JPH04142088A - Rate biasing device - Google Patents

Abstract

PURPOSE:To eliminate accumulation of a scale factor error and to minimize the error of a sensor due to the motion of a navigator by multiplying the inverting period of a second rotary shaft by an integer number of the rotating period of the rotary shaft of a rotary block. CONSTITUTION:A rotary frame 8a is secured to a base member 15 through a second rotary shaft 14, and the member 15 is secured to a navigator. A frame 8 itself is supported by the shaft 14 perpendicular to a first rotary shaft 6 of a rotary shaft 6 of a rotary block 5, rotated in a predetermined direction to coordinates system of the earth at a predetermined angular velocity around the shaft 6, rotated at a predetermined angular velocity to the coordinates system of the earth around the shaft 14 to be periodically inverted in its rotating direction in such a manner that the inverting period around the shaft 14 is multiplied by an integer number of the rotating period around the shaft 6. Thus, since an abruptly inverting operation is not required, a torque motor having a large torque, a large current is eliminated to prevent generation of an error.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a late bias device for avoiding the lock-in phenomenon in a ring laser gyro device.

b. Conventional technology In a ring laser gyro, the beats of light rotating clockwise and counterclockwise in the optical path are determined, and the rotational angular velocity is determined by measuring the beat frequency with a counter.

However, when the rotation reaches the rotational angular velocity of the earth, the difference in oscillation frequency between the left and right lights becomes small, and as a result, a lock-in phenomenon occurs in which the frequency difference disappears due to a so-called entrainment phenomenon. That is, it becomes impossible to detect angular velocity in the low angular velocity region.

One of the devices to prevent this is a late bias device.

This is achieved by rotating the sensor module, which consists of a gyro and an accelerometer used in inertial navigation systems, around an axis that applies angular velocity equally to each gyro. It uses a gyro.

FIG. 6 is a perspective view of the main parts of a ring laser gyro device equipped with a late bias device according to the prior art.

Ring laser gyro 1.2, each having an input shaft 1a, 2a, 3a. An accelerometer 4 having three input axes orthogonal to the accelerometer 3 is fixed to a rotating block 5, and a rotating shaft 6 of the rotating block 5 is rotatably fixed to a frame 8 via bearings 7 at both ends. Each ring laser gyro 1.2. 3 is placed on the rotating block 5. Note that the rotating shaft 6 has a hollow structure to pass an electric circuit.

The rotation angle of the rotation block around the rotation axis 6 is detected by the angle detector 9, and the difference from the command signal from the rotation angle command transmitter 10 is determined by the subtracter 11, and the output signal of the subtractor 11 is sent to the servo amplifier. 12 and its output signal is sent to a torque motor 13. The torque motor 13 applies a torque proportional to its input current to the rotating shaft 6 of the rotating block 5. As a result, the rotation block 5 rotates according to the command signal from the rotation angle command transmitter 10.

Ring laser gyro 1.2. 3 and accelerometer 4
The output signal is taken out to the outside via the hollow part of the rotating shaft 6 and the slip ring.

FIG. 7 is a block diagram of the apparatus of FIG.

Three ring laser gyros RLGI, RLG2 . The angular velocity signal from the RLG3 is corrected for the influence of the fixed mounting angle of the ring laser gyro on the rotation block 5 by the fixed mounting angle correction converter FIXA, and is further sent to the direction cosine calculating section C05I. The direction cosine calculation unit C05I calculates the direction cosine between the coordinate axis of the rotation block 5 and the coordinates of the earth. Note that one of the coordinate axes of the rotation block 5 coincides with the rotation axis 6, and the other two axes are perpendicular to this axis and perpendicular to each other. The earth's coordinate axes are the north-south axis, east-west axis, and vertical axis at the point where the navigation vehicle is located.

A ring laser gyro detects angular velocity relative to inertial space. However, since navigational objects such as ships require positional information such as the latitude and longitude of the earth, it is necessary to input the movement of the earth relative to inertial space as a correction term or correction term.

Therefore, based on the direction cosine signal obtained in the direction cosine calculation unit C05I and the acceleration signal from the accelerometer AC5, the first coordinate conversion unit cooi converts the acceleration signal in the north-south direction, east-west direction, vertical direction, etc. with respect to the earth coordinates. Convert to acceleration component.

The acceleration component with respect to this earth coordinate is calculated by the velocity calculation unit VCA.
Coriolis correction and integral calculation are performed at L, and the signal is converted into a speed signal, which is output as a speed signal (2) and sent to the position calculation unit PCAL.

In the position calculation unit PCAL, ellipse correction and integral calculation are performed to ensure that the earth is a spheroid, and latitude and longitude are determined and output as a position signal P. These speed signals and position signals are sent to the rotation correction and damping calculation unit RO.
Sent to TD.

The rotation correction and damping calculation unit ROTD has a speedometer V.
A velocity component signal is also sent from a velocity component calculation unit VCOM which calculates a velocity component based on a signal from S, and rotation correction and the like are performed on the velocity and position.

The output of the rotation correction and damping calculation unit ROTD is sent to the correction signal calculation unit COO2, and the coordinate axes of the earth relative to the inertial space (the north-south axis, the east-west axis at the point where the navigation object is located,
vertical axis) is obtained, and this data is sent to the direction cosine calculation unit C0
Sent to 5I.

The direction cosine signal obtained by the direction cosine calculation section COS I is sent to the first coordinate transformation calculation section Cool, and is also sent to the gimbal angle correction calculation section GIMB.

The output of the angle detector 9 shown in FIG. 6 is sent to the gimbal angle correction calculation unit GIMB, and the direction cosine between the coordinate axes of the frame 8 and the coordinate axes of the earth is determined. Furthermore, based on this, the azimuth angle A2, roll angle R0, and pitch angle Pi of the navigation object are determined by the attitude angle control unit POST. The azimuth angle ^2 is sent to the velocity component calculation unit VCOM and used to calculate the velocity component.

C1 Problem to be Solved by the Invention In the late bias device according to the prior art, the torque motor 13 is used as a command signal from the rotation angle transmitter 10.
There are two methods: one in which the motor is always rotated in a fixed direction, and the other in which the direction of rotation is reversed at certain time intervals.

In the former method, each ring laser gyro L 2
．． 3 always rotates in one direction, so if there is a scale factor error in the gyro, it has the disadvantage that the error accumulates. For example, if the isometric gyroscale factor error around the axis of rotation is 1 ppm when rotating at 50 degrees per second, then for one hour, 50 degrees
@X I Xl0-b produces an error equivalent to the drift rate error of X3600.

In the latter method, each ring laser gyro 1, 2
．． Since the direction of rotation of No. 3 is reversed, accumulation of scale factor errors can be prevented, but when the direction of rotation is reversed, it must necessarily pass through a low angular velocity region where a lock-in phenomenon occurs. In order to minimize the negative effects caused by this, the reversing operation must be completed within a short period of time. For this purpose, it is necessary to apply a large torque at the time of reversal.

Therefore, if a motor is used to perform the reversal operation, a large motor and large current are required.

An object of the present invention is to propose a late bias device that constantly operates outside the low angular velocity region where the lock-in phenomenon occurs, does not accumulate scale factor errors, and minimizes sensor errors due to the movement of the vehicle. do.

60 Means for Solving the Problems The above problem is achieved by supporting the frame 8 itself of the late bias device according to the prior art with a second rotation axis perpendicular to the first rotation axis, which is the rotation axis 6 of the rotation block 5, and rotating it. Around the axis 6, it is rotated in a constant direction with respect to the earth's coordinate system at a constant angular velocity, around the second rotation axis, it is rotated at a constant angular velocity with respect to the earth's coordinate system, and the direction of rotation is periodically reversed, This problem was solved by making the reversal period around the second rotation axis an integral multiple of the rotation period around the rotation axis 6.

More specifically, there is a rotating block to which the ring laser gyro is fixed, a rotating frame that rotatably supports the rotating block, and a rotating frame that is perpendicular to the rotational axis of the rotating block and intersects with the rotational axis of the rotating block. It consists of a fixed frame that is rotatably supported around a second rotation axis, the fixed frame is fixed to the navigation object, and the rotating frame rotates with respect to the fixed frame at a constant angular velocity with respect to the earth's coordinate system. The rotation block is rotated with respect to the rotation frame body in a constant direction with respect to the earth's coordinate system at a constant angular velocity, and the reversal period of the second rotation axis is set to the rotation of the rotation axis of the rotation block. This problem was solved by a late bias device characterized by an integer multiple of the period.

d. Operation ring Since the laser gyro always rotates in a constant direction around the rotation axis of the rotating block, it does not operate in a low angular velocity region where lock-in phenomenon occurs.

Since the rotation axis of the rotation block and the second rotation axis are perpendicular to each other and intersect with each other, the angular velocities around both rotation axes are combined as a vector. As a result, due to the rotation around the second rotation axis, the direction of the rotation axis of the rotation block relative to the inertial system changes continuously and is periodically reversed. Therefore, no error occurs due to accumulation of scale factor errors. Furthermore, since the rotating block and rotating frame rotate at a constant angular velocity with respect to the earth's coordinate system, sensor errors due to the movement of the navigation object can be kept to a minimum.

f. Example FIG. 1 is a perspective view of the main part of a ring laser gyro device equipped with a late bias device according to the present invention, and FIG.
1 is a block diagram of the device shown in FIG.

Ring laser gyro of this device 1.2. 3, accelerometer 4, rotation block 5, rotation axis of rotation block 6, bearing 7, first angle detector 9, first rotation angle command transmitter 10, first subtractor 11, first servo amplifier 12
The arrangement and functions of the ring laser gyro 1.2. are shown in FIG. 6, respectively. 3. Accelerometer 4, Rotation block 5, Rotation block rotation axis 6, Bearing 7, Angle detector 9, Rotation angle command transmitter 10, Subtractor 11, Servo amplifier 12
The same reference numerals will be given and the explanation will be omitted because the arrangement and functions correspond to those of the above. Further, the portion for determining the attitude angle signal output in FIG. 2 is also the same as the corresponding portion in FIG. 7, so a description thereof will be omitted.

The rotating frame 8a corresponds to the frame 8 in the device shown in FIG. 6, but the rotating frame 8a in FIG. Fixed.

The rotation angle of the rotating frame 8a around the second rotation axis 14 is detected by a frame rotation angle detector 16, and the difference from the command signal from the frame rotation angle command transmitter 17 is detected by a second subtractor 18. The output signal of the second subtracter 18 is amplified by the second servo amplifier 19, and the output signal is sent to the frame rotating torque motor 20. The frame rotation torque motor 20 applies a torque proportional to its input current to the second rotating shaft 14 . As a result, the frame 8a rotates in accordance with the command signal from the frame rotation angle command transmitter 17.

FIG. 3 is a perspective view conceptually showing the apparatus shown in FIG. 1.

Each ring laser gyro 1.2. 3 input shaft 1a+
28+3a are orthogonal to each other and set at an angle of 54.7356° with respect to the rotation axis 6 of the rotation block.

The input axes 4a, 4b, 4c of the accelerometer 4 are orthogonal to each other, and one of them, 4a, is in the same direction as the rotation axis 6 of the rotation block.

FIG. 4 is a graph showing an example of the relationship between the rotation angle θ of the rotating block and the rotation angle θ2 of the rotating frame, and FIG. 5 is a graph showing another example of the relationship between the rotation angles θ1 and θ. be.

In this device, the rotating block always rotates in a constant direction at a constant angular velocity with respect to the earth's coordinate system around the rotation axis 6. At this time, the rotation angle θ1 around the rotation axis 6 is the fourth
It changes as shown in the upper row of each of the figures and Fig. 5.

On the other hand, the rotating frame 8a rotates at a constant angular velocity while periodically inverting around the second rotation axis with respect to the earth's coordinate system. The rotation angle θ2 around the second rotation axis 14 is the first
In this embodiment, as shown in FIG. 4, after one rotation at a constant angular velocity, the rotation is immediately reversed, another rotation is made at a constant angular velocity, and the operation of immediately reversing is repeated. Note that the period of the rotation angle θ2 around the second rotation shaft 14 is an integral multiple N of the period of the rotation angle θ around the rotation shaft 6.

In the second embodiment, as shown in FIG. 5, the motor rotates half a turn at a constant angular velocity, stops for a certain period of time, then rotates another half turn in the same direction at the same angular velocity, and after stopping for a certain period of time, the direction of rotation is reversed. . Then repeat this.

In this embodiment as well, the rotation angle θ around the second rotation axis 14
The period of 2 is an integral multiple of the period of the rotation angle θ1 around the rotation axis 6.

In this embodiment, the rotation angle θ2 around the rotation axis 14 is 18
Since it is temporarily stopped at the 0@ position and the 3606 position, it can be reversed with half the torque of the embodiment shown in FIG.

The angular velocity around the rotating axis 6 of the rotating block is zero, and the second
In order to prevent the lock-in phenomenon of the ring laser gyro, the following relationship needs to hold between the angular velocity ω2 around the rotation axis 14 of the ring laser gyro.

ω, cos (54,7356°) −ωzsin(5
4,7356°)=1 Disturbance angular velocity 1>10 Since the twin angular velocity ω21 can be made sufficiently small compared to ]ω11, the torque required to reverse the rotation around the second rotation axis 14 can be made small. can do.

Also, since the rotating block rotates around the rotation axis 6 in a constant direction with respect to the earth's coordinate system, at a constant angular velocity,
A torque sufficient to overcome the inertia caused by bearing friction and disturbance angular velocity is sufficient.

Next, regarding the problem of error accumulation, when viewed from a coordinate system fixed to the earth's coordinate system, the accumulation of angular errors due to scale factor error, installation error, and bias drift, which are errors of the ring laser gyro, is prevented.

Furthermore, since the rotating block and rotating frame rotate at a constant angular velocity with respect to the earth's coordinate system, calculation errors in the direction cosine calculation section, etc. are small, and errors due to anisotropy of the rotating block's mass and distributed moment of inertia are reduced. few.

g. Effects of the invention i) Since rapid reversal operation is not required, a torque motor with large torque and large current is not required.

ii) Since the power supply can be made smaller, the entire system can be made smaller.

ji) Since excessive inertial force accompanying the start and stop of rotation does not act on the sensor, errors can be prevented from occurring.

iv) Inversion by the added second rotation axis can prevent angle accumulation due to gyro error.

■) There is little sensor error due to the movement of the navigation object.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the main parts of a ring laser gyro device equipped with a late bias device according to the present invention, and FIG.
A block diagram of the device shown in the figure, FIG. 3 is a perspective view conceptually showing the device of FIG. 1, and FIG. 4 is a graph showing the implementation of the relationship between the rotation angle θ1 of the rotating block and the rotation angle θ2 of the rotating frame. , FIG. 5 is a graph showing another example of the relationship between rotation angles θ1 and θ2, FIG. 6 is a perspective view of the main part of a ring laser gyro device equipped with a late bias device according to the prior art, and FIG. 1 is a block diagram of the device shown in FIG. 1.2.3...Ring laser gyro, la, 2a,
3a...Input shaft, 4...Accelerometer, 5...
Rotation block, 6... Rotation axis, 8a... Rotation frame, 9... Angle detector, 10... Rotation angle command transmitter, 11... Subtractor, 12... Servo amplifier, 13...torque motor, 14...
Second rotating shaft, 15... Base member, 16...
・Frame rotation angle detector, 17... Frame rotation angle command transmitter, 18... Second subtractor, 19... Second servo amplifier, 20... Frame rotation torque motor . light

Claims (1)

[Claims] 1) A ring laser gyro is fixed to a rotating block,
A late bias device that avoids the lock-in phenomenon by rotating a rotating block includes a rotating block to which a ring laser gyro is fixed, a rotating frame that rotatably supports the rotating block, and a rotating frame that is connected to the rotating shaft of the rotating block. It consists of a fixed frame that is rotatably supported around a second rotation axis that is vertical and intersects with the rotation axis of the rotating block, and the fixed frame is fixed to the navigation vehicle, and the rotating frame is attached to the earth with respect to the fixed frame. rotate the rotating block at a constant angular velocity with respect to the coordinate system of the earth at a constant angular velocity, and rotate the rotating block with respect to the rotating frame body at a constant angular velocity in a constant direction with respect to the coordinate system of the earth, and invert the second rotation axis. A late bias device characterized in that the period is an integral multiple of the rotation period of a rotating shaft of a rotating block. 2) The rotation angle θ_2 around the second rotation axis repeats the operation of rotating 360 degrees at a constant angular velocity in one direction, immediately reversing, and rotating 360 degrees again at a constant speed. Late bias device as described in section. 3) When the rotation angle θ_2 around the second rotation axis rotates 180° in one direction at a constant angular velocity, it stops for a certain period of time, then rotates another 180° in the same direction at the same angular velocity, stops for a certain period, and then stops rotating. The late bias device according to claim 1, characterized in that the operation of reversing the direction is repeated.