JPH05164560A - Azimuth sensor - Google Patents

Abstract

PURPOSE:To obtain the sensor which is lightweight, miniature and inexpense without any error by detecting an angle applied to a geomagnetic sensor based on the phase difference of clockwise and unclockwise turn light transmitting a sensing loop by the use of an optical fiber gyro. CONSTITUTION:An optical fiber gyro 2 is combined with a geomagnetic sensor 1 to form a hybrid type azimuth sensor. The azimuth change output of the geomagnetic sensor 1 and the angle change output of the optical fiber gyro 2 are input to a controller 3, the output of the geomagnetic sensor 1 is corrected by comparing and processing both the above outputs and an azimuth without any error is output to a display 4 or the other device. Because an ellipse which indicates the output voltage trace of the geomagnetic sensor 1 is changed by an environment, the center coordinate and the constant of the ellipse cannot be determined in the expression of an azimuth angle for mounting it on a car or a ship. There, angle data obtained by the use of the optical fiber gyro 2 are input to the controller 3 together with the azimuth data of the geomagnetic sensor 1 for the purpose of correcting the coordinate and the constant thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orientation sensor, and more particularly to an orientation sensor having a hybrid structure of a geomagnetic sensor and an optical fiber gyro.

[0002]

2. Description of the Related Art As an orientation sensor, a geomagnetic sensor for detecting the magnetic field of the earth, a mechanical gyrocompass utilizing the rotation of the earth and the direction retention of a rotating coma, and an optical gyrocompass utilizing the Sagnac effect. Is commonly used.

As shown in FIG. 4, the geomagnetic sensor has a toroidal core 41 wound with an exciting coil 42, and detection coils U and V wound in directions orthogonal to each other. When the geomagnetism H ₀ that intersects the detection coils U and V at an angle of θ is applied, the azimuth θ is detected by the detection coils U and V as shown in the following equation.
Is calculated by the arc tangent of the ratio of the voltages V _U and V _Y respectively induced in the.

Θ = tan ⁻¹ (V _U / V _Y ) (1) A mechanical gyro compass is an angle sensor that uses the law of conservation of angular momentum of a rotating body, and has three axes orthogonal to each other. It is possible to rotate about the XX axis, rotate around the YY axis as the horizontal axis, and rotate about the ZZ axis as the vertical axis. When the mechanical gyro operates and the rotating body rotates at high speed, its axis continues to point in a fixed direction with respect to space without being affected by the rotation of the earth unless torque is applied. The azimuth is detected by utilizing this.

The optical gyro compass obtains the azimuth by detecting the rotation angular velocity of the earth to find the direction of the rotation axis of the earth. A fiber optic gyro is used to detect the rotation angular velocity of the earth. The optical fiber gyro is a sensor that detects an angular velocity, and the angle is obtained by adding a product of the angular velocity and time by using a timer in the CPU. Therefore, the relative angle change can be detected, but the azimuth cannot be detected. For this reason,
The rotation direction of the earth is obtained by detecting the rotation angular velocity of the earth. The optical fiber gyro has a structure as shown in FIG. The illustrated example is a phase modulation type optical fiber gyro, and has attracted attention because it has a relatively simple configuration and is inexpensive. The light emitted from the light source 11 passes through the coupler 12 and the polarizer 13, is branched by the coupler 14, and is incident on both ends of the sensing coil 16 as clockwise light and counterclockwise light, respectively. The light returning through the sensing coil 16 is combined by the coupler 14, passes through the polarizer 13, and is branched by the coupler 12.
The light receiver 17 converts the current signal into a current signal proportional to the light intensity. Although the detection intensity of the light receiver 17 is constant when stationary, a phase difference occurs between the two-direction light due to the addition of the angular velocity, and the light intensity changes. The angular velocity is obtained from the change in the light intensity, and this is integrated to obtain the angle.

[0006]

By the way, although an error occurs in the azimuth sensor, the problem is the deviation angle and the error. The declination is the angle between the direction of the horizontal magnetic force of the earth's magnetism and the direction north of the ground plane, which is the angle corresponding to the azimuth of the direction of the magnetic field, and is absolutely geographically generated. The deviation is the difference between the readings when a defect-free compass is left stationary in space and when it is mounted on a ship or aircraft at the same geographical position, and it occurs individually on the aircraft. ..
An orientation sensor that minimizes these errors is desired.

However, each of the above-described conventional orientation sensors has the following drawbacks.

(1) In the geomagnetic sensor, the earth's magnetic field to be detected is extremely small. Therefore, when the sensor is mounted on, for example, a ship or a car, the geomagnetism is disturbed by the iron in the hull and various parts of the car body, which causes It is the azimuth error, that is, the error. In addition, it is difficult to use because the earth's magnetism is disturbed by the buried object and the structure, which causes the error. Permanent magnets are usually used for the error correction. There is a small case near the magnet type geomagnetic sensor, which is adjusted when a skilled person installs this sensor on the hull. As described above, the manual operation is required, which is very time-consuming, and moreover, it is difficult to be accurate because it is affected by the magnetic field. Note that, unlike the deviation, the deviation angle on the earth is known in advance, so it is relatively easy to correct it if the location of use can be specified, but it is always possible to obtain the deviation angle correction table at hand. It is troublesome because the operator has to calculate and calculate from the azimuth.

(2) The mechanical gyro compass is large, heavy, expensive, has a long starting time, is susceptible to vibration, and requires frequent maintenance.

(3) The optical gyro compass obtains the azimuth on the basis of a very small value of the rotation speed of the earth. Therefore, if the hull or body shakes, an accurate direction cannot be obtained.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art by adding an optical fiber gyro to the geomagnetic sensor to make it hybrid, and to reduce errors.
It is to provide an orientation sensor that is lightweight, small, inexpensive, and easy to use.

[0012]

The orientation sensor of the present invention comprises:
The detection coils are arranged in mutually orthogonal directions, and the azimuth angle is detected based on the azimuth data that includes the output voltage of the detection coil that changes according to the direction of the earth's magnetism. A geomagnetic sensor whose correction error varies depending on the environment, an optical fiber gyro that detects the angle applied to the geomagnetic sensor based on the phase difference between the left and right light that propagates in the sensing loop, and the geomagnetic sensor by the optical fiber gyro. Whenever the angle applied is detected and the angle difference detected by the geomagnetic sensor and the optical fiber gyro exceeds a specified value, the error correction value is calculated from the azimuth data of the geomagnetic sensor and the optical fiber gyro angle data obtained up to that point. , And a control means for correcting the output of the geomagnetic sensor by automatically updating its own correction value.

In order to automatically perform the declination correction in addition to the self-correction, the sensor has storage means for preliminarily storing the declination on the earth, latitude of the place where the magnetic sensor is used, Further, a detection means for detecting the longitude is further provided, and the control means specifies a location on the earth from the output of the detection means, reads the declination corresponding to the location from the storage means, and updates the declination correction value. Good. Further, in order to eliminate the error due to the inclination, it is preferable to mount the geomagnetic sensor and the optical fiber gyro on the horizontal holding device.

[0014]

The locus of the output voltage value when the geomagnetic sensor is rotated once is shown in FIG. When the geomagnetism is not disturbed, the circle is as shown in FIG. 2A, and when there is a disturbance, the circle is elliptical as shown in FIG. The azimuth angle θ is given by the following equation using the maximum voltage values V _Xmax and V _Ymax of the ellipse and the minimum voltage values V _Xmin and V _Ymin .

Θ = tan ⁻¹ {(V _Y −Z _Y ) / (V _X −Z _X ) * K} (2) where (Z _X , Z _Y ) is the center coordinate of the ellipse, and K = (V _Ymax −V _Ymin ) / (V _Xmax −V _Xmin ) Since the ellipse in FIG. 2B changes depending on the environment, the center coordinates (Z _x , Z _y ) of the ellipse and K are to be mounted on a car or ship. Cannot be set to a constant.

By the way, the above-mentioned optical fiber gyro is an angle sensor utilizing the Sagnac effect, and angle data can be obtained from the angular velocity to which the gyro is added.
If this is used together with a geomagnetic sensor, it is possible to know the environmental change when the sensor is mounted on a car or a ship, and it is possible to obtain the shape and center of the ellipse due to the environmental change of the geomagnetic sensor. That is, the optical fiber gyro can correct the center coordinates (Z _x , Z _y ) of the ellipse and the constant K necessary for the azimuth calculation of the geomagnetic sensor.

If there is no change in the error, the angle change Δθ _g detected by the optical fiber gyro should be equal to the angle change Δθ _m detected by the geomagnetic sensor. However, in reality, the difference changes, and therefore Δθ _g ≠ Δθ _m . However, since the optical fiber gyro also has an error factor of angular drift, a constant γ that determines the timing of executing the correction is required. This γ is determined by the performance of the two sensors. Here, α = | Δθ _g −Δθ _m α | (However, calculation is performed in a range in which an input of a certain time interval and a certain angle or more is added,
It shall be judged. ), When α exceeds a certain fixed value γ, new optimum values are newly obtained for the ellipse center coordinates and the constant K based on the past data of the geomagnetic sensor and the optical fiber gyro, and the azimuth is calculated based on these values. To detect. In this way, the azimuth detection accuracy is improved by automatically correcting the error.

[0018]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows the configuration of a hybrid azimuth sensor of this embodiment in which an optical fiber gyro is added to the geomagnetic sensor. The geomagnetic sensor 1 and the optical fiber gyro 2 are the same as those described in the conventional example. The azimuth change output of the geomagnetic sensor 1 and the angle change output of the optical fiber gyro 2 are input to the controller 3, and the outputs of the geomagnetic sensor 1 are corrected by comparing both outputs, and the azimuth without error is displayed. To the output device 4 or another output device. As described above, the elliptical shape that is the locus of the output voltage of the geomagnetic sensor 1 changes depending on the environment, so to mount it on a car or ship,
Z _X , Z _Y and K cannot be set to constants. Therefore, in the present embodiment, the angle data obtained by the optical fiber gyro 2 is used together with the azimuth data of the geomagnetic sensor in the controller 3
The above method is used to correct the above coordinates and constants. FIG. 3 shows an example of a flowchart of the correction process performed by the controller 3.

First, when the azimuth sensor is powered on, the controller 3 reads the declination correction value set in advance according to the sensor use location (step 301), corrects the declination and corrects the geomagnetic sensor. Match the detection direction with the direction north of the ground plane. This step is performed, for example, by reading a value set by a dip switch or the like. Subsequently, the own-correction value is read (step 302) and the initial own-error is corrected to zero. This step is, for example, an E ² ROM (electrically erasable read-only storage device)
This is done by reading the value stored in advance in. This difference value is updated as described later. In this way, the controller 3 reads the correction values and then detects the output voltages V _X and V _Y of the geomagnetic sensor 1 (step 303).

Next, it is judged whether or not the initialization of the optical fiber gyro 2 which is performed immediately after the power is turned on to detect the optimum phase difference is completed (step 304). In the case of no, after displaying the azimuth obtained based on the output voltage of the geomagnetic sensor 1 on the display device 4 or outputting it to another output device (step 305), the process returns to step 303 and the optical fiber gyro 2
The detection, determination, and display (steps 303, 304, and 305) are repeated until the initialization of is completed. After the initialization of the optical fiber gyro 2 is completed, the optical fiber gyro 2
The rotation angle θ of the sensor is detected by (step 30
6).

On the other hand, the angle change ψ is calculated from the data of the geomagnetic sensor (step 307), α = | θ−ψ | is calculated (step 308), and it is determined whether or not α is γ or more (step). 309). If not, controller 3
V _Xi , which is the calculation result of the geomagnetic sensor 1, in the memory of
V _Yi , θ _i (i = 1, 2, 3 ...) Is stored (step 3
10) After displaying the azimuth obtained based on the output voltage of the geomagnetic sensor 1 on the display 4 or outputting it to the output device (step 311), the process returns to the voltage detection step 303, and steps are performed until α becomes equal to or greater than a predetermined value γ. Repeat steps 303 to 311.

When the rotation angle difference α exceeds a predetermined value γ,
The following calculation is performed using the values of V _Xi , V _Yi , and θ _i stored in the memory of the controller 3. That is, using an elliptic expression V _Xi = A ₁ · sin (θ _i ) + B ₁ (3) V _Yi = A ₂ · cos (θ _i ) + B ₂ (4) composed of two equations, i = 1 to n Data values up to (n is an i value when θ ≧ α) are approximated by least squares, and A ₁ , A ₂ (ellipse major axis,
Minor axis length), B ₁ and B ₂ (ellipse center coordinates) are calculated (step 312). If these are obtained, the shape and center of the ellipse can be detected. ^{_{That, (V x -B 1) 2}} / A 1 2 + (V Y -B 2) 2 / A 2 2 = 1 (5) _{where, Z x = B 1, Z} Y = B 2, K = A ₂ / A ₁ The error correction value is updated based on this detection result (step 31
3), after resetting the values of α, θ, and ψ to zero (step 313), the process proceeds to the display step 311, and the azimuth is obtained from the output voltage of the geomagnetic sensor 1 based on the updated error correction value and displayed on the display unit 4. Display or output to an output device (step 311).

As described above, according to this embodiment, the optimum coordinates and the optimum constants are obtained from the azimuth data group of the geomagnetic sensor each time the rotation angle θ becomes a predetermined value or more by using the optical fiber gyro which is not influenced by the magnetic field. Since the center of the ellipse and the constant K that change depending on the environment are updated, the automatic deviation correction of the magnetic sensor can be realized without being affected by the magnetic field.

Further, in the above-mentioned embodiment, if the geomagnetic sensor and the optical fiber gyro are mounted on the horizontal holding means, that is, the gimbal that keeps the compass of the ship horizontal, that is, the error due to the inclination can be ignored, so that the stability is stable. Output is obtained.

According to the above-mentioned embodiment, only the own difference is corrected, but the present invention is not limited to this, and the deviation angle may be corrected. For example, the declination on the earth is inputted in advance in the memory of the controller 3, the place on the earth is specified by knowing the latitude and longitude of the place of use, and the declination corresponding to the place is read out to automatically determine the declination. It is possible to correct the angle. In this case, it goes without saying that the DIP switch is unnecessary.

[0026]

According to the present invention, the following effects are exhibited.

(1) According to the azimuth sensor of the first aspect, an optical fiber gyro that is not affected by the geomagnetism is added to the geomagnetic sensor for hybridization, and the optical fiber gyro automatically corrects the difference between the geomagnetic sensors. Since this is done, there are few errors and the azimuth accuracy can be improved. In addition, it can be easily realized by software of the control means, and it can be manufactured at low cost because the geomagnetic sensor and the optical fiber gyro are cheap, and since it has no mechanical structure, it has a quick start-up time, is lightweight and compact, and is maintenance-free. You can

(2) According to the azimuth sensor of the second aspect, since the deflection angle can be automatically corrected, the operability and the azimuth accuracy can be further improved.

(3) According to the azimuth sensor of the third aspect, by mounting the constituent elements of the sensor on the horizontal holding means, it is possible to effectively prevent the error due to the inclination, and the accuracy is remarkably improved. be able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an orientation sensor of the present invention.

FIG. 2 is a diagram showing an example of the locus of the output voltage of the geomagnetic sensor used in this embodiment.

FIG. 3 is a flowchart of a correction process according to this embodiment.

FIG. 4 is a measurement principle diagram of the geomagnetic sensor used in this embodiment.

FIG. 5 is a configuration diagram of a phase modulation optical fiber gyro used in this embodiment.

[Explanation of symbols]

 1 Geomagnetic sensor 2 Optical fiber gyro 3 Controller 4 Display

Claims (3)

[Claims] 1. A detection coil in which detection coils are arranged in directions orthogonal to each other, and a detection coil whose output changes according to the direction of the geomagnetism, and a geomagnetism for detecting an azimuth angle based on a circuit output which converts the output into a voltage. A sensor and an optical fiber gyro that detects the angle applied to the geomagnetic sensor based on the phase difference between the left and right light that propagates through the sensing loop, and the angle applied to the geomagnetic sensor by the optical fiber gyro is detected, and the geomagnetic sensor Each time the angle difference detected by the optical fiber gyro exceeds a specified value, the own correction value is calculated from the azimuth data of the geomagnetic sensor and the angle data of the optical fiber gyro obtained so far, and the own correction value is updated. And a control unit that corrects the output of the geomagnetic sensor by using the azimuth sensor. 2. Storage means for storing beforehand the declination on the earth,
The magnetic sensor is provided with a detection means for detecting the latitude and longitude of the place of use, the control means specifies a location on the earth from the output of the detection means, and the declination corresponding to the location is read from the storage means. The azimuth sensor according to claim 2, wherein the declination correction value is updated. 3. The orientation sensor according to claim 1, wherein the geomagnetic sensor and the optical fiber gyro are mounted on a horizontal holding device.