Research And Development Of The Automobile Electric Power Assisted Steering System

The electric power assisted steering system(EPAS)may be the potential trend of the automobile power steering, and it is the technical breakthrough on the automobile steering technology next to the hydraulic power steering system. EPAS has many advantages over the past steering system, so that it becomes the hottest topic in the research field of automobile steering in recent years. However, up to now domestic automobile industry still relies on EPAS import. EPAS has been listed in as one of the main research topics of current national developing plan.The electric power assisted steering system is the typical mechatronics system, and it blends many disciplines. Such as mechanical design, automobile theory, electronics, computer science, control technology, sensor technology, and motor technology. A lot of effort was involved in when the research to be started.Based on the analysis of the function requirements of the system, the main components of the system were studied and tested including driving motor, electromagnetic clutch, torque sensor, vehicle speed sensor, and reducer.It is obvious the key task to develop an EPAS is its control module. By many times of try and error tests, the research has get significant progress. The control hardware includes a center control module, a motor control module, a sensor signals process module, a clutch control module, and a diagnosing module. A prototype circuit board has been made, and all modules of the control system have been debugged with control software in the lab. A lot of valuable testing data were obtained that will be helpful for the next outside driving test.Meanwhile, the control software was developed with its hardware testing. Some control strategies and the recommended flowchart to get a stable steering under various conditions were presented and discussed in the paper. The research shows that EPAS has flexible control power and huge application prospect.Based on the discussion of control strategy of EPAS, a mathematic model of the system is put forward and simulated with the concept of combination control of fuzzy logic and PID, which has built a theory foundation for future research of EPAS.The phase research result has been transferred to a cooperation enterprise to be as the initial test model for his new EPAS product.This dissertation may be a bold attempt of the development of the electric power steering system in our country, and some achievements obtained may be valuable reference for developing of domestic electric power steering system.