Design and development of reconfigurable robots with lockable telescopic joints

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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.