A surface acoustic wave (SAW) motor has already shown its superior potential. However, its efficiency from the electrical input to the mechanical output is still low. To improve its efficiency, an energy circulation driving method has been proposed and demonstrated. It has been found that the Rayleigh wave beneath the slider was scattered, so that the phase of the wave shifted; the phase shift decreased the efficiency of the motor. Thus, we need to know the characteristics of the phase shift to design a SAW motor with a high efficiency. From several experimental results, it has been found that the phase shift is related to the projection parameters of the slider and the preload conditions. The relationship between the slider projection contact, the friction phenomenon, and the phase shift was investigated by numerical simulation using the finite element method. Two-dimensional finite element method analysis in a time domain was carried out to simulate the wave propagation from driving points through a preloaded silicon slider. Contact and friction simulation was applied to the boundary condition between the stator and the slider projections.
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