| References about kinematic calibration of industrial robots can be found in scientific literature over the last twenty years. However, just a few are based in measurements in robots, being most of them simulations of results of several calibration procedures. On the other hand, in many of the cases where experimental measurements have been performed, just a local calibration has been obtained (due partially to limitations of the measurement procedure used), where the mathematical model obtained is adjusted quite well to a set of measurements carried out on a limited volume inside the robot workspace, but failing the model accuracy outside of the volume where the points used for calibration purposes were defined.; In the first place, in this thesis an experimental tool to be used for calibration purposes and also control of robot performance has been adjusted. More specifically, it is a laser tracking system based on triangulation. Special attention has been put into quality of measurements performed, increasing accuracy of the measuring system by means of substituting the original model of guidance of the laser beam by one more complete.; In second place, two global kinematic calibration procedures has been compared, trying to find the mathematical model which describes the real robot geometry, so it should enhance the robot accuracy in the whole workspace. The geometrical model has been developed using two different levels of complexity. The simplest one includes only geometrical parameters in its composition, whereas the other one incorporates non geometrical parameters, such as the error in the transmissions and the elastic deformations in the two joints of the robot where those deformations can get to be significant. Using these models it has been possible to evaluate the influence of these non geometrical parameters as opposed to the influence of the geometrical parameters on the precision of the robot.; In the last place a brief review of the limitations of kinematic calibration procedure is included, observing how the precision of the robot decreases when working at high speed, due to the dynamic effects that appear. |
