A microfabricated three-degree-of-freedom parallel mechanism

A microfabricated, three-degree-of-freedom, passive, closed-chain, planar mechanism with the potential for low-torque precision positioning applications is presented. A parallel-link mechanism design is selected rather than a serial-link implementation, since parallel-link mechanisms can operate with stationary actuators and are more rigid than their serial counterparts. Polysilicon surface micromachining is used to fabricate a mechanism which has a total area of 0.13 mm/sup 2/ and a workspace of approximately 0.01 mm/sup 2/. The fabrication process for the mechanism is described, identifying the effect on device performance of constraints imposed by the microfabrication; most notably joint clearances, component nonplanarity, and residual-stress-induced linkage deformations. The requisite formulations for the kinematics and dynamics of the device are presented which, in conjunction with the documented measurements of friction on structures of similar geometry and material, indicate that the dominant torque loads are due to friction.<
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