High precision linear motor control via relay-tuning and iterative learning based on zero-phase filtering

In this paper, with a modest amount of modeling effort, a feedback–feedforward control structure is proposed for precision motion control of a permanent magnet linear motor (PMLM) for applications which are inherently repetitive in terms of the motion trajectories. First, a proportional integral derivative (PID) feedback controller is designed using a relay automatic tuning method. An iterative learning controller (ILC) based on zero-phase filtering is applied as feedforward controller to the existing relay-tuned PID feedback controller to enhance the trajectory tracking performance by utilizing the experience gained from the repeated execution of the same operations. Experimental results are presented to demonstrate the practical appeal and effectiveness of the proposed scheme.