Same-phase drive-type ultrasonic motors, using two degenerate bending vibration modes of a disk, are presented. The distinctive feature of the motor is in using the standing wave modes. The motor is not driven by two input signals with different phases, but by input signals with the same phase. Therefore, only one amplifier is sufficient to drive the motor. The experimental results have proved that the motor can yield stable operational characteristics at low speed and high torque.
In this paper the relationship between the pressing force
applied to a rotor and the rotation characteristic of an
ultrasonic motor driven by self-oscillation are discussed.
The motor used here is an in-phase drive-type ultrasonic
motor using two degenerate bending vibration modes of a disk.
The picking-up electrical signal caused by self-oscillation
is positively fed back into the piezoelectric ceramics for
driving through an operational amplifier and a step-up
transformer. The pressing force applied to a rotor was measured
using a force gauge coupled to the shaft of the ultrasonic
motor. As a result, it was confirmed that the selection of the
picking-up position for the feedback signal is important for a
stable starting and running of the disk-type ultrasonic motor
driven by self-oscillation.
Twenty years and more have passed since real research of ultrasonic motors was started and now their practical applications are performed in some engineering fields. Therefore, such a problem has happened now as to what kinds of breakthrough ultrasonic motors must be researched for the next generation. For this reason, we are challenging the breakthrough research of the ultrasonic motors. This paper deals with such breakthrough motors. In the first part, we deal with thin-form ultrasonic motors of high revolution speed for their use as HDD motors, applying lead-free piezoelectric single crystal of LiNbO3. The second part contains some gyro-moment motors, devised by us originally. The motors can be driven electromagnetically and, moreover, electrostatically in theory. Therefore the motors are suited to ones fabricated by MEMS technology and might be applied as a micro-fun motor for heat radiation in electronic apparatuses, a windmill motor in fuel cells, and so on.
In this paper we describe an ultrasonic motor using a flexural disk
vibrating in two degeneration modes driven by a same-phase input signal.
Its operating characteristics depend considerably on the pressing force
between the stator and the rotor. We report some experimental studies of
this effect. Measurements of the vibration mode showed that the change in
the rotational direction of the motor was caused by a shift in the vibration
axis of the mode synthesized from two degeneration modes. It is also shown
that the motor's operating characteristics can be adjusted via an electrical
element connected to the control terminal.
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