Abstract
This paper presents an approach to compensate for the effect of thermal expansion on the structure of an industrial robot and thus to reduce the repeatability difference of the robot in cold and warm conditions. In contrast to previous research in this area that deals with absolute accuracy, this article is focused on determining achievable repeatability. To unify and to increase the robot repeatability, the measurements with highly accurate sensors were performed under different conditions on an industrial robot ABB IRB1200, which was equipped with thermal sensors, mounted on a pre-defined position around joints. The performed measurements allowed to implement a temperature-based prediction model of the end effector positioning error. Subsequent tests have shown that the implemented model used for the error compensation proved to be highly effective. Using the methodology presented in this article, the impact of drift can be reduced by up to 89.9%. A robot upgraded with a compensation principle described in this article does not have to be warmed up as it works with the same low repeatability error in the entire range of the achievable temperatures.
Highlights
IntroductionFor a common industrial angular six-axis robot with a load capacity of up to 10 kg, a repeatability value of 0.025 mm is achievable
The measurements were performed under different conditions, such as different Tool Center Point (TCP) speeds measurements were performed under different conditions, asofdifferent
The results of the presented measurements indicate the usefulness of the developed compensation methodology since it significantly improves repeatability
Summary
For a common industrial angular six-axis robot with a load capacity of up to 10 kg, a repeatability value of 0.025 mm is achievable. The greatest one is the drift, caused by thermal expansion It is the reason why, for many applications, robots must be pre-warmed before production can be started. The thermal expansion and its effect on repeatability is an issue accompanying any high precision device, and there are solutions that describe possible compensation and calibration methods. Among the commercially available solutions, there can be found an AccuBeam: Robot Temperature Compensation system It uses a twin beam laser and a rugged industrial sensor. For special robot applications, such as honing of boreholes, Wiest AG offers an industrial solution of continuous compensation of the robot temperature drift with the help of the measuring technique LaserLAB [3]. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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