Research On Multi Motor Coordinated Control Strategy Of 4WID/S All Electric Vehicle Steer By Wire

Four,wheel independent traction/steering(4WID/S)all electric vehicle steering system adopts wire control technology,and uses CAN bus to transmil the steering wheel angle control signal to the vehicle controller,which solves the problem that the steering characteristics of the traditional steering system need to be adjusted at all times,so as to ensure the stabiiity of vehicle steering,improve and reduce the driver’s busy degree of operation.The steering executive part mainly includes four independent sfeering motors and rack and pinion.The multi-mode steering condition of the vehicle needs the coordination of four steering motors.Based on the coordinated performance and synchronous performance control of multi motcor steering by wire of 4WID/S all electric vehicle,and improving the performance of steering motor,this paper studies the optimization design of variable angle transmission ratio.The main work is divided into the following four parts.Firstly,through the investigation oF literature and materials in recent 5 to 10 years,we can understand the research progress and status quo of University and vehicle enterprises on steer by wire electric vehicles,mainly including the improvement of vehicle steering performance in the aspects of variable angle transmission ratio,vehicle handling stability and multi motor coordinated control,and briefly describe the research significance and content of the subject;considering the two degrees of freedom of lateral and yaw,the dynamic vehicle model is built,and the response curves of yaw and lateral acceleraliort unnder steering condition are compared with CarSim simulation software to prove its rationality,which lays the foundation for the research.Second the angle ratio between steering wheel and wheel of steer by wire vehicle can be designed by human,which can take into account the driving habits of drivers and the steering characteristics of low-speed and high-speed steering.However,the ideal angle ratio curve is not differentiable at the turning point of vehicle speed,which leads to the impact on the angular speed of steering motor and reduces the performance of steering motor.Based on this,the improved T-function fitting method is used to optimize the design,so that it can make a smooth transition at the turning point of vehicle speed,so as to improve the performance of steering motor.Thirdly,to realize multiple steering modes of vehicles,four independent steering motors are needed to coordinate to realize the driver’s steering intention.Based on the investigation in the first part,the existing multi motor control is analyzed,and the adjacent cross coupling multi motor structure is selected.Firstly,the speed simulation models of four motors are built to analyze the existence of large synchronization error when they are disturbed,and the number of synchronous compensators increases exponentially with the increase of the number of motors,The difference between the output speed of each motor and the average speed is used to feed back the load disturbance in real time,and the difference between the output speed of its adjacent motor is used to compensate the motor synchronization,so as to reduce the synchronization error between motors.Secondly,the position simulation models of four motors are built to verify the motor position tracking performance under the actual vehicle steering conditions,so as to ensure that the vehicle steering angle requirements can be accurately achieved.Fourthly,on the existing 4WID/S all electric vehicle experimental platform,the angle sensor is installed at the wheel to obtain the steering angle in real time.The DSP chip of TMS320F28335 is used as the central processor,and the vehicle control signal and vehicle status information are transmitted through CAN bus.The influence of the improved steering multi motor synchronous control structure and variable angle transmission ratio optimization on the performance of the steering motor is verified.