Position control of a magnetic levitation system via a PI-PD control with feedforward compensation

摘要

This paper presents a proportional integral-proportional derivative (PI-PD) control with feedforward compensation for positioning control of a magnetic levitation (maglev) system. Maglev system has gained numerous attention in high speed and precision engineering applications. However, it remains a challenging task to obtain a satisfactory positioning performance for the maglev system due to its inherently nonlinear and open loop unstable characteristics. Although advanced controllers show promising positioning performance in the maglev system, but deep understanding of control theory is required in the design procedure. While the classical controllers have the simple and straightforward design procedure, yet they suffer from poor transient response. Thus, a two-degrees-of-freedom (2-DOF) PID controller is proposed to solve the limitation of the classical PID controller. In this paper, a PI-PD controller is utilized to improve the system transient response. Still, the transient response of the PI-PD control system is not yet the satisfied one. Therefore, a model-based feedforward control is incorporated with the PI-PD (FF PI-PD) controller to enhance the positioning performance of the maglev system. The FF PI-PD controller is designed by using the pole-placement method and the system driving characteristic in open loop. The proposed controller can be easily implemented to the maglev system without require any deep understanding of control theory. The effectiveness of the proposed controller is examined experimentally and it's positioning and tracking performances are compared with the PI-PD controller. Experimental results demonstrate that the FF PI-PD controller has a superior positioning performance than the PI-PD controller with better overshoot reduction characteristic and faster settling time. The FF PI-PD controller has reduced the overshoot and settling time by 49.7 % and 66.0 %, respectively in comparison to the PI-PD controller. Furthermore, the FF PI-PD controller has improved the system positioning accuracy up to 100 % as compared to the PI-PD controller. Besides, the FF PI-PD controller also reduced the maximum tracking error by 56.7 % in contrast to the PI-PD controller.