剪式单元可展结构的自由度及动力学特性研究

发布时间：2018-05-18 08:58

本文选题：剪式单元 + 螺旋理论　；参考：《西北工业大学》2016年博士论文

【摘要】：可展结构具有运动缩放、构型保持的功能,故其广泛应用于航空、航天和建筑等领域。可展结构作为一种特殊的机械结构,能够实现机构与结构等构型的相互转变。组成可展结构的单元有多种类型,具有大收缩比等优点的剪式单元是其最常见的一种类型,并且按照不同的阵列方式可以形成不同的可展结构。但是由剪式单元阵列组合而成的可展结构,是一个具有多闭环和多冗余约束等特点的多体组合结构。正是由于剪式单元可展结构这一复杂的结构特性,所以在其设计和分析中,不仅要研究剪式单元可展结构的型综合等问题,而且还要深入研究其运动学和动力学特性,以及展开到位的构型稳定性。所以,本文对剪式单元可展结构进行自由度和动力学特性的研究,具体的研究工作和创新点如下:(1)提出了剪式单元可展结构的分解和组合方法,并基于螺旋理论建立了剪式单元可展结构自由度的分析计算方法。首先,对剪式单元可展结构进行了结构的分解,分解成一些基本的单元,并根据图论方法绘制约束拓扑几何图,进而基于螺旋理论建立了约束螺旋方程;然后,将基本单元进行组合成原来的可展结构,并根据螺旋理论进行了自由度的计算;最后,再选取两种不同阵列方式的剪式单元可展结构进行自由度计算和仿真。这一自由度的分析计算方法也为其他可展结构,或具有复杂几何结构的自由度的计算提供了一种分析思路。(2)对空间三剪式单元可展结构进行数学化,绘制了其拓扑几何图,并推导了可展结构的运动学公式,给出了螺旋速度和加速度与质点在空间坐标系下速度和加速的关系式。建立了可展结构剪式单元的局部坐标系,求得了构件的质心雅克比矩阵。基于螺旋理论和虚功原理,推导了剪式单元可展结构的动力学方程,进而对可展结构进行了运动学和动力学分析。(3)研究了铰链间隙对剪式单元可展结构动力学和运动同步性的影响。采用了L-N间隙模型,建立了考虑间隙的动力学方程。并分别就铰链间隙大小、间隙所处的位置和可展结构展开速度等三个因素,对剪式单元可展结构展开过程的影响进行了研究,获得了相应的数据结果。根据数据结果,讨论总结了以上三个因素对可展结构展开过程动力学特性的影响。(4)根据剪式单元可展结构的几何特点,推导了在绝对节点坐标下,可展结构的固定约束和铰链约束方程,并根据有限元技术组合形成可展结构的总体刚度矩阵和质量矩阵,建立了约束条件下可展结构的结构动力学方程。采用了Newmark法对结构动力学方程进行数值求解,并得到了相应的数据结果,进而研究了剪式单元可展结构分别在力和速度的扰动下,可展结构的动力学响应问题。(5)设计并加工了剪式单元可展结构的实验件,并搭建了相应的实验台。进而测试了剪式单元可展结构在铰链间隙下的振动加速度,进行了相关数据的采集工作,并进行了分析。本文为解决剪式单元可展结构的自由度计算问题,提出了结构的分解和组合方法,即可展结构先分解成基本单元,然后再进行组合,进而求解了可展结构的自由度。在螺旋理论的体系下,推导了具有多闭环和多冗余约束等特点的剪式单元可展结构的运动学方程和质心雅克比矩阵,并基于虚功原理,建立了可展结构的动力学方程。由于间隙是不可避免的,并且对可展结构动力学也具有不可忽视的影响,所以系统地研究了间隙这一因素,对剪式单元可展结构在展开过程中动力学特性的影响。剪式单元可展结构在展开到位锁止进行工作时,将会受到一定的扰动,进而可展结构会产生振动,严重时会影响其正常工作,所以基于绝对节点坐标法,研究了可展结构的动力学响应这一关乎其构型稳定性的问题。本文系统地研究了剪式单元可展结构的自由度计算,和可展结构在展开过程中和构型保持时的动力学特性,该研究工作不仅为机构学和结构学这一交叉学科的发展提供了理论基础,而且有助于可展结构的应用和进一步推广。
[Abstract]:The deployable structure has the functions of zoom and configuration, so it is widely used in the fields of aviation, space and architecture. As a special mechanical structure, the deployable structure can realize the transformation of the structure of mechanism and structure. There are many kinds of units which make up the deployable structure, and the shear units with the advantages of large shrinkage ratio are the most important. A common type, and can form different deployable structures according to different array modes. But the deployable structure composed of shear unit arrays is a multi body composite structure with characteristics of multiple closed-loop and multiple redundancy constraints. It is precisely because of the complex structural characteristics of the extensible structure of the shear unit, so it is designed in its design. In the analysis, it is not only to study the problem of the type synthesis of the extensible structure of the shear unit, but also to study its kinematic and dynamic characteristics, as well as the stability of the configuration in place. Therefore, the research on the freedom and dynamics of the extensible structure of the shear unit is studied in this paper. The specific research work and innovation are as follows: (1) The method of decomposition and combination of the extensible structure of the shear unit is made, and the analysis and calculation method of the extensible structural freedom of the shear unit is established based on the spiral theory. First, the structure of the extensible structure of the shear unit is decomposed into some basic units, and the topological geometric maps are drawn according to the graph theory method and then based on the helix theory. The constraint helix equation is established. Then, the basic units are combined into the original extensible structure, and the degree of freedom is calculated according to the spiral theory. Finally, the free degree calculation and Simulation of the two different array modes are selected for the freedom degree. The analysis and calculation method of this degree of freedom is also other deployable structure, The calculation of the degree of freedom with complex geometric structure provides an analytical idea. (2) the deployable structure of the space three shear unit is mathematically transformed, its topological geometry is drawn, and the kinematic formula of the deployable structure is derived, and the relation between the velocity and acceleration of the spiral velocity and acceleration and the particle in the space coordinate system is given. The centroid Jacobi matrix of the extensible structural shear unit is obtained. Based on the theory of spiral and virtual work, the dynamic equation of the deployable structure of the shear element is derived, and the kinematic and dynamic analysis of the deployable structure is carried out. (3) the dynamic and movement of the articulated structure of the shear element is studied. The L-N gap model is used to establish the dynamic equation of the gap, and three factors, such as the size of the hinges, the position of the gap and the expansion speed of the deployable structure, are respectively studied. The results of the data are obtained. The results of the data are discussed. The influence of the above three factors on the dynamic characteristics of the deployable structure is summarized. (4) according to the geometric characteristics of the deployable structure of the shear element, the fixed and hinge constraint equations of the deployable structure under the absolute node coordinates are derived, and the overall stiffness matrix and mass matrix of the deployable structure are formed according to the finite element technique. The structural dynamic equations of the deployable structure under constraint conditions are established. The Newmark method is used to solve the structural dynamic equations and the corresponding data results are obtained. Then the dynamic response of the deployable structure of the shear element under the disturbance of force and velocity is studied. (5) the shear unit is designed and machined. The experimental parts of the deployable structure are set up and the corresponding experimental bench is set up. Then the vibration acceleration of the extensible structure of the shear unit under the hinges gap is tested and the relevant data acquisition work is carried out, and the analysis is carried out. In order to solve the problem of the free degree calculation of the extensible structure of the shear unit, the method of decomposition and combination of the structure is put forward. In the system of spiral theory, the kinematic equation and the centroid Jacobian matrix of the extensible structure with multiple closed loop and multiple redundancy constraints are derived. Based on the principle of virtual work, the dynamics of the deployable structure are established. As the gap is unavoidable and has an unnegligible effect on the dynamics of deployable structures, the factor of clearance is systematically studied and the influence of the deployable structure of the shear unit on the dynamic characteristics of the deployable structure. The disturbance, and then the deployable structure will produce vibration, and it will affect its normal work seriously. Therefore, based on the absolute node coordinate method, the dynamic response of the deployable structure is studied on the problem of its configuration stability. This paper systematically studies the calculation of the freedom degree of the deployable structure of the shear unit, and the deployable structure in the expansion process and the configuration. The research work not only provides a theoretical basis for the development of the cross discipline of institutional and structural science, but also contributes to the application and further extension of the deployable structure.
【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH112

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