Shape memory alloy (SMA) actuators and devices including bio-inspired shape memory alloy composite (bismac) actuators

Abstract

An actuator comprising a flexible spring affixed at a separation distance from a shape memory alloy or artificial muscle element amplifies strain developed by the shape memory alloy or artificial muscle element while maintaining a substantial fraction of the force developed during activation of the shape memory alloy or artificial memory element. A plurality of such actuators positioned relative to each other by encapsulation or attachment to a body of material such as a terminal hub can emulate a wide variety of biological movements such as for providing gripping in the manner of an opposed human thumb or propulsion in the manner of a jellyfish.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims benefit of priority of U S. Provisional Application 61 / 421,847, filed Dec. 10, 2010, which is hereby incorporated by reference in its entirety.STATEMENT OF GOVERNMENT INTEREST[0002]Development of this invention was sponsored by the Office of Naval Research through contract number N00014-08-1-0654. The U.S. Government may have certain rights in this invention.FIELD OF THE INVENTION[0003]The present invention generally relates to actuators employing shape memory alloy (SMA) elements and, more particularly, to bio-inspired shape memory alloy composite (BISMAC) actuators and devices employing them including a propulsion system for a submersible vessel emulating a species of fish such as an Aurelia aurita species of jellyfish.BACKGROUND OF THE INVENTION[0004]During the progress of science in regard to materials and their physical properties, many new materials have been developed that exhibit unusual physical properties...

AI Technical Summary

Benefits of technology

The present invention provides an actuator that uses SMA material to amplify its range of motion. It also utilizes shape memory effects to provide a range of motion comparable to biological muscle tissue. The actuator includes a flexible spring beam, a shape memory alloy or artificial muscle element, and a connection between them that maintains a separation distance. Additionally, the invention provides an efficient propulsion system for a water-borne vehicle. The actuator can be used in an apparatus with multiple actuators, where each actuator includes a flexible spring beam, a shape memory alloy or artificial muscle element, and a connection between them that maintains a separation distance.

Problems solved by technology

Few, if any, new devices have been developed that uniquely exploit the properties of SMAs for useful purposes.

For example, while the light weight of SMA materials and the smooth, easily controllable forces that SMA materials can develop, which are similar to those produced by muscle tissue, suggest uses in robotics and prosthetic devices, few, if any, successful applications have been developed, even for devices of known types for robotic or prosthetic applications.

To obtain larger degrees of motion from the shape memory effect, itself, the elastic deformation must be augmented by recoverable plastic deformation from a force developed externally to the SMA material, generally requiring the use of another powered actuator which largely defeats the advantages to be derived from use of an SMA material and still yields only a relatively small motion.

Additionally, while the required transition temperature can be chosen in accordance with an application (e.g. slightly above body temperature for a prosthetic device) the temperature excursion above the transition temperature to produce the shape memory effect in a suitably short time may be difficult to accommodate.

These problems of application of SMA materials appear to have largely precluded development of novel structures that can optimally exploit their properties.

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