RU2684710C1 - Aircraft ins errors correction system by the area road map - Google Patents

Abstract

FIELD: instrument making.SUBSTANCE: invention relates to the field of navigational instrument making and can be used for the aircrafts (AC) flight and guidance by the underlying surface remote probing actual data comparison with the area road map and is intended for use on board of manned and unmanned aircrafts, cruise missiles, etc. using the self-contained information source, for example, radar altimeter (RA) or other radar, for example the front hemisphere scanning radar, to perform the inertial navigation system (INS) measurements correction. Technical results is achieved due to the radar irradiation of the underlying surface and the reflected signals reception along the flight path longitudinal axis; – surface type histogram and correlation selection calculation (change of the surface type corresponds to the road map landmarks); – updating the landmarks borders position and forming a picture (the surface types values array along the flight path or in the given scanning area) of the underlying surface actual remote probing data; – this picture comparison with the road map (reference); – INS readings corrections based on the portraits correlation comparison results.EFFECT: technical result is increase in the AC navigation accuracy, including under conditions of the low-relief underlying surface.1 cl, 1 dwg

Description

The invention relates to radio engineering, more precisely, to radio navigation and can be used for flight and guidance of aircraft (LA) by comparing real data of remote sensing of the underlying surface with a road map of the area and is intended for use on board manned and unmanned aircraft, cruise missiles, etc. . using an autonomous information source, for example, a radio altimeter (PB) or another radar, for example, a front hemisphere radar, for correcting measurements of the inertial navigation system (INS).

A common problem with the use of inertial navigation systems is the specifics of its work, which leads to the appearance and accumulation of errors in determining the position of aircraft that may become unacceptably large over time, therefore the resulting flight path will differ significantly from the target or planned flight path in the absence of correction.

The invention relates to the class of correlation-extreme navigation systems (CENS), designed to correct information data of the onboard INS by comparing (comparing) the detected radio-contrast [1] landmarks (i.e., differing in level and / or statistical characteristics during vertical or oblique sounding) with a reference road map of the area obtained in advance (aerial photography, satellite, geodesic, etc.).

Satellite navigation systems are widely known, which in most cases provide high accuracy in determining coordinates and other navigation parameters for correcting the flight path of an aircraft. The disadvantage is that they are not autonomous, which means that they do not provide sufficient stability of the correction of the aircraft trajectory under conditions of natural and / or artificial interference.

Also widely known are optical systems, including astrocorrection of the flight path, both manual (on strategic bombers and on ships) and automatic (on ballistic missiles), for example, the optical correlation system [2]. The disadvantage of such systems is that they do not work in conditions of poor visibility (with the exception of ballistic missiles).

The most effective known means of correcting the accumulated errors is the use of geophysical field sensors [3], which ensure the collection of information during the flight of the aircraft. At the same time, a correlation-extremal approach is used, which is based on a comparison of the obtained field measurements with a priori (reference) information about it stored in the onboard computer memory.

Informative geophysical fields can be magnetic, gravitational fields, relief, optical, radiothermal or radar brightness.

The theory of extremal correlation navigation systems began to be dealt with in the late 60s - early 70s, and the term was first introduced by Academician of the Academy of Sciences A.A. Krasovsky, [4]. The theory of navigation in geophysical fields in the Russian Federation is well established in [1], [3] and [5], and among foreign authors in [6].

The practical application of ANS error correction in LA was developed somewhat later. For example, the correction of deviation errors of the real flight path from the given one is currently carried out by the following systems:

- Infrared Correlation System [7]

- Passive radiometric correlator [8]

- Personnel correlation-extreme navigation system [9]

- Navigation system for the Earth’s magnetic field [10]

- The system for determining the location of low-flying aircraft on the profile ahead of the terrain [11]

- Search engineless terrain navigation system [12]

The “Active Correlation System” developed by Goodyear Aerospace for solving problems of navigation and guidance, called ROC (Range-Only Correlation), is based on the principle of correlation along the line [13].

The system determines the position of a moving object according to the time of the reflected radar pulses generated in four symmetrical directions and vertically. In the processor, the high-speed correlator solves the problem of determining the coordinates of the aircraft by comparing the processed reflected pulses with the corresponding data of the reference maps. The information received is fed to the INS for the correction of the navigation system. The irradiated area is 5 × 10 km. Disadvantage: the use of special radar with a high power and memory calculator.

The “Donnell-Douglas (United States) Combined Terrain Contour Navigation System for the Torahawk Terror Contour Matching TERCOM [14]) is known, in which the system measures the vertical profile of the terrain along the true flight path using RV for measuring the geometrical flight altitude) and the barov altimeter (for obtaining the absolute flight altitude). Subtracting a certain height, measured by the RV, from the barometric one, the system determines the profile along the flight trajectory and organizes a search in the computer’s memory of the most “similar” previously recorded profiles to the road map.

When in the system of the closest profile, the true position of the aircraft is determined, and this information is used to correct the trajectory. Disadvantages: complex algorithm of work, requires a large amount of memory and high CPU performance, because An overview of the terrain is conducted forward / backward, then across the flight path, and these are 30 × 30 m long and 240 × 240 m across). The system is not corrected for speed and angular position.

The advanced algorithm of CENS over the field of relief was implemented in the SITAN system (Sandia inertial navigation system) [12, 15]. In the first case, the Kalman filter is used instead of the correlator, which processes the navigation data of the relief field with the subsequent formation of hypotheses about the location of the aircraft.

Disadvantages: complex information processing is also necessary, besides careful selection of Kalman filter coefficients for each type of relief is necessary.

The next step in the use of empirical terrain data obtained in the VATAN system [16], instead of the Kalman filter, it uses the Viterbi algorithm, which runs faster than the algorithm in the SITAN and TERCOM systems by applying fast Monte-Carlo and Viterbi algorithms. A plus is also a more complete use of empirical data. Disadvantage: it is still a very complex algorithm, in addition, all relief navigation systems do not work with areas of a mellerefacular surface.

Thus, the solution of the navigation problem and the accuracy of its solution depend on the type of geophysical field used. Therefore, in practice, none of the well-known CENS systems makes it possible to completely solve the problem of navigation in the whole range of possible application conditions for various geophysical fields.

The closest technical solution is to use the Honeywell (USA) AN / APN - 197 radio altimeter for correcting the INS, which is designed to measure (together with signals from the vertical accelerometer and barometric altimeter) the relief field on board the Tomahawk cruise missile. Characteristics of PB are given in [17]. Disadvantages: the use of such a system for supersonic cruise missiles (for example, of the “Caliber” type, the Russian Federation) is problematic, since much more computational power, memory size and increase in weight and size characteristics will be required to obtain acceptable accuracy characteristics.

The most promising direction for authors is the use of a radio contrast field based on comparing a digital roadmap of landmarks of a flight with remote sensing data observed by real-time radar sensors. With a low-relief surface, the radio contrast field retains informational content due to the availability of infrastructure facilities (road and rail network, bridges, pipelines, etc.), as well as natural landmarks (rivers, lakes borders, fields, forests, etc.).

An object of the invention is to improve the accuracy of navigation of the aircraft, including the most important in the conditions of low-relief underlying surface.

The technical result is achieved due to:

- irradiation of the radar surface of the underlying surface and reception of reflected signals along the longitudinal axis of the flight path;

- calculation of the histogram and the correlation selection of the surface type (the change of the surface type corresponds to the landmarks of the road map);

- clarify the position of the boundaries of landmarks and the formation of a portrait (an array of values of surface types along the flight path or in a given scanning area) of real remote sensing data of the underlying surface;

- comparison of this portrait with a road map (benchmark);

- adjustments of the indications of ANN according to the results of correlative comparison of portraits.

To solve this problem, an error correction system for aircraft navigation on a terrain roadmap containing an inertial system with an LA coordinate calculator, a radio altimeter / radar, a terrain roadmap and an error correction circuit, characterized in that the error correction circuit contains the following nodes and blocks: amplitude detector, height normalization unit, histogram calculation unit, template database unit, surface type selection correlator, boundary position refinement unit, classification torus of the extended object type, surface type selector, correlator, adder, correction signal generator, correction resolution block, correction resolution synchronizer with the following connections: radio altimeter / radar 1 by the received reflected signal is connected through the amplitude detector 3 to the height 3 and the signal the gain is connected to the second input of the normalization unit in height 3, and a signal to the height of the third input of the normalization unit in height 3 and to the first input of the classifier length wennogo object 8; the output of the normalization block for height 3 is connected via the histogram computing unit 4 to the first input of the surface type selection correlator 6, the second input of which receives a signal from the first output of the database of the standards database 5, the output of the correlator of the surface type selection 6 and the second output of the database of the standards 5 served on the unit for specifying the position of the boundaries 7, the output of which is fed to the second input of the classifier of the extended object type 8 and the first input of the correlator 11, the probabilistic output of which is connected to the first input of the resolution synchronizer correction 17 to the second input of which is connected classifier type extended object 8; the first data output of the INS 15 through the coordinate transmitter 12 is connected to the first input of the adder 13; the signal from the output of the correction signal shaper 14 is fed to the adder 13 and the first input of the correction resolution block 16, to the second input of which a signal is sent from the correction resolution synchronizer 17, and the output of the correction resolution block 16 is connected to the input of the INS 15, which in turn the second signal output the horizontal speed of the aircraft is connected to the third input of the classifier of the type of an extended object 8; the outputs of the adder 13 and the roadmap of the area 9 are fed to the inputs of the selector type surface 10, the output of which is connected to the second input of the correlator 11; the output of the transmitter coordinates LA 12 is also issued in the control system of the aircraft.

FIG. A block diagram of the INS error correction system of the aircraft is shown according to the road map of the area, which shows:

1) radio altimeter (PB) or other radar;

2) amplitude detector (BP);

3) block normalization in height;

4) histogram calculation unit;

5) block database of standards;

6) the correlator of the choice of the type of surface;

7) a block for clarifying the position of boundaries;

8) classifier type extended object;

9) road map of the area;

10) surface type selector;

11) correlator;

12) calculator coordinates LA;

13) adder;

14) correction signal generator;

15) inertial navigation system (INS);

16) correction resolution block;

17) correction resolution synchronizer.

The system of correction of the trajectory of the aircraft according to the roadmap of the area works as follows.

From the radio altimeter or radar (probing at an angle to the nadir) the reflected signal enters the amplitude detector, which calculates the value of the amplitude of the signal in real time. Further, using information about the altitude and the gain from the RV, the amplitude value is normalized to the flight altitude in the normalization block in height. During the flight, information about the amplitude is accumulated and a histogram of the amplitude of the reflected signal is generated from the accumulated amplitude values. Further, the histogram is normalized to a unit area. After the formation of the first histogram, it is calculated in real time continuously as the amplitude information arrives.

From the database of standards templates, the histograms of standards are fed to the correlator of the type of underlying surface. Here, the current histogram is compared with the reference, the area of histogram intersection is calculated. If no surface type has exceeded the minimum threshold, zero is output. At the output of the correlator of the underlying surface type - the type of surface (numerical identifier). In the case of changing the type of underlying surface information about the underlying surface is fed to the input of the block to clarify the position of the boundaries. Information on offset errors (defined in the pattern database block for each combination of typical underlying surfaces) is also received in this block to eliminate the offset error. Information from the output enters the classifier of the type of an extended object, which determines that the “border” or “strip” was crossed for the object depending on the width of the extended object and whether there was any movement of the aircraft (according to the speed of the aircraft with the ANN). The width of the extended object is estimated by the time between readings and the speed information obtained from the INS. This information is also fed to the input of the correlator, which compares the existing sequence of types of underlying surfaces with the sequence obtained from the selector of the type of underlying surface.

Information from the INS enters the calculator coordinates LA, which is implemented as part of the onboard calculator. From the output of the calculator information enters the adder. From the adder, information enters the underlying surface type selector, which forms a sequence of underlying surface types for the current hypothesis of the aircraft's trajectory (position), taking into account information about all previous values of the underlying surface type accumulated during the flight.

The correlator compares the current sequence of types of underlying surfaces with that obtained from the selector of the type of underlying surface. From the output of the correlator, the coincidence probability value arrives at the correction signal generator, which calculates the coordinate error for the sequence of types of underlying surfaces, specifies the position of the current sequence by forming hypotheses about the position (shift of coordinates) of the aircraft. Next, the error in the coordinates goes to the adder, which shifts the position of the sequence of typical underlying surfaces to test the following hypothesis. The correction resolution synchronizer, in case of exceeding the threshold for the coincidence probability value, generates a correction resolution signal, as a result of which the value of the aircraft coordinate mismatch error (specified as a result of the above hypothesis test) is transmitted to the INS. In the case of a small value of the coincidence probability, the second synchronizer input signal from the classifier is used, which changes the threshold value according to the results of estimating the width of extended objects in the classifier of extended objects.

Refined as a result of the operation of the error correction scheme, the coordinate values are given to the aircraft control system [3].

The system for correcting the trajectory of the aircraft can be implemented on a calculator, for example, 1879 VMS. Typical radio altimeter A-078 can be used in the correction system.

The radio altimeter system A-078 provides dynamic tuning of the received signal power values within 135 dB, which corresponds to a height change of 2371 times (the signal level changes proportionally to 1 / R ⁴ ), for example, from 5 m to 11 thousand meters. To save information about height is enough to use a 12-bit ADC.

We introduce the following notation:

C - comparison operation;

P - multiplication operation;

And - addition operation;

S is an operation of choice.

Estimate of the required speed (for LA speeds of 300 m / s, frequency of receiving information on the amplitude 300 samples / sec, flight range of 300 km, density of landmarks 40 pcs / 100 km, full recording of surface types 10 km for the underlying surface type selector and 1 km for the unit to clarify the position of the boundaries, and in abbreviated form (length-type of surface) for the entire flight) showed that the most demanding in terms of resources the block is the underlying surface type selector (10 ⁶ (S + A) operations and 1 MB of memory), then boundary position adjustment block (1 01 KB of memory and about 10 ⁵ (S + 2A) operations) correlators (200 bytes of memory and 10 ⁴ (2S + 4A) + 100Р operations, and 7⋅10 ⁴ (P + C + A) + C + 6A + 70S) operations and (10.5 + 1) Kbytes of memory, respectively), as well as a block for constructing histograms (1 Kbytes of memory and 340 (7C + 1A) + 7A + 7P operations). The remaining blocks require a small amount of resources. Thus, without overhead, less than 210 ⁶ (S + A) + 10 ⁵ P operations and 2 MB of memory will be required. Since half of the time the processor is busy with internal tasks, then taking into account the overhead (about 300% extra), it is necessary to ensure the speed of 16 mln.op / sec. Taking into account optimization, parallelization and reduction of overhead costs, the required resource can be reduced by a factor of four and more. But even without taking into account the optimization of modern high-speed signal processors, for example, 1879 VM3 are able to provide the required resource.

Thus, the construction of the system according to the proposed scheme allows to ensure high accuracy of the correction of the coordinates of the flight of the aircraft in a low-relief landscape, and, as a result, to improve the accuracy of navigation through the use of an extended list of navigation landmarks.

In summary: this system complies with the basic economic law: “cost-effectiveness”.

List of used sources

1. Kondratenkov, G.I. Radio vision. Earth remote sensing radar systems / GI Kondratenkov, A.Yu. Frolov. - M .: Radio Engineering, 2005. - 368 p.

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4. Krasovsky, A.A., Beloglazov, I.N., Chigin, G.P. Theory of correlation extremal systems, M., Nauka, 1979.

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Claims (1)

An INS error correction system of an aircraft according to a roadmap of a terrain containing an inertial system (INS) with an aircraft coordinate transmitter (LA), a radio altimeter / radar, a terrain roadmap and an error correction circuit, characterized in that the error correction circuit contains the following nodes and blocks : amplitude detector, height normalization unit, histogram calculation unit, standard database block, surface type selection correlator, boundary position refinement block, extended length type classifier object, surface type selector, correlator, adder, correction signal conditioner, correction resolution block, correction resolution synchronizer with the following connections: radio altimeter / radar received echo signal through the amplitude detector with the first input of the normalization block, gain signal with the second input block normalization height, and the signal height - with the third input of the block normalization height and the first input of the type of extended object type; the output of the normalization block in height is connected through the histogram computing unit to the first input of the surface type selection correlator, to the second input of which a signal is sent from the first output of the standards database block, the output of the surface type selection correlator and the second output of the standards database block to the boundary position refinement unit , the output of which is fed to the second input of the classifier type of an extended object and the first input of the correlator, the probabilistic output of which is connected to the first input of the synchronizer of the correction resolution , The second input of which is connected to an extended object type classifier; the first output of the INS data through the coordinate transmitter is connected to the first input of the adder; the signal from the shaper output of the correction signal is fed to the adder and the first input of the correction resolution block, to the second input of which a signal is sent from the correction resolution synchronizer, and the output of the correction resolution block is connected to the INS input, which in turn is connected to the third output of the horizontal speed signal LA the input of the classifier type extended object; the outputs of the adder and the roadmap of the terrain are fed to the inputs of the surface type selector, the output of which is connected to the second input of the correlator; the output of the transmitter coordinates of the aircraft is also issued in the control system of the aircraft.

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