Stochastic linkage model of a compliant bistable micromechanism for mechanical error analysis

Microelectromechanical systems (MEMS) that have micromechanisms as actuators involve inaccuracy problems due to joint clearances and link length tolerances. Since compliant bistable micromechanisms have a wide range of applications in MEMS devices, analysis of the mechanical error of these mechanisms is very important. For compliant mechanisms, it is important to consider the effects of cross-sectional shape and material stiffness variations. In this paper, a compliant bistable micromechanism called Young is modeled by a clearance vector concept. Then a stochastic method is used to determine the errors of potential energy, required moment and coupler point position of mechanism. The range of variations of critical moment of the micromechanism to move from one stable point to the other and the displacement of the second stable point of the mechanism are determined. The Monte Carlo simulation shows that the stochastic method yields accurate results. The clearance vector model is easier and more general to use for micromechanisms than previous works.