4,512 research outputs found

    Application of Laguerre based adaptive predictive control to Shape Memory Alloy (SMA) actuators

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    This paper discusses the use of an existing adaptive predictive controller to control some Shape Memory Alloy (SMA) linear actuators. The model consists in a truncated linear combination of Laguerre filters identified online. The controller stability is studied in details. It is proven that the tracking error is asymptotically stable under some conditions on the modelling error. Moreover, the tracking error converge toward zero for step references, even if the identified model is inaccurate. Experimentalcresults obtained on two different kind of actuator validate the proposed control. They also show that it is robust with regard to input constraints.ANR MAFESM

    Development and Wind Tunnel Evaluation of a SMA Based Trim Tab Actuator for a Civil Aircraft

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    This paper presents about the development and wind tunnel evaluation of an SMA based smart trim tab for a typical 2 seater civil aircraft. SMA actuator was housed in the port side of the elevator for actuating the trim tab. Wind tunnel tests were conducted on a full scale Horizontal Tail model with Elevator and Trim Tab at free stream speeds of 25, 35 & 45 m/sec and also for a number of deflections of the elevator (30° up, 0° neutral & 25° down) and trim-tab 11° & 21° up and 15° & 31° down). To measure the hinge moment experienced by the trim-tab at various test conditions, two miniaturized balances were designed and fabricated. Gain scheduled proportional integral controller was developed to control the SMA actuated smart trim tab. It was confirmed during the tests that the trim-tab could be controlled at the desired position against the aerodynamic loads acting on it for the various test conditions

    Shape Memory Alloy Actuator Design: CASMART Collaborative Best Practices

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    Upon examination of shape memory alloy (SMA) actuation designs, there are many considerations and methodologies that are common to them all. A goal of CASMART's design working group is to compile the collective experiences of CASMART's member organizations into a single medium that engineers can then use to make the best decisions regarding SMA system design. In this paper, a review of recent work toward this goal is presented, spanning a wide range of design aspects including evaluation, properties, testing, modeling, alloy selection, fabrication, actuator processing, design optimization, controls, and system integration. We have documented each aspect, based on our collective experiences, so that the design engineer may access the tools and information needed to successfully design and develop SMA systems. Through comparison of several case studies, it is shown that there is not an obvious single, linear route a designer can adopt to navigate the path of concept to product. SMA engineering aspects will have different priorities and emphasis for different applications

    Low spring index, large displacement Shape Memory Alloy (SMA) coil actuators for use in macro- and micro-systems

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    Shape memory alloys (SMA) offer unique shape changing characteristics that can be exploited to produce low­ mass, low-bulk, large-stroke actuators. We are investigating the use of low spring index (defined as the ratio of coil diameter to wire diameter) SMA coils for use as actuators in morphing aerospace systems. Specifically, we describe the development and characterization of minimum achievable spring index coiled actuators made from 0.3048 mm (0.012") diameter shape memory alloy (SMA) wire for integration in textile architectures for future compression space suit applications. Production and shape setting of the coiled actuators, as well as experimental test methods, are described. Force, length and voltage relationships for multiple coil actuators are reported and discussed. The actuators exhibit a highly linear (R[superscript 2] < 0.99) relationship between isometric blocking force and coil displacement, which is consistent with current SMA coil models; and SMA coil actuators demonstrate the ability to produce significant linear forces (i.e., greater than 8 N per coil) at strains up to 3x their initial (i.e., fully coiled) length. Discussions of both the potential use of these actuators in future compression space suit designs, and the broader viability of these actuators in both macro- and micro-systems, are presented.United States. National Aeronautics and Space Administration. Office of the Chief Technologist (Space Technology Research Fellowship Grant NNX11AM62H)MIT-Portugal Progra

    Feasibility of a 30-meter space based laser transmitter

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    A study was made of the application of large expandable mirror structures in future space missions to establish the feasibility and define the potential of high power laser systems for such applications as propulsion and power transmission. Application of these concepts requires a 30-meter diameter, diffraction limited mirror for transmission of the laser energy. Three concepts for the transmitter are presented. These concepts include consideration of continuous as well as segmented mirror surfaces and the major stow-deployment categories of inflatable, variable geometry and assembled-in-space structures. The mirror surface for each concept would be actively monitored and controlled to maintain diffraction limited performance at 10.6 microns during operation. The proposed mirror configurations are based on existing aerospace state-of-the-art technology. The assembled-in-space concept appears to be the most feasible, at this time

    Low power consumption mini rotary actuator with SMA wires

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    Shape memory alloys (SMAs) are smart materials widely used as actuators for their high power to weight ratio despite their well-known low energy efficiency and limited mechanical bandwidth. For robotic applications, SMAs exhibit limitations due to high power consumption and limited stroke, varying from 4% to 7% of the total length. Hysteresis, during the contraction and extension cycle, requires a complex control algorithm. On the positive side, the small size and low weight are eminently suited for the design of mini actuators for robotic platforms. This paper describes the design and construction of a light weight and low power consuming mini rotary actuator with on-board contact-less position and force sensors. The design is specifically intended to reduce (i) energy consumption, (ii) dimensions of the sensory system, and (iii) provide a simple control without any need for SMA characterisation. The torque produced is controlled by on-board force sensors. Experiments were performed to investigate the energy consumption and performance (step and sinusoidal angle profiles with a frequency varying from 0.5 to 10 Hz and maximal amplitude of 15?). We describe a transient capacitor effect related to the SMA wires during the sinusoidal profile when the active SMA wire is powered and the antagonist one switched-off, resulting in a transient current time varying from 300 to 400 ms

    A cooling system for s.m.a. (shape memory alloy)based on the use of peltier cells

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    The aim of this thesis has been the study and the implementation of an innovative cooling system for S.M.A. (Shape Memory Alloy) material by using a Peltier cell. This system has demonstrated a consistent cooling time reduction during the application and so that the solution adopted has confirmed that it can be used for a better operability of the S.M.A. material during the cooling phase. After an accurate selection of possible cooling system to be adopted on these materials the better choice in terms of efficiency and energy consumption reduction has converged on Peltier cell design development. In this context for our research three investigation have been conducted. The first one has concerned an analytic investigation in order to understand the phenomenology and the terms involved during the heat exchange. After this study a numerical investigation through a Finite Element approach by commercial software has been carried out. Also an experimental investigation has been conducted, at the CIRA Smart Structure Laboratory, in order to verify the results obtained by the numerical prediction. The set-up with the Peltier cell used as heater and cooler of the S.M.A. has confirmed the soundness of the solution adopted. Finally, a correlation between numerical and experimental results have been presented demonstrating the validity of the obtained results through the developed investigations. This system, composed of Peltier cell has confirmed also an energy consumption reduction because the cell has been used for heating and cooling phase without additional system as resistive system (Joule effect). This project shall be also industrial involvement in a new cost cut down point of vie

    Development of an Adaptive Flap/Flaperon Flight Control System with Shape Memory Alloy Actuation

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    This thesis discusses the design, manufacturing and testing of a new kind of adaptive airfoil using Shape Memory Alloy (SMA) actuation. An antagonistic arrangement of SMA wires was used in a Post-Buckled Precompressed (PBP) kind of actuator that was employed in an adaptive flap system. The thesis opens with a short survey on the history of the PBP mechanism and a literature research on different flap systems actuated by adaptive materials. The conceptual design of the SMAPBP actuator and its evolution to the actuator employed in an adaptive aerostructure is discussed in the first chapters. Experiments showed that the SMAPBP actuator could obtain tip rotations up to 65°, which nearly quadrupled the levels achieved by piezoelectric PBP actuators. In the following, former developed theory for piezoelectric PBP actuators was modified to account for the trapezoidal shape of the SMAPBP actuator. The developed theory was then compared to experimental results. A FEM model was also developed and evaluated to prove the PBP concept for this actuator numerically. In the second section of the thesis the author gives a detailed explanation of the design concept and the manufacturing of the airfoil. A NACA0012 airfoil with a chord length of 150mm and a width of 100mm was used to prove the concept of the adaptive flap system. The thesis continues with a description of the test setup, the CFD model assumptions and the results of wind tunnel tests. The developed adaptive airfoil proved its capabilities during the numerical and experimental tests and showed that the employment and actuation of the SMAPBP actuator could more than doubled the lift coefficient of the airfoil. The architecture and employment of a closed loop position feedback system to overcome the nonlinear behavior of the SMA material and the PBP mechanism is also discussed. The thesis closes with an overview over the adaptive airfoil with SMAPBP actuator and gives recommendations for future work in this field

    Thermo-Mechanical System Identification of a Shape Memory Alloy Actuated Mechanism

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    Shape memory alloy (SMA) actuators paired in an antagonistic arrangement can be used to produce mechanisms that replicate human biomechanics. To investigate this proposal, the biomechanical articulation of the elbow by means of the biceps brachii muscle is compared with that of a SMA actuated arm. This is accomplished by parametric analysis of a crank-slider kinematic mechanism actuated, first, with an experimentally characterized SMA wire and then an idealized musculotendon actuator based on actuation properties of muscles published in the literature. Next, equations of motion for the system dynamics of the SMA actuated mechanism are derived and phase portrait analysis is conducted varying system parameters around different operating points. The eigenvalues of the differential equation are examined around equilibrium points and a stiffness ratio metric is proposed to characterize dynamic stability based on system parameters. Next, a heat transfer model is proposed and energy analysis is conducted on each stage of phase transformation for the SMA wire. The unknown parameters in the heat transfer model are theoretically derived and an experimental system identification is conducted. A proof of concept antagonistic SMA actuated mechanism is designed and kinematic analysis is conducted on an experimental prototype
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