Torque Tracking Control Of Permanent Magnet Synchronous In-Wheel Motor For Electric Vehicle

To get rid of the dependence on non-renewable energy of oil and reduce the airpollution, the auto industry has been committed to develop more advanced and reliableelectric vehicles. The biggest diference between electric cars and traditional vehicle is touse the battery-powered motor driven system, and there are currently centralized drivensystem and distributed driven system. In-wheel motor technology has been becoming thehot research object currently, because it can save more space and improve the performanceof the electric vehicle. In this paper, based on the control strategy of the torque demandas the center in the vehicle, we determine to study the torque tracking control of thein-wheel motor, and we are dedicated to solve the problem of torque accuracy control ofthe in-wheel motor, in order to improve the performance of the electric car.Because the in-wheel motor is raised the requirements of large starting torque, highpower density, and high reliability, we choose the permanent magnet synchronous motorwith high power density, good torque performance and overload performance as the motorbody of the in-wheel motor. In this paper, we will introduce the mechanical structure ofthe in-wheel motor and the permanent magnet synchronous motor. To understand andsimplify the mathematical model of the permanent magnet synchronous motor, we convertthe mathematical model on the ABC axis to the mathematical model on the αβ axis andthe mathematical model on the dq axis by the principle of coordinate transformation.In this paper, the theory diference between FOC and DTC is analyzed in detail andthe comparison experiment is operated. The results show that FOC has a more stablecontrol performance of the motor, but the the algorithm calculation is large because of thethe principle of coordinate transformation and the motor position needs to be monitor;DTC has a fast torque response control performance of the motor, but at the same timethere is large torque ripple, and the characteristics of stability control is weak. We decideto combine the advantages of two algorithms, and use more advanced estimation algorithmand control algorithm to design the motor controller to achieve rapid and accurate torquetracking control. In this paper, the main innovation points:1.This article uses the algorithm of EKF to design and build the flux estimator inDTC. For PMSM has the characteristics of strong nonlinear coupling and parameteruncertainties, EKF algorithm has the better strong anti-interference characteristics thanthe pure integral estimator in traditional DTC. It can avoid the cumulative error andintegral saturation in the pure integral estimator and estimate more accurate.2.In this paper, the SVM algorithm in FOC will be applied in the traditional DTCto replace the switch table module. Traditional switch table sends a unit basic voltagevector in the unit sampling time only control the motor approximately. SVM can sendthe suitable control voltage to the motor by combining two unit voltage vector to processthe flux and torque ripple caused by the traditional switch table.3.For PMSM has the characteristics of strong nonlinear coupling and parameter un-certainties, the advanced nonlinear algorithm "Triple-step method" will be applied tocontrol PMSM in this paper. Triple-step method contains the steady control module,feed-forward control module and the error feedback control module. The structure andlogic of the control law is clear. In the framework of Triple-step controller, the systemvarying parametric does not afect the controller structure. Moreover, the control gainsare state-parameter dependent, which strength the the self-adjustment ability of the con-troller in the motor running in diferent working conditions. The simulink experimentsshow that the controller can achieve better rapid and accurate torque tracking control.