RU2563608C1 - Remote object distance and speed evaluation method - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: remote object distance and speed determination method consists in 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 first sounding series is performed using the incoherent accumulation method and the distance R to an object is determined, then, if the measured distance R exceeds the pre-set size R_min, the measurements are continued in the indicated incoherent accumulation mode and if R doesn't exceed R_min, the monopulse distance and speed measurement mode is included.

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.

3 cl, 1 dwg, 1 tbl

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 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 emission of the laser pulse and the reception of the radiation reflected by the object, with each sounding, the values of the current time moments T _{i are} determined and recorded , 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 is 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 tied, and determine the value of the distance to the object at this moment by the formula:

R = R ₀ + V (TT ₁ ),

where R is the result of determining the distance to the object at time 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 the speed both in 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 of a distant object, 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 the range cells, and statistical processing of the recorded data, produce the first sounding method by the method of incoherent accumulation, namely, accumulate samples of received realizations of the reflected signal in each range cell until the accumulated value exceeds a threshold value, then by a predetermined criterion, for example, by the maximum correlation coefficient of the accumulated array of received realizations with an array of pre-digitized probing pulse, determine the serial number p of the range cell to which the reflected signal belongs, and determine the range R to the object from formula is R = cpΔt / 2, where c - velocity of light; Δt is the duration of the clock interval, after which, if the measured range R exceeds a predetermined value of R _min , then continue to carry out measurements in the specified incoherent accumulation mode, and if R does not exceed R _min , then turn on the single-pulse mode of measuring range and speed, during which series of sounding object at least twice, with each i-th sensing determine its reception time t _i, calculated distance to the object R _i = ct _i / 2, where c - velocity of light, and determining the range to the object and its relative speed Uteem linear interpolation of the measurement results in the form of R (t) = Vt + R ₀ where R (t) - the current range to the object; t is the current time; V is the speed estimate; R ₀ - an estimate of the distance to the object corresponding to t = 0, while the height R _min when determining the height of the aircraft in the process of landing is selected from the condition

h ₂ + Ltgθ + h _g <R _min <R _D ,

where h ₂ - the height of the end point of the glide path;

L is the length of the glide path along the landing strip;

θ is the slope angle of the glide path;

h _g is the vertical distance between the altimeter and the glide path;

R _D is the maximum height at which the probability of a reliable measurement of D in a single-pulse measurement mode meets the specified requirements.

, 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 moment of measurement T ₁ and the speed of the object V can be formed by the formulas:

,

,

,

,

where R ₀ is an estimate of the distance to the object at time T ₁ ;

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 presents a diagram of the landing of an aircraft on an airplane with an aerofinisher [4].

When landing an aircraft in an airplane with an aerofinisher, the following relations are valid

R _min = h ₂ + Ltgθ + h _g ,

where R _min - the height of the aircraft above the landing strip at the beginning of the landing trajectory;

h ₂ - the height of the cable of the aerofinisher over the landing strip;

L is the length of the landing site;

θ is the slope angle of the glide path;

h _g - leash length with hook.

For example, when h ₂ = 2 m; L = 200 m; θ = 10 °; h _g = 2 m minimum measured height R _min ~ 40 m

The characteristics of the range finder-altimeter that implements the proposed method, as well as the measurement conditions are shown in the table.

Altimeter Rangefinder Features Demand Dimensions of the target, m > 5 × 5 The brightness coefficient of the target, ρ 0.2 Meteorological range W, km > 10 Probability of reliable range measurement 0.9 Operating wavelength λ, nm 900 Real sensitivity of the receiving path E _min , fJ 0.3 Laser radiation power at the output of the range finder P ₀ , W thirty Laser pulse duration t _and , ns one hundred Laser frequency F, 1 / s 8000 Divergence of the probe radiation beam ψ, mrad <5 The transmittance of the lens of the receiving channel of the range finder, τ ₀ 0.9 The diameter of the lens of the receiving channel D _CR mm eighteen Frequency of updating information at heights> 200 m, 1 / s 10 Frequency of updating information at altitudes <200 m, 1 / s fifty

The specified range of 40 m is provided subject to the inequality determined by the equation of the laser location [1] provided that the fields of the emitter and receiver are matched:

,

,

where E _min is the minimum signal energy received with a given probability, provided by the sensitivity of the photodetector (real sensitivity);

E _CR - the energy of the signal entering the working site of the sensitive element of the FPU;

E _o = P ₀ t _and is the energy of the probe signal;

P ₀ is the power of the probing signal;

t _and - the duration of the probe signal;

- коэффициент энергетического перекрытия зондирующего пучка целью (коэффициент использования излучения); при зондировании подстилающей поверхности с малых высот K=ρ;

- coefficient of energy overlap of the probe beam by the target (radiation utilization coefficient); when probing the underlying surface from low heights K = ρ;

ρ (x, y) is the spatial distribution of the brightness coefficient of the target;

Ψ (x, y) is the radiation pattern of the output probe beam;

ρ is the average brightness coefficient of the target;

D _CR - diameter of the receiving lens;

- коэффициент пропускания атмосферы на трассе;

- atmospheric transmittance on the track;

µ is an indicator of attenuation;

τ _o - transmittance of the optics of the receiving channel of the range finder;

R - range to the target.

At low altitudes for W> 10 km, the atmospheric transmission τ _a = 1.

With the above initial data and a height of R _min = 200 m, the value of the signal arriving at the receiver E _pr = 1.1 fJ with a large margin exceeds E _min = 0.3 fJ, which means that height measurements can be made with high reliability.

In accordance with the above equation of the laser location, the height R _D at which E _pr = E _min for the conditions is

R _D = R _min [E _ol (R _min ) / E _min ] ^½ = 200 · (1.1 / 0.3) ^½ = 383 m.

This method allows you to:

- Increase the measured height of the aircraft to 1000-2000 m.

- Reduce the minimum measured height to 2 m.

- To provide a minimum information update period of about 1 s at high altitudes and up to 0.1 s at low altitudes.

- 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 solution of the problem - providing measurements from the aircraft of its height and vertical component of speed both in a 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. A method of landing an unmanned aircraft on an aerofinisher. RF patent No. 2399560.

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 of a distant object, which consists in repeatedly probing the object with laser pulses, receiving and registering 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 forming the range cells, and the statistical processing of the recorded data, characterized in that they produce the first series of soundings using the non-coherent method of accumulation, namely, they accumulate samples of received realizations of the reflected signal in each range cell until the accumulated value exceeds a threshold value, then the ordinal number p of the range cell is determined from the maximum correlation coefficient of the accumulated array of received realizations with an array of previously digitized sounding pulse, which the reflected signal relates to, 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, after which, if the measured range R exceeds a predetermined value of R _min , then continue to carry out measurements in the specified incoherent accumulation mode, and if R does not exceed R _min , then turn on the single-pulse mode of measuring range and speed, during which series of sounding object at least twice, with each i-th sensing determine its reception time t _i, calculated distance to the object R _i = ct _i / 2, where c - velocity of light, and determining the range to the object and its relative speed Uteem linear interpolation of the measurement results in the form of R (t) = Vt + R ₀ where R (t) - the current range to the object; t is the current time; V is the speed estimate; R ₀ - an estimate of the distance to the object corresponding to t = 0, while the height R _min when determining the height of the aircraft in the process of landing is selected from the condition

,
where h ₂ - the height of the end point of the glide path;
L is the length of the glide path along the landing strip;
θ is the slope angle of the glide path;
h _r is the vertical distance between the altimeter and the glide path;
R _D is the maximum height at which the probability of a reliable measurement of D in a single-pulse measurement mode meets the specified requirements. 2. The method according to p. 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 p. 1, characterized in that estimates of the distance to the object R ₀ at the initial moment of measurement T ₁ and the speed of the object V are formed by the formulas

,

,
where R ₀ is an estimate of the distance to the object at time T ₁ ;
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.