JP3082097B2 - Azimuth angle measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an azimuth angle measuring device for detecting an azimuth angle of a navigating body such as a ship or an automobile.

[0002]

2. Description of the Related Art In recent years, as a system for constantly detecting the position of a navigating body such as a ship, a GP using satellite radio waves has been used.
S (Global Positioning System) navigation has been proposed. In this method, the position of a navigator is measured three-dimensionally based on data from three or more satellites at all times. In the 1990s, when satellite launch was completed, C / A, a private code, was used. It is expected to be operated using code. However, as described above, the GP
In the signal processing of S, it was only possible to measure the position of the navigation body, and it was not possible to measure the azimuth angle due to a large position measurement error. On the other hand, a two-position difference high-accuracy simultaneous measurement method that measures the phase difference of satellite radio waves, which has been used in surveying called differential GPS,
A technique for calculating the azimuth of a navigation body has been announced.

The principle of measurement will be described below with reference to FIG. In FIG. 2, 1 and 2 are, for example, ships, automobiles,
This is a receiving antenna attached to a navigating body (not shown) such as an airplane, and has a base line length L between the antennas 1 and 2.
Is known. The radio waves from the antennas 1 and 2 are supplied to the GPS azimuth calculation unit 3 and calculate the azimuth component ψ of the navigation body by the calculation described below. Now, consider a case where radio waves from one satellite 5 are received simultaneously by antennas 1 and 2 as shown in FIG. At this time,
Due to the position L of the satellite 5 and the distance L between the antennas 1 and 2, there is a distance difference between the radio wave received by the antenna 1 and the radio wave received by the antenna 2 as indicated by D in FIG. This distance difference D can be measured as a phase difference (time difference) by focusing on a specific radio wave of a carrier wave.
By multiplying this by the wavelength of the radio wave, the distance difference D
You can ask for If D is found, then L is known,

[0004]

１ = cos ^-1 (D / L)

[0005] As a result, the base line length L with respect to the observation satellite 5, that is, the azimuth componentの of the navigation body can be obtained. In this measurement, it is not always necessary to demodulate the received code.

On the other hand, the azimuth θ between the line connecting the satellite 5 and the receiving antennas 1 and 2 and true north (N) can be obtained as follows. That is, after receiving a radio wave from the satellite 5 with the antenna 1, at least two or more other satellites (not shown) are received. Then, by demodulating the C / A code of these received radio waves and obtaining the transmission time and the reception time of the radio waves transmitted from the satellite, the propagation time of the radio waves from the satellite is obtained, and the wavelength is multiplied by the wavelength of the radio waves. , The distance from the satellite to the antenna 1 and thus to the vehicle. Since the position equidistant from one satellite is on a sphere whose radius is the distance, the above-mentioned three spheres from the three satellites are obtained, and the intersection thereof is obtained.
The position of the receiving antenna 1 can be determined. If the position of the antenna 1 is determined, the position of the satellite 5 is known, and thus the azimuth θ can be determined from the direction cosine of the position vector between the antenna 1 and the satellite 5.

An element for executing a process of calculating a position from reception of a radio wave for obtaining the position of the antenna 1 is a GPS position calculation unit 4 which receives a radio wave from the antenna 1.
The GPS azimuth calculating unit 3 performs the above-described calculation of ψ and (ψ + θ) based on the position data and the reception data from the antennas 1 and 2. In this way, the base line length L calculated by the GPS azimuth calculation unit 3, and hence the azimuth of the navigation body, becomes (θ + ψ), which is output as a digital signal.

[0008]

However, such a GPS azimuth calculating device has a problem that the signal suddenly largely fluctuates due to the influence of the radio wave multipath and the propagation state of the radio wave. Therefore, there is a disadvantage that the measurement of the azimuth angle lacks reliability. An object of the present invention is to provide an azimuth angle measuring device that can cope with a change in the azimuth signal of the GPS azimuth calculation unit in view of the above problem.

[0009]

The azimuth angle measuring device of the present invention is, for example, as shown in FIG. 1, at least two satellite receiving antennas 1, 2 to be installed at a predetermined distance from a navigation body.
A first azimuth calculating unit 6a for calculating the azimuth of the navigating body based on the satellite radio waves received by the antennas 1 and 2 and the phase difference thereof, and an antenna of the antenna obtained from the satellite radio waves received from the antennas 1 and 2. A second azimuth calculating unit 6b for calculating an azimuth angle based on a change in position with time; a first and a second multiplying unit for multiplying the first azimuth calculating unit 6a and the second azimuth calculating unit 6b by a predetermined coefficient 7 and 8, an adder 9 that outputs an azimuth by adding the outputs of the first and second multipliers 7 and 8, and a coefficient controller that changes the coefficient values of the multipliers 7 and 8 depending on the situation. 11 is provided.

[0010]

According to the present invention, a first azimuth calculator 6a for obtaining an azimuth from the phase difference between the antennas 1 and 2, and a second azimuth calculator 6 for obtaining an azimuth from the time change of the positions of the antennas 1 and 2.
The azimuth is obtained by multiplying each output value by a coefficient and adding them together with b. And antenna 1,
2. Focusing on the fact that the influence of the error on the azimuth calculation unit differs depending on the azimuth calculation unit according to the reception state, radio wave propagation state, traveling state of the navigation body, etc., and control the coefficient value according to the situation. Thus, an azimuth angle suitable for a situation can be output. With such a configuration, it is possible to cope with a change in the azimuth angle of the conventional GPS azimuth calculation unit.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an azimuth angle measuring apparatus according to the present invention will be described below with reference to FIG. In FIG. 1, reference numerals 1 and 2 are receiving antennas installed at a predetermined distance from a navigation body. The received signals from the receiving antennas 1 and 2 are
Is supplied to the azimuth calculation unit 6a and the second azimuth calculation unit 6b,
Therefore, the azimuth angles φ ₁ and φ ₂ are calculated. The first azimuth calculating unit 6a is the same as the conventional GPS azimuth calculating unit,
Position of a radio wave phase difference and reception antennas 1 received by the receiving antennas 1, 2 and calculates the azimuth angle phi ₁ from the distance between the antennas 1 and 2. Then, the azimuth angle φ ₁ is multiplied by H in the multiplier 7 and sent to the adder 9. On the other hand, the second azimuth calculating unit 6b calculates the azimuth angle φ2 from the time change of the positions of the receiving antennas 1 and ₂ . Then, the azimuth angle φ ₂ is multiplied by K in the multiplier 7 and sent to the adder 9.
The calculation in the second direction calculation unit 6b will be described. The position of the receiving antenna ₁ at a certain time t ₁ is represented by P ₁ (λ ₁ , l ₁ )
(Λ ₁ : latitude, l ₁ : longitude), and the position of the receiving antenna 1 at time t ₂ after a certain time (for example, 10 seconds) has elapsed from time t ₁ is P ₂ (λ ₂ , l ₂ ) (λ _2: latitude, l _2: longitude) to. The positions of these receiving antennas are the outputs of the GPS position calculator. An azimuth φ ₂ is obtained from a change in the position of the receiving antenna 1 at times t ₁ and t ₂ . φ ₂ = tan ⁻¹ [{(l ₂ −l ₁ ) / (λ ₂ −λ ₁ )}
cosλ ₁ ] In the above description, the azimuth is determined based on the position of the receiving antenna 1, but may be determined based on the position of the receiving antenna 2. The output of the second direction calculation unit 6b may be a value based on either antenna. The adder 9 adds the outputs of the multipliers 7 and 8 and sends the result to the integrator 10. Further, the output of the integrator 10 is output as the azimuth angle φ and the subtracters 12, 1 arranged on the input sides of the multipliers 7, 8
At 3, negative feedback is provided. By configuring such a first-order lag system, a filtering effect is provided. The azimuth angle φ output from the integrator 10 is
Factor H, results in reflecting the weighted azimuth angle phi ₁ and azimuth angle phi ₂ determined by K. The coefficient controller 11 changes the coefficients H and K of the multipliers 7 and 8 according to the situation. For example, in a situation where multipath of radio waves is likely to occur,
The first azimuth angle calculation unit 6a is the second azimuth angle calculation unit 6
The output value φ ₁ is affected more than b and sudden changes in its output value φ ₁ frequently occur. In this case, it is possible to deal to reduce the weighting of phi ₁ by increasing the coefficient K from the coefficient H.

On the other hand, when a change in the refractive index of the atmosphere occurs, a change occurs in the propagation path, and the output value φ _{2 of} the second azimuth calculating unit 6b is changed.
Tends to cause more errors. In this case, by making H larger than the coefficient K, the weight of φ ₂ can be reduced to cope with it. The control of this coefficient is based on the GDOP (Geometric Dilution of
Precision) and K and H can be controlled to suitable values based on a correction term represented by a function on the carrier wave from the satellite. For example, suitable values of H and K according to the value of GDOP are stored in a look-up table, and the multiplier 7,
It can be made to act to rewrite the coefficient value of 8. Further, it is also possible to change the coefficient according to the running condition of the navigation body. For example, when the direction is frequently changed, such as in a car traveling in an urban area, an error often occurs in a method in which the second azimuth calculating unit 6b outputs the azimuth angle by a time change. On the other hand, when the direction is hardly changed as in the case of a ship navigating in the ocean, it can be expected that the second azimuth calculating unit 6b can obtain a rather stable output. The output azimuth angle φ of the system shown in FIG. 1 is represented by the following equation. φ = (φ ₁ H + φ ₂ K) / [S + (H + K)] Here, S is a Laplace operator. There are various suitable ways of giving numerical values of H and K. For example, a way of giving H + K = 1 may be used. That is, when the azimuth angle at which the error occurs is φ ₁ , H = 0, K = 1 and φ ₂
Azimuth angle alone, H = 0.2,
It is also possible to reduce the error by setting K = 0.8. H
And how K is changed depends on the multipath described above,
Judgment is made comprehensively according to the running conditions of the navigating body. If the values of the coefficients H and K can be changed in accordance with the operating condition of the navigation body, an accurate azimuth angle φ can be output. In this case, the control of the coefficient control unit 11 can be performed either automatically or manually. It is to be noted that the present invention is not limited to the above-described embodiment, and may adopt various other configurations without departing from the gist of the present invention.

[0013]

According to the present invention, the outputs of the first azimuth calculation unit and the second azimuth calculation unit are controlled in accordance with the reception state of the antenna of the navigation body, the propagation state of radio waves, the traveling state of the navigation body, and the like. By applying a suitable coefficient value, an accurate azimuth angle suitable for the situation can be output.
Therefore, it is possible to cope with a change in the azimuth angle of the conventional GPS azimuth calculation unit.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of an azimuth angle measuring device of the present invention.

FIG. 2 is a configuration diagram for explaining a principle of measuring an azimuth angle;

[Explanation of symbols]

 1, 2 Receiving antenna 6a First azimuth calculator 6b Second azimuth calculator 7,8 Multiplier 9 Adder 10 Integrator 11 Coefficient controller

Continued on the front page (72) Inventor Noriyuki Akabane 2-16-46 Minami Kamata, Ota-ku, Tokyo Inside Tokimec Co., Ltd. (72) Inventor Atsushi Kawakami 2-16-46 Minami Kamata, Ota-ku, Tokyo Co., Ltd. In Tokimec (56) References JP-A-63-29279 (JP, A) JP-A-60-244878 (JP, A) JP-A-55-117977 (JP, A) JP-A-59-88666 (JP, A) JP-A-2-296172 (JP, A) JP-A-63-6414 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01C 21/00 G01S 5/14

Claims (1)

(57) [Claims] At least two satellite receiving antennas to be installed at a predetermined distance from a navigation body, and a first azimuth angle for calculating the azimuth angle of the navigation body based on a satellite radio wave received by the antenna and a phase difference thereof. An azimuth calculating unit, a second azimuth calculating unit that calculates an azimuth angle based on a time change of the position of the antenna obtained from a satellite radio wave received from the antenna, the first azimuth calculating unit, and a second azimuth calculating unit A first and a second multiplying unit for multiplying by a predetermined coefficient, an adding unit for outputting an azimuth angle by adding outputs of the first and the second multiplying unit,
An azimuth angle measurement device comprising: a coefficient control unit that changes a coefficient value of the multiplication unit depending on a situation.