A multi-rangefinder station selection method based on heuristic search algorithm

Abstract

The present invention provides a multi-rangefinder station selection method based on a heuristic search algorithm, which selects stations for multiple rangefinders, takes into account the operating frequencies of ground rangefinders, uses ground rangefinders with operating frequencies falling within the constraint frequency band range as candidates, and after determining the number and frequencies of ground rangefinders, uses a heuristic search algorithm to supplement and eliminate ground rangefinders based on the geometric distribution characterized by the horizontal dilution of precision (HDOP). Thus, it is possible to reduce the signal attenuation caused by ground rangefinder signals to GNSS while selecting stations, and while ensuring the tracking ability, real-time performance, and navigation accuracy of ground rangefinder receivers, minimize the interference of ground rangefinder signals to GNSS signals as much as possible.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace measurement and control communication, and particularly relates to a method for selecting stations for multiple distance measuring equipment based on a heuristic search algorithm. Background Art

[0002] With the gradual construction and improvement of GNSS multi-frequency and multi-mode, GNSS, as the main method of aerospace navigation, is widely used in the field of aerospace measurement and control communication to provide high-precision and high-integrity services. However, the signal strength of GNSS is relatively low and is easily interfered, so it is necessary to provide alternative navigation, positioning, and timing (A-PNT) services when GNSS is unavailable. A-PNT is used to provide required navigation performance (RNP) services, which are required to meet the performance requirements of RNP 1 in the medium and short term and reach the performance requirements of RNP 0.3 in the long term.

[0003] Since the existing ground distance measuring equipment (DME) construction is relatively complete, DME navigation can become a main method to achieve A-PNT. The traditional DME / DME method uses two DME stations for navigation and positioning, which has geometric limitations. Using multiple DMEs for navigation and positioning can effectively improve the geometric distribution, thereby improving accuracy and integrity. Aircraft usually have two multi-band DME receivers that can simultaneously track 6 to 10 different DME signals, which makes multi-DME navigation and positioning possible. However, in some areas, there are more than 20 visible DMEs, exceeding the aircraft's receiving ability for DME signals. Therefore, it is necessary to perform multi-DME station selection to select the optimal DME combination from the visible DMEs. The previous DME station selection methods were mainly for DME / DME. It is necessary to ensure that the included angle between the lines of sight of two DMEs is within the range of 30° - 150° to perform navigation and positioning. This DME station selection method with angle constraints is not applicable to the selection of multiple DMEs. The multi-DME station selection method will execute necessary logical algorithms to enable the DME receiver with limited tracking ability to avoid receiving unnecessary navigation signals and improve real-time processing ability. For the multi-DME station selection algorithm, first, it is necessary to ensure that the overall geometric distribution of the selected DME combination is as close as possible to the optimal geometric distribution. At the same time, it is necessary to avoid frequent changes in tracking DMEs as much as possible.

[0004] In civil signals, the signal broadcast frequencies of GPS L5 and Galileo E5a are around 1176.45 MHz, and the frequency band where they are located is a band that is severely interfered with, especially interfered with by the signals of the DME system. The signal frequency of the DME system is between 960 - 1215 MHz, which is within the frequency band allocated to GNSS E5a / L5. At the same time, DME works in an interrogation - response mode and ranges by sending and receiving strong - power pulse pairs. The interference of strong - power signals on GNSS signals will be further increased. Therefore, when selecting multiple DME stations, it is also necessary to minimize the attenuation of GNSS signals caused by interference. Summary of the Invention

[0005] To solve the problem of selecting DME stations, the present invention provides a method for selecting multiple DME stations based on a heuristic search algorithm, which can minimize the interference of ground DME signals on GNSS signals while ensuring the tracking ability, real - time performance, and navigation accuracy of ground DME receivers.

[0006] A method for selecting multiple DME stations based on a heuristic search algorithm includes the following steps:

[0007] S1: Denote the number of ground DMEs required to implement navigation, positioning, and timing services as N;

[0008] S2: Determine whether the number of currently visible ground DMEs is greater than N. If not, all currently visible ground DMEs are selected to participate in navigation; if greater, perform the station - selection operation, where the station - selection operation is specifically as follows:

[0009] S21: Form a first set of ground DMEs whose operating frequencies fall within the set constraint frequency band range, and form a second set of the remaining ground DMEs;

[0010] S22: Determine whether the number of ground DMEs in the second set is equal to N. If equal, all ground DMEs in the second set are selected to participate in navigation; if less, select ground DMEs from the first set to join the second set so that the number of ground DMEs in the second set is equal to N, and the combination formed by the selected ground DMEs in the first set and the ground DMEs in the initial second set has the minimum horizontal geometric dilution of precision; if greater, eliminate ground DMEs from the second set so that the number of ground DMEs in the second set is equal to N, and the combination formed by the remaining ground DMEs in the second set has the minimum horizontal geometric dilution of precision.

[0011] Further, the constraint frequency band is the overlapping part between the frequency coverage range of GNSS E5a / L5 and the operating frequency range of ground DMEs.

[0012] Further, when the number of ground distance measuring instruments in the second set is less than N, the method for determining the ground distance measuring instruments selected from the first set and added to the second set is as follows:

[0013] S22a: Combine the ground distance measuring instruments in the first set with the ground distance measuring instruments in the second set one by one, and simultaneously obtain the horizontal geometric dilution of precision corresponding to each combination. Then add the ground distance measuring instrument in the first set corresponding to the combination with the minimum horizontal geometric dilution of precision to the second set;

[0014] S22b: Determine whether the number of ground distance measuring instruments in the second set is equal to N. If it is equal, the station selection is completed. If it is less, repeat steps S22a - S22b for the remaining ground distance measuring instruments in the first set until the number of ground distance measuring instruments in the second set is equal to N.

[0015] Further, when the number of ground distance measuring instruments in the second set is greater than N, the method for determining the ground distance measuring instruments to be removed from the second set is as follows:

[0016] S22c: Respectively take each ground distance measuring instrument in the second set as the one to be removed, and simultaneously obtain the horizontal geometric dilution of precision corresponding to each combination formed by the ground distance measuring instruments in the second set except the one to be removed. Then remove the one to be removed corresponding to the combination with the minimum horizontal geometric dilution of precision to the first set;

[0017] S22d: Determine whether the number of ground distance measuring instruments in the second set is equal to N. If it is equal, the station selection is completed. If it is greater, repeat steps S22c - S22d for the remaining ground distance measuring instruments in the second set until the number of ground distance measuring instruments in the second set is equal to N.

[0018] Further, N = 6 - 10.

[0019] Beneficial effects:

[0020] The present invention provides a multi - rangefinder station selection method based on a heuristic search algorithm, which is not restricted by the angle constraint of traditional DME / DME station selection. By searching for the optimal geometric distribution of multiple rangefinders, the accuracy and reliability of navigation positioning are improved. The consideration of the operating frequency of ground distance measuring instruments is increased, and the ground distance measuring instruments whose operating frequencies fall within the constraint frequency band range are used as candidates. After determining the number and frequency of ground distance measuring instruments, a heuristic search algorithm is used to supplement and remove the ground distance measuring instruments participating in the navigation positioning calculation set according to the geometric distribution characterized by the horizontal geometric dilution of precision (HDOP). Thus, the signal attenuation caused by ground distance measuring instrument signals to GNSS can be reduced while selecting stations, and while ensuring the tracking ability, real - time performance and navigation accuracy of ground distance measuring instrument receivers, the interference of ground distance measuring instrument signals to GNSS signals is minimized as much as possible. Description of the drawings

[0021] Figure 1 Flow chart of the multi-distance measuring instrument station selection method provided by the present invention;

[0022] Figure 2 Flow chart of the station selection operation provided by the present invention;

[0023] Figure 3 Flow chart of supplementing ground distance measuring instruments to the second set provided by the present invention;

[0024] Figure 4 Flow chart of removing ground distance measuring instruments from the second set provided by the present invention. Detailed implementation mode

[0025] In order to enable those skilled in the art to better understand the solution of this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application.

[0026] As Figure 1 shown, a multi-distance measuring instrument station selection method based on a heuristic search algorithm includes the following steps:

[0027] S1: Denote the number of ground distance measuring equipment (DME) required to implement the navigation, positioning, and timing service as N. Generally, an aircraft usually has two multi-band ground distance measuring instrument receivers that can simultaneously track 6 to 10 different ground distance measuring instrument signals.

[0028] It should be noted that most traditional station selection algorithms are based on dual DME, and only the geometric angle between two DMEs needs to be constrained, which cannot adapt to the station selection of multi-DME. However, according to the multi-DME station selection algorithm of the present invention, a threshold value for the number of tracked DMEs is preset to perform a preliminary screening on the number of visible DMEs.

[0029] S2: Determine whether the number of currently visible ground distance measuring instruments is greater than N. If it is not greater than, the station selection is completed, and all currently visible ground distance measuring instruments are selected to participate in navigation; if it is greater than, perform the station selection operation, where, as Figure 2 shown, the station selection operation is specifically:

[0030] S21: Form a first set of ground distance measuring instruments whose operating frequencies fall within the set constraint frequency band range, and the remaining ground distance measuring instruments form a second set. Among them, the constraint frequency band is the overlapping part between the frequency coverage range of GNSS E5a / L5 and the operating frequency range of the ground distance measuring instrument.

[0031] That is to say, in step S21, it is necessary to set a constraint frequency band according to the frequency coverage range of GNSS E5a / L5, and perform a first-round screening on the frequencies of visible DME stations, that is, regarding the ground rangefinders that cause GNSS signal attenuation due to their operating frequencies falling within the constraint frequency band as candidates.

[0032] S22: Determine whether the number of ground rangefinders in the second set is equal to N. If it is equal, all the ground rangefinders in the second set are selected to participate in navigation; if it is less, select ground rangefinders from the first set to join the second set so that the number of ground rangefinders in the second set is equal to N, and the combination formed by the selected ground rangefinders in the first set and the ground rangefinders in the initial second set has the minimum Horizontal Dilution Precision (HDOP); if it is greater, remove ground rangefinders from the second set so that the number of ground rangefinders in the second set is equal to N, and the combination formed by the remaining ground rangefinders in the second set has the minimum horizontal geometric precision factor.

[0033] Further, as Figure 3 shown, when the number of ground rangefinders in the second set is less than N, the method for determining the ground rangefinders selected from the first set to join the second set is as follows:

[0034] S22a: Combine the ground rangefinders in the first set with the ground rangefinders in the second set one by one, and at the same time obtain the horizontal geometric precision factor corresponding to each combination, and add the ground rangefinders in the first set corresponding to the combination with the minimum horizontal geometric precision factor to the second set;

[0035] S22b: Determine whether the number of ground rangefinders in the second set is equal to N. If it is equal, the station selection is completed; if it is less, repeat steps S22a - S22b for the remaining ground rangefinders in the first set until the number of ground rangefinders in the second set is equal to N, and the station selection is completed. At this time, all the ground rangefinders in the second set are selected to participate in navigation.

[0036] As Figure 4 shown, when the number of ground rangefinders in the second set is greater than N, the method for determining the ground rangefinders to be removed from the second set is as follows:

[0037] S22c: Respectively regard each ground rangefinder in the second set as the one to be removed, and at the same time obtain the horizontal geometric precision factor corresponding to each combination formed by the ground rangefinders in the second set except the one to be removed, and remove the one to be removed corresponding to the combination with the minimum horizontal geometric precision factor to the first set;

[0038] S22d: Determine whether the number of ground ranging sensors in the second set is equal to N. If it is equal, the station selection is completed. If it is greater, repeat steps S22c - S22d for the remaining ground ranging sensors in the second set until the number of ground ranging sensors in the second set is equal to N, at which point the station selection is completed and all ground ranging sensors in the second set are selected to participate in navigation.

[0039] Thus far, based on the heuristic search algorithm, the present invention has completed the station selection for multiple ranging sensors.

[0040] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can certainly make various corresponding changes and deformations according to the present invention. However, these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

Claims

1. A multi-range finder station selection method based on a heuristic search algorithm, characterized in that It includes the following steps: S1: Denote the number of ground ranging instruments required to implement the navigation positioning and timing service as N; S2: Determine whether the number of currently visible ground ranging instruments is greater than N. If it is not greater, all currently visible ground ranging instruments are selected to participate in the navigation. If it is greater, perform the station selection operation, where the station selection operation is specifically as follows: S21: Form a first set of ground ranging instruments whose operating frequencies fall within the set constraint frequency band range, and the remaining ground ranging instruments form a second set; the constraint frequency band is the overlapping part between the frequency coverage range of GNSS E5a / L5 and the operating frequency range of the ground ranging instruments; S22: Determine whether the number of ground ranging instruments in the second set is equal to N. If it is equal, all ground ranging instruments in the second set are selected to participate in the navigation. If it is less, select ground ranging instruments from the first set to join the second set so that the number of ground ranging instruments in the second set is equal to N, and the combination formed by the selected ground ranging instruments in the first set and the ground ranging instruments in the initial second set has the minimum horizontal geometric dilution of precision. If it is greater, remove ground ranging instruments from the second set so that the number of ground ranging instruments in the second set is equal to N, and the combination formed by the remaining ground ranging instruments in the second set has the minimum horizontal geometric dilution of precision.

2. The multi-rangefinder station selection method based on the heuristic search algorithm according to claim 1, wherein, When the number of ground ranging instruments in the second set is less than N, the method for determining the ground ranging instruments selected from the first set to join the second set is as follows: S22a: Combine the ground ranging instruments in the first set with the ground ranging instruments in the second set one by one, and simultaneously obtain the horizontal geometric dilution of precision corresponding to each combination, and add the ground ranging instruments in the first set corresponding to the combination with the minimum horizontal geometric dilution of precision to the second set; S22b: Determine whether the number of ground ranging instruments in the second set is equal to N. If it is equal, the station selection is completed. If it is less, repeat steps S22a to S22b for the remaining ground ranging instruments in the first set until the number of ground ranging instruments in the second set is equal to N.

3. The multi-rangefinder station selection method based on the heuristic search algorithm according to claim 1, characterized in that When the number of ground ranging instruments in the second set is greater than N, the method for determining the ground ranging instruments removed from the second set is as follows: S22c: Respectively take each ground ranging instrument in the second set as the one to be removed, and simultaneously obtain the horizontal geometric dilution of precision corresponding to each combination formed by the ground ranging instruments in the second set except the one to be removed, and remove the one to be removed corresponding to the combination with the minimum horizontal geometric dilution of precision to the first set; S22d: Determine whether the number of ground ranging instruments in the second set is equal to N. If it is equal, the station selection is completed. If it is greater, repeat steps S22c to S22d for the remaining ground ranging instruments in the second set until the number of ground ranging instruments in the second set is equal to N.

4. The multi-rangefinder station selection method based on the heuristic search algorithm according to claim 1, wherein The N = 6 - 10.

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