Design Of The Controller Of Electric Power Steering Based On Freescale

EPS(Electric Power Steering) is a mechatronic product which embodies the direction ofthe development of vehicle technology——"safety, energy saving and environmentalprotection". The system controller of EPS is a key part which would effect EPS performancesignificantly. Aiming at the1.6L economic car of Sagitar, this article develops the controllerfor its EPS system. The research of this article can be applied to engineering projects andpromote the development of EPS with self-owned intellectual property in a certain degree forChina.Based on the analysis of the principle and characteristics of EPS, a controller whichmainly contains a control unit that comprising the dual core MC9S12XS128chip produced byFreescale was developed. By analyzing the existing control strategies and its performances,the power characteristic curve of the Sagitar1.6L car is established and the Fuzzy-PID controlstrategy is adopted to design the software and hardware of the controller. In terms of thehardware,according to specific situation which EPS is used in and the characteristics of keycomponents,peripheral circuits including the torque signal processing circuit, speed signalprocessing circuit, power motor driving circuit, power supply system and with additionalanti-interference and isolation measures are designed. In terms of the software, in the basis ofsatisfying the requirement of system performance, modular design including the mainprogram, speed signal acquisition subroutine, A/D acquisition subprogram, Fuzzy-PID controlsubroutine, torque signal fault-tolerant processing subroutine and so on is adopted. In order todetect the real-time working condition, the host computer is developed based on the PS-LCD,which realizes the communication between the host computer and the controller, the onlinesetting of the system parameters and the real-time detection of the system condition.The performance test of the home-made controller was carried out on the physical EPStesting platform in the laboratory, the result shows the controller can meet the portability andtraceability requirement, it can improve the resolution of the steering system; the function offault tolerance and fault detection is contained as well; the host computer is operable andpractical.