Piezoelectric Smart Structures For Active Vibration Isolation System

In past two decades, with the development of material science, computer technology, signal processing and control theories, intelligent structures have become one of the most active research fields,and the active vibration control of intelligent structures is also a very important branch.In this thesis,the dynamic models of a specific precise instrument in spacecraft are established and an active vibration isolation system based on piezoelectric intelligent structures is constructed. Theoretical analysis and numerical simulation on this system has been carried out. Piezoelectric intelligent structure is applied to civil engineering.The piezoelectric intelligent control devise is used for the control of translation-torsion coupling responses of multi-story frame structure suffered from earthquake. The main research work and conclutions are listed as follows.(1) Based on the piezoelectric equation,the actuating and sensing ability for the piezoceramics are discussed in details.The actuating equation and sensing equation are derived when piezoceramics work as both sensors and actuators.The self-sensing actuators are discussed.(2) The dynamic models of a specific precise instrument in spacecraft are established and an active vibration isolation system based on piezoelectric intelligent structures is constructed.(3) The theory of morden optimal control is used for the controller design of the active vibration isolation system. Two algorithms, instantaneous optimal control and linear quadratic gauss optimal control ,have been discussed and compared.An instantaneous optimal closed-loop control algorithm in structural space is derived by using the Newmark Scheme.(4)Through numerical simulation, the validity and advantage of intelligent structures for active vibration isolation has been verified. The results show that piezoelectric intelligent structure has favorable performances for vibration isolation in whole frequency band. It is superior to passive vibration isolation system, and also to the general active-passive hybrid vibration isolation system.The functions of the weighting matrices Q and R are analysed and the conclusion is obtained thatinstantaneous optimal control algorithm is superior to linear quadratic gauss whenchoosing the same weighting matrices.(5)The piezoelectric intelligent control devise is used for the control of translation-torsion coupling responses of multi-story frame structure which is suffered from earthquake.The results of an example illustrate that this intelligent control devise can effeiciently reduce the structual translation-torsion coupling responses induced by earthquake.