The electric parking brake (EPB) developed by TRW Automotive, now ZF Friedrichshafen AG, offers many advantages over traditional parking brakes. By eliminating the need for a parking brake lever or pedal, the EPB provides greater flexibility in the vehicle’s interior design. The EPB’s onboard computer can be integrated with the vehicle’s stability control system. For example, it can be configured to release the brake when the vehicle accelerates, activate the brake when the driver’s door opens, and prevent the vehicle from rolling backward when starting from a stop.
Because the EPB is a critical part of the parking application, TRW had to test every operation and branch of the control software. TRW used MathWorks tools for Model-Based Design to model and simulate the control system of the IEC 61508–certified EPB. With Simulink Design Verifier™ TRW engineers automatically generated tests, an approach that helped the group achieve 100 percent coverage of their Simulink® and Stateflow® models.
“Simulink Design Verifier enabled us to bring the formal testing of our software in-house and verify our design in the first phases of development, when defects are easier and less costly to fix,” notes Christoph Hellwig, team lead at TRW.