Research On Adaptive Control Technology Of Permanent Magnet Synchronous Motor

Adaptive control technology is widely applied in the permanent magnet synchronous motor(PMSM). In CNC machines, shaping a manipulator, intelligent wheelchairs, and other control areas requiring high precision, introducing the adaptive control strategy can improve the accuracy of servo system, the stability and anti-interference capability.During the motor operation, the load change will cause a variation of the motor speed and an impact on the stability of the motor. The load, which includes load torque, rotor inertia, friction coefficient, stator resistance etc., refers to a type of parameters affecting the performance of the motor. In this thesis, we take the load torque as our research object to estimate the change rate of load torque. We analyze the effect of load torque on the motor speed, afterwards we present two kinds of control method to restrict the load torque disturbance. This thesis mainly describes from the following aspects:1.We analyze the adaptive control research status of PMSM, master the common methods for restraining load disturbances, then we summarize the advantages and disadvantages of these methods.2.Our control object is a type of 750 w low inertia servo motor. A simulation model of the motor is built in the MATLAB/Simulink software and then we use this model to study the effect of load torque on the motor speed.3. We propose a method to estimate the load torque. Because in the motor the load torque cannot be measured, only estimation is possible. We get the estimate value. We know that in the motor vector control system, a control of the motor speed depends on the current iq and a variation of the load torque can cause a change of current iq. The motor speed fluctuations can be revised by a compensation for the current iq. In order to obtain the compensating current, it is necessary to estimate the change rate of the load torque. By collecting the motor speed's information on the load torque variation and using the least squares method we can estimate the change rate of the load torque.4.We propose two control methods to restrain the impact of the load torque on the motor speed.The first method is the feed-forward compensation method. In the motor speed loop we design a load estimator and a q-axis current feed-forward compensator. The function of the load estimator is to estimate the change rate of load torque based on the change of the motor speed. However, the function of the compensator is to calculate the compensation current by using the change rate and compensate the current iq in the current loop. This method can prevent motor speed fluctuation and realize the self-tuning control of the motor in the load torque disturbance.The second method is self-tuning PI controller design method. In the speed loop of the motor only a PI controller cannot adjust the load torque of various ranges. Therefore, we propose a self-tuning PI controller. According to the size of the load torque, we design three PI controllers. In three groups of PI controller, choosing the parameter Kp?Ki of the best performance can reduce the motor speed error. The self-tuning PI controller we designed is simple in structure, does not need complex calculations, and facilitates the implementation on project.