| The steer-by-wire system plays an important role in the future of unmanned driving.It has the advantages of flexible layout,variable transmission ratio,and personalized custom steering wheel feel.This paper focuses on the force characteristics of the line-controlled steering,including the steering motor control,front wheel load observation,steering wheel feedback force simulation three opposites.The surface model of the permanent magnet synchronous motor is used to analyze the mathematical model and control principle of the motor.The vector control method and the SVPWM method are used to control the motor output.The bidirectional control architecture of the SBW system is determined as the position control-force feedback scheme.On this basis,the load is analyzed.Observing the requirements of motor control;in the current follow-up of the motor,due to the system lag factor,the traditional PI control method is poor in control effect,so the dynamic three-step method is used to optimize the current following effect,and the high-quality motor output signal is obtained;In terms of control,the feedforward feedback integrated control method is used to achieve fast and accurate position control;in addition,the signal is disturbed and filtered and suppressed accordingly;finally,the line control steering position control is completed,and the load observation is provided with high quality signal input.The acquisition of the front wheel load is a difficult part of the research on the characteristics of the wire steering steering force.The method of load acquisition is analyzed and compared.In order to obtain the real road load information to ensure driving safety,this paper adopts the method of constructing the load observer.Pulling the pressure sensor to obtain the real road load information;then constructing the disturbance observer,and performing friction compensation,inertia compensation,Kalman filtering and other measures to obtain the observation signal that is attached to the sensor signal;the experimental results show that the load observer The signal can reflect real road load information.Steering wheel feedback force reconfiguration is the core part of the design of the wire-steering steering force.This paper reconstructs the feedback force of the steering wheelbased on the observed load signal.Based on this,the design of the feedback force simulation strategy and the composition of the steering wheel torque are carried out.Including:curve-assisted force,reflexive feedback force,in addition to the compensation strategy of the steering system,namely friction compensation,damping compensation,inertia compensation and mechanical compensation;this scheme simulates the control principle of EPS,with a clear sense of road,with the speed of the vehicle changes significantly,and the control parameters are easy to calibrate.The active return control strategy of speed control is designed,which can accurately judge the positive working condition,and the return control is fast and accurate,and the torque is smoothly switched back.Based on the Carsim-Labview RT-based wire-controlled steering hardware-in-the-loop experimental platform,the experimental research on the above strategies was carried out.The experimental results show that: 1)The current control of the motor has fast follow-up speed and small signal noise;the position control response speed of the motor is fast,the angle following is accurate,the signal noise is small,and the hysteresis is small.2)The load observation signal is closely attached to the tension pressure sensor signal,the observation signal is accurate and reliable,and the observation signal changes with the road surface adhesion coefficient.3)The steering wheel feedback force simulation strategy can provide the driver with a sense of force close to the EPS;4)The active return control strategy is adopted,and the return mode is designed to ensure the steering wheel is quickly and accurately corrected. |
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