RU2558694C1 - Determination of aircraft altitude - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: in compliance with this process, underlying surface is subjected to N-fold probing by laser radiation pulses and incoherent accumulation of the received signal reflected from the object. Results of statistical processing of obtained data are used to define time position of reflected signal Th relative to the moment of probing pulse radiation and to calculate aircraft altitude by formula h = c·Th/2 where c is the light velocity. Note here that the range of altitude is divided into K zones. Accumulation volume N in every zone is set depending on pulse clock frequency dividing the time into intervals, tolerable altitude measurement error in j^th altitude zone, probing frequency and preset data updating period in the said j^th altitude zone.

EFFECT: required accuracy of measurements at preset detection characteristics and required data updating frequency.

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Description

The present invention relates to measuring technique and can be used in any field where it is necessary to periodically determine the distance to a distant object, in particular, to control the relief of the underlying surface and control the flight 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 need to use a laser whose monopulse radiation energy is sufficient to provide a given range. Typically, long range is unattainable when using miniature lasers. This prevents the reduction of dimensions and weight of the equipment, which does not allow to implement the method for small-sized aircraft.

The known method of incoherent accumulation [2, 3], which allows to increase the range of a small rangefinder with a low probe radiation energy. This method is also used to determine the altitude of the aircraft [4] by a semiconductor laser range finder.

The closest in technical essence to the proposed method is a method for determining the altitude of an aircraft [2], by incoherent accumulation during pulsed laser location-based sensing, which consists in N-times probing the underlying surface with laser pulses, receiving and recording the signal reflected by the object with its reference to pulses stable clock frequency, dividing the time into numbered clock intervals, determine the temporal position of the reflected signal T _h relative to radiation radiation of the probe pulse and calculate the height of the aircraft according to the formula h = cT _h / 2, where c is the speed of light.

In this procedure, the measurement error depends on the aircraft altitude, since the signal-to-noise ratio in the receiving path decreases at high altitude, and its noise distorts the waveform, which affects the error in temporarily fixing the accumulated data array. With a further increase in aircraft altitude, there is a risk of complete signal loss due to noise and, consequently, loss of height measurement. In this case, it is also possible to register a false signal, due to the accumulation of noise emissions, and the corresponding false measurement of the aircraft altitude. Such errors make it impossible to regularly issue data on aircraft altitude, for example, during 3D mapping [5], when each result in the measurement grid must be reliable. In other procedures, the omission of individual measurements is allowed, but higher accuracy or frequency of data output is required, for example, when landing an aircraft.

The objective of the invention is to provide the necessary measurement accuracy Δh at a given probability of detecting a signal D and the probability of false measurement W, as well as at the required frequency of updating information F in the process of performing various flight tasks.

This problem is solved due to the fact that in the known method for determining the altitude of an aircraft (LA) by incoherent accumulation during pulsed laser location-based probing, which consists in N-times probing the underlying surface with laser pulses, receiving and recording the signal reflected by the object with its binding to pulses stable clock frequency, dividing time into numbered clock intervals determine the temporal position of the reflected signal relative to the time T _h of radiation Ndira pulse and calculating the height of the aircraft by the formula _h = cT h / 2, where c - velocity of light, break height range in K bands, the ceiling of each h _K zone is set according to the flight mission, and the amount of accumulation of N is set in each j-th zone taking into account the amplitude of the reflected signal within

,

,

Where

c is the speed of light;

ΔT is the period of the clock frequency;

Δh _j is the maximum permissible error of height measurement in the j-th zone of heights;

F is the sounding frequency;

T _j - a given period of updating information in the j-th height zone.

, а если не превышает, то из условия N_j=FT_j.In the process of sensing, it is possible to determine the amplitude of the reflected signal and, if it exceeds a predetermined value, the accumulation volume N _{j is} set from the condition

, and if it does not exceed, then from the condition N _j = FT _j .

равным N_j=(η₁/η)², где η₁ - отношение сигнал/шум, обеспечивающее заданные обнаружительные характеристики при N_j=1.You can also determine the ratio of the amplitude of the reflected signal to noise η and set the accumulation volume N _j within

equal to N _j = (η ₁ / η) ² , where η ₁ is the signal-to-noise ratio, providing specified detection characteristics at N _j = 1.

The boundaries of the zones can, for example, be set in accordance with the separation scheme.

In FIG. 1 shows a flight profile of an aircraft.

The height range is divided into three zones.

The first zone 0≤h≤h ₁ is determined by the take-off and landing modes. Altitude measurements in this zone are needed to ensure optimal flight paths in automatic pilot mode. The zone is characterized by a high level of signal-to-noise ratio and, accordingly, high reliability of measurements. In this zone, a high frequency of updating information is required, as well as high accuracy.

The second zone h ₁ ≤h≤h ₂ - intermediate. Measurements in it are made more rarely and with low requirements for accuracy and reliability. The signal to noise ratio is relatively large. Altitude measurements in this area are used to control flight altitude outside the operating mode.

The third zone h ₂ ≤h≤h ₃ - working. The signal-to-noise ratio in it is minimal, and the requirements for the reliability of measurements are the most stringent.

In addition to the specified partition, an increase or decrease in the number of working zones is possible.

Example 1. Flight mission - mapping the terrain from the third zone.

Table 1 Sensing Modes and Measurement Characteristics Zone ₉ T, ns F, 1 / s Δh _j , m T _j , ms N N * 0≤h≤h ₁ = 200 m 13,333 8800 0.5 10 16 88 h ₁ ≤h≤h ₂ = 500 m 13,333 8800 2 1000 one 8800 h ₂ ≤h≤h ₃ = 1000 m 13,333 8800 one one hundred four 880 Note: N * = FT _j - maximum permissible accumulation volume.

Example 2. Flight mission - transit flight according to the separation scheme with binding of the second and third zones to the corresponding echelons.

table 2 Sensing Modes and Measurement Characteristics Zone ΔT, ns F, 1 / s Δh _j , m T _j , ms N N * 0≤h≤h ₁ = 200 m 13,333 8800 0.5 10 16 88 h ₁ ≤h≤h ₂ = 500 m 13,333 8800 10 1000 one 8800 h ₂ ≤h≤h ₃ = 1000 m 13,333 8800 10 1000 one 8800

может быть определен по формуле N**=(η₁/η)², где η₁ - отношение сигнал/шум, обеспечивающее заданные обнаружительные характеристики при N_j=1.The maximum accumulation volume N * indicated in the tables is limited by a predetermined time T _{j for} updating the height information. This volume can be reduced if predetermined detection characteristics (probability of correct detection and probability of false alarm) are provided with the actual signal-to-noise ratio. The required accumulation volume N ** within the specified limits

can be determined by the formula N ** = (η ₁ / η) ² , where η ₁ is the signal-to-noise ratio, providing specified detection characteristics for N _j = 1.

Example 3. Flight mission - mapping the terrain from the third zone. The accumulation volume is determined by the current signal-to-noise ratio for η ₁ = 5.

Table 3 Sensing Modes and Measurement Characteristics Zone ΔT, ns F, 1 / c Δh _j , m T _j , ms η N N ** N * 0≤h≤h ₁ = 200 m 13,333 8800 0.5 10 10 16 16 88 h ₁ ≤h≤h ₂ = 500 m 13,333 8800 2 1000 one one 25 8800 h ₂ ≤h≤h ₃ = 1000 m 13,333 8800 one one hundred 0.2 four 625 880 Note: N ** = (η ₁ / η) ² is the accumulation volume sufficient for measurements at the actual signal-to-noise ratio η.

As can be seen from the above examples, the present invention allows you to effectively reconcile conflicting requirements for measurement accuracy, detection characteristics and the frequency of updating information when determining the height of the aircraft in different flight modes and, thereby, expand the capabilities of its operation, in particular by increasing the range of operating heights .

This confirms the fulfillment of the task - ensuring the necessary measurement accuracy Δh at a given probability of detecting a signal D and the probability of false measurement W, as well as at the required frequency of updating information F in the process of performing various flight tasks.

Information sources

1. V.A. Smirnov. Introduction to optical electronics. - M .: Soviet Radio, 1973, p. 189.

2. V.G. Vilner et al. Evaluation of the capabilities of a radar pulse range meter with accumulation. "Photonics", No. 6, 2007, p. 22-26 is a prototype.

3. V.G. Vilner et al. A method of incoherent accumulation of radar signals. RF patent No. 2455615 for z-ke No. 20111101613/28, 01/18/2011.

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

5. Medvedev EM Laser location and aerial photography. Digest of articles. - M .: Prospect, 2006 .-- 60 p.

Claims (4)

1. A method for determining the altitude of an aircraft (LA) by incoherent accumulation during pulsed laser location-based sensing, which consists in N-times probing the underlying surface 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, determine the temporary position of the reflected signal T _h relative to the moment of radiation of the probe pulse and calculate the height of the a apparatus according to the formula h = c T _h / 2, where c is the speed of light, characterized in that they divide the height range into K zones, the ceiling of each zone h _{K is} set according to the flight task, and the accumulation volume N is set in each j-th zone with taking into account the amplitude of the reflected signal within

,
Where
c is the speed of light;
ΔT is the period of the clock frequency;
Δh _j is the maximum permissible error of height measurement in the j-th zone of heights;
F is the sounding frequency;
T _j - a given period of updating information in the j-th zone of heights. 2. The method for determining the altitude of an aircraft according to claim 1, characterized in that the amplitude of the reflected signal is determined and, if it exceeds a predetermined value, the accumulation volume N _{j is} set from the condition

, and if it does not exceed, then from the condition N _j = FT _j . 3. The method for determining the altitude of an aircraft according to claim 1, characterized in that the ratio of the amplitude of the reflected signal to noise η is determined and the accumulation volume N _j is set within

equal to N _j = (η ₁ / η) ² , where η ₁ is the signal-to-noise ratio, providing specified detection characteristics at N _j = 1. 4. The method of determining the height of the aircraft according to claim 1, characterized in that the boundaries of the zones are set in accordance with the separation scheme.