Sumio Sugawara

Construction of Ultrasonic Motors and their Application

This paper deals with construction of an ultrasonic motor and their application; a paper-sending device using a flat rectangular type ultrasonic motor is described. Various types of ultrasonic motors can be constructed by considering displacement combinations in the horizontal and vertical directions at the elliptic motion yielded. As for this elliptic motion, multi-mode vibrators using degenerate modes of the same or different form are utilized.

Ultrasonic Motors Using Piezoelectric Ceramic Multi-Mode Vibrators

The purpose of this paper is to report development of an ultrasonic motor using piezoelectric ceramic multi-mode vibrators of circular or annular plates, in which degenerate horizontal vibration modes of the same or different form are used. Some constructions of the motor and its experimental characteristics are presented. The ultrasonic motor investigated herein shows special merit in its thin construction.

Construction of Frequency-Change-Type Single-Crystal Silicon Two-Axis Acceleration Sensor

The construction of a frequency-change-type single-crystal silicon two-axis acceleration sensor is proposed and is designed using the finite-element method. The sensor element is composed of two developed bending vibrators, a mass and support bars. The volume is about 4.0×4.2×0.5 mm3. The 1st out-of-plane vibration mode in the vibrator is used here, and the resonance frequency is about 80 kHz. The analyzed relationship between the applied acceleration and the resonance frequency change becomes linear in this sensor construction. A sensor sensitivity of about 468 ppm/G is realized. When acceleration is applied, the sensor mass moves in parallel along the x- and y-axes and does not rotate. Therefore, the linearity of sensor sensitivity with respect to the applied acceleration is consistently maintained.

Basic Consideration of a Flat-Type Acceleration Sensor Utilizing the Resonance Frequency Shift in the Flexural Vibrator

In this paper, a flat-type structure for the acceleration sensor utilizing the resonance frequency shift in the flexural vibrator is proposed, and the design guideline considering the influence of support is clarified by the finite-element analysis. The resonance frequency shift in the vibrator is produced by axial force due to acceleration. The resonance frequency and quality factor are negligibly influenced by adding support and also by adding mass, because the displacements at both ends of the vibrator are very small. The relationship between the acceleration and the resonance frequency change becomes linear. The influence of the undesirable acceleration from other axes is also analyzed. It was clarified that high sensitivity and reduction of the undesirable acceleration are realized by adding mass and by devising a support. This new structure is expected to be a small low-cost crystal sensor that can be fabricated by mass production.

Construction of a New Flat Force Sensor Using the Resonant Frequency Shift by Axial Force

A new structure of flat force sensors using the resonant frequency shift of a flexurally vibrating bar by the axial force is proposed in this paper. The sensor structure is composed of only one flexurally vibrating bar called a central arm and two short arms flatly arranged on both sides at both ends. As the displacements at the base ends can be extremely reduced by balancing these arms, the structure is not affected by a support. The dimensions of the force sensor are determined by the finite-element analysis when using the out-of-plane modes. The resonant frequency changes with application of the axial force to the both base ends. The rate of change for the first mode is larger than that for the second mode. This structure is suitable for mass production, and therefore will be expected as a low-cost force sensor with high stability and sensitivity.

Experimental Consideration of Acceleration Sensor Utilizing Resonance Frequency Change of Flexural Vibrator

In this paper, the characteristics of the acceleration sensor utilizing the resonance frequency change in the flexural vibrator are examined experimentally. The sensor sample was produced using stainless steel. It was confirmed that the relationship between the applied acceleration and the resonance frequency change becomes linear and almost coincides with the theoretical value by the finite element analysis. The sensor sensitivities of approximately 2800 ppm/G and 2150 ppm/G are measured in the cases of using the 1st and 2nd modes, respectively. It was clarified experimentally that the spurious vibrations do not appear in the vicinity of the resonance frequency f0. Moreover, it is shown that this sensor can also be used as an inclination angle sensor.

Fundamental Considerations of Excitation of a Flexural Progressive Wave and its Application

This paper deals with fundamental considerations of excitation of a flexural progressive wave and its application to an ultrasonic motor. The conditions for excitation of a progressive wave not only in a straight line flexurally vibrating medium, but also in a flexural disk vibrator are made clear, and conditions of the excitation method for an ultrasonic motor are reported to be very similar to those for an electro-magnetic induction motor. Characteristics of a disk vibrator for an ultrasonic motor and results of fundamental experiments on it are also described.

Finite Element Analysis of Displacement at Base Portion of a Quartz Crystal Tuning Fork

A finite element method is used to analyze the displace- ments at the base portion of B quartz crystal tuning fork for a wristwatch unit. From the analysis, the quantitative reason for the great improve- ment in the effective reasonant quality factor Qe of the supported tun- ing fork with ann comers cut off becomes clear. This desirable charac- teristic is also realized in tuning forks with a circle hole at the slit end or those with a wide base portion.

Finite Element Analysis of Sensitivity of Frequency-Change Force Sensor

The characteristics of various frequency-change force sensors were analyzed using the finite-element method and compared. In the case of the sensor design, displacements at both ends of the sensor must be made as small as possible to reduce the influence of fixation, and the resonance frequency of the sensor must be considerably changed by the axial force to realize high sensitivity. The displacements ui (i=x,y,z) were analyzed as the ratio ui/ui0 to the maximum displacement ui0 at the central part of the long arm of the sensor, and then the sensor structure with the ratio ui/ui0, which is less than 10-3, was clarified. In addition, the change Δf of the resonance frequency f0 by the axial force was analyzed. The force sensor with a flat and simple structure, which is preferable as a micro electro mechanical system (MEMS) sensor, was shown to be best from the standpoint of high sensitivity and small displacements.

Improvement of Transitional Response Characteristics of a Piezoelectric Vibratory Gyroscope

We describe the transitional responses in piezoelectric vibratory gyroscopes used as angular rate sensors. The transitional responses for a stepped angular velocity and an external impulse force are experimentally determined. Then, it is shown that these responses are dependent on the difference between the two resonant frequencies in the gyroscope. A new gyroscope structure, in which the null signal is reduced and the responses are improved by using the active damping method, is proposed. The improved responses are presented and the design conditions are clarified.