Ultrasonic Proximity Sensor for Profile Following Work by Robot Manipulators

Abstract

In the field of profile following works by robot manipulators, a sensory feedback controller using the proximity information can reduce the setting errors and simplify the teaching works. Then it is necessary to develop the proximity sensor which can measure the relative posotion/orientation of the endeffector and objective surface.This paper proposes a new ultrasonic proximity sensor for measurements of the hand orientation against an object. For three dimensional applications, a method is presented which obtain the two directional angles of the line normal to the surface. The method uses the mutual phase difference between the reflected echoes of three receivers arranged in encircling the transmitter.The sensing system can be developed using commercially available transducers. And it has many advantages as high resolution, wide measuring range, simple structure, light weight and so on. The sensing system is suitable for the proximity sensor attached to the hand of robot manipulators.The principle using the phase difference is useful for measurements and controls by a null method. Then, the sensing system is applied to the control system which maintain the direction of hand normal to an objective surface.Experiments using typical wrist mechanisms show the effectiveness of the sensory feedback system. They also show the applicability of the sensing system to profile following works.