On Accurate Modeling Of Tensural Muiltistable Compliant Mechanisms

Compliant mechanisms are a new type of mechanism that transfers or converts motion,force and energy through elastic deformation of materials.Through 30 years of development,compliant mechanism has become an important branch of modern mechanisms.Multistable mechanisms are a kind of compliant mechanisms with special functions.?n addition to the advantages of the compliant mechanism,they can maintain several distinct positions.?n recent years,multistable mechanisms have been used in jumping mechanisms of robots,vibration energy harvesting,reconfigurable metamaterials,threshold acceleration sensing,and so on,showing a high value in practical applications.Usually,multistable mechanisms make use of the nonlinear deflection behaviors,such as the stress rigidity of the compliant segments and the nonlinear curvature,which makes them very difficult to be model accurately.At present,the commonly used methods such as elliptic integral solutions,the pseudo-rigid body model are not well suited for the modeling the multistable mechanisms,especially the multistable mechanisms utilizing tensural segments.Tensural segments are loaded in tension during the bistable switching process,thus the problems such as the asymmetric jump and unpredictable bistable behaviors associated with bucking can be avoided.Therefore,this paper is mainly focused on modeling of full compliant multistable mechanisms with tensural segments.Based on the beam constraint model and the chained beam constraint model,two kinetostatic models are developed for double-tensural bistable mechanisms.By comparing to the finite element results,it is found that both the model ? and model ? well predict the bistability and the kinematic behaviors of the mechanisms.Although model ? is a little more complicated than model ?,it significantly improves the modeling accuracy,especially at the negative stiffness region of the kinetostatic curve.In order to expand the design space of bistable mechanism with tensural segments,a novel configuration of bistable mechanism called tensural-compresural bistable mechanism is proposed.Two kinetostatic models are developed by using the beam constraint model and the chained constraint model,respectively.The results show that both model ? and model ? successfully predict the bistable behaviors of the mechanisms,but model ? is more accurate.Several designs accompanied with a prototype of 3D printing are presented to demonstrate the feasibility of the new bistable configuration and the use of the two kinetostatic models.On the basis of the above kinetostatic model,a simple sensitivity analysis and uncertainty analysis method based on Monte Carlo method is given for the tensural-compresural bistable mechanism,which accurately predicts the variations of the performances of the mechanism due to parameters' variations.The results are helpful for the robustness design of the mechanism and provides improving the micro-fabrication processes.Finally,a novel fully compliant tristable mechanism based on the tensural-compresural bistable mechanism is proposed.On the basis of the derivation of its motion statics model,two tristable mechanisms are designed.The kinetostatic model accurately predicts the tristable behaviors of the mechanisms,and the results are further verified by the finite element analysis.A prototype was designed by 3D,and its steady state characteristics were successfully demonstrated.