Research Of Control Strategy And Development Of Controller Of The Electric Power Steering System For Car

With the development of economy and the automobile electronic technology, people putforward higher requirements on the safety, steering stability, driving comfort and energy-savingenvironmental protection. The Electric Power Steering (EPS) system has been more and moreget the favour of people and very suitable for assembly on the car because of its the advantagesof energy-saving, environmental protection, adjustable assist characteristics, simple assembly,and small space. Therefore, the EPS system has great application field and market developmentspace. At present, the EPS system in China is still in the growth stage, most of the coretechnology by foreign monopoly, the control strategy and reliability of the controller needs to beimproved. Therefore, this article has carried on the research and test of control stategy andcontroller development for EPS system.By studying the structure and work principle of EPS system, the parameters and structure ofthe key components are matched, which consists of mechanical steering, assist motor, retardingmechanism and torque sensor, etc. The overall control strategy of EPS system is designed, whichincludes two layers. According to the steering wheel torque and car speed signals, the top layerstrategy calculates the target current of assist motor. Bottom layer strategy controls the actualcurrent or torque of assist motor. The assist characteristic curve of suitable for car is designed.Use the PID current controller to tack target current, the control process of EPS system hasobtained the good dynamic effect and robustness by adjusting the proportion, differential andintegral three parameters of PID controller. The simulation model of EPS system based onMatlab/Simulink is built, which consists of mechanical steering system model, motor model andcontroller model, etc. The control strategy is simulated by simulation model to verify theeffectiveness. In fully aware of the high speed and high precision data acquisition, systemprotection, fault processing and anti-interference measures, on the this basis, the EPS systemcontroller hardware circuit is developed by using Freescale MC56F8346chip, which consists oflogic circuit and power circuit. According to the preliminary design of control strategy, the EPSsystem control program is designed based on the CodeWarrior IDE8.3Freescale software,which consists of main program, interrupt program assist control program, etc. In order toimprove the performance of system, software filtering is widely used.In order to verify the effectiveness of the control strategy and the performance of thecontroller, the development of controller is tested on the auto electric power steering systemcomprehensive performance test bench, which consists of no-load torque test, assistcharacteristics test, input-output torque test, etc. Through debugging and improvement, The test results show that the controller of development has obtained good control effect in the assistcontrol and power consumption.