A fractional order composite control method for a class of motion control systems

In this paper, a fractional order composite control scheme for a class of permanent magnet synchronous motor (PMSM) speed servo systems is proposed to fulfil the requirements of tracking performance and disturbance rejection performance in actual applications. An extended state observer is employed to compensate the uncertainties in the current loop and convert the PMSM speed servo plant into a double-integrator model. A fractional order proportional-derivative (FOPD) controller is applied to control the speed of the PMSM. The FOPD controller is tuned by a differential evolution based optimization method, ensuring the control system to achieve optimal step response performance. Simulation results show that the PMSM servo system using the proposed control method achieves the robustness to parametric uncertainties and load disturbance. Besides, it can achieve better step response performance than the systems using some existing control methods.