Pasadena, California Special-purpose robot hands (end effectors) now under development are intended to enable robots to traverse cliffs much as human climbers do. Potential applications for robots having this capability include scientific exploration (both on Earth and other rocky bodies in space), military reconnaissance, and outdoor search and rescue operations.
Until now, enabling robots to traverse cliffs has been considered too difficult a task because of the perceived need of prohibitively sophisticated planning algorithms as well as end effectors as dexterous as human hands. The present end effectors are being designed to enable robots to attach themselves to typical rock-face features with less planning and simpler end effectors. This advance is based on the emulation of the equipment used by human climbers rather than the emulation of the human hand. Climbing-aid equipment, specifically cams, aid hooks, and cam hooks, are used by sport climbers when a quick ascent of a cliff is desired (see Figure 1).
Currently two different end-effector designs have been created. The first, denoted the simple hook emulator, consists of three “fingers” arranged around a central "palm." Each finger emulates the function of a particular type of climbing hook (aid hook, wide cam hook, and a narrow cam hook). These fingers are connected to the palm via a mechanical linkage actuated with a leadscrew/nut. This mechanism allows the fingers to be extended or retracted. The second design, denoted the advanced hook emulator (see Figure 2), shares these features, but it incorporates an aid hook and a cam hook into each finger. The spring-loading of the aid hook allows the passive selection of the type of hook used.
The end effectors can be used in several different modes. In the aid-hook mode, the aid hook on one of the fingers locks onto a horizontal ledge while the other two fingers act to stabilize the end effector against the cliff face. In the cam-hook mode, the broad, flat tip of the cam hook is inserted into a non-horizontal crack in the cliff face. A subsequent transfer of weight onto the end effector causes the tip to rotate within the crack, creating a passive, self-locking action of the hook relative to the crack. In the advanced hook emulator, the aid hook is pushed into its retracted position by contact with the cliff face as the cam hook tip is inserted into the crack. When a cliff face contains relatively large pockets or cracks, another type of passive self-locking can be used. Emulating the function of the piece of climbing equipment called a "cam" (note: not the same as a "cam hook". see Figure 1), the fingers can be fully retracted and the entire end effector inserted into the feature. The fingers are then extended as far as the feature allows. Any weight then transferred to the end effector will tend to extend the fingers further due to frictional force, passively increasing the grip on the feature. In addition to the climbing modes, these end effectors can be used to walk on (either on the palm or the fingertips) and to grasp objects by fully extending the fingers.
This work was done by Brett Kennedy and Patrick Leger of Caltech for NASA’s Jet Propulsion Laboratory. NPO-40224
This Brief includes a Technical Support Package (TSP).
Robotic End Effectors for Hard-Rock Climbing
(reference NPO-40224) is currently available for download from the TSP library.
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Overview
The document titled "Technical Support Package for Robotic End Effectors for Hard-Rock Climbing" from NASA's Jet Propulsion Laboratory outlines advancements in robotic technologies designed to enable robots to traverse challenging terrains, particularly in hard-rock environments. This capability is essential for various applications, including extraterrestrial exploration, military reconnaissance, and search and rescue operations.
The primary motivation for developing these robotic end effectors is the need for effective navigation of rugged landscapes, such as Martian cliff faces, which can provide valuable geological information. Traditional methods of climbing and traversing such terrains have been deemed too complex for robots due to the requirement for sophisticated planning algorithms. To address this challenge, the document proposes the emulation of proven climbing equipment used by humans, which allows robots to achieve secure attachments with minimal planning.
Key components of the robotic end effectors include devices that replicate the functions of climbing aids such as aid hooks and cam hooks. The design features a lead screw and nut mechanism that drives a linkage system to extend "fingers" that can mimic the gripping capabilities of these climbing tools. The aid hook, for instance, locks itself into horizontal ledges under load, providing stability through contact points at its base, while the cam mechanism offers a self-locking feature for secure placement in pockets or wide cracks.
The document emphasizes the versatility of these robotic systems, which can be adapted for various widths and functionalities to suit different climbing scenarios. By leveraging existing climbing technologies, the robots can navigate difficult terrains more effectively, reducing the risks associated with human involvement in hazardous environments.
Overall, the technical support package highlights the potential of robotic end effectors to enhance exploration and operational capabilities in both terrestrial and extraterrestrial contexts. The innovations presented aim to facilitate safer and more efficient traversing of challenging landscapes, ultimately contributing to advancements in scientific research and operational effectiveness in rugged terrains. The document serves as a resource for understanding the technological developments in this field and their broader implications for future exploration missions.
