| Active vibration control remains a topic of significant relevance and importance due to high performance demands of certain space structures as well as growing interest in the development of terrestrial structures using feedback control. This thesis presents two new approaches, to control system design for flexible structures. In the first approach, piezoelectric transducers are continually switched between actuator and sensor modes to enhance controllability and observability of the system. This approach can potentially reduce the number of piezoelectric transducers and associated hardware by 50%. In the second approach, piezoelectric transducers are used as sensors to estimate modal displacements and cables are used for the purpose of actuation. It is shown that tension in cables can be applied and released to directly suppress vibration of structures or vary the stiffness of the structure which results in modal energy redistribution. By properly designing switching strategies for the cable tension, modal energy can be redistributed, and specifically energy associated with higher modes can be funneled to the lower modes. This enables vibration suppression using a simple controller that can potentially sidestep the spillover problem. |
