RU2564552C1 - Navigation method of airborne vehicle as per radar images of earth surface - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: result of the invention is achieved by formation in flight of an airborne vehicle (AV) of a radar image of the earth surface in a "slant range - Doppler frequency" coordinate system, conversion of this image to a set of radar images (RI) in the normal earth system of coordinates considering a priori formed corrections to the data on AV flight altitude, which is calculated by a navigation complex of the airborne vehicle, and further mutual correlation processing of formed RI with the reference (standard) radar image prepared in advance.

EFFECT: improving probability of correct determination of position of airborne vehicles as per radar images of the earth surface and enlarging conditions of possible application of onboard radar aids of airborne vehicles, which provide a possibility of navigation of airborne vehicles as per radar images of the earth surface.

5 dwg

Description

The invention relates to radar, in particular to airborne radar navigation aids (LA), providing in flight LA radar images (RLI) of the earth's surface and the comparison of these images with pre-prepared reference (reference) images.

Comparison of the (working) radar images obtained in flight with the reference ones is associated with the search for the maximum of some two-dimensional function, which reflects the mutual correlation of the reference and working radar images. The coordinates of this maximum, determined by changing the relative relative positions of the working and reference radar images, form estimates of the coordinates of the aircraft.

There is a method described in [1], according to which an airborne radar system (radar), which is part of the airborne control system of an unmanned aerial vehicle (UAV), using an antenna scan, looks through the space in the horizontal plane:

in front of the UAV (in the mode of bringing the UAV to a radio-contrast object);

from the zero position of the antenna, which coincides with the firing plane, to the extreme angular position of the measurement sector (in the mode of bringing the UAV to a non-radio contrast object).

During the review process, an array A (i, j) of measurements of radar signals is formed, with assignment to each array element of the corresponding value of the angle of rotation Ψ _i of the antenna and the range D _j corresponding to the measured reflected signal.

Further, this array is subjected to correlation processing by comparing the measured array with sequentially sorted binary sequences B (i, j) of fragments of a previously prepared reference map.

The results of this processing determine the location of the measured array on the reference map, the longitudinal axis of which is oriented along the firing plane. The offset of the near left portion of the surface where the reflected signal is measured relative to the lower left point of the reference map determines the errors in bringing the UAV to a given point at a distance of measurement.

The disadvantage of this method is that the azimuthal resolution of the generated radar image is determined by the width of the radiation pattern of the antenna of the radar coordinator, which does not allow for a sufficiently accurate "binding" of the resulting radar image to the standard. In addition, the conversion of polar coordinates (Ψ _i , D _j ) to rectangular (XOZ) is carried out by simply reassigning the numbers (i, j) of the array A (i, j) to the numbers of linear coordinates X and Z, which also significantly reduces the accuracy of navigation calculations mistakes.

This method has a significant difference from the proposed, consisting in the fact that the proposed method uses radar with the synthesis of antenna aperture (CAP).

There is a method described in [2], according to which the estimate of the planned navigation errors of the aircraft (LA) is obtained by assessing the position of the maximum of the two-dimensional cross-correlation function (CCF) of the reference (reference) and working (obtained in flight) radar images (RLI) specified (reference) area.

Before receiving a working radar, in order to reduce the amount of calculations during digital processing of a signal of a working radar and reduce the likelihood of an incorrect exposure of the antenna in elevation at the point of correction of the aircraft trajectory when scanning the antenna of the airborne radar sensor, the following procedures are performed:

- estimates of the vector of the aircraft’s own speed according to the known algorithm [3];

- estimates of the average elevation angles of bright points on the radar image generated during the scanning process, which determine the average aircraft height relative to these bright points;

- a calculated estimate of the aircraft altitude above the terrain in the vicinity of the priority point of a given terrain by averaging the heights of the “bright” points over the set of partial radar images.

The reference radar image is calculated in the polar coordinate system (inherent in the radar sensor) for each correction point.

The reference radar image is an Aet matrix of the power of the signals “reflected” from elementary areas and located at the nodes of the polar coordinate grid.

The coordinate grid of the reference radar image is formed in the specified polar coordinate system within the specified range strobe boundaries Rmin and Rmax of the radar sensor and the boundaries of the terrain viewing sector in the azimuth of Bbeg and Bend.

The working radar image of a given area is formed using the fast Fourier transform (FFT) and incoherent processing of the working radar frame also in the polar coordinate system.

The inter-correlation function of the reference and working radar data obtained using CAP is calculated by the coordinates of the points of the standard relative to each point of the working radar data (relative positions).

Given the possible discrepancy between the two radar data according to the angle of rotation, when calculating the cross-correlation, the most probable angle of rotation of the standard radar image is searched. The procedure for calculating and searching for the maximum VKF is repeated for a given (test) set of angles of mutual rotation of the radar image. In this case, the selection of the largest maximum VKF is made.

Then, with the specified parameters of the correlation comparison, the mutual linear shift of two radar images is calculated, as well as the magnitude of the mutual angular shift of these radar images.

However, this method has the following disadvantages.

1. The azimuthal angular size of the radar images of the observation object, formed in the coordinate system "range - azimuth", changes when changing the range to this object. For example, the observed correction section with a transverse length of 1 km when observing from a distance of 5 km has an angular width of 11.42 degrees, and from a distance of 6 km - 9.53 degrees.

Thus, in the presence of unknown planned errors of the aircraft’s withdrawal to the start point of the survey of a predetermined (reference) site of the terrain (the point of formation of the radar image [2]), it is possible to obtain radar images of this site, significantly different azimuthal sizes, which complicates their subsequent correlation processing with the prepared radar standard.

2. The shift of the real position of the point of formation of the working radar relative to the calculated position used in the formation of the standard leads to a reversal of the working radar relative to the reference, which also complicates the subsequent cross-correlation processing of radar images. For example, with a lateral displacement of the real position of the point of formation of the working radar relative to the calculated one by 500 m, a distance to the object of observation of 5 km and an azimuthal deviation of the direction of sighting of a given area in the SAR mode from the direction of the speed vector of 15 degrees, the turn of the working radar relative to the calculated will be 9.5 hail.

To eliminate this effect, the known method involves obtaining estimates of the maximum VKF using enumeration of the standard radar image, rotated by predetermined angles.

3. The possibility of changing the flight parameters of the aircraft during the formation of the working radar frames, including the horizontal and vertical components of the flight speed of the aircraft, flight altitude, is not taken into account. These components are closely related to the magnitude of the Doppler frequencies of the signals reflected by the elements of the observed area, based on the estimates of which the working radar

The closest in technical essence analogue (prototype) of the proposed method is the method described in [4].

In accordance with this method, the error estimation of the planned navigational coordinates of the aircraft (LA) is carried out at the correction point by comparing the (working) radar images obtained in flight with the reference (reference) images using the calculation of the maximum of the two-dimensional function that reflects the cross-correlation of the reference and working radar images . Based on the position of the indicated maximum, found when the relative relative positions of the working and reference radar images are changed, estimates of the coordinates of the aircraft relative to the known (reference) site are formed.

The formation of both the reference (reference) and the working radar images, as well as their inter-correlation processing, is carried out in a normal earth coordinate system (NSC) associated with a given (reference - OUM) terrain, and to ensure the formation of working radar in the NSC CAM at each correction point carried out:

determination of the values of corrections ΔV _x , ΔV _y , ΔV _z , Δy _la to the estimates of the flight parameters (components of the aircraft’s flight speed and altitude in the NSC) formed by (reckoned) on-board navigation system (NC), for example, an inertial aircraft system (these amendments, then when forming the frames of the working radar sensors, they are summed up with the current calculated values of the flight parameters of the aircraft coming from the aircraft of the aircraft, while the formation of updated estimates of the current values of the trajectory parameters of the flight of the aircraft);

the formation of the frames of the primary working radar images of the OUMA region in the coordinate system "Doppler frequency - slant range";

the formation of a working radar in the normal Earth's OUM coordinate system based on the primary working radar, taking into account the previously determined values of corrections to the current values of the trajectory parameters of the flight, formed (reckoned) by the aircraft navigation system;

cross-correlation processing of the reference (reference) and operational RLM OAM in the NSC OUM and determination of corrections (Δx _la , Δz _la ) of the planned coordinates (x _la , z _la ) of the aircraft relative to a given point on the OUM.

When considering the advantages and disadvantages of the prototype, it should be noted the relative simplicity of the formation of the amendments ΔV _x , ΔV _y , ΔV _z to the estimates of the values of the components of the flight speed of the aircraft [3] and the difficulty of obtaining accurate estimates, including accurate measurements of the flight height of the aircraft that arise when forming the amendments Δy _la , especially at high flight altitudes. In the case of measuring flight altitude using radio altimeters, these difficulties are determined by the presence of a varying terrain over which the flight is carried out. In addition, when forming the working radar in the NSC, the value of the flight altitude of the aircraft should not be used above the underlying surface, but relative to the reference areas of the terrain (OUM), offset from the projection of the flight path of the aircraft on a horizontal plane. Obtaining such relative estimates on board an aircraft is possible using pre-prepared data of reliefmetry or a single pulse of an airborne radar [5]. However, the resulting accuracy of such estimates is small.

The technical result of the invention is to increase the likelihood of a correct determination of the position of the aircraft from the radar images of the earth's surface and to expand the conditions for the possible use of airborne radar means of the aircraft, allowing navigation of the aircraft on the radar images of the earth's surface.

, формируемых в НЗСК в полете для априорно задаваемой совокупности {y_ла=Y_n}, $$n=\overline{\mathrm{1,}N}$$

расчетных значений высоты полета ЛА.Distinctive features of the proposed method from the prototype is that the assessment of the planned navigation errors Δx _la , Δz _la ) of the aircraft navigation system is formed by determining the maximum of the functional of the form Ф [F [J _ОП (x, z), J _P (x, z / y _la ))], which characterizes the change in the maximum value of the function F (J _op (x, z), J _P (x, z / y _la )), such as a cross-correlation one, reflecting the similarity of the reference REL OUM J _OP (x, z ) and a number of working radar sensors ОУМ {J _P (x, z / y _la = Y _n )}, $$n=\overline{\mathrm{one,}N}$$

formed in NZSC in flight for a priori set {y _la = Y _n }, $$n=\overline{\mathrm{one,}N}$$

the calculated values of the aircraft flight altitude.

In addition, the proposed method allows for additional correction of the planned navigation coordinates (x _la , z _la ) of the aircraft, when it seems possible to implement the subsequent high-precision measurement of the height of its flight, for example, when reducing the aircraft.

To determine the effect of errors in estimating the flight altitude of an aircraft on the results of evaluating its navigation (planned) coordinates by OAM using radar with CAP, as in the prototype, we will consider the navigation of aircraft in a normal earth coordinate system. The origin of this coordinate system is for convenience compatible with some reference point (OT) on the OUMA (Fig. 1).

In this SC, the OY axis is directed upward along the local vertical passing through the reference point (OT) to the OUMA. The OX axis is perpendicular to the OY axis. The OZ axis complements the coordinate system to the right.

The direction of the OX axis is determined by the conditions of the problem in which the aircraft is navigated. In particular, the OX axis can be directed, for example, to the north, or it can belong to the vertical plane that belongs to the launch point of the aircraft and from the OUMA, or coincide with the planned (calculated) azimuthal direction of sighting FROM the reference area, along which the trajectory should be corrected flight LA.

In the NWCC under consideration, the coordinates of each element of the OUMA corresponding to the ith element of the generated working radar image are determined by the following relations.

Where:

x _la , z _la - estimates of the current planned coordinates of the aircraft in the NSC, formed (reckoned) according to the onboard navigation system of the aircraft;

- оценка горизонтальной дальности от ЛА до элемента наблюдаемого участка местности, соответствующего i-му элементу рабочего РЛИ, формируемого бортовой радиолокационной станцией (БРЛС) ЛА с использованием CAP; $$D_{g_i}$$

- assessment of the horizontal distance from the aircraft to the element of the observed area corresponding to the i-th element of the working radar generated by the aircraft’s on-board radar station (CRL) using CAP;

- оценка азимутального угла визирования элемента ОУМ, соответствующего i-му элементу рабочего РЛИ, формируемого БРЛС с CAP, относительно азимутального направления путевой скорости ЛА; $${\varphi }_{g_i}$$

- assessment of the azimuthal viewing angle of the OUM element, corresponding to the i-th element of the working radar, formed by radar with CAP, relative to the azimuthal direction of the ground speed of the aircraft;

- оценка угла между осью ОХ НЗСК ОУМ и азимутальным направлением визирования элемента ОУМ, соответствующего i-му элементу формируемого рабочего РЛИ; $${\beta }_i={\varphi }_{g_i}+\Psi$$

- assessment of the angle between the axis OX NZSK OUM and the azimuthal direction of sight of the element OUMA corresponding to the i-th element of the generated working radar;

Ψ is an estimate of the angle of the aircraft path.

, $${\varphi }_{g_i}$$

, оцениваемых на основе первичных радиолокационных изображений земной поверхности, формируемых БРЛС с CAP в полете в системе координат «доплеровская частота - наклонная дальность», справедливо:For quantities $$D_{g_i}$$

, $${\varphi }_{g_i}$$

evaluated on the basis of primary radar images of the earth's surface, formed by radar with CAP in flight in the coordinate system "Doppler frequency - slant range", it is true:

Where

R _i - assessment of the slant range from the aircraft to the element of the OUMA corresponding to the i-th element of the generated working radar;

- оценка угла места элемента ОУМ, соответствующего i-му элементу формируемого рабочего РЛИ; $${\epsilon }_i=-\arcsin \left(\frac{h_i}{R_i}\right)$$

- assessment of the elevation angle of the OUM element corresponding to the i-th element of the generated working radar image;

h _i = H _la -H _i - assessment of the flight altitude of the aircraft relative to the element of the OUMA corresponding to the i-th element of the generated working radar;

H _la - estimate (reckoned) of the absolute flight altitude of the aircraft;

H _i - assessment of the absolute height of the element OUMA corresponding to the i-th element of the generated working radar;

- оценка скорости сближения ЛА с элементом ОУМ, соответствующим i-му элементу формируемого рабочего РЛИ; $$V_{r_i}=\frac{F_{d_i}\lambda }{2}$$

- assessment of the speed of approach of the aircraft with the element of the OUMA corresponding to the i-th element of the generated working radar;

- доплеровская частота, соответствующая i-му элементу формируемого рабочего РЛИ; $$F_{d_i}$$

- Doppler frequency corresponding to the i-th element of the generated working radar;

- оценка путевой (горизонтальной составляющей) скорости полета ЛА; $$V_g=\sqrt{V_x^2+V_z^2}$$

- assessment of the track (horizontal component) of the flight speed of the aircraft;

V _x - estimate of the projection of the flight speed of the aircraft on the X axis;

V _z - estimate of the projection of the flight speed of the aircraft on the Z axis;

λ is the wavelength of the probing radar signals.

Given the fact that

from (4) and (5) we obtain

ф

f

Where:

The above expressions relate the estimates of the planned coordinates of the OUM element corresponding to the ith element of the operational radar generated by the radar of the aircraft, with the values of the trajectory parameters (x _la , h _i , z _la , V _x , V _y , V _z ) of the flight of the aircraft.

As is known [6], the error values of the parameter estimation p = f (q ₁ , q ₂ , ..., q _N ) as a function of the measured coordinates q ₁ , q ₂ , ..., q _N for small deviations Δq ₁ , Δq ₂ , ..., Δq _N can be determined using the full differential formula

- оценка координаты q_n.Where $${\stackrel{\wedge }{q}}_n$$

- estimate of the coordinate q _n .

In relation to the problem under consideration, estimates of the values of the components of the aircraft flight speed can be obtained with very high accuracy [3]. In this regard, we further restrict ourselves to considering the influence on the formation of radar data of only navigation errors of the aircraft in position.

Assuming that the airborne radar also determines with high accuracy the oblique ranges and Doppler frequencies of the reflected signals, for errors in determining the coordinates of the elements of the generated operational radar in the NSC OUM using the full differential formula from (8) and (9) we obtain

Where

- sensitivity coefficients of the planned coordinates of the elements formed in the NSC of the working radar (x and z) to errors in estimating the current relative flight altitude of the aircraft;

From (12), (13), the current corrections to the planned navigation coordinates of the aircraft, determined relative to the reference point of the OAM

where Δy _la = Δh _OT , the error in estimating the flight altitude of the aircraft (y _la = h _OT ) in the NSC OUM.

The values of Δx _OT , Δz _OT , as described above (see (1)), are determined using the maximum estimate of the function F (J _OD (x, z), J _P (x, z)), which reflects the measure of mutual correlation of the reference J _OD (x, z) and working J _P (x, z) radar images in the NSC OUM.

It can be seen from expressions (12), (13) that the planned errors (Δx _la , Δz _la ) of calculating the coordinates of the aircraft in the NSC OUM lead to the same displacements of all elements of the generated working radar image and do not entail its distortion and reversal.

, соизмерима с V_g).From the same expressions it is seen that the influence of the relative errors of the aircraft output to the OUM sighting point in height (Δh _i ) on the planned errors (Δx _i , Δz _i ) of the estimates of the coordinates of the OAM elements is nonlinear and increases with increasing ratio h _i to R _i , the growth of the modulus of the altitude of the flight altitude (V _y ) of the aircraft during the formation of the working radar, as well as in the conditions of the anterolateral view (when the speed of approach of the aircraft with the elements of the OUMA, determined by the ratio $$V_{r_i}=\frac{F_{d_i}\lambda }{2}$$

is commensurate with V _g ).

In FIG. 2a) an image is shown in the NSC of the test OAM, which includes 9 radar reflectors located on the XOZ plane and located at a distance of 500 meters from each other. The reference point of the OUM (center NZSK) is combined with the central reflector.

In FIG. 2b) marks are shown that correspond to the actual position of the indicated radar reflectors and marks (cruciform) obtained as a result of the formation of the corresponding operational radar image in the NSC OUM with the following flight parameters:

range to OT OUM - 5000 m; aircraft flight speed - 250 m / s; aircraft acceleration (braking) - minus 4 m / s ² ;

aircraft speed vector direction

in the vertical plane - minus 30 °; LAS path angle (Ψ) - 20 °;

the angle between the axis OX HZSC OUM and the azimuthal

OT direction of sight (β _OT ) - minus 1 °;

errors in calculating the coordinates of aircraft

along the X and Z axes in NZSK OUM - 400 m.

In FIG. Figure 3 shows the marks corresponding to the actual position of the indicated radar reflectors, and the marks obtained as a result of the generation of working radar images in the NSC OUM for the above, flight conditions of the aircraft at values:

errors in calculating the coordinates of the aircraft along the axes X and Z in HZSC OUM - 0m;

errors calculating the coordinates of the aircraft along the Y axis H HSC OUM:

minus 250 m - (figure Fig. 3a); plus 250 m - (Figure Fig. 3b).

From FIG. Figure 3 shows that, under the indicated flight conditions of the aircraft, errors in estimating the current flight altitude of the aircraft lead to a significant shift and distortion of the operational radar data generated in the NSCS OUM.

The indicated distortions can be so great that the possibility of interlinking the supporting and working radar data can be called into question.

These radar image distortion decreases as the errors in estimating the current aircraft altitude tend to zero.

It should be noted that in the case when OAM is monitored with elements of different heights, when forming a working OAM radar in HSC for different (i ≠ j) OUM elements, we have to assume: h _i = h _j . Usually taken h _i = h _j = h _OT = y _la, where h _OT - altitude aircraft flight relatively FROM OUM.

In this case, for the conversion of the primary working radar from the coordinate system "Doppler frequency - slant range" in the ZSC OUM can use the following expressions:

Where:

Obviously, in this case, the displacement of the OUM elements relative to the XOZ plane in height (y _i ≠ 0) is equivalent to the presence of corresponding errors in determining their relative heights h _i . These errors entail the planned distortion of the working radar in the NZSC, formed using (19), (20). However, these distortions are predictable and can be taken into account when constructing reference radar data.

, формируемых в НЗСК в полете для априорно задаваемой совокупности {y_ла=Y_n}, $$n=\overline{\mathrm{1,}N}$$

расчетных значений высоты полета ЛА.Reducing the radar image distortion generated in flight, when the error in estimating the flight altitude tends to zero, determines the feasibility of updating estimates of the aircraft’s planned coordinates (x _la , z _la ) by determining the maximum of the functional of the form Ф [F (J _ОП (x, z), J _P (x, z / y _la )), which characterizes the change in the maximum value of the function F (J _ОP (x, z), J _P (x, z / y _la )), such as cross-correlation, which reflects the similarity of the reference RMI of the OAM J prepared in advance in the NSC _OP (x, z) and a number of working radar sensors OUM {J _P (x, z / y _la = Y _n )}, $$n=\overline{\mathrm{one,}N}$$

formed in NZSC in flight for a priori set {y _la = Y _n }, $$n=\overline{\mathrm{one,}N}$$

the calculated values of the aircraft flight altitude.

могут задаваться с учетом возможных поправок {ΔY_n}, $$n=\overline{\mathrm{1,}N}$$

к этому значению, определяемых, например, в пределах, соответствующих возможным ошибкам бортового навигационного комплекса.If we assume that the estimate of the current flight altitude, formed (reckoned) by the aircraft onboard aircraft, is equal to Y _nk , then the values {Y _n }, $$n=\overline{\mathrm{one,}N}$$

can be specified taking into account possible amendments {ΔY _n }, $$n=\overline{\mathrm{one,}N}$$

to this value, determined, for example, within the limits corresponding to possible errors on-board navigation system.

Wherein

Where:

- оценка текущей высоты полета ЛА, сформированная (счисленная) бортовым НК ЛА; $$Y_{n\mathrm{to}}\in ({\underset{\_}{Y}}_{n\mathrm{to}},{\overline{Y}}_{n\mathrm{to}})$$

- an estimate of the aircraft’s current altitude, formed (calculated) by the aircraft’s onboard aircraft;

- нижняя граница оценки текущей высоты полета ЛА, с учетом возможных ошибок бортового НК ЛА; $${\underset{\_}{Y}}_{n\mathrm{to}}$$

- the lower boundary of the assessment of the current flight altitude of the aircraft, taking into account possible errors onboard aircraft NK;

- верхняя граница оценки текущей высоты полета ЛА, с учетом возможных ошибок бортового НК ЛА; $${\overline{Y}}_{n\mathrm{to}}$$

- the upper boundary of the assessment of the current flight altitude of the aircraft, taking into account possible errors onboard aircraft NK;

- значение поправки ΔY_n, к счисленным данным НК ЛА, при которой достигается максимум Ф(·).

- the value of the correction ΔY _n to the calculated data of the aircraft LA, at which the maximum Φ (·) is achieved.

In FIG. Figure 4 shows a graph reflecting the dependence of the functional Ф [F (J _ОP (x, z), J _P (x, z / y _la = Y _nk -ΔY _n ))] from ΔY _n considered above the test position and flight conditions of the aircraft at deviation of the aircraft flight altitude calculated by the aircraft from its actual value by 50 m. Similar graphs are also given for aircraft angles of decrease of minus 15 ° and minus 45 ° with the remaining trajectory parameters being equal.

Upon receipt of these dependencies, it was assumed that the observed elevations of the radar reflectors of the test position had a diameter (length) of 30 meters, and

where ⊗ is a symbol denoting a two-dimensional convolution of the reference and working radar images.

The dependencies shown in the figure of FIG. 4, have maxima expressed to different degrees. The asymmetry of these dependencies is explained by the nonlinearity of the change in the values of cos (ε _i ) and sin (ε _i ), with negative and positive deviations of the calculated values of the aircraft flight altitude from its real value.

It seems obvious that for a small peak acuity of the functional Ф [F (J _ОP (x, z), J _P (x, z / y _la = Y _nk -ΔY _n ))], estimates Δx _la = Δx _FR , Δz _la = Δz _OT corresponding to the maximum Ф (·), (when it is assumed that in (17) and (18) Δy _la = 0) can form with unacceptable errors.

In the case when the considered correction of the planned coordinates of the aircraft is carried out in the process of bringing it to the earth's surface, i.e. at the stage of reducing the aircraft, it seems possible to further refine the corrections to these coordinates (Δx _la , Δz _la ) with the appearance of the possibility of direct high-precision measurement of flight altitude

, $$\Delta {\stackrel{\wedge }{z}}_{ОТ}$$

соответствующие

, а также с использованием (14) и (15) рассчитываются коэффициенты чувствительности $$K{\stackrel{\wedge }{x}}_{ОТ}$$

, $$K{\stackrel{\wedge }{z}}_{ОТ}$$

.Thus the problem of determining the maximum of the functional F [F (J _{OP (x, z), J P} (x, z / y = Y _{nc la} -ΔY _n))], is considered as preliminary measuring procedure, which in the implementation of a minimum criterion discrepancies (maximum coordination) of the working and reference radar data are formed estimates $$\Delta {\stackrel{\wedge }{x}}_{\mathrm{ABOUT}T}$$

, $$\Delta {\stackrel{\wedge }{z}}_{\mathrm{ABOUT}T}$$

relevant

, as well as using sensitivity coefficients, are calculated using (14) and (15) $$K{\stackrel{\wedge }{x}}_{\mathrm{ABOUT}T}$$

, $$K{\stackrel{\wedge }{z}}_{\mathrm{ABOUT}T}$$

.

, $$\Delta {\stackrel{\wedge }{z}}_{ОТ}$$

, $$K{\stackrel{\wedge }{x}}_{ОТ}$$

, $$K{\stackrel{\wedge }{z}}_{ОТ}$$

, а также значение ошибки оценки высоты полета ЛА, определяемое в соответствии с выражениемThen, in the process of subsequent reduction of the aircraft to the earth's surface, corrections (Δx _la , Δz _la ) to the reckoned planned coordinates of the aircraft are formed by "reverse recount" using expressions (17), (18), into which the previously calculated values are substituted $$\Delta {\stackrel{\wedge }{x}}_{\mathrm{ABOUT}T}$$

, $$\Delta {\stackrel{\wedge }{z}}_{\mathrm{ABOUT}T}$$

, $$K{\stackrel{\wedge }{x}}_{\mathrm{ABOUT}T}$$

, $$K{\stackrel{\wedge }{z}}_{\mathrm{ABOUT}T}$$

, as well as the value of the error in estimating the aircraft flight altitude, determined in accordance with the expression

Where:

y _nk - the current value of the flight altitude of the descending aircraft in the NZSC OUM PK reckoned NK;

Y _P - the value of the height of the calculated point of bringing the aircraft to the earth's surface in the NSC OUM (determined simultaneously with the preparation of the reference radar);

h _T - current flight altitude directly measured by airborne means over the underlying surface.

The implementation of the “reverse translation” is possible when:

a) the change in the error in calculating the flight altitude of the navigation system for the time elapsed since the end of the correction of the coordinates of the aircraft by the OAM can be considered insignificant [7];

b) as the aircraft approaches its predetermined point of reduction, the differences in the current flight altitude of the aircraft relative to this point and the underlying surface disappear in the NSCC OUM (otherwise, the effect of the terrain becomes insignificant).

Mathematical modeling carried out for the flight conditions of the aircraft considered above confirmed the possibility of using the “reverse translation” of amendments to the planned coordinates of the aircraft.

In view of the foregoing, the proposed method for navigating an aircraft through radar images of the earth’s surface formed by radar systems using antenna aperture synthesis is implemented as follows.

1. In preparing the flight mission of the aircraft, the reference areas of the terrain to be monitored are determined from the radar images of which the planned coordinates of the aircraft should be corrected. For each OUMA, a reference point is assigned, relative to which the plan coordinates of the aircraft should be corrected, the origin of coordinates and the directions of the axes of the NSC OUMA are set based on the conditions of the navigation task. The conditions for the beginning of the formation of working radar sensors of OUM are determined, for example: achievement by the aircraft of a given range to the OT specified on the OUM.

2. For each OUM, before the flight or during the flight, support radar data are formed in the selected NSCS.

3. In flight, the formation of the frames of the primary working radar sensors of the OUMA using CAP in the coordinate system "Doppler frequency - slant range."

высот полета ЛА (например, с использованием выражения (23): Y_n=Y_нк-Y_n), для которых будет осуществляться формирование рабочих РЛИ в НЗСК ОУМ.4. The set of calculated values {Y _n }, $$n=\overline{\mathrm{one,}N}$$

aircraft flight altitudes (for example, using the expression (23): Y _n = Y _nk -Y _n ), for which the formation of working radar data will be carried out in the NZSC OUM.

5. For each value of the aircraft flight altitude from a given set of calculated altitude values, (using expressions (14), (15) or (19), (20)), the primary working radar frames are converted from the Doppler frequency - slant range coordinate system the aggregate (array) of frames of workers of radar data in the selected NZSK.

In order to eliminate the speckle effect, incoherent summation of the frames of the OUM radar sensors formed in the NSC from the frames of the primary OUM radar sensors with the same calculated values of the aircraft altitude is performed.

6. The reference OMI RMI and each OUM RRL are compared from the set of working radar images of the reference terrain formed in the NSCC with an estimate of the function maxima reflecting the mutual correlation of the indicated RRLs when the relative position of the working and reference RRLs along the X, Z coordinates changes.

Based on the results of the comparison, a set of values of the maxima of the function is formed, which reflects the cross-correlation in the NSC of the reference and working radar sensors of the OUM. Each of these maxima corresponds to a specific specified design value of the aircraft altitude.

7. Based on a comparison of the values of the maxima of the function, which reflects the mutual correlation of the reference and working radar sensors of the OUM in the NSC, those calculated values of corrections for which the maximum value is the largest are accepted as corrections to the estimates of the planned coordinates of the aircraft.

8. In the case where the sharpness of the peak of the functional F [F (J _{OP (x, z), J P} (x, z / y = Y _{nc la} -ΔY _n))], determined in accordance with some predetermined decision rule, for example, by its half level, it is insufficient and there is the possibility of subsequent more accurate determination of the values of the current flight altitude and, therefore, the values of the corresponding amendments to the values of the flight altitude formed by the aircraft, are:

, соответствующей значению ΔY_n, при которой достигается максимум функционала Ф(·);correction assessment

corresponding to the value ΔY _n , at which the maximum of the functional Ф (·) is achieved;

, $$K{\stackrel{\wedge }{z}}_{ОТ}$$

, а также значений поправок $$\Delta {\stackrel{\wedge }{x}}_{ОТ}$$

, $$\Delta {\stackrel{\wedge }{z}}_{ОТ}$$

к плановым координатам опорной точки формируемого в НЗСК рабочего РЛИ ОУМ с использованием указанной поправки

.calculation of sensitivity coefficients $$K{\stackrel{\wedge }{x}}_{\mathrm{ABOUT}T}$$

, $$K{\stackrel{\wedge }{z}}_{\mathrm{ABOUT}T}$$

as well as correction values $$\Delta {\stackrel{\wedge }{x}}_{\mathrm{ABOUT}T}$$

, $$\Delta {\stackrel{\wedge }{z}}_{\mathrm{ABOUT}T}$$

to the planned coordinates of the reference point formed in the NZSK working radar OUM using the specified correction

.

9. Measurement of the value of the current flight altitude of the aircraft and the formation of the updated current correction Y _P + h _T to its current values of y _nk coming from the aircraft of the aircraft.

10. Calculation of the adjusted values of the amendments to the current planned coordinates of the aircraft formed by the SC of the aircraft in the SC OUM

where Δy _la is determined in accordance with (25)

In FIG. 5 shows a simplified block diagram of a possible radar system that implements the proposed method for navigating an aircraft through radar images of the earth’s surface, where:

1 - radar antenna;

2 - switch reception - transmission radar;

3 - radar transmitter;

4 - radar synchronizer;

5 - digital radar control device;

6 - coherent radar receiver;

7 - analog-to-digital Converter;

8 - block primary processing and storage of the path signal;

9 - block Fourier transform;

10 - block conversion of the primary current radar from the coordinate system "Doppler frequency - slant range" in the ZSC;

11 is a unit for calculating the maxima of the VKF reference and current radar data in the KCC;

12 is a block for generating amendments to the planned navigation coordinates and aircraft altitude and the calculation of sensitivity coefficients;

13 - unit for measuring height;

14 - airborne navigation control system of the aircraft.

The presented version of the radar operates as follows.

When the aircraft reaches the portion of the flight path where correction of the aircraft’s planned coordinates by radar images of the earth’s surface should be carried out, the radar antenna 1 under control from the digital control device 5 is installed in the direction of sighting of the specified reference area. The antenna emits sounding radar signals received through the receive-transmit switch 2 from the transmitter 3, controlled by the radar synchronizer 4, and also receives reflected signals, ensuring their spatial selection. Through the receive-transmit switch 2, the received signals are received at the input of the radar receiver 6, from the outputs of which are transmitted in quadratures to the input of the multi-channel analog-to-digital converter 7. The received radar signals converted to digital form are multiplied with the reference function in the unit 8 for the initial processing and storage of the path signal . Multiplication is carried out in order to focus the synthesized radar images of the observed area of the earth's surface. At the same time, in block 8, data arrays are generated and stored that are subjected to fast Fourier transform by block 9, with the help of which primary working radar images of the observed area are formed in the Doppler frequency - slant range coordinate system. These images come in block 10 converting the primary working radar from the coordinate system "Doppler frequency - oblique range" in the working radar, presented in a normal terrestrial coordinate system OUMA.

возможных расчетных значений высоты полета ЛА, поступающих в блок 10 из цифрового устройства управления 5 БРЛС, управляющего также режимами работы синхронизатора 4 БРЛС.Block 10, the conversion of the working radar from the coordinate system "Doppler frequency - slant range" in the normal earth coordinate system is carried out for a set of {Y _n }, $$n=\overline{\mathrm{one,}N}$$

possible calculated values of the flight altitude of the aircraft entering block 10 from a digital radar control device 5, which also controls the operating modes of the radar synchronizer 4.

In order to eliminate the speckle effect, block 10 performs incoherent summation of the frames of the current OAM radar images formed in the NSC from the frames of the primary working OUM radar records with the same calculated values of the aircraft flight altitude.

A set of possible calculated values of the flight altitude of the aircraft is formed by a digital radar control device 5 based on data received from the onboard navigation system 14 of the aircraft, within the limits provided by this complex of errors in estimating the indicated altitude.

From block 10, the operational radar data presented in the OMSC OUM are sent to block 11, where each of these radar data is subjected to a type of cross-correlation with the reference radar signal received from the digital control device (block 5) of the observed reference area when the relative positions of the working and reference radar signals are mutually changed along the coordinates X and Z of the NZSC.

возможных текущих значений высоты полета ЛА сопоставляется значение $$\underset{x,z}{\max }F\left(J_{ОП}(x,z\right),J_P(x,z/y_{ла}=Y_n))=\underset{x,z}{\max }F(J_{ОП}(x,z),J_P(x,z/y_{ла}=Y_{нк}-\Delta Y_n))$$

максимума функции, отражающей взаимную корреляцию опорного и рабочих РЛИ, представленных в НЗСК ОУМ.According to the results of this processing, each value from the set {Y _n }, $$n=\overline{\mathrm{one,}N}$$

possible current flight altitude values $$\underset{x,z}{\max }F\left(J_{\mathrm{ABOUT}P}(x,z\right),J_P(x,z/y_{l\mathrm{but}}=Y_n))=\underset{x,z}{\max }F(J_{\mathrm{ABOUT}P}(x,z),J_P(x,z/y_{l\mathrm{but}}=Y_{n\mathrm{to}}-\Delta Y_n))$$

the maximum of the function, reflecting the mutual correlation of the reference and working radar, presented in the NSC OUM.

The values of the indicated maxima are transferred from block 11 to block 12, which are used for:

, $$\Delta {\stackrel{\wedge }{z}}_{ОТ}$$

,

к плановым координатам ОТ ОУМ и высоте полета ЛА на основе сопоставления значений максимумов функции F(J_ОП(x, z), J_P(x, z/y_ла=Y_нк-ΔY_n)), $$n=\overline{\mathrm{1,}N}$$

, N отражающей взаимную корреляцию опорного и рабочих РЛИ ОУМ в НЗСК, при этом в качестве поправок к оценкам плановых координат ЛА принимаются те расчетные значения поправок, для которых величина указанного максимума является наибольшей;amendment $$\Delta {\stackrel{\wedge }{x}}_{\mathrm{ABOUT}T}$$

, $$\Delta {\stackrel{\wedge }{z}}_{\mathrm{ABOUT}T}$$

,

to the planned coordinates FROM the OUMA and the flight altitude of the aircraft based on a comparison of the values of the maxima of the function F (J _OP (x, z), J _P (x, z / y _la = Y _nk -ΔY _n )), $$n=\overline{\mathrm{one,}N}$$

, N reflecting the cross-correlation of the reference and working ORL radar sensors in the NSC, while the estimated values of the corrections for which the maximum value is the largest are accepted as corrections to the estimates of the planned coordinates of the aircraft;

соответствии с заданным решающим правилом, например по его половинному уровню;assessment of the acceptability of the corrections according to the sharpness of the peak of the functional Ф [F (J _ОП (x, z), J _P (x, z / y _la = Y _nk -ΔY _n ))], $$n=\overline{\mathrm{one,}N}$$

compliance with a given decision rule, for example at its half level;

, $$K{\stackrel{\wedge }{z}}_{ОТ}$$

, соответствующих максимуму Ф(·).calculation of sensitivity coefficients $$K{\stackrel{\wedge }{x}}_{\mathrm{ABOUT}T}$$

, $$K{\stackrel{\wedge }{z}}_{\mathrm{ABOUT}T}$$

corresponding to the maximum of Φ (·).

The generated navigation corrections from block 12 go to the digital radar control device (block 5) and then to the on-board navigation complex (block 14) of the aircraft.

The altimeter (block 13), for example, which is part of the aircraft’s onboard equipment, measures the current flight altitude of the aircraft when such an opportunity arises (for example, with a subsequent decrease in aircraft). The results of these measurements come from block 13 to block 5, which, in accordance with (25) and (26), calculates and issues to the navigation system of the aircraft updated corrections to the planned coordinates of the aircraft in the NSC OUM.

The proposed method for navigating an aircraft through radar images of the earth's surface has undergone mathematical modeling and experimental testing.

The research results confirmed the efficiency of the proposed method for navigating an aircraft through radar images of the earth's surface.

The proposed method of navigating an aircraft through radar images of the earth's surface allows for high accuracy in obtaining estimates of the planned navigational coordinates of the aircraft using onboard radar.

Using the proposed method does not impose any significant restrictions on the element base and it is quite possible with the existing characteristics of radar computers with CAP in terms of speed and memory size.

Literature

1. The control system of an unmanned aerial vehicle. RF patent No. 2189625 dated 09/20/2002, IPC G05D 1/12, F41G 7/36.

2. A method of navigating an aircraft through radar images of the earth's surface using digital terrain models. RF patent No. 2364887 of September 25, 2007, IPC G01S 13/90.

3. Kozayev A.A., Koltyshev U. U., Frolov F.Yu., Yankovsky V.T. Algorithm of Doppler velocity measurement in synthetic aperture radar. // Radio engineering, 2005, No. 6, p.13.

4. A method for navigating an aircraft through radar images of the earth's surface. RF patent No. 2483324 of 11/23/2011, IPC G01S 13/90.

5. US patent US No. 5430445, 12.31.1992, G01S 13/90.

6. Merkulov V.I., Drogalin V.V., Kanaschenkov A.I. and other Aviation systems of radio control. T.2. Radio-electronic homing systems / under. ed. A.I. Kanaschenkova and V.I. Merkulova. M .: Radio engineering, 2003.

7. Babich O.A., Dobrolensky Yu.P., Kozlov M.S. et al. Aviation Instruments and Navigation Systems / Ed. O.A. Babich. - M.: VVIA named after prof. NOT. Zhukovsky, 1981.

Claims (1)

A method of navigating an aircraft through radar images of the earth's surface, which consists in determining and correcting data on the current navigation coordinates of the aircraft at each correction point, the values of the corrections to the current values of the components of the flight speed of the aircraft, measured by its onboard navigation system, taking into account certain values of the amendments to the values of the components of the speed of flight, form in the process of correction using the onboard rad of a radar station with antenna aperture synthesis frames of primary working radar images of the area of the reference terrain (according to which the coordinates are corrected) in the coordinate system "Doppler frequency - slant range", taking into account certain values of corrections to the values of the components of the flight speed of the aircraft formed by the onboard control system the aircraft, carry out the conversion of the frames of the primary working radar images of the reference portion of the the coordinates from the coordinate system "Doppler frequency - oblique range" to the normal earth coordinate system, characterized in that when converting the primary synthesized working radar images from the coordinate system ″ Doppler frequency - oblique range ″ to the normal earth system, the coordinate sets a priori a lot of corrections to the value the flight altitude of the aircraft, calculated by its navigation system, for each correction from a given set of corrections to the calculated altitude from the flight, the frames of the primary working radar images are converted from the Doppler frequency - oblique range coordinate system to the totality of the working radar image frames in the selected normal earth coordinate system, the frames of the working radar images of the reference region of the area formed in the normal earth coordinate system are incoherently summed from frames of primary radar images of the area of the reference area with According to the calculated values of the corrections to the flight altitude of the aircraft, the reference radar image of the reference terrain and each radar image of the region of the reference terrain is compared from the composition of the set of working radar images of the region of the reference terrain formed in a normal earth coordinate system with an estimate of the function maxima reflecting the cross-correlation specified radar images when changing their relative planned coordinates, according to the results of the comparison, they form a set of maximum values of the function reflecting the cross-correlation in the normal earth coordinate system of the reference and working radar images of the area of the reference terrain, based on a comparison of the maximums of the function that reflects the mutual correlation of the reference and working radar images of the region of the reference terrain in normal terrestrial coordinate system, as amendments to estimates of the planned navigational coordinates of the aircraft n they take into account those calculated values of the corrections for which the value of the indicated maximum is the largest, memorize these values, as well as the values of the corrections to the calculated flight altitude of the aircraft, to which the specified maximum corresponds, calculate and remember the corresponding values of the sensitivity coefficients of the planned coordinates of the reference point of the reference area to errors in assessing the current relative flight altitude of the aircraft, with the use of which, when When corrections are calculated to the altitude of flight of the aircraft calculated relative to the reference point of the reference area, the updated values of the current values of the corrections to its planned navigation coordinates are calculated.

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