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Design of Shape Memory Alloy Actuator with High Strain and Variable Structure Control

12/1999;
Source: CiteSeer

ABSTRACT A novel Shape Memory Alloy (SMA) actuator consisting of a number of thin NiTi fibers woven in a counter rotating helical pattern around supporting disks is first described. This structure can be viewed as a parallel mechanism used to accomplish a highly efficient transformation between force and displacement. The actuator overcomes the main mechanical drawback of shape memory alloys, that being limited strain. Two variable structure controllers are applied to a pair of antagonist actuators. The first involves a switching control input creating a sliding mode in conjunction with a linear control activated within a boundary layer in the vicinity of the set point. The second involves a multi-stage switching control that simplifies amplifier construction. Experimental performance results in the time domain are discussed. 1 Introduction With the continued miniaturization of robotic systems comes the need for powerful, compact, lightweight actuators. Conventional techniques such as electri...

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    • "shown that open loop control is not suitable for robotic applications [1] [2]. Only a limited number of approches for controlling SMA actuator can be consider positively when taking into account integration constraints for microsystems (i.e number of sensors and controller hardware have to be minimized) [2]. "
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    12/2007: pages 490-499;
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    ABSTRACT: This work describes the conceptual design, the modelling, the optimization, the detail design and the virtual testing of a shape memory actuator purposely conceived to maximize torque and angular stroke while limiting overall size and electric consumption. The chosen design, achieved by means of a Quality Function Deployment approach, features a fully modular concept in which an arbitrary number of identical modules are assembled to produce the desired angular stroke and output torque. The basic module contains shape memory springs that actuate the device and also a conventional spring that reduces the torque ripple. Following the concept generation stage, a thermo-electromechanical model is developed and a numerical optimization performed, aimed at minimizing the electrical consumption of the actuator. Finally, the device is designed in detail and the actuator is tested virtually. Thanks to the proposed modular construction and the use of a conventional balancing spring, the device shows better performances than known rotary shape memory actuators in terms of rotation, torque and customization.
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    Smart Materials and Structures 12/1998; 8(2):197. DOI:10.1088/0964-1726/8/2/004 · 2.45 Impact Factor
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