Research On The Design Method Of Flexure Hinges Based On Origami And Mortise-Tenon Structure

The flexure hinges are important component in compliant mechanisms,the design of flexure hinges is the key to compliant mechanisms.LEMs(Lamina Emergent Mechanisms)hinges are flexure hinges designed and produced from flat sheet materials,and their unique structure and design make them widely used in various industries.At present,the design of LEMs hinges is mostly focused on twodimensional planes,which greatly limits their development and application.To expand the design of LEMs hinges from two-dimensional plane to threedimensional space,this paper proposes a design method of flexure hinges based on origami and mortise-tenon structure.Unlike the design of traditional origami-based mechanism,the focus of this paper is not gathered on the design of complex creases,but focuses on how to design and make permanent creases.Based on the proposed method,variable stiffness flexure hinges,multi-degree-of-freedom flexure hinges and flexible robots are designed,and the modeling and analysis methods of these hinges and robots are thoroughly investigated.The main research contents of the paper is organized as follows:(1)A design method of flexure hinges based on origami and mortise-tenon structure and the concept of Foldable mortise-tenon structure(FMTS)are proposed.The design method completes the arrangement of flexible segments by origami and then makes permanent creases by FMTS.The design method accomplishes the arrangement of flexible segments by origami and the permanent folds by FMTS structure.The design guidelines and key techniques of the FMTS structure are given,and the influence of dimensional parameters on the stiffness of the FMTS structure is explored.The design and fabrication process of the FMTS is described in detail,and the influence of dimensional parameters on the FMTS is explored.The deformation,advantages and disadvantages of FMTS structure and conventional origami structure under the same load are compared.Finally,the feasibility of the proposed design method is verified by theoretical and simulation analysis and experimental tests using the compliant translational joint as an example.(2)Based on the method proposed in(1),a single-degree-of-freedom passive variable stiffness Lamina Emergent joint is designed,which has the characteristic that the stiffness can be changed with the load.The principle of variable stiffness is described,the formula for calculating the dimensions of the block is given,the causes of variable stiffness failure are analyzed,and the key technologies for the design of this hinge are discussed.The theoretical calculations,finite element analysis and experimental tests are used to verify the variable stiffness performance of the hinge and the effectiveness of the design method.(3)Two two-degree-of-freedom flexure hinges are designed based on the method proposed in(1).The first is a two-degree-of-freedom LET(Lamina Emergent torsional)joint,which can achieve rotational motion in two directions,and the other is a two-degree-of-freedom left hinge,which can achieve one rotation and one translational motion.Then theoretical analysis of these two hinges is carried out using equivalent spring model,closed model and comliant matrix method.Finally,finite element analysis is used to verify the correctness of the theoretical analysis and the feasibility of the design for both hinges.(4)A multi-degree-of-freedom flexure hinges is designed based on the method proposed in(1),and the hinge is applied to a flexible continuum robot.The design process of this multi-degree-of-freedom flexible hinge is described in detail,and a theoretical model that can capture its spatial nonlinear deformation is established and verified with finite element analysis.In order to analyze the motion characteristics of the flexible continuum robot,an equivalent pseudo-rigid body model is developed and solved.Finally,the simulation analysis and experimental test of the flexible continuum robot were carried out to verify the correctness of the theoretical analysis model and the validity of the design.(5)An underdriven robot hand is designed based on origami and mortisetenon structure.The stiffness of three joints of the robot hand is finally determined by considering the influence of the joint stiffness on the grasping force,initial posture and grasping posture.For the modeling problem of the internal cable of the cable-driven robot hand,a modeling method that takes into account the internal cable entanglement is proposed,and the motion process of the robot hand grasping the object is analyzed based on this method and verified by simulation analysis.Motion and gripping tests are also performed on the prototype manipulator to further verify the feasibility of the design and the correctness of the theoretical model.The research in this paper can provide new ideas and references for the design of variable stiffness and multi-degree-of-freedom flexure hinges,and play a role in promoting the design of flexible mechanisms.