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

Presents the kinematic calibration of an H4 parallel prototype 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 (i.e. position and orientation) has to be measured with the utmost accuracy. Thus, first the practical accuracy of the low-cost vision-based measuring system is evaluated to have a precision in the order of magnitude of 10 mum and 10(-3degrees) for a 1,024 x 768 pixel CCD camera. Second, the prototype is calibrated using the easy-to-install vision system, yielding a final positioning accuracy of the end-effector reduced from more than 1 cm down to less than 0.5 mm. Also provides a discussion on the use of such a method on commercial systems.