Chiharu Kusakabe

Same phase drive-type ultrasonic motors using two degenerate bending vibration modes of a disk

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.<<ETX>>

High-speed actuation of a piezoelectric actuator by pulse driving and stopping of its residual mechanical vibration

The driving method for high-speed actuation and prevention of residual vibration of a piezoelectric actuator is described. The driving voltage is composed of a pulse voltage and a step voltage. As a result, the risetime of the piezoelectric actuator can be reduced to approximately 1/4 of its mechanical response period by setting the pulse width, and the residual vibration can be prevented by adjusting the step voltage. The high-speed stopping of a piezoelectric actuator driven by AC power at its resonance is discussed.<<ETX>>

Rotor Displacement of the Ultrasonic Motor Having an Angular Displacement Self-Correction Function

This paper deals with the experimental investigation for confirmation of rotor displacement of the ultrasonic stepping motor having an angular displacement self-correction function. The experiment focused on the relationship between the rotors vibration displacement and its staying position for the self-correction. The result proved that the rotor always stays at the position where the displacement is smallest by cutting a slit into the rotor. Moreover, it has also been found that the stable self-correction of rotor angular displacement depends upon both the rotor driving frequency and rotor clamping force.

An Encoder-Less Ultrasonic Stepping Motor Using Open-Loop Control System

The construction of a light-load ultrasonic stepping motor for a watch device, and its angular displacement control by the open-loop control are described. In this control system, a rotary encoder as an angular displacement sensor is not used. A function of an angular displacement self-correction is added to an ultrasonic motor itself, applying a new type rotor and a new drive method. As a result, the correct setting of an angular displacement has been achieved with no use of the rotary encoder.

Driving and Controlling of a Watch Device Ultrasonic Motor by Two Phase Pulse Signals

A drive and control system of a light-load ultrasonic motor for a watch device is described. The ultrasonic motor is driven with two phase pulse signals having π/2 phase differences and 50% duty cycles. An angular displacement is detected by a rotary encoder and a rotor moves a 6 deg. step per second. The experimental results using the system have proved that the light-load ultrasonic motor can be used as a stable stepping motor for a watch device.

Effect of Pressing Force Applied to a Rotor on Disk-Type Ultrasonic Motor Driven by Self-Oscillation

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.

Characteristics and a New Control Method of a Same-Phase Drive-Type Ultrasonic Motor

This paper deals with a same-phase drive-type ultrasonic motor, using two degenerate bending vibration modes of a disk. Characteristics of the motor driven at low input power are shown. Signal waves picked up from a rotor are also shown. It is found that these signals are closely related to revolution states of the motor. Moreover, a new control method for the motor is proposed and tried.

Electromechanical Filter Composed of Transversely Vibrating Resonators for Low Frequencies

An electromechanical bandpass filter that is suitable for low frequencies is described. The mechanical filter consists of two transducer‐resonators and two couplers, of which the transducer‐resonators vibrate transversely and are coupled at their nodal points with the torsionally vibrating couplers. Each transducer‐resonator consists of two pieces of electrostrictive material with a basis reed sandwiched between them. Also, in this paper, the effects of impedance of electrostrictive material on the basis reed are analyzed. In order to analyze the mechanical vibrating system, mechanical network theory is adopted.

Operating Characteristics of a Same-Phase Drive-Type Ultrasonic Motor Using a Flexural Disk Vibrator.

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 motors operating characteristics can be adjusted via an electrical element connected to the control terminal.

Excitation of an Asymmetric Displacement without Residual Vibration and its Application to Construct a Piezoelectric Actuator

This paper deals with a new excitation method of a piezoelectric actuator in order to achieve its asymmetric displacement as a function of time elapsed without its residual vibration: The method is to use the rectangular pulse of voltage and is aimed to develop a new type piezoelectric actuator with a function of a both direction operation. Analysis on displacement of such an actuator driven by the rectangular pulse, and proposal of its application to concrete actuators with its experimental description are reported.