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Proceedings Paper

Piezo-drive circuits for amplitude-modulated locomoton for miniature wireless robots
Author(s): Sylvain M. Martel; Ian Warwick Hunter
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Paper Abstract

Piezo-actuators due to their relatively high resonant frequencies and small deflections are ideally suited as accurate displacement transducers. As such, they have been used to implement the legs of the miniature wireless NanoWalker robot where step sizes in the order of a few tenths of nanometers are required for final positioning within the range of an embedded instrument designed to operate at the atomic scale. The relatively high capacitance combined with the high-drive voltage requirement of the actuators, impose constraints on the miniaturization of the electronics. The amplitude modulation scheme requires one amplifier per quadrant electrode on the piezo-legs. Although power amplifiers are suited to drive large capacitive loads with large signal amplitudes without stability problems, the quiescent current of the amplifiers requires several DC/DC converters of significant size. During locomotion, the sudden current increase occurring when high slew rate signals are used during the charging/discharging cycle of the capacitive loads at each walking step, causes the power rail voltage to drop, yielding a reduction in the amplitude of the deflections of the piezo-legs. To minimize the number of DC/DC converters, the slew rate requirement of the drive signal is reduced by an increase of the angular acceleration of the leg created by an initial static friction force with the walking surface. It is then suggested that further miniaturization of the embedded electronics can be achieved by adjusting the kinematic behavior of the piezo-legs with an appropriate mechanical design and the right friction coefficient through careful materials selection.

Paper Details

Date Published: 8 October 2001
PDF: 11 pages
Proc. SPIE 4568, Microrobotics and Microassembly III, (8 October 2001); doi: 10.1117/12.444127
Show Author Affiliations
Sylvain M. Martel, MIT BioInstrumentation Lab. (United States)
Ian Warwick Hunter, MIT BioInstrumentation Lab. (United States)

Published in SPIE Proceedings Vol. 4568:
Microrobotics and Microassembly III
Bradley J. Nelson; Jean-Marc Breguet, Editor(s)

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