High-displacement flexible Shape Memory Alloy actuator for soft wearable robots

Villoslada, Álvaro; Flores, Antonio; Copaci, Dorin; Blanco, Dolores; Moreno, Luís

doi:10.1016/j.robot.2014.09.026

Cited by 123 publications

(88 citation statements)

References 12 publications

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“…The simple SMA-based actuator (with only one SMA wire) used in this work, was presented in [25]. The SMA wire is made of a metallic alloy-the most common between Nickel and Titanium, and called Nitinol [26].…”

Section: Actuator Designmentioning

confidence: 99%

A High-Level Control Algorithm Based on sEMG Signalling for an Elbow Joint SMA Exoskeleton

Copaci¹,

Serrano²,

Moreno³

et al. 2018

Preprint

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Abstract:A high-level control algorithm capable of generating position and torque references from surface electromyography signals (sEMG) has been designed. It is applied to a shape memory alloy (SMA) actuated exoskeleton used in active rehabilitation therapies for elbow joints. The sEMG signals are filtered and normalized according data collected online during the first seconds of therapy sessions. The control algorithm uses the sEMG signals to promote active participation of patients during the therapy session. In order to generate the position reference pattern with good precision, the sEMG normalized signal is compared with a pressure sensor signal to detect the intention of each movement. The algorithm has been tested in simulations and with healthy people for control of an elbow exoskeleton in flexion-extension movements. The results indicate that sEMG signals from elbow muscles in combination with pressure sensors that measure arm-exoskeleton interaction can be used as inputs for the control algorithm, which adapts the reference for exoskeleton movements according a patient's intention.

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Section: Actuator Designmentioning

confidence: 99%

A High-Level Control Algorithm Based on sEMG Signalling for an Elbow Joint SMA Exoskeleton

Copaci¹,

Serrano²,

Moreno³

et al. 2018

Preprint

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“…The actuator chosen to control the displacement of the hanging mass has been a high-displacement flexible SMA actuator first presented in [36] and refined in [37]. The main field of application of this flexible actuator is wearable robotics, more specifically soft exoskeletons and robotic prostheses, where weight reduction is a major design factor and where large displacements and forces are required.…”

Section: Sma Actuatormentioning

confidence: 99%

“…

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mentioning

confidence: 99%

Position control of a shape memory alloy actuator using a four-term bilinear PID controller

Villoslada

Escudero

Alonso-Martín

et al. 2015

Sensors and Actuators A: Physical

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This is a postprint version of the following published document: Villoslada, A.; Escudero, N.; Martín, F.; Flores, A.; Rivera, C.; Collado, M.; Moreno, L. (2015). Position control of a shape memory alloy actuator using a four-term bilinear PID controller. Sensors and Actuators AbstractShape memory alloy (SMA) actuators have a number of appealing features, such as their low weight or their high force-to-weight ratio, that make them a potential alternative to traditional actuation tech-nologies in fields such as space applications, surgical devices or wearable robotics. In this paper, a type of bilinear controller consisting of a conventional PID controller cascaded with a bilinear compensator, known as BPID, is proposed. Bilinear controllers are a subset of nonlinear controllers, which is why the BPID may be a promising alternative to control the position of a SMA actuator. Nonlinear control tech-niques are commonly applied to control SMA actuators, because of their nonlinear behavior caused by thermal hysteresis. The BPID controller is simpler and easier to implement than other nonlinear control strategies, which makes it a very appealing candidate to control SMA actuators. The performance of the BPID controller has been compared with other two controllers, a conventional PID and a commuted feed-forward PIPD, controlling a real SMA actuator. To this end, a set of five tests has been defined, in which the controlled actuator must follow a series of position references. From these tests, the position and error of the actuator have been plotted, and a series of metrics has been computed to have quantitative mea-surements of the performance of the three controllers. It is shown that, in most of the experiments, the BPID has a better performance than the other two tested controllers, especially tracking step references. However, the power consumption is slightly higher when the actuator is controlled with this strategy, although the difference is minimal. Also, the BPID imposes greater energy variations to the SMA actuator, which might affect its service life. Overall, the BPID controller has proved to be a viable alternative to control SMA actuators.

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“…Our research group has developed a new flexible SMA actuator that provides more freedom of movement and a better integration in wearable robots, especially in soft wearable robots. This actuator has been presented in previous works [8] (based on only one SMA wire) and [9]. During the design process of this system, several factors that determine the behavior of the final actuator have been considered.…”

Section: Introductionmentioning

confidence: 99%

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

2019

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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.

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High-displacement flexible Shape Memory Alloy actuator for soft wearable robots

Cited by 123 publications

References 12 publications

A High-Level Control Algorithm Based on sEMG Signalling for an Elbow Joint SMA Exoskeleton

A High-Level Control Algorithm Based on sEMG Signalling for an Elbow Joint SMA Exoskeleton

Position control of a shape memory alloy actuator using a four-term bilinear PID controller

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

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