RU2548366C1 - Method of identification of location and angles of orientation of aircraft with respect to runway - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: method consists in estimate of coordinates of aircraft location and angles of swing, head and pitch according to information read-out from three spaced photosensitive receivers installed on an aircraft, radiation of a laser beacon scanning a vicnity with the narrow beam modulated by the size of its bearing angle and angle of altitude.

EFFECT: improvement of accuracy and reliability of identification of location of the aircraft with respect to a runway.

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Description

The invention relates to optical navigation systems, in particular, using laser and optical sources, and can be used to ensure the landing of aircraft, ship traffic, road construction, agricultural machinery and road transport.

Known optical beacon visual landing along the glide path [1], which implements a method of forming using lamp sources of light in a vertical plane adjacent to each other light zones of different colors, while the correct flight along the glide path corresponds to the location of the aircraft in the central corner zone green color. The disadvantages of this method is the low information content due to the lack of horizontal lights and information about the relative position in the color zone (edge or middle). In addition, the head of the visual landing does not have reliable information about the position of the aircraft relative to the glide path, which reduces the likelihood of a safe landing, because the possibility of objective correction of the aircraft trajectory from the ground or ship is not provided in case of inadequate pilot actions.

A device for determining the position of an aircraft in space using a mobile laser three-color navigation system [2], which uses a method based on the formation of color zones in the vicinity of the landing trajectory and visual perception by the pilot of radiation at a given wavelength. The method is implemented by two sources of optical radiation spaced in space, thus forming three zones covered by optical radiation of different wavelengths. Each source allows you to get at least two non-overlapping beams of optical radiation with different wavelengths. Optical beams with matching wavelength ranges overlap in the alignment zone. Outside the alignment zone, these beams overlap with optical radiation beams of other wavelength ranges.

The disadvantages of this method are the low accuracy, since the position of the aircraft relative to the axis of the runway (runway) within the same color zone is uncertain. In addition, the position of the aircraft is evaluated visually by the pilot, which leads to the need for human participation in the aircraft control loop, while automatic landing is not possible.

An object of the invention is to increase the accuracy and reliability of measuring the location of the aircraft relative to the runway, providing additional measurement of yaw, roll, pitch, and automation of the process of measuring these parameters.

The technical result when using the proposed method is to increase the accuracy of determining the location relative to the runway and the orientation angles of the aircraft, achieved through the use of a laser IR beacon, three laser radiation receivers, an aircraft coordinate calculator, where a system of nonlinear algebraic equations is solved with respect to the desired coordinates of the aircraft - X, Y, Z, γ, ψ, υ.

A single technical result of the invention is achieved by the fact that in a method for determining the location and orientation angles of an aircraft relative to the axis of the runway, based on the formation of light zones in the vicinity of the landing path and the pilot's visual perception of radiation of a given wavelength, the radiation of a runway installed in the vicinity is recorded laser beacon strips by means of three spaced radiation detectors made in the form of photosensitive sensors installed on an aircraft, a laser beacon that provides scanning of the near-Earth space with a narrow beam of a semiconductor laser, modulated depending on the angle of rotation α from the OX axis in azimuth and height — β, the laser beam can be scanned line by line, and the coordinates of the aircraft are determined in a horizontal coordinate system OXYZ, the OX axis of which is parallel to the axis of the runway, as well as the orientation angles of the aircraft: yaw, roll and pitch angles, by numerically solving a system of nonlinear algebraic equations:

where α ₁ , β ₁ , α ₂ , β ₂ , α ₃ , β ₃ are the location angles of the first, second, and third photosensitive sensors, taken as a digital code from these sensors;

B _x , B _y , B _z - location coordinates of photosensitive sensors in the coordinate system O ⁽¹⁾ X ⁽¹⁾ Y ⁽¹⁾ Z ⁽¹⁾ ;

ψ, γ, υ - angles of yaw, roll and pitch of the aircraft, respectively;

X, Y, Z - the coordinates of the aircraft in the coordinate system OXYZ.

Salient features from the prototype of the method is the following set of actions:

the formation of a discrete electromagnetic field in the infrared range (for example, 1.55 microns.);

laser beam modulation in terms of azimuth angle and height;

calculation of the coordinates of the location of the aircraft, yaw angles, roll, pitch, according to information received from the radiation receivers of the laser beacon.

Figure 1 shows the arrangement of the laser beacon and the aircraft, with photosensitive receivers installed on it, in the process of determining the location and orientation angles of the aircraft; figure 2 is a scanning device of a lighthouse that implements the proposed method; figure 3 - the probability of failure of the optical communication channel for various geographical regions.

The method is implemented as follows. At the beginning of the OXYZ horizontal coordinate system, a laser beacon is located, providing scanning of the near-Earth space with a narrow beam of a semiconductor laser. The laser beam is modulated (for example, by pulse-code modulation) depending on the angle of rotation α from the axis OX in azimuth and in height - β (Fig. 1).

The laser beam scan can be performed in a line-by-line manner, which has been successfully used in television for decades, for example, by means of the device shown in FIG. 2, where the following elements are indicated by positions:

1 - laser emitter;

2 - a mirror for vertical scanning (the axis of rotation is horizontal);

3 - a rotating mirror for horizontal scanning (the axis of rotation is vertical);

4 - electric motor;

5 - laser beam.

The laser beam scanner provides a horizontal scan at an angle of 0 ° ≤α≤360 °, and also vertically at an angle β (Fig. 1), if necessary, to narrow the horizontal scan, mirror 3 must be made in the form of an equilateral pyramid with reflecting side faces ( figure 2).

A set of spaced photosensitive receivers Р ₁ , Р ₂ , Р ₃ , which receive laser radiation, is installed on the aircraft, and after demodulation of the received signals, three signals α ₁ , α ₂ , α ₃ are generated, about the angular position of the photodetectors in azimuth and in height β ₁ , β ₂ , β ₃ in the coordinate system OXYZ. We assume that the coordinates of the photodetectors P ₁ (B _x , 0,0), P ₂ (0, B _y , 0), P ₃ (0,0, B _z ) in the coordinate system O ⁽¹⁾ X ⁽¹⁾ Y ^{( 1)} Z ^{(1) are} known. The task is to determine the linear and angular position of the aircraft in the OXYZ system, given by the x, y, z coordinates of the position of the origin O ⁽¹⁾ and the angles ψ, γ, υ that determine the angular position of the system in the OXYZ system (Fig. 1).

и соотношения, связывающие эти векторыWrite vectors $$\overline{O{P}_i}(i=\mathrm{one}...3)$$

and relations connecting these vectors

$$\overline{O{P}_{\mathrm{one}}}=\overline{O{O}^{(\mathrm{one})}}+i^{(\mathrm{one})}{B}_x$$

$$\overline{\mathrm{<figure-callout\; id="2"\; label="O\; P"\; filenames="00000019.png"\; state="\{\{state\}\}">O\; </figure-callout>}{P}_{}{}_2}=\overline{O{O}^{(\mathrm{one})}}+j^{(\mathrm{one})}{B}_y$$

$$\overline{O{P}_3}=\overline{O{O}^{(\mathrm{one})}}+k^{(\mathrm{one})}{B}_z$$

- вектор положения начала системы координат O⁽¹⁾X⁽¹⁾Y⁽¹⁾Z⁽¹⁾.where i ⁽¹⁾ , j ⁽¹⁾ , k ⁽¹⁾ are the unit vectors of the coordinate system O ⁽¹⁾ X ⁽¹⁾ Y ⁽¹⁾ Z ⁽¹⁾ , $$\overline{O{O}^{(\mathrm{one})}}$$

is the position vector of the origin of the coordinate system O ⁽¹⁾ X ⁽¹⁾ Y ⁽¹⁾ Z ⁽¹⁾ .

We project these equations on the axis of the OXYZ coordinate system, for this we multiply them alternately by the unit vectors i, j, k.

We express the coordinates of the photodetectors through the angles measured by them

X _i = OP _i cosα ₁ cosβ ₁ ,

Y _i = OP _i sinα ₁ cosβ ₁ ,

Z _i = OP _i sinβ ₁ ,

- модуль вектора OP_i.Where

- the module of the vector OP _i .

Using the last relations, we transform expressions (2)

OP ₁ cosα ₁ cosβ ₁ = ii ⁽¹⁾ B _x + X

OP ₁ sinα ₁ cosβ ₁ = ji ⁽¹⁾ B _x + Y

OP ₁ sinβ ₁ = ki ⁽¹⁾ B _x + Z

OP ₂ cosα ₂ cosβ ₂ = ij ⁽¹⁾ B _y + X

OP ₂ sinα ₂ cosβ ₂ = jj ⁽¹⁾ B _y + Y

OP ₂ sinβ ₂ = kj ⁽¹⁾ B _y + Z

OP ₃ cosαcosβ ₃ = ik ⁽¹⁾ B _z + X

OP ₃ sinα ₃ cosβ ₃ = jk ⁽¹⁾ B _z + Y

OP ₃ sinβ ₃ = kk ⁽¹⁾ B _z + Z

We exclude from these relations the parameters OP ₁ , OP ₂ , and OP ₃

The mutual angular position of the coordinate systems OXYZ and O ⁽¹⁾ X ⁽¹⁾ Y ⁽¹⁾ Z ^{(1) is} described by the matrix of guiding cosines of the following form

We substitute the expressions of the coefficients of the matrix of guide cosines into relations (3)

The resulting nonlinear system of equations for the unknown X, Y, Z, γ, ψ, υ can be solved by one of the numerical methods, for example, Newton, Adams, successive approximations.

Thus, the proposed measuring system provides a complete solution to the navigation problem in the vicinity of the lighthouse, since it is determined not only the location of the aircraft (coordinates X, Y, Z), but also its angular position (angles γ, ψ, υ). Real-time calculation of unknown X, Y, Z, γ, ψ, υ provides knowledge of the current coordinates of the aircraft position and opens the possibility of automation of motion control in accordance with the task at hand.

Since the measurement method under consideration relates to navigation, the question of the potential reliability and accuracy of the system if implemented is extremely important.

The reliability of such a position measurement system may not be sufficient due to the influence of atmospheric conditions on the communication channel that occurs between the beacon during the transmission of signals α ₁ , α ₂ , α ₃ , β ₁ , β ₂ , β ₃ and photosensitive receivers. Therefore, without assessing the reliability of such an information channel, consideration of the proposed method for measuring position is incorrect.

With proper installation and configuration of the atmospheric optical communication channel, the determining factor in the reliability of this channel is the weather conditions at its location [3]. The influence of the atmosphere is manifested in the attenuation of the beam by meteorological factors: rain, snow, fog, sandstorm, as well as man-made aerosols. Also, additional factors for reducing the radiation power in the receiving plane are turbulent formations in the atmosphere and their interaction with the laser radiation, which leads to the so-called “trembling” of the beam and its “spotting” in the receiving plane.

We estimate the probability of failure of the optical communication channel according to the technique presented in [3]. The terminology used in this paragraph corresponds to that used in the article.

The main parameter describing the process of interaction of optical radiation with the atmosphere is the meteorological range of visibility (MDV). Weather conditions vary not only for different geographical areas, but also from year to year. The statistical weather parameter for a specific geographical location, which determines the reliability of the communication channel, is the fraction of the time for the year during which the MDV is less than the specified value. Processing the statistical data of meteorological observations made it possible to determine the empirical dependence of this parameter on distance, of the following form [3]:

where W (L) is the probability of the occurrence of weather conditions under which the MDV is less than the distance L,

L is the distance of the optical communication channel, m,

a _i , b _i - constants for a specific geographical point.

Relation (4) is valid for MDVs of less than 17 km [3].

The constants for a specific geographical point (for various cities of Russia) are given in table 1, they are calculated for the observation period of several years for some cities located in different geographical regions of Russia.

In clear weather, atmospheric turbulence determines the ultimate communication range. The effect of atmospheric turbulence and scintillation in a laser beam is significantly attenuated by the introduction of several laser transmitters, since their radiation is substantially incoherent.

At present, the theory of turbulent processes in the atmosphere, relating to the inertial interval of turbulence development, allows one to describe many fluctuation effects in laser beams on atmospheric paths. This theory, based on Kolmogorov’s “two-thirds law,” suggests a cascade process of vortex fragmentation with a stable size distribution spectrum of inhomogeneities. Such an approach has long served as almost the only basis for interpreting experimental data on fluctuations of laser radiation in the atmosphere, including on surface paths. And in the case of the propagation of laser radiation in the surface layer of air, this theory turns out to be too rough an approximation. An analysis of the results of studies described in various publications shows that turbulence in the surface air layer is more complex, due to the development of various kinds of instabilities. Since there are currently no complete theoretical studies that allow us to estimate the reliability parameters of the communication channel, as well as to average the influence of the aperture of the receiver and take into account the destruction of coherence on aerosols of the atmosphere, an empirical dependence is estimated that estimates these factors [3]

where I is the factor of possible signal attenuation at a distance L, dB,

L is the distance from the transmitter to the receiver, m,

Θ is the full angle of divergence of the radiation from the transmitter, glad

D _r - the diameter of the aperture of the optical system of the receiver, m

Expression (5) was obtained on the basis of direct measurements, as well as data from other manufacturers of atmospheric optical communication lines, in particular Optical Access [3].

Using Booger's law, as well as the geometric attenuation factor of the signal, from expression (5) we obtain the equation for determining the maximum path length for a given MDV

where P _t is the pulse power of the transmitters, W,

P _r is the sensitivity of the receiver with a signal to noise ratio of 10/1, W,

V - meteorological visibility range, m,

N is the number of transmitting lasers.

A coefficient of 1.2 at V was introduced to take into account the wavelength of infrared laser radiation (0.8-1.6 μm) [3].

Using expressions (4) and (6), we obtain the ratio for determining the reliability of the communication channel depending on the range and weather conditions for a particular area.

The obtained expression (7) is used in calculating the probability of failure of the optical communication channel for various geographical regions, such as Izhevsk, Yaroslavl, Kirov. In this case, the following values of the constant a _i , b _i for a specific geographical point were used as initial data for the calculation (table 1):

distance from laser beacons to the radiation receiver up to 2500 m; radiation divergence angle of 10 ^-5 rad; the diameter of the aperture of the optical system of the receiver is 0.01 m; MDV - 30 m.; N = 1.

The calculation result is shown in figure 3. It illustrates the likelihood of a failure in the optical communication channel depending on the distance selected at different geographical locations.

The use of such estimates makes it possible to determine with high reliability the reliability of the communication channel for a given distance or the allowable distance for a given reliability of the communication channel.

It should be noted that in world practice it is customary to evaluate the recommended communication range of optical systems for the weather conditions of the main cities of the leading countries of the world [3]. In any case, to decide on the use of an atmospheric laser communication channel, it is recommended to use the above estimates, taking into account specific weather conditions and system parameters.

The maximum probability of failure at a distance of 2 km for Izhevsk (the worst area for the functioning of the system) is 1.4 × 10 ^-3 , and the probability of failure-free operation is 99.86%. It is easy to calculate that the communication channel will not be available within one year for just over 12 hours.

Consider the potential accuracy of the proposed system, for this we evaluate the cross section of the laser beam at a working distance of 1-2 km. With the divergence of the beam Θ and the range L, the beam cross section is determined by

Δ = Θ · L = 10- ⁵ · ³ = 10 10 m ^-2.

Thus, at a distance of 1 km, the cross section of the laser beam will have a value of 1 cm, which determines the order of measurement errors of the system. For comparison, microwave landing systems (MLS), GPS positioning systems (GLONASS) in differential mode have errors of tens of centimeters. This allows us to conclude that the proposed system can be quite competitive in solving problems of local navigation.

Information sources

1. US patent for the invention N 4064424, CL. B64E 1/20, 1982 (analog).

2. RF patent for the invention No. 2083444, class. G01S 5/08, 03/22/1994 (prototype).

3. Zelenyuk, Yu.I. The influence of weather conditions on the reliability of atmospheric optical communications [Text] / Yu.I. Zelenyuk, I.V. Ognev, S.Yu. Polyakov, S.E. Shirobakin - Communication Bulletin, No. 4, 2002.

Claims (1)

A method for determining the location and orientation angles of an aircraft relative to the runway, based on the formation of light zones in the vicinity of the landing path and the pilot's visual perception of radiation of a given wavelength, characterized in that the radiation detected in the vicinity of the runway, a laser beacon by three spaced radiation receivers, made in the form of photosensitive sensors mounted on an aircraft, a laser beacon providing scanning near-Earth space with a narrow beam of a semiconductor laser, modulated depending on the rotation angle α in azimuth and height - β, the laser beam can be scanned in a line-by-line manner, and the coordinates of the location of the aircraft in the horizontal coordinate system OXYZ, the axis OX of which is parallel to the take-off axis, are determined landing strip, as well as aircraft orientation angles: yaw, roll and pitch angles, by numerically solving a system of nonlinear algebraic equations:

where α ₁ , β ₁ ,, α ₂ , β ₂ ,, α ₃ , β ₃ are the location angles of the first, second, and third photosensitive sensors, taken as a digital code from these sensors;
B _x , B _y , B _z - location coordinates of photosensitive sensors in the coordinate system O ⁽¹⁾ X ⁽¹⁾ Y ⁽¹⁾ Z ⁽¹⁾
γ, ψ, υ - roll angles, yaw and pitch, respectively;
X, Y, Z - the coordinates of the aircraft in the coordinate system OXYZ.

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