Research On The Control Strategy Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM) serving as actuating and controlling elements are extensively used in many practical fields including aerospace, CNC machine tools, electric vehicles etc due to their excellent advantages, such as high power density, high reliability, high efficiency, simple structure, small size, and light weight. Consequently, multi-motor synchronous control is indispensable for some production fields of spinning, printing and dyeing, papermaking and rolling, and production efficiency and quality of the products are directly affected by the controlling situation. Therefore, for the propurse of improving the accuracy of the speed of permanent magnet synchronous motor in this study,research contents and achievements are list in the following:1. In order to make the research on the control strategy of permanent magnet synchronous motor has a base and platform, the simulation model about voltage space vector PWM control technology of permanent magnet synchronous motor is built. The establishment of the simulation model is based on analysis of the structure and the mathematical model of permanent magnet synchronous motor. Through analyzing the principle of voltage space vector PWM control technology, it shows that this control method is very suitable for controling permanent magnet synchronous motor.2. The current of the motor stator contains high frequency noise, when the double closed loop of voltage space vector PWM control technology is applied to control the speed of permanent magnet synchronous motor. The PID controller of current loop need differential signal of current. The sliding mode variable structure controller also need differential signal. If the signal has noise, classic differentiator will amplify the noise, when using the classical differentiator to obtain the differential signal. So the differential signal will be submerged in the noise which is amplified. In order to solve this problem, the time-optimal tracking differentiator is applied. The results of simulation show that the time-optimal tracking differentiator overcomes the effect of noise amplification; it can provide the tracking signal which the noise is filtered and the differential signal of this tracking signal.3. Permanent magnet synchronous motors is a nonlinear system, which has the characteristics of multivariable, variable parameter, strong coupling. So sliding mode variable structure control technique which is not sensitive to parameter variations and disturbances is applied to control it. Through analysis and simulation, it is found that linear sliding mode variable structure controller which is based on combining linear sliding surface and the saturation function can reduce the chattering, but the control precision of the system is severly reduced. Therefore, this paper designs a nonlinear sliding mode surface. And the nonlinear sliding mode variable structure controller which is based on combining nonlinear sliding surface and the saturation function is designed. Simulation results show that, using the nonlinear sliding mode variable structure controller is designed in this paper to control motor, not only can weaken the chattering very well, but also can greatly improve the precision of the system.4. Designing a multi-motor adjacent cross coupling ring system which is controlled by nonlinear sliding mode variable structure controller. In order to solve the problem that each motor driving performance and load disturbance is not the same, adjacent cross coupling ring system is designed. Through analysising synchronization error state equation of the motor and the adjacent motor; and the tracking error state equation of the output speed and set speed, nonlinear sliding mode variable structure controller is designed. Comparing the result of simulation that controlling by nonlinear sliding mode variable structure controller with the controling by PID controller, the controlling by linear sliding mode variable structure controller, it proves that the motors which are controlled by nonlinear sliding mode variable structure controller based on multi-motor adjacent cross coupling ring system has the better performance of synchronization, at the same time the system has very strong robustness.