Friction drive of an SAW motor. Part II: Analyses

The mechanics of the friction drive of a surface acoustic wave motor were investigated by means of contact mechanics theory. As a means to control the contact condition, the motor´s slider had projections on its frictional surface. Assuming the projection was a rigid circular punch and the slider body was an elastic half-space allowed application of contact mechanics formulae to the analyses of the friction drive. Because the projection contacted the Rayleigh wave vibration, the projection´s responses were considered dynamic; thus, the dynamics were also analyzed in the same framework of contact mechanics formulae. Moreover, the analyses were applied to measurements of the projection´s displacement to examine the detailed mechanics during the friction drive. We calculated the contact/frictional forces based on the measurement and indicated the necessity of further investigation of the surface acoustic wave motor´s friction drive, because the usual friction law was unable to explain the measurement.