Research On Return-to-center Of Electric Power Steering System

Electric power steering system (EPS) is superior to conventional hydraulic powersteering in many respects: more useful functions, less power consumption, easierinstallation, no maintenance, and enhanced steering comfort.. Control strategy is one ofthe key factors and also core technology of EPS system. It is important to design an EPScontroller and developing an return-to-center control strategy in order to achievereturn-to-center accuracy under different condition and prevent cars from deficiency andovershoot phenomenon in return.Through changing traditional low speed EPS’s mechanical structure, designingcontroller electric circuit, making the power assisted and return-to-center control strategyand bench testing, this paper researched on the return-to-center control of EPS. The maincontents of this paper can be summarized as follows: (1) The all speed range EPS’smechanical structure and controller electric circuit were designed, which included MCU,signal processing circuit, motor drive and protection circuit, and the signal processingcircuit was simulated and analyzed. (2) The power assisted curve and motor protectioncontrol strategy were designed, integral discrete PID control strategy of return-to-centerwas developed that based on the steering wheel angle error, and the condition toreturn-to-center was given. (3) The control software was designed on the platform ofFreescale Codewarrior, and power assisted and return-to-center characteristics were testedon the test bench, and the results show that power assisted performance meets therequirements, the return-to-center control can effectively depress overshoot and deficiency.