Scheduled controller design for systems with varying sensor configurations: a frequency-domain approach

A novel parameter-dependent scheduled controller design is proposed for systems which exhibit switched dynamics. Switching is a result of varying sensor configurations available in the measurement system. The control architecture is based on a priori designed local linear time-invariant controllers, which are designed using frequency-domain loop-shaping techniques. Moreover, conditions on measured frequency response function data of the plant are provided under which the closed-loop system is input-to-state stable for arbitrarily fast parameter variations based on a generalized version of the circle criterion. By presenting a design and analysis framework for scheduled control systems that is easily implementable in existing control software, and does not require parametric plant models, this paper connects well to the industrial control practice. The effectiveness of the proposed scheduling technique, as a way to improve both transient and steady-state performance, is demonstrated by means of a case study which includes measurement results obtained from an industrial wafer stage system.