Yeon Taek Oh

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 ...

Robot accuracy evaluation using a ball-bar link system

Relatively large errors can exist in industrial robots as a result of mismatch between the controller model and the corresponding physical model. The paper outlines a novel approach for accuracy assessment and adjustment of multiaxis industrial robots through a low-cost ball-bar link system. The features of the ball-bar, which incorporated a 12 mm range digital displacement transducer in conjunction with a PC, are discussed. The ball-bar device was used in both a trammelling and circular mode of operation. This produced data which not only related to the accuracy of the robot but also enabled joint errors to be significantly reduced.

Portable robotic system for steel H‐beam welding

Steel beam welding at a construction site is challenging due to the increasing thickness of steel members in todays buildings. In order to achieve high quality welding and resolve the problem caused by the shortage of skilled welders, robotic systems are in high demand. We have proposed a practical robotic system for steel beam welding, specifically designed for working on H‐shaped column structures that are known to be the most difficult structures for automation.