Beam shape control using shape memory alloys
Kelly, Brian L.
Agrawal, Brij N.
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This thesis presents the design and experimental results of active position control of a shape memory alloy (SMA) wire and a SMA wire actuated composite beam. The wire is a single SMA Nickel Titanium wire mounted on a single wire test stand. The composite beam is aluminum honeycomb with SMA wires embedded in one of its face sheets for active shape control. The potential applications of this experiment include thermo-distortion compensation for precision space structures, stern shape control for submarines, and flap shape control for aeronautical applications. SMA wires are chosen as actuating elements due to their high recovery stress (> 700 MPa) and its tolerance to high strain (up to 8%). SMA wires are inherently nonlinear, which poses a challenge for control design. The experimental setup consists of the single wire test stand and the composite beam with embedded SMA wires, a HP programmable power supply, a Linear Variable Differential Transformer (LVDT), an intrared laser range sensor, and a dSpace system with a Texas Instrument C-30 DSP for data acquisition and real-time control. A Position and Derivative (PD) control with feed forward action was designed and implemented, and a control accuracy of 0.1 mm was achieved. A non-linear control was added which gives a control accuracy of 0.05 mm with a much faster response.
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