Kalman filter-based loading rate-dependent hysteresis compensation of flexoelectric torsional responses in polyvinylidene fluoride films for shaft torque sensors

Abstract This paper presents a new method of dynamic shaft torque measurement using polyvinylidene fluoride (PVDF) films, one of the new polymer type piezoelectric conversion materials. The measurement method is based on the shear strain gradient and the flexoelectric torsional response of the PVDF films. The loading rate-dependent hysteresis associated with viscoelastic behavior of PVDF film was modeled to estimate the torque input. The torque estimated by the proposed hysteresis model and optimization algorithm (genetic algorithm) can be implemented by the discrete Kalman filter. Because the torque estimated by the real-time Kalman filtering matches well with the actual torque input measured by the commercial in-line torque transducer, a new method of sensing the dynamic shaft torque using the PVDF output signal has been experimentally validated. This study offers potential applications for the development of new torque sensing technology to be widely used in a variety of mechanical engineering areas such as turbines, rotors, automobiles, and robotics.