Ultrasonic linear motor using surface acoustic waves

The first success in the operation of an ultrasonic linear motor at HF band driving frequency using the Rayleigh wave is described. The substrate material is a 127.8/spl deg/ Y-cut LiNbO/sub 3/ wafer whose diameter is three inches. Four interdigital transducers (IDT´s) are arranged to excite x- and y-propagation waves in both directions. The dimensions of the IDT are 25 mm aperture size, 400 /spl mu/m pitch, 100 /spl mu/m strip width, and 10 pairs. The operation area is about 25 mm square, The driving frequency is about 9.6 MHz in the x direction and about 9.1 MHz in the y direction. The most important point of the success is the shape of the contact surface and slider materials. For the contact materials, small balls about 1 mm in diameter are introduced to obtain sufficient contact pressure around 100 MPa. The use of ruby balls, steel balls, and tungsten carbide balls is investigated. Each slider has three balls to enable stable contact at three points. The maximum transfer speed is about 20 cm/s. The transfer speed is controllable by changing the driving voltage.