Research And Realization Of Control Strategy For Pinion-Electric Power Steering System

Electric power steering (EPS) system is the inevitable trend of steering system. The study of EPS which involves the field of sensors, micro-electronics control, computer control, embedded system design, electric driving, nonlinear control theory, intelligent control, automobile project and mechanical design represents the future ideas for automobile design. Pinion-EPS (P-EPS) which can be used in middle class car is studied in this paper. The experiment on experimentation platform which is based on modeling study and ECU design of P-EPS is carried out.The physical model of P-EPS system was established with AMESim which is an integrated modeling environment for hydraulic and mechanics. The correctness of the model was tested. The static and dynamic behavior of P-EPS which is the base of control strategy was studied.Mature control strategy for P-EPS was needed to meet the comfort, reliability and safety request of steering system. One control strategy which includes three controls and two compensations were brought forward in this paper. Assist control provides steering moment for driver; active returning control increases returning speed, the motor can afford active return moment for the system because of the new sensor used in P-EPS system; damping control strengthen stability of the car. Two compensations which include inertia compensation and friction compensation remedy low responding speed of the system caused by motor inertia and system friction.ECU is the core of P-EPS system. DSP56F8323 which was produced by Motorola was adopted as the processor of ECU. The hardware design including signal collecting and processing circuit, motor drive circuit and protecting circuit was introduced. The software design was based on the tools of CodeWarriro IDE and PE which were afforded by Metrowerks. The program flow chart was also given.Finally, the experimentation platform for P-EPS was established. The assist character, returning character and responding character was tested on the experimentation platform.