Control And Co-simulation Of Electric Power Steering System Without Torque Sensor

With the rapid development of the automotive industry, energy saving, safety andcomfort have become hot topics of the modern automotive technology. Electric PowerSteering (EPS) system has lots of advantages, such as simple structure, easy installationand maintenance, environmental protection, easy to control, etc. So EPS system hasquickly occupied the market, and become the future development direction of thevehicle power steering technology.The purpose of this paper is to study dynamic models, strategies, simulationmodelings and test methods of the sensorless EPS system with different velocities anddifferent road, which are important for the future theoretical research and EPS systemtest bench.The main contents can be divided into the following sections.(1) Considering the actual demand of the EPS system, the difference between thesystem resistance torque and steering wheel torque is the EPS system desired torque,which conbined with speed signal are the fuzzy controller input signals, and then get themodified dynamical characteristics. Together with return-to-center control stratrgy ofthe booster motor current loop PI control to achieve a loop control strategy of q-axlecurrent of the permanent magnet synchronous motor.(2) Establish state space model of EPS system, and design an unknown inputobserver to estimate the steering wheel torque signal, which makes the EPS systemachieve sensorless technology. Based on two degrees of freedom vehicle dynamicsmodel, the Brush tire model is introduced to EPS system, and then design an nonlinearobserver, with wheel slip angle and the road surface friction coefficient as two states, toestimate road conditions when vehicle is steering.(3) Considering the error of the motor q-axle current and the actual currentminimized as a function of the energy index system, and use linear quadratic optimalstate feedback controller to realize the EPS control system.(4) Using the basic parameters of a prototype car, a complete system is built inAMESim and MATLAB/Simulink software, system mechanical models of EPS arebuilt in AMESim, and completely control of the observer and the system are built inMATLAB/Simulink. Simulated respectively when the vehicle in V=0km/hsteering, inthe low adhesion road surface and high adhesion road steering of EPS system operation torque, the total torques, motor output torque and motor q-axle current curve. Verify thefeasibility and rationality of the electric power steering system in this study.