JPS6148714A - Drift correction system of optical gyro - Google Patents

Abstract

PURPOSE:To detect an invariably accurate angular velocity of rotation by providing a means which turns over the rotational angular velocity detection surface of the optical gyro by 180 deg., and comparing detected quantities before and after the turning-over operation with each other and detecting a zero point. CONSTITUTION:An optical fiber gyro device is a single-body device formed by providing an optical module 7 to a drum 9 provided with an optical fiber coil 8, and the rotational angular detection surface of the optical gyro is inverted by 180 deg. to perform zero-point detection by comparing detected quantities before and after the inverting operation with each other. Therefore, drift correction of the optical gyro and the calibration of detection sensitivity are performed optionally during the use of the optical gyro, so tha accumulation of errors is eliminated and the invariably accurate rotational angular speed is detected.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to drift correction of optical gyros such as optical fiber gyros and ring laser gyros. This invention relates to an optical fiber gyro that can detect the amount of drift.

[Background of the invention]

Detection of rotational angular velocity is required for inertial navigation, attitude control, and display of running position of various moving objects such as aircraft, ships, automobiles, and robots. A type gyro was used.

However, in recent years, gyros that utilize various physical phenomena other than such mechanical gyros have come into practical use, and one of them is the gyro.

However, there are many types of optical gyros known, such as former fiber gyros and ring laser gyros.
The first is a basic example of the original fiber gyro.
To explain with a diagram, in FIG. 1, numeral 1 indicates a semicircular laser for a light source.

2 is an isolator, 3 is a beam splitter, 4° 4' is a lens, 5 is a light receiving element, 6 is a detector, 7 is an optical module constituting a detection processing section, 8 is an original fiber coil, and 9 is a drum.

The laser light sourced from the laser 1 passes through the isolator 2 and then enters the beam splitter 3, where it is split into two parts, each passing through lenses 4 and 4' to the original fiber 8.
The light enters the optical fiber coil 8 from one end 8a and the other end 8b, respectively.

The original fiber coil 8 is, for example, from several tens of meters to several thousand
An optical fiber with a length of approximately m is wound around a drum 9 to form a coil, and the laser light incident from one end 8a passes through the original fiber coil 8 while rotating clockwise. The coil 8 is pulled out from the other end 8b, and the laser beam incident from the other end 8b passes through the coil 8 while rotating counterclockwise, and then the coil 8 is pulled out from the other end 8a. Put out. And these ends 8a, 8b
The extracted laser beams pass through separate lenses 4 and 4' and return to the beam splitter 3, where they are combined and enter the light receiving element 5.

Therefore, the laser light incident on the light receiving cable 5 is interference light of the laser light that has passed through the optical fiber coil 8 in the clockwise direction and the laser light that has passed in the counterclockwise direction 9.

Therefore, now, point arrow A or B to this optical fiber coil 8.
When rotational motion in the direction of rotation ad+ about the central axis of the drum 9 as shown in is given at an angular velocity ω, the interference state of the laser light incident on the light receiving element 5 changes due to the Sagnac effect (the state of interference of the laser light incident on the light receiving element 5 changes) (intensity of brightness or darkness, or movement of interference fringes),
This is converted into an electrical signal by the light receiving element 5, and detected by the detector 6 as a signal that affects the rotational angular velocity ω.

Therefore, according to the original fiber gyro shown in FIG. 1, the plane perpendicular to the central axis of the drum 9 is used as the rotational angular velocity detection plane, and the thickness of the rotational angular velocity ω generated in the central axis rotation within this plane is determined. The direction of rotation can be measured.

By the way, in general, measurement processing that applies light can provide high resolution and is expected to be highly accurate. Changes in the refractive index can also have a significant effect on measurement operations, causing drift in measured values.

On the other hand, such deformation and change in refractive index occur due to temperature changes, and therefore, in conventional original gyros, there is a problem that drift due to temperature changes is significant and it is not possible to obtain an optical odd degree.

For example, in the original fiber gyro explained in FIG.
However, even a slight increase in temperature causes a change in the refractive index, and furthermore, due to deformation caused by a change in thermal tension, a difference occurs in the optical path for the laser beam. Furthermore, since the original fiber coil 8 made of a long optical fiber is included in the optical path, the original fiber coil 8
There are significant changes in the optical properties of the material, and the influence of temperature changes is particularly significant.

In order to prevent this, for example, it is possible to make the optical system as small as possible or to make it solid-state, but there are limits in terms of reduced sensitivity and solid-state technology.

It is also conceivable to perform temperature control, but this requires a high-precision temperature device (material) of '/10 to '/100'9, which poses the problem of being impractical from a cost standpoint.

In particular, long-term stability (low However, conventional optical gyros have the drawback of not being able to meet these requirements as they are.

[Purpose of the invention]

The purpose of the present invention is to eliminate the drawbacks of the prior art described above and to provide an optical gyro that can maintain a sufficiently stable high temperature without temperature adjustment (drift). The tli formal method is complete.

[Gist of invention]

In order to achieve this object, the present invention provides an optical gyro with means for inverting its rotational angular velocity detection surface by 180 degrees and then turning it over, and by comparing the detection output before and after inversion, the magnitude of the drift can be determined. It is characterized by the fact that it can be detected arbitrarily and precisely.

[Practical example of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drift arm correction method for an optical gyro according to the present invention will be described in detail below with reference to illustrated embodiments.

Before describing embodiments of the present invention, the principle of operation of the present invention will first be explained with reference to FIGS. 2 to 4.

Fig. 2 shows the basic Umenari of the gamma optical fiber gyro shown in Fig. 1, which has been constructed as a single practical fiber gyro device, in which the optical module 7 is replaced by an optical fiber coil 8. It is attached to a drum 9, which is a stand-alone device, to form a single device. Figure 2 (A) shows the state during normal detection operation (hereinafter referred to as the normal state), and Figure 2 (B) shows the state during normal detection operation (I). ) shows a state in which the state is reversed by 180 degrees and turned over (hereinafter referred to as an inverted state).

Next, Figures 3 (a) and (b) are explanatory diagrams of the Sagnac effect in the states of Figure 2 (0) and (naka), respectively, when a certain value of rotational angular velocity Δω is given to the fiber gyro. The solid line 8a' represents the optical path of the laser light that entered from the end 8a of the original fiber coil 8, and the broken line 8
Similarly, b' represents the optical path of the laser beam incident from the end portion 8b.

On the other hand, since the original fiber coil 8 is given a rotational angular velocity Δω, if the time required for the laser beam to pass through the optical fiber coil 8 is to, then this time t0
During this period, the optical fiber coil 8 rotates by Δω1o, and as a result, the rotation direction of the rotational angular velocity Δω (clockwise in FIG. 3)
The laser beam passes through the coil 8 in the same direction as the laser beam, the laser beam passes through the optical path indicated by the solid line 83' in Fig. 3 (A), and the optical path indicated by the broken line 8 b' in Fig. 3 (CI). The laser beam that passes through the other optical path, that is, the one in Figure 3 (
/I), the laser beam passes through the optical path indicated by the broken line 8b';
In (b), the laser beam actually passes through a longer optical path than the optical path of is a', and the Sagnac effect appears. It can be seen that the length relationship of the optical path is reversed between the normal state shown in FIG. 3(a) and the inverted state shown in FIG. 3(b).

Therefore, the optical fiber gyro is kept in the normal state shown in Fig. 3 (a) for a time t (H), and then the original fiber gyro is turned over and the state shown in Fig. 3 (b) is maintained for a time t (b). After that, turn it into the inverted state as shown in
It is assumed that the normal state shown in FIG.

Then, the rotational angular velocity detection signal S detected by the original fiber gyro during this time becomes as shown in FIG. In Fig. 4, time t(b) is the time taken to flip the optical fiber gyro from state (a) to state (b) in Fig. 2, and (b) in Fig. 2. ) from the state of (
It represents the time it takes to reverse to the state (a) and return to the normal one-width state.

Therefore, as is clear from these FIGS. 3(a) and 4(b), the detection signal S at time t0) is due to the rotational angular velocity Δω, whereas the detection signal S at time t(b) The detection at (*-!S is also based on the rotational angular velocity Δω, but as is clear from the comparison between (a) and middle) in Fig. 3, at this time t(b), the original The relationship of the optical path due to the fiber coil 8 is reversed, and therefore the direction of the detection signal S due to the rotational angular velocity Δω is also reversed, and therefore the detection signal S at this time [(b) becomes thicker at time t. What is the thickness of the detection signal S in @)? It can be seen that the difference is exactly 2 times the value ΔωS of the detection signal S corresponding to the rotational angular velocity Δω. As a result, the time t (the difference between the level of the detection signal S at In and the level at time t (B) is calculated, and the level corresponding to 1/2 of this difference (direct H) expressed as o - o) is calculated. This straight line O
-0 is the level representing the rotational angular velocity ω=0, that is, the zero point, and since this is the vibration or drift of this zero point, it is possible to correct the shift by this.

Therefore, we changed the rotational angular velocity detection surface to 180 degrees on the original gyro.
If a means for inverting the optical gyro and turning it over is provided, and at any point during use of the optical gyro, a series of inversion operations are performed on the optical gyro each time the rotational angular velocity given to it does not change. It can be seen that the zero point can be found at any time and that the drift can be corrected.

An embodiment of the present invention that can be operated to compensate for the above-described operation ljA of the present invention will be described below.

First, Figure 5 shows an example of the coordinate system of the rotational angular velocity that must be detected by the original gyro.
It's a makeshift device that uses optical gyros for the three axes of , Y, and Z to detect three-dimensional rotational angular velocity.
The rotational angular velocity of ωX with respect to the Z axis and the rotational angular velocity of ωy with respect to the Y axis? , and the rotational angular velocity of ω2 with respect to the Z axis are detected and used for inertia control and attitude control of a moving body.

FIG. 6 shows an embodiment in which the three-dimensional detection explained in FIG. In Figure 6, 10 is the 2t gyro body, inside which is the 5th gyro.
Rotational angular velocities ωX and ωγ in the three axis directions of X, Y, and Z shown in the figure.

Three sets of original gyros (optical gyros such as an optical fiber gyro and a ring laser gyro) are incorporated so that ω2 can be detected.

Reference numeral 11 represents a member fixed to the body of the moving object to be equipped with this gyro.

12 x , 12 y , and 12 z are drive-side clamps attached to the member 11 so as to be movable in the direction of the arrow in the figure.

13 x , 13 y , and 13 z are drive-side shafts that are inserted into and fixed to the respective drive-side clamps 12 x to 12 z.

Reference numerals 14
5 x , 15 y , and 15 x to generate rotational force.

16 x , 16 y , and 16 z are shafts fixedly attached to the gyro main body 1o.

17x, 17y, and 17z are clamps attached to the member 11 so as to be movable in the direction of the arrow in the figure.

Next, the operation of this embodiment will be explained.

For example, assume that it becomes necessary to correct the drift of the gyro in the detection operation of the rotational angular velocity ωX or ωy of the Z-axis or Y-axis.

Then, in this case, drive-side clamps 12x, 12y and clamp 17x for the Z-axis and Y-axis, respectively.

17y toward member 11, and each corresponds to ilA jlij 1141113 x, 1
3 Remove from y and axes 16x and 16y.

Next, ZiI! 1Ill motor 14z on the operating side,
The drive side clamp 12 z is fixed by the K. The shaft 15z is rotated with respect to the shaft 13Z, and the original gyro main body 10 is rotated 1 in a plane including the entire Z axis and YI1111.
After 80 counter rotations, the drive side shafts 13x and 13y are rotated to their corresponding clamps 17x and 17y, and the shaft 16
x and 16y correspond to the drive side clamp 12x
and 127, and then move the clamp 12x to the shaft 16x and the clamp 17 to the shaft 16x.
x to the shaft 13x, the clamp 12y to the shaft 16y, and the clamp 17y to the shaft 13Y to return the optical gyro main body 10 to the fixed state.

Then, in this state, from the state shown in Figure 6,
By reversing the X-axis direction and the YIIli1 direction in FIG. 5 by 180 degrees, the detection surface of the optical gyro for the rotational angular velocities ωX and ωy has been reversed.

Therefore, in this state, the rotational angular velocity ωX or ωy.

Alternatively, if both of these are detected and compared with the detection signal before inversion, as explained in FIG. You can know the zero point,
Drift can be corrected.

Incidentally, when it becomes necessary to correct the drift with respect to the rotational angular velocity ω2 of the Z-axis rotation 9, the clamps 12 z , 12 y , 17 z ,
17y, and motor 14x (or motor 14y
), the optical gyro body 10 may be inverted 180 degrees within a plane including the two axes and the Y-axis (or the Y-axis), and then the rotational angular velocity 2 may be detected.

The above operation is shown for the u-turn angular velocity detection signal around each axis 9 of X, Y, and Z.
This is the case when reversal is performed by the toe 9 motor 14z according to the axis, and in this section I, the zero points ΔωxS and ΔωyS on both the X and Y axes can be found and the drift can be corrected, and in the section 2, according to the Y axis, This is the case when the axis is reversed by the toe shifter 14x, and in this section (2), the zero points ΔωZS and ΔωyS on the inner axes of Z and Y can be found and drift correction can be performed.

In addition, ωis and ωXS in this FIG. The detection sensitivity can be calibrated. Note that in order to calibrate the detection sensitivity of the optical gyro on the Y axis, reversal may be performed using the motor 14y.

Therefore, according to this embodiment, since the drift correction of the 7Th gyro and the calibration of the detection Me can be performed arbitrarily while the optical gyro is in use, it is possible to eliminate the accumulation of errors, and the rotational angular velocity is always accurate. can be detected.

Although the above embodiments have mainly been explained with reference to optical fiber gyros, various types of optical gyros are known, and therefore, the present invention also applies to optical fiber gyros as well as ring laser type optical gyros. gyro,
Namely, mechanical dither type, magneto-optic bias type,
Needless to say, the present invention can be easily applied to Yuzuki's optical gyro such as the optical fiber resonance type.

〔Effect of the invention〕

As explained above, according to the present invention, the drift of the original gyro can be arbitrarily corrected while the optical gyro is in use. Even if a drift occurs, it can be corrected appropriately, and it is possible to easily provide a highly accurate original gyro which can always accurately detect rotational angular velocity without accumulating errors over a long period of time.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the basic configuration of an optical fiber gyro, FIGS. 2(a) and 3(b), and FIG. 3(a). (b) is an explanatory diagram for understanding the operating principle of the present invention. FIG. 4 is a characteristic diagram for explaining the operation, and FIG. 5 is an explanatory diagram of detected coordinates of the rotation angle in an embodiment of the present invention. FIG. 6 is a perspective view showing an embodiment of the optical gyro correction method according to the present invention, and FIG. 7 is a characteristic diagram for explaining its operation. 10... Optical gyro body, 12χ, 12y,
12z, curved, drive side clamp, 13x, 13y,
13z... Drive side shaft, 14x. 14y, 14z・-” motor, 15x,
15y, 15z, 16x, 16y. 16m・・・Axis, 17x, 17y, 17z
...Song clamp. Figure 1 (A) (B) Figure 3 Figure 4 Katama Figure 5 Figure 6

Claims (1)

[Claims] 1. In an optical gyro that detects rotational angular velocity, means is provided to flip the rotational angular velocity detection surface of the optical gyro 180 degrees and turn it over, and the zero point is detected by comparing the detected amount before and after this flipping operation. A drift correction method for an optical gyro, characterized in that it is configured to perform the following. 2. According to claim 1, the optical gyro is provided with a plurality of rotational angular velocity detection surfaces that are orthogonal to each other, and the above-mentioned turning means is provided for each of the plurality of rotational angle detection surfaces. Optical gyro drift correction method. 3. In claim 2, a rotational angular velocity signal is detected by another rotational angular velocity detection surface to which a rotational angular velocity is given by an inversion operation on one rotational angular velocity detection surface of the optical gyro. A drift correction method for an optical gyro, characterized in that the detection operation for the rotational angular velocity detection surface is calibrated by performing the following steps.