A Novel, Scalable Shape Memory Alloy Actuator Controlled by Fluid Temperature

This paper presents the basic performance evaluation of a design concept for linear scalable Shape Memory Alloy (SMA) wire actuators controlled by the temperature of a liquid. Fluid heat transmission with SMA wires, contrasting with Joule heating, allows the design to provide scalability of its maximum output force and displacement by changing the arrangement of the wires. The purpose of this design concept is to have an actuator that can scale output energy with minimum changes in footprint or power source. Two prototypes using this design concept were tested in an isometric experiment to contrast its force vs. temperature response, as well as its thermal response time. Both prototypes successfully achieved force output scalability by changing the number of parallel actuating SMA wires in a range from ten to forty. In addition, with the second design, the force rise time was reduced by 92%, and the force fall time was reduced by 95%, as compared with the first design, by the addition of flow heat transmission. This design concept allows an actuator to be adapted to changing specifications by customizing its output characteristics and could potentially provide further flexibility to robotic systems.