Circumferential Scissor Spring Enhances Precision in Hand Controllers

Johnson Space Center, Houston, TX

Three-quarter view of three-axis analog hand controller (left) engineered with Circumferential Scissor Springs, and side view of controller (right) with control stick being pushed inward, initiating circumferential spring return-tension. (Image: NASA)

Innovators at NASA’s Johnson Space Center have designed a circumferential scissor spring mechanism, that when incorporated into a hand controller, improves the restorative force to a control stick’s neutral position. The design also provides for operation on a more linear portion of the spring’s force deflection curve, yielding better feedback to the user. Physical hand controllers, such as translational and rotational controllers, use a non-circumferential scissor spring arrangement to return the control stick to a neutral position, but the linear response of a typical scissor spring arrangement can reduce a user’s sense of control by allowing slack between deflections.

This design is driven by a spring mechanism whereby an expansion spring is looped around the channeled circumference of two rounded pivoting blades whose setup can be tuned to allow varying spring tension. This allows the user enhanced control stick sensitivity while operating drive systems, industrial automation, measuring technology, mobile machinery, and gaming systems. This technology is currently implemented on NASA’s Orion Spacecraft training simulators using three-axis hand controllers.

The traditional scissor spring design for hand controllers has been improved upon with a circumferential spring controller mechanism that facilitates easy customization, enhanced durability, and optimum controller feedback. These advantages are partially facilitated by locating the spring to the outside of the mechanism which allows for easier spring replacement to adjust the deflection force or for maintenance. The new mechanism is comprised of two rounded blades, or cams, that pivot forward and back under operation and meet to form a circle.

An expansion spring is looped around the blade perimeter and resides in a channel, providing the restoring force that returns the control stick to a neutral position. Due to the use of a longer circumferential spring, the proportion of spring expansion is smaller for a given distance of deflection, so the forces associated with the deflection remain on a more linear portion of the force deflection curve.

The technology has several potential applications including aerospace: spacecraft, aircraft, remotely operated reconnaissance vehicles; industrial and military: mobile machinery, drive system and remote valve operation, hazardous environment vehicles, weaponry; and entertainment: gaming controllers, drones.

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 at 202-358-7432 to initiate licensing discussions. For more information, visit here .