JPH063149A - Direction sensor - Google Patents

Abstract

PURPOSE:To realize high accuracy even if a relatively large gyro drift is present by providing means for starting the calculation of the azimuth in a reference direction when an input shaft of a gyroscope is agreed with the reference direction and finishing the calculation when the gyroscope is rotated an integral number of times. CONSTITUTION:The angular velocity component D due to the rotation of tame earth which is detected by a gyroscope 1 and the rotating number N set by a rotating number setting part 14 are input to a calculator part 17. An angle detector 5 has a function to output a rotating angle alpha defined by the detected direction of a reference line 9 and the direction of an input shaft 7. The output of tone rotating angle X is input to the calculator part 17. In the calculator part 17, the timing when the direction of the input, shaft, 7 of the gyroscope 1 is agreed with that, of the reference line 9 (alpha=0) is detected with the use of the rotating angle alpha, and the rotating number of the gyroscope 1 (alpha=2pin, n=1, 2, 3,psi) is calculater based on the detected timing, and moreover, arm angle defined by the direction of the reference line 9 and the direction of a due north 8, i.e., azimuth psi is calculated with the use of the rotating angle alpha and the component D. The azimuth psi is fed and displayed at a rotation display device 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an azimuth meter for detecting an angular velocity component due to rotation of the earth by a gyroscope and measuring an azimuth angle with reference to true north.

[0002]

2. Description of the Related Art An example of a conventional compass will be described with reference to FIG. One end of the rotary shaft 10 is rotatably attached to the base 6 installed horizontally so as to be vertical to it.
Further, the angle detector 5 is attached to the base 6 so as to surround the rotation shaft 10. A rotary shaft 10 is provided on the angle detector 5.
The servomotor 4 for rotating the is attached to the base 6 using the fixed support 11. A rotary table 2 is horizontally mounted on the other end of the rotary shaft 10, and a gyroscope 1 is mounted on the rotary table 2 so that its input shaft 7 is horizontal. The center of the gyroscope 1 is set to match. From the angle detector 5, the direction of the reference line 9 and the gyroscope 1
The rotation angle formed with the direction of the input shaft 7 is output and is supplied to the rotation angle indicator 12 to display the rotation angle. The angular velocity component due to the rotation of the earth detected by the gyroscope 1 is input to the servo motor drive circuit 3, and the output of the servo motor drive circuit 3 is input to the servo motor 4.
The servo motor 4 rotates the rotary table 2 (and the gyroscope 1) clockwise when a positive voltage is input, and rotates counterclockwise when a negative voltage is input, for example. . When the voltage input to the servo motor 4 is 0, the rotary table 2 does not rotate and the stationary state is maintained.

The angular velocity of the earth's rotation is Ω, the latitude of the place where this compass is installed is λ, and the input shaft 7 of the gyroscope 1 is
Let θ be the angle formed by the direction of true north 8 and θ be the proportional constant, the angular velocity component of the rotation of the earth detected and output by the gyroscope 1 is D = cΩ cos λ cos θ. This angular velocity component is amplified by the servo motor drive circuit 3 and supplied to the servo motor 4, whereby the servo motor 4 is driven, and therefore the rotary base 2 is rotated. This rotational movement becomes when the angular velocity component D detected and output by the gyroscope 1 becomes 0 (when the output voltage of the servo motor drive circuit 3 that drives the servo motor 4 becomes 0), that is, θ = 90 °. When stopped, the gyroscope 1 stops.

The angle detector 5 detects and displays the rotation angle formed by the direction of the reference line 9 and the direction of the input shaft 7. Therefore, if this angle β is measured when the gyroscope 1 is stationary, the reference The angle formed by the direction of the line 9 and the direction of the true north 8, that is, the azimuth angle of the reference line is obtained as β-90 °.

[0005]

In the conventional azimuth meter as described above, the gyroscope 1 has an error in accuracy called a gyro drift. Therefore, if this gyro drift is d, the gyroscope 1 actually detects the gyro drift. The output angular velocity component D is D = cΩcosλcosθ + d, and when the gyroscope 1 is stationary, that is, D =
The error of the angle θ (= 90 °) formed by the direction of the input shaft 7 of the gyroscope 1 and the direction of true north 8 when it becomes 0 is Δθ.
Then, D = cΩcosλcos (90 ° + Δθ) + d = 0. Therefore, Δθ is Δθ≈sin (Δθ) = d / (cΩcosλ). Since this angle error Δθ directly affects the angle β formed by the direction of the reference line 9 and the direction of the input shaft 7, it becomes a measurement error of the azimuth angle β-90 ° of the reference line.

Therefore, in the prior art, it is necessary to use a gyroscope with a small gyro drift in order to construct a highly accurate azimuth meter with a small azimuth measurement error.
However, such a gyroscope having a small gyro drift is extremely expensive, and thus the azimuth meter is also expensive. An object of the present invention is to provide an inexpensive azimuth meter that can obtain high accuracy even if a gyroscope having a relatively large gyro drift is used.

[0007]

According to the present invention, a gyroscope for detecting an angular velocity component of the earth's rotation, a rotation mechanism section for rotating an input shaft of the gyroscope at a constant angular velocity in a horizontal plane, and a rotation mechanism section thereof An angle detector that detects a rotation angle, a calculator unit that calculates an azimuth angle in a predetermined reference direction from the angular velocity component due to the rotation of the earth detected by the gyroscope and the rotation angle detected by the angle detector,
Means for starting the calculation when the input axis of the gyroscope coincides with the reference direction and ending the calculation with an integral number of rotations of the gyroscope are provided, and the azimuth angle of the reference direction is calculated.

[0008]

As described above, in the azimuth meter of the present invention, the gyroscope for detecting the angular velocity component of the earth's rotation is rotated at a constant angular velocity ω with its input shaft kept in the horizontal plane, so that the rotation of the rotation is reduced. With an angle detector that detects the angle,
.Alpha. =. Omega.t (1) is detected and output as the angle .alpha. Formed between the reference direction and the input shaft. Here, t is the time (seconds) measured from the time when the calculation starts when the input axis of the gyroscope coincides with the reference direction.

From the gyroscope, D = cΩcosλcosθ + d (2) is detected and output as the angular velocity component of the rotation of the earth, where d is the gyrodrift. Where θ is the angle between true north and the input axis, and if the angle (azimuth) between true north and the reference direction is ψ, the angle between true north and the input axis = true north and the reference direction Since there is a relation between the angle formed by + the reference direction and the angle formed by the input shaft, it can be said that θ = ψ + α = ψ + ωt using equation (1). By substituting this θ into the equation (2), D (t) = cΩcosλcos (ψ + ωt) + d (3) is obtained. Here, D (t) is used to indicate that D is a function of time.

In the calculator, the following time integration is performed using the rotation angle α = ωt of the equation (1) obtained by the angle detector and the angular velocity component D (t) of the equation (3) obtained by the gyroscope. Be seen. S = ∫D (t) cos (ωt) dt (4) The time integration section is from t = 0 to t = 2πN, where N is 1, 2, 3, ... is an integer. The setting of the time integration section is performed by "means for starting calculation when the input axis of the gyroscope coincides with the reference direction and ending the calculation with an integral number of rotations of the gyroscope". By substituting the equation (3) into the equation (4) and performing the calculation, S = (cΩcosλcosψ × Nπ) / ω is obtained. Therefore, the calculated azimuth angle ψ is calculated as ψ = arccos {Sω / (cΩcosλ × Nπ)} (5).

What is important here is that the gyro drift d is not included in the equation (5). The reason is that the next time integration becomes 0 in the time integration section t = 0 to t = 2πN. That is, ∫d × cos (ωt) dt = 0 In this way, the gyroscope is rotated an integral number of times in the horizontal plane to calculate the formula (4), and based on the result, the azimuth is calculated using the formula (5). By calculating the angle, the error due to gyro drift can be removed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will now be described with reference to the drawings. An azimuth meter according to the present invention is shown in FIG. 1, and corresponding parts in FIG. 2 are designated by the same reference numerals. In order to avoid duplication, only the part different from the conventional compass shown in FIG. 2 will be described. The rotation mechanism unit 13 is attached to the base 6 by using the fixed support 11. The rotation mechanism unit 13 is arranged so as to surround the rotation shaft 10, and the rotation shaft 10, the rotation base 2 attached to the rotation shaft 10, and the rotation thereof. The rotation of the gyroscope 1 installed on the table 2 in a horizontal plane is driven. The actual rotation mode, that is, the rotation angular velocity and the stop signal are generated by the rotation mechanism control unit 16, and the rotation mechanism unit 13 drives the rotation shaft 10 based on this information. The modes of rotation include rotation and stop at a constant angular velocity ω.

The angular velocity component D (t) due to the rotation of the earth detected by the gyroscope 8 and the rotation speed N set by the rotation speed setting unit 14 are input to the calculator unit 17. The angle detector 5 is provided with a function of outputting a rotation angle α formed by the detected direction of the reference line 9 and the direction of the input shaft 7, and the rotation angle output α is input to the calculator unit 17. This calculator section 1
7, the timing (α = 0) at which the direction of the input shaft 7 of the gyroscope 1 and the direction of the reference line 9 match is detected using the rotation angle α, and the rotation speed of the gyroscope 1 from this timing (α = 0) α = 2πn, n = 1, 2, 3, ...
..) is calculated, and the rotation angle α and the angular velocity component D (t) are calculated.
The angle between the direction of the reference line 9 and the direction of true north 8 using
That is, the azimuth angle ψ is calculated. This azimuth angle ψ is supplied to and displayed on the rotation angle indicator 12.

The above is the basic configuration of the compass according to the present invention and the function of each component. Next, the overall operation will be described. It is assumed that the gyroscope 1 is stationary under the command of the rotation mechanism control unit 16. First, the rotation mechanism control unit 16 provides the rotation mechanism unit 13 with information on each constant speed ω and a rotation command. By the rotation mechanism unit 13,
Based on this information and the rotation command, the rotary shaft 10, the rotary base 2 attached to the rotary shaft 10, and the gyroscope 1 are rotated. Since it takes some time for the rotation to stabilize and to obtain the constant angular velocity ω, the operation start signal from the operation start control unit 15 is sent to the calculator unit 17 after waiting for this time.
The calculator 17 has a set rotational speed N and an angular velocity component D.
(T) and the rotation angle α are input, and when the first integer n that satisfies α = 2πn is detected after the operation start signal is received, the rotation angle α is reset with α = 0 and the calculation is started. To do. The timing of the end of this calculation is the calculator unit 17
Is performed by monitoring the rotation angle α input to
It ends with πN. As a result, the angle formed by the direction of the reference line 9 and the direction of the true north 8, that is, the azimuth angle ψ is calculated by the calculator unit 17 and output. After the calculation is completed, the rotation mechanism control unit 16
Under this command, the rotation of the gyroscope 1 is stopped.

Further, it is clear that the azimuth angle ψ can be calculated even if the gyroscope 1 is always rotated at a constant angular velocity ω without stopping. To repeat, the calculation procedure of the azimuth angle ψ performed by the calculator unit 17 first uses S = ∫D (t) cos (ωt) by using the rotation angle α = ωt and the angular velocity component D (t). dt is calculated, and as a result, S = (cΩcosλcosψ × Nπ) / ω is obtained. Finally, when the azimuth angle ψ is calculated using this formula, ψ = arccos {Sω / (cΩcosλ × Nπ)}.

The function of generating the calculation start signal of the calculation start control unit 15 can also be performed inside the calculator unit 17.
To this end, the number of revolutions until the rotary table 2 obtains stable rotation is set in the calculator unit 17, and when the number of revolutions detected by the calculator unit 17 from the rotation angle α becomes equal to the set value. May be used as the calculation start timing.

[0017]

According to the azimuth meter of the present invention, a gyroscope for detecting the angular velocity component of the earth's rotation, a rotation mechanism section for rotating the input shaft of the gyroscope at a constant angular velocity in the horizontal plane, and its rotation. An angle detector that detects the rotation angle of the gyroscope, a calculator that calculates the azimuth angle of the predetermined reference direction from the angular velocity component due to the rotation of the earth detected by the gyroscope and the rotation angle detected by the angle detector, and the gyroscope. Means for starting the calculation when the input axis of the scope coincides with the reference direction and ending the calculation for an integral number of rotations of the gyroscope are provided, and the azimuth angle of the reference direction is calculated. Therefore, if the azimuth angle is calculated by rotating the gyroscope an integral number of times, the error due to the gyrodrift that is unique to the gyroscope can be offset, and even if a gyroscope with a relatively large gyrodrift is used, the azimuth angle is high and the azimuth is inexpensive. The total is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of an azimuth meter according to the present invention.

FIG. 2 is a perspective view of a conventional compass.

Claims (1)

[Claims] 1. A gyroscope that detects an angular velocity component of the earth's rotation, a rotation mechanism unit that rotates an input shaft of the gyroscope at a constant angular velocity in a horizontal plane, and an angle detector that detects a rotation angle of the rotation. And a calculator unit that calculates an azimuth angle of a predetermined reference direction from the angular velocity component due to the rotation of the earth detected by the gyroscope and the rotation angle detected by the angle detector, and the input axis is the reference direction. An azimuth meter comprising means for starting the calculation when they match and ending the calculation for an integral number of rotations.