Studies On Control Technique Of Vehicle Power Steering System

The thesis rooting in the transverse item - research and manufacture of vehicle Electric Power Steering system (which is abbreviated into EPS) is to study power steering control technique for mini-car that is based on drive of rare earth permanent magnet DC motor.At the beginning of the dissertation, the basic elements and the operating principle of EPS are introduced. From the reference of concerned technical document, the paper establishes the transform function of the whole system by predigesting every element of the system and analyzing force stress of the system. Then the paper makes a choice of the type of every element against the system's traits and studies the main power converter of H-bridge that realizes forward/inverse rotation of DC motor, after that, the restricted monopole control mode is adopted to assure the motor reversing its rotation reliability. Afterward, according to the request of the system designing, the thesis explores the target assisting characteristic equations and puts forward a scheme basing on the high-performance microcontroller P87C591.Meanwhile, a hardware current-loop circuit is designed to regulate the output torque of the motor by utilizing the abundant hardware of P87C591 association with PWM technique. The article also brings two control strategies in the steering that are assisting mode and damp mode for enhancement of the steering control stabilization. At last, the thesis details hardware design and software design.Finally results of laboratory experiments and road experiments show that the system designed has good steering characteristic and meets the anticipated performance index.