Smart piezoelectric film sensors for structural control

This paper describes how structural control information can be embedded in a smart piezoelectric film. The control knowledge is imparted by shaping a piezoelectric film. Shaping involves electrode etching and splicing together sections with varying poling directions. The shaping can be used to implement a general class of spatial filters. This technique is successfully demonstrated in this work using an articulated flexible beam. The controller is realized in terms of a pair of shaped piezoelectric films. One film implements a spatial filter of the strain profile of the beam, and the other implements a spatial filter of the strain rate profile. Electronic circuits for measuring piezoelectric film signals are analyzed in terms of their fidelity, and their effect on controller performance. Although other researchers have explored the concept of imparting controller information in a shaped piezoelectric film, they have not explicitly developed a methodology for coping with the noise characteristics of these sensors. In this paper, an H_∞ controller design procedure is used to mitigate the effects of sensor noise, torque disturbances, and the limitations of the instrumentation. The major contribution of this paper is the integrated design methodology which copes with sensor, actuator, and modeling limitations in a practical structural control application.