Steering Motor And Road Feeling Motor Coordinated Control In Steer-by-wire System

Steering-by-wire System(SBW)abandons the steering column between the steering wheel and the font wheel,and uses an electronic control system to control the front wheel for steering.Angular transmission ratio and force transmission ratio of system can be set freely.The system can realize active steering and improve steering performance.Road feeling motor and steering motor are important components of the steering system.Their performance directly affects the driver’s operating experience.Therefore,the design of coordinated controller is the key.Aiming at the deficiency of single motor control in steering-by-wire system,a dual motor coordinated control strategy is designed and the motor control algorithm is optimized.Based on the research of coordinated control of steer-by-wire system,the main research contents are as follows:Firstly,the mathematical models of front wheel motor and road feeling motor in steering system are introduced.The maximum torque required for steering is analyzed,and the sensors are selected and designed.The permanent magnet synchronous motor with small torque ripple and high power density is selected as the control object.Secondly,the ideal transmission ratio of the steering-by-wire system is analyzed.In view of the deficiency of ideal transmission ratio,the variable transmission ratio of the steering system is designed based on the constant yaw angle gain.And three kinds of force transmission ratio characteristics are analyzed and designed.The Electric Power Str force transmission ratio characteristics are selected to design the steering system.Aiming at the shortcomings of traditional sliding mode control and PID control,the optimal sliding mode algorithm is designed with optimal control and sliding mode control.The speed loop is the optimal sliding mode control,and the current loop is PI control.And verifies the stability and effectiveness of the controller.Aiming at the problem of dual-motor angle-torque coupling of the steer-by-wire system,a position-torque coordinated control strategy is proposed.On the basis of the speed control of the permanent magnet synchronous motor,the position loop is added to realize the following control for the front wheel angle;the control of the current loop realizes the torque control for the road feeling motor.The variable steer ratio is applied to the system to realize the coordinated control of the dual motor in steer-by-wire system.Then the steer-by-wire system can realize the characteristics of steering sensitivity at low speed and stable steering at high speed,and improves the stability of the steer-by-wire system.Finally,a coordinated controller for the steer-by-wire system was designed.The controller includes a gate drive circuit,a voltage current feedback circuit,a power module circuit,and a sensor acquisition circuit.On the basis of the hardware circuit,the C-language is used to design control program.The acquisition of the sensor information and the real-time control of the dual motor are realized by the interrupt program.Communication with controller by PC,the sensor information is collected,and the speed control performance of the motor is verified.