RU2816756C1 - Autonomous method for determining initial velocity of artillery projectile with remote air deposition - Google Patents

Abstract

FIELD: munitions.

SUBSTANCE: control of remote detonation of rifled artillery shells in the air. An autonomous method for determining the initial velocity of an artillery projectile with remote detonation in the air, including measuring the angular velocity of rotation of the projectile, calculating the initial velocity from it, characterized in that plane polarized laser radiation is directed onto the projectile by a polarization analyser installed in the rear part of the projectile, transforming it into periodically changing radiation, the frequency of which is equal to twice the angular velocity of rotation of the projectile, the variable component of the resulting radiation is converted into an electrical signal by a photodetector and its frequency is measured, and the initial velocity of the projectile is calculated from the frequency of the electrical signal: Vo = πfd/2tanα, where d is the barrel gauge, α is the angle of inclination of the barrel rifling at the muzzle section of the gun barrel, f is the frequency of the electrical signal. The frequency of the electrical signal is converted with a conversion factor of N>1.

EFFECT: improved range accuracy of air blasts with a limited counting time.

2 cl, 1 dwg

Description

TECHNICAL FIELD

The present invention relates to the control of remote detonation of projectiles in the air of rifled artillery.

BACKGROUND OF THE ART

Programmable air blast projectiles have found widespread use in artillery. The computer complex of the artillery system determines and enters into the projectile the specified time of its detonation after the shot. The actual detonation time may differ from the specified one due to different charge properties and wear of the gun barrel. Measuring and entering into the projectile the value of its initial velocity significantly increases the effectiveness of the artillery system.

An analogue of this technical solution is a programmable projectile (patent RU 2535313 for the invention, application: 2012137290/03, IPC F42C (2006.01) published: 12/10/2014. Bulletin No. 34).

The programmable projectile contains an energy storage device, an electronic unit, a fuse and a signal and energy reception sensor. Programming, as well as energy transfer, occurs when the projectile passes through the gun barrel, muzzle brake or similar element that acts as a wave guide. The actual detonation time may differ from the specified one due to different charge properties and wear of the gun barrel. Measuring and entering into the projectile the value of its initial velocity significantly increases the effectiveness of the artillery system.

Another analogue is a method for measuring the muzzle velocity of a projectile (patent RU 2406959 C1 for the invention, application: 2009126134/02, IPC F41A, B21C (2006.01) published: 12/20/2010. Bulletin No. 35). In this analogue it is proposed to use the barrel or muzzle brake as a wave guide. In this case, the effect of Doppler changes in the frequency of the received signal is used. The patent description also discusses a method for measuring the speed of a projectile using a pair of inductive coils located behind the muzzle brake at a certain distance from each other. In this case, the speed is determined by measuring the time interval between the projectile and the distance between the coils. In known systems with guided ammunition, for example, AHEAD, the distance between the inductive coils is 10 cm. The small distance between the coils, the shape of their electromagnetic field, the ambient temperature and the propellant gases limit the accuracy of measuring the velocity of the projectile. The measured value of the velocity of the projectile exiting the gun barrel enters the computer complex and the required delay time for the detonation of the projectile is determined. This value must be introduced into the projectile through communication devices before the projectile is completely released from the barrel. A short period of time of the order of 10 ^-4 seconds for performing these procedures places stringent requirements on the communication channel and computing devices of the complex. At the same time, the accuracy of solving the problem is also limited.

The disadvantage of the considered method of measuring the muzzle velocity of a projectile is also the complication of the design of artillery guns.

The next analogue is artillery ammunition (patent RU 2310154 C1 for invention, application: 2006114810/02, IPC F42B (2006.01) published: November 10, 2007. Bulletin No. 31).

In this analogue, increasing the accuracy of remote initiation of detonation of small-caliber rotating artillery shells is achieved by the fact that a rotation speed sensor is placed in the projectile body, made primarily in the form of a magnetometer connected to the Earth’s magnetic field. Using the direct relationship between the angular and linear velocities of the rotating product in the initial part of the flight, the initial speed of movement of each projectile is determined, according to which it is adequate to automatically regulate the distance (time) of fuse initiation. The speed of rotation of a projectile around its longitudinal axis is measured by counting the number of revolutions per unit time, using the Earth's magnetic field. When the ammunition rotates around its axis and intersects the lines of force of the Earth's magnetic field, an EMF of variable magnitude and polarity arises in the form of a periodic pulse signal, which uniquely characterizes the linear speed obtained by the projectile when fired. Depending on the actual muzzle velocity compared to the established baseline, the delay circuit produces a corresponding delay in the initiation of projectile detonation, with less range error and therefore less distance from the target, which significantly increases the lethality of the projectile. At the same time, the ammunition required to complete the combat mission is significantly reduced.

When calculating the root-mean-square error in determining the initial velocity of a projectile of ±0.15%, the deviation of the initial velocity of a small-caliber projectile at the 3σ level will be ±4.5 m/s. Automatic control of the time (distance) of detonation significantly reduces the range error, so the aerial detonation of these small-caliber projectiles at the 3σ level is characterized by errors:

- at a distance of 1 km ±7.8 m;

- at a distance of 2 km ±13.4 m.

When magnetometer 7 rotates as part of a projectile along a flight path at speeds characteristic of small-caliber projectiles (100 thousand revolutions per minute), an EMF of 10 mV appears in it in the Earth's magnetic field.

The disadvantage of this method of measuring the speed of rotation of a projectile is the error in measuring the speed of rotation of the projectile due to the precessional and nutational movements of the projectile.

The closest invention, prototype (patent RU 2703835 C1 for invention application: 2018135544 IPC F41F 1/00 (2006.01), G01P 3/481 (2006.01), published: 10/22/2019 Bulletin No. 30), is an inertial method for determining the initial speed of a controlled rifled gun projectile.

In the prototype, using a miniature flywheel installed inside the projectile, connected to the projectile body by a bearing assembly containing thrust and radial bearings, the axes of which coincide with the longitudinal axis of the projectile, and permanent magnets located on the flywheel, its rotation speed relative to the flywheel is measured at the initial section of the projectile flight path , seeking to maintain its initial angular orientation, over the time interval between a given number of voltage pulses on an inductor coil connected to the projectile body and containing an open ferromagnetic core. The speed of rotation of the projectile determines its flight speed, taking into account the rifling pitch at the muzzle section of the gun barrel. When fired, the device is subject to enormous inertial forces directed along its longitudinal axis. Therefore, in addition to the radial ball bearing, the bearing assembly also includes a thrust bearing. Currently existing technical solutions, materials and miniature ball bearings make it possible to realize a product suitable for installation in small and medium caliber artillery shells.

When measuring the speed of rotation of the projectile body relative to the initially stationary flywheel, the flywheel begins to rotate under the influence of the coupling moments between them.

The projectile's flight speed is determined at the initial stage of its flight by its rotation speed, taking into account the rifling pitch at the muzzle of the gun barrel. To ensure the possibility of placing the device in small and medium caliber projectiles, the diameter of the device must be sufficiently small.

To maintain the functionality of the device at high linear accelerations of the projectile in the gun barrel, it is necessary to make the rotating part with a flywheel of minimal mass.

The disadvantage of the prototype is the presence of a rotating measuring flywheel, which must operate at high linear and angular accelerations of the projectile.

Thus, there is a need in the art for a method for measuring the muzzle velocity of an artillery projectile that is free from these disadvantages.

The technical objective of the invention is to simplify the method.

The essence of the proposed invention is that plane polarized laser radiation is directed onto the projectile by a polarization analyzer installed in the rear part of the projectile, it is converted into periodically varying radiation, the frequency of which is equal to twice the angular velocity of rotation of the projectile, the variable component of the resulting radiation is converted by a photodetector into an electrical signal and its frequency is measured, and the initial velocity of the projectile is calculated from the frequency of the electrical signal:

where d is the barrel caliber,

α is the angle of inclination of the barrel rifling at the muzzle section of the gun barrel,

ƒ - frequency of the electrical signal.

To reduce the frequency measurement error, within a limited counting time, the frequency of the electrical signal from the photodetector is converted by a frequency converter, with a conversion factor N>1.

This provision is explained as follows. Plane polarized laser radiation is directed at the rear of the moving projectile. In the rear part of the projectile, a radiation polarization plane analyzer and a photodetector are installed sequentially along the beam path. When the projectile rotates with angular velocity Ω, the analyzer of the plane of polarization of the radiation incident on the projectile rotates with it. The intensity of radiation passing through the analyzer and incident on the photodetector, in accordance with Malus’s law:

where I ₀ is the intensity of plane-polarized radiation incident on the analyzer;

ϕ is the angle between the planes of polarization of laser radiation and the polarization analyzer.

Since the projectile rotates with angular velocity Ω, the angle between the plane of polarization of the laser radiation and the polarization analyzer will change according to the law:

Let's substitute (2) into (1), we get:

.

As follows from formula (3), the intensity of the radiation reflected from the projectile contains constant and variable components. The variable component of the signal changes at twice the frequency with respect to the angular velocity of rotation of the projectile ƒ=2Ω/2π=Ω/π.

The initial velocity of the projectile V ₀ is related to its rotation speed Ω, the angle of inclination of the barrel rifling α at the muzzle of the gun barrel, as well as the barrel caliber d, and is determined by the formula:

So, for example, with projectile speed V ₀ =1000 m/sec, barrel caliber d=20 mm, rifling angle at the muzzle of the gun barrel α=7°, the angular velocity of the projectile will be:

Ω=12278.5 rad/sec., or 1955 rpm.=117310 rpm. In this case, ƒ=3910 Hz, and after the frequency multiplier 21, the frequency will be ƒ _uch =N*ƒ=N*3910 Hz.

The relative error of frequency measurement is [1] Metrology, standardization and technical measurements: (Textbook for universities / A.S. Sigov, V.I. Nefedov; Edited by A.S. Sigov. - M.: Higher School, 2008. - 624 p.; ill.):

where T _count is the counting time.

As follows from relation (5), the greater the pulse frequency and counting time, the smaller the relative frequency measurement error. We increased the counting frequency using a frequency multiplier. The counting time is limited by the time the projectile is at the stage of intermediate ballistics and is taken equal to T _count =0.1 seconds.

The initial velocity of the projectile is entered into the system for calculating the time of detonation of the projectile after firing, taking into account the entered detonation distance.

At the frequency of counting pulses ƒ _pr =3910 Hz, counting time T _count =0.1 sec. and N=10, the relative frequency measurement error will be [1]:

δƒ=±1/ƒ _pr T _sch N=1/3910*0.1*10=0.000256

or 0.000256*100=0.0256%.

This will ensure the measurement of absolute frequency with an error of Δƒ=3910*0.000256=1 Hz., and the initial speed:

In this case, the systematic error of an air blast at a distance of L=1000 m will be:

ΔL=ΔV*t=0.255*1000/1000=0.255 m,

and at a distance of L=2000 m ΔL=0.51 m. The detonation distance L is entered into the remote control unit and calculates the detonation time using laser radiation coding. Here it is assumed that the detonation distance is specified accurately.

The main technical result of the proposed invention is the possibility of creating an autonomous method in a projectile for measuring its initial speed.

New features that have significant differences in method are the following set of actions:

1. Plane polarized laser radiation is directed at the back of the moving projectile;

2. The radiation polarization plane analyzer, located at the rear of the rotating projectile, converts the plane polarized laser radiation into periodically varying radiation intensity;

3. When the projectile rotates with an angular velocity Ω, the radiation intensity after the analyzer changes according to a sinusoidal law with a double circular frequency ω=2Ω, while the frequency of the electrical signal ƒ=Ω/π;

4. The frequency of the electrical signal is converted by a frequency converter, with a conversion coefficient N>1, which allows, with limited counting time, to increase the range accuracy of air blasts.

The inventive method is the result of scientific research and experimental work.

Figure 4 shows a diagram of the experiments, where:

The projectile body 1 contains an explosive filling 2, a remote control unit 3, an optical window 5, behind which there is a radiation polarization plane analyzer 22 and a photodetector 7 connected to the remote control unit 3.

When fired, an external transmitting device, including a laser 7, connected to the gun, emits plane polarized laser radiation, which carries a code combination - information about the distance to the target.

The laser radiation, having passed through the polarization plane analyzer 5, hits the photodetector 6. When the projectile 1 rotates with angular velocity Ω, the polarization plane analyzer 5 of the radiation incident on the projectile rotates with it. The intensity of the radiation passing through the analyzer 5 and incident on the photodetector 6, in accordance with the Malus law, corresponds to formula (1).

In this case, the variable component of the signal from receiver 6 changes with double the frequency ƒ relative to the angular velocity of rotation of the projectile.

Based on the frequency of the electrical signal f, the initial velocity of the projectile is calculated:

Thus, the use of the proposed invention makes it possible to significantly simplify, reduce weight and increase the reliability of the measuring system, as well as improve its energy characteristics. The weight of the analyzer placed in the projectile is no more than two grams.

Claims (6)

1. An autonomous method for determining the initial velocity of an artillery projectile with a remote detonation in the air, including measuring the angular velocity of rotation of the projectile, calculating the initial velocity from it, characterized in that plane polarized laser radiation is directed at the projectile by a polarization analyzer installed in the rear part of the projectile, transforming it into periodically changing radiation, the frequency of which is equal to twice the angular velocity of rotation of the projectile, the variable component of the resulting radiation is converted into an electrical signal by a photodetector and its frequency is measured, and the initial velocity of the projectile is calculated from the frequency of the electrical signal: , where d is the barrel caliber, α is the angle of inclination of the barrel rifling at the muzzle section of the gun barrel, ƒ - frequency of the electrical signal. 2. An autonomous method for determining the initial velocity of an artillery shell with a remote detonation in the air, according to claim 1, characterized in that the frequency of the electrical signal is converted with a conversion factor N>1.

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