Circle Condition-Based Feedback Controller Design for Fast and Precise Positioning

This paper presents a novel feedback (FB) controller design methodology for fast and precise positioning of mechatronic systems. Improvement of disturbance suppression performance is one of the general and important indexes in the FB controller design to realize the precision performance. However, since the stability of FB system generally restricts the disturbance suppression capability, improvements in both disturbance suppression and stability performance are difficult to be achieved. In this paper, therefore, a circle condition-based FB controller design is proposed to provide the required disturbance suppression with the desired stability. The proposed FB controller specifies a stability margin (i.e., gain and phase margins) as a circle condition on the Nyquist diagram using a linear matrix inequality (LMI) technique, whereas the disturbance suppression capability is determined by giving arbitrary poles in the FB control system. In addition, the proposed FB controller can be systematically designed on the basis of an optimization technique using the LMI. Effectiveness of the proposed approach has been verified by numerical simulations and experiments using a prototype of a linear motor-driven table system.