Analytical review of approaches to ensuring positioning accuracy of industrial robots in welding operations

Abstract

The article summarizes modern approaches to ensuring the accuracy of positioning of industrial robots in robotic welding. The purpose of the work is a comparative analysis of the repeatability and absolute accuracy of manipulators, as well as factors that determine the deviation of the tool trajectory in real conditions of the welding process. The study is of a review-analytical nature and is based on a systematic analysis of scientific publications, international standards and open technical documentation of leading manufacturers of industrial robots. It is shown that the passport repeatability does not fully reflect the actual welding accuracy, since the real TCP displacement is formed under the combined influence of kinematic, thermal, dynamic and sensor factors. The main sources of error are systematized and the feasibility of dividing them into four groups is established: kinematic, thermal, dynamic and sensor. A generalization of the literature data showed that an increase in temperature in the welding zone by 10-30 °C can cause a shift in the tool trajectory by 0.1-0.5 mm, depending on the length of the manipulator working arm. Within the framework of the generalized computational analysis, it is shown that under moderate conditions the total positioning error can be about 0.24 mm, and during intensive welding it can increase to about 0.50 mm, with the share of the thermal component being one of the dominant ones. The technical solutions used by leading manufacturers are analyzed, in particular kinematic calibration, dynamic motion compensation algorithms, machine vision, adaptive seam tracking and digital trajectory verification. It is substantiated that the most appropriate approach for increasing positioning accuracy is a comprehensive approach that combines calibration, sensor correction, temperature compensation and digital means of process validation. The obtained generalizations can be used for a well-founded choice of technical solutions during the design, configuration, and modernization of robotic welding complexes.