Research On Nonlinear Control Strategy In Motion Control System Of Pmsm

AC motion control system has many advantages over DC motion control system, owing to the utilization of vector control technique and direct torque control technique, especially in the Permanent-Magnetic-Synchronous-Motor(PMSM) motion system for high performance applications. However, AC motor has such characteristics as multi-variable, high-coupled and nonlinear, which implies that it is very difficult to control. It is well known that traditional linear control methods are only limited to linear plants. In order to achieve higher performance, it is necessary for AC motor control system to apply nonlinear control methods.Several nonlinear control strategies have been involved in this paper, such as feedback linearization, variable structure control, backstepping and intelligent control Feedback linearization, based on differential geometry, is global, which is different from linearization only limited at some points. Using feedback linearization method, an input-output decoupled model of PMSM is achieved. Then by means of pole assignment method, control strategy is obtained. Simulation shows good results in various speed ranges. And the system is also robust for load variation. Feedback linearization proves successful for solving specific nonlinear problem. But it has a strict requirement for the accuracy of motor model and parameters.As we know, variable structure control system is immune to parameters variation and disturbances. This control strategy has been paid more attention since 1950s. The main problem in variable structure control is chattering. In order to alleviate chattering, a sector-shaped boundary layer is presented: And the simulation show good results of this control strategy.Adaptive backstepping, which is a new control strategy introduced in recent years, is adopted in PMSM servo control systems to cope with matched or unmatched uncertainties. Among these control strategy, Adaptive laws are applied for compensating parameter variations and load disturbance. Another control strategy, which is called integral backstepping method, is also presented to deal with the same problem above. Both guarantee the position tracking. However, the former requires more calculation and longer settling time, and the later may result in delayin system response.Artificial intelligent control is a latest strategy for motion control. It has nothing to do with plant's model. But the whole system has the property of robustness and adaptability . Two method of intelligent control are used in this paper. One is fuzzy controller for PMSM speed control. The other is Adaline neural network for estimating speed control in PMSM motion system.Speed sensorless control has become a focus in motion control system in recent years. This paper provides two speed estimation algorithms, one is based on Extended Kalman Filter (EKF), the other on Adaline neural network.There are still many problems in nonlinear control of motion system, one of which is on how to design nonlinear control strategy with discrete speed observer in motion system. Many efforts will focus on this challenge later.