A new position sensor using a triangularly shaped piezoelectric PVDF film

This paper describes a novel tip position sensor for a cantilever beam made of a triangularly shaped distributed piezoelectric PVDF (polyvinylidene fluoride) film. Due to the boundary condition of the cantilever beam and the spatial sensitivity function of the distributed PVDF sensor, the charge output of the PVDF sensor can be shown to be proportional to the tip position of the beam. Experimental result using the triangular PVDF sensor were compared with those using two commercially available position sensors: an inductive sensor and an accelerometer (after double integration). The resonance frequencies of the test beam, measured using the PVDF sensor, matched well with those measured with the two commercial sensors and the PVDF sensor also showed good coherence over wide frequency range, whereas the inductive sensor became poor above 300Hz. However, the measured response of the PVDF sensor showed a bit larger magnitude compared with the two commercial sensors at higher frequencies. The triangular PVDF sensor have a number of advantages over conventional position sensors and could be used as tip position sensors.