Stéphane Leleu

Improving the accuracy of industrial robots by offline compensation of joints errors

The use of industrial robots in many fields of industry like prototyping, pre-machining and end milling is limited because of their poor accuracy. Robot joints are mainly responsible for this poor accuracy. The flexibility of robots joints and the kinematic errors in the transmission systems produce a significant position error in the level of the end-effector. This paper presents these two types of joint errors. Identification methods are presented with experimental validation on a 6 axes industrial robot, STAUBLI RX 170 BH. An offline correction method used to improve the accuracy of this robot is validated experimentally.

Methodology to Straighten the End Parts of Long Workpieces

A workpiece is considered as “long” when one dimension is larger than the two others, for example, railways or guides of manufacturing machines. The customers’ requirements’ evolutions asks the question of workpieces end parts straightness. This paper deals with the means to measure and correct the straightness, a way to prevent flaws in adapting the process and it is especially focused on improving quality for the end parts of the long workpiece. At first, to get the right measure of the straightness, we take into account the fact that the workpiece is deformable; consequently, we assumed the hypothesis that the measured straightness is composed of the intrinsic straightness and the elastic one. Then an approach was developed in order to measure any straightness. Secondly, after getting the proof that the measures are reliable; the correction of the straightness has been studied. The method of semi-automated straightening has been developed in order to improve the productivity. Some experiments have been realized and the results have been compared to the theoretical ones. The conclusions will help to find ways to modify the process in order to prevent the flaws of straightness of long workpieces.