Solution to preserve correspondence of measurement and light source using multiple simultaneously with MAPS

A constantly growing demand for high-precision components for special applications requires ever more precise and flexible machine tools. As a result, industrial robots are often used. Despite their versatility, their precision and accuracy may not be sufficient for certain tasks. For example, high accuracy is required for the manufacturing of free form optics or ultra precision mirrors. Even small errors in the optical surface can cause an unacceptable imaging error. Various techniques to improve this are already state of the Art. Tracking the robot’s end effector with an external measuring device is frequently used to calibrate or correct the robot during its operation. The Multi-Aperture Positioning System (MAPS) is one of the measuring devices capable of doing so. With MAPS, the position and orientation of multiple coordinate systems can be measured simultaneously. The position of an end effector can be tracked online by attaching a light source-based target to it. The orientation, on the other hand, could previously only be calculated when the machine was stationary. The positions of three LEDs are required for this. The challenge is to measure the three positions and find the correspondence between each measurement and the respective light source. The current solution to this problem is to modulate the LEDs in time. These are switched on and measured one after the other. If the machine is in motion, this would lead to a spatial offset between the measurements. If, on the other hand, they are all switched on at the same time, the relationship between the light source and the measured value is lost. This is because the spots in the image can no longer be distinguished from each other and overshadow the markers. This article presents a new approach to ensure correspondence between the light source and the measured value when the LEDs are switched on at simultaneously. In this method, the light sources are labeled with a shape that is transferred to the image. An algorithm for separating the spot sets and a newly developed LED target are presented. This method enables MAPS to measure the end effector of machines such as robots in 6DOF while they are moving.