Piezoelectric bimorph charge mode force sensor

In this work, an analytical model, a finite element analysis and measured results for a planar, parallel and symmetrical piezoelectric bimorph structure are presented. The bimorph consists of two rectangular piezoelectric strips that are connected back-to-back on a thin metallic centre electrode. The bimorph is intended to be used as a millinewton range force sensor with dynamic excitation. The bimorph is modelled with a static, analytical expression for generated charge, voltage, displacement and force that correspond to the deflection of a freely oscillating piezoelectric bimorph. Also, a case where the movement of the bimorph is blocked is analyzed. A circuit that is used to actuate the bimorph is presented, as well as the measured results from the actuator and the sensor side of the bimorph in both free oscillation and blocked cases. The measurement results show a reasonably good agreement with the analytical model and very good agreement with the FEM model. Force sensor setup and a way to measure the force inflicted on the bimorph are also presented, as well as the force response of the bimorph against a commercial piezoresistive force sensor.