The Design And Analysis Of Compliant Bistable And Multi-Stable Mechanisms

With the excellent mechanical properties of threshold snap-through and stable state holding capability, the compliant bistable and multi-stable mechanisms have been widely used in the fields of micro-motion, micromanipulation, micro-assembly etc. However, the present mechanisms have some deficiencies such as high driven snapping force, low stable state holding ability and less stable states, which will block their further applications. Therefore, to solve these problems, this thesis mainly includes the following aspects.1. Two methods to improve the bistable performance:reducing the threshold force and increasing the stable state holding force.1) A section reinforced method was proposed to reduce the snap-through force and increase retention force, which includes the following two steps:first, optimize the configuration to lower the snapping force by not changing the maintaining force; second, find an optimized structure to increase the maintaining force and keeping the snapping force unchanged. Then, a low-threshold bistable mechanism with four rigid sections was designed.2) The other way is to change the stiffness at two ends of the beam by adding side beams. And such device was manufactured by the low-cost and convenient micro-electroforming technology on a Si substrate. The rotating flat is employed for the measurement of quasi static threshold value of bistable mechanism and the experimental results were coincide with the simulation results, which adequately validate the design method of low threshold mechanism.2. Two novel methods were proposed to increase the stable states of flexible mech-anisms and corrugated shells.1) a novel structure was designed by serially combining two bistable compliant structures, which has two thresholds through the interaction of two different size of bistable structure.2) a effective method for designing stable states was proposed by varying the thickness at different locations of dimpled shells. First, the effect of the cross section on the mechanical properties of corrugated shell was studied, and found that the tapered shape has the best mechanical properties. Then, a multi-stable structure was proposed based on the mechanism with the tapered section by changing the number and position of the rigid section. The influence of the rigid section number and rigid position on the numbers of configuration of corrugated shell was investigated. The results show that there was a sensitive region, at the where the number of stable configurations can be increased by reinforcing the thickness of the shell.