RU2796121C1 - Method for determining range to ground source of radiation from aircraft equipped with azimuthal phase direction finder - Google Patents

Abstract

FIELD: determining the distance to a radiation source (RS).

SUBSTANCE: invention utilizes the azimuthal method using a phase direction finder placed on board an aircraft flying in the direction of the radiation source. The method for determining the distance to a ground source of radiation from an aircraft equipped with an azimuth phase direction finder consists of detecting the source of radiation, in flight towards the source of radiation, in determining the current flight altitude of the aircraft, in measuring, using the direction finder, angles to the radiation source in the absence and after roll , measuring the angle of roll and calculating, using the obtained data, the distance to the radiation source. The accuracy of determining the range to the radiation source is ensured by using a recurrent Wiener filter to evaluate the measurements of bearings to the radiation source coming from the phase direction finder and additional filtering of the calculated data on the distance to the radiation source using a recurrent low-pass filter to eliminate high-frequency noise components, as well as accounting for time needed to pitch the aircraft. In addition, the simplicity of these filters makes it possible to practically implement them in onboard equipment of an unmanned aerial vehicle with limited weight and size characteristics, that is, in small unmanned vehicles.

EFFECT: increase of the accuracy of determining the distance to the radiation source.

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Description

The present invention relates to methods for determining the distance to a radiation source (IS) by goniometric method using a phase direction finder placed on board an aircraft flying in the direction of the radiation source.

When applying the phase method of direction finding in one plane (one-dimensional direction finding), at least two weakly directional small antennas are required, separated by a distance d, called the base. In this case, the root-mean-square error of measuring the angle σ _α =λ/(2πd⋅cos(α)q ^0.5 ) is proportional to the ratio (λ/d), where α is the angle between the normal to the base and the direction of the received radiation, q is the signal-to-noise ratio [Belotserkovsky G.B. Fundamentals of radar and radar devices. M.: Sov. radio, 1975. 336 p.: ill., pp. 91-93]. The required accuracy in this case is achieved by increasing the separation of the phase direction finder antennas, that is, by increasing the base d. In the azimuth plane, this can be achieved by placing the direction finder antennas, for example, at the wingtips of the aircraft. In the elevation plane, it is almost impossible to spread the antennas.

, где Н, γ - высота полета и угол крена самолета; θ0, θ - углы с вершиной в середине антенной базы между направлениями на источник излучения и на правую антенну фазового пеленгатора при полете самолета без крена и с креном, соответственно. Недостатком способа является низкая точность определения дальности до источника излучения, что связано с малым изменением углов при выполнении крена самолета на больших дальностях до ИИ и недостаточной точностью определения пеленгатором углов на ИИ. Также в способе-прототипе было принято допущение, что время, необходимое для выполнения крена, мало и расстояние между точками местонахождения самолета до и после выполнения крена незначительно.The closest in essence and achieved effect (prototype) is a method for determining the range to a ground-based radiation source using a phase direction finder placed on board an aircraft, the antennas of which are installed on the wingtips [RF Patent for invention No. apparatus”, published on 02.12.2021, bul. 34. IPC G01S 11/02, G01S 3/46, G01S 5/04]. The method is based on the successive measurement by a direction finder from an aircraft performing a horizontal flight towards the AI, the angles on the AI in the absence of the aircraft roll and after the roll is performed, the calculation of the range to the AI, taking into account the knowledge of the flight altitude and the roll angle according to the formula

, where H, γ - flight altitude and aircraft roll angle; θ0, θ - angles with a vertex in the middle of the antenna base between the directions to the radiation source and to the right antenna of the phase direction finder when the aircraft is flying without a roll and with a roll, respectively. The disadvantage of this method is the low accuracy of determining the range to the radiation source, which is associated with a small change in angles when the aircraft rolls at long ranges to AI and insufficient accuracy in determining the direction finder angles on AI. Also in the prototype method, it was assumed that the time required to perform a roll is small and the distance between the aircraft's location points before and after the roll is insignificant.

The technical result of the invention is to increase the accuracy of determining the range to the radiation source by using a recurrent Wiener filter to evaluate the measurements of bearings to the radiation source coming from the phase direction finder and additional filtering the calculated data on the distance to the radiation source using a recurrent low-pass filter to eliminate high-frequency noise components, as well as taking into account the time required to perform the roll of the aircraft. The simplicity of these filters makes it possible to practically implement them in the onboard equipment of an unmanned aerial vehicle with limited weight and size characteristics, that is, in small unmanned vehicles.

This result is achieved by the fact that in a known method for determining the range to a ground source of radiation from an aircraft equipped with an azimuth phase direction finder, the antennas of which are located at the wingtips, based on the detection of the radiation source, flight towards the radiation source, determining the current flight altitude of the aircraft, measuring from using an angle finder to the radiation source in the absence and after the roll, measuring the roll angle and calculating using the obtained data the distance to the radiation source, according to the invention

after measuring the angle to the radiation source, the aircraft is directed towards it in such a way that during level flight the angle between the direction of the aircraft flight and the bearing to the radiation source is not less than 5 °,

continue flying in a horizontal plane with a constant heading, making successive roll maneuvers in different directions,

at the same time, discretely in time at each i-th step, the aircraft roll angle and the angle to the radiation source are simultaneously measured,

, где γ_i, θ_i - измеренные угол крена самолета и угол с вершиной в середине антенной базы между направлениями на источник излучения и на правую антенну фазового пеленгатора; Н - высота полета самолета;

- отфильтрованное на предыдущем шаге фильтром нижних частот значение дальности до источника излучения и прогнозируемое ее приращение

,recalculate the angle to the radiation source under the assumption that the aircraft roll angle is zero, according to the formula

, where γ _i , θ _i - the measured roll angle of the aircraft and the angle with the vertex in the middle of the antenna base between the directions to the radiation source and to the right antenna of the phase direction finder; H - aircraft flight altitude;

- the value of the distance to the radiation source filtered at the previous step by the low-pass filter and its predicted increment

,

, где

- оценка пересчитанного угла на предыдущем шаге и прогнозируемое ее приращение

;

- коэффициент передачи фильтра Винера, σ_α - среднеквадратическая ошибка измерения пеленга на источник излучения, σ_ξ - среднеквадратическое отклонение состояния системы,evaluate the recalculated angle using the Wiener recursive formula

, Where

- estimate of the recalculated angle at the previous step and its predicted increment

;

- transmission coefficient of the Wiener filter, σ _α - root-mean-square error of bearing measurement to the radiation source, σ _ξ - standard deviation of the system state,

и осуществляют ее фильтрацию с использованием фильтра нижних частот по формуле

, где D_i-1 - рассчитанная на предыдущем шаге дальность до источника излучения, Т - постоянная времени фильтра нижних частот, Δt - шаг дискретизации.calculate the distance to the radiation source by the formula

and filter it using a low-pass filter according to the formula

, where D _i-1 is the distance to the radiation source calculated in the previous step, T is the time constant of the low-pass filter, Δt is the sampling step.

- вектор скорости самолета; H - высота полета самолета; D_i - расстояние от самолета до ИИ; θ_i (θ0_i) - измеряемый (пересчитанный) угол на ИИ относительно правой антенны при наличии (отсутствии) крена самолета.The essence of the invention is illustrated in Fig. 1, which shows the relative position of the aircraft and the radiation source in space. In FIG. 1 are marked: 0 - the location of the aircraft at the i-th measurement step, which corresponds to the middle of the direction finder antenna base; 1* - the plane of the aircraft with a roll angle γ _i ; 1 - the plane of the aircraft at the same point, if the roll angle were equal to zero; 2*, 3* (2, 3) - position of the left and right antennas of the phase direction finder when the aircraft is rolling (at zero roll); 4 - radiation source; OXYZ - Cartesian coordinate system;

- aircraft speed vector; H - aircraft flight altitude; D _i - distance from the aircraft to AI; θ _i (θ0 _i ) - measured (recalculated) angle on the AI relative to the right antenna in the presence (absence) of the aircraft roll.

[Патент РФ на изобретение №2760975 «Способ определения местоположения источника излучения с борта летательного аппарата», опубликовано 02.12.2021, бюл. 34. МПК G01S 11/02, G01S 3/46, G01S 5/04]. При этом было принято допущение, что время, необходимое для выполнения крена самолета с положения без крена, когда угол на ИИ равен θ0_i, на угол γ_i, когда угол на ИИ равен θ_i, мало и расстояние между точками местонахождения самолета до и после выполнения крена незначительно. В предложенном авторами способе устранено данное допущение. Для этого проводится пересчет измеренного угла на источник излучения для случая, если бы угол крена самолета был равен нулю, по преобразованной из способа-прототипа формуле

с последующей его фильтрацией от шумов измерения пеленгов и шумов состояния системы (оценкой) фильтром Винера [Оценка характеристик и выбор фильтров сопровождения в реальном масштабе времени для тактических систем вооружения. Зингер Р.А., Бенке К.В. Зарубежная радиоэлектроника, 1972, №1, с. 44-60]. Этот фильтр работает как фильтр Калмана после установившегося значения коэффициента передачи. При этом применительно к фильтру для пересчета применяется формулаIn the prototype method, the distance to the radiation source is calculated by the formula

[RF patent for invention No. 2760975 "Method for determining the location of a radiation source from an aircraft", published 02.12.2021, bul. 34. IPC G01S 11/02, G01S 3/46, G01S 5/04]. At the same time, it was assumed that the time required to roll the aircraft from a position without a roll, when the angle on the AI is θ0 _i , to the angle γ _i , when the angle on the AI is equal to θ _i , is small and the distance between the aircraft location points before and after roll performance is insignificant. In the method proposed by the authors, this assumption is eliminated. To do this, the measured angle is recalculated to the radiation source for the case if the aircraft roll angle was equal to zero, according to the formula converted from the prototype method

with its subsequent filtering from bearing measurement noise and system state noise (estimation) by the Wiener filter [Evaluation of performance and selection of tracking filters in real time for tactical weapon systems. Singer R.A., Benke K.V. Foreign radio electronics, 1972, No. 1, p. 44-60]. This filter works like a Kalman filter after a steady state gain value. In this case, in relation to the filter for recalculation, the formula is applied

- сглаженное на предыдущем шаге фильтром нижних частот значение дальности и прогнозируемое ее приращение

. Рекуррентная формула фильтра Винера имеет видWhere

- the range value smoothed at the previous step by the low-pass filter and its predicted increment

. The recursive formula of the Wiener filter has the form

, в которой среднеквадратическая ошибка измерения пеленга на источник излучения σ_α известна, а среднеквадратическое отклонение состояния системы σ_ξ выбирается с учетом маневренных свойств самолета и устойчивости фильтра.The Wiener filter gain is constant and can be calculated in advance before the flight using the formula

, in which the root-mean-square error of the bearing measurement to the radiation source σ _α is known, and the root-mean-square deviation of the state of the system σ _ξ is chosen taking into account the maneuvering properties of the aircraft and the stability of the filter.

неизвестны, то им присваивается примерное значение, приращению -

, где V - скорость самолета; Δt - шаг дискретизации по времени, углу на ИИ относительно антенн пеленгатора и ее оценке -

, где α - угол между направлением полета самолета и пеленгом на ИИ (примерно равен курсу самолета относительно ИИ при отсутствии крена самолета и большом отношении H/D), ее приращению -

. То есть фильтр Винера полноценно начинает работать после 2-3 измерений и итераций.Since, during the initial direction finding, the distance to the AI D ₀ and its smoothed value

are unknown, then they are assigned an approximate value, the increment -

, where V is the speed of the aircraft; Δt - sampling step in time, angle on AI relative to direction finder antennas and its estimation -

, where α is the angle between the direction of the aircraft flight and the bearing on the AI (approximately equal to the course of the aircraft relative to the AI in the absence of the aircraft roll and a large H/D ratio), its increment is

. That is, the Wiener filter fully begins to work after 2-3 measurements and iterations.

The distance to the AI is calculated using the recurrent formula

However, the calculated ranges have high-frequency noise associated with the rapid maneuvers of the aircraft in the form of a roll in different directions and, accordingly, rapid changes in the measured angle according to the sawtooth law. To eliminate this, the calculated data are filtered (smoothed) by a low-pass filter according to the formula

where T is the time constant of the low-pass filter [Kuzovkov N.T. and others. Non-reactive and discrete control systems and identification methods / N.T. Kuzovkov, S.V. Karabanov, O.S. Salychev. M: Mashinostroenie, 1978. 22 p. S. 56-57].

Based on the foregoing, to implement the method, it is necessary to perform the following operations.

), приращение

, угол на источник излучения θ0₀, его оценку

и ее приращение

, запомнить для следующего шага данные

. Коэффициент передачи K рассчитывается заранее и хранится в памяти постоянно.Initially, for i=0 steps, after detecting the AI and determining the bearing on the AI, direct the aircraft in its direction so that the angle between the direction of flight and the bearing on the AI is at least 5 °, determine the flight speed V, set approximately the distance to the radiation source to ( D ₀ ) and after filtering (

), increment

, the angle to the radiation source θ0 ₀ , its estimate

and its increment

, remember the data for the next step

. The transmission factor K is calculated in advance and stored permanently in memory.

For the next i-th step:

1) determine the flight altitude H, perform a roll and measure the roll angle γ _i and the angle θ _i to the radiation source relative to the direction finder antennas;

по формуле фильтра Винера (2), определить приращение на следующий шаг

,2) using the stored data and current H, γ _i recalculate the angle θ _i to θ0 _i according to formula (1), evaluate it

according to the Wiener filter formula (2), determine the increment for the next step

,

по формуле (4), определить приращение

, обновить в памяти данные

;3) calculate the distance to AI D _i by formula (3) and its smoothed value after filtering

according to formula (4), determine the increment

, refresh data in memory

;

4) level the aircraft in a horizontal plane;

5) repeat operations 1)-4), taking into account the fact that the roll is alternately performed either in one direction or the other, taking the values ± γ.

The speed, altitude and roll of the aircraft can be determined using standard on-board devices [Vorobiev V.G., Glukhov V.V., Kadyshev I.K. Aviation instruments, information-measuring systems and complexes. M.: Transport, 1992. 399 p.: ill., pp. 239-260]. For example, a vertical gyro can be used as a roll sensor, a barometric altimeter can be used as an altimeter, and indicators of true airspeed and M numbers can be used as speed sensors.

Recalculation of angles to the radiation source, calculation of the distance to it with the implementation of Wiener and low-pass filters can be performed on microcontrollers (for example, on a single-chip eight-bit microcontroller of the PIC16F62X type) with software according to the presented formulas (1) - (4).

To compare the prototype method and the proposed method, an estimate of the relative error in determining the range (σ _d /D) from the aircraft to the AI was made, for which a simulation of the flight of the aircraft to the radiation source was carried out. In this case, the following initial data and assumptions were accepted:

- the aircraft performs a horizontal flight with a constant heading at an altitude of 3 km at a speed of 100 m/s towards AI from a distance of 100 km;

- when performing a flight with a step Δt=1c, the aircraft roll angle is successively changed by 45° and the angle on the AI θ _{i is measured;} . In this case, the roll angle, depending on the i-th step, takes sequentially the values {-45°, 0, 45°};

- the error in determining the bearing on the AI by the phase direction finder is σ _α =0.5°;

- dispersion of deviation of the state of the system is given by σ _ξ =2°;

- transmission coefficient of the Wiener filter K=0.941;

- time constant of the low-pass filter T=5 s.

практически не меняется, а достаточно большие ошибки определения пеленга «раскачивают» фильтр Винера. Оценки относительной погрешности определения дальности до ИИ при первоначальном угле между направлением полета самолета и направлением на источник излучения 5°, приведенные на фиг. 2б, показали лучшие по сравнению со способом-прототипом показатели. Так относительная погрешность определения дальности до ИИ (σ_D/D) в предложенном способе составляет 11-12%, а в способе-прототипе - 17%, где σ_D - среднеквадратическая ошибки определения дальности. При этом ошибка измерения угла крена σ_γ может достигать 1°, а относительная ошибка измерения высоты полета самолета (σ_H/H) - 1%.The simulation results shown in FIG. 2a showed that the flight of an aircraft at an initial angle of less than 4–5° on the IS leads to a significant increase in errors in determining the range to the IS. This is because the angle

practically does not change, and sufficiently large errors in determining the bearing "swing" the Wiener filter. Estimates of the relative error in determining the range to the IR at an initial angle between the aircraft flight direction and the direction to the radiation source of 5°, shown in Fig. 2b showed better performance compared to the prototype method. So the relative error in determining the range to AI (σ _D /D) in the proposed method is 11-12%, and in the prototype method - 17%, where σ _D is the root-mean-square error in determining the range. In this case, the error in measuring the roll angle σ _γ can reach 1°, and the relative error in measuring the aircraft flight altitude (σ _H /H) - 1%.

Thus, the claimed method for determining the range to a ground source of radiation from an aircraft equipped with an azimuth phase direction finder provides an increase in the accuracy of determining the range to the radiation source by using a recurrent Wiener filter to evaluate the measurements of bearings coming from the phase direction finder to the radiation source and additional filtering using recurrent low-pass filter of the calculated range data to the source of radiation to eliminate high-frequency noise components, as well as taking into account the time required to perform the roll of the aircraft. In addition, the simplicity of these filters makes it possible to practically implement them in the onboard equipment of an unmanned aerial vehicle with limited weight and size characteristics, that is, in small unmanned vehicles.

to the emitter by using a recurrent Wiener filter to evaluate the measurements of bearings to the emitter coming from the phase direction finder and additional filtering, using a recurrent low-pass filter, of the calculated range data to the emitter to eliminate high-frequency noise components, as well as taking into account the time required to perform aircraft roll. An additional technical result is that the simplicity of these filters makes it possible to practically implement them in the on-board equipment of an unmanned aerial vehicle with limited weight and size characteristics.

Claims (7)

A method for determining the range to a ground source of radiation from an aircraft equipped with an azimuth phase direction finder, the antennas of which are located at the wingtips, which consists in detecting a radiation source in flight towards the radiation source, in determining the current flight altitude of the aircraft, in measuring angles to the source using the direction finder radiation in the absence and after performing the roll, measuring the angle of roll and in the calculation using the obtained data of the range to the radiation source, characterized in that after measuring the angle to the radiation source, the aircraft is directed towards it in such a way that during horizontal flight the angle between the direction of the aircraft flight and the bearing to the radiation source is not less than 5 °, continue flying in a horizontal plane with a constant heading, making successive roll maneuvers in different directions, at the same time, discretely in time at each i-th step, the aircraft roll angle and the angle to the radiation source are simultaneously measured, recalculate the angle to the radiation source under the assumption that the aircraft roll angle is zero, according to the formula

, where γ _i , θ _i - the measured roll angle of the aircraft and the angle with the vertex in the middle of the antenna base between the directions to the radiation source and to the right antenna of the phase direction finder; H - aircraft flight altitude;

- the value of the distance to the radiation source filtered at the previous step by the low-pass filter and its predicted increment

, evaluate the recalculated angle using the Wiener recursive formula

, Where

- estimate of the recalculated angle at the previous step and its predicted increment

;

- transmission coefficient of the Wiener filter, σ _α - root-mean-square error of bearing measurement to the radiation source, σ _ξ - standard deviation of the system state, calculate the distance to the radiation source by the formula

and filter it using a low-pass filter according to the formula

, where D _i-1 is the distance to the radiation source calculated in the previous step, T is the time constant of the low-pass filter, Δt is the sampling step.

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