RU2562148C1 - Remote object distance and speed determination method - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: method includes multiple sounding of an object by laser radiation impulses, reception and registration of the signal reflected by an object with its binding to the impulses of stable clock frequency forming range cells, and statistical processing of the registered data. The sounding series is performed using the incoherent accumulation method if the accepted signal is less than the threshold value which is defined by the pre-set probability F of false response. And if the accepted signal exceeds the threshold value, the sounding is performed in monopulse mode of range and speed measurement.

EFFECT: providing of the aircraft onboard measurements of its altitude and vertical component of speed both during stationary flight, and during take off and landing in a wide range of altitudes and the modes of ascent and descent.

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Description

The present invention relates to measuring technique and can be used in any field where it is necessary to determine the speed of a moving object and the distance to it, in particular, to control the relief of the underlying surface and control the landing mode of the aircraft.

There is a method of determining the distance to a distant object by sensing it with a laser pulse, receiving the reflected radiation pulse from the object and determining the time interval between the moments of radiation of the probe pulse and receiving the reflected pulse by the object, which is used to judge the distance to the object [1].

The disadvantage of this method is the inability to measure the speed of the target.

The closest in technical essence to the proposed method is a method for determining the range and / or speed of a distant object [2], which consists in repeatedly probing the object with laser pulses, receiving and recording the signal reflected by the object with its reference to pulses of a stable clock frequency, dividing the time into numbered clock intervals counted from the moment of radiation of the probe pulse and thereby forming a range cell, and statistical processing of recorded data . According to the indicated method, a multiple monopulse sounding of an object is performed by sending a series of n laser pulses to it and determining in each i-th sounding the time interval t _i between the moments of radiation of the laser pulse and receiving the radiation reflected by the object, with each sounding, the values of the current time moments T are determined and recorded _i , in which they send laser pulses, and the measured intervals t _i in a series of n soundings, and determine the speed of the object by the formula:

Where

V is the speed of the object;

R _i = c · t _i / 2 - the result of measuring the distance to the object in the i-th sounding;

c is the speed of light,

set the time moment T ∗ to which the range reference should be attached, and determine the distance to the object at this moment by the formula:

R ∗ = R ₀ + V (T ∗ -T ₁ ),

Where

R ∗ is the result of determining the distance to the object at time moment T ∗;

The indicated procedure is feasible only at small and medium altitudes of the aircraft, since it requires the reliability of measurements for each sounding of the object. Portable range and speed meters do not have sufficient energy potential for such measurements at high altitudes. With a long range to the object, the magnitude of the received signal becomes comparable with the amplitude of the noise, and the reception of each reflected pulse with a given probability becomes impossible. In this case, the speed measurement according to the specified algorithm leads to unreliable results.

The objective of the invention is the provision of measurements from the aircraft of its height and vertical component of speed in a stationary flight, and during take-off and landing in a wide range of heights and modes of rise and fall.

This problem is solved due to the fact that in the known method for determining the range and / or speed, which consists in repeatedly probing a remote object with laser pulses, receiving and recording the signal reflected by the object with its reference to pulses of a stable clock frequency, dividing the time into numbered clock intervals, counted from the moment of radiation of the probe pulse and thereby forming the range cells, and statistical processing of the recorded data, test probes are performed measurement, the level of the received signal S is determined, it is compared with the threshold value S ₀ determined by the given probability F of false positives, and if S <S ₀ , then a series of soundings is performed by the method of incoherent accumulation, namely, an array of received realizations of the reflected signal is accumulated in each range cell until the value of the accumulated array does not exceed the threshold value, then according to a predetermined criterion, for example, according to the maximum correlation coefficient of the accumulated array of accepted implementations with the array n of a previously digitized probe pulse, the serial number P of the range cell to which the reflected signal belongs is determined and the range R to the object is determined by the formula R = cPΔt / 2, where c is the speed of light; Δt is the duration of the clock interval, and if S> S ₀ , then turn off the incoherent accumulation mode and turn on the single-pulse mode for measuring range and speed, during which a series of soundings of the object is performed at least two times, at each ith sounding, the delay of its reception t _i relative to the moment of sounding, calculate the distance to the object R _i = ct _i / 2, where c is the speed of light, and determine the distance to the object and its relative speed by linear interpolation of the measurement results in the form R (t) = Vt + R ₀ , where R (t) - current yielded distance to the object; t is the current time; V is the speed estimate; R ₀ is an estimate of the distance to the object at t = 0.

, где j - порядковый номер ячейки дальности; P_max - максимальное число ячеек дальности, соответствующее диапазону измерения дальности; {S_0j} - массив выборочных значений зондирующего импульса; {S_j} - массив накопленных значений принятых реализаций; p - текущее количество шагов при пошаговом сдвиге {S_j}.The correlation coefficient can be determined by the formula

where j is the ordinal number of the range cell; P _max - the maximum number of range cells corresponding to the range of range measurement; {S _0j } - an array of sample values of the probe pulse; {S _j } - an array of accumulated values of the adopted implementations; p is the current number of steps in a stepwise shift {S _j }.

Estimates of the distance to the object R ₀ at the initial time t = 0 and the speed of the object V can be formed by the formulas:

Where

R ₀ - estimate of the distance to the object at time t = 0; V is an estimate of the speed of the object; R _i = c · t _i / 2 - the result of measuring the distance to the object in the i-th sounding; T _i - time points at which the measured range R _i ; c is the speed of light; m is the number of range measurements in the series; t _i is the delay between the moments of radiation of the laser pulse and the reception of the radiation reflected by the object in the i-th sounding.

In FIG. 1 shows implementations of a signal, noise, and mixtures thereof at a signal amplitude and a rms noise value of 1. FIG. 2 shows an array of accumulated data at N = 200. In FIG. 3 shows a graph of R = Vt + R ₀ interpolation of the results of range measurements in single-pulse mode.

, где j - порядковый номер ячейки дальности; P_max - максимальное число ячеек дальности, соответствующее диапазону измерения дальности; {S_0j} - массив выборочных значений зондирующего импульса; {S_j} - массив накопленных значений принятых реализаций; p - текущее количество шагов при пошаговом сдвиге {S_j}. Далее определяют дальность R до объекта по формуле R=cPΔt/2, где с - скорость света; Р - номер ячейки дальности, соответствующий положению накопленного массива; Δt - длительность тактового интервала. Вертикальная составляющая скорости V в этом случае может быть определена как относительное приращение высоты R за период Т между j-м и (j-1) измерениями: V=(R_j-R_j-i)/T. На фиг. 2 представлен результат накопления в содержащих сигнал десяти ячейках дальности при объеме накопления N=200. Индексом показано положение центра тяжести массива.The signal reflected from the target is mixed with the noise of the photodetector path having a standard deviation σ. The signal-to-noise mixture is compared with a threshold value S ₀ (FIG. 1). The figure conditionally shows the level S ₀ -1.8σ, at which the probability of its excess by noise is F ~ 0.04. In practice, it is set higher - at the level of 5-7σ and more, depending on the problem being solved, the dynamic range of the receiving path and the characteristics of the analog-digital analyzer. If, as shown in FIG. 1, the signal + noise mixture does not exceed the level S ₀ , then a range is measured using the method of incoherent accumulation [3]. At the end of the accumulation process, that is, upon reaching the accumulated sum of the required value in at least one range cell, the array of accumulated data is analyzed, determining the position of the accumulated array relative to the time scale by the established criterion, for example, by the center of gravity of the array [4] or by the maximum of the correlation function

where j is the ordinal number of the range cell; P _max - the maximum number of range cells corresponding to the range of range measurement; {S _0j } - an array of sample values of the probe pulse; {S _j } - an array of accumulated values of the adopted implementations; p is the current number of steps in a stepwise shift {S _j }. Next, determine the distance R to the object by the formula R = cPΔt / 2, where c is the speed of light; P is the number of the range cell corresponding to the position of the accumulated array; Δt is the duration of the clock interval. The vertical component of the velocity V in this case can be defined as the relative increment of the height R for the period T between the jth and (j-1) measurements: V = (R _j -R _ji ) / T. In FIG. Figure 2 shows the result of accumulation in ten range cells containing a signal with an accumulation volume of N = 200. The index shows the position of the center of gravity of the array.

If during the probe sounding the signal + noise mixture exceeds the level S ₀ , then the measurements are carried out in a single-pulse mode with interpolation of the measurement results [2]. At times T _i , a range is measured. The number m> 2 soundings is determined by the specified period of updating information and accuracy requirements. Estimates of the distance to the object R ₀ at the initial moment of measurement and the speed of the object V are formed by the formulas:

Where

R ₀ - estimate of the distance to the object at the initial moment t = 0; V is an estimate of the speed of the object; R _i = c · t _i / 2 - the result of measuring the distance to the object in the i-th sounding; T _i - time points at which the measured range R _i ; c is the speed of light; m is the number of range measurements in the series; t _i is the delay between the moments of radiation of the laser pulse and the reception of the radiation reflected by the object in the i-th sounding.

The distance to the object R and its relative speed V is determined by linear interpolation of the measurement results in the form of regression R (t) = Vt + R ₀ , where R (t) is the current distance to the object; t is the current time counted from the initial moment. An estimate of the flight altitude of an aircraft can be issued for any moment in time t, including for the moment of the end of a series of soundings T _m . The principle of constructing a regression is illustrated by the graph of FIG. 3. Dots show the results of individual measurements in a series of soundings.

This method allows you to:

- increase the measured height of the aircraft to 1000-2000 m;

- reduce the minimum measured height to 2 m;

- provide a minimum information update period of the order of 1 s at high altitudes and up to 0.1 s at low altitudes;

- to provide a minimum velocity measurement error of 0.01-0.1 m / s depending on the duration of the series of soundings and the number of measurements in the series;

- interpolate the results at any point in the measurement period or extrapolate them for a specified time in advance.

These conclusions are confirmed by testing prototype altimeter-speed meter [5, 6]. This confirms the fulfillment of the task - providing measurements from the aircraft of its height and vertical component of speed both in stationary flight and during take-off and landing in a wide range of heights and modes of rise and fall.

Information sources

1. V.A. Smirnov "Introduction to Optical Electronics". Ed. Soviet Radio, Moscow, 1973, p. 189.

2. A method for determining the range and / or speed of a remote object.

RF patent No. 2378705 - prototype.

3. The method of incoherent accumulation of radar signals.

RF patent No. 2455615.

4. The method of radar range determination. RF patent No. 2390724.

5. Small-sized laser altimeter DL-5M. Photonics No. 3, 2013, p. 55.

6. V.G. Vilner, V.G. Volobuev, A.A. Kazakov, B.K. Ryabokul. Ways to achieve extreme accuracy of a laser speed meter. "World of measurements" No. 7, 2010

Claims (3)

1. A method for determining the range and speed, which consists in repeatedly probing a distant object with laser pulses, receiving and recording the signal reflected by the object with its binding to stable clock pulses, dividing the time into numbered clock intervals, counted from the moment of radiation of the probe pulse and thereby forming cell range, and statistical processing of recorded data, characterized in that they produce test sounding, determine the level of received drove S, compare it with a threshold value S ₀ defined by a predetermined probability F of false alarm, and if S <S _0, then conduct a series of sounding method incoherent accumulation, namely, accumulate array received reflected signal realizations in each range cell as long as the value of the accumulated array does not exceed the threshold value, then the sequence number P is determined from the maximum correlation coefficient of the accumulated array of received realizations with the array of the pre-digitized probe pulse cell range to which the reflected signal and determine the distance R to the object by the formula R = cPΔt / 2, where c - velocity of light; Δt is the duration of the clock interval, and if S> S ₀ , then turn off the incoherent accumulation mode and turn on the single-pulse mode for measuring range and speed, during which a series of soundings of the object is performed at least two times, at each ith sounding, the delay of its reception t _i relative to the moment of sounding, calculate the distance to the object R _i = ct _i / 2, where c is the speed of light, and determine the distance to the object and its relative speed by linear interpolation of the measurement results in the form R (t) = Vt + R ₀ , where R (t) - current yielded distance to the object; t is the current time; V is the speed estimate; R ₀ is an estimate of the distance to the object at t = 0. 2. The method according to claim 1, characterized in that the correlation coefficient is determined by the formula

where j is the ordinal number of the range cell; P _max - the maximum number of range cells corresponding to the range of range measurement; {S _0j } - an array of sample values of the probe pulse; {S _j } - an array of accumulated values of the adopted implementations; p is the current number of steps in a stepwise shift {S _j }. 3. The method according to claim 1, characterized in that the estimates of the distance to the object R ₀ at the initial time t = 0 and the speed of the object V are formed by the formulas:

Where
R ₀ - estimate of the distance to the object at time t = 0;
V is an estimate of the speed of the object;
R _i = c · t / 2 - the result of measuring the distance to the object in the i-th sounding;
T _i - time points at which the measured range R _i ;
c is the speed of light;
m is the number of range measurements in the series;
t _i is the delay between the moments of radiation of the laser pulse and the reception of the radiation reflected by the object in the i-th sounding.

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