Nonlinear kinetostatic modeling of double-tensural fully-compliant bistable mechanisms

In double-tensural fully compliant bistable mechanisms (DTBMs), all of the compliant segments are loaded in tension when deflected, thus the problems associated with buckling are avoided. Because the stiffening of the compliant segments due to tensile loads plays an important role in achieving the bistable behaviors, it is critical to capture the relevant geometric nonlinearities when modeling DTBMs. Based on the beam constraint model (BCM) and the chained beam constraint model (CBCM), two kinetostatic models are developed for DTBMs in this work: Model I models both of the tensural segments using BCM, while Model II models the shorter tensural segment using BCM and the longer tensural segment using CBCM with two BCM elements. The two models well predict the bistability and the kinetostatic behaviors of a DTBM as compared to the finite element results. Although Model II is a little more complicated than Model I, it improves the modeling accuracy, especially at the negative stiffness region of the kinetostatic curve.