Abstract: Due to the strong nonlinearity of the snap-through phenomenon of the multistable mechanism, it is difficult to design and control the multistable characteristics including stable state number, stable positions, snapping threshold and travelling stroke. To solve the design problems caused by the uncontrollable state features of the multistable mechanisms, a novel magnetic-mechanical based multistable mechanism with large travelling stroke is proposed by introducing the spatial arranged magnets to assist the energy storage and release procedure of the mechanical system, with which the local minimal energy positions can be designed by properly incorporating the compliant mechanisms and multi-magnets. Considering the influence of the nonlinear mechanical deformation on the magnetic field distribution, the accurate mathematical model for analyzing the nonlinear snap-through characteristic is established based on the magnetic charged model and the pseudo rigid body model method. Additionally, the influence of the magnetic pole direction, the magnet number and their arrangement on the multistable characteristic is theoretically analyzed, which is validated by the FEM simulation. Accordingly, the energy criterion for the magnetic-mechanical coupled multistability is obtained, thus resulting in the relationship between the real stable state and pseudo stable state. With the prerequisites for multistable features, a novel heptastable mechanism is manufactured. The good consistency between the simulation and experimental results adequately validate the correctness of the proposed model.

Key words: compliant mechanisms, magnetic-mechanical coupling effects, multistability, nonlinear characteristic, snap-through