【作者】 刘鹏；

【导师】 仇原鹰；

【作者基本信息】 西安电子科技大学 ， 机械电子工程， 2015， 博士

【摘要】 柔索牵引并联机器人是并联机器人家族中重要的组成部分,具有结构简单,重量轻,耗能低,控制容易,惯性小和移动速度快,有更高的精度等优点。因此,具有广泛的应用领域和重要的研究价值。但是由于其作为驱动元件的绳索的柔性和单向约束特性,使得柔索牵引并联机器人较传统的杆支撑并联机器人有很多不同的特性。由于绳索的柔性特性,柔索牵引并联机器人末端执行器运动的稳定性成为对其研究的主要环节,稳定性对柔索牵引并联机器人的总体性能具有重要的影响。本文从传统的刚性支撑的稳定性出发,结合柔索牵引并联机器人独有的特点,引申并总结出影响柔索牵引并联机器人末端执行器运动的稳定性的主要因素,并进一步提出评价其末端执行器运动的稳定性的评价方法,旨在为打破柔索牵引并联机器人应用中的重要瓶颈一由于绳索的柔性和约束不足导致的运动稳定性问题。从传统刚性支撑的稳定性出发,引申出柔索牵引并联机器人稳定性的主要决定因素有二点：“位置”因素,由于当前位置点在工作空间所处的位置对柔索牵引并联机器人末端执行器运动的稳定性具有重要的影响,因此柔索牵引并联机器人的稳定性中必须考虑位置因素的影响；“约束力”因素,同时当前位置点处拉力最小绳索的索拉力对柔索牵引并联机器人末端执行器运动的稳定性也具有重要的影响,因此柔索牵引并联机器人的稳定性中必须考虑约束最小的索拉力的影响。本文的研究围绕国家自然科学基金项目：“高速柔索牵引摄像机机器人机动性与稳定性研究(51175397)”的相关内容,主要对此类柔索牵引并联机器人进行了基于两种模型下的运动学分析、最小索拉力在工作空间的分布研究、运动稳定性分析以及稳定工作空间的求解研究,旨在为柔索牵引并联机器人的性能提升和实际工程应用提供理论依据和技术支持。绳牵引并联摄像机机器人作为柔索牵引并联机器人的典型代表,比传统的高空摄像方式有明显的优势。但摄像机器人的高速运动会对其稳定性造成很大影响,且在实际运行中易于受到气象条件的干扰,需要一种符合其实际特点的稳定性评价方法来衡量绳牵引并联摄像机机器人运动的稳定性。本文的研究内容主要针对四个关键点：①综合“位置”和“约束力”因素来分析柔索牵引并联机器人末端执行器运动的稳定性；②基于柔索牵引并联机器人的运动学解,提出了影响末端执行器运动稳定性的位置性能因子,进而研究了位置性能因子在全工作空间内的分布情况；③基于柔索牵引并联机器人的索拉力优化解,提出影响末端执行器运动稳定性的索拉力性能因子,进而研究了索拉力性能因子在全工作空间内的分布情况；④提出了符合一定稳定度条件的稳定工作空间的求解方法。完成的主要工作及取得的创新性研究成果归纳如下：1.定义了影响柔索牵引并联机器人末端执行器运动的稳定性的“位置”因素,提出了影响末端运动稳定的位置性能因子,分析了位置性能因子的影响参数,进一步给出了位置性能因子的解析表达式,并绘制了位置性能因子在工作空间不同区域所形成的等位曲线。针对柔索牵引并联机器人绳索的悬链线特性,分析了结构尺度以及末端执行器与绳索总质量比值对大跨度绳索悬链线形态的影响机制。从柔索牵引并联机器人的运动学解出发,提出了影响末端运动稳定的位置性能因子。以绳牵引摄像机器人为研究对象,对直线模型和悬链线模型下绳牵引摄像机器人的运动学和位置性能因子进行比较,从而为更准确地衡量和评价柔索牵引并联机器人末端执行器运动的稳定性奠定基础。2.阐述了影响柔索牵引并联机器人末端执行器运动的稳定性的“约束力”因素,定义了当前位置点处所有绳索的最小索拉力,提出了影响末端稳定性的索拉力性能因子,剖析了索拉力性能因子的决定因素,给出了索拉力性能因子的隐函数表达式,并分析了索拉力性能因子和最小索拉力在工作空间的分布情况。基于欠约束、完全约束和冗余约束柔索牵引并联机器人直线和悬链线两种情况下的冗余索拉力求解模型,绘制了索拉力性能因子和最小索拉力在工作空间的分布图谱。针对必须把绳索建模为悬链线模型的完全和冗余约束柔索牵引并联机器人,建立了求解其索拉力的优化模型,提出了一种以直线状态下的索长和张力为迭代初始值,以索的垂度不发生改变为终止条件的迭代算法实现了对张力的优化求解,为柔索牵引并联机器人的力控制奠定了理论基础。通过对比两种模型下末端处于工作空间任一位置点处的索拉力、最小索拉力以及索拉力性能因子,表明对于大尺寸柔索牵引并联机器人,把大跨度绳索建模为悬链线形态的必要性。3.提出了柔索牵引并联机器人基于位置性能因子和索拉力性能因子的力位混合结构稳定性以及考虑末端运动速度的三位一体运动稳定性求解方法,分析了影响末端稳定性的决定因素,并给出了力位混合的稳定性因子的隐函数表达式,进一步图示了力位混合的稳定度在工作空间不同区域的分布等位曲线。该力位混合稳定性求解方法针对柔索牵引并联机器人特有的柔性驱动特性,结合了影响柔索牵引并联机器人末端执行器运动稳定性的主要影响因素,采用加权系数法,构建了评价柔索牵引并联机器人末端执行器运动稳定性的解析方法。其采用区间(0,1]之间的数值来衡量柔索牵引并联机器人的稳定性,不同于传统的对稳定性的状态只存在稳定或者不稳定两种情况的评价标准,能够较为灵活的获取满足一定稳定度的柔索牵引并联机器人的稳定工作空间。并对两种模型下柔索牵引并联机器人末端运动的稳定度进行对比和分析,以便能够为大跨度柔性驱动的柔索牵引并联机器人运动的稳定性的求解方法提供理论依据和求解策略,进一步打破制约柔索牵引并联机器人发展主要瓶颈。4.从力位混合稳定性能求解方法和工作空间的定义出发,提出了完全约束以及冗余约束柔索牵引并联机器人的稳定工作空间的定义,研究了其稳定工作空间的存在条件及其求解方法。进一步将柔索牵引并联机器人受到广义外力扰动后的工作空间与稳定工作空间进行比较,仿真结果表明采用力位混合稳定性求解因子的合理性。更多还原

【Abstract】 The cable-driven parallel manipulators with redundant actuations, which are simple, light-weight structure, low energy consumption, easy to control, low moment inertia and high speed motion, higher accuracy and so on, play important roles in the family of parallel manipulators, therefore having abroad applications and valuable exploitations. Indeed, the unilateral constraints of the flexible drive cables makes the cable-driven parallel manipulators possess some distinctive features that the parallel ones with rigid handles do not. However, a major challenge in the theory study of the cable-driven parallel manipulators comes from the fact that, the flexible cables lead to the challenge of the stability.Due to the flexible property of the drive cables, the stability of the cable-driven parallel manipulators is the impotant part of the reseach on the cable-driven parallel manipulators, which has a critical influence on the overall performances. Based on the stability of conventional parallel manipulators, combining with the peculiarities of the cable-driven parallel manipulators, the critical parts influencing the stability of the cable-driven parallel manipulators are proposed, and moreover, the calculating method of the stability evaluating the stability of the cable-driven parallel manipulators are proposed in order to break the development bottleneck of the cable-driven parallel manipulators. To the authors’knowledge, there are two primary factors influencing the stability of the cable-driven parallel manipulators, and they are respectively the positions and the constraints. Both the present position and the constraint have an important influence on the stability of the cable-driven parallel manipulators, thus they are taken into consideration when evaluating the stability of the cable-driven parallel manipulators.The reseach on the cable-driven parallel manipulators is based on the key project of Natural Science Foundation of China. And moreover, the analysis of the kinematics, the distributions of the cable tensions in the workspace, the analysis of the stability for the cable-driven parallel manipulators and the stability workspace designed with the stability performance index are studied in this paper, furthermore, the research results can found theoretical and technical basis for the performance improvement and engineering application of cable-driven parallel manipulators. Indeed, the camera robot with high speed is one of the cable-driven parallel manipulators, which has some advantages over the conventional ways of the taking photographs. However, the high speed and flexible cables of the camera robot have an important influence on the stability of it, so the method evaluating the stability of the camera robot is needed to measure the overall performances.This paper deals with four issues, and they are respectively as follows:① the stability of the cable-driven parallel manipulators is discussed combining the positions and the constraints; ② based on the kinematics model of the cable-driven parallel manipulators, the position factors that have an important influence on the stability of the cable-driven parallel manipulators are proposed, and moreover, the distributions of the position factors are considered; ③ based on the optimization model of the cable tensions for the cable-driven parallel manipulators, the force factors that have an important influence on the stability of the cable-driven parallel manipulators are proposed, and moreover, the distributions of the force factors are considered; ④ the determining method of the workspace that possesses a specified stability for the cable-driven parallel manipulators is presented. The main contents can be described as follows:1. The position factors influencing the stability of the cable-driven parallel manipulators are discussed, and moreover, the distributions of the position factors are considered. Considering the catenary the large-span cables having, the influence mechanism of the dimensions and the weight of the cable-driven parallel manipulators for the shape of the catenary the large-span cables possessing is analysed. First of all, the analysis of the kinematics for the cable-driven parallel manipulators with the catenary and massless straight line models are discussed, in which two position factors having the significant effects on the stability for the cable-driven parallel manipulators are proposed respectively. And moreover, the kinematics and the two position factors of the cable-driven parallel manipulators with the two models are compared, therefore providing a systematic basis of reference for the stability of the movement for the cable-driven parallel manipulators.2. The force factors influencing the stability of the cable-driven parallel manipulators are discussed and the minimum cable tensions the current position having are defined. Furthermore, the distributions of the minimum cable tensions and the force factors with the catenary and massless straight line models are depicted based on the optimization algorithm solving the determining of the cable tensions with the proper optimal objective function. Considering the catenary the large-span cable-driven parallel manipulators having, the cable tensions optimization model is set up, and moreover, the iterated algorithm, that employs the length and the tensions of the cables with the straight line model as the initial values of them, is proposed to solve the cable tensions for the large-span cable-driven parallel manipulators. Comparing the cable tensions and two force factors with the two models leads to the necessity of taking the cable sags into consideration for the large-span manipulators.3. The stability performance index is described using the weighted method based on the two position factors and the two force factors. Apart from the above mentioned, the approach considers the flexible of the cables and integrates the key factors influencing the stability of the cable-driven parallel manipulators. Furthermore, the approach using the interval (0,1] to evaluate the stability of the cable-driven parallel manipulators is different from the traditional one and is capable of obtaining the workspace with the specified stability. Particular emphasis was placed on the primary factors influencing the stability of the cable-driven parallel manipulators, and they are studied in detail and worked out, therefore proposing the method with the crucial factors evaluating the stability of the cable-driven parallel manipulators. Moreover, comparing the stability with the two models concludes that it is necessary to regard the cables as the catenary for the large-span manipulators in order to evaluate the stability of the cable-driven parallel manipulators accurately.4. The stability workspaces combining the stability performance index and the definition of the workspaces for completely restrained and redundant restrained cable-driven parallel manipulators are investigated, and moreover, the existence conditions of the stability workspaces of the two types of the robots above are given and proved, in addition to, a solution strategy is proposed to determine the workspaces of the two types of cable-driven parallel manipulators above. Apart from the above mentioned, a new workspace, the Specified Minimum Cable Tension Workspace (SMCTW), is introduced, within which all the minimum tensions exceed a specified value, therefore meeting the specified tension requirement. Furthermore, the distributions of the minimum cable tensions in the workspace are depicted. At last, a robustness workspace with the external wrench compared with the stability workspaces is selected to demonstrate the effectiveness of the stability performance index above for the cable-driven parallel manipulators.更多还原