Optical real time orientation measurement of moving targets

Abstract

In industrial applications of robots the real position and orientation of the end-effector is a critical point to provide high quality products. As the mechanics of industrial robots consists of joints, links, motors, and in many cases also of gears, their absolute accuracy is not as good as it should be. Calibration models and methods are developed to identify the parameters of robots. Their application to bring the absolute accuracy of robots into the area of their repeatability needs accurate measurement data of the position and orientation of the end-effector. To find parameters that result from dynamic motions of the robot, the pose of the end-effector has to be measured under motion. In the course of this work the mechanical design of a laser tracking system is introduced which can measure the position of a corner cube with an accuracy of 50#mu#m/m. The laser tracking system is the basis of two different systems to measure the orientation of a corner cube. These two orientation measurement systems are developed in this thesis. The first system uses the method that was introduced 1992 by Dr. Prenninger. The pattern that is included in the expanded laser beam that was reflected by a corner cube is recorded with CCD-line scan sensors and analyzed by correlation. The measurement accuracy would be around 2 arcseconds. The second method to detect the orientation of a corner cube uses the principle of the corner cube to reflect an incoming light beam back to its source. The reflection consists of three single reflections on the three plane mirrors of the corner cube. The three reflection points have a unique relation to the orientation of the corner cube. The detection of these reflection points allows to compute the three orientation angles of the corner cube.