 |
|
 |
|
 |
|
Warranty Lab Automotive Seat Test Stand For Johnson Controls, Inc
R&D/Lab Automation
Products Used:
LabVIEW 6.1
NI-DAQ 7.0
Measurement & Automation Explorer 3.0
5B Series 16-Channel Backplane
5B36
5B49
NI PCI-6527 Digital I/O board
CB-100
NI PCI-6014 Basic Multifunction I/O Board
The Challenge:
V I Engineering Inc. has developed a Power Seat Test System for Johnson Controls, Inc. The tests are performed on automobile seat tracks for warranty claims and engineering evaluation or analysis. Each test can be individually controlled to perform tests on a single seat.
The tests procedures involve directional travel of the seat track under its own power and the application of load to the track. Current and speed are observed for the directional tests. The load tests analyze the stability of the track, and the plotting of each individual seat's "Chuck." Chuck is defined as the instantaneous displacement in a seat back when force is applied. Riders feel "Chuck" against their back in a car seat when it gives a bit, but stops before full recline position is reached.
The Solution:
This complicated system has come together using NI hardware and software for I/O, Puritan Automation machining, State Electronics custom potentiometers and a Bimba air cylinder. The LabVIEW programming, by V I Engineering, created a user-friendly GUI for lab engineers to easily run numerous tests.
Abstract:
The Johnson controls seat tester use an air cylinder to apply force to the back of a seat gradually forward and reverse to plot the displacement vs. the force applied to a seat. This identifies 'chuck', or the amount of seat displacement that occurs when a small force is applied to the seatback. Minimizing these movements in the seat significantly improves rider comfortable. The software uses graphic data to calculate the chuck and presents data in four different spreadsheets based on sensor position. This system also runs two, four, and six direction seat power track tests. All tests tabulate data to an excel readable format for later use. The tests can be printed out at the test stand, or saved to .a jpg, file for later review.
Overview:
The main screen opens when the program is called. At the top is a menu that will allow the user to exit, print, or load previous tests. From this screen the user can begin testing on three versions of the speed of operation power track test and the stability test.
Cost effective
National Instruments 5B line provided a low cost, yet robust isolated signal conditioning option for the low channel count of this system. 5B allowed V I Engineering to choose signal conditioning on a per-channel basis. Thus the system has modules specifically designed for potentiometer input channels and varying voltage levels channels all on the same back plane.
Data
During a test, data is taken and saved into an excel readable format for convince. Pressing Print will print the screen and create a .jpg image of that screen.
Speed of Operation tests:
The 6, 4, or 2 Way tabs (Figure 1) allow the user complete viewing of the entire power track. The sections of the display are broken up into directional graphs with analysis of mean current and speed to the right. This lets the operator run all directions of the power track and see all the data on one page. The displacement controls at the bottom of this screen are used in the analysis to calculate the speed of the track since the distance traveled is not measured in this application. The system calculates the speed of the seat track and the average current required for appropriate movement.
Start Test
The Start Test button allows the user to begin the test sequence. When each test is started, the preset schedule begins. The 6 Way test moves the seat forward, vertical up and down, then rearward horizontal forward and back. The 4 Way test moves the seat vertical up and down, then horizontal forward and back. The 2 Way test moves the seat in a forward and reverse direction on the section of track selected. Each motor is driven in the selected direction until the Stall Current is reached, then proceeds with the next step in the test sequence. If a timeout of 30 seconds is reached, the test stops, assuming an error has occurred. Upon completion of the test cycle, the graphs are updated with the data streamed to file for better accuracy.
FFT analysis
The currents measured in these graphs may look simple, but represents very meaningful data. Using FFT functions available in LabVIEW, V I Engineering was able to display the particularities of a seat track to give JCI an important tool in understanding a host of failure conditions.
Stability Test:
The intent of the stability test is to gather information on the total deflection of various parts of the seat under the application of force and to observe any irregularities in deflection caused by track and frame during the smooth application of that force. The indicators at the side of the top graph (Figure 2) display the total displacement of each plot. The indicators for the bottom two graphs show the largest value of chuck as defined by Chuck rate and Chuck minimum Displacement.
Figure 2 - Stability tab
Chuck
The Chuck tab ( Figure 3) displays the relevant information for all instances of chuck found. As indicated earlier, chuck is the instantaneous displacement in a seat back when force is applied. The qualifiers of chuck are Chuck rate and Chuck minimum Displacement as previously mentioned. This is a more detailed format of the indicators next to the chuck plots on the Stability tab.
Start Test
The Start Test button allows the user to start the requested stability test. The test is selected by the ring control above the Start Test button. In response to the Start command the cylinder moves from the full forward start position, to full reverse, then back full forward again, at the completion of the test cycle the seat is brought to the no load position thus finishing the test. The afore mentioned test positions are defined by Load. The waveform is output to ramp through this pattern so that the test will be done at the requested Time value.
Complications in Finding Chuck
Using a hardware PID controller for the air cylinder added erroneous chuck to the test measurements. This was caused by the PID correcting for give in the seat back, and applying more force, then meeting resistance again and backing off. To account for this issue V I Engineering used manual pneumatic valves controlled by software timing to gradually apply pressure through the control of air input to the cylinder. This was accomplished with LabVIEW using V I Engineering's custom state machine.
|
|
| << Back to Automotive |
|
|
|