JP2001059863A - Azimuth measuring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform highly accurate azimuth measuring even in the case that the number of receivable satellites for positioning is few, and that radio waves from a few satellites are received with multipath in the case of performing kinematic positioning on the relative location of two GPS antennas on a moving body and obtaining the direction of the moving body. SOLUTION: In this device, a reference antenna A and measuring antenna B are arranged at a predetermined interval. The coefficient of change of a double-phase difference or single-phase difference in a unit of azimuth change in the measuring antenna B to the reference antenna A is obtained by computations, the amount of the azimuth change in the measuring antenna B to the reference antenna A is obtained from the observed double-phase difference or observed single-phase difference, and the coefficient of change is obtained and added to the previous direction to obtain the present azimuth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a mobile communication system
The present invention relates to an apparatus for receiving a radio wave transmitted from a positioning satellite such as an S satellite and measuring the direction of a moving object.

[0002]

2. Description of the Related Art Heretofore, a work boat for performing dredging work, for example, on a bay shore or offshore, has been provided with a device for measuring the position of the bucket in order to lower the bucket to an accurate predetermined position and perform dredging.

FIG. 1 shows the construction of a work boat for performing dredging work. FIG. 1A is a plan view, and FIG. 1B is a side view. As shown in the figure, the bucket is suspended from the tip of the boom (arm), and the boom (horizontal plane rotation and vertical plane rotation) within a predetermined range in a state where the work boat is fixed. Moves the bucket up and down.

Conventionally, the heading θh is detected by a gyro compass, the angle θb of the boom in the horizontal plane direction and the angle φb of the boom in the vertical direction are each detected by a rotary encoder, and the position of the work boat (hereinafter referred to as “ship position”) is detected. ) Is measured, and the position of the bucket in the horizontal plane is calculated based on the ship position, the heading θh, the angle θb of the boom in the horizontal plane direction, and the angle φb of the boom in the vertical plane, and this is displayed to the operator. The vertical position of the bucket is also detected and displayed by another means.

[0005]

As a positioning device for obtaining the above-mentioned ship position information, a GPS positioning device is generally used, and a receiving antenna thereof is provided at a predetermined position on a work boat. In the above-described method of detecting the work position (bucket position), the work position is obtained indirectly by transposing the position of the antenna of the positioning device by the direction and the distance. Therefore, the detection accuracy of the work position is determined by the angle detection accuracy of the rotary encoder and the heading measurement accuracy of the gyro compass in addition to the positioning accuracy of the positioning device.
Of these, the angle detection accuracy of the rotary encoder can be easily increased, so that the heading detection accuracy occupies a large weight.

For this purpose, the heading is conventionally detected by using a gyro compass, but the handling is not always simple. That is, the maintenance cost due to overhaul is required every several months to one year, so that the running cost increases, and the time from when the power supply is cut off to when the azimuth measurement can be actually performed (settling time) is usually as long as about 4 hours. Was required. If a magnetic compass or an electronic magnetic compass using a flux gate sensor is used, such a problem does not occur, but its azimuth measurement accuracy is low. Generally, the azimuth measurement accuracy of the gyro compass is ± 0.5 °, whereas the magnetic compass, for example, is approximately ± 1 °. For this reason, when a magnetic compass is used, the accuracy of measurement of the heading direction is reduced, and the accuracy of detecting the work position is greatly reduced.

If a GPS antenna is provided at the end of the boom, the position of the bucket can be obtained directly by GPS positioning. However, the vibration accompanying the work is very large, and the length of the boom reaches several tens of meters. And the cable length from the antenna to the receiver becomes too long.

[0008] Therefore, it is conceivable to provide two GPS antennas on the moving body, determine their relative positions by kinematic positioning, and determine the azimuth of the moving body from the relative positions.

[0009] However, in order to perform kinematic positioning, radio waves from four or more satellites must be received at all times, and the temporal and spatial restrictions on which azimuth can be measured are great. Not necessarily.

[0010] Further, even in a state where radio waves from four or more satellites can be received, there is a problem that the accuracy of azimuth measurement is reduced when receiving multipath. That is, in kinematic positioning, since the dual phase difference is used, it is not possible to individually determine which satellite receives a signal from the multipath. It is impossible to use.

An object of the present invention is to provide high-accuracy azimuth measurement even when the number of receivable positioning satellites is small and when radio waves from several satellites are received with multipath. To provide an azimuth measuring device capable of performing the following.

[0012]

According to the present invention, an observation double phase difference of a carrier phase is obtained by a reference antenna and a measurement antenna provided at a predetermined position on a moving body, and a relative position of the measurement antenna with respect to the reference antenna is obtained. . In addition, the change coefficient of the double phase difference per unit change of the direction of the measurement antenna with respect to the reference antenna is obtained by calculation, and from this change coefficient and the observed double phase difference, the direction change amount of the measurement antenna with respect to the reference antenna is obtained. Then, the azimuth of the moving object is obtained by integrating the azimuth change amount.

For example, in the case of the work boat shown in FIG.
GPS antennas are provided in advance at the positions indicated by. In this example, the straight line connecting the two GPS antennas coincides with the bow line.

FIG. 4 shows the positional relationship between the two antennas and 2
Position lines based on the observed double phase difference at the positions of two antennas (a plurality of hyperboloids corresponding to those obtained by setting the fractional part to the observed double phase difference and the integer part to several candidate values as lines on a two-dimensional plane) (Shown). When there are four satellites, three sets of position lines are obtained in this way, and among these grid points, a true grid point obtained by determining an integer part is determined by the antenna B with respect to the antenna A. It is obtained as a relative position. Thereafter, if the number of satellites becomes two and the relationship shown in FIG. 5B is obtained, the change coefficient α of the double phase difference per unit change in the direction of the antenna B with respect to the antenna A is calculated. From the change amount of the observed double phase difference and the change coefficient α, the azimuth change amount φ of the antenna B with respect to the antenna A is obtained. Then, the current azimuth is obtained by integrating the azimuth change amount with the azimuth before the change.

In the above-described example, the azimuth is measured based on the double phase difference. In the second aspect of the invention, the radio waves received by the reference antenna and the radio wave received by the measurement antenna are respectively received. While synchronizing the reference clock signals of the reference antenna receiver and the measurement antenna receiver, the change coefficient of the single phase difference per unit change of the azimuth of the measurement antenna with respect to the reference antenna is calculated, and the observed single phase difference and the change coefficient are calculated. Then, the azimuth change amount of the measurement antenna with respect to the reference antenna is obtained, and the azimuth of the moving object is obtained by integrating the azimuth change amount. That is, as shown in FIG. 5A, the relative position of the antenna B with respect to the antenna A changes from B to B ′ by changing the azimuth.
Although the single phase difference changes from L to L ', this antenna A
, A change coefficient α of a single phase difference per unit change of the azimuth of the antenna B is calculated in advance, and the azimuth change φ of the antenna B with respect to the antenna A is obtained from the observed single phase difference and the coefficient α. The current azimuth is obtained by integrating the azimuth.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an azimuth measuring apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an example of mounting positions of two antennas in a work boat (spud type glove dredger). (A) is a plan view,
(B) is a side view. In this example, two antennas A and B are provided on the bow line of the work boat at a predetermined distance La.

FIG. 2 is a block diagram showing the configuration of the entire device for detecting a working position using the azimuth measuring device of the present invention. In FIG. 2, two rotary encoders detect an angle θb of the boom in the horizontal plane direction and an angle φb of the boom in the vertical plane direction, respectively. The positioning device measures the position of the ship.
The work position detection device calculates the position of the bucket in the horizontal plane based on the ship position, the heading θh, the angle θb of the boom in the horizontal plane direction, and the angle φb of the boom in the vertical plane, and displays this to the operator. The vertical position of the bucket is also detected and displayed by another means.

FIG. 3 is a block diagram showing the configuration of the azimuth measuring device shown in FIG. In FIG. 3, A is a reference antenna, and B is a measurement antenna. The receiver connected to the reference antenna A is a reference antenna receiver and the measurement antenna B
Is a measurement antenna receiver.

The receiving circuits 11 and 21 amplify the signal received from the antenna and convert it to an intermediate frequency signal. The AD converters 12 and 22 sample the received signal and convert it into digital data. Digital signal processing circuit 1
Numerals 3 and 23 perform arithmetic processing on the digital data strings converted by the AD converters 12 and 22. Specifically, the input data sequence is multiplied by the C / A code to remove the C / A code component, and the carrier N
An I correlation value and a Q correlation value are obtained by integrating the result of multiplying the I signal and the Q signal generated by the CO.
In addition, C / C shifted by ± 0.5 chip from the input data string
The correlation with the A code is obtained, and the difference is obtained as an EL correlation value.

Processors 14 and 24 are CPU, RO
M, RAM, etc., detecting the carrier phase of the received signal from the I correlation value and the Q correlation value, detecting the phase of the C / A code included in the received signal from the EL correlation value, The tracking of the carrier phase and the C / A code phase is performed. The carrier phase is actually detected not from the phase of the carrier frequency of the radio wave transmitted from the GPS satellite but from the signal converted into the intermediate frequency signal, but the phase information of the intermediate frequency signal is determined by the GPS satellite and the receiving point. Since the information on the distance from the GPS satellite is stored as it is, this is equivalent to detecting the phase of the carrier frequency of the radio wave transmitted from the GPS satellite.

The processor 24 outputs the data of the carrier phase of each satellite at the position of the measurement antenna B via the interface 25, and the processor 14 receives the data via the interface 15. Further, the processor 14 obtains the observed single phase difference at the position of the measurement antenna. In addition, the processor 14 performs the following procedure.
The azimuth change amount of the measurement antenna with respect to the reference antenna is obtained, and the change amount is added to the azimuth before the change to obtain the azimuth of the measurement antenna with respect to the current reference antenna. Output via The oscillator 10 includes receiving circuits 11 and
1 is given a local oscillation signal for frequency conversion,
A reference clock signal is supplied to the AD converters 12 and 12 and the digital signal processing circuits 13 and 23. The frequency dividers 17 and 27 divide the frequency of the reference clock signal to provide a clock signal to the processors 14 and 24.

FIG. 6 is a flowchart showing a processing procedure of the azimuth measuring device. First, OTF (On The Fly cal
In the (ibration) process, if the number of satellites currently being tracked is equal to or greater than the number (four) for which an integer bias can be determined, an observation single phase difference is obtained for each satellite. Then, the integer bias of these observed single phase differences is determined. this is,
This corresponds to determining a true solution among points (three-dimensional grid points) formed by intersecting multiple spheres centered on the satellite position. For example, even if the satellite constellation changes with the passage of time, a point at which a constant integer value bias is obtained regardless of the change is determined as a true solution (integer value bias).

The relative position of the measurement antenna B with respect to the reference antenna A is obtained by the OTF with an accuracy of, for example, about ± 1 cm, which is equal to the resolution of the carrier phase.

When the number of receivable satellites decreases and kinematic positioning cannot be performed, the azimuth measurement processing in FIG. 6 is performed. First, for each receivable satellite, the difference in carrier phase from the previous time (one second before) is determined. Here, the satellite number is SV1, the change amount of the carrier phase by the reference antenna A per second is θ _A ^SV1 , the measurement antenna B
The amount of change per second of the carrier phase as theta _B ^SV1 in, obtains the difference ^{_{(θ A SV1 -θ B SV1)}} . When the azimuth of the measurement antenna B with respect to the reference antenna A changes by a unit amount (for example, 1 degree), the above (θ _A ^SV1 −θ _B
^SV1 ) is calculated by calculating a coefficient ^αSV1 of how much the value changes. This is obtained from the relationship between the positions of the two antennas A and B and the satellite (position taking into account the movement of the satellite for one second). In the example shown in FIG. 5A, when the relative position of the antenna B with respect to the antenna A moves from B to B ′, the difference in carrier phase (θ _A −θ _B ) is caused by the change of the distance L′−L. Is changed by the phase difference corresponding to. In FIG. 5B, although a two-dimensional plane is drawn for convenience of illustration on paper, it is actually handled as three-dimensional information.

Then, φ = (θ _A ^SV1 −θ _B ^SV1 ) / α
The azimuth change amount φ per second is obtained by ^SV1 .
For example, (θ _A ^SV1 −θ _B ^SV1 ) = 1.6 [cycles]
If α is 3.2 [cycles / degree], it means that the heading has changed by 0.5 degrees per second. Accordingly, a new current azimuth Φ is obtained by integrating the change amount Φ with the azimuth Φ obtained last time. Then, Φ is output as the heading.

In the example described above, if the number of receivable satellites is one, φ obtained for that satellite is treated as the azimuth change amount, but the number of receivable satellites is two.
If there are three or three, the azimuth change amount φ per second is obtained using each satellite, and the average value thereof is treated as the azimuth change amount. However, since the above α greatly varies depending on the positional relationship between the two antennas A and B and the satellite,
In order to obtain higher accuracy, the azimuth change amount φ obtained by using each satellite is weighted average. In other words, the more the α is the azimuth change amount obtained by a satellite having a large positional relationship, the greater the weight is and the weighted averaging is performed, whereby the measurement accuracy of the azimuth change amount is improved.

When φ is determined for each of the three satellites, the satellites showing an abnormal value among them are regarded as having received multipath radio waves from the satellites, and their data are determined. And a weighted average is calculated for the remaining two azimuth changes φ. As a result, the influence of multipath can be avoided and the azimuth measurement accuracy can be maintained high.

In the example described above, a single
The phase difference was calculated, and the azimuth change was calculated based on the phase difference.
However, the oscillator 10 shown in FIG.
If they are independent for each receiver,
That is, the two receivers operate under separate reference clocks.
The phase difference based on the signals from the two satellites
To obtain the azimuth change amount from the change amount.
You may. In this case, two satellites S at antenna A
1 of the single phase difference of the carrier phase for V1 and SV0
Change amount per second (θ^SV1 −θ^SV0 )_A And antenna B
Phase for two satellites SV1 and SV0
Of the single phase difference for one second (θ^SV1 −θ^SV0 )_B When
Ask for. And the direction of antenna B with respect to antenna A
Is changed by a unit amount (for example, 1 degree).^SV1 
−θ^SV0 )_A And (θ^SV1 −θ^SV0 ) _B The difference between
Coefficient of change α^SV1-SV0 Is obtained by calculation. this
Is two satellites SV1, SV0 and two antennas
From the positional relationship between A and B,
Determined taking into account the movement of the stars. And the bearing by the following formula
Is obtained.

Φ = ｛(θ ^SV1 −θ ^SV0 ) _A − (θ ^SV1 −
θ ^SV0 ) _B ｝ / α ^SV1-SV0 As described above, even when the azimuth change amount is obtained based on the double phase difference, φ is more weighted by using two satellites having a positional relationship in which α becomes larger. And weighted average. This improves the measurement accuracy of the azimuth change.

Now, as shown in FIG. 6, the number of satellites is RT
When the number returns to a number that allows K (Real Time Kinematic) positioning, the positions of the two antennas are measured relative to each other by RTK positioning to determine the heading, and the heading is output.

The positioning device shown in FIG. 2 may be provided independently of the azimuth measuring device, but an RTK is provided between the reference antenna receiver and a reference station provided at a fixed position such as land.
Positioning may be performed. That is, the reference antenna receiver receives the carrier phase data of each satellite from the reference station, obtains the observed double phase difference of the carrier phase between the reference station and the reference antenna receiver, and determines an integer bias by OTF. Thus, the relative position of the reference antenna with respect to the position of the reference station may be obtained and output as the ship position data. With this configuration, a dedicated receiver for finding the position of the ship is not required, and it is possible to avoid an increase in the size of the system.

Next, the configuration of an azimuth measuring apparatus according to a second embodiment will be described with reference to FIGS. In the first embodiment, two antennas A and B are used for relative positioning with a base line between them. However, when only one satellite is required to obtain a single phase difference, If only two satellites are used to determine the distance, the measurement accuracy of the azimuth change amount decreases due to the positional relationship between the satellite and the two antennas. For example, when a single phase difference is obtained, as shown in FIG. 7A, the measurement antenna is located at the position B ′, and the baseline connecting the reference antenna A and the measurement antenna B ′ is:
When there is a relationship along an arc centered on the position of the satellite, the above α is the largest and the azimuth measurement accuracy is the highest,
When the measurement antenna is located at the position B and the satellite exists in a vertical plane including the base line connecting the reference antenna A and the measurement antenna B, the above α becomes the smallest and the measurement accuracy of the azimuth change amount becomes the lowest. Become.

Also, when the azimuth change amount is determined based on the double phase difference, as shown in FIG. When the baseline connecting the antenna B 'is parallel to the position line generated by the double phase difference, α becomes the largest and the azimuth measurement accuracy is the highest, but the measurement antenna is located at the position B and the reference When the base line connecting the antenna A and the measurement antenna B is in a direction perpendicular to the position line, α is the smallest, and the measurement accuracy of the azimuth change amount is the lowest.

Therefore, as shown in FIG. 8A, using the reference antenna A and the two measurement antennas B and C, the base line by the antennas AB and the base line by the antennas AC have a vertical relationship. Next, the positional relationship between the three antennas is determined. Then, azimuth measurement is performed using the base line with the higher azimuth measurement accuracy. Alternatively, instead of switching the base line depending on the case as described above, the azimuth change amounts obtained by both base lines are weighted average so that the measurement accuracy of the azimuth change amount is increased. That is, the larger the value of α is, the greater the weight is and the weighted averaging is performed. Note that the angle formed by the two base lines is not limited to a vertical angle, and may have another angle relationship such as 60 degrees as shown in FIG. 8B.

FIG. 9 is a flowchart showing a procedure for calculating the azimuth change amount φ when the above three antennas are used.
First, using the reference antenna A and the measurement antenna B, the azimuth change φb is obtained in the same manner as in the method described in the first embodiment. At the same time, the azimuth change amount φc is obtained using the reference antenna A and the measurement antenna C. And weight w for φb,
A weight (1-w) is given to φc, and a weighted average is given. This weight w is determined by the positional relationship between the two antennas and the satellite. For example, in the state shown in FIGS. 7A and 7B, w = 0 when the measurement antenna is at the position B, and W = 1.0 when the measurement antenna is at the position B ′.

In the present invention, it is a condition that the direct distance of the base line (base line) between the reference antenna and the measurement antenna is kept constant and horizontal. this is,
If the perpendicular distance of the baseline changes, the difference in carrier phase changes accordingly.If the height of the reference antenna and the measurement antenna changes, the carrier phase also changes, and the measurement of the azimuth change amount is erroneous. Because it will be. However, there is an allowable range depending on the required azimuth measurement accuracy, and a change in the direct distance of the base line and a change in the height of the reference antenna and the measurement antenna may be within the allowable range.

When the ship is rolling without being fixed to the seabed by the spud, the result of the direction measurement is time-averaged by utilizing the characteristic that the angle formed by the base line with respect to the horizontal plane changes periodically. By doing so, the azimuth change amount when the base line is in the horizontal plane may be obtained.
Alternatively, the inclination of the ship may be observed, the carrier phase data may be obtained at a timing when the base line overlaps the horizontal plane, and the azimuth change amount may be obtained from the difference by the method described above.

[0038]

According to the first, second and third aspects of the present invention, even when the number of receivable positioning satellites is small and kinematic positioning is not possible, the azimuth of the moving object can be measured. There are almost no restrictions in time and space in which the direction can be measured, and the utilization efficiency of the device is improved.

According to the second aspect of the present invention, even when radio waves from several satellites are received with multipaths, signals with the multipaths can be distinguished. Higher accuracy azimuth measurement can be performed using only a signal without a path.

According to the third aspect of the invention, it is possible to always prevent the azimuth measurement accuracy from being lowered regardless of the positional relationship between the reference antenna, the measurement antenna, and the positioning satellite.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a configuration of a work boat and mounting positions of two antennas.

FIG. 2 is a block diagram showing an overall configuration of a device for detecting a work position using the azimuth measuring device according to the embodiment;

FIG. 3 is a block diagram showing a configuration of an azimuth measuring device.

FIG. 4 is a diagram showing a relationship between a position line based on a double phase difference and positions of two antennas.

FIG. 5 is a diagram showing an example of a change in azimuth of an antenna B with respect to an antenna A and a change in a carrier phase difference;

FIG. 6 is a flowchart showing a processing procedure of the azimuth measuring device.

FIG. 7 is a diagram showing a relationship of azimuth measurement accuracy based on a positional relationship between two antennas and a satellite.

FIG. 8 is a diagram showing an example of an antenna arrangement of an azimuth measuring device using three antennas according to the second embodiment;

FIG. 9 is a flowchart showing a processing procedure of the azimuth measuring device according to the second embodiment.

[Explanation of symbols]

 A-Reference antenna and its position B-Measurement antenna and its position C-Measurement antenna and its position

Claims (3)

[Claims] 1. A reference antenna and a measurement antenna provided at predetermined positions on a moving body receive radio waves from a plurality of positioning satellites, respectively, and observe carrier phases at the positions of the reference antenna and the measurement antenna. Means for determining the relative position of the measurement antenna with respect to the reference antenna by determining the phase difference; and radio waves from two predetermined positioning satellites at the positions of the reference antenna and the measurement antenna per unit change of the azimuth of the measurement antenna with respect to the reference antenna. The change coefficient of the double phase difference is obtained by calculation, and the azimuth change amount of the measurement antenna with respect to the reference antenna is obtained from the double phase difference observed by the radio waves from the two positioning satellites and the change coefficient.
Means for determining the azimuth of the moving object by integrating the azimuth change amount. 2. A reference antenna and a measurement antenna provided at a predetermined position on a mobile body respectively receive radio waves from a plurality of positioning satellites, and observe a single phase difference of a carrier phase at the positions of the reference antenna and the measurement antenna. Means for determining the relative position of the measurement antenna with respect to the reference antenna, and synchronizing the reference clock signals of the reference antenna and the measurement antenna receiver, which receive the radio waves received by the reference antenna and the measurement antenna, respectively. The change coefficient of the single phase difference due to the radio wave from the predetermined positioning satellite at the position of the reference antenna and the measurement antenna per unit change of the azimuth of the measurement antenna is calculated, and the single observation by the radio wave from the predetermined positioning satellite is calculated. From the phase difference and the change coefficient, the orientation of the measurement antenna with respect to the reference antenna Volume of the seek, direction measuring device characterized by comprising a means for determining the orientation of the moving object by integrating the said level change amount. 3. The apparatus according to claim 1, wherein a plurality of the measurement antennas are provided, and respective base lines connecting the reference antenna and the measurement antennas do not overlap with each other.
Or the azimuth measuring device according to 2.