Simulating Electric Power Steering
Systems at Electric Power Level

Task

Electric Power Steering (EPS) systems support the driver during steering. A torque sensor measures the steering movement and sends this data to the EPS ECU, which causes the EPS electric motor to support and enforce the movement. As the EPS electric motor acts directly on the steering rod, the vehicle can be steered even without the driver's interaction. This enables fully automated parking as well as interaction with the electronic stability control (ESC) to support the driver.

Challenge

The signals of ECUs for EPS often cannot be accessed at signal level. HIL simulation is therefore performed at power level. The ECUs have to be connected to the real motor either at mechanical level or by simulation at electric power level.
The electric power level requires real currents and a simulation for the motor. This solution is quite flexible and can be adapted quickly, for example to simulate different motor types. The simulation can also be combined with HIL simulation for an ESP.

Solution

In both cases the dSPACE HIL Simulator is equipped with a DS6601 or DS6602 FPGA Base Board. Electronic load modules provide the real current for simulation at electric power level. dSPACE Automotive Simulation Models for vehicle dynamics are used for simulating the actual physical vehicle characteristics, including the steering system for the EPS and the brake hydraulics for the ESP.