Development of high accuracy ultrasonic sensor for robot application.

Abstract

High accuracy ultrasonic sensor is developed. It has the structure of condenser microphone type with thin plastic membrane and has a rapid stand-up of sound impulse because of high damping in membrane, which enables high precision measurement. Theoretical analysis clarified that natural frequency f0 is determined by membrane density, tension and stiffness of air confined in backplate grooves, and that directional characteristics of impulsive sound radiation and reflection is approximated by the square of that of ordinary sound. In case of a developed sensor f0=118 kHz and half bandwidth 6° are obtained. A new measuring method is adopted, where the distance to the object is calculated by sound reflection time which is measured from 0-cross point of sound wave, and azimuth is measured by the angle indicating maximum amplitude. The measuring accuracy of 0.1mm for distance and 0.1°for azimuth have been accomplished. By rotational scanning of sensor the characteristic point of an object can be known and it gives the informations of its shape, position and orientation. Experimental results showed that the object of some complicated shape can be recognized, which suggest its applicability to robot.