Miniature High Force, Long Stroke Linear Shape Memory Alloy Actuators

Shape Memory Alloys (SMAs) are metal alloys (Nickel-Titanium, for example) that change shape when heated. When drawn and processed in wire form, the shape change is an aggressive contraction with useable lifetimes of millions of cycles. Despite this fact, SMAs have largely been a scientific curiosity, finding very little commercial use as actuators since their discovery over 30 years ago. The apparent lack of practical application may be due to their low recoverable strain (~4% of total wire length). MIGA Motor Company has numerous international patents covering Displacement Multiplication (DM) techniques that allow us to package strokes of over 1 inch in highly compact, lightweight packages. Our current commercially available linear actuators provide 1/2" of stroke with 4.5 pounds of output force. We propose to develop several high force variants of the DM designs, allowing up to 45 pounds of force in a device weighing less than 2 ounces. The manufacturing techniques that we have developed in manufacturing the DM actuators have paved the way to expansion into the high force realm: high reliability wire attachment methods, use of high temperature thermoplastics, Teflon-coated or over-molded precision chemically-etched stainless-steel motive elements, and various load-sharing techniques have enabled the design of these actuators to finally become a reality.