一类三自由度并联机构的特性研究与优化设计

发布时间：2017-12-31 04:12

本文关键词：一类三自由度并联机构的特性研究与优化设计　出处：《中国科学技术大学》2013年博士论文　论文类型：学位论文

【摘要】：随着天文学的发展,望远镜的分辨率要求越来越高,对副镜的支撑提出了更高的要求,传统的四翼梁式支撑结构可以实现自动调焦,但不能主动校正副镜的姿态,因此,设计具有两个转动一个移动自由度的副镜支撑机构,实时、稳定、高精度地调整副镜相对主镜的焦距和姿态,具有重要的现实意义。本文以望远镜副镜三自由度并联支撑为背景,围绕三自由度并联机构的设计主线,开展了构型设计与选型、运动学设计、精度分析与设计、结构参数优化设计、仿真平台设计等五方面的研究。并联机构的设计首先需要进行构型设计和选型。根据期望两个转动和一个移动自由度的需求,采用约束螺旋理论设计了三支链、采用添加约束法设计了四支链对称的三自由度并联机构。在此基础上,综合考虑并联机构的结构对称、结构简单、结构紧凑、低惯性等定性指标,以及伴随运动小、全局条件数大、运动副刚度大精度好等定量指标,最终选取3-RCU构型作为望远镜副镜并联支撑。本文提出分类建模方法,建立两转一移三自由度并联机构的统一运动学模型、速度传递模型和误差传递模型。根据并两转一移三自由度并联机构的驱动和约束特性,分类建立了运动学模型；在此基础上,建立了运动支链的D-H矩阵模型,全面反映各运动支链的运动副和杆件的运动特性；建立了并联机构的速度传递模型,反映驱动速度与动平台的有效位姿变化速度之间的映射关系,并得到机构的速度Jacobian巨阵和全局条件数。同时,对并联机构的姿态描述进行了深入讨论,引入zxz欧拉角法研究机构的伴随运动和姿态空间,引入YXY欧拉角法研究机构速度Jacobian矩阵、全局条件数和误差传递模型。考虑并联机构具有两个转动一个移动自由度,定义了两个欧拉角和一个移动的微小摄动为机构的有效位姿误差,基于误差摄动原理和机构的速度传递模型,建立了运动副安装误差(包括结构偏差)、运动副间隙误差和支链驱动误差(包括传感误差)等主要误差源到动平台有效位姿误差的全误差模型；然后,推导了3-RCU并联机构的最大误差模型,分析了各主要误差源对动平台有效位姿误差的误差灵敏度；最后,分别研究了基于灵敏度和基于成本的3-RCU并联机构精度设计,并采用遗传算法实现了3-RCU并联机构的精度设计。根据两转一移三自由度并联机构的运动特点,推广了机器人包含工作空间和全姿态工作空间的概念,定义了两转一移并联机构的可达工作空间和灵活工作空间,以及工作空间体积；然后讨论了并联机构的约束条件,并基于区间分析方法计算了3-RCU并联机构的工作空间,分析了工作空间的形状特点。确定以动平台半径、连杆中心位置长度和驱动行程与静平台半径的比值为设计变量,分析了全局条件数、最大位姿误差和工作空间体积等3个性能指标随3个设计变量的变化规律,优化设计得到3-RCU并联机构的关键结构参数。最后,利用Matlab GUI工具箱设计了两转一移三自由度并联机构仿真平台,重点研究了3-RCU并联机构的可视化运动仿真模块。基于SolidWorks软件建立了机构的三维实体模型,基于SimMechanics工具箱设计了机构的运动学和动力学控制系统,包括轨迹规划模块、控制器模块、并联机构模型模块和显示模块等,实现了3-RCU并联机构的可视化运动仿真研究。
[Abstract]:With the development of astronomy , the resolution requirement of the telescope is higher and higher , and the support of the auxiliary mirror is more demanding . The traditional four - wing beam type support structure can realize automatic focusing , but can not actively correct the posture of the secondary mirror . Therefore , it is of great practical significance to design the auxiliary mirror support mechanism with two rotational degrees of freedom to adjust the focal length and attitude of the secondary mirror relative to the main mirror in real time . In this paper , the three - degree - of - freedom parallel support is used as the background , and the design and selection , kinematics design , precision analysis and design , structural parameter optimization design , simulation platform design and so on are carried out around the design main line of the three - degree - of - freedom parallel mechanism . A three - degree - of - freedom parallel mechanism with four branches is designed by using the constraint screw theory . Based on this , a three - degree - of - freedom parallel mechanism with four branches is designed by using the constraint helix theory . Based on this , a three - degree - of - freedom parallel mechanism with four branches is designed by the addition restriction method . This paper proposes a classification modeling method , and establishes a unified kinematic model , a velocity transmission model and an error transmission model of two - turn one - shift three - degree - of - freedom parallel mechanism . Based on the above , a kinematic model is established according to the driving and constraint characteristics of the parallel mechanism with three degrees of freedom . The speed transfer model of the parallel mechanism is established to reflect the mapping relationship between the driving speed and the effective posture change speed of the moving platform . Considering that the parallel mechanism has two degrees of freedom of movement , two Euler angles and one moving minute perturbation are defined as the effective pose error of the mechanism . Based on the principle of error perturbation and the speed transfer model of the mechanism , a full error model of the effective pose error of the moving platform is established . According to the motion characteristics of the three - degree - of - freedom parallel mechanism , the concept of working space and full - attitude workspace is generalized , and the available working space and flexible working space of the two - turn - one - shift parallel mechanism are defined , and the working space volume is defined . Then the constraint conditions of the parallel mechanism are discussed , and the working space of the 3 - RCUs parallel mechanism is calculated based on the interval analysis method , and the shape characteristics of the working space are analyzed . It is determined that the ratio of the radius of the moving platform , the length of the center of the connecting rod and the radius of the driving stroke to the radius of the static platform is the design variable , and the three indexes of the global condition number , the maximum pose error and the working space volume are analyzed . The key structural parameters of the 3 - RCUs parallel mechanism are optimized according to the changing law of the three design variables . Finally , the simulation platform of three - degree - of - freedom parallel mechanism is designed by using the Matlab GUI toolbox . The visualization motion simulation module of 3 - RCUs parallel mechanism is studied . Based on the software , the kinematics and dynamics control system of the mechanism is designed , which includes trajectory planning module , controller module , parallel mechanism model module and display module .

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TH112;TH743

【相似文献】