Design of an Analog Adaptive Piezoelectric Sensoriactuator
In order for a piezoelectric transducer to be used as a sensor and actuator simultaneously, a direct charge due to the applied voltage must be removed from the total response in order to allow observation of the mechanical response alone. Earlier researchers proposed electronic compensators to remove this term by creating a reference signal which destructively interferes with the direct piezoelectric charge output, leaving only the charge related to the mechanical response signal. This research presents alternative analog LMS adaptive filtering methods which accomplish the same result. The main advantage of the proposed analog compensation scheme is its ability to more closely match the order of the adaptive filter to the assumed dynamics of the piezostructure using an adaptive first-order high-pass filter. Theoretical and experimental results are provided along with a discussion of the difficulties encountered in trying to achieve perfect compensation of the feedthrough capacitive charge on a piezoelectric wafer.