JPH06331365A - Method of calibrating rotary angular velocity sensor - Google Patents

Abstract

PURPOSE:To achieve the accuracy of a correlation chart between an input angular velocity of an optical fiber gyrosensor and an output signal thereof by applying an input angular velocity stable with a higher accuracy using a spinning angular velocity of the earth. CONSTITUTION:A rotary surface of a rotary base is arranged horizontally and a sensing coil 12 is arranged with a loop surface vertical to the surface of the base 11. An angular velocity to be inputted into an optical fiber gyroscope is given by OMEGA=OMEGAeXcosthetaeXcostheta (OMEGAe=15 deg./hour, thetae = latitude at a calibration point) by an angle theta with respect to the direction (east west) of spinning of the earth of the loop surface. Therefore, a correlation chart can be obtained from a signal to be outputted when the loop surface is turned by the angle horizontally with the base 11 and a formula. The determination of a bearing is made by astronomical observation when the angle theta=0 and the base is turned by the angle theta from the direction to input the rotary angular velocity OMEGA. Actually, a bearing sensor is set on the base 11 and the bearing of a sensing loop surface is set from the bearing indicated with a bearing sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calibrating a rotational angular velocity sensor, particularly an optical fiber gyro sensor.

[0002]

2. Description of the Related Art A conventional method for calibrating an optical fiber gyro sensor will be described with reference to FIG. The rate table 22 is a turntable that rotates at a rotation angular velocity instructed by an external controller 21 such as a personal computer or the like, a rate table controller 24, etc., and an optical fiber gyro sensor 23 to be calibrated is mounted on the table 20 on the upper surface of the rate table. ing. Reference numeral 12 is a sensing coil, and 13 is a signal processing circuit, each of which constitutes a main part of the optical fiber gyro sensor. FIG. 5 shows an example of a phase modulation type optical fiber gyro sensor. This optical fiber gyro sensor includes a sensing coil 2 in which an optical fiber is formed in a loop shape, the light from the light source 1 is divided into two by a multiplexer / demultiplexer 4, and each light is incident from different ends of the sensing coil 2. Then, after transmitting in the sensing coil 2 in mutually opposite directions, they are combined again by the multiplexer / demultiplexer 4 and the light is guided to the photodetector 6 via the multiplexer / demultiplexer 3 to be converted into an electric signal. It is a sensor that detects the angular velocity from the phase difference between two lights that have been converted and transmitted in the sensing coil 2 in opposite directions by the signal processing circuit 7. In addition, 5 is an optical fiber polarizer and 8 is a phase modulator. In the calibration method, first, the optical fiber gyro sensor 23 is mounted on the table 20 attached to the rotary shaft of the rate table 22, and the rate table 22 is rotated according to an instruction from the external controller 21. A signal is output from the optical fiber gyro sensor 23 with the rotation, and the signal output is recorded. Thereby, the correlation of the output signal of the optical fiber gyro sensor with respect to the input angular velocity to the rate table can be obtained. FIG. 4 shows a correlation diagram 33 of the input angular velocity 31 and the output signal 32. This correlation diagram is stored in the RAM in the optical fiber gyro sensor, and based on this correlation diagram, the rotational angular velocity corresponding to it is derived from the gyro signal output when the optical fiber gyro sensor rotates. That is, the calibration of the optical fiber gyro sensor requires the work of creating the correlation between the input angular velocity and the output signal shown in FIG. 4 and storing the correlation in the optical fiber gyro sensor.

[0003]

[Problems to be Solved by the Invention]

(1) To calibrate the optical fiber gyro sensor, it is necessary to create a correlation diagram of the output signal with respect to the input angular velocity. Therefore, if the input angular velocity is inaccurate, the correlation diagram will be inaccurate. Therefore, it is necessary to prepare a rate table that can rotate with high accuracy. (2) When the input angular velocity in the correlation diagram is a very small rotational angular velocity, it is necessary to prepare a rate table with high accuracy and high resolution as in (1). However, when the input angular velocity is 1 degree / hour or less, it is actually impossible to prepare a rate table that rotates with high accuracy (accuracy 1% or less).

[0004]

SUMMARY OF THE INVENTION The present invention uses a rotation angular velocity of the earth instead of a rate table for calibrating a rotation angular velocity sensor, particularly an optical fiber gyro sensor, and thereby enables highly accurate rotation. It is possible to provide a high-precision and stable input angular velocity to the optical fiber gyro sensor, while eliminating the need for a rate table. In addition, the accuracy can be significantly improved even at a low rotational angular velocity, and the accuracy of the correlation diagram between the input angular velocity and the output signal of the optical fiber gyro sensor can be improved.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. First, an optical fiber gyro sensor is mounted on a turntable 11 that is rotatably attached to a fixed base 10. In the figure, the sensing coil 12 and the signal processing circuit 13 are directly displayed on the turntable for easy understanding of the structure of the sensing coil. In the configuration of the optical fiber gyro sensor shown in FIG. 5, the light source, the coupler, the polarizer, the phase modulator, the light receiver, etc. are housed in the hollow portion of the bobbin around which the optical fiber constituting the sensing coil is wound. There is. The signal processing circuit 13 is connected to a personal computer 21 for data processing. The rotation surface of the turntable 11 is arranged in a horizontal state, and the sensing coil 12 in which an optical fiber is wound around a metal bobbin is arranged with the loop surface perpendicular to the surface of the turntable. At this time, the angular velocity Ω input to the optical fiber gyro is represented by the following equation (1) depending on the angle θ of the loop surface with respect to the rotation direction of the earth (east → west). _{Ω = Ω N × cosθ (1} ) Ω N = Ωe × cosθe (2) where, Ωe = 360/24 (degrees / hr), .theta.e the calibration point latitude. Therefore, by using the turntable, the correlation diagram can be obtained from the signal output when the loop surface is rotated by the angle θ in the horizontal direction and the equation (1). When the angle θ = 0, the azimuth determination is performed by astronomical observation such as North Star, and the turntable is rotated by the angle θ from that direction, and the rotational angular velocity of the expression (1) is input. In order to input the rotational angular velocity to the sensing loop, actually, instead of directly setting the input angular velocity by using the formula 1 based on the rotational angle of the turntable, an orientation sensor such as a gyro compass is installed on the turntable. Every time, from the direction indicated by the direction sensor,
Set the orientation of the sensing loop plane. At this time, the sensing loop plane and the reference plane of the azimuth sensor must be matched in advance. That is, when the loop surface indicates north-south direction, the direction sensor also indicates north-south direction.

[0006]

【The invention's effect】

(1) Since the rotation angular velocity of the earth is used in the calibration method of the present invention instead of using the rate table, a highly accurate and stable input angular velocity can be obtained with an optical fiber without using a rate table that rotates with high precision. It can be easily given to the gyro. (2) It has become possible to calibrate a high-precision gyro that detects low rotational angular velocity.

[Brief description of drawings]

FIG. 1 is a front view of a calibration device used in the present invention.

FIG. 2 is a partial top view of the calibration device showing only the sensing coil and the signal processing device of the optical fiber gyro sensor used in the present invention.

FIG. 3 is a front view of an apparatus used in a conventional calibration method.

FIG. 4 is a correlation diagram of an input angular velocity and an output signal.

FIG. 5 is a block diagram of an optical fiber gyro sensor.

[Explanation of symbols]

 10 Fixed Stand 11 Turntable 12 Sensing Coil 13 Signal Processing Circuit 20 Table 21 External Controller 22 Rate Table 23 Optical Fiber Gyro Sensor 24 Rate Table Controller 31 Input Angular Velocity 32 Output Signal 33 Correlation Diagram

Claims (2)

[Claims] 1. An optical fiber gyro sensor having a sensing loop in which an optical fiber is wound around a bobbin is mounted on a turntable having a rotation surface arranged horizontally, and the sensing loop surface is positioned perpendicular to the rotation surface of the turntable. It is mounted on the sensor, and the turntable is rotated to rotate the sensing loop surface by a predetermined angle θ from the reference position, and the angular velocity Ω due to the rotation of the earth corresponding to the angle θ is given to the sensing loop.
The information based on this is output as an electric signal of the optical fiber gyro sensor, so that the angle θ
By changing the angular velocity Ω and outputting an electrical signal corresponding to this, the correlation between the rotational angular velocity input to the optical fiber gyro sensor and the signal output of the optical fiber gyro sensor caused by this rotational angular velocity. A method for calibrating a rotation angular velocity sensor, characterized by obtaining 2. The method for calibrating a rotational angular velocity sensor according to claim 1, wherein the reference position is in the east-west direction, and the angular velocity Ω generated in the sensing loop by the angle θ formed between the reference position and the sensing loop surface is Ω = Ωe × cos θe × cos θ (in the above equation, Ωe = 15 degrees / hour, θe is the latitude of the calibration point)
The rotation angular velocity sensor is characterized by obtaining the correlation between the rotation angular velocity input to the optical fiber gyro sensor and the signal output of the optical fiber gyro sensor generated by this rotation angular velocity by changing the angle θ. Calibration method.