JP2009145283A - Positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of Null due to composition of received signals in GPS positioning using a plurality of antennas. <P>SOLUTION: An airframe 1 has an A antenna 2, a B antenna 3, and a C antenna 4 installed on the outer circumference thereof and connected to an A receiver 5, a B receiver 6, and a C receiver 7, respectively. The receivers output an A pseudo distance 11, a B pseudo distance 12, and a C pseudo distance 13 as observed values, respectively. These pseudo distances are used for positioning calculation by a positioning calculation device 14. It is assumed here that the position vectors of the antennas 2 to 4 can be approximated by the mean vector (e.g., the center position vector of the airframe). Then, the number of unknown parameters to be calculated by the positioning calculation device 14 is six, i.e., the total of the elements of the mean vector and the errors in time of the receivers. A result 15 of positioning is thereby obtained with use of a method of least squares if there are six or more linearly independent pseudo distances observed from the receivers 5 to 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a positioning device that performs positioning by preventing generation of nulls by combining received signals using a plurality of GPS receivers in GPS positioning of a flying object having a plurality of antennas.

  In GPS positioning on a cylindrical object such as a rocket, a GPS antenna is generally arranged on the side of the object to be positioned. Therefore, there is a possibility that GPS satellite visibility is low with one antenna and positioning cannot be performed. In order to solve this problem, a multi-antenna GPS receiver has been developed in which a plurality of antennas are arranged on the circumference of an object and a positioning calculation is performed by combining RF signals of the antennas (for example, Non-Patent Document 1). And Non-Patent Document 2).

Markgraf, M., et al., "A low cost GPS system for real-time tracking of sounding rockets", 15th ESA Symposium of European Rocket and Balloon Programs and Related Research, ESA SP-471, ISBN 92-9092-725- 9, 2001, pp. 495-502. Enderle, W., et al., "A Simple and Low Cost Two-Antennas Concept for the Tracking of a Sounding Rocket Trajectory using GPS", Proceedings of ION GPS 2000, pp. 376-383.

  However, the larger the diameter of the cylinder on which the GPS antenna is arranged, the larger the Null region generated in the antenna gain pattern by the synthesis of the received signal, and the situation where the positioning becomes impossible due to the reduced visibility of the satellite. There is a problem. Thus, in the GPS positioning using the synthetic RF wave of a plurality of GPS antennas, there is a problem regarding the visibility of the GPS satellite. Further, in order to solve this problem, if a dedicated GPS receiver that performs correlation processing and tracking processing for individual RF waves without synthesizing RF waves is created, there is a problem that the product is inevitably expensive.

  The present invention has been made in order to solve the above-described problem. By using a GPS receiver connected to each of a plurality of GPS antennas as a pair, the problem is solved, and a null region is not easily generated. It was made to realize high GPS positioning.

  The positioning device according to the present invention is mounted on a flying object, and is installed on the outer periphery of the flying object, and is connected to the receiving antenna and a plurality of receiving antennas that receive positioning information from a plurality of positioning satellites, A plurality of receivers that calculate and output a pseudorange that is a distance from the positioning satellite using the positioning information at an observation time based on a specific reference clock, and the pseudoranges are input from a plurality of the receivers, A pseudo-distance at a synchronization time at which the plurality of receivers are synchronized is calculated, and a positioning calculation unit that performs a positioning calculation based on the pseudo-distance at the synchronization time is provided.

  According to the present invention, it is possible to obtain a positioning device with high visibility by suppressing a null area of an antenna gain pattern generated by combining received signals.

Embodiment 1 FIG.
The first embodiment will be described below with reference to FIGS. A GPS (Global Positioning System) receiver (hereinafter referred to as a receiver) shown in the figure receives positioning signals (also referred to as GPS signals) from a plurality of GPS satellites, and uses GPS satellites and receivers as observation values. It is assumed that information such as a pseudo distance that is a measurement distance can be output.
A GPS satellite is an example of a positioning satellite.

FIG. 1 is a configuration diagram of a positioning device according to the first embodiment. In FIG. 1, the three antennas A antenna 2, B antenna 3, and C antenna 4 are about 120 with respect to the outer periphery of the airframe 1 when viewed from the traveling direction of the airframe 1 such as a flying object. It is installed at a degree interval. A receiver 5, B receiver 6, and C receiver 7 are connected to A antenna 2, B antenna 3, and C antenna 4, respectively.
These receivers 5 to 7 measure the pseudo distance by measuring the radio wave propagation time between the GPS satellite and the receiver and multiplying the propagation time by the speed of light. A reference signal used for measuring the radio wave propagation time is generated by a reference clock provided in each receiver. In the example of FIG. 1, each of the receivers 5 to 7 includes an A reference clock 8, a B reference clock 9, and a C reference clock 10 as reference clocks.

  Based on the received positioning signal, the A receiver 5 associates the pseudorange with a satellite number for identifying the GPS satellite, and outputs it to the positioning device 14 as the A pseudorange 11. Here, when the A receiver 5 receives positioning signals from a plurality of GPS satellites, the satellite number and its pseudorange are associated with each GPS satellite and output as an A pseudorange 11. Similarly, the B receiver 6 and the C receiver 7 output the B pseudo distance 12 and the C pseudo distance 13 as observation values, respectively. These A to C pseudoranges 11 to 13 are used for positioning calculation by the positioning calculation unit 14. The positioning calculation unit 14 outputs the result of the positioning calculation as the positioning result 15.

The reference clocks between the receivers are generally not synchronized, and the reference clocks of the receivers (A receiver 5, B receiver 6, C receiver 7) are also used in the positioning apparatus shown in FIG. (A reference clock 8, B reference clock 9, C reference clock 10) are not synchronized. For this reason, the pseudo distances (A pseudo distance 11, B pseudo distance 12, C pseudo distance 13) respectively observed and output by the A receiver 5, B receiver 6, and C receiver 7 are also observed at different observation times. Value. If the observation time of the pseudo distance is different, the positioning calculation unit 14 that calculates the position based on the A pseudo distance 11, the B pseudo distance 12, and the C pseudo distance 13 cannot calculate a highly accurate position.
Therefore, in the positioning device of the present embodiment, the pseudo-range of each receiver at the synchronous time is obtained by linear interpolation shown in Equation 1, and the positioning calculation is performed. It is assumed that the difference between the synchronization time and the observation time when the positioning signal is observed is sufficiently small.

In the example of Equation 1, t _k is the time based on the reference clock that each of the receivers 5 to 7 is mounted on its own receiver, and indicates the observation time when the pseudorange is observed at the epoch k. . On the other hand, t ′ _k indicates the synchronization time at epoch k. Normally, the receiver tries to output an observation value such as a pseudorange in synchronization with the GPS time that is the reference, but the reference clock installed in the receiver has an error in performance, so it is recognized by the receiver. In reality, there is a difference between the current time t _k and the reference time GPS time t ′ _k .
Also in the following embodiments, each receiver tries to synchronize with the GPS time. However, it is assumed that the time based on the reference clock of each receiver has a time error from the GPS time. The GPS time is referred to as a synchronization time.

In Equation 1, P _ij (t _k ) is a pseudorange between the GPS satellite (satellite number i) and the receiver (receiver number j) at the observation time t _k , and P _ij (t ′ _k ) is synchronized. The pseudo distance between the GPS satellite (satellite number i) and the receiver (number j) calculated at time t ′ _k (GPS time t ′ _k ) is shown.

FIG. 2 illustrates the relationship between the pseudo distances P _i (t _k ) and P _i (t ′ _k ) at the observation time t _k , synchronization time t ′ _k , t _k and t ′ _k used in Equation 1. It is. In the example of FIG. 2, the A receiver 5 (receiver number 1) having the A reference clock 8 receives positioning signals from two GPS satellites (satellite numbers 1 and 2), and the observation time t _k at the epoch _k. Pseudo distances P ₁₁ (t _k ) and P ₂₁ (t _k ) are output. Similarly, the B receiver 6 (receiver number 2) having the B reference clock 9 receives positioning signals from three GPS satellites (satellite numbers 3, 4, 5), and at the observation time t _k at the epoch _k . The pseudo distances P ₃₂ (t _k ), P ₄₂ (t _k ), and P ₅₂ (t _k ) are output. Further, the C receiver 7 (receiver number 3) having the C reference clock 10 receives a positioning signal from one GPS satellite (satellite number 6), and the pseudo distance P ₆₃ (at the observation time t _k of each epoch k). t _k ) is output.

Formulas 2 and 3 show the pseudo distance mathematical model. In Equation 2 and Equation 3, the GPS satellite time error τ _{s, which} the position vector (X ⁱ _S , Y ⁱ _S , Z ⁱ _S ) of the GPS satellite (satellite number i) and the reference clock of the GPS satellite (satellite number i) have _{. i} is assumed to be known from a navigation message or the like. Here, the GPS satellite time error τ _{s, i} is an error of the GPS time possessed by the GPS satellite. Therefore, in this case, the unknown parameter in each receiver (receiver number j) is the sum of each element of the receiver antenna position vector (X ⁱ _R , Y ⁱ _R , Z ⁱ _R ) and the receiver time error τ _{R, j} . There will be four. Here, the receiver time error τ _{R, j} is a GPS time error of the GPS receiver.

In equations 2 and 3, ρ _{i, j} (t ′ _k ) is the geometric distance between the GPS satellite (satellite number i) and the receiver antenna (number j) at the synchronization time t ′ _k of epoch k, and c is Speed of light, τ _{R, j} is receiver (number j) time error, τ _{S, i} is GPS satellite (number i) time error, (X ^j _R , Y ^j _R , Z ^j _R ) is receiver antenna (number j ) The position vector (X ⁱ _S , Y ⁱ _S , Z ⁱ _S ) is a GPS satellite (number i) position vector.

When the number of receivers is three, the number of unknown parameters to be obtained by the positioning calculation unit 14 is six in total, that is, each element of the receiver antenna average position vector and the receiver time error of each receiver. Therefore, if there are six or more linearly independent pseudoranges observed from each receiver (A receiver 5, B receiver 6, C receiver 7), the positioning result 15 is obtained using the least square method. Can do. In general, if the number of receivers paired with a GPS antenna is N, the least squares method can be used by acquiring (N + 3) or more GPS satellites and acquiring each pseudorange by the entire GPS antenna. The positioning result 15 can be acquired by using.

An example of an observation model that performs positioning calculation in the positioning calculation unit 14 is shown in Equation 4. Equation 4 receives positioning signals from GPS satellites with satellite numbers 1 and 2 at A antenna 2, receives positioning signals from GPS satellites with satellite numbers 3 to 5 at B antenna 3, and receives satellite signals at C antenna 4. It is an example of the observation model in the case of receiving the positioning signal from 6 GPS satellites and observing the pseudorange with each GPS satellite.
In the expression 4, l _i is the pseudo-range deviation of the satellite number _{i, (a x, a y} , a z) i is the partial differential of the position vector of the GPS satellites of the satellite number i, (x, y, z) is a receiver antenna average position vector deviation, b _j is a receiver time error (number j, distance unit), δY is a pseudorange deviation vector, H is an observation matrix, and δX is an unknown parameter vector. The average position vector of the receiver antenna means the average of the position vectors of the respective receiver antennas 2 to 4, and a specific position of the body 1 (for example, the center position of the body) can be approximated by this average position vector. Shall. The receiver antenna average position vector deviation represents the deviation.

  In the example of the observation model shown in Equation 4, when the receivers of the A receiver 5, the B receiver 6, and the C receiver 7 mounted on the flying object 1 are used for positioning alone, any receiver is used. Because the number of satellites that can receive positioning signals is less than 4 (2 satellites for A receiver 5, 3 satellites for B receiver, 1 satellite for C receiver) I can't do it.

However, by using all the pseudoranges calculated by the three receivers of the A receiver 5, the B receiver 6, and the C receiver 7, the observation model represented by Expression 4 can be obtained.
At this time, since the element vectors of the observation matrix H are linearly independent, the receiver antenna average position vector deviation (x, y, z) and the receiver time error τ _{R of} each receiver are obtained by the least square method shown in Equation 5. _{, j} can be estimated.

  The specific calculation method for estimating the receiver antenna average position vector deviation and the receiver time error of each receiver by the least square method is described in, for example, the following document (“Sophisticated GPS Basic Concept / Positioning Principle”・ Signals and receivers ”, Pratap Misra and Per Enge original work, translated by the Japan Institute of Navigation, GPS study group, p159-163, Shoyo Bunko)

The calculation by the least square method is generally performed, but the following points can be given as processing unique to the present embodiment. FIG. 3 is a diagram illustrating a calculation processing flow performed by the positioning calculation unit 14.
As described above, the reference clock (A reference clock 8, B reference clock 9, C reference clock 10) of each receiver (A receiver 5, B receiver 6, C receiver 7) of the present embodiment. Are not synchronized. For this reason, it is necessary to first estimate the receiver time error (t ′ _k −t _k ) between the receiver time of the reference clock mounted on each receiver and the GPS time. There are several methods for estimating the receiver time error τ. Here, the estimation is performed by the following method as an example.

First, at least four GPS satellites are captured by any one of the receivers mounted on the flying object, and the receiver position and the receiver time error τ are calculated. As a result, the position of the flying object and the difference (t ′ _k −t _k ) between the synchronization time t ′ _k and the observation time t _k are calculated (step S01 in FIG. 3). Other receivers mounted on the flying object can use positioning signals from at least one GPS satellite acquired at the same time as the previous receiver acquired at least four GPS satellites. Then, the receiver time error τ of the receiver is calculated (step S02). That is, since the position of the flying object, the position of at least one GPS satellite, and the pseudorange between the GPS satellite and the GPS distance are known, the receiver error τ of the receiver can be calculated by Equations 2 and 3. .
In this way, the initial value of the receiver time error of Equation 4 can be given, and the average position vector of the receiver antenna can be obtained by the calculation (step S03) that is generally performed by the least square method. (Step S04).

As described above, according to the present embodiment, in positioning of a flying object having a cylindrical shape such as a rocket, a GPS antenna is arranged on the side of the flying object, and a receiver that is paired with the GPS antenna is provided. did. In the conventional method of performing positioning calculation by synthesizing the RF signals, depending on the positional relationship between the GPS satellite and the GPS antenna, the carrier wave phase cancels out, so that a null region occurs in the antenna gain pattern. According to the embodiment, since the carrier wave is not synthesized and the observation value output from each receiver is used, the generation of a null region in the antenna gain pattern 50 can be suppressed, and GPS positioning with high visibility can be performed.
More specifically, the positioning device according to the present embodiment can suppress the generation of a null region, and the positioning calculation unit can perform positioning even when only one GPS antenna has low satellite visibility. By receiving positioning signals from more than the required number of GPS satellites by the entire receiver mounted on the flying object, the position of the flying object can be always estimated during the flight.

  In the estimation of the receiver time error, the receiver time error τ is first calculated for one receiver in the above example. However, the present invention is not limited to this method. 7 may generate a pulse signal based on the receiver time, and the positioning calculation unit 14 may calculate the receiver time error of each receiver by comparing the reception timing of the pulse signal from each receiver.

Embodiment 2. FIG.
In the first embodiment, the time variation of continuous pseudorange data is used for linear interpolation. However, if Doppler is obtained as an observed value from each receiver in addition to the pseudorange, the Doppler is converted to the pseudorange. It can be used as a time change amount.

Formula 6 is a formula for calculating the pseudo distance at the synchronization time t ′ _k . As shown in Equation 6, by using the Doppler as a time change amount of the pseudorange, the pseudorange P _ij (t ′ _k ) of the GPS satellite of the satellite number i calculated at an arbitrary synchronization time t ′ _k is calculated. be able to.

Here, λ is the wavelength of the positioning signal to be received, and D _ij is the Doppler of the signal received by the receiver (receiver number j) from the GPS satellite (satellite number i).

  As described above, in the present embodiment, a plurality of GPS antennas and a receiver paired with the GPS antennas are provided to suppress the generation of the null region. Furthermore, GPS positioning with high visibility is possible by using Doppler, and the flying object position can be always estimated during the flight.

Embodiment 3 FIG.
In Embodiments 1 and 2, three sets of antennas and receivers are used. However, the number of antennas and receivers may be reduced to two sets or increased to four or more sets according to the size and shape of the aircraft. Also good. For example, in the case of 2 sets, it is only necessary to receive 5 GPS satellites with 2 sets of receivers. When the number of antennas and receivers is 4 sets, 7 sets with 4 sets of receivers. It suffices if a single GPS satellite can be received. In general, when the number of antennas and receivers is n sets, if (n + 3) GPS satellites can be received by the n sets of receivers, the position of the target object is estimated by an observation model equivalent to Equation 4. can do.

In addition, although it is desirable to arrange | position a GPS antenna at an equal angle with respect to the flying object outer periphery, it is not restricted to an equal angle.
In addition, in Embodiments 1 and 2, a cylindrical flying body is assumed, but it can also be mounted on an airframe shaped like a general airplane in addition to a cylindrical shape. Even when flying, the position of the airplane can be continuously estimated.

Embodiment 4 FIG.
In the first to third embodiments, one receiver is provided for one antenna to synthesize a received signal. However, a synthesized RF wave obtained by combining some of the plurality of mounted receivers. If the gain characteristic of is good, a method using this synthesized RF wave is also conceivable. In the fourth embodiment, one receiver is provided for each of two antenna pairs that can complement each other's Null region and have a good gain characteristic of the synthesized RF wave via a mixer.

  FIG. 4 shows the configuration of the positioning apparatus according to the fourth embodiment. In addition, the same number is attached | subjected to the structure of a function equivalent to Embodiment 1-3, and the description is abbreviate | omitted. In FIG. 4, four antennas 16 to 19 are arranged at intervals of about 90 degrees with respect to the outer periphery of the aircraft. The D antenna 16 and the E antenna 17 are arranged at positions spaced about 180 degrees with respect to the outer circumference of the cylinder, and the F antenna 18 and the G antenna 19 are arranged at positions spaced about 180 degrees with respect to the outer circumference of the cylinder. Thus, when two antennas connected to one receiver are arranged at intervals of 180 degrees, for example, when the E antenna 17 faces the ground and the D antenna 16 faces the sky. The null area of the E antenna 17 can be complemented by the receivable area of the D antenna.

  As described above, in the fourth embodiment, a plurality of antennas are connected to one receiver via a mixer, and the plurality of antennas connected to one receiver are arranged so as to supplement each other's Null region. By doing so, positioning can be performed with a small number of receivers.

  In the fourth embodiment, an example in which four receivers are mounted has been described. However, even if the gain characteristic of a synthesized RF wave obtained by combining some of the plurality of mounted receivers is good. Needless to say, the same effect is achieved and the present invention is not limited to the four examples shown in the present embodiment.

Embodiment 5 FIG.
In the first to fourth embodiments, each independent reference clock incorporated in the receiver in advance is used. However, as shown in FIG. 5, a reference clock that is common to a plurality of receivers is provided, and this reference clock is used as the reference clock. Based on this, an observation value such as a pseudo distance may be calculated.

  In the first to fifth embodiments, the present invention has been described using GPS as an example. However, the present invention is not limited to GPS, and the present invention can be applied to other global positioning systems such as Galileo.

These are the figures which show the structure of the receiver in Embodiment 1 of this invention. These are the figures explaining the synchronous time etc. in Formula 1 in Embodiment 1 of this invention. These are the operation | movement flowcharts of the least squares method in Embodiment 1 of this invention. These are figures which show the structure of the receiver in Embodiment 4 of this invention. These are figures which show the structure of the receiver in Embodiment 5 of this invention.

Explanation of symbols

1 Aircraft (Flying Aircraft), 2 A Antenna, 3 B Antenna, 4 C Antenna, 5 A Receiver, 6 B Receiver, 7 C Receiver, 8 A Reference Clock, 9 B Reference Clock, 10 C Reference Clock, 11 A pseudorange, 12 B pseudorange, 13 C pseudorange, 14 positioning calculation unit, 15 positioning result, 16 D antenna, 17 E antenna, 18 F antenna, 19 G antenna, 20 A mixer, 21 B mixer, 50 Antenna gain pattern

Claims (5)

Mounted on the flying body,
A plurality of receiving antennas installed on the outer periphery of the flying body and receiving positioning information from a plurality of positioning satellites;
A plurality of receivers connected to the receiving antenna in a pair and calculating and outputting a pseudorange, which is a distance from the positioning satellite, using the positioning information at an observation time based on a unique reference clock;
A positioning calculation unit that inputs the pseudo distances from a plurality of the receivers, calculates a pseudo distance at a synchronization time at which the plurality of receivers are synchronized, and performs a positioning calculation based on the pseudo distance at the synchronization time;
A positioning device comprising: The positioning device according to claim 1, wherein the positioning calculation unit calculates a pseudo distance at the synchronization time by linear interpolation. The positioning device according to claim 1, wherein the positioning calculation unit calculates a pseudo distance at the synchronization time using a Doppler amount observed by the receiver as a time change amount of the pseudo distance. Mounted on the flying body,
A plurality of receiving antennas installed on the outer periphery of the flying object and receiving positioning information from a plurality of positioning satellites;
A pseudo-range, which is a distance to the positioning satellite, is calculated and output using the positioning information at the observation time based on each unique reference clock, connected to a set of receiving antennas that complement the null area of each receiving antenna. With multiple receivers,
A positioning calculation unit that inputs the pseudo distances from a plurality of the receivers, calculates the pseudo distance at a synchronization time at which the plurality of receivers are synchronized, and performs a positioning calculation based on the pseudo distance at the synchronization time;
A positioning device comprising: 5. The positioning device according to claim 4, wherein the receiving antenna that complements the null region is installed at an interval of about 180 degrees with respect to the outer periphery of the cylindrical flying body.

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