Research On Drive Control Of Dual Permanent Magnet In-wheel Motors For Electric Vehicles

The in-wheel motor drive system,as a drive system for the distributed drive electric vehicle(EV),has attracted extensive attention from researchers at home and abroad,due to its unique structural and control characteristics.The EV with dual in-wheel motors is directly driven by two in-wheel motors.The torque and speed of each motor is independently controllable,and the control of vehicle driving force is flexible.To give full play to the performance advantages of dual in-wheel motors,it is necessary to research the control strategy of in-wheel motors and the control strategy of dual motors.Therefore,this paper proposes maximum torque per ampere(MTPA)direct torque control(DTC)for permanent magnet in-wheel motors,and studies the coordinated control of dual in-wheel motors.This thesis introduces the mathematical model of permanent magnet synchronous motor(PMSM)in different coordinate systems and the direct torque control.Then the difference between the MTPA in vector control and direct torque control is compared and analyzed.On the basis of space vector modulation direct torque control(SVM-DTC),an MTPA strategy based on active flux is proposed.Compared with the classical DTC,this method utilizes active flux to establish the relationship between the torque and the amplitude of the stator flux.By calculating the stator flux online,the method eliminates the table established by the classical MTPA-DTC,and simplifies the numerical calculation process by utilizing the Newton-Raphson method.In addition,the control research of EV with dual in-wheel motors drive is carried out in straight and steering conditions.Combining the virtual master control with electric differential in multi-motor control,the virtual master electric differential is studied to realize the straight and steering of EV driven by two in-wheel motors.In this thesis,the MTPA–DTC strategy based on the active flux is verified by simulation and experiments.Simulation and experimental results show that the method can achieve the reference stator flux and can operate on the MTPA point,reducing the current amplitude and the copper loss.Furthermore,the virtual master electric differential control is verified.The results show that the method can not only realize the electric differential during steering,but also keep the dual motors synchronous operation in straight running with the load change.