Shape Memory Alloy Actuated Vertical Deploy Air Dam: Part 1 — Performance Requirements and Design

Airflow over/under/around a vehicle can affect many important aspects of vehicle performance including vehicle drag (and through this vehicle fuel economy) and cooling/heat exchange for the vehicle powertrain and A/C systems. The vast majority of known devices in current use to control airflow over/under/around the vehicle are of fixed geometry, location, orientation, and stiffness. The project whose performance requirements, design, and build phases are described in this paper was successful in developing an SMA actuator based approach to the on-demand reversible deployment of an air dam through vertical translation. Beyond feasibility, the initial bench top working models demonstrated an active materials based approach which would add little weight to the existing stationary system, and could potentially perform well in the harsh under vehicle environment due to a lack of exposed bearings and pivots. This demonstration showed that actuation speed, force, and cyclic stability all could meet the application requirements. The solution, a dual point balanced actuation approach based on shape memory alloy wires, uses straight linear actuation to produce a reversible height change of 50 mm. Key technical issues with regard to design remaining to be resolved given the harsh under vehicle environment are in most part related to improved system robustness, a prime example being mechanism sealing.

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SMA Actuated Vertical Blade Louver System: Part 1 — Performance Requirements and Design

Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation and Control of Adaptive Systems; Integrated System Design and Implementation ◽

10.1115/smasis2013-3001 ◽

2013 ◽

Author(s):

Alan L. Browne ◽

Nancy L. Johnson ◽

Jeffrey Brown

Keyword(s):

Aerodynamic Drag ◽

Performance Testing ◽

Vehicle Performance ◽

Active Devices ◽

On Demand ◽

Performance Requirements ◽

Sma Actuator ◽

Application Requirements ◽

Opening And Closing ◽

Demand Control

Airflow over/under/around a vehicle can affect many important aspects of vehicle performance including vehicle drag (and through this vehicle fuel economy), vehicle lift and downforce, and cooling/heat exchange for the vehicle powertrain and A/C systems. While active devices are present on all aircraft, the majority of known airflow control devices in current use in ground transportation are of fixed geometry, location, orientation, and stiffness. The project, conducted during the 2004–2006 timeframe, whose performance requirements, design, and bench-top prototype build phases, are described in this paper was successful in developing an SMA actuator based approach for opening and closing a vertically-oriented-blade louver system to be used for on-demand control of the airflow into the engine compartment, i.e. for on-demand control of both cooling airflow as well as aerodynamic drag. Beyond feasibility, the initial full scale bench top working models demonstrated an active materials based approach which would have decreased weight and a smaller packaging envelop than a comparable motor driven unit. This demonstration showed that actuation speed, force, and cyclic stability all could meet the application requirements. The specific design that was selected, a set of parallel vertically oriented blades each linked through a gear to a common rack that is translated by a linear SMA actuator, uses straight linear actuation to produce a reversible synchronous 90 degree rotation of the blades, i.e. a full opening and closing capability for the louver system. Key technical issues that remained to be demonstrated and resolved through design modifications if necessary in Part 2 — on-vehicle performance testing — of this study were related in most part to robustness in the harsh vehicle front-end environment, a prime example being mechanism stalling due to ice or mud buildup.

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Microstructural Evolution and Metastability in Active Materials

MRS Proceedings ◽

10.1557/proc-529-3 ◽

1998 ◽

Vol 529 ◽

Author(s):

David Kinderlehrer

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Microstructural Evolution ◽

Active Materials ◽

Length Scales ◽

Macroscopic Level ◽

Evolution Of Microstructure ◽

Metastable Systems

AbstractMetastable systems pose significant problems in both analysis and simulation. We discuss here the evolution of microstructure in a shape-memory alloy where energetic contributions from disparate scales play determining roles. This is a challenge for modelling since the finest length scales cannot be ‘seen’ at macroscopic level. We then provide a mechanism for kinetics that gives a different notion metastability.

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Simulation and Control Design for Shape Memory Alloy Torque Tubes

ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Volume 2 ◽

10.1115/smasis2011-5132 ◽

2011 ◽

Cited By ~ 3

Author(s):

David H. Friedman ◽

Stefan Bieniawski ◽

Darren Hartl

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

High Performance ◽

Linear Quadratic Regulator ◽

Complete Sequence ◽

Shear Loading ◽

Control Synthesis ◽

Linear Quadratic ◽

Vehicle Performance ◽

Compact Size

Shape Memory Alloy (SMA) driven actuation devices offer the potential for dramatic improvements in flight vehicle performance. Such actuators are ideally suited for the light-weight, low-bandwidth, compact size requirements associated with small changes in the vehicle geometry to enhance performance. Over the last 10+ years SMA-based actuation concepts have been considered for use on commercial aircraft, military aircraft, rotorcraft, and spacecraft. Many of these actuation concepts are driven by twisting SMA tubes which are under variable shear loading. This work extends previous quasi-static modeling work to provide a time-domain coupled thermo-mechanical model for SMA torque tubes. The model includes states associated with the material and states associated with peripheral dynamic systems, such as the heater. Approaches for obtaining the key parameters required by the model directly from experimental data are then described. Steps for developing controllers using these models are then reviewed including linearization and linear quadratic regulator (LQR) based control synthesis. The controller is implemented and tested in closed-loop position tracking experiments. These are completed in a lab setting and the results indicate a robust (in terms of gain and phase margin) and high-performance (in terms of settling time) tracking controller. The complete sequence described in this work illustrates the potential of model based optimal control applied to Shape Memory Alloy torque tubes.

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Parametric Analysis of a Compliant Hinge Mechanism for a Shape Memory Alloy Actuated Arm

Volume 2: Modeling, Simulation and Control of Adaptive Systems; Integrated System Design and Implementation; Structural Health Monitoring ◽

10.1115/smasis2017-3738 ◽

2017 ◽

Author(s):

Cody Wright ◽

Onur Bilgen

Keyword(s):

Shape Memory Alloy ◽

Shape Memory ◽

Elbow Joint ◽

Parametric Analysis ◽

Complex Geometries ◽

Biceps Muscle ◽

Dead Load ◽

Revolute Joints ◽

Material Solution ◽

Application Requirements

A compliant hinge is proposed to replace conventional revolute joints for a shape memory alloy actuated arm-like mechanism. The arm-like mechanism is designed to replicate the articulation of the elbow joint, linking the humerus and radius, while being able to lift a dead load using a shape memory alloy wire as the biceps muscle. A parametric analysis on hinge geometry and Young’s modulus is performed to determine if a feasible geometric and material solution exists based on the application requirements. The results indicate optimum solutions are logarithmically correlated between modulus of elasticity and width-to-thickness ratio. Overlaying the results of the parametric study onto an Ashby chart indicates that large hinge widths are necessary. These results indicate more complex geometries are needed for arm-like manipulator applications.

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