FEM-Based Design and Characterization of a Millimeter-Scale Piezoelectric Resonance Force Sensor

This paper presents a millimeter-scale piezoelectric effect-based force sensor that uses the change in its resonant frequency as the detection principle for high sensitivity and a wide measurement range. Such characteristics are suited for robot hand applications that can not only detect a small force but also handle large payloads. In this paper, we develop a methodology to estimate the relationship between the applied force and the resonant frequency shift by combining classic contact theory and the finite element method (FEM) analysis. Although this relationship is non-linear, the designability of the sensitivity and measurement range is demonstrated by the simulation. The simulation results based on the method are verified, showing good agreement with experimental results. The static characteristics, including sensitivity, standard deviation, and resolution, are evaluated using the prototype sensors with characteristic lengths ranging from 1mmto 4 mm. The 4-mm model has a measurement range of 77 mN to 300 N, and the smallest model, which is one of the smallest force sensors suitable for practical implementation, has a measurement range of 9 mN to 20 N.