Abstract: Multistable mechanisms can stay at multiple stable equilibrium positions without power input, and get more and more widely use in many regions. Fully compliant multistable mechanisms have some advantages such as free of assembly, frictionless, lower power consumption, and so on, but they are difficult to design because of the stress concentration and nonlinear characteristics caused by the large deformation of the flexible segments. A design approach is presented for a type of fully compliant sexastable mechanism, which possesses six stable equilibrium positions, employing a compliant structure and two compliant bistable mechanisms with different snap-through forces. The model of the compliant structure is built by pseudo-rigid-body model to achieve the force-deflection characteristics. The force-deflection curves of the two components are compared to obtain the stability criterion for the sexastable mechanism, avoiding nonlinear analysis. Formulas are proposed to determine the stiffness arrange of the flexible segments of the compliant structure, which is the basis of the size parameters design for the flexible segments. A design example is given and the finite element analysis by ANSYS software and the prototype test prove the feasibility of this design approach.

Key words: fully compliant mechanism, multistable mechanism, pseudo-rigid-body model