PASSIVE DAMPING FOR ROBUST FEEDBACK-CONTROL OF FLEXIBLE STRUCTURES

This paper investigates the benefits of passive damping in single-inpu t single-output (SISO) and multi-input multi-output (MIMO) feedback co ntrolled structures. Theoretical formulations are derived verifying im proved stability robustness characteristics for simple controlled stru ctures on phase margin, gain margin, and root locus properties of a SI SO 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 th e structural design allows for a greater margin of error in pole-zero cancellation at crossover, thus improving the stability robustness. Mi nimum levels of required passive damping are derived for robust contro l of uncertain structures. The derivations are extended to suggest app lication to MIMO systems. Robustness improvements are quantified in ca se studies for an 8th-order SISO example and an 18th-order MIMO exampl e and compared to the simple derivations.