Search

This paper comprehensively reviews effective control applications using shape memory alloy (SMA) actuators. Among many applications, this paper focuses on the vibration and stiffness control of flexible structures and shape control in the aerospace engineering field. In the vibration control of flexible structures, three different methods are introduced and discussed, including their merits and demerits. In addition, several control strategies, such as neuro-fuzzy controller, are investigated in terms of the implementation associated with the microchip. In the control process, the inherent hysteretic behavior of SMA is also reviewed as a feedforward loop or actuating force compensator. At the second part, applications on the morphing wing in the field of aerospace engineering are reviewed, and salient characteristics are discussed. In this review, the morphing wing, which is closely related to aircraft stability, is mainly investigated considering control logics and geometrical parameters. For easily understanding morphing control using SMA, a table which summarizes the main contribution of each research is presented. It is expected, since this review article provides numerous approaches for vibration and morphing control conducted over the last decade, it will be very helpful to the same research community to create novel ideas to achieve more advanced and effective results in vibration and morphing control using SMA actuators. [ABSTRACT FROM AUTHOR]

Leveraging advances in shape memory alloys (SMAs) and flexible thermoelectric devices (f-TEDs), this paper presents a structural and functional integrity composite sheet to address the inefficient and bulky activation of 2-D SMAs. A series of experimental tests were performed to reveal the generation, change, and transfer mechanisms of different types of electrically-induced heat in the f-TED, as well as the temperature-induced SMA phase transformation behaviors. The results show that the composite sheet exhibited good bidirectional thermal management capacity. The austenite deformation can be completed within 10s at an operating current of 2 A. The cooling recovery, in particular, performs much better than in conventional modes (the temperature declines exponentially with time). Finally, through two functional prototypes, a light switch and a flexible gripper, the application potential of the proposed composite was further experimentally demonstrated. [ABSTRACT FROM AUTHOR]

To achieve the control of a small-sized robotmanipulator, we focus on an actuator using a shape memory alloy (SMA). By providing an adjusted voltage, an SMA wire can itself generate heat, contract, and control its length. However, a strong hysteresis is generally known to be present in a given heat and deformation volume. Most of the control methods developed thus far have applied detailed modeling and model-based control. However, there are many cases in which it is difficult to determine the parameter settings required for modeling. By contrast, iterative learning control is a method that does not require detailed information on the dynamics and realizes the desired motion through iterative trials. Despite pioneering studies on the iterative learning control of SMA, convergence has yet to be proven in detail. This paper therefore describes a stability analysis of an iterative learning control to mathematically prove convergence at the desired length. This paper also details an experimental verification of the effect of convergence depending on the variation in gain. [ABSTRACT FROM AUTHOR]

Soft actuators that execute diverse motions have recently been proposed to improve the usability of soft robots. Nature-inspired actuators, in particular, are emerging as a means of accomplishing efficient motions based on the flexibility of natural creatures. In this research, we present an actuator capable of executing multi-degree-of-freedom motions that mimics the movement of an elephant's trunk. Shape memory alloys (SMAs) that actively react to external stimuli were integrated into actuators constructed of soft polymers to imitate the flexible body and muscles of an elephant's trunk. The amount of electrical current provided to each SMA was adjusted for each channel to achieve the curving motion of the elephant's trunk, and the deformation characteristics were observed by varying the quantity of current supplied to each SMA. It was feasible to stably lift and lower a cup filled with water by using the operation of wrapping and lifting objects, as well as effectively performing the lifting task of surrounding household items of varying weights and forms. The designed actuator is a soft gripper that incorporates a flexible polymer and an SMA to imitate the flexible and efficient gripping action of an elephant trunk, and its fundamental technology is expected to be used as a safety-enhancing gripper that requires environmental adaptation. [ABSTRACT FROM AUTHOR]

The magnetic field-induced stress and strain of magnetic shape memory alloy (MSMA) are fundamental to describe its magnetomechanical behavior. In order to investigate the operating characteristics of MSMA-based actuator, this paper presents a 3-D quasi-static modeling approach of magnetomechanical behavior of MSMA with the improved constitutive equation by introducing the activation field strength. The relationships between three critical parameters of the activation field strength, the maximum of strain, as well as the saturation field strength, and the pre-compressing force are obtained by fitting the data collected from the experiment. Two kinds of test specimen in different geometric dimensions are studied by the numerical modeling method. Considering that the key material parameters vary dramatically depending on the size and composition, verifications through experiments show that this numerical modeling and simulation can accurately describe the force and deformation characteristics of MSMA. The modeling analysis and simulation results are significant to design of the actuator based on MSMA to predict the actuator performance under the given working conditions. [ABSTRACT FROM AUTHOR]

A Nitinol hydraulic bellows actuator for the application in minimally invasive surgeries (MIS) has been designed and manufactured. Such application required the actuator to be elastically deformable. This paper explains how the actuator geometry is optimized for large deformations and shows the feasibility of an actuator manufactured by selective laser melting (SLM). Four different shapes were virtually tested using finite element analyses (FEA). Furthermore, multiple samples of the bellows actuator with a U-shaped deformation zone were simulated and manufactured. A test rig was developed to measure deformation and achievable force. Physical tests showed a sufficient performance of the actuator for typical applications in minimal invasive surgery. Technical challenges and potential solutions on the current state of development are discussed. [ABSTRACT FROM AUTHOR]

With the development of micromotion actuation technology, smart material-based actuators are more promising in micro/nanopositioning field. As a typical example of smart material-based actuators, magnetical shape memory alloy actuator has been applied in nanopositioning stages due to its extremely innovative properties such as high precision nanoscale positioning and large stroke. However, the inherent hysteresis nonlinearity of the magnetical shape memory alloy material affects the performance of the magnetical shape memory alloy-based actuator in the field of high precision positioning. The hysteresis characteristics of the magnetical shape memory alloybased actuator are related to many factors. This paper is devoted to study the effect of driving signal and external temperature on the displacement of the magnetical shape memory alloy-based actuator. Firstly, the structure and principle of the magnetical shape memory alloy-based actuator are introduced. Then the displacement curves of the magnetical shape memory alloy-based actuator are tested under different input frequencies, amplitudes, and environment temperatures. Finally, the hysteresis characteristics of the magnetical shape memory alloy-based actuator under different driving signals and environment temperatures are analyzed. [ABSTRACT FROM AUTHOR]

The paper deals with Shape memory alloy (SMA) spring analysis and its possibility for usage as actuator for in-pipe machine. In the paper the inner structure of SMA is introduced. Further, the experimental analysis of SMA contractor and expander was done. From the experiments was found that SMA spring has several disadvantages like long time of cooling and high electric power consumption. Using SMA spring as actuator for in-pipe machine has been obtained average velocity of in-pipe machine roughly 2 mm/min. Advantage of SMA spring as actuator is its good expansibility. [ABSTRACT FROM AUTHOR]

This paper introduces an adapted high-speed high pressure torsion (HS-HPT) method of severe plastic deformation applied for obtaining shape memory alloy (SMA) active elements with revolution symmetry, able to develop axial displacement/force. Billets with circular crown forms were cut from Fe-28Mn-6Si-5Cr (mass%) SMA ingots and, by means of HS-HPT technology, were directly turned into modules, with truncated cone shell configurations. This process was performed, during time intervals of seconds, under the effect of high pressure (up to 1 GPa) cumulated with high rotation speed (hundreds of rotations per minute) applied on the active surfaces of sintered-carbide anvils, specially designed for this purpose. Due to pressure and friction, generated by rotation, the entire sample volume is heated and simultaneously deformed to final shape. During the process, microstructure fragmentation occurred enabling to obtain (ultra)fine grains and nanocrystalline areas, in spite of the heat developed by friction, which was removed by conduction at the contact surface between sample and anvils, before the occurrence of any recrystallization phenomena. When compressed between flat surfaces, the truncated cone modules developed a superelastic-like response, unique among Fe -Mn-Si base SMAs and, when heated in compressed state, they were able to develop either axial strokes or recovery forces by either free or constrained recovery shape memory effect (SME), respectively. By means of optical (OM) and scanning electron microscopy (SEM) marked structural changes caused by HT-HPT were revealed, along with fine and ultrafine crystalline grains. The presence of stress-induced ε-hexagonal close-packed ( hcp) martensite, together with nanocrystalline areas were confirmed by x-ray diffraction. [ABSTRACT FROM AUTHOR]

In this paper, we propose a method for taking into account uncertainties of a micro-pump system using Shape Memory Alloy (SMA), based on the perturbation method. The proposed method is used to determine the thermo-mechanical response of a system. Comparisons with the mean value reference solution, illustrate the efficiency of the proposed method. The results are discussed in order to investigate the influence of the most influential parameters of the thermomechanical SMA model. The simulation results are obtained by the proposed method for static analysis with uncertainties.The perturbation method results are compared with the mean value reference solution. The results are discussed in order to investigate the influence of the Young's modulus E, the two transformations strain magnitude ɛ t r a c T and ɛ t r a c T F A , the martensite start M s and austenite finish A f temperatures and the stress reorientation F ε on the static response of a micro-pump system. [ABSTRACT FROM AUTHOR]

Most relevant to predicting the behavior of shape-memory-alloy (SMA)-based actuator-sensor applications activated by Joule heating are the electro-mechanical characteristics of the material under consideration. For a comprehensive characterization, a single setup that is able to provide all relevant data and information is desirable. This work covers the design, implementation and validation of such a high-end test bench for the holistic characterization of SMA micro-wires. In addition, the setup provides the possibility of application simulation experiments. Key elements of the design are the clamping mechanism guided on air bearings, a linear direct drive, a high-resolution load cell, a high-precision constant current source and a stress-controlled in-line wire sample installation. All measurements take place inside an isolated, temperature-controlled chamber. With the presented setup, the electro-mechanical and thermal characteristics of SMA wire samples with diameters from 20 µm to 100 µm can be determined. Via hardware-in-the-loop (HiL) implementation, the outputs with different biasing mechanisms and additional end-stops can be simulated even at high ambient temperatures. The generated results facilitate the prediction of the exact characteristics of SMA-driven actuator-sensor systems in a variety of applications and lead to a better general understanding of the alloy's properties. All functionalities and features of the setup are presented by discussing the results of exemplary experiments. [ABSTRACT FROM AUTHOR]

In this paper, a novel actuator in the form of a Kagome truss composed of shape memory alloy (SMA) wires and common metallic wires is described. In the actuator, the SMA wires play dual roles as load supporters and actuating elements. The intersections between the SMA wires and between the SMA wires and the common metallic wires were joined by using shrinkable tubes, which induced the kinematically compatible buckling of the columns of SMA wires under compression, consequently enabling the large actuation displacement of up to 30% of the height with some sacrifice of the load capacity. An analytic solution was derived using the elementary mechanics of buckling and geometric relation of curved column, which gave fairly good estimation of the behavior of the Kagome actuator for the deformation and actuation stages, based on the behavior of a single SMA wire. The lightness and large actuation range of this actuator appear to be useful for practical applications. [ABSTRACT FROM AUTHOR]

The ever-changing nature of the power industry will require the implementation of hybrid energy systems. Integration of tightly coupled components in hybrids often involves the diversion of exhaust gas flow. An innovative smart material actuation technology is proposed to replace traditional electro-mechanical actuated valve mechanisms with lighter and less expensive actuators. A shape memory alloy (SMA) spring-actuated valve was designed for high-temperature service to demonstrate the promise of smart materials in control valve applications. With SMA springs only generating a maximum force of 3.2 N, an innovative valve design was necessary. To demonstrate the concept, a 3-inch Nominal Pipe Size valve was designed, and 3D printed using the stereolithography technique. Increasing the electrical current to actuate the SMA springs reduced actuation time. The maximum current of 10 A produced the lowest actuation time of 2.85 s, with an observed maximum stroke rate of more than 100 stroke completion %/s (considering actuation open/close as 100% stroke) at the midrange. The final assembly of the valve was estimated to provide a cost reduction of more than 30% and a weight reduction of more than 80% compared to the other available automatic valves in the present market. [ABSTRACT FROM AUTHOR]

The modern industrial and consumer applications in accordance with the concepts of Industry 4.0 and the Internet of Things are characterized by autonomy and self-sufficiency. This has led to an increase in the interest for the so-called smart materials, capable of combining the functionalities of sensors, actuators and, in some applications, control systems. An important group of smart materials are shape-memory alloys, among which nickel–titanium (NiTi) alloys are the most known. In this article, the influence of phase transformation on the mechanical properties of thin NiTi alloy wires was investigated. During the test, the influence of the heating currents on the displacement and the force generated by the thin NiTi wires were analyzed. The temperature of the wires during heating was measured by a thermographic camera. This study proved the maximum value of the wires' displacement was related to the value of the heating current. During the research, the dependence of the transformation dynamics on the value of the heating currents was also proved. In addition, the influence of the surface inhomogeneity of the thin NiTi alloy wires on the accuracy of the thermographic measurements was analyzed. For the experimental research described in this article, we used the NiTi alloy whose trade name is Flexinol, produced by DYNALLOY (Inc. 2801 McGaw Ave. Irvine, CA, USA). [ABSTRACT FROM AUTHOR]

One of the modern methods for enhancing the efficiency of photovoltaic (PV) systems is implementing a solar tracking mechanism in order to redirect PV modules toward the sun throughout the day. However, the use of solar trackers increases the system's electrical consumption, hindering its net generated energy. In this study, a novel self-tracking solar-driven PV system is proposed. The smart solar-driven thermomechanical actuator takes advantage of a solar heat collector (SHC) device, in the form of a parabolic trough solar concentrator (PTC), and smart shape memory alloy (SMA) to produce effective mechanical energy for solar tracking applications from sun rays. Furthermore, a thermal–optical analysis is presented to evaluate the performance of the solar concentrator for the simulated weather condition of Dammam City, Saudi Arabia. The numerical results of the thermal and optical analyses show the promising feasibility of the proposed system in which SMA springs with an activation temperature between 31.09 °C and 45.15 °C can be utilized for the self-tracking operations. The work presented adds to the body of knowledge an advanced SMA-based SHC device for solar-based self-actuation systems, which enables further expansions within modern and advanced solar thermal applications. [ABSTRACT FROM AUTHOR]

This paper deals w ith actuators based on shape memory alloys. The testing device has been developed for experimental verification of shape memory alloy actuator testing. Static characteristic shows the hysteresis of this material. Also dynamic properties have been explored through the step response characteristic. Application of the material as actuator in engineering system is shown. [ABSTRACT FROM AUTHOR]

Soft Robotics is an emerging field due to high degree of freedom, their soft and delicate interaction, almost no vibration during operations etc. are some among many reasons, why scientists and researchers got attracted towards this field. Nitinol is commonly used in soft robotics and easily available Shape Memory Alloy (SMA) actuator. In present investigation, the authors attempted to understand the characteristics and behaviour of Nitinol SMA Actuator wire with change in various parameters such as length, diameter, current, and temperature. Moreover, it is investigated, how resistance, power consumption, force developed, hysteresis, and displacement changing takes place with current passing through the wire and corresponding temperature developed. Various experiments are performed and based on the results and findings related to the selection of wires for specific requirement have been discussed and suggestions were made for the use of the SMA actuator efficiently and effectively. [ABSTRACT FROM AUTHOR]

This work aims at the experimental characterization and modeling validation of shape memory alloy (SMA) Negator springs. According to the classic engineering books on springs, a Negator spring is a spiral spring made of strip of metal wound on the flat with an inherent curvature such that, in repose, each coil wraps tightly on its inner neighbor. The main feature of a Negator springs is the nearly constant force displacement behavior in the unwinding of the strip. Moreover the stroke is very long, theoretically infinite, as it depends only on the length of the initial strip. A Negator spring made in SMA is built and experimentally tested to demonstrate the feasibility of this actuator. The shape memory Negator spring behavior can be modeled with an analytical procedure, which is in good agreement with the experimental test and can be used for design purposes. In both cases, the material is modeled as elastic in austenitic range, while an exponential continuum law is used to describe the martensitic behavior. The experimental results confirms the applicability of this kind of geometry to the shape memory alloy actuators, and the analytical model is confirmed to be a powerful design tool to dimension and predict the spring behavior both in martensitic and austenitic range. [ABSTRACT FROM AUTHOR]