Error Analysis of Robotic Assembly System Based on Screw Theory

Assembly errors have great Influence on assembly quality in robotic assembly systems. Error analysis is directed to the propagations and accumula-tions of various errors and their effect on assembly success. Using the screw coordinates, assembly errors are represented as "error twist", the extremely compact expression. According to the law of screw composition, relative position and orientation errors of mating parts are computed and the necessary condition of assembly success is concluded. A new simple method for measuring assembly errors is also proposed based on the transformation law of a screw. Because of the compact representation of error, the model presented for error analysis can be applied to various part-mating types and especially useful for error analysis of complexity assembly.