Modern cars contain more and more electronic components. An especially important roll is played by various safety systems, such as ABS (Anti-Lock Braking System), traction control, and ESP (electronic stability program) in newer vehicles. Wheel speed sensors are key components of these systems. They determine the speed of the car's wheels and send signals to the ESP control unit. Usually, the sensor operates on a magnetic principle (Hall effect or magnetoresistance). The sensor detects the rotation of a special encoder ring and calculates wheel speed.
The Quality Assurance Department of Audi Hungaria (Győr, Hungary) has two testing rigs set up in their electronics laboratory: one for each of the models built in Győr, namely the A3 and the TT. These systems contain every single electronic component of the car. The testing rigs are used for simulating the car's behaviour under laboratory conditions and for fault reproduction. In order to simulate the rotating motion of the vehicle's wheels, a mechanism containing an electro-motor was constructed for the A3 rig. The wheel speed sensors are fixed to this constructed simulator in order to mimic rotating wheels. The simulated speed can be adjusted by modifying the motor's frequency of rotation.
For the TT version, the idea of a signal-generating simulator emerged. The simulator's task is to recreate the signals which are sent from the wheel sensors to the ESP control unit. During my thesis, I designed and created such a device. It replaces the wheel speed sensors and is compatible with the above-mentioned testing rig. The basis of the device is a microcontroller development board, and its goal is simulating the rotational motion of wheels on the testing system for the TT. During the development, I set up several measurements in order to determine the waveforms of the sensors. Subsequently, I designed the circuit, wrote the program for the microcontroller and finally connected the simulator to the testing rig.
The aims of this paper are to summarise relevant literature, to introduce the testing rig system, and to present the development of the simulator.