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 adds arm offloading to gravity field simulator
Overview
Innovators at NASA Johnson Space Center (JSC) have developed an earthbound robotic training system that can actively simulate an astro-naut’s weightlessness in space. The Active Response Gravity Offload System (ARGOS) comprises an overhead runway and bridge drive system that can partially or fully offload the weight of a test subject using cables, effectively suspending them off the ground, to simulate a reduced gravity environment for them to train. Although the test subject’s torso and legs are offloaded, their arms and any weighty hand tools are not.
The Actuated Realtime Control for ARGOS Negation of Gravitational Effects on the Limbs (ARC ANGEL) technology was developed to offload a space suited test subject’s arms and counteract fatigue realized by them while performing training activities using ARGOS. ARC ANGEL provides arm offloading for test subjects via computer-controlled active cable tension. Cables are strung between attachment points located on arm cuffs just above each elbow, and a motorized reel mounted to the spacesuit’s backpack-like Primary Life Support System (PLSS).
This active load offsetting technology could be used for a number of applications other than simulating zero to one G environments. These applications may include medical rehabilitation and exercise, industrial and military environments, or any environment in which the offloading of one’s arms and tools could lend benefits such as increased productivity, and reduction of injuries.
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 supplies real-time actuation torque offloading 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, 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
|
Tags:
|
Similar Results
Full-Size Reduced Gravity Simulator For Humans, Robots, and Test Objects
The Active Response Gravity Offload System (ARGOS) provides a simulated reduced gravity environment that responds to human-imparted forces. System capabilities range from full gravity to microgravity. The system utilizes input/feedback sensors, fast-response motor controllers, and custom-developed software algorithms to provide a constant force offload that simulates reduced gravity.
The ARGOS system attaches to a human subject in a gimbal and/or harness through a cable. The system then maintains a constant offload of a portion of the subjects weight through the cable to simulate reduced gravity. The system supports movements in all 3 dimensions consistent with the selected gravity level. Front/back and left/right movements are supported via a trolley on an overhead runway and bridge drive system, and up/down movements are supported via a precisely positioned cable. The system runs at a very high cycle rate, and constantly receives feedback to ensure the human subjects safety.
Computer Vision Lends Precision to Robotic Grappling
The goal of this computer vision software is to take the guesswork out of grapple operations aboard the ISS by providing a robotic arm operator with real-time pose estimation of the grapple fixtures relative to the robotic arms end effectors. To solve this Perspective-n-Point challenge, the software uses computer vision algorithms to determine alignment solutions between the position of the camera eyepoint with the position of the end effector as the borescope camera sensors are typically located several centimeters from their respective end effector grasping mechanisms.
The software includes a machine learning component that uses a trained regional Convolutional Neural Network (r-CNN) to provide the capability to analyze a live camera feed to determine ISS fixture targets a robotic arm operator can interact with on orbit. This feature is intended to increase the grappling operational range of ISSs main robotic arm from a previous maximum of 0.5 meters for certain target types, to greater than 1.5 meters, while significantly reducing computation times for grasping operations.
Industrial automation and robotics applications that rely on computer vision solutions may find value in this softwares capabilities. A wide range of emerging terrestrial robotic applications, outside of controlled environments, may also find value in the dynamic object recognition and state determination capabilities of this technology as successfully demonstrated by NASA on-orbit.
This computer vision software is at a technology readiness level (TRL) 6, (system/sub-system model or prototype demonstration in an operational environment.), and the software is now available to license. Please note that NASA does not manufacture products itself for commercial sale.
Robonaut 2: Medical Opportunities
R2's unique systems allow the robot to be used in many telemedicine applications and in many medical scenarios. For example, R2 can assist a surgeon and the surgical team before, during, and after a procedure with multiple tasks. The robot has the vision, dexterity, and the ability to perform tasks tirelessly 24 hours a day, seven days a week. R2 can work safely around humans, so it can be integrated into a dynamic hospital environment.
The R2 technology capabilities in telemedicine are being explored through partnerships with medical institutions. After a quick medical procedure training, a R2 teleoperator was able to guide the robot and perform an ultrasound scan on a medical mannequin. Humans at the controls were able to guide the robot to perform the task correctly and efficiently by using R2's dexterity to apply the appropriate level of force and were able to track their progress using the robot's vision system. The technology was also used to experiment using a syringe and an intubation procedure with a mannequin to demonstrate R2's telemedicine capabilities. R2 is well suited to be used by physicians to conduct medical procedures on humans in remote locations.
Advanced Humanoid Robotic Arm Technologies
R2 uses brushless DC motors, harmonic drive gear reductions, and electromagnetic failsafe brakes as the building blocks for the powerful, torque-dense actuators in its human-scale, 5 DoF upper arms. Moreover, the use of series elastic actuators and novel tension sensing & control systems represent some of the most innovative technologies present in the humanoid robotic arms of R2.
Series Elastic Actuators (SEAs): R2’s SEAs achieve fine torque sensing at each of its joints without sacrificing strength or payload capacity. Such capabilities are enabled through the development of several advanced technologies. Specifically, novel planar torsion springs (U.S. Patent No. 8,176,809) are integrated into each rotary series elastic actuator (U.S. Patent No. 8,291,788), while two absolute angular position sensors, calibrated using a novel technique (U.S. Patent No 8,250,901), measure the deflection of each spring. Force and Impedance Control Systems (U.S. Patent No. 8,525,460): These systems use position sensor signals for sending position data to an embedded processor that determines the positional orientation of the load relative to a motor shaft and its related torque on a string. A FPGA-based controller (U.S. Patent No. 8,442,684) provides a high-speed (10 KHz) control loop for the electric motor and gear reduction assembly present in R2 joints.
Tension Sensing & Control of Tendon-Based Robotic Manipulators: NASA has also developed technologies to provide tension sensing & control of humanoid robotic arms. First, a tendon tension sensor (U.S. Patent No. 8,371,177) measures strain on tendons (strings) employed in robotic arms. A novel calibration system (U.S. Patent No. 8,412,378) calibrates the tendon tension sensors. Finally, joint space impedance control systems (U.S. Patent Nos. 8,170,718 & 8,060,250) provide closed-loop control of joint torques or joint impedances without inducing dynamic coupling between joints, as well as programmable Cartesian arm stiffness.
Space Suit RoboGlove (SSRG)
NASA is currently developing the next generation space suit for future missions, including the optimization of space suit gloves. When non-assisted space suit gloves are coupled to a pressurized suit and operated in a vacuum, they tend to limit the range of motion of an astronaut's hand to as little as 20% of normal range. Many of NASA's future missions will be in challenging environments where an astronaut’s hand dexterity will be critical for the success of NASA missions. Innovators at JSC have improved the performance on the second-generation, robotically assisted SSRG, to reduce exertion and improve the hand strength and dexterity of an astronaut in situ.
The SSRG’s system detects user finger movements using string potentiometers and contact with objects using force-sensitive resistors (FSRs). FSRs are imbedded in the distal and medial phalanges, palmar side of the glove. To move a finger, an actuator pulls a tendon through a Bowden Cable system which transfers mechanical pulling force of an inner cable relative to a hollow outer cable, like the brakes on a bicycle, as seen in the Figure below. An improved controller commands the new, more powerful linear actuator to drive tendon operation while minding custom controller parameters inputted through a digital editor tool.
The Space Suit RoboGlove is at TRL 6 (system/subsystem model or prototype demonstrated in a relevant environment) and it is now available for licensing. Please note that NASA does not manufacture products itself for commercial sale.
