Design of Compliant MEMS Grippers for Micro-Assembly Tasks

Due to their monolithic construction and superior wear and loss properties, flexure joints have been used to reduce the mechanism size and increase the positioning accuracy. The compliance of flexure joints, however, can affect the static and dynamic characteristics of the overall mechanism. To design mechanisms containing flexure joints, we have proposed a multi-objective optimization approach to take into account the multitude of performance metrics and design constraints. A Pareto frontier is first computed, and secondary design criteria, such as sensitivity and dynamic characteristics, are then applied to select the final design. To reduce the computation load and facilitate design iteration, a lumped spring approximation, the Paros-Weisbord model, is used to characterize the flexure joints and the pseudo-rigid-body model is used as an approximate description of mechanisms. This paper presents this approach applied to the design of a micro-gripper. The performance metrics are chosen to be the manipulability of the gripper opening and the decoupling of a stiffness matrix (reflecting the remote center of compliance criterion). Different design and initial fabrication results are included