JPH0625671B2 - Inertial navigation system - Google Patents

Description

The present invention relates to an inertial navigation device, more specifically, an accelerometer for measuring the acceleration of a moving body such as an aircraft, and a gyroscope for holding the accelerometer in a correct posture. Consists of and
The present invention relates to a navigation device for confirming the position of a moving body, which comprises integrating the output of an accelerometer to obtain a moving speed, and further integrating this to obtain a moving distance.

BACKGROUND OF THE INVENTION The basis of an inertial navigation system is that an accelerometer is provided for an axis that always coincides vertically with the local area, an axis that always points north, and an axis that is orthogonal to this axis, regardless of changes in the attitude and movement of the moving body. And the input axis of the gyro are matched.

On the other hand, in the inertial navigation system, the latitude and longitude of the departure place are stored in a computer, and thereafter, the latitude change and the longitude change are calculated by this device. The calculation of these latitude and longitude is based on the earth coordinate system based on the equatorial radius and polar radius of the earth, which is an ellipsoid.

By the way, as the earth ellipsoid, there are Bessel, Clark, and the international ellipsoid defined by the International Geophysical Society and others based on the results obtained by observing the earth. In Japan, the Bessel ellipsoid is adopted, and in the map issued by Japan (GSI / issued), this is applied to the latitude and longitude. On the other hand, in Europe and other countries, the international ellipsoid is adopted.

Therefore, when a conventional inertial navigation system is used to fly by a map whose earth radius is defined by the international system, an error occurs on a map created by the Bessel system even if other errors are set to zero. That is, for example, when flying from Hokkaido to southern Kyushu, it appears as an error of about 0.15 NM in the actual map of the Bessel system.

Next, when the radius of the earth is defined by the Bessel system, the angular motion with respect to the center of the earth when the aircraft flies over the earth, that is, transport rete
From the above correction error, there is an error of about 0.1 NM when flying from Hokkaido as described above.

When flying from Japan to another country, the latitude and longitude of the initial position on the map of Japan are based on the Bessel system, and thus an error of about 0.25 NM occurs in the international land or the ocean.

In particular, regarding the actual topography, the map of the international ellipse system is more accurate than that of the Bessel system, but in the conventional inertial navigation system, it is constructed considering the international system exclusively. Therefore, when flying in Japan and its sea area, there is a disadvantage that the precise position of the moving body is not recognized in the map of Japan created by the Bessel system.

An inertial navigation system usually incorporates a Schuler loop to compensate for the gyro drift rate and the earth rotation rate error. Therefore, if the radius of the earth is calculated close to the correct value, the latitude and longitude of the moving body can be calculated from the integral of the tangential acceleration about the north-south direction of the moving body (x-axis) and the time in the east-west direction (y-axis). However, each is required with high accuracy.

However, in the map created based on the above-mentioned Bessel system, since the earth radius is greatly different from the true value, the error caused by these cannot be ignored.

[Object of the Invention] In view of the problems described above, the main object of the present invention is to avoid an error of a moving body due to a difference in the geodetic system between the Bessel system and the international system for the earth ellipsoid. To provide an inertial navigation system.

Another object of the present invention is to provide an inertial navigation system for simultaneously measuring the latitude and longitude of a moving body using both the Bessel ellipse system and the international reference ellipse system.

A further object of the present invention is to provide an inertial navigation system capable of converting the position of a moving body into the international reference system even if the position of the moving body is initially input in the earth coordinates of the Bessel system.

An object of the present invention is to provide an inertial navigation device capable of performing topographical matching using topographical data such as a map or a radar even if the geodetic system of earth coordinates is different.

[Structure of the Invention] An embodiment of the present invention will be specifically described with reference to the drawings.
The inertial navigation system comprises a gyroscope 10 and an accelerometer 12. The gyroscope 10 has three or more gyroscopes in which the input axes of the Az axis, which coincides with the vertical direction of the moving body, the N axis which always points to the north, and the E axis which is orthogonal to this, or the skew axis, are made to coincide with each other. And the motion angular velocity ω in the inertial space in these body coordinate systems can be obtained.

Similarly to the gyro 10, the accelerometer 12 is also made up of three or more elements whose input axes are aligned with each other with respect to the body coordinates of the moving body, and outputs the acceleration A.

The angular velocity ω from the gyro 10 is sent to the coordinate conversion matrix calculation unit 14. In the coordinate conversion matrix unit 14, a transport rate ωT from a transport rate calculation unit 16 described later
And the earth rotation ωe from the earth rotation angular velocity calculation unit 18, the angular velocity ω from the gyro 10 is corrected, and the coordinate conversion matrix value C is output.

The acceleration A and the coordinate transformation matrix C of the accelerometer 12 is supplied to the coordinate transformation operation part 20 of the acceleration and velocity increment [Delta] V ^N is determined for navigation axes, and sent to the integrator 22 as an output.

The output of the accelerometer 22 is an apparent velocity component of the moving body due to the rotation of the earth, that is, the Coriolis correction value ΔAc from the Coriolis acceleration calculation unit 24 for correcting the Coriolis and the gravity acceleration correction value ΔG from the gravity acceleration calculation unit 26. Are respectively sent to the integrator 22, and are calculated here to obtain the velocity V _N about the navigation coordinate axis.

The velocity V _N, which is the output of the integrator 22, is sent to the second integrator 28 and outputs the position P ^I according to the international standard ellipse system.

The above-described earth rotation angular velocity calculation unit 18 performs calculation based on the position P ^I which is the output of the second integrator 28, and the correction value ωe
Is output. Further, the angular motion of the moving body with respect to the center of the earth, that is, the transport rate, is calculated by the transport rate calculation unit 16 with the speed V _N which is the output of the first integrator 22, and the correction value ωT is obtained. In this transport rate calculation unit 16, the earth ellipsoid is converted into the international ellipsoid (equator radius: 6378388).
m, polar radius 6356912 m).

The transport rate correction value ωT is supplied to the coordinate exchange matrix calculation unit 14 together with the output ωe of the earth rotation angular velocity calculation unit 18.

A geodetic system converter 30 is provided following the second integrator 28. The geodetic system conversion unit 30 includes a Bessel-international conversion calculation unit 32 and an international-Bessel conversion unit 34.

The conversion formula for the Bessel-international conversion calculation is λ _I = λ _B + 1 / where the latitude of the Bessel formula is λ _B , the longitude is μ _B , the latitude of the international system is λ _I , and the longitude is λ _I. 60 * {a ₄ (λ _B −λ _BI ) ² + a ₃ (μ _B −μ _BI ) ² + a ₂ (λ _B
−λ _BI ) + a ₁ (μ _B −μ _BI ) + a ₀ } μ _I = μ _B + 1/60 * {b ₄ (λ _B −λ _BI ) ² + b ₃ (μ _B −μ _BI ) ² + b ₂ (λ _{B
-Λ BI) + b 1 (μ} B -μ BI) + a 0} ( where: λ _BI, μ _BI: constants a ₀ ~a _4: constants b ₀ ~b _4: be approximated by a quadratic equation constants) You can

[Advantages of the Invention] Since the structure of the inertial navigation device of the present invention is as described above in detail, the device of the present invention accurately achieves the above-mentioned object and its output is an international standard system. ,
Carry out hybrid navigation in combination with GPS as a satellite navigation system or long-range hyperbolic radio navigation that determines the position of a moving body by measuring the signal arrival time difference from at least three transmitting stations, that is, Loran C. You can

[Brief description of drawings]

The accompanying drawings are schematic block diagrams illustrating an inertial navigation system according to the present invention.

Claims (3)

[Claims] 1. A gyro that is mounted on a moving body to generate an output signal of an angular velocity of the moving body, an accelerometer mounted on the moving body to generate an output signal of an acceleration of the moving body, and an earth rotation signal. An earth rotation calculating section for outputting a transport rate signal; a transport rate calculating section for outputting a transport rate signal; the angular velocity signal; the earth rotation signal and the transport rate signal; A coordinate transformation matrix calculation unit that transforms the body coordinates of the vehicle into navigation coordinates and outputs a coordinate transformation matrix value signal, and receives the acceleration signal and the coordinate matrix value signal to change the body axis acceleration of the moving body to the navigation acceleration. An acceleration conversion calculation unit for converting, a first integrator that integrates an output signal of the acceleration conversion calculation unit, and an international standard of the mobile unit that receives an output signal of the first integrator. A second integrator that outputs a position signal according to an ellipse system, the position signal of the moving body input in the earth coordinates of the Bessel system by receiving the output signal of the second integrator into the international standard ellipse system, An inertial navigation system comprising a geodetic system conversion unit adapted to convert the position signal of the moving body input in the international standard ellipse system into a Bessel system. 2. The inertial navigation system according to claim 1, wherein a gravity acceleration correction value and a Coriolis correction value signal are input from the gravity acceleration calculation unit and the Coriolis acceleration calculation unit to the first integrator. apparatus. 3. The inertial navigation system according to claim 1, wherein the geodetic system conversion unit comprises a Bessel-international conversion calculation unit and an international-Bessel conversion calculation unit.