ARC ANGEL Reduces Gravity’s Effect on Arms
Mechanical and Fluid Systems
ARC ANGEL Reduces Gravity’s Effect on Arms (MSC-TOPS-139)
Robotic system offloads arms for astronaut trainees, others
Overview
Innovators at NASA Johnson Space Center (JSC) have developed an earthbound robotic training system called “ARGOS” for short. It can actively simulate an astronaut’s weightlessness in space by using an overhead runway and bridge drive system to partially or fully offload their weight using attached cables, effectively suspending them off the ground. Although the test subject’s torso and legs are offloaded, their arms and any weighty hand tools are not.
Enter “ARC ANGEL”. The Actuated Realtime Control for ARGOS Nega-tion of Gravitational Effects on the Limbs (ARC ANGEL) technology was developed to offload a space suited test subject’s arms and counteract fatigue realized while performing training activities using ARGOS. Like ARGOS, ARC ANGEL provides offloading via computer-controlled active cable tension. Cables are strung between arm cuffs located just above each elbow, and a motorized reel(s) mounted to the spacesuit’s backpack-like Primary Life Support System (PLSS).
This active offloading technology could be used for a number of appli-cations in addition to simulating zero to one G environments. For exam-ple, a patient rehabilitating their shoulder could benefit from movement assistance that offloads arm weight or grasp load, a construction worker carrying a heavy tool could more easily manipulate it, or it could offset equipment weight for military personnel ultimately staving off limb fatigue that would otherwise occur.
The Technology
ARC ANGEL is an active robotic system like ARGOS; however, its electric motor is not mounted overhead to a runway and bridge system, but instead is mounted to the test subject’s backpack-like PLSS where the motor(s) supplies real-time actuation torque off-loading to the upper arms via cabling. If a test subject picks-up a hammer, the system will react immediately to offload the weight of the hammer relative to the programmed environment.
The ARC ANGEL system is comprised of an electric motor(s), soft goods, electronics hardware, firmware, and software. To provide a smoothly operating arm offloading analog and optimize system performance, engineers at JSC coded software that leverages kinematic algorithms and closed-loop architecture for motor control, along with custom computer language scripts to ingest sensor data. This allows ARC ANGEL’s subsystems to be seamlessly integrated and accurately simulate one to zero G environments.
During operation, compact tension sensors and inertial measurement units detect arm weight and motion and provide a closed-loop control system that feeds data to a single-board computer and requisite firmware for processing. A custom graphical user interface was also developed in-house to provide controls for inputting desired arm offload values. Additionally, ARC ANGEL features its own power supply that provides power to its subcomponents without external cables. This allows the ability to function independently from ARGOS and further lends itself to potential terrestrial applications.
This work directly correlates to active exosuit development that is being implemented for rehabilitation and/or assistive medical devices. ARC ANGEL is essentially providing a desired assistance (offload) while maintaining a subject’s full range of motion. The system hardware and software can be modified to custom-fit an individual without a spacesuit and toward limb-assisted movement – not just arm offloading. ARC ANGEL may already meet a higher physical demand and robustness given that it is engineered to perform in challenging environments with greater loads.
ARC ANGEL is at a technology readiness level (TRL) 5 (component and/or breadboard validation in laboratory environment) and is now available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale.
Benefits
- Supplies real-time actuation torque offloading
- Programmable offloading simulates zero to 1G
- Software incorporates kinematic algorithms and non-linear control theory for accurate simulation
- Custom graphical user interface facilitates simplified system control
- Compact architecture comprises centrally mounted hardware
- Standalone operation via integrated power supply
- Automatically offloads weight of various hand tools/ equipment
- Reduces arm load and fatigue
- Configurable system could lend itself to terrestrial applications
Applications
- ARGOS reduced gravity simulator arm offloading
- Medical rehabilitation and assistive devices
- Resistance exercise training
- Industrial
- Manufacturing
- Military
Technology Details
Mechanical and Fluid Systems
MSC-TOPS-139
MSC-27646-1
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