Robonaut Arm

NASA Meatball




Robonaut has two arms designed to be equivalent to human strength,scale, reach and dexterity.


    Robonaut's arms are human scale manipulators designed to fit withinthe exterior volume of an Astronaut's suit (the EMU). Beyond its volume, designobjectives were human equivalent strength, human scale reach, thermal enduranceto match an 8 hour EVA, fine motion, high bandwidth dynamic response,redundancy, safety, and a range of motion that exceeds that of a human limb. Thearm has a dense packaging of joints and avionics developed with the mechatronicsphilosophy. The endoskeletal design of the arm houses thermal vacuum ratedmotors, harmonic drives, fail-safe brakes and 16 sensors in each joint.Customlubricants, strain gages, encoders and absolute angular position sensors weredeveloped in house to make the dense packaging possible. TheRoll-Pitch-Roll-Pitch-Roll-Pitch-Yaw kinematic tree is covered in a series ofsynthetic fabric layers, forming a skin that provides protection from contactand extreme thermal variations in the environment of space. Two of these armjoints have already been tested in a thermal vacuum chamber at JSC, where theyperformed well as the temperature was varied from -25C to 105C.

The arms were designed using software developed as part of Dr.Ambrose's Ph.D. dissertation at the University of Texas at Austin [1].This software was used to size [2][3] and select components [4][5],evaluate strength requirements [6] and simulate thermal endurance[7][8][9][10][11] for specific task timelines. The combined design ofthe arms, body and leg (tail) for the microgravity applications was alsoperformed using custom analysis techniques, where load sharing andcompliance require an understanding of serial, parallel and bifurcatingchain kinetics [12]. Arm requirements for advanced applications suchas climbing in microgravity[13] and integration with surface mobility systems(rovers) are now being explored.


1. Ambrose, Robert O. "Design, Construction and Demonstration of Modular, Reconfigurable Robots", Ph.D. Dissertation, The University of Texas at Austin, August, 1991.2 "An Experimental Investigation of Robot Actuator Performance", ISMCR, Japan, November 16, 19923 "Interactive Robot Joint Design, Analysis and Prototyping", ICRA 95 Robotics and Automation Conference, Nagoya, Japan, May 1995.4 "Designing Modular Robots for a Spectrum of Space Applications", SPIE, Boston, November 18, 19925 "The Optimal Selection of Robot Modules for Space Manipulators", Space '94, Albuquerque, February, 1994.6 "Definitions of Strength in Serial and Bifurcated Manipulators", ISA 96, Chicago Il, November 1996.7 "Thermodynamic Implications for the Design and Control of Space Robots", ISMCR, Italy, September 1993.8 "Thermal Management in Hyper-Redundant Space Manipulators", SPIE, Boston, September, 8 1993.7 "Modeling Robot Actuators in Space Environments", Am. Nuclear Soc. Conf. Robotics and Remote Systems, Monterey Ca, Feb 1995.9 "Robot Models for Space Environments", ICRA 95 Robotics and Automation Conference, Nagoya, Japan, May 1995.10 "An Experimental Investigation of Actuator for Space Robots", ICRA 95 Robotics and Automation Conf., Nagoya, Japan, May 1995.11 "The Serial form of Strength in Serial, Parallel and Bifurcated Manipulators", ICRA 98, Lueven Belgium, 1998.12 "Graphical Simulation Environment for Locomotion Analysis", Houston Conf. on Biomedical Engineering, Houston, Feb 1994


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