Research On Cross-scale Micro-gripper Based On Multi-stable Compliant Mechanism

Micro-gripper is a typical end effector in the field of micro-manipulation.The traditional micro-gripper structure has problems such as small stroke,low precision,and inability to grip objects across scales(?m-mm).In view of the above problems,this thesis proposes a microgripper structure based on the combination of a multi-stable flexible mechanism and a traditional amplification mechanism.The design of multi-stable flexible mechanism and amplification mechanism,optimization of structural parameters,theoretical modeling and simulation analysis are studied.Firstly,the characteristics and common analysis methods of the multi-stable flexible mechanism are analyzed,and the topological configuration of the micro-gripper based on the multi-stable mechanism is studied,including bistable series,nesting and connecting with the slider link and other configurations and its force-displacement relationship is analyzed.Finally,a new multi-stable mechanism with multi-stage parallel combination is proposed and its output displacement is theoretically analyzed.Considering comprehensively,this thesis adopts the bistable mechanism in series to realize the cross-scale of micro-gripper.Secondly,the single bistable mechanism in serial multi-stable mechanism of the microgripper is designed,and its theoretical model is established,including beam constraint model,pseudo-rigid body model and numerical model.Orthogonal simulation test design of bistable mechanism is carried out.Based on the orthogonal test,gray wolf algorithm is used to optimize the structure,and finally a three-section bistable structure is successfully designed.The "tri-root bistable function" proposed in the numerical model are used to represent the complete nonlinear bistable force-displacement characteristics,according to the function,the snap-through threshold value of the bistable is obtained and then the finite element simulation is carried out to verify the accuracy of the above model.Thirdly,the overall structure design of the cross-scale micro-gripper is proposed,namely the multi-stable mechanism is combined with the traditional amplification mechanism.The lever mechanism and parallelogram mechanism are used on the left side of the microgripper,and the parallelogram mechanism ensures that the output of the microgripper end is purely parallel.Three different bistable mechanisms are used in series to achieve eight stable states on the right side,and specific analysis is made for the clamping method,parallel guiding mechanism,flexible hinge and so on.The theoretical modeling of the left magnifying mechanism of the micro-gripper is carried out to deduce the magnification,and the simulation of the right series multi-stable mechanism is carried out to verify its steady-state characteristics and span displacement.Finally,on the basis of the above theoretical and simulation research,an enlarged version of the micro-gripper was fabricated and a preliminary demonstration experiment was carried out to verify the rationality of the multi-stable mechanism for cross-scale clamping of the micro-gripper.The results show that the flexible multi-stable micro-gripper designed in this paper has a large effective clamping displacement range,high magnification,compact structure,and can realize cross-scale parallel clamping of ?m-mm.