Spring Over Muscle

Thomas Sugar (Inventor)

Research output: Patent


Conventional pneumatic muscle actuators apply a uni-directional pulling force. When air pressure is increased in the inner bladder, it expands and presses against a braided material sheath. The radial expansion against the sheath causes the pneumatic muscle to contract. However, this type of actuator cannot apply a pushing force - pairs of actuators are required to achieve bidirectional movement.Researchers at Arizona State University have developed an improved actuator concept known as a 'spring over muscle' (SOM) actuator. A compression spring is added in parallel to the pneumatic muscle. As the passive spring is compressed, it stores energy to be used as a later pushing force. The spring constant and the equilibrium position can be changed to alter the force-deflection curve of the new actuator. The equilibrium position can be changed manually using a nut, or actively controlled using a simple motor device. Software to control the behavior of the SOM actuator has also been developed. A lightweight, high-power bidirectional wearable actuator is now available.
Original languageEnglish (US)
StatePublished - Apr 10 2003


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