ON THE DESIGN OF PIEZOELECTRIC SENSORS AND ACTUATORS

Piezoelectric devices are becoming more common with the introduction o f smart sensors and actuators, and new developments in piezoelectric p olymers and ceramics. However, as the authors found, obtaining relevan t information for a comprehensive design of piezoelectric sensors and actuators is quite an ordeal. The literature on piezoelectricity is ma inly divided on oversimplified explanations based on quartz crystals o r on journals and books requiring an extensive background in solid sta te physics. This paper provides a non-trivial description of piezoelec tricity from the perspective of sensor/actuator design. Contributions include: (a) using a simple matrix approach to (i) clearly describe th e piezoelectric relationships, and (ii) clearly show how to manipulate the boundary conditions to experimentally obtain the constitutive par ameters; (b) showing how the coefficients in the transfer function of a pressure sensor vary as the mode of operation change from isothermal to adiabatic by defining effective capacitances, permitivity, piezoel ectric, and compliance constants; (c) showing that the wave equation i s a natural result of introducing a kinetic energy term into the energ y balance. (C) 1998 Elsevier Science Ltd. All rights reserved.