Development of low cost PVDF pressure sensors for sensing the motion of a robot fish

This study aims to develop a low cost pressure sensor for a robot fish to sense its environmental features. Tiny pressure changes surrounding a robot fish need to be understood for the robot to dodge and or to react. A design which is based on Polyvinylidene Fluoride, PVDF, film and a small charge amplifier circuit is proposed in this work. Compared to piezo ceramic, PVDF has lower acoustic impedance and higher sensitivity. The capacitor of the charge amplifier plays an important factor of the design of the sensor sensitivity and the cut-off frequency. The charge source is from compressive stress of PVDF. Experimental results show that the sensitivity of the PVDF sensor were 0.071mV/pa with 10 pF capacitor. A robot fish of 80 cm body length with flexible tail swimming in a water tank was used as a vibrating pressure source. The tail motion can be detected and the tail position can be located by the PVDF pressure sensors in a range of 25cm when the tail oscillated at a fixed frequency.