JP2023155130A - Method and dev for detecting abnormality of received signal - Google Patents

Abstract

To detect the abnormality of a received signal including abnormality in the arrival direction of the received signal in a GNSS.SOLUTION: The present invention receives GNSS signals transmitted from a plurality of GNSS satellites S_i via a plurality of GNSS antennas 3A, 3B, 3C and determines whether the transmitted time of the GNSS signals is normal or not, on the basis of the comparison of the transmitted time of the GNSS signals included in the GNSS signals with a reference transmit time, and determines whether the pseudo-distance ρ_i of the GNSS satellites S_i is normal or not, on the basis of the comparison of the pseudo-distance ρ_i of the GNSS satellites S_i having transmitted the GNSS signals with the pseudo-distance ρr of a prescribed reference satellite Sr, as well as determines whether the arrival direction of the GNSS signals is normal or not, on the basis of an index that indicates a difference in course from the GNSS satellites S_i having transmitted the GNSS signals to each of the plurality of GNSS antennas 3A, 3B, 3C.SELECTED DRAWING: Figure 1

Description

The present invention relates to a technique for detecting abnormalities in received signals in GNSS (Global Navigation Satellite System).

BACKGROUND ART Devices that measure the position of a moving object using an inertial navigation device and a GNSS positioning system are conventionally known (see Patent Document 1). In addition, as a technology for detecting anomalies in received signals in GNSS, it is possible to detect whether or not received signals from GPS (Global Positioning System, Global Positioning Satellite) satellites are affected by multipath. There is a known device for determining (see Patent Document 2). Further, a device is known that detects spoofing after satellite positioning by GNSS is interrupted (see Patent Document 3).

Patent No. 4803862 Japanese Patent Application Publication No. 2010-256301 Japanese Patent Application Publication No. 2020-134350

The device of Patent Document 2 determines whether the received signal from each GPS satellite is a signal affected by multipath based on the phase difference of the received signal from each GPS satellite, It is not determined whether the direction of arrival of the received signal from each GPS satellite is abnormal.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method and apparatus for detecting an abnormality in a received signal, which can detect an abnormality in a received signal including an abnormality in the direction of arrival of a received signal in GNSS.

In order to solve the above problems, a method for detecting an abnormality in a received signal according to the present invention receives GNSS signals transmitted from a plurality of satellites via a plurality of antennas, and detects the abnormality contained in the GNSS signal. It is determined whether the transmission time of the GNSS signal is normal based on a comparison between the transmission time of the GNSS signal and a predetermined reference transmission time, and each of the plurality of antennas is determined from the satellite that transmitted the GNSS signal. It is characterized in that it is determined whether or not the direction of arrival of the GNSS signal is normal based on a path difference index representing a difference in path up to.

The method for detecting an abnormality in a received signal according to the present invention includes determining whether the pseudorange of the satellite is normal based on a comparison between the pseudorange of the satellite that transmitted the GNSS signal and the pseudorange of a predetermined reference satellite. It may also be possible to further determine whether the

The method for detecting an abnormality in a received signal according to the present invention is such that the reference transmission time for the satellite that transmitted the GNSS signal is a transmission time included in a GNSS signal transmitted from the satellite in the past. You can also do this.

The method for detecting an abnormality in a received signal according to the present invention is such that the reference transmission time of the satellite that transmitted the GNSS signal is a transmission time included in a GNSS signal transmitted from another satellite. It's okay.

The method for detecting an abnormality in a received signal according to the present invention may be such that the abnormal state of a satellite determined to be abnormal is maintained for a predetermined period of time.

The method for detecting an abnormality in a received signal according to the present invention includes changing the number of reception channels allocated to satellites having a different frequency band from the satellites determined to be abnormal, depending on the number of satellites determined to be abnormal. You can do it like this.

The method for detecting an abnormality in a received signal according to the present invention may include determining whether the direction of arrival of the GNSS signal is normal based on the path difference index for each type of satellite.

Further, the receiving signal abnormality detection device according to the present invention includes a receiving unit that receives GNSS signals transmitted from a plurality of satellites via a plurality of antennas; a transmission time determination unit that determines whether the transmission time of the GNSS signal is normal based on a comparison between the time and a predetermined reference transmission time; and each of the plurality of antennas from the satellite that transmitted the GNSS signal. a path difference determination unit that determines whether the direction of arrival of the GNSS signal is normal based on a path difference index representing a difference in path to the GNSS signal; and a positioning unit that calculates positioning information; Used in calculation processing of the positioning information by the positioning unit based on the determination result of whether the transmission time of the signal is normal and the determination result of whether the direction of arrival of the GNSS signal is normal. It is characterized by determining the satellite.

The reception signal abnormality detection device according to the present invention determines whether the pseudorange of the satellite is normal based on a comparison between the pseudorange of the satellite that transmitted the GNSS signal and the pseudorange of a predetermined reference satellite. further comprising a pseudorange determination unit that determines whether the transmission time of the GNSS signal is normal, the determination result of whether the direction of arrival of the GNSS signal is normal, and the The satellite to be used in the calculation process of the positioning information by the positioning unit may be determined based on a determination result of whether the pseudorange of the satellite is normal.

The reception signal abnormality detection device according to the present invention is such that the reference transmission time for the satellite that transmitted the GNSS signal is a transmission time included in a GNSS signal transmitted from the satellite in the past. You can also do this.

The reception signal abnormality detection device according to the present invention is configured such that the reference transmission time of the satellite that transmitted the GNSS signal is a transmission time included in a GNSS signal transmitted from another satellite. It's okay.

The reception signal abnormality detection device according to the present invention may be configured such that the abnormal state of a satellite determined to be abnormal is maintained for a predetermined period of time.

In the reception signal abnormality detection device according to the present invention, the number of reception channels allocated to satellites having a different frequency band from the satellites determined to be abnormal changes depending on the number of satellites determined to be abnormal. You can do it like this.

The reception signal abnormality detection device according to the present invention may determine whether the direction of arrival of the GNSS signal is normal based on the path difference index for each type of satellite.

According to the method for detecting an abnormality in a received signal and the apparatus for detecting an abnormality in a received signal according to the present invention, an abnormality in the transmission time of a GNSS signal can be detected, and the path difference (direction of arrival of the GNSS signal) from a satellite to each of a plurality of antennas can be detected. ), it is possible to more reliably detect abnormalities in the GNSS signal, but the detection is delayed because the processing is performed on GNSS signals transmitted from multiple satellites. On the other hand, abnormalities in transmission time can be detected immediately because they are processed independently for each satellite, and by combining the transmission time determination process and the path difference determination process, it is possible to detect abnormalities in the received signal in GNSS. It becomes possible to improve the reliability of the abnormality detection process of the received signal in GNSS by detecting abnormalities in a mutually complementary manner.

According to the method for detecting an abnormality in a received signal and the apparatus for detecting an abnormality in a received signal according to the present invention, when an abnormality in a pseudorange of a satellite is further detected, a pseudorange determination process is further combined. It becomes possible to more reliably detect an abnormality in a received signal in GNSS and further improve the reliability of the abnormality detection process in a received signal in GNSS.

FIG. 1 is a functional block diagram showing a schematic configuration of a GNSS compass according to an embodiment. 2 is a diagram showing the arrangement of multiple GNSS antennas in the GNSS compass of FIG. 1. FIG. 3 is a diagram illustrating a path difference between the GNSS antennas in FIG. 2. FIG.

The present invention will be described below based on the illustrated embodiments. In this embodiment, an example will be described in which a received signal abnormality detection device according to the present invention is incorporated into a GNSS compass.

(Overall configuration of GNSS compass)
FIG. 1 is a functional block diagram showing a schematic configuration of a GNSS compass 1 according to an embodiment, including a receiving signal abnormality detection device according to the present invention. The GNSS compass 1 is used, for example, by being mounted on a moving body such as a ship, a vehicle, or an aircraft.

The GNSS compass 1 according to the embodiment uses satellite signals/positioning signals (" The control unit 2, the GNSS antenna 3 and the , a GNSS receiving section 4, an anomaly detecting section 5, and a positioning section 6. The respective parts constituting the GNSS compass 1 are connected to each other so that they can send and receive signals and transmit information to each other via a bus.

Examples of GNSS include GPS (abbreviation for Global Positioning System, Global Positioning Satellite; Global Positioning System), GLONASS (abbreviation for GLObal Navigation Satellite System), and BDS (abbreviation for BeiDou Navigation Satellite System). .

Each of the plurality of GNSS satellites transmits a GNSS signal including ephemeris, which is data indicating the current position of the GNSS satellite, as a radio wave. The GNSS signal transmitted from each of the plurality of GNSS satellites also includes information indicating the time when the GNSS satellite transmitted the GNSS signal as a radio wave.

The control unit 2 has a function of controlling the operation of each part constituting the GNSS compass 1, and includes, for example, a central processing unit (CPU) that performs arithmetic processing related to detecting abnormalities in GNSS signals and calculating the position of the GNSS compass 1. : Abbreviation for Central Processing Unit).

The control unit 2 also stores programs, various information, and data used by the central processing unit (CPU) to perform calculations related to detecting abnormalities in GNSS signals and calculating the position of the GNSS compass 1. A function that serves as a storage area for storing data or as a work area for temporarily storing data and information generated when the central processing unit (CPU) performs the arithmetic processing. For example, a device having at least one of ROM (abbreviation for Read Only Memory), which is a read-only storage device, RAM (abbreviation), which is a readable and writable storage device, and a hard disk. It is structured as an introduction.

The control unit 2 controls the processing of each part of the GNSS compass 1 according to the control program by having a central processing unit (CPU) execute a program (referred to as a "control program") for controlling the operation of the GNSS compass 1. Discipline and control the beginning, content, and ending.

The GNSS receiving unit 4 is configured to receive GNSS signals transmitted from each of a plurality of GNSS satellites S_i (where, i: a number unique to each satellite for distinguishing and identifying a plurality of GNSS satellites). A mechanism consisting of at least two GNSS receivers, each with a GNSS antenna 3. In this embodiment, the GNSS receiver 4 includes three GNSS receivers 4A, 4B, and 4C, the GNSS receiver 4A is equipped with a GNSS antenna 3A, the GNSS receiver 4B is equipped with a GNSS antenna 3B, and the GNSS receiver 4A is equipped with a GNSS antenna 3B. The device 4C is equipped with a GNSS antenna 3C.

The three GNSS antennas 3A, 3B, and 3C are spaced apart from each other at predetermined intervals and fixed on the moving body on which the GNSS compass 1 is mounted. In this embodiment, three GNSS antennas 3A, 3B, and 3C are arranged at the vertices of an equilateral triangle (see FIG. 2).

The line segment connecting the GNSS antennas 3A, 3B, and 3C is called a "baseline." The baseline dimension, which is the distance between the GNSS antennas 3A, 3B, and 3C, is known as a design value for the arrangement of the GNSS antennas 3A, 3B, and 3C. In this embodiment, the dimensions of the base line AB between GNSS antenna 3A and GNSS antenna 3B, the dimension of base line BC between GNSS antenna 3B and GNSS antenna 3C, and the dimension between GNSS antenna 3A and GNSS antenna 3C are explained. The dimensions of the baseline AC are all known. The dimension of the baseline, which is the distance between the GNSS antennas 3A, 3B, and 3C, is set to one wavelength or more (usually about several wavelengths) in order to avoid interference between the GNSS antennas 3A, 3B, and 3C.

Each GNSS receiver 4A, 4B, 4C receives the GNSS signal transmitted from each GNSS satellite S_i via the GNSS antenna 3A, 3B, 3C, converts it into an electrical signal (in particular, a digital signal), and outputs the signal.

The GNSS signal is superimposed on a carrier wave and is sequentially transmitted as radio waves (referred to as "GNSS radio waves") from the GNSS satellite S_i. Each GNSS receiver 4A, 4B, 4C receives a GNSS radio wave, demodulates the GNSS radio wave, and extracts a GNSS signal. Then, the GNSS signal is output from the GNSS receiving section 4.

By executing the control program by the central processing unit (CPU) of the control unit 2, an abnormality detection section 5 and a positioning section 6 are configured within the control unit 2.

The abnormality detection unit 5 is a mechanism for detecting an abnormality in the GNSS signal output from the GNSS receiving unit 4 and outputting a detection result.

The positioning unit 6 is a mechanism for calculating and outputting positioning information using the GNSS signal output from the GNSS receiving unit 4.

Although the positioning information calculated by the positioning unit 6 is not limited to specific items, for example, at least one of the position, direction, and attitude (e.g., rolling, pitching, rate of turn (ROT)) of the own aircraft, etc. These include: The calculation process of the positioning information by the positioning unit 6 can be performed using well-known techniques, and the present invention is not limited to specific items or methods, so a detailed explanation will be omitted.

The positioning unit 6 determines the GNSS satellite S_i to be excluded from the satellite group used in the positioning information calculation process based on the detection result of the abnormality in the GNSS signal output from the anomaly detection unit 5 (in other words, the positioning information (Determine the GNSS satellite S_i to be used in calculation processing).

(Processing content of the abnormality detection unit)
The method for detecting an abnormality in a received signal according to the embodiment includes receiving GNSS signals transmitted from a plurality of GNSS satellites S_i via a plurality of GNSS antennas 3A, 3B, and 3C, and detecting the abnormality contained in the GNSS signals. It is determined whether the transmission time of the GNSS signal is normal based on a comparison between the transmission time of the GNSS signal and a predetermined reference transmission time, and the pseudorange ρ_i of the GNSS satellite S_i that transmitted the GNSS signal and the predetermined reference satellite are determined. Based on the comparison with the pseudorange ρr of Sr, it is determined whether the pseudorange ρ_i of the GNSS satellite S_i is normal or not. It is determined whether the arrival direction of the GNSS signal is normal based on an index representing the difference in the routes of the GNSS signals.

Further, the GNSS compass 1 according to the embodiment, which includes a receiving signal abnormality detection device as a device that implements the above-described method for detecting a received signal abnormality, detects a plurality of GNSS signals transmitted from a plurality of GNSS satellites S_i. The transmission time of the GNSS signal is determined based on the comparison between the transmission time of the GNSS signal included in the GNSS signal and a predetermined reference transmission time. A transmission time determination unit 51 determines whether or not the GNSS signal is normal, and the pseudorange of the GNSS satellite S_i is determined based on a comparison between the pseudorange ρ_i of the GNSS satellite S_i that transmitted the GNSS signal and the pseudorange ρr of a predetermined reference satellite Sr. A pseudorange determination unit 52 determines whether ρ_i is normal or not, and a GNSS signal is determined based on an index representing the difference in path from the GNSS satellite S_i that transmitted the GNSS signal to each of the plurality of GNSS antennas 3A, 3B, and 3C. It has a path difference determination unit 54 that determines whether the arrival direction of the GNSS signal is normal, and a positioning unit 6 that calculates positioning information. GNSS used in the calculation process of positioning information by the positioning unit 6 based on the determination result of whether the direction of arrival of the GNSS signal is normal and the determination result of whether the pseudorange ρ_i of the GNSS satellite S_i is normal. The satellite S_i is determined as follows.

The abnormality detection unit 5 is a mechanism for detecting an abnormality in the GNSS signal, and each of the GNSS reception units 4 (in addition, each of the GNSS antennas 3 (specifically, one of 3A, 3B, and 3C)) A GNSS signal which is a received signal in GNSS is received based on the GNSS signal and is outputted at a predetermined period from a GNSS receiver (consisting of three GNSS receivers 4A, 4B, 4C). A calculation process (referred to as "abnormality detection calculation process") for detecting an abnormality in the signal is executed. The abnormality detection calculation process may be executed at the predetermined cycle in accordance with the predetermined cycle at which the GNSS signal is output from the GNSS receiver 4, or may be executed at a cycle different from the predetermined cycle. You may also do so.

The abnormality detection section 5 includes a transmission time determination section 51, a pseudo distance determination section 52, a route difference calculation section 53, and a route difference determination section 54.

The transmission time determination unit 51 receives input of the GNSS signal for each GNSS satellite S_i output from the GNSS reception unit 4, and determines whether the transmission time of the GNSS signal is normal. The process performed by the transmission time determination unit 51 is referred to as "transmission time determination process."

The transmission time determination unit 51 determines, for each GNSS satellite S_i, whether the absolute value of the difference between the transmission time of the GNSS signal included in the GNSS signal and a predetermined reference transmission time is greater than or equal to a predetermined time difference threshold. to judge.

The reference transmission time may be set for each GNSS satellite S_i, or may be set as a common time for all GNSS satellites S_i.

When the reference transmission time is set for each GNSS satellite S_i, the reference transmission time for the GNSS satellite S_i is set to the transmission time that was acquired and stored in the GNSS signal transmitted from the GNSS satellite S_i in the past. A time obtained by adding the elapsed time from the time when the GNSS signal was received may be used.

The elapsed time is measured using, for example, a temperature-compensated crystal oscillator (TCXO) mounted on the GNSS receiver 4 as a measuring device for elapsed time. In this case, the elapsed time may be corrected by taking into account an error in an elapsed time measurement device (for example, a temperature-compensated crystal oscillator) that changes over time or a Doppler shift deviation of the GNSS satellite S_i. Note that the Doppler shift is the frequency difference between the carrier frequency of the GNSS radio wave transmitted from the GNSS satellite S_i and the reception frequency at the GNSS receiver 4 (specifically, the GNSS receivers 4A, 4B, and 4C), which is caused by the Doppler effect. It is required as.

When determining whether the transmission time of the GNSS signal is normal (that is, in the transmission time determination process), only the decimal part of the transmission time of the GNSS signal may be used.

The time difference threshold is not limited to a specific value, but is appropriately set to an appropriate value, taking into account errors that are assumed to occur due to, for example, mechanical errors. If the reference transmission time for the GNSS satellite S_i is the transmission time obtained in the past for the GNSS satellite S_i plus the elapsed time, the time difference threshold is, for example, in the range of about 1 to 3 milliseconds. It is conceivable that it is set to one of these values.

When the absolute value of the difference between the transmission time of the GNSS signal and the reference transmission time included in the GNSS signal is equal to or greater than the time difference threshold, the transmission time determination unit 51 determines that the transmission time of the GNSS signal is abnormal. , the GNSS satellite S_i that transmitted the GNSS signal is classified as having an abnormal transmission time.

On the other hand, when the reference transmission time is set as common to all GNSS satellites S_i, the reference transmission time for GNSS satellite S_i is set as the reference transmission time for other GNSS satellites S_j (where j: multiple GNSS satellites are distinguished from each other). It is a number unique to each satellite for identifying each satellite, and the transmission time of the GNSS signal included in the GNSS signal transmitted from i≠j; the same applies hereinafter) may be used. As the other GNSS satellite S_j, for example, the elevation angle of the satellite is selected from among the plurality of GNSS satellites S_i whose GNSS signals are being received by the GNSS receiver 4 at the time of execution of the relevant (or most recent) abnormality detection calculation process. The satellite with the largest is selected.

In this case, the transmission time determination unit 51 determines, for each GNSS satellite S_i, the difference between the transmission time of the GNSS signal and the reception time of the GNSS signal included in the GNSS signal transmitted from the GNSS satellite S_i, and other Whether the absolute value of the difference between the transmission time of the GNSS signal included in the GNSS signal transmitted from the GNSS satellite S_j and the reception time of the GNSS signal is equal to or greater than a predetermined time difference threshold. to judge. The reception time of the GNSS signal is specified by the clock function/time information held by the GNSS receiving unit 4. The clock function/time information held by the GNSS receiver 4 is supplied from, for example, a temperature compensated crystal oscillator (TCXO) installed in the GNSS receiver 4 as a device common to the plurality of GNSS receivers 4A, 4B, and 4C.

When the transmission time of the GNSS signal included in the GNSS signal transmitted from another GNSS satellite S_j is used as the reference transmission time for the GNSS satellite S_i, the time difference threshold value is determined based on the GNSS type of the GNSS satellite S_i. (For example, GPS, GLONASS, BDS) and the GNSS type of the other GNSS satellite S_j may be set to different values depending on the combination. For example, in the case of a combination of GPS, the time difference threshold is set to a value in the range of about 20 to 30 milliseconds, and in the case of a combination of GPS and BDS, the time difference threshold is set to a value of 90 to 110 milliseconds. It is conceivable that the value may be set to any value within a range of degrees.

The transmission time determination unit 51 determines the difference between the transmission time of the GNSS signal included in the GNSS signal transmitted from the GNSS satellite S_i and the reception time of the GNSS signal, and the GNSS signal transmitted from the other GNSS satellite S_j. When the absolute value of the difference between the transmission time of the GNSS signal and the reception time of the GNSS signal included in is equal to or greater than the time difference threshold, the GNSS signal transmitted from the GNSS satellite S_i is The GNSS satellite S_i that transmitted the GNSS signal is classified as having an abnormal transmission time.

Then, the transmission time determination unit 51 outputs information regarding the GNSS satellite S_i classified as having an abnormal transmission time to the positioning unit 6 as satellite information with an abnormal transmission time.

Next, the pseudorange determining unit 52 receives the GNSS signal for each GNSS satellite S_i output from the GNSS receiving unit 4, and determines whether the pseudorange of the GNSS satellite S_i that transmitted the GNSS signal is normal. judge. The process performed by the pseudorange determination unit 52 is referred to as "pseudorange determination process."

The pseudorange is the propagation distance of the GNSS signal transmitted from the GNSS satellite S_i and received via the GNSS antenna 3, and is the time when the received GNSS signal (in other words, GNSS radio wave) was transmitted from the GNSS satellite S_i. This distance is determined from the difference from the time received via the GNSS antenna 3 (so-called propagation time of the GNSS signal).

The pseudorange ρ_i of the GNSS satellite S_i is determined by the difference between the time when the GNSS signal (GNSS radio wave) is transmitted from the GNSS satellite S_i and the time when the GNSS signal (GNSS radio wave) is received via the GNSS antenna 3. It is calculated by multiplying by the propagation speed (specifically, the speed of light).

The time when the GNSS signal was transmitted from the GNSS satellite S_i is included in the GNSS signal. Further, the time when the GNSS signal is received via the GNSS antenna 3 is specified by the clock function/time information held by the GNSS receiving unit 4. The clock function/time information held by the GNSS receiver 4 is supplied from, for example, a temperature compensated crystal oscillator (TCXO) installed in the GNSS receiver 4 as a device common to the plurality of GNSS receivers 4A, 4B, and 4C. Note that the propagation time of the GNSS signal, which corresponds to the difference between the time when the GNSS signal was transmitted and the time when the GNSS signal was received, may be specified based on the amount of phase shift of the C/A code. Note that the C/A code is a code unique to each GNSS satellite S_i, and functions as information indicating the transmission source.

The pseudorange determination unit 52 determines, for each GNSS satellite S_i, whether the absolute value of the difference between the pseudorange ρ_i of the GNSS satellite S_i and the pseudorange ρr of a predetermined reference satellite Sr is larger than a predetermined pseudorange difference threshold. to judge. The reference satellite Sr is, for example, the one whose elevation angle is the highest among the plurality of GNSS satellites S_i whose GNSS signals are being received by the GNSS receiver 4 at the time of execution of the relevant (or most recent) abnormality detection calculation process. Larger satellites are selected.

The pseudorange difference threshold is not limited to a specific value; for example, the maximum value assumed as the difference in pseudoranges between GNSS satellites is taken into account when assuming the orbits of GNSS satellites. , is appropriately set to an appropriate value. It is conceivable that the pseudo distance difference threshold is set to any value within a range of, for example, about 1 to 2 km.

When the absolute value of the difference between the pseudorange ρ_i of the GNSS satellite S_i and the pseudorange ρr of the reference satellite Sr is larger than a pseudorange difference threshold, the pseudorange determination unit 52 determines that the pseudorange of the GNSS satellite S_i is abnormal. , classify the GNSS satellite S_i as a pseudorange anomaly.

The pseudorange determination unit 52 determines that the absolute value of the difference between the pseudorange ρ_i of the GNSS satellite S_i and the pseudorange ρr of the reference satellite Sr is larger than the pseudorange difference threshold, and that the GNSS transmitted from the GNSS satellite S_i When the signal strength/reception strength of the signal is higher than a predetermined threshold value, the GNSS satellite S_i may be determined to have an abnormal pseudorange, and the GNSS satellite S_i may be classified as having an abnormal pseudorange.

Then, the pseudorange determining unit 52 outputs information regarding the GNSS satellite S_i classified as pseudorange abnormal to the positioning unit 6 as pseudorange abnormal satellite information.

Next, the path difference calculating section 53 receives the input of the GNSS signal for each GNSS satellite S_i output from the GNSS receiving section 4, and uses the information of the GNSS signal to calculate the distance from the GNSS antenna 3A, 3B, 3C Calculate the difference in travel distance. The process performed by the route difference calculation unit 53 and the route difference determination unit 54 is referred to as “path difference determination processing”.

The path difference calculation unit 53 calculates the distance between each GNSS antenna from the GNSS satellite S_i, which is caused by the fact that the plurality of GNSS antennas 3A, 3B, and 3C are spaced apart from each other at a predetermined interval for each GNSS satellite S_i. The difference (absolute value) between the routes to GNSS antennas 3A, 3B, and 3C is calculated for each interval between the GNSS antennas 3A, 3B, and 3C, that is, for each combination of two GNSS antennas 3.

FIG. 3 is a diagram illustrating the difference in routes. Although the path difference is actually determined in three dimensions, the principle of the path difference will be explained in two dimensions in FIG. 3. In the example shown in FIG. 3, the difference between the route to GNSS antenna 3A and the route to GNSS antenna 3B for each of GNSS satellite S_1 and GNSS satellite S_2 (i.e., the difference in route between GNSS antenna 3A and GNSS antenna 3B) ) and explain it.

The difference C_1AB between the path from GNSS satellite S_1 to GNSS antenna 3A and the path to GNSS antenna 3B is expressed as in the following formula 1, and is the difference between the path from GNSS satellite S_2 to GNSS antenna 3A and the path to GNSS antenna 3B. The difference C_2AB is expressed as in Equation 2 below (see FIG. 3(A)).
(Math. 1) C_1AB = L_AB×cos(θ_1)
(Math. 2) C_2AB = L_AB×cos(θ_2)
Here,
L_AB: Dimension of base line AB between GNSS antenna 3A and GNSS antenna 3B θ_1: Elevation angle of GNSS satellite S_1 θ_2: Elevation angle of GNSS satellite S_2

The difference C_1AB between the path from the GNSS satellite S_1 to the GNSS antenna 3A and the path to the GNSS antenna 3B, expressed as in Equation 1 above, is calculated according to Equation 3 below. Further, the difference C_2AB between the path from the GNSS satellite S_2 to the GNSS antenna 3A and the path to the GNSS antenna 3B, expressed as in Equation 2 above, is calculated according to Equation 4 below.
(Math. 3) C_1AB = λ_1×(N_1+P_1AB)
(Math. 4) C_2AB = λ_2×(N_2+P_2AB)
Here,
λ_1: Wavelength of carrier wave of GNSS radio wave of GNSS satellite S_1 λ_2: Wavelength of carrier wave of GNSS radio wave of GNSS satellite S_2 N_1: Integer bias of GNSS radio wave of GNSS satellite S_1 (cycle or more)
N_2: Integer bias of GNSS radio waves of GNSS satellite S_2 (more than one cycle)
P_1AB: Single difference between antennas of GNSS radio waves of GNSS satellite S_1 (less than a cycle)
P_2AB: Single difference between antennas of GNSS radio waves of GNSS satellite S_2 (less than a cycle)

The inter-antenna single difference P_iXY for the GNSS satellite S_i (where X, Y: antenna symbols for distinguishing and identifying each of the multiple GNSS antennas 3; X≠Y; the same applies hereinafter) is the difference between the two GNSS satellites This is the difference in carrier phase integrated value of one GNSS satellite S_i with respect to antenna 3 (in the example shown in FIG. 3, GNSS antenna 3A and GNSS antenna 3B).

The path difference calculation unit 53 calculates the difference C_iXY between the path from the GNSS satellite S_i to the GNSS antenna X and the path to the GNSS antenna Y for each combination of two GNSS antennas 3 for each GNSS satellite S_i.

Next, the path difference determination unit 54 determines whether the path difference C_iXY calculated by the path difference calculation unit 53 for each GNSS satellite S_i and for each combination of two GNSS antennas 3 is normal.

Here, in the example shown in FIG. 3, since the GNSS satellite S_1 and the GNSS satellite S_2 are usually located at different spatial positions, the elevation angle θ_1 of each satellite as seen from the GNSS compass 1 (specifically, the GNSS antenna 3) and the elevation angle θ_2 are different from each other. Since the elevation angle θ_1 of the GNSS satellite S_1 and the elevation angle θ_2 of the GNSS satellite S_2 are different from each other, the path difference C_1AB for the GNSS satellite S_1 and the path difference C_2AB for the GNSS satellite S_2 are different from each other (see Fig. 3). A) and see Equations 1 and 2 above).

On the other hand, if GNSS satellite S_1 and GNSS satellite S_2 are both located at the same spatial position, the elevation angle θ_1 and elevation angle θ_2 of each satellite as seen from GNSS compass 1 (specifically, GNSS antenna 3) are the same. (See Figure 3(B)). If the elevation angle θ_1 of the GNSS satellite S_1 and the elevation angle θ_2 of the GNSS satellite S_2 are the same, the difference C_1AB in the path for the GNSS satellite S_1 and the difference C_2AB in the path for the GNSS satellite S_2 will be the same (formula 1 above). , see Equation 2).

An example of a case where the elevation angle θ_1 of GNSS satellite S_1 and the elevation angle θ_2 of GNSS satellite S_2 are the same is when, for example, a signal containing positioning information and orbit information of multiple GNSS satellites is transmitted from a single transmitting antenna. In other words, it is possible to pretend that GNSS signals (in other words, GNSS radio waves) are being transmitted from multiple GNSS satellites, and then use a single transmitting antenna (in other words, at the same location; however, it is installed on the ground). A case may be considered in which multiple GNSS signals are transmitted from a single transmitting antenna/same point (including a single transmitting antenna station). In this respect, "GNSS signals transmitted from multiple GNSS satellites S_i" in this invention are transmitted from a single transmitting antenna/same point after making it appear that GNSS signals are being transmitted from multiple GNSS satellites S_i. Contains signals emitted from.

Therefore, the route difference determination unit 54 determines that when the difference between the route differences (absolute values) C_i The plurality of GNSS satellites S_i are always classified as having an abnormal course.

Specifically, for example, for each GNSS antenna 3, that is, for each combination of two GNSS antennas 3, the maximum value and minimum value of the path difference (absolute value) C_iXY for a plurality of GNSS satellites S_i are calculated. When the difference is less than a predetermined path difference threshold, it is determined that the direction of arrival of the GNSS signal in the plurality of GNSS satellites S_i is abnormal, and the plurality of GNSS satellites S_i are classified as always having a path difference.

The path difference threshold is not limited to a specific value; for example, even if multiple GNSS signals are actually transmitted from a single transmitting antenna/same point, it may occur due to mechanical errors, etc. It is set to an appropriate value after taking into account the expected errors.

A lower limit for the number of satellites may be set when determining that the direction of arrival of a GNSS signal is abnormal for a plurality of GNSS satellites S_i. For example, when the difference between the maximum value and the minimum value of the path difference C_iXY for the two GNSS satellites S_i is less than or equal to the path difference threshold, the two GNSS satellites S_i are not always classified as path differences; When the difference between the maximum value and the minimum value of the path difference C_iXY for three or more GNSS satellites S_i is less than the path difference threshold, the three or more GNSS satellites S_i are always classified as path differences. It's okay. Although the lower limit of the number of satellites in this case is not limited to a specific value, it may be set to any value in the range of, for example, about 3 to 5.

The plurality of GNSS satellites S_i for determining a path difference abnormality may all be of the same type, and the path difference abnormality may be determined for each type of satellite, such as GPS, GLONASS, BDS, etc. For example, when the difference between the maximum value and the minimum value of the path differences for two GPS satellites is less than or equal to the path difference threshold, the two GPS satellites are not always classified as path differences; When the difference between the maximum value and the minimum value of the route differences for the GPS satellites is less than or equal to a route difference threshold value, the three or more GPS satellites may be always classified as having a route difference. Although the lower limit of the number of satellites in this case is not limited to a specific value, it may be set to any value in the range of, for example, about 3 to 5.

The course difference determination unit 54 determines whether the plurality of GNSS satellites S_i is equal to or less than the route difference threshold value when the difference between the maximum value and the minimum value of the route difference C_i S_i may be always classified as a route difference, or a state in which the difference between the maximum value and the minimum value of route differences C_i When continuing, the plurality of GNSS satellites S_i may be always classified according to their route differences.

Here, when a plurality of GNSS satellites S_i exist in mutually different spatial positions, the inter-antenna singlet differences P_iXY for the plurality of GNSS satellites S_i are usually different from each other, whereas a single transmitting antenna/ When a plurality of GNSS signals are transmitted from the same point, the inter-antenna singlet difference P_iXY for the plurality of GNSS satellites S_i becomes the same. Therefore, in the process of determining the path difference for each GNSS satellite S_i, the inter-antenna single difference P_iXY for a plurality of GNSS satellites S_i may be verified (see Equations 3 and 4 above).

Note that even though the GNSS satellite S_1 and the GNSS satellite S_2 exist in mutually different spatial positions and the difference in path C_1AB for the GNSS satellite S_1 and the difference in path C_2AB for the GNSS satellite S_2 are actually different, It is also conceivable that the inter-antenna singlet differences P_1AB and P_2AB for the two GNSS satellites S_1 and S_2 happen to be the same. However, since the GNSS satellites S_1 and S_2 are moving, the above state does not last for a long time (for example, more than a few seconds). Furthermore, since the direction of the baseline differs between each GNSS antenna 3, for example, in a combination of GNSS antenna 3A and GNSS antenna 3B, inter-antenna singlet differences P_1AB and P_2AB for two GNSS satellites S_1 and S_2 happen to be the same. Even if this happens, the inter-antenna singlet differences P_1AB and P_2AC for the two GNSS satellites S_1 and S_2 will not be the same in the combination of the GNSS antenna 3A and the GNSS antenna 3C.

When verifying the inter-antenna single difference P_iXY for the plurality of GNSS satellites S_i, the path difference determining unit 54 determines whether the difference between the antenna-to-antenna single differences (absolute value) P_iXY for the plurality of GNSS satellites S_i is a predetermined path difference threshold. When the following is true, the plurality of GNSS satellites S_i are considered to have an abnormal arrival direction of the GNSS signal, and the plurality of GNSS satellites S_i are always classified as having different routes.

Specifically, for example, for each GNSS antenna 3, that is, for each combination of two GNSS antennas 3, the maximum value and minimum value of the inter-antenna single difference (absolute value) P_iXY for a plurality of GNSS satellites S_i are calculated. When the difference with the value is less than or equal to a predetermined path difference threshold, it is determined that the direction of arrival of the GNSS signal in the plurality of GNSS satellites S_i is abnormal, and the plurality of GNSS satellites S_i are always classified as having a path difference.

The path difference threshold in this case is also not limited to a specific value; for example, even if multiple GNSS signals are actually transmitted from a single transmitting antenna/same point, it may be due to mechanical errors, etc. It is set to an appropriate value after taking into account the errors that are expected to occur.

The path difference C_iXY for the GNSS satellite S_i and the single difference between antennas P_iXY, which represent the path difference from the GNSS satellite S_i to each GNSS antenna 3A, 3B, and 3C, are used in the process of determining the path difference for each GNSS satellite S_i. This is called the "path difference index."

Then, the path difference determining unit 54 outputs information regarding the GNSS satellite S_i classified as a path difference abnormality (in other words, an abnormality in the arrival direction of the GNSS signal) to the positioning unit 6 as satellite information of the path difference abnormality.

In each of the above determination processes, the GNSS satellite S_i that is classified as transmission time abnormality, the GNSS satellite S_i that is classified as pseudorange abnormality, and the GNSS satellite S_i that is always classified as route difference are used in the positioning information calculation process by the positioning unit 6. The GNSS signal transmitted from the excluded GNSS satellite S_i is not used for calculation processing of positioning information by the positioning unit 6.

Each item of positioning information calculated by the positioning unit 6 (specifically, the position, direction, and attitude of the own aircraft) is classified into one of transmission time abnormalities, pseudorange abnormalities, and course difference abnormalities. The setting may be made to determine whether to exclude the GNSS satellite S_i. For example, to give an example for illustrative purposes only, when calculating the position of the own aircraft, a GNSS satellite S_i that is classified as a transmission time anomaly is excluded, while a GNSS satellite S_i that is classified as a pseudorange anomaly and its route. Differences: GNSS satellites S_i that are always classified are not excluded, and when calculating the orientation and attitude of the own aircraft, GNSS satellites S_i that are classified as transmission time abnormalities, GNSS satellites S_i that are classified as pseudorange abnormalities, All of the GNSS satellites S_i that are always classified as route differences and route differences may be excluded.

A GNSS satellite S_i classified as a transmission time abnormality, a pseudorange abnormality, or a course difference abnormality (in other words, a GNSS satellite S_i determined to be abnormal) is in a state classified as the above abnormality ( In other words, the above-mentioned abnormal state) may be maintained for a predetermined abnormality holding time (and the above-mentioned determination process may not be performed while the above-mentioned abnormal state is maintained).

The abnormality retention time is not limited to a specific length of time, and may be used, for example, to prevent a situation in which the number of normal GNSS satellites S_i (in other words, used for calculation processing of positioning information by the positioning unit 6) is extremely reduced. An appropriate time length is set as appropriate, taking into consideration the possibility of capturing the GNSS satellite S_i normally due to the movement of the mobile object on which the GNSS Compass 1 is mounted. . The abnormal hold time may be set to zero. In this case, the transmission time determination process, pseudorange determination process, and course difference determination process for each GNSS satellite S_i are performed every time the abnormality detection calculation process is executed.

The abnormality retention time may be set for each type of abnormality. In other words, even if the abnormality holding time is set to the same length for cases where the transmission time is classified as an abnormality, cases where it is classified as a pseudorange abnormality, and cases where the route difference is always classified, Alternatively, the time lengths may be set to be different from each other.

If a state classified as an abnormality is maintained for the abnormality retention time, the GNSS satellite S_i classified as a transmission time abnormality, pseudorange abnormality, or course difference abnormality (any one of them) is maintained for the abnormality retention time. The satellite may be immediately removed from the abnormality classification after the elapse of the abnormality classification and become a satellite to receive GNSS signals (and the satellite to be subjected to each of the above determination processes), or the abnormality may become abnormal after the abnormality retention time has elapsed. When the unclassified state is maintained for a predetermined normal duration, the satellite may be removed from the abnormal classification and become a satellite to receive GNSS signals (and a satellite to be subjected to each of the above determination processes). .

The normal duration time is not limited to a specific length of time; for example, the normal duration time is not limited to a specific length of time; An appropriate length of time is set as appropriate, taking into account avoidance.

The normal duration time may be set for each type of abnormality. In other words, even if the normal duration is set to the same length for cases where the transmission time is classified as an abnormality, cases where it is classified as a pseudorange abnormality, and cases where the route difference is always classified, the normal duration is set to the same length. Alternatively, the time lengths may be set to be different from each other.

When the GNSS satellite S_i is classified as transmission time abnormality, pseudorange abnormality, or course difference abnormality (any one of them), the GNSS signal contained in the GNSS signal transmitted from the GNSS satellite S_i. When the absolute value of the difference between the transmission time and the reference transmission time becomes less than a time difference threshold, it is determined that the abnormality regarding the GNSS satellite S_i has been resolved, and the GNSS satellite S_i is removed from the abnormality classification. (In other words, the abnormal state of the GNSS satellite S_i may be canceled). Further, in a state where the route differences of the plurality of GNSS satellites S_i are always classified, if the difference between the route differences (absolute values) C_iXY for the plurality of GNSS satellites S_i becomes larger than the route difference threshold, It is determined that the path difference abnormality for the plurality of GNSS satellites S_i has been resolved, and the plurality of GNSS satellites S_i are removed from the classification of path difference abnormality (in other words, the abnormality state of the plurality of GNSS satellites S_i is removed. ).

An output device (not shown), which is attached to the GNSS compass 1 and includes, for example, a monitor and a speaker, is provided to detect when a transmission time abnormality, pseudorange abnormality, or course difference abnormality (any one of them) has occurred. The user may be notified by displaying an alarm screen on the monitor of the output device or emitting an alarm from the speaker of the output device. In addition, other devices that use GNSS signals (e.g. radar, inertial navigation device) will be notified of the occurrence of transmission time abnormalities, pseudorange abnormalities, and course difference abnormalities. You may also do so.

The number of GNSS satellites S_i classified as transmission time abnormality, pseudorange abnormality, or course difference abnormality is large, and the number of GNSS satellites S_i used in the calculation process of positioning information by the positioning unit 6 is small. In this case, the number of reception channels allocated to the GNSS satellite S_i that is classified as abnormal and a satellite whose GNSS type is different (that is, whose frequency band is different) may be increased. That is, depending on the number of GNSS satellites S_i that are classified as abnormal, the number of reception channels allocated to satellites having a different frequency band from the GNSS satellite S_i that is classified as abnormal may be changed.

For example, if multiple GNSS types (e.g. GPS, GLONASS, BDS) are shared and assigned to the same reception channel and there is a limit on the number of satellites that can be assigned, the specifications of the GNSS receiving unit 4 may be such that transmission time abnormalities, When there is no GNSS satellite S_i that is classified as a pseudorange anomaly or a path difference anomaly (any of them), a large number of GNSS satellites S_i are allocated with priority given to the accuracy of calculation of positioning information by the positioning unit 6, and on the other hand, the transmission When there are many GNSS satellites S_i that are classified as time anomalies, pseudorange anomalies, and course difference anomalies (any of them), many GNSS satellites S_i that can prioritize the continuation of calculation of positioning information by the positioning unit 6 are allocated. You may also do so.

There are many GNSS satellites S_i that are classified as transmission time abnormalities, pseudorange abnormalities, and course difference abnormalities (any of them), and the number of GNSS satellites S_i used in the calculation process of positioning information by the positioning unit 6 is small. If the situation in which the positioning unit 6 is unable to calculate the positioning information continues for a predetermined period of time due to the above reasons, the GNSS satellite S_i that has been classified as abnormal will be removed from the abnormal classification as a failsafe. The satellite may be a target satellite for receiving a GNSS signal (and a target satellite for each of the above-mentioned determination processes). In this case, the GNSS signal output from the GNSS receiver 4 includes information (e.g. , flag) may be added.

According to the method for detecting an abnormality in a received signal and the GNSS compass 1 according to the embodiment, it is possible to detect a transmission time abnormality and a pseudorange abnormality, and also to detect a path difference abnormality (in other words, an abnormality in the direction of arrival of a GNSS signal). Although it is possible to more reliably detect anomalies in GNSS signals for path difference anomalies using Transmission time anomalies and pseudorange anomalies are processed independently for each GNSS satellite S_i, so they can be detected immediately, and by combining the transmission time and pseudorange determination processing with the path difference determination processing, It becomes possible to detect abnormalities in received signals in a mutually complementary manner and improve the reliability of the abnormality detection process in received signals in GNSS.

Although the embodiments of this invention have been described above, the specific configuration is not limited to the above embodiments, and even if there are changes in the design within the scope of the gist of this invention, Included in invention.

For example, in the above embodiment, the method for detecting an abnormality in a received signal according to the present invention is implemented in the GNSS compass 1 whose schematic configuration is shown in FIG. The device/device to which the method for detecting an abnormality in a received signal according to the present invention is applied or the device for detecting an abnormality in a received signal according to the present invention is incorporated is shown in Fig. 1. The method for detecting an abnormality in a received signal according to the present invention is not limited to the GNSS compass 1 whose schematic configuration is shown in FIG. In addition, the method for detecting an abnormality in a received signal according to the present invention may be applied to other types of equipment or devices that utilize GNSS, or the method for detecting an abnormality in a received signal according to the present invention may be incorporated. The detection device may be incorporated into other types of equipment or devices that utilize GNSS.

Further, in the embodiment described above, the pseudo distance determination unit 52 is provided to perform the pseudo distance determination process, but the pseudo distance determination process is not an essential process in the present invention. In this case as well, by performing the transmission time determination process by the transmission time determination unit 51, the process is performed independently for each GNSS satellite S_i, so detection can be performed immediately. By combining the above determination processing with the determination processing, it is possible to detect abnormalities in received signals in GNSS in a mutually complementary manner and improve the reliability of the abnormality detection processing in received signals in GNSS.

1 GNSS compass 2 Control unit 3 GNSS antenna 3A, 3B, 3C GNSS antenna 4 GNSS receiver 4A, 4B, 4C GNSS receiver 5 Abnormality detection unit 51 Transmission time determination unit 52 Pseudo-range determination unit 53 Route difference calculation unit 54 Route difference Judgment unit 6 Positioning unit

Claims (18)

Receive GNSS signals transmitted from multiple satellites via multiple antennas,
Determining whether or not the transmission time of the GNSS signal is normal based on a comparison between the transmission time of the GNSS signal included in the GNSS signal and a predetermined reference transmission time,
determining whether the direction of arrival of the GNSS signal is normal based on a path difference index representing a path difference from the satellite that transmitted the GNSS signal to each of the plurality of antennas;
A method for detecting an abnormality in a received signal, characterized in that: further determining whether the pseudorange of the satellite is normal based on a comparison between the pseudorange of the satellite that transmitted the GNSS signal and the pseudorange of a predetermined reference satellite;
2. The method for detecting an abnormality in a received signal according to claim 1. The reference transmission time for the satellite that transmitted the GNSS signal is a transmission time included in a GNSS signal transmitted from the satellite in the past.
3. The method for detecting an abnormality in a received signal according to claim 1 or 2. The reference transmission time for the satellite that transmitted the GNSS signal is a transmission time included in a GNSS signal transmitted from another satellite,
3. The method for detecting an abnormality in a received signal according to claim 1 or 2. Maintaining the abnormal state of a satellite determined to be abnormal for a predetermined period of time;
3. The method for detecting an abnormality in a received signal according to claim 1 or 2. If the transmission time of the GNSS signal is determined to be normal while the abnormal state of the satellite determined to be abnormal is maintained, the normality of the satellite determined to be abnormal is maintained. release the state of not being
3. The method for detecting an abnormality in a received signal according to claim 1 or 2. When the direction of arrival of the GNSS signal is determined to be abnormal for a plurality of satellites and the abnormal state is maintained, and the direction of arrival of the GNSS signal is determined to be normal for a plurality of satellites, canceling the abnormal state regarding the satellite;
3. The method for detecting an abnormality in a received signal according to claim 1 or 2. changing the number of reception channels allocated to satellites having a different frequency band from the satellites determined to be abnormal, depending on the number of satellites determined to be abnormal;
3. The method for detecting an abnormality in a received signal according to claim 1 or 2. determining whether the direction of arrival of the GNSS signal is normal based on the path difference index for each type of satellite;
2. The method for detecting an abnormality in a received signal according to claim 1. a receiving unit that receives GNSS signals transmitted from multiple satellites via multiple antennas;
a transmission time determination unit that determines whether the transmission time of the GNSS signal is normal based on a comparison between the transmission time of the GNSS signal included in the GNSS signal and a predetermined reference transmission time;
a path difference determination unit that determines whether the direction of arrival of the GNSS signal is normal based on a path difference index representing a path difference from the satellite that transmitted the GNSS signal to each of the plurality of antennas; have,
A device for detecting an abnormality in a received signal, characterized in that: further comprising a pseudorange determination unit that determines whether the pseudorange of the satellite is normal based on a comparison between the pseudorange of the satellite that transmitted the GNSS signal and the pseudorange of a predetermined reference satellite;
The apparatus for detecting an abnormality in a received signal according to claim 9. The reference transmission time for the satellite that transmitted the GNSS signal is a transmission time included in a GNSS signal transmitted from the satellite in the past.
The apparatus for detecting an abnormality in a received signal according to claim 9 or 10. The reference transmission time for the satellite that transmitted the GNSS signal is a transmission time included in a GNSS signal transmitted from another satellite,
The apparatus for detecting an abnormality in a received signal according to claim 9 or 10. The abnormal state of the satellite determined to be abnormal is maintained for a predetermined period of time.
The apparatus for detecting an abnormality in a received signal according to claim 9 or 10. If the transmission time of the GNSS signal is determined to be normal while the abnormal state of the satellite determined to be abnormal is maintained, the normality of the satellite determined to be abnormal is maintained. release the state of not being
The apparatus for detecting an abnormality in a received signal according to claim 9 or 10. When the direction of arrival of the GNSS signal is determined to be abnormal for a plurality of satellites and the abnormal state is maintained, and the direction of arrival of the GNSS signal is determined to be normal for a plurality of satellites, canceling the abnormal state regarding the satellite;
The apparatus for detecting an abnormality in a received signal according to claim 9 or 10. Depending on the number of satellites determined to be abnormal, the number of reception channels allocated to satellites having a different frequency band from the satellite determined to be abnormal changes;
The apparatus for detecting an abnormality in a received signal according to claim 9 or 10. determining whether the direction of arrival of the GNSS signal is normal based on the path difference index for each type of satellite;
The apparatus for detecting an abnormality in a received signal according to claim 10.