Flexible Shape-Memory Alloy-Based Actuator: Mechanical Design Optimization According to Application

Abstract

New robotic applications, among others, in medical and related fields, have in recent years boosted research in the development of new actuators in the search for solutions that are lighter and more flexible than conventional actuators. Shape-Memory Alloy (SMA)-based actuators present characteristics that make them an excellent alternative in a wide variety of applications. This paper presents the design, tests (with the control description) and analysis of various configurations of actuators based on SMA wires: flexible SMA actuators, different mechanical design to multiply the displacement and different configurations for actuators with multiple SMA wires. The performance of the actuators has been analyzed using wires of different activation temperatures. The influence of the Bowden sheath of the flexible actuator has been tested, as has the thermal behavior of actuators with several wires. This work has allowed determination of the most effective configuration for the development of a flexible actuator based on SMA, from the point of view of dimensions, efficiency, and work frequency. This type of actuator has been applied in the development of soft robots and light robotic exoskeletons.

Efficiency Analysis of SMA-Based Actuators: Possibilities of Configuration According to the Application

“…Electrical power and energy consumption were higher for Actuator 3 (with Bowden cable; 8.1 W and 3401 J, respectively) compared with Actuator 1 (4.47 W and 1880 J, respectively) for 420 s. This high electrical power consumption is largely due to the first cycles of work where the heat is quickly dissipated. For actuators with a Bowden cable and multiple wires, the electrical power consumption is less when the wires are in the same Bowden cable compared with the case where each wire is in an independent Bowden cable, but this implies that the position error will be greater [15].…”

“…Pathak et al [10] and Tadesse et al [11] studied thermal grease as an SMA heat sink. The authors of [13][14][15] presented different SMA actuators composed of multiple SMA wires, which improve the work frequency of the actuator. Although these methods improve the cooling process, they increase the complexity of the actuator structure, introducing new components.…”

SMA-Driven Soft Robotic Neck: Design, Control and Validation

“…However, this platform is designed as a prototype concept, to demonstrate the feasibility of a soft and bio-inspired system, where the actuators can be configured according to the final application. For example, we can use multi-wire actuators [32] with a smaller diameter (Table 1) for fast cooling or actuators with multiple wires and the same diameter (0.51 mm) to increase the total force of the platform, without changing the structure of the neck platform. Some tests were carried out and the most relevant data were collected to compare the actual positions of the neck platform with the references.…”

“…Our research group already presented in [32] an analysis of different configurations of SMA actuators with one or more SMA wires and the effect of the Bowden cable on the structure of the actuator. In this experiment we have chosen to use an actuator based on one SMA wire, a PTFE tube and a Bowden cable.…”

State of the art in processing of shape memory alloys with electrical discharge machining: A review

“…Among them, there are mainly three alloy systems reported, namely; NiTi-based, Copper-based (CuZnAl and CuAlNi), and Iron-based. 5 The demand for SMAs has been quite increasing in respect of engineering and technical applications in several commercial fields such as; in user goods and various applications in the industry, 6–8 composites and structures, 9 automobile, 10–12 robotics, 13–16 biomedical, 15,17–20 aerospace, 21–23 mini actuators and micro-electromechanical systems (MEMS), 15,17,24–27 and even in fashion. 28 However, for specific requirements or applications, each type of SMM has its advantage.…”