Ultrasonic PVF₂ transducers for sensing tactile force

Abstract

A small flexible tactile force sensor suitable for mounting on the thumb or fingers uses ultrasound to measure the amount of compression in a thin rubber layer. Normal forces in the range of 0.3 to 12 N exerted on a 4 × 4 mm area can be measured. A dynamic response up to 10 Hz is demonstrated and much higher response rates up to 200 Hz are possible. The sensor is based on using piezoelectric plastic film to measure the amount of compression of a 1.5 mm thick rubber array element by detecting the time-of-flight of an ultrasonic pressure pulse in the rubber. The sensor construction and the electronics to generate and measure ultrasonic pulses are described. Preliminary data on the linearity, hysteresis and dynamic response of a two-element array are presented.