RU2766534C2 - Simulation and testing complex for laser ballistic measuring system - Google Patents

Abstract

FIELD: measuring technology.

SUBSTANCE: invention relates to control and measuring technology and can be used in testing a laser ballistic measuring system. The result is achieved due to the fact that the output of a single-frequency laser is connected to the input of an optical frequency modulator, its optical output is connected to the input of a collimator, the radiation from which is directed at a stationary projectile. The control input of the optical modulator is connected to the output of a controlled frequency divider, the input of which is connected to the output of a high-frequency generator, the control input of the frequency divider is connected to a control and signal processing unit that sets fixed modulation frequencies corresponding to the Doppler frequency shift for the simulated projectile velocity set at a given time interval, while radiation reflected from the projectile is received by a laser ballistic measuring system that calculates the simulated projectile velocity, and the complex determines the errors in measuring the velocity of the projectile, as well as the error in measuring the angular velocity of rotation of the projectile.

EFFECT: accuracy of measuring the initial velocity of the projectile and the angular velocity of rotation of the laser ballistic measuring system.

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Description

Technical field

The invention relates to the field of electromagnetic methods for measuring the muzzle velocity of a projectile, in particular to the field of testing a laser ballistic measuring system.

State of the art

Testing is the most reliable way to evaluate system performance. (Natural experiment: Information support for experimental research / A.N. Belyunov, G.M. Solodikhin, V.A. Solodovnikov and others / Edited by N.I. Baklashov. - M: Radio and communication, 1982, p. 13-15).

During the test, it is necessary to determine the main characteristics of the laser ballistic measuring system:

- error in measuring the initial velocity of the projectile;

- error in measuring the speed of rotation of the projectile.

Testing a laser ballistic system is a technically and organizationally complex, expensive and lengthy stage. Therefore, simplifying and reducing the cost of testing while maintaining reliability is an extremely urgent task.

An analogue of this technical solution is a laser measuring the speed and / or movement of small objects in places with limited access (patent RU 2610905 for the invention application: 2015122034 dated 06/09/2015 IPC G01S 17/58 (2006.01) published: 02/17/2017 Bull. No. 5)

A laser measuring device for the speed and/or movement of small objects in places with limited access (Fig. 1) includes a source 1 of laser radiation connected by an optical fiber to an optical isolator 2, a fiber amplifier 3 with a laser pump diode 4, an optical splitter 5 acting as a beam splitter plate for separation of optical radiation in a ratio of 1:1, connected by an optical fiber with an FC / APC connector 6, which acts as a low-reflecting mirror, and a collimator 7 with a beam diameter of 0.8-1.2 mm, and an optical receiver 8. The output of the optical receiver 8 is connected to the input of the oscilloscope 9, connected via a USB interface to a personal computer 10. During the experiment, when measuring the speed of a bullet 12 in the barrel 11 of an air rifle, protective plexiglass 13 was also used. .4], pos.5, pos.6, [pos.7 + pos.12], pos.8 represent a fiber optic analogue of the Michelson interferometer.

The source 1 of laser radiation is a semiconductor single-frequency laser stabilized with a Bragg grating, operating at a current of 120 mA, with a radiation power of about 20 mW and a wavelength of 1064 nm with a generation line width of not more than 3 MHz, which provides a large coherence length and, therefore, provides the ability to measure the dynamics of the movement of an object in the range of movement up to 100 m and in the range of speeds from 0.1 to 180 m/s. The optical isolator 2 allows the radiation from the laser 1 to pass in only one direction and is used to ensure that the reflected radiation traveling in the opposite direction does not adversely affect the laser diode 4.

The device works as follows.

At the moment of firing from an IZH-61 air rifle with a lead bullet weighing 0.5 grams, the piston is released by the trigger mechanism, which leads to its movement inside the glass and, accordingly, to pressure build-up. Through a special hole, compressed air enters the bore, which leads to the acceleration of the bullet. The rifle was fixed on an optical table, the protective plexiglass 12 was fixed at an angle of about 60° relative to the barrel 11 of the rifle. Next, a shot is fired from a rifle by pressing the trigger with the simultaneous supply of a sync pulse to the synchronization input of the oscilloscope 9 using a special sensor. The oscilloscope 9 in the single recording mode upon arrival of the clock pulse records 16776704 samples with a removal period dt=2Hc. The waveform is a signal from the optical receiver 9, i.e. essentially a finished interferogram.

Due to the Doppler effect, beats will be observed in this oscillogram with a frequency directly proportional to the speed of the measured object (bullet), so it is necessary to calculate the spectral components of the oscillogram at different times. The spectrogram is computed using the Fast Fourier Transform (FFT), which is then converted to bullet velocity.

The disadvantage of this described device is the lack of reliability of the measured speeds. Testing is the most objective way to assess the performance of a system. Closest to the claimed device (prototype) is a device for measuring the external ballistic characteristics of the projectile, designed to measure the speed of the projectile, the angular velocity of rotation of the projectile around the longitudinal axis and the amount of nutation of the projectile (Patent RU2515580 for the invention application: 2013112556/07 dated 20.03.2013 IPC G01S 13 /58 (2006.01) published: May 10, 2014 Bull. No. 13). The essence of the prototype lies in the fact that, in a device for measuring the external ballistic characteristics of a projectile, containing a Doppler radar, a spectrum width indicator, in which a key, a delay line, an analog-to-digital converter, a memory unit, a data processing unit, an indicator of the initial velocity of the projectile and an angular indicator the speed of rotation of the projectile, and the output of the Doppler radar is connected to the first input of the key, the second input of which is connected to the output of the delay line, the input of which is connected to the output of the induction sensor placed on the bore of the missile body, and the output to the input of the analog-to-digital converter, the output of which is connected to the input of the memory block, the output of which is connected to the input of the signal processing unit, the first, second and third outputs of which are connected respectively to the inputs of the projectile initial velocity indicator, the spectrum width indicator and the projectile angular velocity indicator.

In addition, the data processing unit consists of a data reliability analyzer, a spectrum width determination unit, a projectile angular velocity determination unit, while the input of the signal processing unit is the input of the data reliability analyzer, the output of which is connected to the input of the spectrum width determination unit and the angular velocity determination unit projectile rotation, the outputs of the data reliability analyzer, the spectrum width determination unit and the projectile angular velocity determination unit are the first, second and third outputs of the signal processing unit, respectively.

The operation algorithm of the data reliability analyzer consists in evaluating the reliability of discrete values of the current projectile velocity for each position in the obtained sequence of data contained, selecting, taking into account the results obtained in this sequence, a section containing predominantly reliable data, from which the initial velocity of the projectile is determined, while assessing the reliability data on the current velocity of the projectile use criteria that take into account the specified requirements for the accuracy of measuring the initial velocity of the projectile; when forming a section of the said sequence for calculating the initial velocity of the projectile, the beginning of this section is determined by the presence of at least three consecutive positions with reliable data, and its end is determined by the presence of two or more positions with invalid data; the observation start delay time used in calculating the muzzle velocity of the projectile is the sum of the set delay and the total duration of the realization of the Doppler echo signal preceding the first position in the data section generated for calculating the muzzle velocity of the projectile; if there are single positions with unreliable data in the selected section of the sequence of discrete values of the current projectile speed, the data contained in such single positions are replaced by the average value of reliable data from two positions of this section directly adjacent to them, the reliability of the data on the current projectile speed is checked by exceeding the actual ratio the signal/noise of its value, which is necessary to ensure the specified accuracy of determining the initial speed of the projectile, the reliability of data on the current speed of the projectile is estimated by changes in the values of the current speed of the projectile, presented at adjacent positions in the resulting sequence, while first, zones are detected by the magnitude of these changes, containing unreliable data, and then, based on reliable data obtained from positions immediately adjacent to these zones, the expected speed values \u200b\u200bare determined for each position in the detected zone and each position is localized with insufficient correct data, and those positions for which the analyzed changes in the values of the current velocity of the projectile do not exceed the value of the specified error in measuring the initial velocity of the projectile are considered reliable, the velocity of the projectile is determined in accordance with the expression

where Δf is the Doppler frequency, λ is the wavelength, Δϕ is the viewing angle.

In addition, the block for determining the spectrum width operates in accordance with the algorithm, the essence of which is to calculate the modulus of the fast Fourier transform

определение величины порога:where y _k =y(k/F _d ) is the input signal y(t) digitized by the analog-to-digital converter, F _d is the sampling frequency of the original signal, N is the number of DFT samples, S _n is the actual amplitude of the n-th spectral harmonic, the frequency which can be defined as:

definition of the threshold value:

where Рlt is the probability of a false alarm, which in practice is usually taken equal to 10-5, σ ² _w is the noise dispersion, the value of which can be calculated by analyzing the FFT of the radar output signal in the absence of moving objects in its visibility zone for compliance with the Rayleigh distribution law, nulling harmonics , which have not exceeded the value of the threshold S _then and are in the region of the expected Doppler frequencies:

where f _exp.min , f _exp.max. - the lower and upper limits of the expected Doppler frequency range, respectively, determining the width of the signal spectrum:

where f _c.min is the lower limit of the signal spectrum, f _c.max is the upper limit of the signal spectrum, Δf is the width of the signal spectrum, determining the projectile maximum section area by the plane perpendicular to the projectile line of sight by the spectrum width, determining the projectile nutation value by changing this area at each position (Fig. 5).

In addition, the unit for determining the angular velocity of the projectile operates in accordance with the algorithm, the essence of which is to calculate the harmonic frequencies of the secondary modulation in the amplitude-frequency spectrum of the selected measurement area, while obtaining the amplitude-frequency spectrum, an algorithm is used to compensate for the effect of phase modulation of the reflected radar signal :

- determination of the complex spectral amplitude at the output of the FFT algorithm:

- выбранный участок отраженного эхо-сигнала, K - число отсчетов выбранного участка сигнала,Where

- the selected section of the reflected echo signal, K - the number of samples of the selected section of the signal,

- determination of the boundary of the spectrum of the dominant harmonic:

where [N _e.min , N _e.max ] is the interval of spectral readings containing the frequencies of the dominant harmonic, n _pl is the frequency position of the maximum spectral amplitude, Δn _pl is the a priori specified width of the search interval for the energy center of the spectrum of the dominant harmonic,

- determination of the energy center of the spectrum of the dominant harmonic, by the squares of the spectral amplitudes:

, n_с - априорно известная ширина спектра доминирующей гармоники, выделение спектра сигнала, отраженного от снаряда, и осуществление дополнения его нулями:where

, n _c - a priori known width of the spectrum of the dominant harmonic, selection of the spectrum of the signal reflected from the projectile, and the implementation of its completion with zeros:

where n _f is the width of the spectrum of the signal reflected from the projectile, including the harmonics of the secondary modulation, carrying out a cyclic shift of the spectrum so that the energy center of the spectrum is in the zero position in accordance with the expression:

и получение корректирующего сигнала:- implementation of the operation of the inverse FFT spectrum

and receiving a corrective signal:

и выполнение операции БПФ:- implementation of the multiplication of the original signal section by the complex conjugate corrective signal

and performing the FFT operation:

- extracting from the spectrum of the echo signal Z _n two pairs of harmonics of the secondary modulation, located closest to the dominant harmonic, and determining the values of the frequencies f ₁ and f ₂ at which they reach a maximum,

- calculation of the angular velocity of rotation of the projectile around the longitudinal axis according to the formula:

ω=2πf _vp

where f _vp =f ₁ -f ₂ )/2, f ₁ and f ₂ - frequency corresponding to the maxima of the first pair of harmonics of the secondary modulation of the Doppler echo signal. In FIG. 2 shows a diagram of an installation for evaluating the external ballistic characteristics of a projectile, where 14 is a device for measuring the external ballistic characteristics of a projectile, 15 is a throwing device, 16 is an induction sensor, 17 is a projectile, in Fig. 3 is a block diagram of a device for measuring the external ballistic characteristics of a projectile, where 18 is a Doppler radar, 19 is a key, 20 is a delay line, 21 is an analog-to-digital converter, 22 is a memory unit, 23 is a data processing unit, 24 is an indicator of projectile speed, 25 - indicator of the width of the spectrum, 26 - indicator of the angular velocity of the projectile, in Fig. 4 is a block diagram of a data processing unit, where 27 is a data reliability analyzer, 28 is a spectrum width determination unit, 29 is a projectile angular velocity determination unit.

The device for measuring the external ballistic characteristics of the projectile operates as follows. When the combat button is pressed, the device 14 for measuring external ballistic characteristics is simultaneously launched and the throwing device 15 is triggered, while at the moment the projectile 17 exits the barrel, the induction sensor 16 is triggered (Fig. 2).

The Doppler radar 18 emits electromagnetic energy in the direction of the projectile, the signal reflected from the projectile is fed to the first input of the key 19, the second input of which receives the signal from the output of the delay line 20, the input of which receives the signal from the output of the inductive sensor 17 (Fig. 3) . The choice of the delay time is due to the need to measure the initial velocity of the projectile, since it is at the moment of the shot that the moment when the projectile velocity reaches its maximum value is observed. The signal from the output of the key 19, through the analog-to-digital converter 21, is fed to the input of the memory block 22, where it is recorded. The processing of the received data is carried out in the data processing unit 23, while the data reliability is analyzed in the data reliability analyzer 27 (Fig. 4).

The data reliability analyzer 27 selects a section containing increased reliable data, while the beginning of the section is determined by the presence of at least three successive positions with reliable data, and its end is determined by the presence of two or more positions with invalid data, which determine the initial velocity of the projectile .

Calculation of the initial velocity of the projectile is carried out at the time t ₀ =t _ass +t _Σ , where t _ass is the set delay, t _Σ is the total duration of the Doppler echo signal realization preceding the first position in the data section formed to calculate the initial velocity of the projectile. If there are single positions with unreliable data in the selected section of the sequence of discrete values of the current projectile velocity, the data contained in such single positions is replaced by the average value of reliable data from two positions of this section immediately adjacent to them.

Thus, the data validity analyzer 27 enables sampling of the area of increased data validity and provides validation of the current speed.

From the output of the analyzer 27 data validity signals are fed to the inputs of the block 28 to determine the width of the spectrum and block 29 to determine the angular velocity of the projectile.

In addition, the signal from the output of the analyzer 27 reliability of the data is input to the indicator 24 of the speed of the projectile. Block 28 for determining the width of the spectrum provides calculation of the fast Fourier transform (FFT), determination of the width of the signal spectrum, determination of the area of the maximum section of the projectile by the plane perpendicular to the line of sight of the projectile from the spectrum width, determination of the amount of nutation of the projectile by changing the area at each position. The signal from the output of the block 28 to determine the width of the spectrum is input to the indicator 25 of the width of the spectrum. Block 29 for determining the angular velocity of rotation of the projectile determines the angular velocity of rotation of the projectile relative to the longitudinal axis for the selected area of measurement.

The disadvantage of this device is the insufficient reliability of the measured external ballistic characteristics, which is set by the reliability analyzer on the basis of calculated rather than experimental data. The test is the most objective assessment of the performance of a laser ballistic measurement system. The technical objective of the invention is a simulation test complex for testing a laser ballistic measuring system and establishing its main performance characteristics:

- errors in measuring the initial velocity of the projectile;

- errors in measuring the speed of rotation of the projectile.

соответствующие доплеровскому сдвигу частоты для заданной на данном временном интервале имитируемой скорости снаряда V_iз, при этом отраженное от снаряда излучение принимается лазерной баллистической измерительной системой, которая вычисляет имитируемую скорость снаряда

, а комплекс определяет погрешности измерения скорости движения снаряда ΔV_i=V_iз - V_iи на различных временных интервалах, где λ₀ - длина волны одночастотного лазера.The specified technical result is achieved by the fact that a simulation and test complex for evaluating the technical characteristics (errors in measuring the speed of the translational movement of an artillery projectile and the speed of its rotation) of a laser ballistic measuring system, for compliance with the requirements of the tactical and technical task), containing a projectile for creating a full-scale environment in the measuring zone, laser ballistic measuring system, single-frequency laser, control and signal processing unit. A distinctive feature of the claimed invention is that the output of a single-frequency laser, a laser ballistic measuring system is connected to the input of an optical frequency modulator, and its optical output is connected to the input of a collimator, the radiation from which is directed to a stationary projectile, while the control input of the optical frequency modulator is connected to the output controlled frequency divider, the input of which is connected to the output of a high-frequency generator, and the control input of the frequency divider is connected to a control and signal processing unit, which sets fixed modulation frequencies

corresponding to the Doppler frequency shift for the simulated projectile speed V _iz specified at a given time interval, while the radiation reflected from the projectile is received by the laser ballistic measuring system, which calculates the simulated projectile speed

, and the complex determines the error in measuring the velocity of the projectile ΔV _i =V _iz - V _ii at different time intervals, where λ ₀ is the wavelength of a single-frequency laser.

Another distinctive feature of the claimed invention is that the longitudinal axis of the projectile is connected with the rotor of the electric motor and the _{exemplary tachometer} , while the measurement _error of the projectile _rotation speed is determined by the _ratio - speed value measured by the laser ballistic measuring system.

Implementation of the invention.

In FIG. 6 shows a functional diagram of a simulation and test complex for a laser ballistic measuring system.

The simulation and test complex for a laser ballistic measuring system contains a laser ballistic measuring system with a single-frequency laser 30, a fiber-optic receiving system 31, a control and information processing unit 32. The output of a single-frequency laser 30 is connected to the input of a frequency modulator 33, and its output is connected to the input of a fiber-optic collimator 34, the radiation from which is directed to a projectile 35 that is stationary in the longitudinal direction, the longitudinal axis of which is connected to an electric motor 36 and a tachometer 37. The modulation frequency of the modulator 33 is set by a high-frequency generator 38 and a frequency divider 39.

The device functions as follows. On a fixed, longitudinal direction of the projectile 35, the radiation of a single-frequency laser 30, which is part of the laser Doppler measuring ballistic system, is directed. The radiation of a single-frequency laser 30 passes a frequency modulator 33. The control and information processing unit 32 sets the frequency divider 39, the frequency modulation of the radiation of a single-frequency laser, corresponding to the specified projectile speeds V _iz , at time intervals t ₁ -t _n (Fig. 7). The radiation reflected from a stationary projectile is received by a fiber-optic receiving system 31 laser ballistic measuring system, which processes the received information and calculates the current (simulated) projectile velocity V _i at a given time interval from the values of dominant frequencies in the spectrum of the reflected signal. Next, the measurement errors are determined by the speed of the projectile (simulated) at different time intervals ΔV _i =V _iz -V _ii .

At the same time, the projectile 35 is driven in rotation about its longitudinal axis by an electric motor 36, and _the specified angular velocity ω _iz is measured by _a tachometer 37. calculates the angular velocity of the projectile around the longitudinal axis ω ii = _{2πƒ in} , where ƒ _in =(ƒ ₁ -ƒ ₂ )/2. According to the measured angular velocity of rotation of the projectile ω _and , and the given angular velocity ω _iz is determined by the measurement error of the angular velocity of rotation of the projectile Δω _i =ω _{iz -ω ii} . The claimed device will allow testing a laser ballistic measuring system and establishing its performance characteristics:

- error in measuring the initial velocity of the projectile;

- error in measuring the speed of rotation of the projectile. All system components are standard for telecommunications applications.

Used sources of information:

1. Full-scale experiment: Information support for experimental research / A.N. Belyunov, G.M. Solodikhin, V.A. Solodovnikov and others / Ed. N.I. Baklashov. - M: Radio and communication, 1982, p.13-15.

2. Patent RU 2610905 for invention application: 2015122034 dated 06/09/2015 IPC G01S 17/58 (2006.01) published: 02/17/2017 Bull. No. 5.

3. Patent RU 2515580 for invention application: 2013112556/07 dated 03/20/2013 IPC G01S 13/58 (2006.01) published: 05/10/2014 Bull. No. 13.

Claims (1)

A simulation and test complex for a laser ballistic measuring system, containing a projectile for creating a natural environment in the measuring area, a laser ballistic measuring system with a single-frequency laser, a control and signal processing unit, characterized in that the output of the single-frequency laser of the laser ballistic measuring system is connected to the input of an optical frequency modulator, and its optical output is connected to the input of the collimator, the radiation from which is directed to a stationary projectile, while the control input of the optical frequency modulator is connected to the output of a controlled frequency divider, the input of which is connected to the output of a high-frequency generator, and the control input of the frequency divider is connected to the control unit and signal processing, which are given fixed modulation frequencies

, corresponding to the Doppler frequency shift for the simulated projectile velocity V _i3 specified at a given time interval, while the radiation reflected from the projectile is received by the laser ballistic measuring system, which calculates the simulated projectile velocity

and the complex determines the errors in measuring the speed of the projectile ΔV _i =V _i3 -V _iu at different time intervals, while the longitudinal axis of the projectile is connected with the rotor of the electric motor and the exemplary tachometer, and the error in measuring the angular velocity of the projectile is determined by the relation Δω _i = ω _i3 - ω _iu , where ω _i3 is the specified angular velocity of the projectile, determined by the tachometer, ω _iu is the angular velocity of the projectile, measured by a laser ballistic measuring system, λ ₀ is the wavelength of a single-frequency laser.

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