Mechanism reliability of bistable compliant mechanisms considering degradation and uncertainties: Modeling and evaluation method

The bistable compliant mechanism has been widely used in the field of micro-electromechanical systems, industrial lines, and daily necessities. Enhancing mechanism reliability is helpful to prolong product life and to reduce the maintenance costs of bistable compliant mechanisms. This paper proposes one method to evaluate the mechanism reliability of the bistable compliant mechanism considering degradation and uncertainties of the parameters. The new method can be subdivided as follows: first, the pseudo-rigid body model is used to calculate the motion precision of the mechanism. Second, by introducing the degradation of stiffness and the randomness of the bending line into the kinematic equations, the other equilibrium position can be calculated with respect to the service duration. Third, by using the health index to judge the status of the mechanism, a large sample of failure time is generated and processed by the Kaplan-Meier estimator to characterize the mechanism reliability of the bistable compliant mechanism. A case studied in this paper reveals the mechanism reliability of a typical bistable compliant mechanism under different health indices and provides clues for the reliability evaluation and performance improvement of bistable compliant mechanisms.