Innovative Design And Performance Analysis Of Fully Symmetric Cross-spring Flexure Hinge

As the core component of compliant mechanisms,flexure hinges realize relative rotation of two rigid bodies through elastic bending deformation with the advantages of compact structure and no frictional loss.At present,the most important and difficult problem in the research of leaf spring hingeis how to improve the rotational performance.The inconsistent deformation of leaf springs of traditional cross-spring flexure hinges during rotation leads to center shift and warping,which cannot ensurerotation accuracy.To restrain center shift and warping,a fully symmetrical N-cross-spring flexure hinge was designed.The main research contents are as follows:(1)A new type of cross-spring flexure hinge is designed.The principles of“Merging”,“Symmetry”,and “The other way round” of leaf spring hinges in restraining center shift and warping are analyzed and summarized.The structural design imperfections of the existing leaf spring hinges are pointed out.Based on the structural characteristics of spring-type flexure hinge and the principle of “Another dimension”,a design method named “Reverse Parallel Connection”(RPC)for structural design of a cross-spring flexure hinge is proposed.Based on the method,a new N-cross-spring(FSNCS)flexure hinge was designed,which has fully symmetrical structure characteristics and can better overcome center shift and warping.(2)The rotational performance of fully symmetrical three-cross-spring(FSTCS)flexure hinge flexure hinges is calculated and analyzed by theoretical modeling.Taking FSTCS flexure hinge as an example,based on beam restraint model and related elastic mechanics knowledge,the theoretical model of rotational stiffness and rotationaccuracy is established.The changerules of rotational stiffness and rotation accuracy of FSTCS flexure hinge under driving torque are studied,and the influence of tangential load and radial load on rotational performance is analyzed.(3)The finite element simulation of the rotational performance of FSTCS flexure hinge is carried out.Taking FSTCS flexure hinge as an example,the finite element model of FSTCS flexure hinge is established by using finite element analysis software HyperMesh and Abaqus.Considering different external load conditions,the change rules of rotational stiffness and rotation accuracy under driving torque are studied and analyzed under non-interference,tangential load interference and radial load interference.The results are compared with those of the theoretical model.(4)The rotational performance of FSTCS flexure hinges was tested experimentally.The rotational stiffness test platform was designed and built.Two processing schemes,namely layered manufacturing and assembly,and integrated manufacturing,are used to test the rotational stiffness of FSTCS flexure hinge.The test results were basically consistent with the theoretical model calculation and finite element simulation,which verified the accuracy of the theoretical model.The analysis shows that FSTCS flexure hinge always maintains the dynamic symmetry of the structure under load.Under the pure torque,the rotational stiffness is a quasi-constant within a certain angle range and the rotation accuracy reaches the level of quasi-zero center shift.when subjected to circumferential load disturbance,the rotation stiffness does not change,but the rotation precision decreases,and the axle drift increases with the increase of the rotation angle.when the radial load interferes,the rotation stiffness changes,and the axis drift increases same as the angle of rotation.The theoretical model calculation,finite element simulation and experimental test consistently reflect the excellentperformance of flexure hinge,including large turning angle,high precision,stability stiffness and anti-interference,and the relative error between them is mainlykept within 10%.