One of the most important requirements for anti-lock brakes is that they perform effectively under all road conditions including deep snow, ice, dry pavement, rough pavement and off-road. General Motors tests its anti-lock brake systems (ABS) under every possible driving condition. The ABS must produce the optimum combination of stability, steerability, and maximum deceleration. Therefore, testing methods for ABS’s must be powerful and versatile to meet these strict specifications.

On the GM test track, the vehicle is put through a number of predefined maneuvers such as turning while braking. During testing, instrumentation has to acquire, manipulate and display a variety of analog inputs from vehicle sensors measuring force, pressure, rpm and temperature. As a result, test methods must be versatile enough to handle mixed analog signals and ensure compliance with strict performance requirements.

Test engineers in the GM Truck Engineering group use an on-board 486 PC running Snap-Master. The new system offers a number of benefits over earlier data acquisition systems, the most useful being the real-time graphic display of data as it is collected. This feature has made it possible to spot and fix a problem before an entire test is run. For example, during a test a transducer cable came loose. By observing the screen display, the technician noticed it immediately and was able to halt the test instead of waiting to graph and plot the results before noticing the problem. Therefore, it is now possible to make sure factors such as brake-line pressures and rate of deceleration are correct before and during a test.

Having this versatile and immediate feedback was the primary reason GM engineers incorporated Snap-Master into their ABS testing. The new system makes it possible to perform more tests in less time and improves ABS performance.

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