Acoustic Waveguides for Actuators

概要

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Using a $3\times 4\times 5$ mm torsional microtransducer attached to a 30-cm long, 0.3-mm diameter flexible stainless steel wire, torsional vibration and coupled torsional-flexural vibration is transmitted to a remotely-placed rotor. The torsional microtransducer uses flat, thickness-poled lead zirconate titanate (PZT) elements attached to the surface of a square-sided prism with a tapered horn and tip; the elements twist the structure and generate torsional vibration amplified by the horn and tip at 150–260 kHz. Swaged to the wire—the ‘acoustic waveguide’—torsional vibration is transmitted into the wire, and flexural vibration is developed in the wire due to strong torsional-flexural coupling, demonstrated by measurement of the vibration velocity. Standing wave vibration was generated (standing wave ratio, SWR$\approx$7.5) in the waveguide with nothing on the waveguide tip, but upon using a rotor, traveling wave vibration transmitted energy to the rotor (SWR$\approx$4), which acted essentially as a loss; by placing a damping material on the tip instead of a rotor, very similar traveling wave motion was obtained (SWR$\approx$1.5). The few torsional resonances of the transducer were found to be greatly increased in number by the waveguide, and rotors, with a contact radius of 300 μm, were found to rotate for most of these resonances in either direction at up to 11,500 rpm and 3.5 μN-m.
2004-05-15