Research On Power-assisted Control Algorithm Of Electric Power Steering Based On Hardware-in-the-loop Simulation Platform

With the development of modern automobile industry,vehicle maneuverability and comfort have become a major research.Electric power steering system is one of the chassis electronic control modules for steering assistance and vehicle stability.It is very valuable to study on electric power steering control system in theory and engineering.This paper proposed a control strategy considering road characteristics for column electric power steering system on small or medium-sized passenger cars.Firstly,based on the actual structure,this paper built the mechanical structure and motor model in the column electric steering system in Simulink.The input and output characteristics of the power steering system model were tested to ensure the accuracy of the model.Then the model can be the foundation for the control strategy.Secondly,in order to get the control variables for the control strategy,several observers were designed for the states(car speed and road friction coefficient)which cannot be estimated from the sensors.Then Simulink simulation was carried out to compare the theoretical value with the estimated value to verify the effectiveness of the observers.Thirdly,according to the requirements of the power steering system,the full control strategy for the power steering system was established,combined with the upper control and the lower PMSM torque control.The assistance control was based on driving requirements.The return control used steering angle and fuzzy control theory.A delay state machine control was proposed to ensure better switch.Aiming at the road state response,compensation strategies and low road friction coefficient road control were proposed.Vector control was used for PMSM control.Then the validity and rationality of the control method were verified.Finally,to verify the control strategy in actual hardware,hardware-in-the-loop system was built on NI PXI hardware platform.Through model and data interface in LabVIEW development environment and embedded code in STM32 control board,a number of different working conditions were tested to verify the control effect.