PASSIVE DAMPING FOR ROBUST FEEDBACK-CONTROL OF FLEXIBLE STRUCTURES

This paper investigates the benefits of passive damping in single-input single-output (SISO) and multi-input multi-output (MIMO) feedback controlled structures. Theoretical formulations are derived verifying improved stability robustness characteristics for simple controlled structures on phase margin, gain margin, and root locus properties of a SISO system. Control design techniques for dosed-loop bandwidths beyond the first modal frequency require accurate knowledge of the structural dynamics, particularly at crossover. The use of passive damping in the structural design allows for a greater margin of error in pole-zero cancellation at crossover, thus improving the stability robustness. Minimum levels of required passive damping are derived for robust control of uncertain structures. The derivations are extended to suggest application to MIMO systems. Robustness improvements are quantified in case studies for an 8th-order SISO example and an 18th-order MIMO example and compared to the simple derivations.