RU2598000C1 - Method of autonomous aircraft navigation - Google Patents

Abstract

FIELD: radar equipment.

SUBSTANCE: invention relates to radar engineering area and can be used in designing of radar relief metric systems intended for determination of location of the aircraft (A) with use of radio waves. In the method of independent navigation LA, which involves determining inclined range aircraft to Earth's surface, consisting in using of the radiation of radio waves in the form of several beams and subsequent reception of reflected radio waves on these beams, radio waves are emitted simultaneously in the same carrier frequency in the form of a series of radio pulses, initial phase of which is modulated with M-sequences, orthogonal to each other. Reflected radio waves is separated by beams and determining inclined range of aircraft to Earth surface by correlation method using modulating M-sequences as basic functions or method of the coordinated filtration with use as weight coefficients of the codes which form a modulating M-sequence.

EFFECT: achieved technical effect of the invention - increase of security and quick action of method of aircraft navigation, as well as accuracy of locating aircraft in motion over the measuring section.

1 cl, 10 dwg

Description

The invention relates to the field of radar technology and can be used in the construction of radar relief systems intended for determining the location of aircraft (LA) using radio waves.

Known correlation-extreme navigation method (KESN) aircraft based on a radar relief system using radio waves emitted in the form of a single beam [1], selected as an analogue.

The implementation of the method [1] is to compile a current terrain map (TKM) according to measurements of the altitude of the pressure sensor Ho and a pulsed radio altimeter Nrv during the flight of a measured area and subsequent comparison of TKM with a reference terrain map (ECM) on board the aircraft before it begins to move. Thus, TKM is a one-dimensional map having the form of a single row of an ECM matrix. The aircraft’s location correction signal is calculated based on the analysis of differences (mutual displacements) of the reference and current terrain maps of the measured area. Control the movement of the aircraft by correcting its location. In this KESN, the aircraft trajectory is divided into an autonomous section (observation) and a correction section without their possible combination.

The disadvantages of the method [1] are as follows:

- low stealth due to a significant level of power emitted by a pulsed radio altimeter;

- generation of a correction signal only after the passage of the entire measured area;

- low accuracy of compiling the current map using a single beam, since for measuring height to the studied area, the beam width of the radio waves should be wide enough, while the accuracy of determining the range to individual points on the surface is reduced and, accordingly, the accuracy of compiling the current map is reduced;

- lack of information about the current location of the aircraft in the process of moving over the measured area, since the processing of the measured information is carried out only after the passage of the entire measured area on the correction area.

A known method of autonomous navigation of aircraft [2], partially eliminating the disadvantages of the analogue [1], selected for the prototype.

The implementation of the method [2] is to compile the current map by measuring the parameters of the measured area using radio waves. In this case, the used radio waves for radiation are rays that act on the test surface in sequence, the number of used radio waves is determined by the allowable time to measure the location of the aircraft when moving over the measured area of the test surface (an increase in the number of rays leads to a significant increase in the purchased information per measurement step, which reduces the time of measuring the location of the aircraft).

The location of the aircraft is determined in the planned coordinates of the measured area based on measurements of slant ranges, the correction signal is calculated in accordance with the differential-difference algorithm for processing multipath measurements (DRAOMI).

The disadvantages of the method [2] are as follows:

- low stealth work;

- low speed and accuracy of determining the current location of the aircraft in the process of its movement above the measured area, including movement with increased speeds;

- restrictions on the flight altitude of the aircraft over the measured area.

The reason for the above disadvantages of the method [2] is the sequential transition of radiation and reception of radio waves from one beam to another beam, during which during the emission and reception of one beam of the aircraft moves relative to the reflective surface and as a result, when the radiation and reception of radio waves by other rays, the spot , the range to which is determined, is shifted forward in the direction of flight of the aircraft. This leads to a dependence of the accuracy of determining the current location of the aircraft on the duration of the emitted radio waves and its speed. The residence time of the relief system in the radiation mode during the passage of the measured portion is equal to the total radiation time along the rays, which reduces the secrecy of its operation.

As the aircraft’s flight altitude increases, the requirement for the energy potential of the relief system increases, the implementation of which within the framework of the method [2] while maintaining the pulsed power of the radio waves emitted in each beam is possible only by increasing their duration, but this, as mentioned above, will lead to an increase in the error determine the location of the aircraft above the measured area.

With a decrease in the flight altitude of the aircraft, the requirement for the magnitude of the “dead” zone of the relief system increases, the implementation of which in the framework of the method [2] is possible with a decrease in the duration of the radio waves emitted in each beam and an increase in the rate of transition of the relief system as from the radiation mode of the radio waves to the reception mode of reflected radio waves within one beam, and the transition from one beam to another, which may be a technical problem.

Thus, the sequential transition of radiation and reception of radio waves from one beam to another beam limits the stealth and speed of the navigation method [2], as well as the possibility of increasing the accuracy of determining the location of the aircraft by increasing the number of rays. When flying an aircraft with increased speeds, as well as increasing the altitude of its flight due to an increase in the duration of the emitted radio waves, the errors in determining the location of the aircraft above the measured area increase.

When flying aircraft at low altitudes, the mode of emission and reception of radio waves for each beam, which is the basis of the navigation method [2], limits the range of minimum measured inclined ranges.

The technical result of the invention is to increase the secrecy and speed of the method of navigation of aircraft, as well as the accuracy of determining the location of the aircraft when moving over a measured area, including with increased speeds and with an increase in the range of heights when flying aircraft.

The technical result is achieved by the fact that in the autonomous navigation method of the aircraft, including determining the slant range of the aircraft to the earth's surface, consisting in the emission of radio waves in the form of several rays and the subsequent reception of reflected radio waves from these rays, the radio waves are emitted simultaneously on the same carrier frequency in the form of sequences of radio pulses, the initial phases of which are modulated by M-sequences orthogonal to each other. The reflected radio waves are separated by the rays and the oblique distances of the aircraft to the earth's surface are determined by the correlation method using modulating M-sequences as reference functions or by matched filtering using codes that form modulating M-sequences as weight coefficients.

To determine the location of the aircraft when moving at higher speeds and with a decrease in altitude of its flight, the radio waves emit along several narrow beams, and the reflected radio waves receive along one wide beam.

A method for navigating an aircraft, including, for example, determining the slant range of an aircraft to the earth's surface using three beams in terms of generating emitted radio waves in the form of quasicontinuous sequences of radio pulses whose initial phases are modulated by M-sequences orthogonal to each other and separation of reflected radio waves when they overlap in time, is illustrated by the following drawings:

Figure 1 - the principle of operation of a single-beam relief system;

Figure 2 - the arrangement of the rays of the aircraft relative to the measured portion of the earth's surface for a 3-beam relief system when receiving reflected waves through three rays (a), when receiving reflected waves through one wide beam (b);

Figure 3 - the emitted signal in the form of a quasicontinuous sequence of radio pulses, the initial phases of which are modulated by the M-sequence (duty cycle Q = 3);

Figure 4 - the emitted signal in the form of a continuous sequence of radio pulses, the initial phases of which are modulated by the M-sequence (duty cycle Q = 1);

Figure 5 - orthogonal modulating M-sequence MP1, MP2 and MP3 (initial sections);

Figure 6 - graphs of the autocorrelation functions of the M-sequences of the three rays MP1, MP2 and MP3;

Figure 7 - graphs of the cross-correlation functions of the sequences MP1 and MP2, MP1 and MP3, MP2 and MP3;

Figure 8 - envelope of the total signal of three rays;

Figure 9 - graphs of the correlation functions of the total signal of three rays after highlighting its envelope and reference sequences MP1, MP2, MP3;

Figure 10 - graphs of the correlation functions of figure 8 in the vicinity of the correlation maxima.

The navigation method of the aircraft, including, for example, the determination of the inclined range of the aircraft to the earth's surface by three beams, as follows.

Before the movement of the aircraft, a reference map of the terrain is entered into the on-board equipment, on which the necessary terrain is selected, which is a measured area. A current map is compiled by measuring the parameters of the measuring section using radio waves in the form of three rays.

Rays of radio waves emit, as shown in FIG. 2a, as follows.

Beam 1 has a propagation direction in a plane orthogonal to the horizon plane of the surface under study, beam 2 has a propagation direction on the left in the direction of aircraft movement from beam 1, and beam 3 - on the right in the direction of aircraft movement from beam 1, and all rays are located in one plane. In all the rays, the radio waves emit simultaneously at the same frequency in the form of quasi-continuous sequences of radio pulses with a duty cycle of Q = 3 (Fig. 3), the initial phases of which are modulated by the orthogonal M-sequences MP1, MP2, MP3 (Fig. 5). In beam 1, radio waves are emitted and received in the form of a quasicontinuous sequence of radio pulses, the initial phases of which are modulated by the M-sequence MP1, in beam 2 - MP2, in beam 3 - MP3. The correlation functions of quasicontinuous sequences of radio pulses of all three beams are shown in FIG. 6 and FIG. 7. As can be seen in the graphs of FIG. 6, the autocorrelation functions corresponding to the M-sequences of MP1, MP2, and MP3 have a single maximum whose numerical value is equal to the number of pulses in the M-sequences. Moreover, the cross-correlation functions (Fig. 7) of the considered M-sequences do not have correlation maxima. Thus, from the total sequence, all three M-ray sequences can be separated and identified by a correlation method (Fig. 9). Separation of rays is also possible by a coordinated filtering method equivalent to the correlation method considered above [3], in which codes forming orthogonal M-sequences are used as weighting coefficients.

When the flight altitude decreases, the radio waves in the rays emit in the form of a continuous sequence of radio pulses, the initial phases of which are modulated by the M-sequence (duty cycle Q = 1) (Fig. 4), the reception of reflected waves is carried out along one wide beam, as shown in Fig. 2b, while radiation and reception of radio waves are possible with time overlap. The location of the aircraft is determined on the basis of the slant range measurements obtained using the rays of the radio waves, the correction signal is calculated in accordance with the differential-difference algorithm for processing multipath measurements (DRAOMI), proposed and considered in [2].

As a result, the navigation method allows you to obtain the information necessary to determine the current location of the aircraft and control the movement of the aircraft during the emission and reception of radio waves along one beam, and not during the passage of the entire measured portion of the reference map, as was done in the analogue [1], and not for the total time of emission and reception of radio waves for all beams, as was done in the prototype [2].

Simultaneous radiation in each beam of radio waves in the form of sequences of radio pulses, the initial phases of which are modulated by orthogonal M-sequences, allows, in comparison with the prototype:

- increase the secrecy of the navigation system by reducing the radiation time by N times, where N is the number of rays;

- to ensure the operability of the navigation system with increasing aircraft altitude by increasing its energy potential;

- to ensure the operability of the navigation system while reducing the flight altitude of the aircraft due to the emission of radio waves by narrow beams and the reception of reflected radio waves along one wide beam;

- increase the speed of the navigation system;

- to ensure the accuracy of determining the location of the aircraft when driving at high speeds;

- increase the accuracy of determining the location of the aircraft by increasing the number of rays.

Thus, the method of navigation of aircraft has a number of significant advantages over the prototype and analogue.

Literature

1. Rzhevkin V.A. Autonomous navigation on terrain maps // Foreign Radio Electronics. 1981, No. 10. S.3-28.

2. RF patent No. 2284544. Aircraft navigation method / Khrustalev A.A., Koltsov Yu.V., Ryndyk A.G., Pluzhnikov A.D., Potapov N.N., Egorov S.N .; priority from 05/30/2005.

3. S.V. Katin, V.A. Kozlov, Yu.M. Kulikov, A.L. Kunilov. Design principles for digital processing of airborne radar signals that implement optimal or near optimal algorithms in real time // Physics of Wave Processes and Radio Engineering Systems. Volume 14, No. 2. 2011. S. 53-57.

Claims (1)

The method of autonomous navigation of aircraft, including determining the oblique range of the aircraft to the earth's surface, which consists in emitting radio waves in the form of several rays and then receiving the reflected radio waves through these rays, characterized in that the radio waves emit simultaneously on the same carrier frequency in the form of sequences of radio pulses, the initial the phases of which are modulated by M-sequences orthogonal to each other, the reflected radio waves are separated by rays and the inclined distance is determined of the aircraft to the earth's surface in a correlation way using modulating M-sequences as support functions or by a coordinated filtering method using weight codes of codes forming modulating M-sequences.

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