<title>Analysis of a self-powered piezoelectric vibration damper</title>

Abstract

There is considerable interest in the use of piezoelectric ceramic actuators for vibration suppression of thin lightly damped structures. One technique receiving much attention is to 'actively' drive the piezoelectric ceramic to control the out-of-plane vibration of the structure, this technique requires an external power source. Another technique involves using an R-L resonant shunt, with the piezoelectric element, to achieve single-mode passive vibration control of the structure - analogous to a mechanically tuned mass damper. The R-L resonant shunt scheme requires large inductors making this technique difficult to implement unless an active inductance, requiring an external power supply, is used. This paper looks at the concept of a self -powered discrete time piezoelectric damper that uses piezoelectric elements as the power source, sensor and actuator. The device uses a small portion of the electrical energy produced by the piezoelectric elements to power the electronic circuitry, thus eliminating the requirement for an external power source. The circuit controls the transfer of electrical energy between a storage device (capacitor) and the piezoelectric elements, which also operate as an actuator to suppress vibration. This approach does not need large value inductors such as required for passive tuned R-L resonant shunt damper and does not require tuning to the structural resonant frequency. The design concepts of a self-powered discrete time piezoelectric vibration damper are discussed in this paper. This device is referred to as a STrain Amplitude Minimisation Patch (STAMP) damper. Initial experimental results have shown that a concept demonstrator of the non-optimised STAMP damper system had better damping than the simple resistor shunt damper but not as good as the tuned R-L resonant shunt damper. This paper outlines, in more detail, the theoretical analysis of the STAMP damper system thus illustrating the fundamental differences between more conventional passive techniques such as resistor and R-L resonant shunts with piezoceramic elements. The aim of the paper is to theoretically show the benefits of the STAMP damper compared to other piezoceramic-based vibration damping concepts. A case study of the operation of the three systems, resistor, R-L resonant shunt and STAMP system, on a cantilevered beam system is undertaken. The case study quantifies the vibration reduction mechanisms of each system studied. It is shown that, as expected, the resistor shunt system dissipates energy in the resistor element to achieve vibration suppression. However, both the tuned R-L resonant shunt and the STAMP systems achieve their significant vibration reduction by producing a voltage component across the piezoceramic elements which is in-phase with the system velocity, rather than by power dissipated in the purely resistive components. The "STAMP" circuit has no intentional dissipation element, instead using the "harvested" power to drive the piezoelectric ceramic element, thus it generated the largest in-phase piezoelectric voltage component and thus, potentially, the largest effect on damping (of the methodologies analysed). The tuning requirements were also examined, illustrating the relatively narrow range of effective operating frequencies for the R-L damper scheme compared with the pure resistor or STAMP techniques.