SMA Wire Actuators Research Articles

A novel dust mitigation technology solution of a self-cleaning method for a PV module capable of harnessing reject heat using shape memory alloy

Most large-scale solar photovoltaic (PV) systems are installed in remote and desert areas, where large land areas and sunlight are available throughout the year. However, major environmental degradation factors exist in the form of soiling and dust accumulation, primarily when operating PV systems in desert lands. In this study, an innovative method for dust mitigation of a PV panel surface is introduced using an SMA wire actuator. It utilizes unwanted heat energy at the back surface of a PV panel and converts it into effective mechanical energy using a unique thermo-mechanical property in SMA materials. Results of the indoor test, using a sun-simulator instrument, prove the effectiveness of harnessing the reject heat at the back surface of a PV panel toward the activation of an SMA-based PV cleaning system. Experimental results demonstrated the successful reach of the SMA activation temperature of about 60 OC, for an applied solar irradiance power of 1200 W/m2, within a test duration of 40 min. This allowed generating a desirable mechanical displacement based on the harnessed rejected heat for the operation of the cleaning system. The overall performance of the fabricated system was analyzed and evaluated to highlight the achieved cleaning process and its effectiveness.

Nonlinear Analysis of a Flexible Beam Actuated by a Couple of Active SMA Wire Actuators

There are two different ways of using SMA wires as actuators for shape control of flexible structures; which can be either embedded within the composite laminate or externally attached to the structure. Since the actuator can be placed at different offset distances from the beam, external actuators produce more bending moment and, consequently, considerable shape changes with the same magnitude of the actuation force comparing to the embedded type. Such a configuration also provides fast convection which is very important in shape control applications that require a high-frequency response of SMA actuators. Although combination and modeling of externally-attached SMA actuator wires and strips have been considered by many researchers, these studies have some weaknesses neglecting them yields a number of errors between theoretical and experimental results. In this work, the aforementioned limitations of attaching actuators to the smart structures have been removed and a flexible beam actuated by two active SMA actuators is nonlinearly modeled. The Brinson constitutive equations and thermoelectric equations for SMA materials are coupled with the nonlinear beam behavior and the coupled system of equations is numerically solved for some particular practical cases. The analysis method done in this paper can be easily extended to the complicated smart structure with externally-attached SMA wires.

Fabrication and static characterization of carbon-fiber-reinforced polymers with embeddedNiTi shape memory wire actuators

In this work, unidirectional carbon-fiber-reinforced polymers (CFRP) with embedded NiTishape memory alloy (SMA) wire actuators were manufactured using a universal testingmachine equipped with a thermally controlled chamber. Beam specimens containingcold-worked, annealed and trained NiTi SMA wires distributed along their neutral planewere fabricated. Several tests in a three-point bending mode at different constanttemperatures were performed. To verify thermal buckling effects, electrical activation ofthe specimens was realized in a cantilevered beam mode and the influence ofthe SMA wire actuators on the tip deflection of the composite is demonstrated.

A Study on Anthropomorphic Robot Hand Simulation Driven by SMA Wire Using Segment Control

In recent years, as the robot technology is developed, the researches on the artificial muscle actuator that enables robot to move dexterously like biological organ become active. Actuators are one of the key technologies underpinning robotics. Particularly breakthroughs of power-to-weight ratio or energy-density in actuator technology have significant impacts upon the design and the control of robotic systems. The widely used materials for artificial muscle are the shape memory alloy and electro-active polymer. These actuators have the higher energy density than the electromechanical actuators such as the electric motor. However, there are some drawbacks because these actuators have the hysteretic dynamic characteristics. In this paper, the segment control for reducing the hysteresis of SMA is proposed and the simulation of an anthropomorphic robotic hand is performed using ADAMS. A new approach to design and control of SMA actuators is presented. SMA wire is divided into many segments and their thermal states are controlled individually in a binary manner(ON/OFF). The basic experiment for evaluating the dynamic characteristics of SMA wire actuator is performed.

MODELING AND CONTROL OF SHAPE MEMORY ACTUATORS

This paper addresses the issue of modeling and control of shape memory actuators exemplified here by a SMA-wire actuator. After some preliminary considerations and some briefly reviewed details related to the constitutive modeling of shape memory materials, this article focuses on the Preisach hysteresis modeling in terms of presentation and comparative discussion of different modeling approaches in accordance to different Preisach measures (or weighting functions in the Preisach plane), and considers the position control using conventional feedback strategies. The effectiveness of the considered modeling approaches and the closed-loop performance achieved by using conventional controllers are demonstrated by simulations and in part by experiments.

Behaviors of Shape Memory Alloy Wire Embedded Smart Composite Skins and Actuators

The shape changes by bending and twisting of a SMA/composite panel with embedded SMA wire actuators controlled by both electric resistive heating and passive elastic tailoring are investigated to realize the morphing wing of unmanned aerial vehicles. Three-dimensional finite element formulations are derived and used to analyze the behaviors of the SMA/composite smart structures. The numerical results show that the shapes of the SMA/composite panels can be controlled by judicious choices of control temperatures, SMA angles, and elastic tailoring. To validate the analytical results, two SMA-embedded curved panels are fabricated and then, their changes in shape are measured by a laser optical sensor when SMA is activated by electrically resistive heating. Both results show excellent correlation.

Adaptive composites incorporating shape memory alloy wires Part I Probing the internal stress and temperature distributions with a laser Raman sensor

Hybrid composite laminates consisting of an epoxy resin reinforced by aramid fibres and incorporating SMA wire actuators have been produced. The residual thermal stresses of the composites were determined with the technique of laser Raman spectroscopy and the generated compressive loads during SMA activation were quantified. The results obtained indicate that the SMA wires can be effectively used as actuating elements whereas the aramid fibres can be exploited as independent thermal and mechanical sensors.

The shape control of a composite beam with embedded shape memory alloy wire actuators

In this study, the results of experimental and analytical study on shape control of a composite beam with embedded shape memory alloy wire actuators are presented. The effects of the reactive moment of the SMA wire actuators on the shape control test are observed in detail. In shape control of a flexible composite structure, the reactive moment by SMA wire actuators can alter the deformed shape of composite beams which are subjected to external and thermal loads. The results obtained from the shape control test confirm that the deflected shape of a composite beam with embedded SMA wire actuators can be controlled by electrical resistance heating. An analytical model describing the snapthrough of composite beams is also presented.