Cessna rapidly developed HIL tests for the prototype’s brake control system using Simulink®, Simulink Coder™, and Simulink Real-Time™.
Two Cessna engineers developed a model of the prototype in Simulink. The model incorporated lift, drag, engine thrust, and the trailing link main landing gear. It also included parameters to simulate runway conditions—including water, snow, or ice on asphalt and grooved runways—as well as different brake wear conditions. The engineers then used Simulink Coder to automatically generate ANSI C code from the Simulink model.
With Simulink Real-Time they ran the code and executed the model in real time on commercial off-the-shelf hardware connected to the aircraft’s brake control system.
Using this testing environment, the engineers simulated hundreds of landings under different conditions until they could replicate the symptom consistently. During simulations, the team gathered data on 20 different parameters at a sample rate of 2000 Hz. With each real-time test lasting more than 20 seconds, more than a gigabyte of data was produced for each run.
Cessna used MATLAB® to analyze the test data, plot various signal relationships, and ultimately, to identify the cause of the brake control issue: a dead band in the brake controller.
After finding the dead band, the team developed a design that addressed the issue using additional parameters available from the aircraft controls and systems, and both the test pilots and the engineers were pleased with the new performance. Being able to find intermittent issues quickly and cheaply gives Cessna a competitive edge in a market that demands perfection.
Since this prototype antiskid project, Cessna has expanded its use of HIL testing, and now uses MathWorks tools to test all new brake control systems.