Design and development of robotic end-effector position measuring device

Abstract

Robot end-effector position measurement is very essential to determine the error between the commanded position and actual position reached by the robot end-effector. This also ensures the error with which the robot end-effector traces the commanded path. Conventionally position measuring devices like laser trackers, coordinate measuring machine and other non-contact-based position measuring devices are widely used to measure the position of the end-effector due to their high accuracy and precision, even though they are very expensive. This paper presents a cost effective solution for the measurement of position of robot end-effector. An end-effector position measuring device is designed and developed in spherical coordinate system using two absolute rotary encoders and a draw-wire sensor. A mathematical model for the end effector position measuring device is developed to determine the position of the end-effector with respect to a reference coordinate system using 3D homogeneous transformation approach. End-effector position measuring device is tested for ABB IRB 1600 for numerous poses and for a straight line path. The newly developed end-effector position measuring device is found to be capable of measuring the end effector position with an accuracy of 2 mm and hence can be implemented in calibration of industrial robots.