ROBOTICS : CONTOURING CONTROL USING VISION FEEDBACK

Abstract

A system that can guide the robot to follow the contour of a given shape using a camera is described. The system consists of a low cost vidicon camera for image capturing, an IBM PC microcomputer for vision processing and communication and a six degree-of-freedom PUMA 560 robot for contour following. The system developed has been tested on several odd shapes with various curvatures and straight lines combinations. The result shows very good agreement between the actual contour and the robot generated contour. The necessary hardware circuit has been designed to interf3ce the video camera to the microcomputer. The processing of the digital image involves segmentation, contour extraction, contour approximation and contour scaling. Information are send to the PUMA controller by emulating its terminal and keyboard functions. The software is written in compiled BASIC with the essential vision algorithm written in 8088 machine codes to achieve an execution speed which is about I 5-20 seconds for contours of 400-800 pixels (extracted from a 200 by 200 image array). Multiple independent contours can also be processed in a single pass. In addition to a one-to-one contour reproduction, contour enlargement, reduction and rotation is also included. The system can be linked to teach and reproduce the profile on any Point-to-Point robot which has provision for straight line motions and should be useful in many practical applications, for example metal cutting, welding, patterns cutting in woodwork, textile industries, etc.