Design and development of reconfigurable robots with lockable telescopic joints

在几次机器人飞行任务中，将空间机械手的手臂压缩到其指定的发射量一直是一个困难的设计问题，不仅用于在轨服务，而且还用于行星探索。此外，在复杂环境中工作的机器人经常需要改变其结构和大小，以满足给定任务的环境和其他要求。特别是在空间应用中，采用能够执行不同任务的单个多功能机器人既是理想的，也是经济有效的，例如：检查、接触操作、组装或携带物体。这些任务中的每一项的最佳操作都需要特定的机械手设计。例如，具有最大化工作空间体积的长臂杆的机器人通常适合于诸如检查和有效载荷处理之类的操作，而具有最大化机器人末端执行器的力/扭矩能力的短臂杆的机器人适合于灵巧和接触任务操作。传统的可重构机器人使用特殊设计的自含式模块化关节，每个关节都可以通过多个连接点连接到相邻的链接。然而，由于这些可重构机器人是模块化的，它们需要一个有效的连接器对接系统来连接和释放模块。提出了一种可重构机器人的新范式和概念设计。与传统的可重构机器人不同，我们的设计不使用模块化关节进行自我重构。相反，机器人具有可锁定的被动关节，即没有致动器或传感器的关节，允许改变Denavit-Hartenberg(DH)参数，如连杆长度和扭转角度。然而，当机器人形成一个封闭的运动链时，被动关节是可控的。此外，每个被动关节都配备了一个常闭的内置锁定机构，当参数需要改变时，可以释放该机构。该方案的目的是通过在锁定机构的设计和优化、DH参数的优化以及此类机器人的鲁棒控制系统方面的一系列改进，提高可锁伸缩连杆可重构机器人的技术准备能力。

Compacting the arms of a space manipulator in its designated launch volume has been a difficult design problem in several robotic missions for not only in-orbit servicing but also planetary exploration. Moreover, robotic manipulators working in a complex environment often need to change their configuration and size in order to meet the environmental and other demands of a given task. Particularly in space application, it is both desirable and cost effective to employ a single versatile robot capable of performing different tasks such as; inspection, contact operation, assembly, or carrying an object. Optimal operation of each of these tasks demands a specific manipulator design. For instance, a robot with long booms maximizing the workspace volume is typically suitable for such operations as inspection and payload handling whereas a robot with short booms maximizing the force/torque capacity of the robot end-effector is suitable for dexterous and contact task operations. Conventional reconfigurable robots make use of especially designed, self-contained modular joints, each of which can be connected to its adjacent links through its multiple connection points. However, since these reconfigurable robots are modular, they need an effective docking system for connector for joining and releasing the modules. A new paradigm and a conceptual design for reconfigurable robots is proposed. Unlike conventional reconfigurable robots, our design does not reconfigure itself by utilizing modular joints. Rather, the robot has lockable passive joints, i.e., joints with no actuators or sensors, which permit changing the Denavit-Hartenberg (DH) parameters such as the link length, and the twist angle. The passive joints are controllable, however, when the robots forms a closed kinematic chain. Also, each passive joint is equipped with a normally closed, built-in locking mechanism, which can be released whenever the parameters need to be changed. The objective of this proposal is enhance the technology readiness of reconfigurable robots with lockable telescopic links through a series of advancements in design and optimization of the locking mechanism, optimization of DH parameters, and robust control system for such robots.