Experiments on Active Vibration Control of a Coupled Flexible Structure

The control of vibration in large structures is complicated by the presence of many closely-spaced modes within the contoller bandwidh. Problem of stability robustness arise since accurate models for the entire structure are difficult to generate. This paper investigae stability issues associated with a decentralized control strategy applied to subsystem models of the entire structure. A novel coupling parameter which characterizes the degree of subsystem interaction in a 2×2 system is introduced and defined. This parameter is used to determine stability bounds and performance limitations for decentralized active vibration control of large structures. A simple cantilever beam structure with attached disk is used to experimentally confirm the theoretical development when subsystem coupling is introduced by the actuators. The stability analysis suggests that the set of coupled system can be split into two regions by a critical coupling value, c*. One region can be controlled by a diagonal controller and the other can be controlled by an off-diagonal controller. Should the degree of coupling change from one side of c* to the other during operation, no single controller is capable of maintaining stability.