembly to assembly modu-

lates the fundamental gear and bearing frequencies generating many

sidebands about each.

d. The amplitude of the fundamentals and their harmonics is proporticnil

to load. Faults, however, increase the amplitude of the harmonics

much more than they do the fundamental.

e. The higher frequency modes of the housings and frames are excited

to higher amplitudes by faulty gears and bearings.

f. Bent shafts have a tendency to increase the amplitude ol the gear

mesh frequencies.

In summary, vibration energy in the band from 20 to 400 hertz is proportional

to the amount of power being transferred. in the higher frequency bands,

energy is proportional to power transfer but increases much more rapidly with

part failure.

Selection of test techniques that utilized individual frequency 01 each compon-

ent would result in a large list of synchronous frequencies and amplitudes for

eacli part within the transmission and differential. In addition, equations

for the cross-coupling of each of the frequencies to other parts would be

involved. This approach would work and appears desirable for production test-

ing and engineering evolution of new designs. The approach is impractical for

field maintenance applications for the following reasons.

a. The identification of Individual gears and bearings would be confus-

ing to the field maintenance mechanic. His only interest is the

complete assembly.

2-5 J

■ <4p~

b. Memory required for storing constants and cross-coupling factors for

components and the related calculations is impractical for met field

r.ppl icat ions.

c. The number of measurements required and the related caJculation.s

Rre.it lv increases the test time.

d. Experimental dita requirements for various conponent failures is much

more extensivt than would be permitted by this program.

When there is only the requirement to identify the assembly as being bad with-

out the need to identify components within the assembly, the bandpass ratio

technique becomes more practical. This approach takes advantage of the fact

that the high frequency vibrations increase more rapidly than the lower fre-

quencies as components fail within the assembly. This approach was selected

for the engine, transmission, and differential driveline assembly. It has

the following advantages.

a. For each assembly, only two measurements are required: one energy

in a low-pass band and two energies in a high-pass band.

b. The calculation involves taking the ratio of the high-band energy

to the low-band energy which eliminates the major effects of power

transfer.

c. Selection of appropriate bandpasses potentially eliminates or greatly

reduces the effects of cross-coupling between engine and transmission

and between engine-transmission assembly and the differential

assemblies.

d. Since accelerometers will be mounted on both differentials, it would

be practical to separate front and rear differential faults by magni-

tude comparison. Experimental data indicated that the coupling be-

tween front and rear differentials was comparatively low.

2-5/4

:.:"!Wipr ■... ,"V3»,-W«*i-*---

I I I I 1 I

1 [ i I I I I I

2.8.3 Clutch

In a vehicle, a defective clutch slips under conditions of high vehicle accel-

eration or heavy load, and the amount of slip was found to be several revolu-

tions. For this application, the vehicle will be assumed to be unloaded and

that clutch slippage is induced by high acceleration in high gear. The tech-

nique selected counts the revolutions or the engine, effectively divides it by

the transmission gear reduction, and compares this to the drive shaft revolu-

tions. Differences in the two counts indicate the amount of clutch slippage

when measured over a specified time and under specified operating conditions.

2.8.4 Selected Test Techniques

In summary the selected test techniques were:

a. Discrete synchronous frequency analysis for wheels, axles, U-joints,

and drive shafts.

b. Bandpass ratio techniques for differentia!, transmission, and engine.

c. Engine shaft rate versus drive shaft under acceletation conditions

for slipping clutch.

2-55

sa«w-ife^w^ÄS^KA^^^

PRECBDUO PAOB DUNK-NOT tl "f

SKCTION i

IMPLEMENTATION OF THE DRIVELINE ANALYZER I)I-SK;N

:f'.

This suction describes the implementar ion ol the performance requirement:- into r.!u

design of the driveline analyser hardware rind the rational,1 employed in resolving critical development decisions.

J.1 OVERALL CONCEPT

The performance requirements for the driveline analyzer have established that test set must:

Be a stand-al

to he tested one portable unit that is easily attachable to the v,

Us e power from the vehicle battery

• Be automatic in its operation

• Be capable of displaying the results to indica

of the vehicle. te good or bad condition.1-

I I 1 I I

Figure 3-1 depicts the resultant block diagram for the driveline analyzer which

I is an integrated series of tests which will provide a tool for automatically

I I I

required to perform the data gatherin g portions of the tests.

diagnosing the vibrati on source in the vehicle as it is driven en the road.

-fe<w;.-N*>^O^.^

3-1

',i- ^ir^afcnÄ- ^■^■&^&i^i-s:v&v'--M^K!-l.\ vwy^iji&^Vik

^^^^m^%%m^^^^^^^sm^^u^-,, %&$

TfcST RESULTS OISPIAY

AND CONTROL

VEHICLE OPERATIONAL

OISPLAV

ENGINEERING OlSltAV

Figur*. 3-1. Mil VELINE ANALYZER BLOCK DIAGRAM

This configuration will detect abnormal vibrations that indicate faults in the

driveline subassemblies listed in Table 3-1.

Table 3-1. DRIVELINE SUBASSEMBLY FAULTS

3-2

.. ,

Subas. jmbly

Clutch

Ft ilt Mode.

Slippage

X

Imbalance Misalignment Excess

Vibration

Drive Shaft Drive Shaft U-Joinjs

X X Wheel Assembly

X •fc

Wheel U-Joints Axle X Engine X

Transmission X Differential X

X

i I I I I I 1 1

,2 CENTRAL PROCESSOR REQUIREMENTS

'Hie large number of data points •, ,

—.. -^ JUZ'Z :::::::: - " —• - the ot

Preliminary analysis of the data showed that between 8- ;ind '6-bit accuracy was

required for most data. The analysis of wheel and axle data would result in summa-

tions that exceeded 25 bits. This large number of hies was required for the long

time period? of synchronous integration in the presence of large noise-to-signal

ratios. To conduct the analysis in real time, thus eliminating the require.', nt for

storing large quantities of vibration data, it would be necessary for the processor to add in approximately 7 microseconds.

Analysis of control and processing requirements indicated the following:

a. Between 40 and 50 measurement;: rau.«f bt ::.«<!"'.

b. A number of measi

LJ minutes. dements must be made and stored for periods up t P to 10 or

c Accuracies of requirements for the measurements

better than 1 percent. were typically equal to or

d. To offset, scale-, normalize, and compensate for rross-coupling and fault

order, there was a retirement for approximately 400 additions and sub-

tractions, multiplications, and divisions. One hundred constants were used in calculations.

3-3

-vr

e. There were approximately 100 control commands to signal conditioning and

display functions.

f. There were 40 numerical numbers involving spc-ed, gear, and other opera-

tional conditions that must be displayed to i:h*» operator.

g. There are approximately 80 pieces of variable data that must be stored

and used during one complete set of tests.

It. Approximately 1200 words of program and constants, and 100 words of

read-write memory for data and test variables would be required.

To satisfy these requirements, Northrop considered a number of commercially available

computers. Analysis, as indicated in Table 3-2, showed that most of these computers

were not suitable for portable application and tl at their power was much higher than

could be supported by vehicle power.

A CMOS computer being designed by Northrop was also considered. A comparison of

power consumption versus performance is shown in Figure 3-2. In this comparison,

Relative Performance is taken as one over required instructions times execution

time, \ftien required, Instructions is the number of instructions required to

perform a stanaard sequence of operations, and the Time is the time required to

perform a standard sequence.

3.2.1 Central Processor Implementation

Selection of a specially designed CMOS computer was made and was based on the

following:

a. The low power requirements of the CMOS system. Less than 1 ampere of

vehicle power required. This la up to 100 times less than the power

required by commercially available models.

b. High noise immunity of CMOS components to the vehicle ignition environment.

The CMOS approach has five times the noise immunity as compared to other

approaches.

1 I

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MCS4

RELATIVE PERFORMANCE (REQUIRED INSTRUCTIONS) (TIME)

Figure 3-2. POWER/PERFORMANCE COMPARISON OF VARIOUS MINICOMPUTERS

c. Compatible with the low cost read mostly memory devices.

d. CMOS devices are not damaged by power shorts, etc., do not require logic

ground planes and low switching transient generation that would interfere

with sensitive analog circuits.

e. Optimum instruction site. The ability to use micro-instructions to develop

instructions specially oriented to driveline testing greatly reduced the

number of instructions required.

f. A large number of device interrupts and special device commands could be

provided for vehicle operational monitoring and control of: sensor devices.

A functional block diagram of the Northrop designed CMOS processor is shown in

Figure 3-3.

3-6

I I I !

I !

1 i 1 1 I I l l

Figure 3-3. NORTHROP CMOS PROCESS

ANALOG INPUTS

OR

EXTERNAL EVENTS

3300

3-7

:--v^h^.j.^:a;,---:.,;,-.L,\: t_,-: *~-&SU,l-

i. 1 VIIHICLK OPERATIONAL DISPLAY REQUIREMENTS

There are a largo number of vehicle operational modes during a complete series of

tests on the Mlr>l vehicle. These operational modes involve operating the vehicle

in a specified gear at approximately a specified speed along a prescribed path.

Because tbese tests are conducted on the road, traffic and other considerations will

cause interruptions in the test sequence. In some cases, a test mode will have to

be repeated because it was impossible to hold the vehicle operational cond'tions for

the specified time. Provis ons must, be made to provide the vehicle operator with

indicators that instruct him concerning vehicle gear, engine rpm, vehicle speed, and

the identification of the test being conducted. The vehicle operator should also be

provided with indications of whether or not he is meeting the required operational

conditions and if it is necessary to repeat a test sequence. The types of informa-

tion that must be presented to the vehicle operator are:

• Engine rpm for engine and clutch tests

• Transmission gear for specific test modes

• Speed in mph for clutch, transmission, differential, and wheel tests,

The monitored conditions display requirements are:

Engine rpm

Speed in mph

Waiting for conditions to be met

Invalid test

Test complete.

3.3.1 Operator Display Implementation

The remote display panel on the operator display assembly provides the vehicle

operator with the indications as illustrated in Figure 3-4. This assembly is

packaged in a box 6 by 7-1/2 by 2 inches and attaches to the metal panel just below

the windshield.

I I f

3-8

1 I I I I I 1

REMOTE DISPLAY CONSOLE

I

RPM H O REQUIRED .

SPEED REQUIRED

* »

- (Z

RPM Ä i» GEAR $> VCTUAL j REQUIRED

, 0WAITING # CLUTCH

• 4fc TEST IN A n.r_ Ä W PROGRESS h rr,

mm • INVALID ÄTRANA TEST X

SPEED f> ACTUAL ■F

Ä

# ENGINE •WHEELS

Figure i-4. KEMOTK DISl'I.Ai n'N'Snu PANFL

i.J.2 Description of th_e Misjilay.s

'Hie operator display assembly has the following operate! c-r iented display functions.

WAITING Initially illuminates when analyser has completed a power-up sequence,

successfully completed a processor seM'-test, has initiated the program,

and is waiting for operator action.

I I I 1

During a test mode the lamp will illuminate whenever an operator action

is required to change gears in tin transmission, rpm of the engine,

speed of the vehicle, or the direction of the vehicle to cause wheel

phase shift.

3-9

TKST IN PROGRESS

Illuminates whenever the vehicle is heins operated in the appropriate

test mode and the processor is conducting data acquisition or data

analvs is.

INVALID Illuminates to inform the operator that the required test conditions

were not met during the previous test program and that the test should

he repeated.

ENGINE, CLUTCH, TRANS, DI FF, WHEELS

These five individual lamps will illuminate as the diagnostic test

progresses through the individual test modes to enable the operator

to determine that test conditions are being successfully met.

RPM REQUIRED

The numbers (times 100) designate the revolutions per minute that

the vehicle operator should operate the vehicle engine.

RPM ACTUAL

The numbers (times 100) display the actual rnm at which the engine is

being operated.

SPEED The numbers designate thp speed in mph that the vehicle operator should REQUIRED . , fcl . . ,

drive the vehicle.

SPEED ACTUAL

The numbers designate the speed in mph at which the vehicle is actually

moving.

GEAR REQUIRED

The number designates the gear position in which the transmission

should be placed:

1 ■ 1st gear 3 ■ 3rd gear

2 = 2nd gear 4 = 4th gear

5 = reverse gear

0 = neutral

3.4 TEST RESULT DISPLAY REQUIREMENTS

There are a number of assemblies that must be identified with an indication of the

degree of fault indicated. A method to indicate the degree of fault is to use

numerically normalized values from 0 to 9. During engineering evaluation it would

3-10

■w

I i be highly desirable to display a higher resolution number, for example 00 to (*9

The faults which must be identified include the following:

i I I I

a. I'ngine

b. Clutch

c. Transmission

d. Rear Drive Shaft Imbalance

e. Hear Drive Shaft U-joints

f. Rear Differential

g. Right Rear Axle U-joints

h. Right Rear Axle Bent

i. Right Rear l/heel Imbalance

j. Left Rear Axle ü-joints

k. Left Rear Axle Bent

1. Left Rear Wheel Imbalance

m. Front Drive Shaft Imbalance

n. Front Drive Shaft l-joints

o. Front Right Axle U-joints

p. Front Right Axle Bent

q. Vront Right Wheel Imbalance

r. Front Left Axle ll-jcints

s. Front Left Axle Bent

t. Front Left Wheel Bent.

Typical display arrangements for these faults might be as follows

T~~ ■

A | U F 7

♦ Degree of fault

-Left or Right

] Measured value or

normalized value for

engineering use only

—Front or Rear

■Assembly Axle U-joint, transmission, etc.

In this case, a technique must be provided for presenting the faults in descending

order of the des-ree of fault. Provisions for manually sequencing from one fault to

the next must be. provided.

3-11

^;.■-:,.>■,-:_ v-y.'«f*:-H-Wt.,*JV,>^W-'-..^.:.- JXiQ.*

w

'.-».I Test_ JiesulJ: JUs£lay Implementation

The display selected for the hardware implementation is a l^-character alphanumeric

am! is contained in the logic and control assembly. This display is used tor iden-

tification of the faulty driveline components. 1'pon completion of a valid test

program, the front panel FAULT DISPLAY will illuminate <.• ith a TEST COMPLETE message.

To observe the test results, the operator actuates the FAULT DISPLAY INDEX pushbutton

also located on the logic and control assembly.

The faultv assemblies will be identified in the hierarchy oj faults. The FAIL!

DISPLAY, will first display a message identifying the most significant fault, together

with a normalized degree of fault and the order of faults, as multiple faults can

occur through the cross-coupling of vibration. The most likely i. 'use of vibration

fault will be the first fault displayed.

3. A. 2 Description jof_ the Test Kesult Messages

The format utilized for these messages is as follows:

7 8 9 10 11 12 13 14 15 16

Fault Identifier

Degree of Fau 11

Rank Order of Fault

The abbreviations utilized for the fault identifier messages are defined below.

Test Name

REAR RIGHT WHEEL

».EAR LEFT WHEEL

FRONT RIGHT WHEEL

FRONT LEFT WHEEL

REAR RIGHT AXLE

REAR Li..'7 \XLE

FRONT RIGHT AXLE

FRONT LEFT AXLE

REAR SHAH' FUND

FRONT SHAFT FUND

PJ-?play Code

WHB-RR

WHB-RL

WHB-FR

WHB-FL

WHA-RR

WHA-RL

WHA-FR

WHA-FI.

R-DS-F

F-OS-F

3-12

I I

I I I I I 1 I I I I I I I

I I I 1 1 *

1

1 1

1 1 t 1 I I I

Test Name Display Code

REAR SHAH' 2ND R-DS-2

FRONT SHAH 2ND F-DS-2

REAR HIFF HI RIUF-H

REAR IUFF RATIO RD1F-R

FRONT IUFF 111 FD1F-H

FRONT 1)1 I F RATIO FDIF-R

IRANS GEAR 1 Hl TR-l-H

TRANS ('.EAR 1 RATIO TR-l-R

TRANS GKAR 2 HI TR-2-H

TRANS GEAR 2 RATIO TR-2-R

TRANS GEAR 3 HI TR-3-H

TRANS GEAR 3 RATIO TR-3-R

TRANS GEAR 4 Hl TR-4-H

TRANS GEAR 4 RATIO TR-4-R

ENIJIIV. 600 Jii EGOO-T.

ENGINE 600 RATH) E600-R

ENGINE 1000 HI E 1K-H

ENGINE 1000 RATIO E 1K.-R

ENGINE 2000 HI E 2K-H

ENGINE 2000 RATIO K 2K-R

CLUTCH SLIP CLUTCH

Following are definitions of trims used in Test Name:

FUND - Tlii' fundamental frequency oj rotation tor the component ol interest

2ND - The second harmonic ol the rotation frequency for the component oi

interest

HI - The measurement value of the high frequency bandpass

RATIO - The ratio of the high frequency bandpass to the low frequency bandpass

values.

J.5 SENSOR AND SIGNAL CONDITIONING REQUIREMENTS

The requirement of applying the driveline analyzer to the vehicle in less than the

10 minutes dictates the use of a small number of easily connected sensor assemblies.

This requirement excludes the ability to instrument areas of the driveline subassem-

blies, which would require excessive time to install or modification of the vehicle.

3-13

From the test technique selection, the rotation sensor requirements become six:

• Four for the wheel rotation sensing,

• One for the engine rpm sensing

• One for drive shaft rotation sensing

The rotation sensors will require phase-locked-loop logic. Multiplexers are adaed

to allow for time sharing of the hardware.

Three accelerometers will be required. This was determined empirically and fron

the requirements imposed by the fault separation test technique selected for the

front and rear differentials.

Fach of the ac'» aromerers used to sense vibration must have the following signal

conditioning provisions:

a. Programmable preamplifier with 0 to 42 dB dynamic programmable range and a

bandpass of 0.1 Hz to 10 kHz.

b. Programmable filter wich four-pole high pass and four-pole low pass.

c. Progiammable post amplifier with 0 to 42 dB programmable gain and a band-

pass of 0.1 to 10 kHz.

d. An analog-to-digital converter programmable to select any of three

accelerometer channels and with a conversion start control.

3.6 DRIVEL1NE ANALYZER SPECIFICATIONS

CJMMPONENTS One Logic and Control Assembly (Part No. 307225)

One Operator Display Assembly (Part No. 307226)

Three Sensor Assemblies (Part Nos. 307227, 307228, 307229)

One Power Cable (Part No. 307231)

MEASUREMENT Four counter-t imer cnanneib v. 'J-Lll UlUXLJ-^J-*'"- — r

CAPABILITY

1 Hz 10 kHz PL1SF'.5) CTK3r,C

10 Hz 100 kHz PL2SB(6) CTR4TC

100 Hz

1 kHz

1 MHz

PLiSA(l)

CTRJ rc

CTRT' r

PLLl

PLL2

I 1 1 !

3-14

-sr

Two amplifier-filter channels with multiplexed controls of:

Input Select: Ground, Accel No. 1, Accel No. 2

Input Gain: Unity, 6 dB, 12 dB, 18 dB, 24 dB, 30 dB, 36 dB, 42 HR

High-Pass Filter: Bypass, 10 Hz, 30 Hz, 90 Hz, 700 Hz, 2200 Hz,

5 kHz

Output Gain: Unity, 6 dB, 12 dB, 18 dB, 24 dB, 30 dB, 36 dB, 42 dB

One A/D converter with multiplexed controls of:

Input Select: Chan 1, Chan 2, Chan 1 Avg, Chan 2 Avg, DC Test,

Ground

PROCESSOR CAPABILITY

One 16-bit data bus (processor and I/O functions)

One 16-bit address bus (address memory and I/O devices)

Eight 16-bit general purpose registers (data opera-.ds, accumula- tors, or address index registers)

One 16-bit arithmetic logic unit (ALU)

Four 16-bit memory address registers (memory address pointers)

256 words alterable read-only-memory (microinstructions)

1536 words alterable read-only-memory (macroinstructions)

1028 words random access memory (read-write)

READOUT Operator Display (Remote Unit)

I

WAITING

TEST IN PROGRESS

INVALID TEST

ENGINE

TRANS

DIFF

WHEELS

Waiting for operator action

Performing data acquisition or analysis

Instruction to operator

Programmed for test related to engine

Progi-anuned for test related to transmission

Programmed for test related to differential

Programmed for test related to wheels, wheel axles, propeller shaft, and U-joints

3-15

4V ;ti*.ja'"-- <.».*.«»».»■*•*>*"•■■ ■■•■ *w»«tj«'*t«»*'i*W*

CONTROLS

POWER

REQUIREMENTS

RPM REQUIRED Designates speed of engine required

RPM ACTUAL Dicplays actual speed of engine

SPEED Designates speed of vehicle required REQUIRED

SPEED ACTUAL Displays actual speed of vehicle

GEAR Designates transmission position required REQUIRED

Front Panel (Logic and Control Assembly)

Alphanumeric 16-character diagnosis display

Engineering Control Panel (beneath front panel)

Sequence states

Address bus

Data bus •*

Front Panel (Logic and Control Assembly)

POWER On/off control for 24-volt source power

RESET Program reset to start of selected data acquisition

FAULT DISPLAY Allows for stepping through fault display messages INDEX

RUN Initiates the test j

Engineering Control Panel (beneath front panel) I

Processor Control Switches (5) 1

Register Selection Switches (7)

Address/Data Input Switches (16) "f

Voltage: 25.2 f3 volts DC ^

Polarity: Negative terminal grounded to frame (Reverse polarity |

is protected)

Current: 7-1/2 amperes maximum, 3 amperes nominal 1

I I

MECHANICAL

I I I I I I 1 I I I 1 I I I K I I

DIAGNOSTIC PROGRAMS

Size: Logic and Control Assembly - 12 x 14 x 17 inches

Operator display Assembly - 6 x 7-1/2 x 2 inches

Weight: Logic and Control Assembly - 40 pounds

Operator Display Assembly - 2 pounds

Sensor Assemblies (Total) - 11 pounds

Test Select and Control

Wheel Data Acquisition and Analysis

Propeller Shaft Data Acquisition and Analysis

Differential Data Acquisition and Analysis

Transmission Data Acquisition and Analysis

Clutch Control Data Acquisition and Analysis

Engine Data Acquisition and Analysis

Test Results Analysis and Display

Engineering Data Display Control

Analyzer Self-Check

3.7 HARDWARE PICTORIALS

The driveline analyzer chassis installed in the M151 vehicle is shown in Figure 3-5,

and the vehicle operator's remote display is shown in Figure 3-6. The rear differ-

ential sensor assembly, transmission sensor assembly, and the front differential

sensor assembly are shown in Figures 3-7, 3-8, and 3-9, respectively.

A detailed description of the installation and use and interpretation of the drive-

line analyzer is given in the Instruction Manual M151 Driveline Analyzer Feasibility

Model.

3-17

Figure 3-5. DRIVELINE ANALYZER CHASSIS IN PLACE

I

Figure 3-6. REMOTE DISPLAY CONSOLE IN PLACE

i

\

I I

3-18 I

Figure 3-7. FRONT DIFFERENTIAL SENSOR ASSEMBLY INSTALLED

I Figure 3-8. REAR DIFFERENTIAL SENSOR ASSEMBLY INSTALLED

I 3-19

Figure 3-9. TRANSMISSION SENSOR ASSEMBLY INSTALLED

I

3-20

i

I I I I I

I I E I !

I t 1

T

I 1 I I I I

SECTION 4

TEST AND EVALUATION

(Summary of Tests)

The test and evaluation portion of the drive]ine analyser program involved the

following phases.

• Bench Test which included the following:

a. Computer program sequence checkout.

b. Use of simulated transducer signals as inputs to the analyzer to

determine proper measurement of specified signal features.

c. Use of magnetic tape recordings of transducer signals from on-the-road

test to show compatibility and reproducibility of readings using actual

vehicle data.

• Vehicle Compatibility Test which included:

a. Attachment of sensors to the vehicle and installation of the driveline

analyzer and display in the M151A2 1/4-ton utility truck.

b. Operation of the driveline analyzer from vehicle electrical power

while operating the vehicle on the road.

• Preliminary Road Test to:

a. Demonstrate the ability of the test set to measure vehicle operational

parameters and display them to the vehicle operator with desired modes

of operation during the various test sequences.

b. Obtain preliminary magnitudes of extracted features for a good vehicle.

4-1

.-äf*'-34ft'?attr4tftf' «W/ÖftT «SOW* -: s«»*f» *S «B»$ "'■

c. Obtain preliminary magnitudes of extracted features for certain

inserted faults.

After completion of these tests the driveline analyzer was shipped to TACOM.

4.1 BENCH TESTS OF THE DRIVELINE ANALYZER

The bench test portion of the program involved operating the driveline analyzer in

the laboratory to determine if the driveline analyzer performed to the design goals.

The bench test included the following phase=>

a. Computer Program Operation - All feature extraction, data processing,

test faults display and the vehicle operational display and control program-

were checked, using simulated digital data. The test, programs were modified

to use special digital words as substitutes for data inputs from the trans-

ducers and signal conditioning equipment. Each test was initiated to

determine if the program was extracting the desired feature, analyzing

data, and displaying the results properly. The advantage of this approach

was that the simulated input data could be controlled precisely so that the

accuracy of the feature's extraction and analyses could be determined.

These programs included the following:

• Driveline analyser computer program process flow and control routines

• Tnput device control programs for signal conditioning, analog switching,

counter control, analcg-to-digital converter, binary-to-BCD conversion

and phase lock loop controls

• Vehicle control monitor programs; these programs included the function

of display of desired vehicle operational conditions, monitorirg of

vehicle speed, gear and engine rpm

• Driveline analyzer bandpass ratio tests; this included input device

setup, speed and gear control setup, high-pass and low-pass band

measurements and ratio calculations

• Wheel/axle data acquisition program

";: 4-2 I

w

I I I I I 1 1

1 I I 1 1 I I \

Wheel imbalance data analysis

Data analysis for propeller (drive shaft) imbalance

Data analysis for wheel U-joints

Transmission test

Differential test

Data normalizing and ordering program

Fault display program

Each of the above programs were checked individually and then linked together to

check data acquisition, feature extraction analysis, and display functions as a

complete sequence.

b. Checkout Using Simulated Analog Signals - Laboratory oscillators, pulse

generators, attenuators, etc., were used to simulate signals from the

transducers. These signals simulat-.ed the output of accelerometers and

rotation sensors. The amplitude and frequencies were controlled so that

precise results could be predicted. The technique made it possible to

determine the proper operation of signal conditioning equipment, feature

extraction programs under dynamic data conditions, and analysis and display

routines.

A block diagram of the setup used to check synchronous analysis routines is

shown in Figure 4-1. The arrangement makes it possible to simulate accel-

erometer outputs that have frequency components that are in synchronism

with rotation pulses. The ratio of the oscillator frequency to rotation

pulses can be selected by the divider circuit. Interfering signals can

also be simulated by mixing in signals from oscillator no. 2. The second

pulse generator is used to simulate variations in vehicle speed, engine

speed, etc. The results of a typical test are shown in Figure 4-2. In

this case, the linearity and dynamic response of the driveline analyzer

4-3

"W"

OSCILLATOR NO 2 !

SIMULATED

DRIVELINE ANALYZER

AMPLrrUOE MONITOR

MIXER CIRCUIT

ACCELEROMETER INPUT

OSOLLATOR NO. 1 ATTENUATOR

' k

SIMULATED I i i i

< ' SENSOR INPUTS

SQUARING CIRCUIT DIVIDER -*

PULSE GENERATOR

NO. 1 ' ' RATIO

MONITOR

PULSE GENERATOR

NO. 2 t

Figure 4-1. SYNCHRONOUS SIGNAL SIMULATI ON

3 4 B« 7 » 9 xo 11 13 ij

INPUT VOLTAOE, PEAK-TO-PEAK 3X0

Figure 4-2. BENCH TEST - INPUT SYNCHRONOUS SIGNAL AMPLITUDE VERSUS DRIVELINE ANALYZER READING OPERATED IN

DRI"E SHAPf TEST MODE

4-4

I "W

synchronous measurement capabilities were checked in the presence : an

interfering signal.

Simulated bench tests were conducted for the following:

Differential bandpass ratio

Transmission bandpass ratio

Wheel U-joints test

Differential imbalance

Differential U-joints test

Transmission gear ratio check

Vehicle speed monitoring

Magnetic Tape Recordings of On-The-Road Tests - During the empirical

data acquisition phase magnetic tape recordings were made of vehicle

vibration and shaft rotation. Recordings were made for both good and bad

assemblies. These recordings were played back into the driveline analyzer

for fault analysis. A block diagram of the technique is shown in figure

4-3. These tests demonstrated the ability of the driveline analyzer to

operate on actual vehicle data. The advantages of this technique were:

1. A repeatable set of vibration data could be provided, thus eliminating

the variations of vehicle, operator, and road conditions.

2. The tests could be conducted in the laborai y where a full set of

laboratory instruments are available for verification of the driveline

analyzer signal conditioning and data processing.

3. The modifying of analysis procedures could be accomplished without

setting up a new road test for each change.

A technique like this was used to demonstrate to TACOM personnel the

ability of the analyzer to detect a bad differential.

4-5

~<7t

ON THE ROAD RECC1DINC OF VEHICLE VIBRATIONS ANO SHAFT ROTATIONS FOR VARIOUS OPERATING SPEEOS AND WITH GOOO AMD BAJJ ASSEMBLIES

DI»LAV

LABORATORY TEST OF THE DRIVELINE ANALY2ER US'NG MAGNETIC TAPE RECORDINGS FROM ON THE ROAD TEST

Figure 4-3. LABORATORY TESTS USING MAGNETIC TAPE RECORDINGS FROM ON-THE-ROAD TEST

4.2 VEHICLE COMPATIBILITY TESTS

The objective of this phase of the program was to demonstrate the compatibility of

the driveline analyzer with the M151A2 vehicle.

It was demonstrated that one man could install the test set in less than five

minutes.

A second portion of this _est demonstrated that the driveline analyzer would

operate from vehicle power under typical road operational conditions and would

not be affected by ignition and other electrical noise or road vibration. Tests

included:

a. Determination of vehicle speed

b. Determination of vehicle gear

c. Display of required vehicle operational conditions

d. Sequencing through each of the program tests

e. Display of test results.

4.3 ON-THE-ROAD TESTS

A limited number of the tests were conducted while operating the M151 vehicle on

the road. The purpose of these tests was to establish some baseline capability of

the driveline analyzer. These tests were limited due to lack of conTact funds and

4-6

I I !

I

tine. Plans call for extensive evaluation tests to he conducted by TACOM to

determine feasibility of the concept and to establish limits for many of the test

parameters.

4.3.1 Drive Shaft U-Joint Tests

A series of tests was conducted to demonstrate the capability of the driveline

anal/zer to:

a. Detect imbalance in the rear drive shaft

b. Detect imbalance in the front drive shaft

c. Differentiate between front and rear drive shaft faults.

The tests also demonstrated the driveline analyzer's ability to measure vibration

due to U-joints and due to engine firing. Three conditions were simulated:

a. With no weight added to either drive shaft (no weight condition)

b. With 6 ounces of weight clamped to the rear drive shaft

c. With 6 ounces of weight clamped to the front drive shaft.

The driveline analy °.r was set up to displayed measured values for the following:

Rear drive shaft first

fTn-phase component of vibration.

Rear drive shan't second

(Second harmonic component of vibration)

Front drive shaft first

(In-phase component of vibration)

Front drive shaft second

(Second harmonic component of vibration)

4-7

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The vehicle was operated on the road at a speed of 35 mph for the following

conditions:

Test No. 1 - Third gear

Test No. 2 - Fourth gear

Test No. 3 - Third gear, four-wheel drive.

4.3.2 No Weight on Drive Shaft Test

The test results for no weight added to either drive shaft, presumably good vehicle,

is shown in Table 4-1. The values provided here are considered baseline values.

Sorae significant changes in measured values as of function of third and fourth gear

operation and four-wheel drive operation are as follows:

a. Rear Drive Shaft First (In-Phase Vibration)

1. Changing from third gear to fourth gear increases the rear first from

an average of 32 to 111, a factor of 3 increase. This increase is due

to cross-coupling between engine imbalance and rear drive shaft

imbalance. Going to fourth gear causes the engine to rotate at the

same rate as the drive shaft. Drive shaft imbalance should not be

measured in fourth gear.

2. Operating the vehicle in thK'd gear and four-wheel drive caused the

output to increase from 32 to 46 average, which is insignificant. Some

small amount can be attributed to additional drive shaft loading when

in four-wheel drive. This is the same as increased loading. A part

of this increase may also be attributed to additional cross-coupling

between front and rear drive shafts.

b. Rear Drive Shaft Second

1. Changing from third {sea** to fourth gear increases the second harmonic

from 86 to 193, or a factor of a little over 2. This increase can be

attributed to cylinder firing rate and is cross-coupled to the drive

shaft imbalance wh»n the transmission is in fourth gear.

4-8

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Tablj 4-1. ON-THE-ROAD DRIVE SHAFT TEST, NO WEIGHTS (GOOD »RIVE SHAFT),

35 MPH, NO FAULT

I I I I I L I

I I I I I 1

1 ,

Condition Run No.

Rear Drive Shaft Front Drive Shaft

1st Harmonic

2nd Harmonic

1st Ha rmon i c

2nd Harmonic

Test No. 1

Third Gear

1

2

3

4

28

13

46

43

SI

70

98

95

210

204

227

203

113

201

23

13

23

13

04

03

0

3

Test No. 2

Fourth Gear

I

1

2

3

4

5

6

60

91

104

149

121

143

51

39

6 )

40

57

89

550

500

527

519

458

474

Test No. 3

Third Gear

Four-Wheel Drive

1

2

3

4

5

63

20

57

53

37

97

151

158

226

119

20

48

28

45

15

44

46

56

54

53

Units are Kg, where K Is a programmed constant and g is an acceleration at the discrete frequency.

2. Increases in second harmonic of drive shaft vibration when vehicle

operated in third gear and four-wheel drive third gear, 86 versus

150, respectively. Four-wheel drive increases the loading on the

U-joints and this increases the second harmonic output.

Front Drive Shaft

A similar set of conditions exists for the front drive shaft. Of

significance is the much closer coupling of engine firing rate to the

front drive shaft, increasing from 3 to 504.

4-9

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From this series of tests, the features were traceahle to the following driveline

assemblies:

Baseline vihration for the following:

Rear drive shaft imhalance

Rear drive shaft U-Joint

Front drive shaft imbalance

Front drive shaft U-joint

Cross-coupled effects included:

Engine imhalance

Cylinder firing rate

U-Joint and drive shaft loading due to four-wheel drive.

4.3.3 6-Qunce Weight on Rear Drive Shaft Test

The test results for 6 ounces clamped to the center of the rear drive shaft are

shown in Table 4-2. While driving the vehicle on the road, there was no significant

increase in vibration that could be detected by the driver.

Changes in measured value as a function of gear and front wheel drive were similar

to the baseline test. There was, however, a significant increase in rear drive

shaft synchronous vibration when operated in third gear. The value was 32 for no

weight added to the rear drive shaft versus 365 for 6 ounces added to the rear

drive shaft. Also, there was cross-coupling to the front drive shaft, increasing

the value to 181.

Rotation of the weight 180 degrees on the» drive shaft changed the value of the

in-phase component from 365 to 449, indicating that the new position was more in-phase

with the unfaulted imbalance of the drive shaft.

4-10

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I I I I I 1 I I 1 !

I I I I I I I I

Table 4-2. ON-THE-ROAD DRIVE SHAFT TEST, 6-OUNCE WEIGHT ON REAR DRIVE SHAFT, 35 HPH

i

Run No.

Rear Drive Shaft Front Drive Shaft

Condition 1st

Ha rmon i c 2nd

Harmonic 1st

Harmonic 2nd

Harmonic

1

| Test No. 1

Third ('.ear

j

1

2

3

388

385

324

48

87

40

188

186

169

11

11

11

Test No. 2

Fourth Gear

1

2

3

467

334

336

227

182

194

309

183

168

141

499

499

j

i Test No. 3

Tliird Gear

| 6-oz Weight

Rotated 180° i

1

2

3

463

474

412

60

5

44

183

173

188

17

12

11

Test No. 4

Fourth Gear

6-oz Weight

Rotated 180°

1

2

457

380

266

185

179

240

499

450

Units are Kg, where K is a programmed constant and JJ is an acceleration at the discrete frequency

4.3.4 6-Qunce Weight on Front Drive Shaft Test

A 6-ounce weight was clamped to the center of the front drive shaft and the vehicle

was operated at 35 mph in third and fourth gear. The results of these measurements

are shown in Table 4-3. Significant changes in measured value occur in the first

harmonic of the front drive shaft measurement when operated in third gear and four-

wheel drive. The value was 31 for no weight versus 280 for a 6-ounce weight on the

front drive shaft. These measurements were taken with the rotation sensor on the

rear drive shaft.

4-11

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Tablc 4-5. ON-THE-ROAJ) DRIVE SHAFT TEST, 6-OUNCK WEICHT ON FRONT DRIVE SHAFT, 35 MPH

When four-wheel drive is disengaged, there is a lack of good synchronism between

front and rear drive shafts. The low reading for the front drive shaft

the four-wheel drive is not in use.

Oondition

Test No. 1

Third i.e.ir

ve Shaft

2nd Harmoni c

82

64

5 7

72

26 L

310

276

25 5

Run No.

1

■■>

3

4

Ke.-ir I)ri Kronl Or [ve Shaft 1st

Harmonic

32

41

60

24

1st Harmonic_

16

16

04 1 20

2nd Harmonic

07

12

0 3

I 11

Test No. 2

Fourtli Gear

1

■>

3

4

81

88

101

95

34

6 3

40

34

1

565

j 614

1 600

553

Test No. 3

Third Gear

Four-Whee1 Or i ve

— ~ — ■■-- —

1

3

34

34

57

186

147

16 3

83

anil g is an

279

260

301

1

61

60

62

Test No. 4

Third Hear

Check on Test No. 1

, ... ,,„ , .

1 30 ,

23 0 3

Units are Kg, where K discrete frequency

is a programmed constant ecceleration at the

was when

A summary of imbalance drive shaft test results is shown in Table 4-4. An analysis

of the data shows the following:

a. A drive shaft imbalance of 6 ounces is easily detected and as little as

1 or 2 ounces can probably be measured.

4--12

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Table 4-4. SUMMARY OF IMBALANCED DRIVE SHAFT TEST RESULTS

f jMeasured Value

Condition 3rd ('.ear Ird (.ear t-wneei Drive 4tn t.ear

Weight Shaft 1st 2nd 1 St 2nd 1st 2nd

GD GD CD (TvT) CD CD Basel'ne-- Baseline-- Ratet ine-* In« rease Im rease Increase

Rear l.ood Cood (iood over base- Ilne due to U-)olnt stress in 4-wheel

over haae- 1 lne doe to engine Hull« lam e

over base- 1 ine due to cylInder firing

No weight on drive shaft CD CD

drive

CD GD CD Values low. Rotation Front and rear drive Increase Large In- sensor on rear drive shaft locked together due to crease due shaft. Ur1ve shaIts rotate avmhronlned to engine to cylInder

Front are not synchronized. This It due to small differences in front and rear wheel diameters

front drive shaft Imbalance firing rate

(365) GD CD CD Large In- In base- (This series of tests Show* Shows

Rear crease due to weight on rear drive shaft,

line range was not run) weight on rear drive shaft plua engine

effect of cylInder firing

Six ounces on Bad rear imbalance

rear drive shaft drive shaft ——j

CD CD CD CD I tu rease In base- (This series of test Shows Shows due to 1 lne range was not run) cross- effect of

Front iross- coupl ing from weight on rear drive shaft

coup I ing from rear drive shaft plus engine Imbalance

cyl Inder firing

CD GD GD CD GD CD Rear BaselIne-- Basel lne-- BaselIne-- Shows U- Value high Value high

C.ood rear Cood Good rear Jolnt due to shows drive shaft drive shaft stress due engine cylinder

Six ounces on front drive shaft

to 4-wheel drive

Imbalance firing

CD CD GD GD GD (583j)

Values low. Rotation Value high Basellne-- Value low Value high sensor not synchronized due to Cood. due to lack shows

Front to front drive shaft weight on Slightly of rotation cylinder front drive hinti due to sensor firing shaft. Bad 11- joint synchron* rate drive shaft stress izalIon

4-13

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h. Hrive shall imbalance should he made with the vehicle operating In third

gear. I'DUILII gear operation (1 to 1 transmission ratio) permits excessive

cross-coupling of engine imbalance that interferes with drive shaft

imbalance and cylinder firinj

measurements. ig cross-couples into drive shaft U-joint

c, Front drive shaft measurements must use the front drive shaft rotation

sensor. (iood results were obtained with the vehicle operating in four-wheel

drive when the two drive shafts were mechanically locked together.

d. Measurement of U-joint source frequencies showed increases in measured

values directly correlating to U-joint loading. This indicated U-joint

faults, if inserted, would be easily detectable.

e. Contributions of engine imbalance were easily measured as indicated by

the fourth gear operation.

Contributions of cylinder firing rat

the fourth gear operation. e were easily measured as indicated by

*• 3.5 iinjjLhe-_Koad Differential Test

The fU51 vehicle was operated at 35 mph on the road under various gear and front

wheel driv<:> conditions while conducting front and rear differential measurements.

The results of these tests are shown in Table 4--5. The driveline analyzer program

was changed to provide readouts for the magnitude of the high bandpass vibration

(High-IJ) and the ratio of the high bandpass to the low bandpass (Ratio). The

results of these tests indicated the following:

a. Operation in third gear shows that the rear differential has a higher high

bandpass output than the front differential. The reason for this is that

the rear differential is operating under load.

Operation in third gear and four-wheel drive greatly increased the rear

differential vibration level. These increases in rear differential vibra-

tion can be attributed to the differences in front/rear wheel circum-

ferences which results in the production of a higher level of internal stress.

4-14

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Table 4-5. ON-THE-ROAD DIFFERENTIAL TEST,

GOOD DIFFERENTIAL, 35 ?0'H

I I I I I I I I I r

i i i

Condition Run No.

Rear Differential Front Differential

High-B Ratio

1

1

3

2

2

2

3

High-B Ratio

Test No. 1

Third Gear

i

2

3

4

5

151

294

191

9 3

301

86

84

!i 4

89

87

91

87

81

82

83

>-

Test No. 2

Fourth Gear

1

2

3

4

5

464

394

381

359

358

Test No. 3

Third Gear

Four-Uheel Drive

1

2

3

4

5

551

733

669

593

684

3

3

3

2

3

200

192

190

180

208

Test No. 4

Fourth Gear

Four-J/heel Drive

1

2

3

4

1011

911

666

789

4

4

3

3

188

189

170

168

1

1

1

1

High B: The magnitude of accleration of the programmed high band frequencies. Ratio: The ratio of the high frequency bandpass measurement to the low fre- quency bandpass measurement. Units are Kg, where K is a programmed constant and g is an acceleration at the discrete band of frequencies.

c. Operation in fourth gear causes an increase in rear differential vibration

over the vibration experienced in third gear. Also the bandpass ratio has

increased from 1 to 2 or 3. While operating in fourth gear, the engine is

directly coupled to the drive shaft such that cylinder firing and engine

torque variances are more directly coupled to the rear differential. This

causes an increase in ring gear tooth chatter.

4-15

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(i. "peration in fourth (tear and four-wheel drive lncrea«ed both front and

roar differential outputs as would he expected. Also, the bandpass ratio

for the rear (inferential increased fron 1 to 1 or •'« indicating much more

tooth or bearing chatter.

It should he noted that the above test data was talen on a vehicle that was believed

to have good differentials in both front and rear. The above test data, however,

would indicate that the rear differential was marginally bad. This rear differential

had been removed and adjusted several times during the program and, therefore, could

have been misadjusted during these tests.

These preliminary tests indicate the following:

a. The effect of loading variation indicates that the bandpass ratio technique

used in the driveline analyzer can be used as a diagnostic tool for

differentials.

b. The differential vibration can he separated from the effects of other

assemblies and from the effects of road noise.

c. Differential tests should be run in third gear and four-wheel drive, as the

vibration levels of faulty components are maximized in this mode,

4.3.6 On-the-Koad Test of Wheels

The vehicle was operated on the road in third gear at 35 mph. Weights of 3 ounces

and 20 ounces were added to the wheels as shown in Table 4~o. Analysis of these data

indicated no significant definitive features for weights being added to the wheels.

Some trends <:re indicated, however.

a. Weights added to the right rear wheel did increase the second harmonic

component. It did not significantly increase the fundamental.

b. Weight added the right front wheel decreased the second harmonic

component associated with that wheel. This may be an indication that the

wheel was previously seriously out of balance and that the addition of

weight tended to balance the wheel.

4-16 * I I

I I 1

Table 4-6. ON-THE-ROAl) WHEEL TEST, THIRD CHAR, 35 UPH, FOUR LEGS ON EACH TEST

I I I

Condition

Rear Wheels Front Wheels

Right Wheel Left Wheel Right

First

Wheel

Second

Left Wheel

First Second First Second First Second

8-oz Ueight 12 248 34 84 56 122 19 205

Right Rear 73 139 31 21 70 239 35 158

63 162 28 57 87 59 21 31

j 20-oz Ueight 21 211 25 60 96 20 35 71

Right Rear 31 200 10 53 45 323 19 203

41 270 46 33 24 189 12 295

18 239 18 41 42 228 22 80

Ho Weight 12 133 40 30 bl 100 31 59

35 42 22 37 56 150 35 98

42 21 43 47 48 96 43 70

20-oz Weight 30 89 23 121 58 81 49 76

Right Front 28 62 29 144 18 83 23 157

58 89 34 155 24 74 17 134

First - A measurement value of the vibration in s^ /nchroniz ism with the funda- mental frequency of wheel rotation. Second - A measurement value of the vibration twi< :e the wh eel rotation frequency. Units are Kg, where K is a programmed constant an< i g is an accelers tlin at the discrete band of frequencies.

c. First harmonic measurements did not vary significantly with addition of

weight, and the measured values were all very low, indicating a need to

increase the sensitivity of the fundamental feature extractor for wheels.

Additional test of wheel imbalance showed careful balancing of wheels should be done

before addition of test weights, and the program should be modified to increase the

gain of the fundamental extraction feature.

4-17

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4.4 SUMMARY OF TKST RKSW.TS

The tests previouoly described showed the following:

a. The driveline analyzer was capable of conducting all tests set forth in

the design objectives as demonstrated by the bench test.

b. The driveline analyzer was compatible for use on the M151 vehicle and

can be installed by one man in less than 5 minutes.

c. <>n-the-road tests conclusively demonstrated the ability of the driveline

analyzer to detect the following assemblies:

Front drive shaft imbalance

Rear drive shaft imbalance

Front drive shaft U-joint

Rear drive shaft U-joint

Fngine imbalance

Engine vibration

Cylinder firing

Front differential vibration

Rear differential vibration.

Preliminary tests indicated the probable success of wheel imbalance and wheel U-joint

vibration; however, additional control of faults and adjustment is required.

The bench test indicated that the «slipping clutch test will work on the vehicle,

but limitations on available time prevented conducting this test.

The TACOM test and evaluation should include a program to define how the driveline

assemblies fail and should include provisions for controlling the inserted driveline

faults.

4-18

^*&*&flH&^ii^ S»*WK«WM»WiftW«^Mfcfe>frT^iK .^

h SECTION r>

SUMMARY

The scope of work specified that Northrop furnish the supplies and services necessary

to design and fabricate, for TACOM test and evaluation, a driveline analyzer designed

to detect faulty driveline assemblies in the Mlr)l stries 1/4-ton trucks. This

effort has been completed and the driveline analyzer has been delivered to TACOM.

Compliance to the hardware requirements is shown in Table 5-1. The procedures used

to define and improve the test techniques utilized for the analyzer design involved

both analytical and empirical approaches. Comparison of the theoretical vibration

properties of the driveline assemblies to the recorded features from actual baseline

and a simulated faulty M151 vehicle led to the validation of the selection of the

following test techniques:

I I I

a. Discrete synchronous frequency analysis for wheels, axles, U-joi ts, and

driveshafts

b. Bandpass ratio techniques for differential, transmission, and engine

c. Engine shaft rate versus slipping clutch.

The test techniques selected established the need for the quantity and types of

sensors, the specific signal conditioning and processing, and the various portions

of the vehicle's drivelines to be operated under controlled conditions.

Figure 5-1 depicts the resultant block diagram for the driveline analyzer which is an

integrated series of tests that provide a tool for automatically diagnosing the

vibration source in the vehicle as it is driven on the road.

The large number of data points projected for the test techniques, the accuracy

required, the number of constants, and the number of calculations required clearly

indicated a requirement for some form of digital processing and control systems.

Since the program is a feasibility investigation, test techniques are likely to

5-1

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TabJe 5-1.

Requi rement

Dimensions:

]2 x 18 x 18 in.

Insensitive to ve- hicle vibration

Powered by vehicle electrical system

Simple installa- tion by one mechanic

Operate by one mechanic

Determine If oper- ating properly and

Autotest with re- sults displayed to indie :e Hood/Bad

COMPLIANCE TO HARDWARE SPECIFICATION

jCompl ic -ompliance

Yes

Yes

res

Yes

Yes

Yes

Yes

Logic/Control, 12 x 14 x 17 in. Operator Display, 6 x 7-1/7 x 2 in.

Logic/Control, 40 lb;

Senso.- Assemblies, 11 lb (total); Operator Display, 2 lb

Designed to operate on +25.2 + 3V DC (battery cell voltage range); current required, 3 amps

Logic/Control, display, and 3 sen- son assemblies with 5 cables

j One button to in it tat • selected tesü

Exercises internal logic and verifies circuits prior to each test

Test is automatial.lv sequeneed; display of faults is programmed to be shown in order of significance

change. This established a need for a stored program rather than a hard-wired

approach. Requirements for displaying some 30 test results were identified and

indicated the requirement for a small alphanumeric display. The alpha portion of

the display was required to provide name identification for the large number of

tests; numerics were required to indicate degree of badness and order of fault.

The operational modes involved in performing the Lests require operating the vehicle

in a specified gear, at a specified speed, along a prescribed path. Because these

tests are conducted on the road, traffic and other considerations will cause inter-

ruptions in the test sequence. Provisions were made to provide the vehicle operator

with indi alors that instruct him concerning vehicle gear, engine rpm, vehicle

speed, and the identification of the test being conducted, together with indicationr.

of whether or not the operator is meeting the required operational conditions. The

types of Information that are presented to the vehicle operator are:

• Engine rpm for engine and clutch tests

• Transmission gear for specific test modes

5-2

-V K * -

f*W

ROTATION SENSORS

«COUNT!« TIMER

CHANNELS

PHASE LOCKED LOOPS

CENTRAL PROCESSOR

MULTIFKXEM

AC« L EROMETERS

SWITCHES SIGNAL

CONDITIONERS

TEST RESULTS DISPLAY

AND CONTROL

VEHICLE OPERATIONAL

OISPLAV

ENGINEERING OISPLAV

Figure 5-1. DRIVELINE ANALYZER BLOCK DIAGRAM

Speed, in mph, for clutch, transmission, differential, and wheel tests

Engine rpm

Speed, in mph

Waiting for conditions to be met

Invali". test

Test complete.

The test and evaluation portion of the driveline analyzer program involved three

phases:

a. Bench test of the computer program sequences and measurements of simulated

transducer signals

b. Bench test of the diagnostic program sequences, using magnetic tape

recordings of transducer signals from on-the-road tests

5-3

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c. Road tests to verify the ability of the test set to measure vehicle

operational parameters and to display them to the vehicle operator.

Table 5-2 displays, in summary form, the results of this hardware and software

verification effort.

The resultant hardware developed during this program allows for flexibility In vary-

ing the parameters of the individual diagnosti techniques. Instructions to the

operator for conduct of the tests, the gains and bandwidths of the sensor signals,

the cross correlation of selected sensor signals, and the resultant decision and

display of fault indications are programmable to allow for selection variation of

each parameter. The effort resulted in the development of an effective engineering

tool nat can be utilized to closely examine the feasibility of using vibration

signatures as a method for Army vehicle driveline diagnosis.

1 3 1

t

5-4 I 4

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SECTION 6

CONCLUSIONS

1. The definitizing of qualitative faults in terms of quantitative mechanical

deviations proved difficult and requires more study by the Army (para-

graphs 2.4 and 4.3.3)

2. Simulation of fualts on the vehicle proved difficult to define and control

(paragraphs 2.4 and 4.3.3).

3. The effects of a fault in a defective assembly can cross-couple to a good

assembly, causing the good assembly to appear fault (paragraphs 2.6.2, 2.7, and 2.8).

4. Spectral lines synchronized to a shaft rotation exhibits very good signatures

of mechanical parts (paragraphs 2.6.3 and 3.8.1).

5, Discrete frequency techniques are useful to identify specific parts, including

wheels, drive shafts, U-joints, gears, bearing races, and ball bearings (para-

graphs 2.7, 2.8, and 2.8.1).

6. Discrete f

en screte frequency techniques are not practical for the transmission or differ-

tial assemblies due to their large quantities of frequencies requiring neas-

urement and comparison (paragraphs 2.7 and 2 8)

7. Ratio of high- to low-frequency bands did exhibit an increase when misadjustment

or fault was involved in the differential (paragraphs 2.7 and 2.8).

8. A specially designed CMOS computer was the optimum unit to process and control

the driveline analyzer (paragraph 3.2.1).

9. The driveline analyzer performs in the manner for which it has be

and programmed (paragraph 4.1). en designed

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10. The driveline analyzer is compatible wiili the physical and operability require-

ments of the M151A2 vehicle (paragraph 4.2).

11. The driveline analyzer is capable of performing its design and programmed

functions on the M151A2 vehicle (paragraphs 4.3, 4.3.1, 4.3.2, 4.3.3, 4.3.4,

4.3.5, and 4.3.6).

12. The diagnostic programs of the analyzer require more test and refinement, with

the following controlled variations (Section 4):

• Variations in road conditions

• Variations in driving patterns, including speed variations and driver

characteristics variations

• Variations in degrees and types of faults

• Variations in vehicle conditi on

• Variations in degrees of multiple faults.

6-2

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RECOMMENDATIONS

Three actions are recommended based on the results of this program:

a. Refine the methods for simulating faults in a measurable controlled

manner (Section 6, paragraphs 1, 2, and 3).

b. Conduct a test program to gain data related to the fault detectability of

the analyzer's test techniques (Section 6, paragraphs 5, 7, 9, 10, 11,

and 12).

c. Develop an improved method for sensing the rotation of the drivelines and

engine (Section 6, paragraph 12).

7.1 FAULT SIMULATION

The simulation of field-faulted assemblies requires extreme care to verify that the

faulted condition results in vibration that is truly representative of field failures,

The Army should identify a set of real-world driveline failures that occur in the

field and develop controlled w?.ys of inserting these faults into the test vehicles.

Levels of unacceptable vibration should be separately determinable as a function of

the degree of fault.

7.2 TEST PROGRAM

The driveline analyzer should be evaluated using these controlled faults singularly

and in combination. Analysis should be made of these results to evaluate how future

extraction, cross-coupling, weighting, and limit parameters should be modified to

improve the test capability and repeatability of the driveline analyzer's measure-

ments. This must be done not only for the M151A2 vehicle but for any other vehicle

to which the Army intends to apply the driveline analyzer.

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.1 Once effectiveness has been established for the M151A2 vehicle, the analyzer should

then be reprogrammed and tested with other vehicles. Having done this, the Army can

determine whether or not such a test set would be truly effective in the depot

environment.

The empirical results of this program and the preliminary evaluation of the drive-

line analyzer have shown the ability to measure vibrations well below levels that

would result in maintenance action. These vibrations are traceable to specific

assemblies and components. With additional testing, the Army may find the driveline

analyzer effective as a prognostic tool.

7.3 ROTATION SENSORS

The rotation sensors that were utilized in this application proved very effective

in the laboratory and during most of the empirical testing. There were road test

conditions that did result in misleading test results. These have been traced to

be the effects of early morning or late evening sunlight shining directly on the

sensor. The sensors are very workable, as this condition is realized by the user,

but the sensing approach on the sensor design should be improved before a prototype

phase is undertaken.

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SECTION 8

DISTRIBUTION LIST

ADDRESSEE

NO. OF COPIES

Commander U.S. Army Tank-Automotive Command Warren, MI 48090 ATTN:

Research, Development and Engineering Directorate, AMSTA-R Chief Scientist, AMSTA-CL Propulsion Systems Division, AMSTA-RG Engineering Science Division, AMSTA-RH Armor, Materials and Components Division, AMSTA-RK Systems Development Division, AMSTA-RE Maintenance Directorate, AMSTA-M Product Assurance Directorate, AMSTA-Q MICV Project Manager, AMCPM-MCV XM1 Project Manager, AMCPM-GCM Technology Library Branch, AMSTA-RWL

1 1

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Commander U.S. Army Material Command ATTN: AMCRD-GV

AMCRD-RD Washington, D.C. 20315

Office, Chief of Research and Development Department of the Army ATTN: CRDCM Washington, D.C. 20310

Commander Defense Documentation Center ATTN: DDC-IR Cameron Station Alexandria, Virginia 22314 12

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DRIVELINE ANALYZER M151 1/4 TON UTILITY TRUCK

AUTHOUT*)

A.D. DeROLT P.J. LEIBERT

Northrop Corp., Electro-Mechanical Division 500 East Orangethorpe Avenue ,/

I Anaheim California 92801 lt. COMTMH.LIMO orriCt KAMI MO AOOMM

U.S. Army Tank Automotive Command Diagnostic Equip., AMSTA-RGD Warren, Michigan 48090

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Driveline Synchronous frequency analysis Bandpass ratio analysis

The objectives of this development program were to determine the feasibility of using data obtained from measuring discrete selected parts of vibration signatures for Army vehicle driveline diagnosis and to provide the U.S. Army Tank Automotive Command (TAC0M) with an advanced development model driveline analyzer designed to identify faulty driveline assemblies of an Army K151A2 1/4-ton utility truck. The development program performed by Northrop included

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20. ABSTRACT

the correlation of simplified analytical models to empirical data, and the design, fabrication, and functional test of one portable driveline analyzer test set complete with sensors and a remote display console.

Analytical models to determine how driveline components and assemblies Ren- erate excessive vibration were developed and used to identify vibration features that were potentially good indications of faulty components. Follow- ing this initial effort, the driveline assemblies of an Ml 51 vehicle were instrumented for vibration and shaft rotation data. During road test, the data was recorded on magnetic tape and was analyzed on Northrop computers to develop power spectral density plots. These plots were used to provide empirically derived excessive vibration features of good and bad assemblies.

The analytically derived vibration features then were correlated to the empirically derived features to identify errors in cither of the processes. Good correlation of analytical and empirical data was used as criteria for selecting features that would provide the highest probability of detecting faulty driveline assemblies and the lowest probability of identifying a good assembly as being bad. From this analysis, vibration features were selected that were compatible with a simplified road test and that were practical for this application.

A portable test set was designed and constructed, consisting of a driveline analyzer chassis, a remote display console, and a set of sensor assemblies. 'Hie driveline analyzer chassis contains amplifiers, programmable filters, counters, phase-locked loop circuits, and a digital computer with both random access and read-only memories. The remote display console contains vehicle operator instruction displays.

Digital computer programs were prepared for use with the driveline analyzer test st!t to provide the vehicle operator instructions, gather the vibration data during the vehicle road test, analyze the data, and display test results in terms of faulty driveline assemblies.

The driveline analyzer set was tested utilizing simulated t»st data and data recorded on magnetic tape. Sensor installation compatibility, test sequence, and vehicle control data acquisition, processing, and display have been verified on the M151 vehicle.

The test set was demonstrated to TACOM personnel using simulated and recorded data in the laboratory. Installation of the test set on an M151 vehicle was also demonstrated. After this demonstration to TACOM, Northrop conducted a number of road tests which demonstrated the ability of the driveline analyzer to detect drive shaft, U-joint, engine vibration, and differential types of faults.

This contract was conceived to assist TACOM in their goal of advancing the technology in the field of Army vehicle diagnostics. The M151 driveline analyzer feasibility model has been delivered to TACOM for test and evaluation. The driveline analyzer has verified many of the diagnostic concepts; however, further testing and engineering improvements are necessary to determine the adequacy of the diagnostic concepts.

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