Research On Fractional-order Control Strategies For Permanent Magnet Synchronous Motor Speed Servo System

Permanent magnet synchronous motor(PMSM) is a new type of AC motor, which represents the development of speed servo system. So far, people have put forward many control methods for PMSM speed servo system. However, each method has respective merits and faults. In order to improve the control performances of PMSM system, we need to put forward new control methods.In recent four years, there are a few related results on the fractional-order control PMSM. Comparing with the integral-order control methods, these literatures demonstrate that the fractional-order control methods can obtain better control performances of PMSM through further enhancing the ability of resisting load disturbances and reducing the speed fluctuations. Therefore, the existing references provide a new idea for exploring control strategies unsed in high performance PMSM speed servo system. Inspired by the above discussions, in this paper, the following two aspects of innovative work have been done for study the fractional-order control method of PMSM speed servo system:(1) Sensorless control of permanent magnet synchronous motor base on fractional-order adaptive speed estimationIn this paper, from the mathematical model of PMSM and the established adjustable model of stator current, combined the stability theory of the fractional-order dynamical system and Lyapunov stability theory, a fractional-order adaptive estimation scheme based on model reference is presented, which is used to estimate the speed. The simulation results demonstrate that under the conditions of big range speed and time-varying system parameters, comparing the integral-order situation, this fractional-order adaptive method can estimate the speed more accurately, and also improve the speed tracking control performance and robustness of sensorless PMSM driving system(2) Control PMSM via double closed-loop fractional-order control strategyIn view of the significance of the current loop controller, which plays an important role to improve the speed response and the whole control system performances, a double closed-loop fractional-order control scheme is proposed for controlling PMSM. In this control method, fractional-order differential-integral controller and fractional-order proportional-integral controller are presented as the regulator in the cullent loop and speed loop respectivlly. By the using of the presented multi-stages synthesis design method, the gains and the fractional order numbers of two controller are designed out according to frequency domain criterionandoptimal principle of motor power factor. The analysis in frenqency domain demonstate the stability and robustness of the controlled PMSM system.The simulation results show that, in contrast to the traditional control method, under the condition of high speed, speed jump and load mutation, the presented control scheme not only can obtain better dynamic performance and robustness for motor speed servo system,but also can improve the operation efficiency of PMSM.The research results on fractional-order control PMSM can provide useful references for obtaining high performance PMSM speed servo system by effective control methods.