Space Suit RoboGlove (SSRG)
robotics automation and control
Space Suit RoboGlove (SSRG) (MSC-TOPS-80)
Advancements in spacesuit robotic glove may yield terrestrial benefits
Overview
Innovators at NASA Johnson Space Center (JSC) have created an enhanced second-generation, robotically assisted extravehicular activity (EVA) glove. The SSRG has been engineered to further decrease the exertion required to do complex, hand-intensive EVA tasks and reduce the risk of astronaut hand injury. Originating from its predecessors, the NASA/General Motors RoboGlove, and the later first-generation Space Suit RoboGlove, the SSRG realizes improved sensing, control, interface, and avionics capabilities. Among these improvements is the implementation of a power steering mode, which allows the user to position his/her fingers in an arbitrarily chosen position and receive assistance in holding that position. The SSRG retains the ability to operate like a conventional space suit glove while the actuators are unpowered. The design intent for the SSRG is to enhance a users ability to perform human scale work, with considerations for speed, power, durability, dexterity, and ease of operation.
The Technology
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 astronauts 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 SSRGs 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.
Benefits
- Power-steering mode allows user to receive assistance holding arbitrarily chosen position
- Decreases exertion required to do complex, hand-intensive tasks
- Reduces risk of hand injury
- New actuator realizes greater force output, increased efficiency, higher thermal mass, improved reliability, and ease of maintenance
- Improved sensing, control, interface, and avionics capabilities over first-generation glove
- Capable of providing 9 assistive modes
- Back drivability of actuators ensures user unpowered mobility
Applications
- Manufacturing: operation of hand tools and hand-gripping manual labor for extended periods of time
- Healthcare: development of rehabilitation aids, and assistance of patients with impaired hand muscle strength
Technology Details
robotics automation and control
MSC-TOPS-80
MSC-26236-1
MSC-26273-1
MSC-26236-2
MSC-26273-2
Similar Results
Robo-Glove
Originally developed by NASA and GM, the Robo-Glove technology was a spinoff of the Robonaut 2 (R2), the first humanoid robot in space. This wearable device allows the user to tightly grip tools and other items for longer periods of time without experiencing muscle discomfort or strain. An astronaut working in a pressurized suit outside the space station or an assembly operator in a factory might need to use 15 to 20 lbs of force to hold a tool during an operation. Use of the Robo-Glove, however, would potentially reduce the applied force to only 5 to 10 lbs.
The Robo-Glove is a self-contained unit, essentially a robot on your hand, with actuators embedded into the glove that provide grasping support to human fingers. The pressure sensors, similar to the sensors that give R2 its sense of touch, are incorporated into the fingertips of the glove to detect when the user is grasping an object. When the user grasps the object, the synthetic tendons automatically retract, pulling the fingers into a gripping position and holding them there until the sensor is released by releasing the object. The current prototype weighs around two pounds, including control electronics and a small display for programming and diagnostics. A lithium-ion battery, such as one for power tools, is used to power the system and is worn separately on the belt.
Tri-Rotor Steering Wheel Yields Programmable Vehicular Control
Since NASAs Apollo program of the late 1960s and 1970s, many previous LTV hand controllers (e.g., joysticks, T-handles) were developed and utilized albeit with shortcomings. Some of these options yielded the desired level of control but were too physically taxing to use for long periods of time in a spacesuit environment. Others simply did not offer the necessary fine motor control. Thus, there has been a long-standing need for controllers that improve upon both of these limitations.
The Tri-Rotor is a novel hand controller designed to reduce operator fatigue, add control capabilities (beyond those of a joystick), and increase the fidelity of control inputs. The design consists of two slotted handles that rotate independently within opposite sides of the Tri-Rotor main-body. Each handle is programmable and can rotate 45 degrees. In this iteration, the right handle rotates counterclockwise and acts as an accelerator and brake. The left handle rotates both clockwise and counterclockwise and controls crabbing whereby the vehicles rear wheels turn in the same direction as the front wheels facilitating diagonal or possibly lateral movement. The main-body of the Tri-Rotor rotates upon a central pivot like an automotive steering wheel and can provide directional input for Ackermann-like steering.
The handles on the Tri-Rotor are designed with spacesuit kinematics in mind and are operated using the pronated and supinated motions of the astronauts hands allowed by the wrist bearings between the glove and the forearm of the spacesuit. The devices central steering pivot is also operated by the hands and is leveraged by the up and down motions of the arms allowed by the constant volume joints in the spacesuits shoulders. This hand controller design staves off operator fatigue and sheds the need for separate fine-dexterity controls without sacrificing precision.
The Tri-Rotor Hand Controller has a technology readiness level (TRL) 5 (component and/or breadboard validation in relevant environment) and is now available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale.
Advanced Robotic Sensing Technologies
Visual Perception System: Key to enabling humanoid robotics to perform dexterous tasks, R2’s visual perception system (U.S. Patent No. 8,244,402) – comprised of machine vision cameras, processors, and novel algorithms – allows robots to find, track, and measure objects automatically in their field of view.
Tendon Tension Sensor: Unique tendon tensions sensors (U.S. Patent Nos. 8,371,177 & 8,056,423) are embedded in R2’s palms to enable granular force control of the fingers via a redundant network of tendons. R2’s tendons are coupled to, and used to actuate, the robot’s finger joints. Thus, tendon tension measurements provided by the sensor allow for the external loads experienced by its robotic fingers to be derived.
Tactile System: R2’s hands feature an innovative tactile system that grant the robot a sense of touch (e.g., measurement of external contact forces, shear force, and slippage of objects held in the hand) – an important requirement for robots designed to perform complex tasks in an automated fashion. The tactile system is enabled by novel six degree of freedom (DoF) force torque sensors (U.S. Patent No. 7,784,363), which are integrated into the fingers at each phalange (14 per hand). A calibration system (U.S. Patent No. 8,265,792) ensures the sensors maintain high accuracy throughout operation.
Contact State Estimation: A contact state estimation sensor (U.S. Patent No. 8,280,837), based on the use of a particle filter, enables R2 to perceive the location, orientation, and shape of objects when in contact with the robot’s hands (i.e., tracks hand-object state). The contact state estimation system leverages a novel motion model, which characterizes the motion of a robotic hand as it moves relative to an object of interest.
Series Elastic Actuator (SEA) Sensing: R2’s SEAs achieve fine torque sensing at each of its joints without sacrificing strength or payload capacity. The robot uses two 19-bit absolute angular position sensors, calibrated using a novel technique (U.S. Patent No. 8,250,901), to measure the deflection of each spring in real time.
Foot Pedal Controller
The Foot Pedal Controller enables an operator of a spacecraft, aircraft, or watercraft, or a simulation of one in a video game, to control all translational and rotational movement using two foot pedals. This novel technology allows control across all six degrees of freedom, unlike any technology on the market. The components of the technology are a support structure, a left foot pedal, a right foot pedal, and supporting electronics. The Foot Pedal Controller is intuitive, easy to learn, and has ergonomic features that accommodate and stabilize the operator's feet. A working prototype is available to demonstrate key technology features to potential licensees.
The Foot Pedal Controller technology could be used in designs for the flight deck of the future, video game controls, drone operations and flight simulators. This technology can be useful in any application where it is preferred or desirable to use the feet to control motion rather than using the hands. A potential market could be foot control of equipment by people with arm or hand disabilities. A unique aspect of the innovation is the consideration of natural foot mechanics in the design and placement of the sensors and actuators to reduce operator fatigue. The axes of rotation of the Controller align with the joints of the foot so the foot moves naturally to control the movement of the craft. NASA seeks collaborations with companies interested in licensing and partnering to further develop and commercialize the technology.
Split-Ring Torque Sensor
The SRTS enables measurement of position, velocity, and torque of a rotating system (e.g., actuator, motor, crankshaft, rotor, etc.) using two optical sensors and a single, custom-designed split-ring rather than the standard dual-ringed systems commonly used for similar applications. The split-ring is comprised of two structural arcs positioned in a concentric, coplanar relationship, wherein each arc is attached to a component capable of rotation (e.g., a lower leg and upper leg, where the SRTS acts as a knee). The two arcs contain indications or codes on their outer surfaces that are read by the optical sensors to determine the relative deflection of the structural arcs as they rotate.
The SRTS configuration discussed above is limited to 180-degree applications. The addition of a third structural arc and a third optical reader, however, would enable 360-degree functionality.
Tests have shown the SRTS has a high degree of tolerance to temperature differences and provides higher resolution measurements than competing technologies.