An active micro-force sensing system with piezoelectric servomechanism

This paper aims at developing an active force sensing technology for micromanipulation and microassembly using in-situ piezoelectric polyvinylidene fluoride (PVDF) films symmetrically bonded to the surface of a flexible cantilever beam structure. The designed micro-force sensing beam has both sensing and actuating layers. The sensing layer can detect the deformation signal due to the external micro-force acting at the sensor tip, the signal is then fed back to the actuating layer through a servoed transfer function or servo controller, as a result, a counteracting bending moment generated by the actuating layer can be used to balance the deformation of sensor beam in real time. Once balanced, the sensor tip will maintain in the equilibrium position as if the sensor stiffness is virtually improved, yielding accurate motion control of the sensor tip. Especially, the micro-force can be obtained by calculating the balance force through the counteracting servo voltage applied to the actuating layer. The developed active structure greatly enlarge dynamic range of micro-force sensor and enhance the manipulability during micromanipulation/microassembly when the sensor is mounted at the end-effector. Preliminary calibration and experimental results both verified the performance of the developed active micro-force sensor and the effectiveness of the models.