Study On The Control Strategy Of Independent Driving System With Four Motors Running On Straight Road

This paper researchs on driving torque distribution strategy of four in-wheel motor vehicle.Unlike traditional vehicle,the control torque of four in-wheel motor vehicles can be distributed independently without interference.When it is driven on bisectional road or low adhesion road,to regulate the torque of each wheel can improve the dynamic of the vehicle,but it can also worsen the stability of the vehicle.So under the condition of ensuring vehicle’s stability,how to exploit the forcing potential of vehicles is the key point of this paper.According to the research object of this paper,co-simulation models have been built for the four in-wheel motor vehicle.The co-simulation platform combines models of Carsim with Simulink models.The effects of stability and dynamic are analyzed when vehicle is driven on high adhesion road,low adhesion road and bisectional road.The simulation results show that the low adhesion road and bisectional road have a great influence on the performance of straight line driving.According to the problems mentioned above,control models of system have been built with typical double-layer control structure.Double-layer control structure includes upper control logic layer and lower control logic layer.Among them,the upper logic layer is responsible for slip ratio calculation,yaw moment control,speed tracking and optimal slip ratio control;lower control logic layer is responsible for torque distribution which is based on demand torque,adjusting yaw moment demand and antiskid torque exported by upper layer.Torque control strategy of vehicle with four in-wheel motors have been designed which is based on PID algorithm and sliding mode control algorithm.Analysis for conditions when vehicle is driven on typical straight line road,the simulation results showed that: when vehicle is driven on high-adhesion road,it is enough that four wheels are given the same torque;when vehicle is driven on joint road,the control strategy can remain the slip rates near the optimal ratio,so that it can enable vehicle’s stability and improve vehicle’s dynamic;when vehicle is driven on bisectional road,the control strategy can remain the slip rates near the optimal ratio,besides,through yaw moment adjustment,it can also enable vehicle’s stability and improve vehicle’s dynamic.Electric vehicle platform which is based on EV150 of BAIC with four in-wheel motors was built.The work of analyzing protocol was carried out.Upper computer based on Labview which was used for debugging,testing and information monitoring was developed Programming and debugging for the vehicle control unit were also carried out.Vehicle tests show that the electric vehicle platform can meet the demand of experimental research,so reliable experimental platform is provided for further vehicle verification.