Visually servoed microspositioning for assembly of hybrid MEMS: theory and experiments

In order for hybrid microelectromechanical systems (MEMS) to become an economically viable technology, these devices must be automatically assembled. Development of automatic assembly strategies requires that the following two issues be addressed: (1) extreme high relative positioning accuracy must be achieved, and (2) the vastly different microphysics that govern part interactions at micron scales must be compensated. Both of these differences suggest the need to use assembly strategies guided by real-time sensor feedback provided in the task frame. In this paper we present experimental results that investigate the use of high resolution optical systems for micropositioning. Task-based sensor feedback is provided by an optical microscope. A visual servoing system is formulated by modeling the microscope optics and using an optimal control strategy. Experimental results demonstrate visually servoed motion at speeds of up to 2 mm/s with a repeatability of 0.17 μm are achieved. The ability to servo over large distances with submicron repeatability is made possible by the use of a unique formulation of the image Jacobian for an optical microscope