Frequency domain modelling and control of fractional‐order system for permanent magnet synchronous motor velocity servo system

This study presents fractional‐order system modelling and control for a permanent magnet synchronous motor (PMSM) velocity servo system. Fractional‐order model of the PMSM velocity servo system is obtained theoretically for an improved modelling precision. To identify the parameters of the proposed fractional‐order model, an enhancement of the classic Levy identification method with weights is applied. In a real‐time PMSM velocity servo plant, the fractional‐order model is identified according to the experimental tests using the presented algorithm. The fact that the fractional model is more accurate than traditional integer‐order model is substantiated using by the mean square error performance index. Two H ∞ stabilising output feedback controllers are designed for velocity servo using a simple scheme according to the identified fractional‐order model and the traditional integer order one, respectively. The experimental test performance using these two designed H ∞ controllers is compared to demonstrate the advantage of the proposed fractional‐order model of the PMSM velocity system.