Calibration and Implementation of Robot for Detection of X-rays

Abstract: While industrial robots have traditionally been designed for tasks such as pick-and-place that require a high repeatability, an increasing demand for off-line control and high-precision applications have in recent decades put higher demands on the accuracy of robots. One application in that vain is the detection of X-rays that have been scattered from a sample during X-ray diffraction, which produces interference peaks of very well-defined angles. To that end, a robot has been installed at the MAX IV synchrotron facility with the intention of having it maneuvering an X-ray detector, and the aim of this thesis is thus to improve the pose accuracy of the robot to a level that is feasible for conducting such experiments. The robot’s kinematics is calibrated through means of an optical CMM, and the joint characteristics such as backlash, friction, and joint stiffness are identified by performing a clamping routine, where the robot’s end-effector is rigidly fixed to the environment. Furthermore, the calibrated model is implemented off-line in order to facilitate the control of the robot by means of the spherical coordinates that are commonly used in X-ray diffraction. The results show that the calibrated model achieved an accuracy of 180 mm, which is close to the anticipated value of 150 mm. This means that the robot is ready to be taken into operation, even though further attempts at improving the accuracy may be undertaken in the future.