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

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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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Available from: Vincent Hayward, Dec 14, 2015
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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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