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  Challenge:  
 
Developing a cost effective system, efficient and easy to use, to automate Tractor Speed Test Jig.
 
     
 

Challenges were:

 
 
Analog Data Acquisition in Very noisy environment  
 
Accurate PID action from Software  
     
  Solution offered:  
 
Tractor Speed Test Jig Data Acquisition and Control system is constructed using the LabVIEW and NI PXI/SCXI. In the software LabVIEW objects are created. These expose the controls and Indicators to the user for the configuration as per the test case requirement.
 
     
  Application:  
 

To design Software for “Tractor Speed Test Jig Data Acquisition and Control”. This will be modular in nature. The application will acquire data from two load cells connected to tractor rear wheels.

It also measures pulses from encoder and shows RPM on user screen. Depending upon the set speed and actual RPM, the PID action will be taken through software which will operate two hydraulic valves controlling the speed of tractor wheels. This will also have intuitive User interface with ability to generate test sequence, which will help user to perform test.

 
     
  NI Products help us to solve these Issues:  
 
PXI /SCXI 1052 combination chassis. + 1314 CB  
 
SCXI 1520 Strain gauge module  
PXI PCI 6289 Multifunction DAQ Card
PXI 8186 controller
LabVIEW 7.1
LabVIEW PID Toolkit
   
Channel Configuration:
SCXI 1520 – Ch 0 – LCLH
    SCXI 1520 – Ch 1 – LCRH  
    PXI 6289 – CH 0 – 0 to 2 V Analog output LH  
    PXI 6289 – CH 1 – 0 to 2 V Analog output RH  
 
PXI 6289 – Digital output for Emergency STOP  
 
PXI counter – He is supposed to tell channel and card to read pulses  
   
  Displays:  
 
Engine RPM – 0 to 2400 ( Card read 2 revolutions – 1 Pulse)  
  LH Axel RPM – 0 to 100 ( Card read 1 revolutions – 60 Pulse)
  RH Axel RPM – 0 to 100 ( Card read 1 revolutions – 60 Pulse)
Set point read from Test Data (torque)
Process Variable (Current read data from Strain Gauges)
  20 mV = 30.48 KN- m and 0mV = 0 KN – m
Emergency STOP indicator: Process variable > 1.15 * Set point
PID gain control
     
 
 
Process Description:
Test loading to be done in steps of 100 N-m, waiting for 5 seconds before each
  increase
PID to be set in such a way that during load ramping, P=1, I=0.008, D=0. And, once
 
stabilized (20 seconds after giving load as per set point), it shall be changed to P=1.2, I=0.003, D=0
Test Excel sheet contains: STEP#, TORQUE, DURATION (HOURS), GEAR SELECTED
Once each step is completed,
  (a) Load to be gradually brought to Zero (O/p from PXI Analog card to be made zero
    volts) ( 0.0500 V/sec)
(b) A blinking message should intimate the operator to change gears as per the step
  (say Please change gears to XX – XX should be read from corresponding excel sheet row
(c) Once the operator changes gears, he selects the respective button, after which
  demand shall be sent through analog o/p.
E-stop will to be excited by DIO, not Analog o/p. That needs to be triggered by two
  things:
  (a) If load varies by +15% of set point, after 20 seconds is elapsed from the time
 
demand is given (before that there could be some oscillations), or +150N-m torque (whichever is larger). But, the variation should last continuously for more than 5 seconds (intermittent peaks are tolerable).
  OR
(b) If the user presses E-stop button on the screen (if he sees some fire, close to the
  test stand). == 0 and 10 V Digital output.
All error signals will be captured and redirected to error log, not stopping the test.
 
Because we need to run the test continuously 24*7, and the test should not be stopped in between for frivolous reasons.
 
Power Down/E stops Action:
Store current test data in to file with steps, total duration, duration completed, Next power on / Start – read file and start from that.
 
Conclusion:
More than conventional system, this system made it possible to obtain the in real time operation with facility to perform analysis on the acquired data. Only NI platform made it possible for us with in record time of 1 week.
 
 
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