adaptive sterr

8/10/2019 adaptive sterr

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ECE5320 Mechatronics

Assignment#01: Literature Survey on Sensors and Actuators

Topic: Harmonic Drive

Prepared by: Zeke Susman

Dept. of Electrical and Computer Engineering

Utah State UniversityE: [email protected];

F: (435)797-3054 (ECE Dept.)

3/11/2010


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Outline Introduction Reference list

To probe further

Major applications

Basic working principle illustrated

A typical sample configuration Major specifications

Advantages

Limitations

Assembly and Installation

Selection

Cost

Suppliers

12/27/2014 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

Slide-2


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Introduction

Harmonic Drives (HD) were invented in the late 1950 byC. Walton Musser.

HD have become a primary choice when precise

positional accuracy and repeatability are required.

HD is capable of high gear ratios, zero backlash, and

high torque-to-weight ratios.

HD are very compact with torque-to-weight ratios 50%

smaller and 30% greater efficiencies than other gearingmechanisms.


Slide-3


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Reference list A. Lauletta, The Basics of Harmonic Drive Gearing, Gear Product News, April 2006. pp. 32-36

Wikipedia, Harmonic Drive, Widipedia, [Accessed: March, 8, 2010] , [Online]

http://en.wikipedia.org/wiki/Harmonic_drive.

KAZEROONI, H. Dynamics and control of instrumented harmonic drives, Journal of dynamic systems,

measurement, and control. 1995, vol. 117, no1, pp. 15-19 (8 ref.) American Society of Mechanical Engineers, New

York, 1971.


Slide-4
http://en.wikipedia.org/wiki/Harmonic_drivehttp://en.wikipedia.org/wiki/Harmonic_drive


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To explore further

(survival pointers of web references etc) http://www.hdinfonet.com/harmonic_drive.html

http://www.powertransmission.com/issues/0706/harmonic.htm

http://en.wikipedia.org/wiki/Harmonic_drive

http://www.nacharmonicdrive.com/index.html

http://www.harmonicdrive.net/

http://www.roymech.co.uk/Useful_Tables/Drive/Harmonic_Gears.html

http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518 http://machinedesign.com/article/flexible-gears-minimize-gearhead-backlash-for-life-0607


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http://www.hdinfonet.com/harmonic_drive.htmlhttp://www.powertransmission.com/issues/0706/harmonic.htmhttp://en.wikipedia.org/wiki/Harmonic_drivehttp://www.nacharmonicdrive.com/index.htmlhttp://www.harmonicdrive.net/http://www.roymech.co.uk/Useful_Tables/Drive/Harmonic_Gears.htmlhttp://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://machinedesign.com/article/sometimes-it-pays-to-be-eccentric-0518http://www.roymech.co.uk/Useful_Tables/Drive/Harmonic_Gears.htmlhttp://www.harmonicdrive.net/http://www.nacharmonicdrive.com/index.htmlhttp://en.wikipedia.org/wiki/Harmonic_drivehttp://www.powertransmission.com/issues/0706/harmonic.htmhttp://www.hdinfonet.com/harmonic_drive.html


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Major applications

Robotics Ground Robotics (chaosAutonomous solutions)

Prosthetics /Cybernetics(Cyberdyne, Honda)

Industrial Robotics (car manufacturing, silicon wafer production)

Aerospace

Satellites, Aircraft

Medical Equipment (mri equipment, microscope positioning)

Communications

Radar and satellite tracking systems


Slide-6

http://www.hdinfonet.com/applications.html


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Basic Working Principle

All harmonic drives consist

of the same three basic

elements:

A Circular Spline

B Flex Spline

C Wave Generator


Slide-7

http://www.powertransmission.com/issues/0706/harmonic_fig1.jpg


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Wave Generator

The wave generator (WG) consists of

two parts: (yellow inner ring)

An elliptically shaped steel plug

Ball bearing

The plug is pressed into the bearingso that the bearing conforms to the

plugs elliptical shape.

The WG is pressed into the flex

spline.

The WG is attached to the drive inputin the most common configuration.


Slide-8

http://www.hds.co.jp/HDS_hp_english/english/principle/movecomp/movecomp.html


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Flex Spline

The flex spline (FS) is a thin walled steel

cylindrical cup.

It has teeth machined into outside upper

rim of the cup.

The FS has a large diameter to allow

radial flexibility while maintaining high

torsional stiffness.

In common configuration rotates in

reverse of the wave generator plug.

The rotating output element in the

common configuration.


Slide-9

http://www.hdinfonet.com/images/instruction-4.jpg


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Circular Spline

The Circular Spline is a

rigid circular ring with teeth

on the inside edge that mate

with the teeth of the flex

spline (blue outer ring). It is the non-rotating

element in the common

configuration.


Slide-10

http://www.hds.co.jp/HDS_hp_english/english/principle/movecomp/movecomp.html


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How it works: Reduction


Slide-11

The gear reductions are aresult of the flex spline

having two less teeth than

the circular spline.

1:100202200

200

Notice the negative sign because the flex splinerotates in reverse of the wave generator

Click forAnimation


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How it works: Flexing

The Harmonic Drive

mechanism relies upon the

elastic properties of the the flex

spline material (steel).

The resulting deformation iswell below the endurance limits

of the material, if the peak

torque is kept below the rated

maximum. This flexing preloads the gears

and helps reduce noise, friction,

and backlash.


Slide-12

http://www.harmonicdrive.net/media/reference/operatingprinciples//diagram2.gif


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How it works: Zero Backlash


Slide-13

Because the flex spline ispreloaded almost zero back

lash is achievable 6,3 or 1 arc-

sec depending on size and

reduction ratio.

The amount of backlash

between mating teeth remains

constant over the lifetime of

the drive because the

preloading and the relative

motion of the gears.

Click forAnimation


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How it works: Efficiency


Slide-14

Standard gear mechanismshave contact between only a

couple of teeth at any given

time.

The unique design of theharmonic drive allows for

30% of the teeth to be in

contact at any give time.

Increases torque transfer

efficiency to be between 65%

and 90% highest of any gear

transfer mechanism.

Click forAnimation


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Configurations


Slide-15

http://www.powertransmission.com/issues/0706/harmonic.htm


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Sample Application

Exoskeletal Robotics is an idealapplication of Harmonic Drive

technologies. The Japanese company

Cyberdyne is producing these suits

and are using HD at each joint. Each

blue circle represents an integrated

stepper and a harmonic drive.

Because the drive and the motor are

coaxially aligned a very compact

assembly is achievable with very hightorque and low weight.


Slide-16

http://www.cyberdyne.jp/English/robotsuithal/index.html


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Major Specifications

There is not limitation of type motor to providethe input actuation.

Input/output torque requirements

Hollow shaft vs. solid shaft

Input Power

Lubrication types and operating temperatures

Size and Weight


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Advantages

Simple construction (3 piece) Light weight (up to 50% lighter than conventional

reducers)

Compact (single stage, pancake style, coaxial input output shafts)

High efficiency in gear ratios between 60:1 to 250:1

efficiencies of 65% to 95% are achievable.

High positional accuracy (0.008)

High torque-to-weight ratio (100:1, 160:1, 200:1)


Slide-18


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Advantages cont.

Zero backlash Infinite lifetime w/ constant performance

Cost effective

Hollow Shaft Quiet operation because low tooth impact, elliptical

shape keeps gears tight and smooth.


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Limitations

Gear reductions below 30:1 are limited because ofthe possibility of fatiguing the flexspline.

Restricted to input power levels below 6000W.

Large models experience lower efficiency

High ratio drives are non-backdrivable

Must be careful of operating temperatures, and

lubrication techniques.


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Assembly

1. The ball bearing is pressed aroundthe wave generator plug and

conforms to the elliptical shape of

the plug.

2. The wave generator Ais inserted

into the flex cup B. The cup alsoconforms to the elliptical shape of

the WG.

3. The flex cup Bis inserted into the

circular spline C.


Slide-21

A

A

B

B

C



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Installation Issues

When installing the waveflex spline into the

circular spline care must

be taken to ensure a

concentric meshing of thegears.

Can be verified by

inspecting the gap on theminor axis.


Slide-22



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Installation Issues

Care must be taken toallow the Flex spline cup

enough clearance to

deflect normally

The outer wall

The bottom of the cup


Slide-23

http://www.hdinfonet.com/application_notes.html


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Lubrication

Lubrication types include oil and grease. The type of lubrication required depends on the size of the

unit and operating temperature and the ambient temperature

difference.

Temperature difference must be kept below 60 C

Oil is generally used for : Higher temperatures

Larger unites

Vertical installations


Slide-24

http://www.nacharmonicdrive.com/id66.html


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Selection

Harmonic Drives have many specifications but the basicsare:

Input/output Torque Ratio

Lubrication Type Output Rpm

Physical size and weight

Maximum Backlash (6,3,1 arc/sec)

Maximum Transmission Error (6,3,1 arc/sec)


Slide-25


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Cost

Harmonic Drives range in cost based on size,lubrication, and configuration type.

The drive costs a bit more than other reduction

devices, but the savings is made up by being ableto reduce the requirements for the motor and the

savings in size and weight.

Based on the myriad of configuration possibilitiesit is recommended to contact a sales rep for actual

pricing.


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Suppliers

Harmonic Drive - http://www.harmonicdrive.net/ Harmonic Drive Gearing -

http://www.hdinfonet.com/firstpage.htm

Harmonic Drive AG -http://www.harmonicdrive.de/en/index.htm

Heason - http://www.heason.com/

12/27/2014 ECE5320 Mechatronics Assignment#1 Survey on sensors and actuators

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http://www.harmonicdrive.net/http://www.hdinfonet.com/firstpage.htmhttp://www.harmonicdrive.de/en/index.htmhttp://www.harmonicdrive.de/en/index.htmhttp://www.hdinfonet.com/firstpage.htmhttp://www.harmonicdrive.net/

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