Fractional order modeling and control for permanent magnet synchronous motor velocity servo system

This paper presents the application of fractional order system on modeling the permanent magnet synchronous motor (PMSM) velocity servo system. The traditional integer order model of the PMSM velocity system is extended to fractional order one in this work. In order to identify the parameters of the proposed fractional order model, an integer order approximation of the fractional order operator is applied and a state-space structure is presented for using the output-error identification algorithm. In real-time PMSM velocity servo plant, the fractional order model is identified according to some experimental tests using the presented algorithm. Two proportional integral (PI) 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 PI controllers is compared to demonstrate the advantage of the proposed fractional order model of the PMSM velocity system.