Electronic Differential System Of Four-wheel Independent Drive Electric Vehicles

Electrical Vehicle (EV) is an important trend of the vehicle in the world. It is involved in the vehicle, control of the motor and the technology of battery. More and more researching organization recognized the importance of EV. Some of them have already had their own production.Firstly, the thesis provides an overview of the latest research results of EV home and abroad, as well as steering system of vehicles and electrical steering system. Compared to the methods of steering, a plan of Electrical Differential (ED) is confirmed which is based on an EV driven by four in-wheel motors.The controller of the motor is the core technology of ED. The control principle and hardware design of the motor is explained. Two ways to control the motor are presents, one is single- polarity PWM, the other is double- polarity PWM. We compared the two ways in the area of the time of dead space, newborn energy, characteristic of power and control method. Furthermore, the speed of motor is calculated which is related to the duty cycle of PWM. The motor's dynamic equations and functions are analyzed and based on which the PID control method is presents.In addition, this paper introduces the design of ED. We cancel the redirection, the motor in the redirection and the bridge. The ED has five parts, steering wheel, sensors of displacement, CPU, the four in-wheel motors and the position sensors in the motor. The four wheels steering system is used in this paper. The speed of four wheels is calculated independently during the turning. The different work conditions are presented to design the control strategy of the four wheels steering system.Mechanism and electrical system are described in chapter 4. The weight, size and the highest speed of EV are explained.Lastly, the design is applied on an EV and the steering parameters is simulated. It is approved it runs steadily.