Masters Research - Master of Engineering (Research)
This thesis considers a number of related problems in the area of passive and semi-active vibration control of piezoelectric laminates. The thesis consists of three main parts. The first part of the thesis develops a mathematical model of a physical resonant system-piezoelectric laminated simply supported beam. It is essential to have a good understanding of the physical system so that the associated problems with passive and semi-active shunt damping can be addressed. The second part of the thesis is concerned with problems related with current passive shunt damping techniques using a single piezoelectric laminate. One of the current problems with multiple mode techniques is determining the correct resistive damping for each resonant mode. Therefore, a systematic method is presented for determining the optimal resistance elements by minimizing the H2 norm of the damped system. After the design process, shunt circuits are normally implemented using discrete resistors, capacitors and virtual inductors (Riordan Gyrators). The difficulty in constructing the shunt circuits and achieving reasonable performance has been an ongoing problem. A new approach to implementing piezoelectric shunt circuits is presented. A “synthetic impedance”, consisting of a voltage controlled current source and digital signal processor (DSP) system, is used to synthesize the terminal impedance of a required shunt network. The third part of the thesis is concerned with the semi-active vibration control of piezoelectric laminated. This part addresses a number of associated problems with the current passive shunt damping schemes. The foremost being the complexity of the shunt circuits required to dampen multiple modes. They generally act to minimize structural vibration at a specific frequency – which are rarely stationary. Therefore, a new broadband semi-active shunt technique for controlling multiple modes has been developed. The “negative capacitor” controller is proposed theoretically, and then validated experimentally. The negative capacitor is simular in nature to a passive shunt damper as it uses a single piezoelectric transducer to dampen multiple modes of a flexible structure.
University of Newcastle Research Higher Degree Thesis