Design Of Compliant Multistable Mechanisms Based On Beam Buckling Characteristics

The compliant multistable mechanism is a special type of compliant mechanism that can be stabilized in multiple equilibrium positions within a certain range of motion,and maintains the steady state without additional energy consumption.Multistable mechanisms are often used in mechanical systems to act as switches,valves and other components.In recent years,they have played a huge role in the field of robotics.With the development of society,the application becomes more and more extensive.However,the existing multistable mechanisms are mostly obtained by the combination of bistable mechanisms,and the mechanism structure is complicated,the volume is large,and it is not conducive to processing.In order to overcome these shortcomings,this paper designs a compliant multistable mechanism based on the buckling characteristics of the beam,and proposes two compliant multistable mechanisms with simple structure,convenient processing and easy realization of functions.The main work is as follows:(1)For a single plane large deformation beam,the relationship between the displacement and load of the midpoint of the large deformation beam hinged at both ends is solved by the analytical elliptic integral method,and the post-buckling equilibrium path of the beam is analyzed.The solution results prove that two buckling forms that are symmetrical about the axis of the undeformed beam will be produced when the beam buckles.The analogy method shows that beams with different geometric boundary conditions also have the same properties.(2)Based on the energy method,the theoretical models of parallel beams and orthogonal beams are established respectively.By establishing the geometric relationship between the beams,combined with the chain beam constraint model,the displacement and load of each node are solved.Use the single beam energy formula to find the total energy of the entire mechanism.Based on the principle of minimum energy,the energy of the mechanism is optimized,and the positions corresponding to each beam when the energy is minimum are optimized.And through the comparison with the finite element simulation results,the correctness of the theoretical model is verified.(3)A state non-sequential compliant tristable mechanism is designed.Since the current stable state jumps of compliant tristable mechanisms are sequential,this type of mechanism cannot achieve mutual jumps between any two states.In order to overcome this limitation,based on the parallel beams mechanism and the kinematic statics characteristics of the Vshaped bistable mechanism,a comprehensive design of a compliant tristable mechanism is designed.The geometric parameters of the proposed mechanism are optimized by the theoretical model of parallel beams and V-shaped bistable mechanism,and a compliant mechanism with three stable positions is obtained.The experimental prototype was processed and an experimental platform was built to complete the functional verification and steady-state position measurement of the tristable mechanism.Experiments show that the tristable mechanism can achieve the expected function and reach the specified steady-state position.(4)A bistable mechanism with variable modes is designed.Based on the orthogonal beams mechanism and the kinematic statics characteristics of the V-shaped bistable mechanism,a variable-mode bistable mechanism is comprehensively designed.The geometric parameters of the proposed mechanism are optimized by the theoretical model of orthogonal beams and V-shaped bistable mechanism,and compliant mechanisms with two stable positions in different modes are obtained.The experimental prototype was processed and the experimental platform was built,and the functional verification and steady-state position measurement of the variable-mode bistable mechanism were completed.Experiments show that the bistable mechanism can achieve the expected function and reach the specified steady-state position.