Research Of Stability On The Torque Allocation Of Independent Driving Electric Vehicles

Electric vehicle has become a trend of replacing traditional vehicle gradually, with environmental issues and energy issues being prominent increasingly. Compared with the traditional internal combustion engine vehicle and centralized drive electric vehicle, independent in-wheel motor driving electric vehicle has some advantages including a more simple structure, manipulated more easily, response more sensitive, independently controllable power, so independent drive electric vehicle is characteristic direction of the electric car development. As people’s requirements of vehicle active safety continue to increase, it’s one of the main directions of stability studies to improve independent drive electric vehicle. This paper studies as independent in-wheel motor driving electric vehicle, studies vehicle torque allocation control as the breakthrough point and the breach, and do the specific research of vehicle stability in the low attachment under limit conditions. The main contents are as follows:Analysis of the significance and the research status of torque allocation of independent driving electric vehicle. Research the structure characteristics and the key technologies. And make a brief analysis of the state of development at home and abroad in recent years. Finally make a classification summary of the research status of torque allocation, and lead to a research paper.In this paper, establish vehicle dynamics model by SIMULINK platform. Establishing vehicle math model of nine degree of freedom including longitudinal, lateral, yaw, roll, pitch, and rotate of four wheels, based on the corresponding reasonable simplification model of the vehicle and the wheel tires. The model built focuses on the control part simulation of the part of the vehicle dynamics, the part of tyre mechanical characteristics. In addition, build the brake model and the tire model. And through the corresponding simulation, it can be drawn that the model built is reasonable in this paper.Analysis of the whole control system of independent driving electric vehicle. To study the stability of the vehicle, study the reference model, namely single track model. According to the reference model, obtaining the yaw rate and sideslip angle, and identified as control variables. Then forcus on the torque allocation control strategy and control algorithm. In the driving force control allocation, this paper proposes three kinds of allocation modes in order to ensure the travel path and driving attitude to be the best. There are two layers in specific control process including the upper layer and the lower layer. On the upper control, there are two controllers, one is the speed controller that can calculate the total required torque, and the other is the ideal yaw moment controller that can control the yaw moment generated by the yaw rate and sideslip angle. In the second controller, the specific control method is to adopt PID control based on BP neural network. On the lower layer, it is the target to control slip rate by dimensional fuzzy control, after this kind of control, the desired torque of four wheels are detained. And at last, design control strategy of combined driving force control to the brake control. The desired torque of four wheels are detainedSimulation of the built control system in this paper. The simulation condition is in the low attachment under limit conditions, and input a step steering angle. Made the simulation to verify crrectness of the torque allocation control strategy. The simulation result is that the vehicle can keep stable driving by control allocation strategy designed from this paper.In the summary, from the simulation results, in the low attachment under limit conditions, the vehicle’s safety and stability can be assured by the the torque allocation control strategies designed from the paper. The control startegies can become theory reference of active safety design, and they also have an important guiding significance for the independent drive electric vehicle.