The Simulation And Controller Design Of The Electric Power Steering System

The automobile turning system has turned from simple machinery system, mechanical hydraulic pressure power system, electronic controlled hydraulic pressure power system to electric power steering system, which is energy-conservation even more and better performance. Electric power steering system adds sensor device, electron controlled device and turning assisting power device based on the traditional machinery steering system. It adopts electromotion implemental machine to offer appropriate assisting power under different driving condition. It adopts the motor to offer assisting power directly, the size of assisting power and the directions are controlled by the automatically controller. EPS has the advantage of smaller volume, lighter weight, simpler structure, easier installation and maintenance, lower consumption, better environmental protection. Additionally, it possesses high-level performance such as ensuring different steering feel owing to adjusting steering assisting force according to vehicle speed, which enables it fits for many kinds of vehicle such as car, truck etc. It is one of the technology of research focus and front of the technical development of present automobile.In this paper, the configuration of the electric power steering system is predigested, and dynamic analysis of the parts of the system are done. Severalindices such as steering sensitivity and steering feel to evaluate the handling performance of the combination system including EPS system and vehicle handling system were put forward and their expressions were deduced after the integral analysis of vehicle's handling dynamics and EPS' dynamics. Having investigated the effects of several factors such as rotational inertia of the motor, gear ratio of the assisting mechanisms, torque sensor stiffness and assist gain. The influence of the controlling parameters to the system performance is also analyzed based on the different controlling strategy.In this paper, based on the mechanical structure of the electric power steering, the aim is to design control circuit of the whole system. The microprocessor and the surround circuit of the system, the motor drive and the protect circuit, the input signals disposal circuit such as current and torque sensor, the clutch and the display circuit and the power supply circuit are designed. The flow chart of main procedure and the subprogram are designed and the code is achieved to use C language as exploitation tool. The control strategy and software are completed which are suitable for the hardware, to provide foundation and reference for the EPS system's perfection.In the process of writing this thesis, first, based on the theory of the DC motor, controller and sensors, the control circuit has been designed. The reliability of the circuit has been examined through the imitation and check to the circuit board. Later, the control strategy and the software has been designed, the primary destination is to get the assisting table and PID control of the current. Finally, the examination on the platform has been carried.