RU2351947C2 - Method of measuring initial shell velocity - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: number of groups of values of return to possible quantities of current velocity is shaped on the registered group of periods of time intervals with general beginning in the Doppler echosignal where every subsequent is less than previous, and on a number of groups of prospective trajectories with the general beginning; it is determined that group of the number where odds between each previous and the subsequent values of the return to possible quantities of current velocity is underload, and odds between the first and second values is positive, and initial velocity is calculated on remoteness and extent of trajectories corresponding to them in this group on these two values.

EFFECT: increase of measurement accuracy of shell velocity by means of measuring current velocity on small distances from trunk.

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Description

The present invention relates to radar monitoring of trajectories of ballistic objects and can be used to measure the initial velocity of the projectile.

It is known that when measuring the initial velocity of a projectile, Doppler radars are widely used to observe them on the trajectory, and the obtained data for determining the velocity refer to parts of the trajectory located at a certain distance from the cut of the barrel.

A known method for measuring speed is the US patent "Method for measuring speed by Doppler radar", in which the initial speed is determined by a group of equally spaced time sections in the Doppler echo signal, and the duration of the time sections is selected automatically by recording the number of pulses of the first time section of the Doppler signal [1] . The calculation of the initial velocity does not take into account the delay in the appearance of the Doppler signal after the projectile leaves the barrel and the difference between the current velocity of the projectile and the radial velocity, which is caused by a shift in the radar position relative to the axis of motion of the projectile. This limits the accuracy of the applied method for determining the speed of high-speed objects at short range.

The difference between the radial speed and the initial speed of the object is taken into account in another known device - the US patent "Speed Chronograph", which is rigidly attached to the barrel and the time section in the Doppler echo is tied to a known section of the object’s trajectory, which is determined using the angular resolution of the radar [ 2]. Detection of the object in this area is carried out by the amplitude method, which requires high stability of the energy characteristics of the radar and the reflectivity of the object.

Also known is a device and method for measuring the initial velocity of the projectile - the patent of the Russian Federation "Method for measuring the initial velocity of the projectile and a device for its implementation" [3]. The device contains a Doppler radar, a recorder for the duration of temporary sections of a Doppler signal, a multiplier, a photosensor for projectile exit from the barrel, a temporary pulse generator, a counter for temporary sections, a buffer memory, a comparator, a meter for the total duration of temporary sections and an adder.

The method consists in the fact that a sequence of current speeds is formed in a group of durations of successive time sections in the Doppler echo of the projectile. In the generated sequence, the reliability of each value of the current velocity of the projectile is determined. The reliability of the current velocity values is checked to ensure the required measurement accuracy, which does not allow the use of this method at small distances, where the methodological error increases due to the fact that the Doppler shift is caused by the radial component of the velocity of the moving projectile.

The initial speed V ₀ and the current speed V are interconnected by the following relation

where β is the velocity regression coefficient, and (xx ₀ ) is the removal of the projectile from the barrel. Then the relative error in the measurement of the initial velocity can be expressed as

where σ _β is the absolute error in determining the velocity regression coefficient, σ _x is the absolute error in determining the distance from the barrel, σV ₀ is the absolute error in determining the initial velocity, and σV is the absolute error in the current speed.

An analysis of the last two terms in expression (2) revealed that their contribution to the error in measuring the initial velocity decreases with decreasing projectile removal, where the current velocity is measured.

The relative error in measuring the current speed σV / V depends on many factors and in the general case is the sum of the relative error in determining the duration of the time section T, the relative error in determining the distance traveled D and the methodological error δV _met . The relative error in measuring the current speed can be represented as follows:

where σ _D is the error of the distance traveled, σ _T is the error of measuring the duration of the temporary section.

An analysis of expression (3) shows that in order to increase the accuracy of measuring the current speed, it is necessary to increase the duration of the time section T and the length of the distance traveled D. Also, the methodological error δV _met , the error of measuring the duration of the time section σ _t and the error value of the distance traveled σ _D should be reduced. These errors are reduced by decreasing removal to a moving projectile.

The aim of this invention is to increase the accuracy of determining the initial velocity of the projectile by measuring the current speed at small distances from the barrel.

This goal is achieved due to the fact that in the method of measuring the initial velocity of the projectile by the position of the trajectory recorded by the group of durations of temporary sections with a common beginning in the Doppler echo, where each subsequent is less than the previous one, and a number of groups are formed for a number of groups of proposed paths with a common beginning values inverse to the possible values of the current velocity, determine the group of the series where the difference between each previous and subsequent values inverse to the possible values of the current velocity of the projectile is minimal nn, and the difference between the first and second values is positive, and the initial velocity is calculated from them by the distance and length of the corresponding paths of this group.

A device for measuring the initial velocity of a projectile is proposed, comprising a Doppler radar, a time pulse generator, a comparator, an adder, (N + 1) time-domain recorders, (N + 2) multipliers, (N + 1) subtractors, a bank of a number of prospective reverse groups values of the path and distance, the first output of the Doppler radar connected to the first inputs (N + 1) of the registrars of the duration of the time section, to the second inputs of which through the generator of time pulses connected the second output Doppler radar, the outputs of the (N + 1) time-domain recorders are connected respectively to the first inputs of the first (N + 1) multipliers, the first inputs of the first N subtractors are connected respectively to the outputs of the first N multipliers, each other input of N subtractors is connected to the output of each subsequent multiplier, the output of the (N + 2) -th multiplier is connected to the first input of the (N + 1) -th subtractor, the outputs of the first N subtractors are connected to the N inputs of the adder, and its output is connected to the first input of the downing device, one output of which is connected to the bank input of a number of prospective groups of inverse values of path and distance, and each of (N + 1) outputs is connected respectively to the second input of the first (N + 1) multipliers, the output of the first subtracting device is additionally connected to the second input of the comparator, the second output of which is connected to the first input of the (N + 2) -th multiplier, and its second input is connected to the (N + 2) -th output of the bank of a number of proposed groups of inverse values of path and distance, the output of the first multiplier is additional It is connected to another input of the (N + 1) -th subtractive device.

A new set of features allows you to fix the belonging of the group of durations of temporary sections during the movement of the projectile immediately after departure to certain intervals of the path and their distance from the barrel, which increases the accuracy of measuring the initial velocity of the projectile.

In addition, the proposed set of features does not require high stability of the radar energy characteristics and reflectivity of the object, and also makes it unnecessary to use sensors that determine the moment the projectile leaves the barrel, which expands the possibilities of using the proposed method where installation of these sensors is not possible or was not provided .

Figure 1 shows the structural diagram of the proposed device for measuring the initial velocity of the projectile,

where 1 is the Doppler radar;

2 - a generator of temporary pulses;

3 - the registrar of the duration of the first time section;

4 - the registrar of the duration of the second time section;

5 - the registrar of the duration of the third time section;

6 - the registrar of the duration of the (N + 1) -th time section;

7 - the first multiplier;

8 - the second multiplier;

9 - the third multiplier;

10- (N + 1) -th multiplier;

11 - (N + 2) -th multiplier;

12 - the first subtractive device;

13 - the second subtractive device;

14 - N-e subtractor;

15 - (N + 1) -e subtractor;

16 - adder;

17 is a comparison device;

18 is a bank of a number of proposed groups of inverse values of path and distance.

Figure 2 shows a diagram of the relative position of the Doppler radar, barrel and projectile on the trajectory.

Figure 3 shows a graph of the dependencies of values inverse to the values of possible current speeds, from the range.

Figure 4 shows the dependence of the reciprocal of the current speed on the distance from the trunk.

The essence of measuring the initial velocity of the projectile by the proposed method is as follows.

(при m=М) производится начало регистрации группы длительностей временных участков t_i=Т_i+α_i, где i=1, 2, …, N+1, T_i - детерминированная длительность временного участка, α_i - случайная составляющая. Окончание регистрации временных участков фиксируется моментом, при котором происходит изменение радиального расстояния на величину

. Предполагаемые пути D_i,m, которые проходит снаряд в соответствии с обозначениями на фиг.2, выражаются какAt one of the possible ranges

(at m = M), the beginning of the registration of the group of durations of temporary sections t _i = Т _i + α _i , where i = 1, 2, ..., N + 1, T _i is the determined duration of the temporary section, α _i is a random component, is started. The end of registration of temporary sections is fixed by the moment at which the radial distance changes by

. The estimated paths D _{i, m} that the projectile passes in accordance with the notation in FIG. 2 are expressed as

m = L, L + 1, ..., L + J.

The inverse values of the possible current speed on these putative paths are determined respectively

From relation (1), the determined durations of the group of temporary sections over which the projectile travels a distance from x _m to x _m + D _{i, m} are

Given the smallness of βD _{i, M} << 1, we have the following group of equalities:

or

where ε _i is a small positive value depending on the regression coefficient of velocity β.

In the absence of noise, graphs of the dependencies of values inverse to the values of possible current speeds for a group of two time sections from the distance of the proposed paths are shown in Fig.3. It can be seen that the dependences intersect only in one range region R _m , and the values of possible current velocities in accordance with (7) are equal to the current velocity of the projectile V.

To obtain the value of the current speed with a large signal-to-noise ratio, it is enough to have only two members in the group. However, in the presence of noise due to fluctuations in the reflected signal and multipath propagation of electromagnetic energy from m rows of N + 1 groups of possible values of current speeds, there is one group in which the differences are minimal, and the possible value of the current speed, which corresponds to the maximum duration of the time section, is closest to the value of the current velocity of the projectile.

The value of the initial velocity V ₀ is determined from (7), taking into account the distance between the centers of the first D _{1, m} and second D _{2, m} paths and their distance (x _m -x ₀ ) from the trunk. From consideration of figure 4, the regression coefficient β is determined as

Taking into account (8) and β (x _m + D _{1, m} -x ₀ ) << 1 from (1), the reciprocal of the initial velocity is calculated as

Thus, by applying the proposed assessment of the current velocity of the projectile and determining the distance to their respective paths, it is possible to measure the initial velocity of the projectile at small distances from the barrel and, accordingly, the accuracy of measuring the initial velocity of the projectile is increased.

A device is described that implements the proposed method for measuring the initial velocity of the projectile.

The operation of the proposed device is as follows.

At a certain distance from the barrel after the projectile leaves the gun barrel, the amplitude of the Doppler signal increases to a threshold level at which the Doppler radar detector 1 is triggered and triggers a temporary pulse generator 2 through the second output. From the output of the temporary pulse generator 2, they begin to arrive at the second inputs N + 1 registrars of duration of temporary sections 3, 4, 5, 6, at the first inputs of which Doppler pulses come from the first output of the Doppler radar 1. Registrars of duration of time Variable sections 3, 4, 5, 6 consider the number of time pulses from the time pulse generator 2 for a fixed number K _i , Doppler pulses, and each following is less than the previous one. The data determined by expression (4) for m = L + J from the bank of a number of prospective groups of return values of path 18 comes from its N + 1 outputs to the second inputs of the corresponding (N + 1) multipliers 7, 8, 9, 10. According to the data from the outputs of the registrars of the durations of temporary sections 3, 4, 5, 6, respectively, using the multipliers 7, 8, 9, 10 according to dependence (5), a group of N + 1 values is calculated that is the reciprocal of the values of the possible current speed. The data obtained from the first N multipliers 7, 8, 9 are fed to the first inputs of N subtractors 12, 13, 14, the other inputs of which receive values that are inverse to the values of the possible current speed, respectively, from each subsequent multiplier 8, 9, 10. From the outputs N subtracting devices 12, 13, 14, the received data is fed to the N inputs of the adder 16, and the summing result is fed to the first input of the comparing device 17, the second input of which receives data from the first subtracting device 12. Then the data defined by expression (4) for m = L + J-1 of the bank of a number of prospective groups of inverse values of the path and distance 18 come from its N + 1 outputs to the second inputs of the corresponding N + 1 multipliers 7, 8, 9, 10, and the comparator 17 repeats the process of forming a group of values that are inverse to the possible current speeds, until the sign of the result from adder 16 changes, with m = M, and at the output of the first multiplier 7, the data will be close to the reciprocal of the current velocity of the projectile V. In this case, the difference between the values of the reciprocal of the possible current velocities from the first subtractor about the device 12, coming through the second input of the comparing device 17 to the first input of the multiplier 11, must be positive. At the other input of the multiplier 17 comes from the (N + 2) -th output of the bank of a number of proposed groups of inverse values of the path and distance 18 the value of the first factor of expression (9). Thus, from the output of the (N + 1) -th subtracting device 15 according to the incoming results to its inputs from the first multiplier 7 and the multiplier 11, we have a value inverse to the value of the initial velocity of the projectile.

In the proposed structure of the device, another procedure can also be used to search for the minimum difference in the group of rows inverse to the values of the possible current velocity of the projectile.

Technical implementation of the proposed device is possible using discrete digital elements and computer equipment.

According to the proposed method and device, a prototype of a measuring instrument for the initial velocity of the projectile was made. Simulation, as well as full-scale testing of the layout, confirmed the possibility of a method for measuring the initial velocity of shells when tracking the projectile at angles to the trajectory, when the difference between the radial velocity and the current velocity of the projectile significantly exceeds the required measurement accuracy, which allows measuring the initial velocity of each shell in a queue from guns with a high rate of fire .

Information sources

1. US patent No. 3918061, NKI 343/8 from 04.11.75,

2. US patent No. 4030097, NKI 343/8 from 06/14/77

3. Patent of the Russian Federation No. 2250476, MKI G01S 13/58 from 09/30/2002 - the prototype.

Claims (1)

A method for measuring the initial velocity of a projectile by the position of the path of its departure from the gun’s barrel, including recording a group of durations of temporary sections of Doppler pulses with a common beginning in the Doppler echo signal and calculating the initial velocity of the projectile based on the distance from the projectile’s barrel, characterized in that a group of recorded durations of temporary sections, where each subsequent section is less than the previous one, and for a number of groups of estimated paths that the projectile passes, with a common beginning of these They form a series of groups of values that are inverse to the possible values of the current velocity, determine the group of the series where the difference between each previous and subsequent values that are inverse to the possible values of the current velocity of the projectile is minimal and the difference between the first and second values is positive, and the initial velocity of the projectile is calculated from them taking into account its remoteness from the gun’s barrel and the length corresponding to the calculated speed of the paths of this group.

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