A Laser Tracking System to Measure Position and Orientation of Robot End Effectors Under Motion

This article describes a laser tracking system (LTS) that can be used to determine the position and orientation of a robot's end effector with high accuracy during arbitrary robot motions. The position is measured using a polar configuration employing one laser beam and two rotary axes. A retroreflector in the robot end effector reflects the laser beam and constitutes the only part the robot has to carry for the contactless measurement. The orientation is determined by analyzing the intensity profile of the reflected laser beam with a vision system. The intensity profile carries diffraction patterns of the retroreflector edges that uniquely define orientation. The tracking unit allows the system to follow arbitrary movements of the robot. With these characteristics a six-degree-of-freedom (6-DOF) real-time robot measurement system is provided that can dynamically track robot motions.