Research On Test And Design Of Rack-type Electric Power Steering System

Steering system is one of the most important systems of the vehicle, and it affects the handling stability and running safety of the car. Owning to the advantages of energy saving, environmental protection and good performance, EPS becomes the trend in steering system development. At present, there is only the C-EPS in China, which works through the Brush DC Motor or the Brushless DC Motor, and this kind of product can only provide low and volatile torque. R-EPS can provide greater torque, but it is completely dependent on imports in China.For this phenomenon, the research target of this paper is to design one type of R-EPS applied to the Class-C. The progress in researching this project is introduced in this paper. At first, the development and the principle of EPS is described. Then a kind of new power-assisted characteristic curve is designed based on the classic one, and this kind of power-assisted characteristic curve is calculated by the steer wheel angle and the vehicle speed. The control strategy which contains the operating mode judgment, the assistance control, the return control and the damp control is analyzed. The strategy is tested using co-simulation of ADAMS and MATLAB. According to the requirements, the coreless permanent magnetic synchronous motor and the Ball Screw is selected to apply, also, the preproduction of the EPS sample is compl eted. Finally, The control strategy is compiled to C code in Code Warrior, and debugged by using the Free Master as the upper monitor. The performance of the EPS is tested on the test bench that is loaded by the pressure-spring, and some problem like running noise and vibration are solved.The finished Rack-type EPS allows the car steer with assistance, return and damp function stably when the car is travelling at low speeds.