Circle Condition-Based Feedback Compensation With Frequency Shaping for Improvement of Settling Performance

This paper presents a novel feedback (FB) controller design on the basis of a circle condition for the fast and precise positioning of mechatronic systems. In general FB controller design, both disturbance suppression and system stability (i.e., gain and phase margins) are essential indexes to provide the desired control performance. A circle condition-based FB controller design by an optimization framework using a linear matrix inequality (LMI) technique has been already proposed in the literature, where the disturbance suppression performance was successfully improved with the desired stability margin. However, since the conventional approach did not consider the frequency shaping of FB control system, the fine positioning performance was deteriorated by response variations due to mechanical parameter variations, disturbances, and/or plant uncertainties. In this paper, therefore, a circle condition-based FB controller design considering the frequency shaping is proposed to achieve robust properties against the response variations. Effectiveness of the proposed approach has been verified by numerical simulations and experiments using a prototype of linear motor-driven table system.