Influence of the joint angular characteristics on the accuracy of industrial robots

Purpose - Angular errors in the robot axes can make a significant contribution to robot positioning accuracy. This paper seeks to propose a new measuring method for measuring angular errors.Design methodology approach - New techniques were devised for the detailed investigation of joint angular errors using a reference encoder together with a precision electronic level and autocollimator. This equipment enabled vertical and horizontally orientated joint axes to be measured with the robot located on-site. Circle contouring measurements were also undertaken to assess the significance of multi-axis movements on the accuracy of the end effector.Findings - The technique, devised using a simulation program for the robot geometry with results from a circular test, enables robot errors to be characterised in terms of datum location error, backlash, gear transmission error, axes misalignments and joint encoder offset.Originality value - The paper describes the experimental and theoretical accuracy characteristics of an articulated industrial robot. Close correlation was obtained between the experimental and theoretical results. This paper offers the practical robot calibration method for industrial application.