DESIGN FOR ACCURACY AND REPEATABILITY FOR ROBOTS USING TAGUCHI METHODS

In this paper, we apply Taguchi Methods in the framework of concurrent engineering design for robot-based manufacturing systems to obtain hi gher accuracy and repeatability for robot end-effecters. It is well kn own that the configurations of robot end-effecters in workspace will a ffect the accuracy and repeatability. Taguchi Methods are employed to find the configuration and location within which the accuracy and repe atability are the best. The optimal position with higher accuracy and repeatability is determined by using the signal-to-noise ratios (S/N r atios), which are defined according to the ''smaller-the-better'' char acteristics of Taguchi Methods to measure the accuracy and repeatabili ty. The results match well with the theoretical analysis of the repeat ability and accuracy of the end-effector based on the kinematic relati onship. In addition, we also study the random and systematic errors du e to joint uncertainties and examine their effects on the accuracy and repeatability. The analysis using S/N ratios yields results that are consistent with expectation, The results demonstrate that Taguchi Meth ods and S/N ratios are very useful tools in design for accuracy and re peatability of robotic end-effecters. The sensitivity and consistency of accuracy with respect to the tolerance of joint angles are represen ted by 3D surfaces. The tolerance design is performed, using the sensi tivity analysis, to satisfy requirements stipulated by design criteria , One of the significant results of consistency analysis is the ''thre shold'' value of tolerance for concurrent engineering design considera tions. Simulation results show that the consistency of accuracy and re peatability will be increased dramatically once the tolerance is below such a threshold. Both sensitivity and consistency analysis are shown to be important in tolerance design for achieving the desired accurac y and repeatability and for enhancing quality.