<title>Power flow and amplifier design for piezoelectric actuators in intelligent structures</title>

Abstract

In developing intelligent structures in which actuation, sensing, and processing elements are physically integrated within the structure, the use of piezoelectric actuators places certain requirements on the electronic components which drive them.Applications may impose strict limitations on power consumption and heat dissipation, and structural integration brings an added requirement for component miniaturization. An understanding of the power flow behavior of piezoelectric actuators in controlled structure applications is therefore important. This paper addresses power issues in the application of piezoelectric actuators and embedded electronic components. The power flow characteristics of piezoelectric actuators are examined in closed-loop control applications. An analysis is presented of the power flow and voltage and current requirements of a piezoelectric actuator in a simple system, along with implications for the design of linear amplifiers. The contributions of various elements to average and peak power flow levels are identified, as is the effect of loop closure on the impedance which the actuator presents to the amplifier.1 . INTRODUCTION Piezoelectric materials, characterized by their ability to deform under the application of an electric field, have found numerous applications in the field of structural l ,2,3,4,5 Much work has been performed in characterizing piezoelectric elements, developing sensors and controllers, and addressing the requirements for embedding piezoelectric elements and electronic processing components. Practical issues of power conversion and amplification, however, have until recently been largely neglected. The modelling of such piezoelectric actuators for dynamic control of structures is well established; Ref. 6 presents a general formulation of the use of a variational principle to derive equations of motion relating actuator voltages and charges to structural displacements and disturbance forces. As power duals, the voltage and current determine the flow of power between the electronic control system and the actuator/structure combination. Ref. 7 uses impedance modelling to compute various components of both the electrical and mechanical power flow and dissipation for a structure actuated in an open loop condition; the derivation of the various impedances, however, is not always straightforward.The objective of the present work is examine power issues by applying the modelling techniques of Ref. 6 to a simple dynamic system: a cantilever beam modelled with a single mode. Although the flow of mechanical energy between actuator and structure is not explicit as in Ref. 7, the use of energy principles allows the derivation of electromechanical models based on Rayleigh-Ritz or finite element methods, which are readily extended to problems of complex geometry and large numbers of modes, sensors, and actuators. The simplicity of the single-mode Rayleigh-Ritz model presented here allows the derivation of interesting relations and parameter groupings which may shed further light on ...

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