Subaru Kudo

Finite element analysis of single crystal tuning forks for gyroscopes

The single crystal tuning fork gyroscopes are analyzed by using the finite element method. The vibrational displacements of the gyroscope are calculated. As the calculated results of an x-cut quartz crystal tuning fork, whose base length is equal to the arm length, it becomes clear as the following. (1) For the horizontal driving mode, the displacements at the bottom of the base are below 1/1000 times as compared with the maximum displacement at the arm end. (2) For the vertical detecting made, the displacements at the base bottom are almost equal to 1/10 times in comparison with the maximum value. The validity of calculated result is experimentally confirmed. Then, the experimental results of the sensitivity and the response characteristics of the crystal gyroscope are shown.

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.

Vibration Characteristics of Trident-Type Tuning-Fork Resonator in the Second Flexural Mode for Application to Tactile Sensors

Tactile sensors are used for measuring the softness and hardness of an object. This paper presents a new tactile sensor with a trident-type tuning-fork resonator using the second flexural vibration mode. The vibration modes and displacements are calculated using the finite element method. The dimensions of the resonator, which are not influenced by supporting conditions, are determined. The calculated results are experimentally confirmed with the trident-type tuning-fork resonators fabricated for various trials. The experimental characteristics of the tactile sensor are shown by measuring the softness and hardness of test pieces. This trident-type tuning-fork resonator is expected to be a highly stable tactile sensor with a high quality factor.

Finite Element Analysis of H-Type Vibratory Gyroscope

This paper describes the H-type vibratory gyroscope used as an angular rate sensor. The vibrational displacements of the gyroscope are analyzed by the finite element method, and a new structure of the gyroscope, which can be supported at a zero-displacement point, is clarified. This H-type gyroscope is expected to be an angular rate sensor with a high quality factor and high stability.

Sensitivity of Frequency Change of Piezoelectric Vibratory Tactile Sensor Using Longitudinal-Bar-Type Resonator

Piezoelectric vibratory tactile sensors are used for measuring the softness and hardness of an object. In this paper, the sensitivity of the frequency change of the longitudinal-bar-type tactile sensor is presented. The approximate equation of the frequency change of the tactile sensor in contact with an object was derived using the distributed constant-circuit model. Then, the experimental characteristics of the manufactured tactile sensors were shown by measuring the softness and hardness of the test pieces. The sensitivity was increased when the resonator with higher resonance frequency was used. It was also clarified that the sensitivity was inversely proportional to the mass of the resonator. The obtained results will be useful for designing the piezoelectric vibratory tactile sensor.

Consideration of Figure of Merit of Piezoelectric Vibratory Gyroscope Using Charge Sensitivity

In this paper, charge sensitivity has been considered as a figure of merit of piezoelectric vibratory gyroscope. First, an approximate equation for charge sensitivity is derived based on an equivalent circuit of the gyroscope. Second, the charge sensitivity characteristics have been discussed in terms of the effects of frequency deviation and load capacitance. The difference between charge sensitivity and voltage sensitivity is quantitatively clarified. Charge sensitivity is effective as a figure of merit for applying a piezoelectric single crystal to the gyroscope.

Piezoelectric Actuator of LiNbO3 with an Integrated Displacement Sensor

We proposed a new actuator with an integrated displacement sensor. We examined the bimorph actuator using an oppositely-polarized LiNbO3 plate. The actuator shows a spurious transient response to driving step voltage due to two resonances (fundamental mode: 278 Hz, and secondary mode: 1720 Hz). We obtained an equivalent circuit model using the input impedance characteristics of the driving electrode and the sensor electrode. We could analyze the transient response of the actuator using the equivalent circuit model. Our simulation of the feedback circuit with an equivalent model showed the possibility of suppressing the ringing of the fundamental mechanical resonant mode.

Consideration on Temperature Characteristics of Sensitivity in Quartz Tuning Fork Gyroscope

The temperature characteristics of the double resonant frequencies of a quartz tuning fork gyroscope are analyzed by means of the finite element method. The temperature characteristics of the sensitivity of the gyroscope are calculated and the relationships between the variations in sensitivity and the frequency deviations are considered. The possibility of quantitative analysis of temperature characteristics of the sensitivity of gyroscope is shown.

Finite Element Analysis of Mechanical Couplings in a Tuning Fork Gyroscope

The mechanical couplings of a tuning fork gyroscope are analyzed by a finite element method. The mechanical couplings due to anisotropy and asymmetrical structure are discussed based on differences in materials. These couplings are estimated by calculating the double resonant frequencies and vibrating modes of the gyroscope. It is possible to analyze quantitatively the couplings for the anisotropy and the asymmetrical structure of the gyroscope.