The Phaeton Laboratory Car

HIL simulation of active suspension LF/CDC, ESP/ABS and active cruise control (ACC)

(Summary of article published in ATZ, Extra Issue Phaeton, Issue July 2002 - Publication No. V115)

The Volkswagen Phaeton, VW's first luxury class offering, includes numerous intelligent, convenience and active safety systems designed to give its occupants the best driving experience modern technology can provide. With over 60 electronic control units acting together to optimize things such as handling and performance, functional testing was imperative to assure proper behavior of the entire in-vehicle controller network under all conceivable conditions. To minimize the development and testing effort, a laboratory car, complete with the actual controllers and controller network, was equipped with a hardware-in-the-loop simulation system and used to exhaustively test the system. The HIL environment selected by VW was a collaboration between Carts Real Time Solutions GmbH and IPG Automotive.

HIL has been used for electronic control units testing in various forms at VW for over twenty years. Initially the testing was done for individual controllers. Today however, because of the complexity of modern luxury class vehicle systems and the overlap that takes place between control units of these systems, a more robust approach for electronic control testing became necessary. Entire vehicle networks are now being integrated as hardware-in-the-loop and tested in unison. Any controller that is not available can be simulated by passing the appropriate messages over the CAN bus.

Vehicle dynamics, which are necessary for testing active safety systems such as ESP/ABS/TCS, are simulated as mathematical computer models and provide the electronic control units with the sensor readings required by the internal control algorithms. In closed-loop simulation a driver model is also included which takes the vehicle model's state and output values as inputs and drives the vehicle in a predefined way along a virtual road.

All the simulation is intended to make the electronic control units believe that they are in a real car. Because the signals that are generated by simulation are the same that would be sent by real vehicle sensors, which measure things like speed, acceleration, yaw and steering wheel angle, the electronic control units can be tested as they would be in a real car, driven by a real person, on a real test track. However, since testing the electronic control units is all done in the laboratory it can be done in a much more controlled and systematic, as well as safe and cost effective, way. Thus with simulation, testing the electronic control units becomes faster and cheaper, expediting development times and lowering project costs.

The VW lab car was comprised of the standard Phaeton body, all the electronic control units and the wiring harnesses and cable trees that would be used when produced. This ensured that the same electrical ground was used in testing the electronic control units as would be used in the actual vehicle so that early line problems could be detected and corrected. The engine, gearbox, chassis and brake system components were simulated with vehicle models by IPG's CarMaker. Some of the real sensors and actuators were used and fed through the production plugs to the electronic control units. Others were simulated. All simulation models were executed in real-time to give the correct time latency seen by the electronic control units.