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.
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.
Robots are being used in many areas. The robot performance constraints are repeatability and accuracy. Standardized testing and evaluation techniques are needed to examine the process capability of a wide variety of robots. Robot calibration is a term applied to the procedure used in determining actual values which describe the geometric dimensions and mechanical characteristics of a robot. The robot accuracy evaluation method is introduced. The study proposed a technique to analyze robot’s orientation error by using the data measured during circle contouring movement of the articulated robot end effectors. New measuring method is proposed to measure orientation errors. Circle contouring measurements were also undertaken to assess the significance of multi-axis movements on the accuracy of the end effector. The paper describes the experimental and theoretical accuracy characteristics of an articulated robot. Also, the technique devised using a simulation program for the robot geometry, together with results from a circular test, enables robot errors to be characterized in terms of orientation error and volumetric error. Close correlation was obtained between the experimental and theoretical results. Also, robot pose error was shown a significant factor influencing the accuracy of the robot end effector. Proposed techniques are useful to set up the articulated robot in the industrial site.
Steel beam welding at a construction site is challenging due to the increasing thickness of steel members in today's 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.
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