Study On Drive Control Strategy For Four-Wheel Independent Drive In-Wheel Motors Electric Vehicle

The Car has become from a model of transport to a symbolic cultural product on behalf of the innovation and technology.Especially in the current,the traffic safety problems,global energy scarcity and pollution problems spread all over the world.To meet the social responsibility of energy conservation environmental protection,every country is turning to the development of key technology for electric vehicle.The four-wheel independent drive control technology based on in-wheel motors is one of the most promising means in electric vehicle.Four-wheel independent drive controlled by X-by-wire technology can conduct steering ? braking and driving together,which lightening the control pressure and having high-precision performance and fast real-time response.It is the optimal shortcut of developing intelligent driving control and achieving dynamic control.In this paper,with four-wheel independent driving car based on in-wheel motors as the research object,simulation platform is developed,the electronic differential control strategy and the anti-skid control strategy are carried out and the vehicle control system scheme designed is used for testing.Firstly,according to modeling requirements of the four-wheel independent driving car based on in-wheel motors,we make the hypothesis of this model based on the modular modeling idea,and build a 15 DOF(degrees of freedom)model of 4WS electric vehicle for simulation,four wheel steering has 4-DOF,there are 4-DOF vertically in the wheels and vehicle body has 6-DOF,and front wheel steering has1-DOF.Including 4-DOF in four wheel steering,4-DOF vertically in the wheels,6-DOF in vehicle body and 1-DOF in front wheel steering.Secondly,aiming at the control strategy,the electrical parameters of the brushless DC motor are determined according to the requirements of vehicle performance dynamically,and the torque is explored.So the double loop PID speed control principle is derivated,and the electronic differential control strategy is proposed.However the impact of wheel slip factors is not taken into consideration of the electronic differential control strategy.So a fuzzy-PID controller is designed based on the impact of wheel slip factors.The fuzzy-PID controller keeps the actual slip rate steadily at the optimal slip ratios to achieve acceleration slip regulation effectively.Besides,when it comes to the development of controller,the selection andfunction of each part of controller system was analyzed according to the designed general plan of the controller system on 4WS electric vehicle.What is more,the vehicle controller and the basic motor drive controller were designed.Then,the design principles,function and realization procedure of software and hardware on the controller were introduced.After that,the simulated analysis of controller system was conducted.Through the simulation analysis by Carsim,we could see the vehicles dynamic performance was precisely described by the model,so the accuracy of the model of the 4WS electric vehicle is verified.On this simulation platform,the rationalization of fuzzy-PID control strategy and the electronic differential control strategy were conducted.The simulation result verified the effectiveness of fuzzy-PID control strategy and the electronic differential control strategy.Finally,the experiment on designed experimental prototype was conducted at the condition of straight-line running and turning,which verified the good response to the instructions of steering and driving.Besides,the feasibility of electronic differential control strategy was verified.