Innovators at NASA Johnson Space Center, in collaboration with Oceaneering and The Florida Institute for Human and Machine Cognition, have developed the Split-Ring Torque Sensor (SRTS), a device that uses optical sensors to measure the position, velocity, and torque of a rotating system.

The SRTS was created for use in NASA’s X1 robotic exoskeleton, an in-space, wearable exercise machine designed to supply resistance against leg movement for NASA astronauts in future missions. The X1 exoskeleton implements the SRTS in its belt-drive series elastic actuator (SEA) and provides a lower profile and lower-weight system than competing designs.

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, copla-nar 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.

The SRTS offers greater flexibility in tailoring for specific applications and requirements. In addition to its applications in robotics, the SRTS has potential uses in medical fields including prosthetics, aerospace and defense applications, automotive applications, testing and measurement, and industrial markets.

NASA is actively seeking licensees to commercialize this technology. Please contact NASA’s Licensing Concierge at This email address is being protected from spambots. You need JavaScript enabled to view it. or call us at 202-358-7432 to initiate licensing discussions. Follow this link here  for more information.


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This article first appeared in the February, 2021 issue of Tech Briefs Magazine.

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