Motion Controller Design with Automatic Loop Shaping and Minimum Tracking Errors

Loop shaping is a widely applied technique for controller design. In particular, the frequency constrained time-domain optimization (FreCTO) controller uses a set of discrete frequency constraints for loop shaping and achieves excellent performance. However, manual loop shaping is inefficient and the result cannot be optimal. To solve this problem, this paper proposes a dual-loop automatic loop shaping algorithm. The inner loop minimizes tracking errors, boosts the bandwidth, and suppresses resonant peaks and 'leakage of gains', whereas the outer loop reduces the length of control parameters and adjusts the number of constraints while reserving the desired phase margin. Experiments on a biaxial table verify that the desired loop shape is automatically attained by the proposed algorithm, and the controller with automatic loop shaping outperforms the one with manual loop shaping.