Are Parallel Robots More Accurate Than Serial Robots?

It is widely claimed that parallel robots are intrinsically more accurate than serial robots because their errors are averaged instead of added cumulatively, an assertion which has not been properly addressed in the literature. This paper addresses this void by comparing the kinematic accuracy of two pairs of serial-parallel 2-DOF planar robots. Only input errors are considered and all robots are optimized for accuracy, the only constraint being that they cover a given desired workspace. The results of this comparison seem to confirm that parallel robots are less sensitive to input errors than serial robots. However, this comparison is too limited to draw any general conclusions. Besides, it is virtually impossible to make a meaningful comparison between other pairs of serial and parallel robot. Therefore, there is no simple answer to this question of superiority.