Cable-Driven Parallel Manipulators with Extensible Rods

多年来，不同类型的冗余度在串联机械手的背景下已经达到了很好的成熟水平。最值得注意的是，为了获得更好的运动学性能或避障，运动学冗余(即添加比任务严格要求更多的关节和连杆)一直是许多工作和成功的机械手设计(例如Canadarm)的重点。然而，在并联机械手(PM)中，冗余度仍处于起步阶段。最近的一些工作已经使用冗余来解决PM的一些常见问题(例如，小和/或高度奇异的工作空间)，并开发新的或改进的机械手体系结构。本文将从理论和实践两个角度对驱动冗余度进行研究。在驱动冗余度方面，重点研究具有较大工作空间的缆索驱动并联机器人(CDPM)。虽然可以设计具有非常大的工作空间(例如，SkyCam)的CDPM，但所得到的CDPM也具有非常大的占地面积。这在很大程度上是因为电缆只能拉，而且总是需要保持张力。在这里，有人建议用驱动的卷曲或伸缩支柱来增强CDPM，这将本质上创造出具有混合驱动的机械手。由于新的执行元件将允许推力和拉力，因此机械手可以执行任务的空间区域可以相当大地扩展。*有效地确定机械手可以施加或维持特定最小力/力矩耦合的区域对于确定特定任务的最佳机械手至关重要。需要新的方法和高效的计算工具来足够快地完成这项任务，以便进行机械手的优化设计。有了这些方法和工具，机器人设计者将能够确定执行所需任务的所有驱动器(无论是缆索还是卷曲/伸缩支柱)的数量、位置和特性。拟议工作的一个重要部分是使用带弹簧或新型元件(如缝隙管或双稳复合管)的驱动器的研究和设计。这些轻型构件可以从线轴展开，但它们可以承受两个方向的轴向力。也就是说，它们将允许在拉伸和压缩的同时施加力量，同时具有相对较长的冲程。虽然这种技术的变种已经存在了20多年，但它们已经用于低速应用，如可展开的空间结构。这里的目的是在相对高速的应用中使用该技术。这些驱动器将极大地扩大CDPM的范围并允许新的实际应用。*总的来说，这项工作将为机器人设计者提供更好的PM设计工具和更多的运动学体系结构选择。这项工作的一个非常重要的副产品将是用于高速应用的可伸缩棒的开发和设计。

Redundancy of different types in the context of serial manipulators has reached a good level of maturity over the years. Most notably, kinematic redundancy (i.e., adding more joints and links than those strictly required by the task) for better kinematic performance or obstacle avoidance has been the focus of a number of works and successful manipulator designs (e.g., Canadarm). In parallel manipulators (PMs), however, redundancy is still in its infancy. Some recent works have used redundancy to tackle a few common issues of PMs (e.g., small and/or highly singular workspaces) and to develop new or improved manipulator architectures. The research proposed here will study actuation redundancy from theoretical and practical perspectives.******In terms of actuation redundancy, the focus will be on Cable Driven Parallel Manipulators (CDPMs) which have potentially large workspaces. Although it is possible to design CDPMs with very large workspaces (e.g., the SkyCam), the resulting CDPMs have a very large footprints as well. This is mostly due to the fact that cables can only pull and always need to be kept in tension. Here, it is proposed to enhance CDPMs with actuated coiled or telescopic struts that will essentially create manipulators with hybrid actuation. Since the new actuated members would permit both pushing and pulling, the region in space in which the manipulator can perform tasks can be extended quite significantly.******Efficiently determining the region in which a manipulator can apply or sustain a certain minimum force/moment couple is essential to determining the best manipulator for a specific task. New methods and efficient computational tools are required to perform this task fast enough to allow optimal design of manipulators. With these methods and tools, a robot designer would be able to determine the number, placement and characteristics of all the actuators (whether they are cables or coiled/telescopic struts) to perform the desired task.******An important part of the proposed work is the study and design of the actuators using either tape springs or novel elements such as slit tubes or bistable composite tubes. These light members can be deployed from a spool yet they can sustain axial forces in both directions. That is, they will allow forces to be applied both in tension and compression while having relatively long strokes. Although variants of this technology have existed for over two decades, they have been used on low speed applications such as deployable space structures. Here, the intention is to use the technology in relatively high speed applications. These actuators will greatly enhance the scope and allow new practical application of CDPMs.******Overall, this work will give robot designers better design tools for PMs and a larger selection of kinematic architectures. A very significant by-product of the work will be the development and design of extensible rods for high speed applications.