Self-sensing and quality factor control circuits for piezoelectric millimeter-sized resonant cantilevers

Abstract

For ever-increasing applications of resonant piezoelectric-excited millimeter-sized cantilever (PEMC) such as biosensors, viscosity, and density sensors, the need for design and implementation of a portable circuit for measuring the resonant frequency shift and/or the variation in the quality factor of PEMC becomes crucial. In this article, active and passive self-sensing bridge circuits are designed, fabricated, and implemented for a PEMC. The performances of these circuits are examined for the resonant frequency and quality factor measurements for vibration of PEMC in two different environments. For this purpose, a parameter-tuning procedure for the passive bridge based on experimental identification of Van Dyke model parameters is proposed and applied for the vibration of PEMC in air and 98% glycerol solution. Also, a compensation method for potential instability of active bridge circuit is proposed and developed experimentally for the vibration of PEMC in these environments. To increase the quality factor, the fabricated passive bridge is used in a designed control circuit, which is based on positive feedback signal proportional to the vibration velocity. The experiments show that with the proposed and implemented control circuit, the quality factor will increase by about 80% in air and 25% in glycerol.