Masanori Yachi

Design methodology of single crystal tuning fork gyroscope for automotive applications

This paper presents a method of designing a single crystal tuning fork vibratory gyroscope for stabilizing temperature sensitivity changes and reducing the noise from the external vibration by increasing the inertia moment of the device. As a result a detection mode Q value of 10,000 was realized. A sensitivity change of within /spl plusmn/5% was obtained after correcting the temperature dependence by a thermistor. Simultaneous incrementing of the inertia moment resulted in an enlargement of the fixed area of support. It was also found that the noise level from vibration decreased to less than 1/5.

H-Type Single Crystal Piezoelectric Gyroscope of an Oppositely Polarized LiNbO3 Plate

For obtaining greater accuracy and stability of piezoelectric gyroscopes, the authors have advanced the research on H-type LiTaO3 single-crystal piezoelectric gyroscopes, which combine the tuning fork vibration with H-type vibration. In this paper, the H-type LiNbO3 gyroscope of an oppositely polarized single crystal plate is reported. The electromechanical coupling factor of LiNbO3 is larger than that of LiTaO3 for the flexural vibration mode. Using an oppositely polarized plate, the electrode construction without a side electrode becomes possible. Therefore, the possibility of miniaturizing the H-type single-crystal piezoelectric gyroscope is examined to obtain the same sensitivity level. In the trial experiment, the dimensions of the LiNbO3 gyroscope were reduced to be 1/8 that of the LiTaO3 gyroscope.

Third-overtone resonator using thickness longitudinal mode of 36° Y-LiNbO3

The energy trapping characteristic of the thickness longitudinal mode propagating in a 36° rotation Y-cut LiNbO3 single crystal is theoretically analyzed. It is found that the fundamental wave has a high-frequency cutoff characteristic and the third overtone has a low-frequency cutoff characteristic. It is shown that a third-order overtone resonator with a small resonant level of the fundamental wave can be obtained. Further, a simulation analysis of the vibration displacement distribution is performed by the finite element method. The device dimensions for further improvement of the degree of suppression of the fundamental wave are experimentally derived. Based on these investigation results, a 34-MHz resonator was fabricated and a third-overtone resonator with a small fundamental response level with a resonance sharpness of 15,000, a capacitance ratio of 97, and a temperature characteristic of approximately –70 ppm/°C was obtained. The resonator is being mass produced as a clock resonator for a microprocessor operating between 25 and 100 MHz.

Supporting structure for LiTaO/sub 3/ crystal tuning fork vibratory gyroscope

/sup T/his paper describes a new supporting structure for a LiTaO/sub 3/ crystal tuning fork vibratory gyroscope. A conventional gyroscope has a large amount of cross-talk which is 67.4 (deg/s) maximum. By using the Finite Element Method (FEM), we clarified that the swing of the tuning fork was the cause of cross-talk. We proposed a new supporting structure in which the tuning fork element is fixed stationary to a rectangular holder plate which has a groove at each nodes of the detecting vibrations. The holder plate is fixed with silicone resin to a rigid arm through a groove. Due to this new structure, the mechanical Q of the detecting mode is not suppressed while the swing of the element is suppressed at the same time. The maximum cross-talk level was reduced to 2.5 (deg/s). This gyroscope with the new supporting structure is suitable for various applications, such as for automotive applications.