Research On Coordination Control For EPS And ESP Of Vehicle Based On Tire Force Estimation

With the increasing demand for vehicle safety,reducing harm caused by traffic accidents,has become an important area in the study of modern cars.It is necessary to research on integration control system between Electronic Stability Program(ESP)and Electric Power Steering(EPS)in face of more and more rate of equipment.Aiming at the ESP and EPS system,this dissertation discusses the coupling effect and coordination control between them from the overall situation of the vehicle chassis.Firstly the dissertation reviews the development of ESP and the EPS system,introduces the basic structure and working principle,summarizes the research history and current situation of tire force estimation and the research on the returnablity control in EPS at home and abroad,and thus leads to the coordinatied control research between them.Tire force estimation is an important content in the design of the ESP control system.Through the analysis of single wheel model of vehicle,using kalman filter to estimate vehicle longitudinal force and adding the constraint equation for the lateral acceleration constraints realize the optimization of vehicle longitudinal force.On the basis of the analysis of nonlinear vehicle model,this dissertation proposes a lateral force estimation algorithm based on yawing moment,the lateral lateral force moment of the vehicle is calculated by using the Disturbance observer,and the lateral force of the front and rear tires are calculated by using the least square method.At the same time,the weight coefficient is introduced,and the lateral force of each tire is calculated based on the vertical load.Based on Matlab/Simulink and CarSim software,and tire lateral force estimation system is simulated.The accuracy and validity of the estimation algorithm are verified by simulation with another tire model formula.An in-depth analysis of the influence of ESP on the EPS assistant mode is analyzed based on the model of seven degrees of freedom vehicle.Utilizing to the non-linear sliding mode controller calculates reference value of stability control force for yaw motion and then carries out force dynamic allocation by way of adjusting distribution coefficient.Simultaneously,the self-aligning moment of vehicle wheels suffer serious losses in quasi-hazardous working conditions.Thus the work mode of EPS is modified by using active self-aligning moment compensation strategy.A negative feedback coefficient is introduced for the rate of change of the self-aligning moment to effectively prevent the returnablity overtone.The control system is simulated by Matlab/Simulink software to verify the feasibility of the control strategy.Considering the coupled dynamics between electric power steering(EPS)and electronic stability program(ESP),the high-order and nonlinear dynamic model is built based on a 7 DOF vehicle model.The self-aligning moment compensation of fuzzy adaptive PID controller of EPS is adopted and drawing into negative feedback of the change rate of power torque achieve damping control,sliding mode controller is used for ESP.Set up the upper coordination system in order to further improve the overall control performance of the vehicle controller.Through the game theory obtains the optimal Nash arbitration solution when overlap or conflict of function between subsystems,that is,the expected value of the control function indicator.When the control function of subsystem conflicts with the expected index,fuzzy control strategy is adopted to dynamically adjust the control target output weights of EPS and ESP based on the principle of function allocation to ensure the rational use of the control functions of the two systems and achieve the optimization of vehicle performance.Finally,Matlab/Simulink software is used to simulate the control system to verify the correctness and reliability of the control strategy.In order to further verify the effectiveness and reliability of the control strategies proposed in this dissertation,a hardware-in-the-loop experimental platform was built.Through the development of ESP and EPS control unit,make real vehicle experiment based on VBOX III under different conditions,to verify the control effect of coordination system.