Design Modeling And Performance Analysis Of Large Stroke Cross-spring Flexure Pivot

In recent years,with the increasing of the application of compliant mechanism,the design research of flexure pivot are facing challenges because the demand of large stroke flexure pivot is urgently needed to achieve.And it is in urgent need of theoretical breakthrough and structural innovation,so as to face more application scenarios and realize higher performance requirements.Large angle stroke generally corresponds to high rotational stiffness and low load capacity in the design process of flexure pivot.Simultaneous realization of low rotational stiffness,large angle and high load has become the problem that researchers are trying to overcome.In view of this situation,this paper studies the design and theoretical modeling of large stroke flexure pivot about the spring structure types and the multi-cross symmetric combination configuration.In order to improve the performance of flexure pivots by changing the topological structure of spring,the stiffness characteristics of plane compliant beams were analyzed.Based on the plane curvature theory of beams,the nonlinear deformation analysis models of two kinds of arc curved beams and three kinds of straight beams with variable section were derived.In order to meet more application situations,a universal multi-cross spring flexure pivot numerical analysis model was established.On the basis of that,the geometric conditions of zero-axis-drift configuration were analyzed,and an analysis model that fitting for preliminary design stage was obtained based on zero-axis-drift configuration.The proposed theory was used to analyze the comprehensive performance of a multicrossed-spring flexure pivot.Aiming at the performance requirement of improving the flexure pivot stroke,several groups of optimal geometric parameters were obtained,and the mechanism design and performance improvement of multi-crossedspring flexure pivot with large stroke were realized.The main research contents are as follows:(1)Modeling of geometric nonlinear with typical planar compliant beams.In order to analyze the deformation characteristics of different spring topological structures,the geometric nonlinear analysis models of slender and short arc curved beam spring were derived based on the beam constraint model,and the equations of deformation and stress at any point of the beam were obtained.Based on the chain beam constraint model,three kinds of mechanical analysis models for large deformation of typical straight beams with variable cross-section are established.(2)Configuration design and modeling of multi-cross spring flexure pivot.In order to investigate the constraint characteristics of symmetric configurations of different multiple-cross-springs flexure pivot,a general mathematical formula for symmetric configurations of multiple-cross-springs flexure pivot was established,which considered both layout parameters and geometric parameters.And the design dimension constraints of curvature springs and the geometric realization conditions of zero-axis drift configurations were given.Two kinds of flexure pivot’s mechanical analysis models were established for different design stages,and split flexure pivot specimens were designed and manufactured.The accuracy of the theoretical model was verified by combining experimental tests and finite element simulation calculation.(3)Comprehensive performance analysis of multi-cross-spring flexure pivot.Combined with the established typical planar compliant beam model,the effects of geometric parameters and interference loads on the rotational stiffness,deformation stress and precision characteristics of the three-crossed-spring flexure pivot were analyzed.The zero stiffness and negative stiffness characteristics of the flexure pivot of curved beam were revealed,and the performance differences of the flexure pivot of uniform straight beam,curved beam and multi-cross spring were comprehensively compared.(4)Design and modeling of composite beam deformation element.Four kinds of composite beam deformation element structures were designed.According to the different combination design scheme and its evolution structure,the unified parameter definition and quantitative description were carried out,and the mechanical model of double beam combined and three beam combined deformation element were established.