Measuring the Motion: Synchronizing a Laser Tracker for High-Accuracy Handling Tasks

Publication Details

Abstract

The article focuses on synchronizing the position of tool center points (TCPs) of assembly robots with a laser tracker. Up to now, the robot’s trajectories were surveyed solely in a stop-and-go-mode. Because the actual trajectory of an object is needed while it is moving, we have developed a highly accurate survey method that enables optimizing a second robot to execute high-precision handling tasks in precision manufacturing. The task described here is challenging, because the accuracy requirement of mechanical handling is high and, due to the object speed of up to 100 mm per second, it requires a synchronization uncertainty down to 50 µs. Therefore, different synchronization methods will be discussed theoretically. As the standard method will not work, the implementation of an appropriate technique will be demonstrated. In the first application gross errors of the robot control system were verified easily, so that the robot’s function was improved significantly. In the second step, a very high repeatability of the trajectory was detected. In the third step, the implemented method was seen to be suitable for the fine tuning of the robot-bound movements. Furthermore, this article will demonstrate how the measurement set-up can be optimized. Additionally, a preview to the development of a (possibly low-priced) active hub will be given, which will allow for the revertive rotation of the CCR according to the control data of the robot’s rotation.