Production of a quasi-traveling wave in a silicon rectangular plate using single phase drive

Abstract

A method is proposed in order to produce a quasi-traveling wave on a rectangular plate with a single phase drive. The method is tested using chemically etched silicon plates. Ultrasonic motors often use traveling waves. For a traveling wave propagating in an elastic object, the particles on the surface move elliptically. Therefore, if a movable object is pressed against the surface of an object subject to a traveling wave then the frictional forces between them can induce a movement. Usually the traveling wave is obtained in a circular plate (or ring) using the combination of two standing waves. These standing waves correspond to a degenerate vibration mode excited by two series of piezoelectric elements. Each series is driven by an electrical power source phase shifted to each other. We present a model that shows the possibility to obtain a quasi-traveling wave in a rectangular plate using the superposition of two plate modes (for example modes 2.1 and 1.3). The quasi-traveling wave is obtained along a curve for which the amplitude of the wave is almost constant and the phase is almost proportional to the curvilinear coordinate of this curve. If the geometry is chosen in order to get the same frequency for both resonances (f/sub 21/=f/sub 31/), the quasi-traveling wave can be obtained by the excitation of two phases. If the geometry is such that the frequencies f/sub 21/and f/sub 31/ are slightly different, it is possible to excite both modes with a frequency f, selected between f/sub 21/ and f/sub 13/. In some cases, the phase shift between the excitation and the mode motion is such that the quasi-travelling wave is produced. Therefore we obtain a quasi-traveling wave using a single phase drive. Obviously in this case the amplitude is reduced by a factor of approximately /spl radic/2. The experiment is performed on a chemically etched rectangular silicon plate. Therefore we checked the possibility of producing a linear motion with a stator manufactured on silicon using microelectronics technology. We conclude that it is experimentally possible to obtain a quasi-traveling wave on a silicon plate using only a single phase drive and the experimental behavior is close to that of the model. >