NDLI: Experimental Investigation of High-Speed/High-Voltage SMA Actuation

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Motzki, Paul Gorges, Tom Würtz, Thomas Seelecke, Stefan
Copyright Year	2017
Abstract	The thermal shape memory effect describes the ability of a deformed material to return to its original shape when heated. This effect is found in shape memory alloys (SMAs) such as nickel-titanium (NiTi). SMA actuator wire is known for its high energy density and allows for the construction of compact systems. An additional advantage is the so-called “self-sensing” effect, which can be used for sensor tasks within an actuator-sensor-system. In most applications, a current is used to heat the SMA wires through joule heating. Usually a current between zero and four ampere is recommended by the SMA wire manufacturers depending on the wire diameter. Therefore, supply voltage is adjusted to the SMA wire’s electrical resistance to reach the recommended current. The focus of this work is to use supply voltages of magnitudes higher than the recommended supply voltages on SMA actuator wires. This actuation method has the advantage of being able to use industry standard voltage supplies for SMA actuators. Additionally, depending on the application, faster actuation and higher strokes can be achieved. The high voltage results in a high current in the SMA wire. To prevent the wire from being destroyed by the high current, short pulses in the micro- and millisecond range are used. As part of the presented work, a test setup has been constructed to examine the effects of the crucial parameters such as supply voltage amplitude, pulse duration, wire diameter and wire pre-tension. The monitored parameters in this setup are the wire displacement, wire current and force generated by the SMA wire. All sensors in this setup and their timing is validated through several experiments. Additionally, a highspeed optical camera system is used to record qualitative videos of the SMA wire’s behavior under there extreme conditions. This optical feedback is necessary to fully understand and interpret the measured force and displacement signals.
Sponsorship	Aerospace Division
File Format	PDF
ISBN	9780791858257
DOI	10.1115/SMASIS2017-3787
Volume Number	Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies
Conference Proceedings	ASME 2017 Conference on Smart Materials, Adaptive Structures and Intelligent Systems
Language	English
Publisher Date	2017-09-18
Publisher Place	Snowbird, Utah, USA
Access Restriction	Subscribed
Subject Keyword	Actuators Construction Shape memory alloys Electrical resistance Wire Density Displacement Amperes Shape memory effects Heat Joules Feedback Heating Nickel titanium alloys Engineering standards Titanium Nickel Tension Sensors Shapes Signals
Content Type	Text
Resource Type	Article

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