【作者】 陈鑫；

【导师】 刘江南；

【作者基本信息】 湖南大学 ， 机械工程， 2022， 硕士

【摘要】 近年来,柔性机构的应用不断发展,大行程柔性铰链的需求日益迫切,现有的柔性铰链设计研究面临挑战,亟需理论的再突破和结构的再创新,以面向更多应用场景并满足更高的性能要求。在过去的柔性铰链设计过程中,大转角行程一般对应着高转动刚度和低负载能力,如何同时实现低转动刚度、大转角、高负载成为目前柔性铰链设计研究者正在全力攻克的难题。针对这一现状,本文从簧片拓扑结构类型和多交叉簧片对称组合构型两方面进行大行程柔性铰链的设计与理论建模研究。分析了不同平面柔顺梁的刚度特征,基于平面梁的曲率理论推导了两种等截面圆弧曲梁和三种变截面直梁的非线性变形分析模型,以通过改变簧片拓扑结构提升柔性铰链性能。面向更多应用情境,建立了通用的多交叉簧片柔性铰链数值分析模型,在此基础上分析了零轴漂构型的几何条件,并进一步基于零轴漂构型获得一种适用于初步设计阶段的轴漂解析计算模型。运用所提出理论对一种三交叉曲梁簧片柔性铰链的综合性能进行分析,针对提高柔性铰链行程的性能需求,获得了多组优选几何参数,实现了大行程多交叉簧片柔性铰链的新结构设计和性能提升。主要研究内容如下:(1)典型平面柔顺梁的非线性变形建模。参考梁约束模型的建模过程,推导了细长圆弧曲梁、粗短圆弧曲梁的非线性变形分析模型,得到梁上各点的变形和应力解析计算方程,为不同簧片拓扑结构的变形特性比较提供理论依据。基于链式梁约束模型的建模方法,建立三种典型变截面直梁的大变形力学分析模型。(2)多交叉簧片柔性铰链的构型设计与力学建模。为了探究不同多交叉簧片柔性铰链对称构型的约束特性,建立了综合考虑布局参数和几何参数的多交叉簧片柔性铰链对称构型通用表达式,在此基础上给出了零轴漂构型的几何实现条件和曲率簧片的设计约束;建立了两种适用于不同设计阶段的柔性铰链力学分析模型,设计制造了分体式柔性铰链试件,结合实验测试和有限元仿真计算,验证理论模型的准确性。(3)多交叉簧片柔性铰链综合性能分析。结合已建立的理论,分析了关键设计参数和干扰载荷对两种三交叉簧片柔性铰链的转动刚度、变形应力和轴漂特性的影响;揭示了曲梁簧片柔性铰链的零刚度和负刚度特性,综合对比了均匀直梁、曲梁应用于多交叉簧片柔性铰链设计中的性能差异。(4)组合梁式变形单元设计与建模。采用模块化组合设计理念,设计了四种组合梁式变形单元结构,并针对其不同组合设计方案及其演变结构,进行了统一的参数定义和量化描述,建立了双梁组合式和三梁组合式变形单元力学模型。更多还原

【Abstract】 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.更多还原