Innovative XY-theta platform held by a serial redundant arm

This paper presents a XV-theta micrometric platform, which is extremely compact and offers a wide 300×300 mm workspace. The novelty is that the platform is hold by a serial kinematic chain of four revolute joints, constituting a redundant robot. Each point of the platform can be positioned under a vertical axis with a final error less than two μm in a two-step approach: in a coarse positioning mode, the four axes are controlled to position and orientate the object with an error less than five μm; in a fine mode, two axes are mechanically blocked while two others are controlled to reduce the final error below two μm. The choice of the blocked and moving axes depend on the lever arm length and the mechanism is designed to optimise the link lengths to reduce the final error.