Shape Memory Alloy (SMA) Actuators and Their Applications

Dear Colleagues,

In recent years, emerging actuators such as shape memory alloy (SMA)-based actuators have made it possible to overcome the current limitations of conventional actuators by being integrated into various applications, including medical robotics, rehabilitation robotics, automotive and aerospace industry applications, and more.

Due to their promising properties, SMA-based actuators have received much attention from researchers, where topics related to materials, actuator design, and control are addressed to improve their performance depending on the final application.

This Special Issue addresses research on SMA-based actuators from fundamental studies to their final applications. Original research and review articles are recommended. Topics include, but are not limited to, the following:

• Control of SMA actuators;
• Emerging design and fabrication of SMA actuators;
• Performance assessment of SMA (e.g., electrical power consumption, efficiency);
• Sensorless actuator;
• SMA actuators for robotic applications.

Dr. Dorin Sabin Copaci
Prof. Dr. Maria Dolores Blanco Rojas
Prof. Dr. Luis Enrique Moreno Lorente
Guest Editors

Manuscript Submission Information

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• shape memory alloy actuator
• actuator design
• control
• sensorless actuator
• modeling

Title: Design of a Release Mechanism for a Folding Tail Using Shape Memory Alloy
Authors: Yan Cheng, Chao Ren, Jun Wang, Xiaojun Gu, Yahui Zhang, Jihong Zhu, Weihong Zhang
Affiliation: Northwestern Polytechnical University
Abstract: This paper introduces a novel design method for SMA (Shape Memory Alloy) actuators aimed at engineering applications. The method incorporates installation space constraints to assist in the selection and design of SMA driving components and springs, thereby achieving higher design precision and practicality. Using the folding tail of a UAV (Unmanned Aerial Vehicle) as the application background, the new design method was employed to test and characterize the material and driving performance of SMA wires. The theoretical models of the kinematics and dynamics of the folding tail were derived. The design utilizes a torsion spring as the driving source for the folding tail and employs a 0.3mm SMA wire and spring to create a three-pin linkage bias-type locking device. This device integrates locking and unlocking functions in two modes, forming a novel folding tail system. Finally, a prototype was manufactured and functionally validated. Test results show that the maximum response time of the locking device is 0.5 seconds, the actuation time is less than 20 milliseconds, the actuation length exceeds 2 millimeters, and it passed environmental reliability verification, proving the effectiveness of the design.

Title: The Potential of Shape Memory Alloys in Riveting Applications
Authors: Edgar Camacho1, Patrícia Freitas Rodrigues*1, João Pedro Oliveira2, Francisco Braz Fernandes2
Affiliation: 1University of Coimbra, CEMMPRE-ARISE, Department of Mechanical, Portugal 2 NOVA School University, CENIMAT-i3N, Department of Materials Science, Portugal
Abstract: This study explores the use of shape memory alloys, specifically Nickel-Titanium (NiTi- Ti rich), in plate joining processes through riveting. Through the shape memory effect (SME), SMAs offer innovative solutions for the joining of components, mainly in the aeronautical and aerospace fields, indicating promising applications. This research presents several characterizations, including differential scanning calorimetry, compression dilatometry, X-rays diffraction using synchrotron radiation and thermomechanical testing, to assess the feasibility and performance of shape memory alloys rivets. In addition, the samples were subject to recrystallization heat treatment to evaluate their reusability. The results demonstrated that shape memory alloys rivets are effective, achieving a maximum load of 340 N for two joined components. However, their application is optimal for materials with yield strengths lower than the stress-induced SME. Moreover, the process enhances the hardening of the joined components and increases the thermal hysteresis of the rivet. This research confirms the viability of shape memory alloys in riveting processes, offering a new avenue for advanced joining techniques. The findings provide a foundation for further development and application in various industries requiring precise and reliable joining methods.