Estimation of thermal influence on 2D positioning error of a SCARA-type robot over the entire workspace   Kandai Kawano, Soichi Ibaraki       Abstract   Recently, demand for higher absolute positioning accuracy of a robot has been increasing in order to save cost and time for teach-in operations, and to apply it to new applications such as machining operations. Many research works reported that a robot’s positioning accuracy can significantly change at different days. This paper first experimentally shows that the change in the 2D positioning error of a SCARA-type robot is caused by the thermal influence on the lengths of the two links. Then, we propose a new method to identify the robot’s link lengths by positioning the robot at a set of two points that are apart to each other by the precalibrated distance. This paper presents a scheme to measure the distance between the two points by using a laser tracker. Then, by estimating the influence of the change in the link lengths on the 2D positioning error, the thermal influence on the 2D positioning error can be compensated over the entire workspace.   Keywords: Thermal error, SCARA-type robot, Absolute positioning accuracy         >> Back to Home