Customer Solutions
by John Niezgoski, Senior DevelopmentEngineer, Roush Industries,
Inc.
The Challenge: Designing and fabricatinga portable test cart to
validate the cam andcrank timing relationship of nearly
14,000complete V6 automotive engines within two weeks.
The Solution: Leveraging the rapidsoftware prototyping power of
LabVIEW, alongwith the integration of custom-fabricatedhardware and
E-series data acquisition (DAQ)boards, to quickly create a mobile
cam andcrank timing test cart.
Cam Gear Replacement When a design change required the retrofit
of a new cam gear on approximately 14,000completely assembled,
uninstalled automotiveengines, the primary hurdles we faced
werethroughput and critical timing constraints.The replacement of
the cam gear required thetensioner and belt to be held static by
thetechnician while we installed the new gear.Any slippage during
the process could easilyresult in timing changes and
ultimatelycatastrophic failure of the engine upon final
installation.
The existing end-of-line (EOL) testmachines were not practical
for the retestingof the engines because the process was tootime
consuming and costly. The enginemanufacturer then turned to Roush
engineersto create a portable test cart for the validation
of the cam gear replacement and cam andcrank timing of the V6
automotive engines.None of the assumptions pertaining
toconventional EOL test machines wereapplicable – the apparatus
needed to belightweight and maneuverable, relatively lowcost and
maintenance free, require very little
or no training to use, andflexible enough to detect everyfailure
mode known for theUUT. The greatest challengefor the development
team was the project timing. Due to housing limitations and
lostrevenue, the test carts had tobe completed within two weeksof
project commencement.
A Portable Hardware System The signals required toaccurately and
repeatedly testthe engines were as follows:• CAM signal – (0 to
Excitation Voltage) Pulse train representing the position on the
camgear. Acquired from thefactory cam sensor on the engine
block
• CRANK signal – (0 to Excitation Voltage) Pulsetrain
representing theposition of the crank. Acquired from thefactory cam
sensor on the engine block
• External Battery Voltage – Battery voltagelevel of the onboard
power source used tocrank the engines
We based our decision to use the National Instruments E-series
DAQ device AT-MIO-16E-2 on the relatively simple I/Orequirement
coupled with the cost constraint.
We placed the DAQ card in a rugged, lunchbox-style computer
andtethered it to an SCB-68for ease of connectivity.The SCB-68
alsoprovided access to the5V excitation available
on the DAQ card that we used to excite thecam and crank
sensors.
Since the engine tests were to be coldtests, the hardware
complement needed tocrank the engines without combustion togenerate
the cam and crank signals. Wedetermined that the engines had to
be
cranked a minimum of eight revolutions but could not exceed
twelve revolutions toconserve battery life. With these conditions
in mind, we fabricated a fixture thatinterfaced directly with
transmissionmounting bolts found on the engine. Wefitted a
reverse-spinning starter to the mount,ensuring proper mesh with the
exposedflywheel and the starter gear. As a final step,we
implemented a hand-held trigger device to permit the user to
enable/disable the startermotor. The entire assembly was stable
enoughto achieve the large torque required for enginecrank but also
lightweight enough to bequickly and easily moved from one UUT to
the next without the use of any tools.
Minimal User Interaction InterfaceThe primary goals of the
custom LabVIEWapplication were as follows:• Efficiently acquire cam
and crank signal
pattern with minimal engine revolutions (max of 10 revs)
Industry: AutomotiveProducts Used: LabVIEW™ • NI-DAQ™
The complete cam and crank timing test cart.
NI Products Enable Rapid Development of Cam and Crank Timing
Test Cart
The entire assembly was stable enough to achievethe large torque
required for engine crank but alsolightweight enough to be quickly
and easily movedfrom one UUT to the next without the use of any
tools.
02_663_821_101_8.5x10.875.qxd 10/11/02 2:32 PM Page 1
Customer Solutions
• Calculate cam/crank relationship without the aid of an encoder
to identify engine position
• Perform testing with minimal user interaction
• Execute complete test in less than one minute
• Log results in an SQL-compatible database for future
analysis
Since the testing was to be done by endusers without a lot of
technical training, we designed all processes to be transparentand
require no input from the operator. We accomplished this by first
automatingthe process by which the tracing number and part number
of the UUT was entered. We implemented a hand-held bar codescanner
to enter the information.
Once scanning of the bar codes wascomplete, the user simply
pulled the trigger of the starter gun to commence the test as
instructed via the main screen. Afteracquiring the minimum amount
of datarequired to accurately determine the cam and crank timing
relationship, the user wasinstructed to terminate the test and to
tag the UUT with the test results. Althoughthe actual timing test
required only seconds, a complex algorithm performed steps thatwere
transparent to the user.
Most tests of this nature utilize an externalencoder to easily
render the engine position at any given time. Since an external
encoderwould have required an extended setup timefor each engine,
the calculation was doneprogrammatically instead. The falling edges
of the cam and crank signals coupled with the known pattern that
exists between thempermitted the proper determination of thetiming
characteristics.
With National Instruments LabVIEW andhardware, we were able to
complete thisapplication in an extremely short period of
timewithout sacrificing functionality and reliability.The rapid
prototyping capability of LabVIEWenabled Roush engineers to provide
immensecost and time savings to the customer. ■
For more information, contactJohn NiezgoskiRoush Industries,
Inc.Tel: (734) 779-7494E-Mail: [email protected]
© 2002 National Instruments Corporation. All rights reserved.
Product and company names listed are trademarks or trade names of
their respective companies.
For worldwide contact information, please visit
ni.com/niglobal
ni.com/success (512) 683-0100 • Fax (512) 683-9300 •
[email protected]
The rapid prototyping capability of LabVIEWenabled Roush
engineers to provide immensecost and time savings to the
customer.
Aquire andAverage Data
Pattern Matchto Determine
Engine Position
Gross FailureAnalysis
(Missing Pulse)
CalculateExact Timing
EnginePASS
FAIL — OutsideAcceptable Window
FAIL — IncorrectGear Installed
A flow chart representing the transparent software
algorithm.
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