Study On Control Strategy And Test Of Electric Power Steering Control System

Electric power steering system, for its easy handling characteristics,better steering feel, compact, easy assembly, high efficiency,and low power consumption, become the focus of a new power steering technology. With the electric power steering system improving, EPS will replace the traditional steering technology, become the dominant force of power steering technology in the new era.This thesis aims to study the control strategy and test ways of the column-type EPS system, as follows:First,the research background,system structure,working principle and the development situation at home and abroad of EPS are introduced.Second, the EPS system functional requirements is analysed to design the EPS system control strategy. The three assist control methods,digital PID control and parameter tuning,and three control methods of EPS motor are described.For traditional EPS system bring the car back to the positive performance degradation, back to the positive/damping control are added to the EPS system to solve this problem.The return curve,PID return control methods based on steering angle and rotation speed are designed and presented. Characteristics of the input signal in the process of steering and return are comparatively analysed to find accurately determine conditions for entering the control mode.Again, input and output signals and their characteristics in the EPS system is introduced.The EPS controller has been designed, Which mainly include the torque sensor signal acquisition and processing, angle sensor signal acquisition based on CAN bus,vehicle speed acquisition, motor drive,PWM control and digital filtering.Then, in order to facilitate debugging, verify the controller's reliability and validity of the control strategy, a resistance simulation test bench is designed which simulate the road resistance with a DC. This paper designed the simulation curve and completed the resistance load on the test bench. Real-time data acquisition system based on LabVIEW is developed. Reference to "electric power steering device and test methods of draft technical conditions",the bench tests have been conducted, including:input and output characteristics test, power current characteristic test, return performance testing. Though real-time display and record data,this paper completes the analysis of EPS system.Finally, The independent research EPS controller is installed on the real car,refer to GB/T 6323-1994 "vehicle handling and stability test methods", to conduct real vehicle tests, including:In-situ test steering, Steering light test, Turn back to the positive performance tests. The results show that the EPS controller can increase portability of steering and back to the positive performance, meet the design requirements.In this paper, through the test in test bench and real vehicle, the feasible of electric power steering control strategy has been verified and the test result is very good.It has important theoretical and practical significance on the electric power steering system research,design and development.