Multi-Objective Design Optimization of a Shape Memory Alloy Flexural Actuator

• Main Authors: Casey D. Haigh, John H. Crews, Shiquan Wang, Gregory D. Buckner
• Format: Article
• Language: English
• Published: MDPI AG 2019-02-01
• Series: Actuators
• Subjects: shape memory alloy; microscale actuation; design optimization; genetic algorithm
• Online Access: https://www.mdpi.com/2076-0825/8/1/13

This paper presents a computational model and design optimization strategy for shape memory alloy (SMA) flexural actuators. These actuators consist of curved SMA wires embedded within elastic structures; one potential application is positioning microcatheters inside blood vessels during clinical treatments. Each SMA wire is shape-set to an initial curvature and inserted along the neutral axis of a straight elastic member (cast polydimethylsiloxane, PDMS). The elastic structure preloads the SMA, reducing the equilibrium curvature of the composite actuator. Temperature-induced phase transformations in the SMA are achieved via Joule heating, enabling strain recovery and increased bending (increased curvature) in the actuator. Actuator behavior is modeled using the homogenized energy framework, and the effects of two critical design parameters (initial SMA curvature and flexural rigidity of the elastic sleeve) on activation curvature are investigated. Finally, a multi-objective genetic algorithm is utilized to optimize actuator performance and generate a Pareto frontier, which is subsequently experimentally validated.