Distributed active vibration control with embedded sensor network techniques
In this dissertation, distributed control with sensor networks is used to suppress beam vibrations. The distributed active vibration control strategy has the advantages of being scalable and fault-tolerant for use in large-scale systems. A distributed control system normally consists of numerous localized controllers called nodes. Each localized controller has a sensor, an actuator and a means of communicating with other nodes in the system. The goal of distributed control is to achieve global performance by sharing sensor information among the localized controllers. This is in contrast to decentralized control whose localized controllers work independently to achieve a global performance, and centralized control which utilize one central processor. A simply supported beam with six pairs of piezoelectric transducers acting as sensors and actuators is the active structure investigated. The disturbance on the beam is band-limited white noise (0 - 600 Hz). The dynamics of the beam are obtained using experimental system identification, and a 36 state model is selected for control design use after exploring various model sizes. Since existing distributed control design approaches are not applicable to structural vibration systems due to the strongly connected nature of vibration system dynamics, new distributed controllers are designed based on traditional H2 optimal control theory. Such H2 optimal control has been proven effective and robust at attenuating structural vibration in centralized strategy, and it is extended here to a distributed architecture. Two types of sensor grouping strategies in the distributed control system are considered: groups based on physical proximity and groups based on modal sensitivity. Distributed middleware services such as clock synchronization and network communications routing are also investigated and implemented experimentally for vibration control. This work is the first experiment implemented in the distributed vibration control field, and control performance results demonstrate the effectiveness of the two distributed grouping approaches. A fault-tolerant active vibration control system is applied to a simply supported beam with high order. System failures are detected and isolated by Beard-Jones (BJ) filters, and then a controller specifically designed for the faulty system is switched on, in order to maintain optimal control performance and stability under failure conditions.