Electrical Properties and Power Considerations of a Piezoelectric Actuator

Abstract

This paper assesses the electrical characteristics of piezoelectric wafers for use in aeronautical applications such as active noise control in aircraft. Determination of capacitive behavior and power consumption is necessary to optimize the system configuration and to design efficient driving electronics. Empirical relations are developed from experimental data to predict the capacitance and loss tangent of a PZT5A ceramic as nonlinear functions of both applied peak voltage and driving frequency. Power consumed by the PZT is the rate of energy required to excite the piezoelectric system along with power dissipated due to dielectric loss and mechanical and structural damping. Overall power consumption is thus quantified as a function of peak applied voltage and driving frequency. It was demonstrated that by incorporating the variation of capacitance and power loss with voltage and frequency, satisfactory estimates of power requirements can be obtained. These relations allow general guidelines in selection and application of piezoelectric actuators and driving electronics for active control applications.Key words, piezoelectricity, power requirements, variation of capacitance, empirical relations Subject classification. Physical Sciences: Materials 1. Introduction. The potential of piezoelectric ceramics as actuators and sensors has been widely documented in applications ranging from aerospace to biomedical. One of the areas that incorporates the use of these materials at NASA LaRC is the area of active noise and vibration control [1][2][3]. In this application, the targeted fundamental frequency is between 50-100Hz, with the next higher modes ranging up to 400-600Hz. These are higher frequencies than in structural or aeroelasticity control because of the pressurized or pre-loaded aircraft cabin/fuselage. Practical limitations such as acceptable excitation voltages, mechanical durability, coupling to the control structure and control system complexity and stability are driving research for sensor and actuator improvement. A critical issue that arises when using surface mounted transducers is the piezoelectric power consumption necessary to drive them. Applications are found to depend upon the electrical characteristics of the PZT transducers, namely the capacitive and resistive behavior of the actuator, which in turn affect their power consumption characteristics.A number of researchers have investigated the power consumption characteristics of PZT actuators used to excite a host structure [4][5][6] and found a coupling between the mechanical motion of the structure and the electrical characteristics of the piezoelectric actuator. Research by Brennan and McGowan [7] shows that the power consumption of piezoelectric materials used for active vibration control is independent of the mechanical motion of the host structure when the structure is completely damped. From these findings, they conclude that the power requirements of the piezoelectric actuator are only dependent upon its geometry and material pro...

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