基于多柔体动力学的并联机构动态特性研究

发布时间：2018-02-05 00:53

本文关键词： 并联机构多柔体系统动力学动态特性分析弹性变形仿真　出处：《沈阳建筑大学》2015年硕士论文　论文类型：学位论文

【摘要】：多体系统包括多刚体系统和多柔性体系统,包含柔性元件的多柔体系统是当前最热门的课题。传统的多体系统动力学研究主要在多刚体的领域内进行,然而由于刚性假设,在一些需要考虑构件变形的特殊情况下很难保证结果的精度要求。并联机构自问世以来就引起了世界各国的广泛关注与高度的重视,随着并联机构向轻型方向的发展,构件的柔度增大,并联机构中构件的柔性变形不仅会导致系统的运动精度降低同时也会引起系统的弹性振动,使得并联机构系统的运动学、动力学性能受到很大的影响。因此,对具有高精度和性能要求的并联机构,就必须计入构件的弹性变形对动力性能和运动精度的影响。并联机构的柔性多体系统是一个多闭环、刚柔耦合的非线性动力学系统,单纯地运用刚体动力学或弹性力学都无法准确描述构件的力学行为,而必须采用多柔体系统动力学理论进行分析。本文将并联机构与多柔体系统有机的结合起来,以具有柔性构件的空间三自由度并联机构为研究对象,基于柔性多体动力学对3-TPT并联机构的动态特性进行研究,主要内容如下:首先,对所研究的3-TPT并联机构的机构特点和运动学问题进行了分析。其中包括并联机构的机构组成和自由度的计算,位置正解和位置反解的分析和仿真,运动影响系数(雅克比矩阵)的计算,速度和加速度的分析和仿真以及机构的奇异性和平稳性的研究。其次,对3-TPT并联机构柔性多体系统动力学性能进行了研究。针对并联机构柔性多体系统建模的复杂性,考虑柔性从动杆刚性运动的刚柔耦合特性,利用假设模态法和拉格朗日方程建立此类并联机构柔性多体系统的动力学弹性振动微分方程。基于Euler-Bernoulli梁理论,采用假设模态法,分析各支链上从动杆的柔性变形,并利用Lagrange法,推导出3-TPT空间并联机构柔性多体系统的动力学方程,完成动力学建模。再次,在MATLAB软件环境下,对3-TPT并联机构柔性多体系统动力学模型进行仿真分析,计算出各支链上从动杆中点处的柔性变形,其中包括轴向变形量、横向变形量和由横向变形引起的轴向缩短量,并计算出由弹性变形产生的弹性势能,完成动力学仿真。最后,分析由弹性变形引起的杆长误差和铰链间隙误差导致最终的动平台的位置误差。分别应用矩阵法和误差独立作用原理建立误差模型,并将由矩阵法建立的误差模型基于蒙特卡洛法进行模拟仿真。本文基于柔性多体动力学对3-TPT并联机构进行动力学建模和仿真分析研究,并分析了由弹性变形引起的杆长误差和铰链间隙误差对机构动平台误差的影响,为此类含有柔性部件的并联机构的动态特性和误差分析的进一步研究奠定了基础。
[Abstract]:Multi-body system includes multi-rigid-body system and multi-flexible body system. The flexible multi-body system with flexible elements is the most popular subject at present. The traditional multi-body system dynamics research is mainly carried out in the field of multi-rigid-body system, but because of the rigid assumption, the multi-body system dynamics research is mainly carried out in the field of multi-rigid-body system. It is very difficult to guarantee the precision of the result under some special circumstances which need to consider the deformation of the component. The parallel mechanism has attracted extensive attention and high attention from all over the world since it came out, with the development of the parallel mechanism towards the light direction. The flexibility of the component increases, and the flexible deformation of the component in the parallel mechanism will not only lead to the decrease of the system motion accuracy, but also cause the elastic vibration of the system, which will greatly affect the kinematics and dynamic performance of the parallel mechanism system. For the parallel mechanism with high accuracy and high performance, the influence of elastic deformation of member on dynamic performance and kinematic accuracy must be taken into account. The flexible multi-body system of parallel mechanism is a multi-closed loop, rigid-flexible coupling nonlinear dynamic system. Simply using rigid body dynamics or elastic mechanics can not accurately describe the mechanical behavior of the member, but must be analyzed by the theory of multi-flexible body system dynamics. In this paper, the parallel mechanism and the multi-flexible body system are organically combined together. Taking the spatial 3-DOF parallel mechanism with flexible members as the research object, the dynamic characteristics of 3-TPT parallel mechanism are studied based on flexible multi-body dynamics. The main contents are as follows: first, The characteristics and kinematics of the 3-TPT parallel mechanism are analyzed, including the calculation of the mechanism composition and degree of freedom, the analysis and simulation of the position forward solution and the position inverse solution. Calculation of motion influence coefficient (Jacobi matrix), analysis and simulation of velocity and acceleration, singularity and stationarity of mechanism. Secondly, The dynamic performance of flexible multi-body system of 3-TPT parallel mechanism is studied. In view of the complexity of modeling of flexible multi-body system of parallel mechanism, the rigid-flexible coupling characteristic of rigid motion of flexible follower is considered. The dynamic elastic vibration differential equation of the flexible multi-body system of parallel mechanism is established by using the assumed mode method and Lagrange equation. Based on the Euler-Bernoulli beam theory, the flexible deformation of the follower on each branch chain is analyzed by using the hypothesis mode method, and the Lagrange method is used. The dynamic equation of 3-TPT space parallel mechanism flexible multi-body system is derived, and the dynamic modeling is completed. Thirdly, the dynamic model of 3-TPT parallel mechanism flexible multi-body system is simulated and analyzed under the environment of MATLAB software. The flexible deformation at the middle point of the follower on each branch chain is calculated, including the axial deformation, the transverse deformation and the axial shortening caused by the transverse deformation, and the elastic potential energy generated by the elastic deformation is calculated to complete the dynamic simulation. The position error of the final moving platform caused by the error of rod length caused by elastic deformation and the error of hinge clearance are analyzed. The error model is established by using the matrix method and the principle of error independent action, respectively. The error model established by matrix method is simulated by Monte Carlo method. The dynamic modeling and simulation analysis of 3-TPT parallel mechanism based on flexible multi-body dynamics are studied in this paper. The influence of rod length error and hinge clearance error caused by elastic deformation on the mechanism platform error is analyzed, which lays a foundation for the further study of the dynamic characteristics and error analysis of this kind of parallel mechanism with flexible components.
【学位授予单位】：沈阳建筑大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH112

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