Vision-based kinematic calibration of an H4 parallel mechanism: practical accuracies

In this article, we present the kinematic calibration of a H4 parallel robot using a vision-based measuring device. Calibration is performed according to the inverse kinematic model method, using first the design model then a model developed for calibration purpose. To do so, the end-effector pose has to be measured with the utterst accuracy. Thus, we first evaluate the practical accuracy of our vision-based measuring system to have a precision in the order of magnitude of 10μm and 10−3deg. Second, we calibrate the robot using our vision system, yielding a final positioning accuracy of the end-effector lower than 0.5mm.