Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
1999-02-08
2001-02-27
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
C073S504040
Reexamination Certificate
active
06192756
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibrator for an angular rate sensor used for detecting a turning angular rate in a turning system, a vibratory gyroscope using the vibrator, a linear accelerometer and a method for detecting a turning angular rate.
2. Description of the Related Art
Up to now, as an angular rate sensor used for detecting a turning angular rate in a turning system, a vibratory gyroscope using a piezoelectric member has been used for detecting position of an aircraft, a ship, or a space satellite. Recently, it is used in a car-navigation system, a movement detecting mechanism in a VTR or a still camera in the field of public livelihood.
Such a vibratory gyroscope utilizes the concept that, when an angular rate is applied to a vibrating object, Coriolis force is generated in the direction perpendicular to the vibratory direction. Its mechanism is analyzed by using a dynamic model (for example, “Handbook of Elastic Wave Device Technologies” (Danseiha-Sosi Gijutsu Handbook) issued by Ohm, Inc., pp.491 to 497). Various kinds of piezoelectric vibratory gyroscopes have been proposed up to now. For example, a Sperry tuning-fork gyroscope, a Watson tuning-fork gyroscope, a regular-triangle prism-shaped tuning-piece gyroscope, a cylindrical tuning-piece gyroscope are known as a piezoelectric vibratory gyroscope.
This type of vibratory gyroscope utilizing a disk-shaped vibrator was disclosed, for example, in U.S. Pat. No. 5,540,094, in which driving vibration, for example with four nodes, was excited in the disk-shaped vibrator, the vibrator was then turned around an axis perpendicular to the disk-shaped vibrator to induce detection vibration, whose amplitude was detected. Such induced detection vibration also comprises four nodes within.
SUMMARY OF THE INVENTION
However, such a vibrator does not necessarily have sufficiently high sensitivity. Moreover, noise, inevitably induced by the driving vibration, tends to impede the necessary detection vibration. As a result, the contribution of the amplitude of the detection vibration is accurately separated from all the detection signal including the noise only with great difficulty. Such difficulty of separation also lowers the sensitivity and the signal
oise ratio.
The inventors are studying various applications of vibratory gyroscopes, and, for example, have tried to use a vibratory gyroscope as a turning rate sensor used in a automobile body control system applying a turning rate feedback method. Such a system detects the direction of a steering wheel itself by a turning angle of the steering wheel. At the same time, the system detects a turning rate of the actually turning car body by means of a vibratory gyroscope. The system then finds a difference between the direction of the steering wheel and the actual body turning rate by comparing them with each other, and attains stable body control by compensating a wheel torque and a steering angle on the basis of this difference.
However, most conventional piezoelectric vibratory gyroscopes can detect a turning angular rate only when the vibrator is arranged in parallel with the axis of turning (what is called “vertical arrangement”). The turning axis of a turning system to be measured is usually perpendicular to the gyroscope mounting part. Accordingly, when mounting such a gyroscope, it has been impossible to shorten the gyroscope in height, namely, to reduce the gyroscope in size in the direction of the turning axis.
An object of the invention is to provide a vibratory gyroscope and vibrator having a high sensitivity and signal
oise ratio and based on a novel principle.
The invention provides a vibrator comprising a primary loop-shaped vibration system, another vibration system vibrating independently from the loop-shaped vibration system, and a connecting portion connecting the loop-shaped vibration system and another vibration system.
The invention also provides a vibratory gyroscope for detecting an angular turning rate in a turning system, comprising the above vibrator, an exciting means for exciting driving vibration in the vibrator and provided in one of the primary loop-shaped vibration system and said another vibration system, and a detecting means for detecting detection vibration occurring in the vibrator when the vibrator is turned and provided in the other of the loop-shaped vibration system and another vibration system.
The invention also provides a method for detecting a turning angular rate in a turning system using the above vibrator, comprising:
providing an exciting means in one of the loop-shaped vibration system and said another vibration system,
providing a detecting means in the other of the loop-shaped vibration system and said another vibration system,
exciting driving vibration in the vibrator by the exciting means, and
detecting detection vibration induced in the vibrator when turning the vibrator by the detecting means.
The invention also provides a linear accelerometer for measuring a linear acceleration, comprising the above vibrator, and a detecting means for detecting the deformation of the vibrator induced by Newton's force effected on the vibrator when the vibrator is subjected to a movement in a linear acceleration.
The inventors have researched about a principle of the vibration of a vibrator to be used for a vibratory gyroscope, and have developed a vibrator and vibratory gyroscope based on a novel principle.
That is, the inventors developed the following idea. By providing a vibrator with a loop-shaped vibration system, another vibration system vibrating independently from the loop-shaped vibration system, and a connecting portion connecting the above systems, the vibration components of the loop-shaped and another vibration systems may be effectively separated, and driving vibration may be excited in one of the vibration systems and detecting vibration may be induced in the other. For example, when driving vibration is excited in the loop-shaped vibration system and the vibrator is not turned around a specified axis (an angular turning rate is 0), another vibration system may not substantially vibrate. When the vibrator is turned, Coriolis force is effected on the loop-shaped vibration system responding to the driving vibration to induce detection vibration in the vibrator. The detection vibration is detected in another vibration system.
“Another vibration system may not substantially vibrate” includes that the vibration induced in another vibration system has an amplitude not higher than {fraction (1/1000)} of the maximum amplitude of the driving vibration.
In prior vibratory gyroscopes, driving vibration excited in a driving vibration arm affected a detection arm in a certain manner, causing some stress within it to induce some noises in the detection signal. Moreover, the above described prior vibratory gyroscope using a disk-shaped vibrator has relatively low sensitivity and signal
oise ratio, because driving vibration induces inner-stress within the vibrator. According to the invention, such noise inevitably induced in a detection signal may be reduced or prevented. Thus the invention provides a solution to the above problem inherent in a vibratory gyroscope.
In the invention, the loop-shaped vibration system and another vibration system may preferably be extended in a specified plane. In this embodiment, the systems may be extended or formed within a certain thickness containing the specified plane. The thickness may be easily determined and understood by those having ordinary skill in the art and may preferably be not higher than 1 mm. In this embodiment, the vibrator may comprise another portion or portions other than the loop-shaped and another vibration systems, and another portion may be protruded, although the whole vibrator may preferably be formed in the specified plane in the above meaning.
The loop-shaped vibration system has a geometrical shape of a loop and does not necessarily have a circular shape, although the system may preferably have a circular or an el
Gouji Shosaku
Kikuchi Takayuki
Osugi Yukihisa
Soma Takao
Burr & Brown
Moller Richard A.
NGK Insulators Ltd.
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