Controller Development For Electric Power Steering System With PMSM

Compared with other power steering systems, EPS has many advantages, such as energy saving, environmental friendly, easily arranging. Permanent Magnet Synchronous Motor (PMSM) has a simple structure, high power density. Unlike other traditional direct current motor, PMSM has no brush, which obviously decreases working noise and prolong longevity. AS a result, EPS with PMSM has become a new research hotspot of automotive power steering system.In this article, Firstly, the mathematic model of PMSM and steering system is built. Based on the mathematic model, two layers control strategy of EPS is proposed. The top layer is EPS control strategy which includes assist control, return control and damping control; the bottom layer is PMSM control strategy based on field oriented control method (FOC). The upper EPS control strategy calculates the target current, and the bottom layer control strategy traces the former target current with PID controller.Then, according to EPS sensors and actuator, EPS control unit hardware is designed, using STM32F103ZET6as the core controller and choosing A3946as the MOFET pre-drive integral circuit. Besides, there are still some other modules in the EPS control unit such as sensors interface circuit, CAN interface, voltage detecting circuit, temperature detecting circuit and fault diagnosis circuit.Based on the EPS control unit hardware, EPS software is developed in u Vision4; the software consists of main program, steering torque and steering angle acquisition program, PMSM drive program, and fault diagnosis program, all of which use hardware timer to control program cycle.Finally, in order to verify the effectivity of the self-designed control system, PMSM bench test, EPS controller bench test and EPS controller vehicle test are carried out. Test results show that self-designed EPS controller can meet vehicle power steering requirements.