Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Method and aPParatuS for improving the accuracv of fire.
The invention relates to a method and an apparatus for improving
the accuracy of fire of real shots or projectiles from a shooting
installation, comprising a surveying means for tracking and surveying
a projectile or shot along a flight path or trajectory, a computer
for calculating the controllable parameters (shooting elements) and
an effector (gun, launcher, etc.) servocontrolled in accordance with
the controllable parameters supplied by the computer, in which the
controllable parameters are calculated by means of available target
parameters and known predetermined parameters and with the aid of
the surveying means the trajectory of a pilot shot or projectile
is surveyed and the thus determined pilot trajectory is used for
correcting the controllable parameters for the real shots.
The invention is therefore in the field of fire control and more
particularly relates to a method for improving the accuracy of fire
of unguided and driveless projectiles. The latter includes rockets
on their ballistic flight following combustion cutoff. It is assumed
that the present and future location of the target, e.g. its trajec-
tory or path of motion, is accurately known and cannot be influenced
and is described by so-called target parameters.
However, the trajectory of the shot for attacking a target is depen-
dent on numerous influences and quantities, which are referred to
here as controllable parameters (e.g. shooting elements, directional
quantities) and predetermined parameters.
The predetermined parameters are those having an influence on the
trajectory of a shot, but which cannot be changed by the method,
i.e. are not controllable. In turn, they can be placed in two clas-
ses, a first class with parameters which are independent of the firing
installation and the projectile, such as the wind, temperature, air
pressure, etc., as a function of the location, and a second class ~ :
with parameters which depend on the shooting installation and
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the projectile, such as the location and setting-up errors of the
effectors, divergences from the e~pected shearin~ force, etc.
The basic problem of fire control is consequently to so select the
controllable parameters (e.g. the direction of the gun tube from
which the projectile is fired, as well as its flight characteristics), -
in such a way that the projectile meets the target, even under the
influer.ce of the predetermined parameters. For this purpose the
predetermined parameters, e.g. the weather conditions, location and
rotation position of the gun mount must be known as well as possible. -
Conventional methods for improving the accuracy of fire of projectiles
or shots can be subdivided into two groups.
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1. The predetermined parameters are measured with conventional
methods and then taken into account when calculating the cont-
rollable parameters. For e~ample, by using a weather balloon ~;
the meteorological data are determined, such as e~g. the vect-
orial wind velocity, pressure and temperature of the air. How-
ever, these methods are usually so complicated and time-consum-
ing, that they cannot be sufficiently frequently carried out
in order to have adequate knowledge of the predetermined para-
meters which are highly dependent on the location (of the target)
and the time, e.g. the wind velocity.
2. The trajectories of the real shots sre measured, which have
already been fired at the target and correspondingly the traj-
ectories of the subsequent real shots are corrected. This so-
called CLFC (Closed Loop Fire Control) method is admittedly
insensitive to the dependence of the controllable parameters
and the predetermined parameters on the time and place, because
it is carried out at the correct place and at the correct time,
but this method presupposes a long burst of fire, whose duration -
must be long enough, compared with the flight time of the proj-
ectiles. It also requires a large number of sensors (tracking
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and surveying means) for surveying the flight paths of the target
and the projectiles, because said flight paths often differ
greatly from one another. Finally, for time reasons, it cannot
itself identify the predetermined parameters and can in fact
only correct their action on the trajectories of the projectiles. -
In other words it is also not possible to obtain information
as to the reasons for the divergence between the measured and
the expected trajectory, i.e. which predetermined parameters
have entered the calculation with values differing from the
true conditions. Therefore these corrections of the effects ~ ~-
of the predetermined parameters by corresponding effects of ~-
the controllable parameters are at least locally difficult to
transfer, because they are still dependent on the target location
if the actual predetermined parameters are not dependent thereon.-~
For example, it is not advantageous at the start of a burst
of firing to use the aforementioned corrections from the end
of the preceding burst of firing if the target is locally rapidly
moving. ~ ~-
A method of the aforementioned type and which in principle belongs ~ -
to the aforementioned second group, is known from Swiss Patent 501 ~ -
203. For firing at a known target a pilot shot or projectile is
fired with the same flight characteristics as the intended real shot
or projectile and the pilot trajectory of the pilot shot is determined
by the cooperation of the surveying means (radar) with the trajectory
computer. On the basis of the pilot trajectory determined, it is
also possible to determine in the trajectory computer the directional
errors of the effector or the deviation of the cutoff point of the
pilot trajectory compared with the preselected-target object. Such
directional errQrs result from the effect of unknown disturbance
variables, such as wind, pressure, temperature, etc., which are ref-
erred to here as predetermined parameters. This known method can
only determine the effect of all these disturbance variables on the
trajectories of pilot shots and take them into account by correcting
the trajectory of the real shot, but not said disturbance variables.
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On the basis of Swiss Patent 501 203, the problem of the present
invention is to be able to rapidly incorporate into the ~ire control
calculation those predetermined parameters (unknown disturbance vari- -
ables), which are to be incorporated into a correction of the control-
lable parameters, and still to make them available for the entire
area to be covered by the effector or effectors when there is no
specific target.
For solving this problem in a method as defined in the preamble of
claim 1, it is proposed that one or more pilot shots are fired in
the direction of possible and/or known targets and that from the
pilot trajectories the predetermined parameters are calculated and
stored and subsequently or directly incorporated into the calculation
of the controllable parameters from the target parameters of a given
target. Further appropriate procedures with respect to the method
are defined in the subclaims.
The basic idea of the inventive method is that not only should the
locally and/or time difficulty transferable effect of all the locally
and/or time adequately transferable predetermined parameters on the
trajectories of the shots or the influence of these effects on the
controllable parameters and therefore the fire control calculation
i9 determined and taken into consideration, but also the actual pre-
determined parameters. For certain applications some of these, namely
the ones which are dependent on the firing installation and the proj-
ectile, can be dealt with on a priority basis. For this purpose
the trajectories of pilot shots are surveyed and which need not neces-
sarily strike a target, but are instead shot at wherever it is sub-
sequently assumed a target could be. It is possible to use the same
surveying means which will subsequently survey the target or the
target firing. In the same way the pilot shots can be shot from
the same effector which is subsequently used for firing the real -
shots. Sufficient time is available to intensively evaluate the
measured values and on the basis of the effect of the predetermined
parameters to determine these as a cause, so that the corresponding
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corrections of the controllable parameters can in particular be better
locally transferred, in that they are dependent on the predetermined
parameters and the target location. The inventive method can be
automated and can be periodically carried out at times of high alert.
From the effect of the predetermined parameters, conclusions are
drawn regarding the predetermined parameters as a cause. This conc-
lusion is possible as a result of modern calculating and computing
processes and the extended Kalman filter is particularly suitable
for this. The movement of the projectile is described by a stoch- ~-
astic differential equation, whose vector of state e.g. contains
the position and velocity of the projectile. In the inventive method
the vector of state is broadened by the sought predetermined parame-
ters, in that the latter are no longer considered and dealt with ~-
as invariable parameters, but as variables of state. However, the
controllable psrameters are still looked upon and dealt with as invar-
iable parameters. As a result of known, e~actly defined, algebraic
transformations the algorithm of the extended Kalman filter is formed
from the stochastic differential equation of the projectile movement
and which calculates from the measured values of the trajectories
of the pilot shots estimates for all the variables of state and there-
fore the predetermined parameters. This estimate of the variables
of state is based on a stepwise improvement, which i9 based on an
initial estimate (initialization), which can e.g. result from an
earlier performance of the inventive method or a conventional measure-
ment. Further details of this will be given in connection with fig. 2.
The partial derivation of the measured values is calculated and used
in accordance with the predetermined parameters. In the case of
effector-dependent predetermined parameters, e.g. setting-up errors
and muzzle velocity, said partial derivation tends to be large close
to the effector and small remote from the effector. In the case
of effector-independent predetermined parameters, e.g. meteorological
data, it is small close to the effector and large remote from the
effector. This facilitates the differentiation of effector-dependent
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and effector-independent predetermined parameters on the basis of
a single pilot shot. In addition, such a differentiation requires
the evaluation of many pilot shots in widely differing directions
if it is to be reliable and accurate.
Particularly for firing at moving targets, i.e. with variable target
parameters, the surveying means according to the invention can survey
or track both the trajectories of the pilot shots and the path of
motion of the target. The pilot shots can also be of a different
nature to the real shots, so that the movement thereof is described
by a different differential equation and influenced in a different
way from the predetermined parameters. Thus, according to the inven-
tion different pilot shots are surveyed, which react differently
on the parameters to be determined. Thus, e.g. the pilot shots can
carry besides or in place of an explosive charge special devices,
e.g. transponders, corner reflectors, Luneberg lenses, etc., which
facilitate the surveying or tracking thereof. For this and other
reasons theg can have a different shape, different mass and even
a different calibre. They can differ at random from the real shots
and from one another, provided that their trajectories are influenced
by the same predetermined parameters. Also from this standpoint
the predetermined parameters can be better transferred than their
action on the controllable parameters or on the trajectories of the
shots. However, obviously the real shots can serve as pilot shots
and in particular preceding real shots can serve as pilot shots for
a following round.
The importance of not only determining the effect of the predeter~
mined parameters, but these predetermined parameters themselves,
can be illustrated by the following example. A pilot shot or proj-
ectile i9 fired northwards and as an effect the surveying means obser-
ves an eastward deviation. The cause can be two predetermined para~
meters, namely 1. a west wind or 2. a setting-up error with respect
to the azimuth angle position of the gun mount. A targetthen appears
in the south. Then the trajectories of the real shots must in the first
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case be corrected to the west and in the second to the east. This
example clearly shows that the pilot shots must be fired wherever
it might be necessary to fire real shots. Only in this way is it
possible to estimate or identify the parameters and differentiate
them from one another.
The example also shows that the method can differentiate between
the effect of predetermined parameters which are dependent on the
shot and gun (in the present example setting-up errors) and those
which are not dependent on the shot and gun (i.e. influence factors,
such as the west wind mentioned in the example).
The influences of different predetermined parameters are also revealed
along the trajectory in different ways. Thus, the initial mo~ement
of the projectile is firstly dependent on the influence factors,
which are linked with the shooting installation and the actual proj-
ectile, whereas e.g. an unexpectedly rapid drop following the zenith
could have meteorological causes.
For specific fields of use and firing installations it can therefore
be adequate to use a simplified modelling and from a measurement
of a specific portion of the trajectory to draw conclusions regarding
that part of the predetermined parameters mainly influencing the
same. This makes it possible to derive a simplified method variant,
which is described hereinafter.
The fundamental idea of this method variant is based on the simpli-
fying assumption that the course of the first part of the trajectory
of a projectile or shot, e.g. the first 300 to 800 m after it leaves
the tube, is approximately only dependent on the predetermined param-
eters, which are dependent on the projectile and the gun, i.e. the
estimates of said parameters can be determined solely by surveying
the first part of the trajectory. The prerequisite for this is that
the trajectory can be surveyed from the outset. It is characterized
by a saving of computing effort and permits shorter reaction times.
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This method is particularly suitable for increasing the hit capacity
of artillery tubular weapon fire control units if the existing tact-
ical sequences are not to be modified. Thus, prior to the actual
true shooting, a so-called variance shooting is carried out in which
generally one or more shots are fired by a control or guidance gun.
If the trajectories of these pilot shots are surveyed and modelled
according to the simplified inventive method, from the first part
of the trajectory is obtained ~he effective vO vector (amount, azi-
muth and elevation). Apart from wind influences which can be ignored
for the initial phase, this makes it possible to establish the sett-
ing-up errors of the control gun and the deviations of the departure
velocity amount calculated back to the muzzle compared with the exp-
ected value. These estimates avoid systematic and statistical devia-
tions of the control gun and the pilot shot being transferred to
the real shots or firing. It is also possible to establish the posi-
tion coordinates of the effector from which the projectile has come
as predetermined parameters from said first trajectory portion.
The simplified inventive method can also be extended to true shots -
or part of the latter. Two further advantages are associated there-
with. Firstly there is no need for the usual, generally inaccurate
measuring of the vO amount, e.g. via the Doppler effect, whose imprec-
ision is due to departure errors, twisting effects of the projectile,
powder after-effects, etc. and secondly the location coordinates
of the gun relative to the trajectory surveying means can be checked
and corresponding corrections can be derived therefrom.
Compared with the known methsd, the presently described variant of
the inventive method solves the problem that there is no longer any
error transfer from the control gun to the remaining guns, because
each vO deviation introduced by the control gun is transferred to ;
the remaining guns and therefore to all the true shots, e.g. a too
large amount of the initial velocity of the pilot shot gives a too
wide impact in the target area. According to the method used up
to now, i.e. using human or electronic observers in the target area,
this deviation is e.g. attributed to the effect of meteorological
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influences and the departure elements of all the guns for true shoot-
ing are therefore elevation-corrected by a corresponding compensation
value. However, as apart from the control gun, the other guns do
not have the too large initial velocity amount, the following true
shooting will have too short hit positions. However, if with the
simplified inventive method the vO vector of the pilot projectile
is calculated, then its influence is eliminated from the calculation
of the predetermined parameters relevant for the correc'ion of the
departure values and the hit position of the true shooting will not
suffer from this error. If the pilot shooting reveals that there
is a setting-up error, there are two sensible assumptions for taking
it into account. If it is to be assumed that the setting-up error
only relates to the control gun, it can be deducted from the directi-
onal values of the remaining guns in the battery, which are controll-
able parameters calculated on the basis of the pilot firing. ~Iowever,
if it is to be assumed that all the guns have the same setting-up
error, it can be taken into account when calculating the directional
values of all the guns.
If the simplified method is also used for true shooting and if a
trajectory surveying means is available which is able to survey the
shots of all the guns in the initial phase of the trajectory, it
is also possible to determine the individual setting-up errors and
departure velocities of the shots.
For performing the inventive method a shooting installation is requi-
red which has at least the following, per se known components: at
least one sensor as the surveying and tracking means, e.g. radar,
laser, t.v. or Flir, with an at least biaxial sensor servo, which
can give a random direction to the parallel lines of sight of the
sensors combined into a common line of sight and keep same directed
permanently on the target or projectile to be measured; at least
one effector, e.g. gun or rocket launcher with in each case at least
one biaxial effector servo, which adjusts the controllable parameters,
such as e.g. the departure direction of the projectile; at least one
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preferably digital computer, which estimates the predetermined para-
meters as variables of state and controls the sensor servo and effec-
tor servo; as well as data channels, which link the sensors with
the computer or computers and effectors, together with at least one
type of pilot projectiles.
An example for realizing the shooting installation appropriate for
the inventive method and a block circuit diagram of the latter are
shown by the two following drawings.
Fig. 1 diagrammatically shows a side view of a firing installation.
Fig. 2 is a fire control system for a shooting installation accor-
ding to fig. 1 in the form of a block circuit diagram. ~
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Fig. 1 in diagrammatic side view shows as a use example of the inven-
tive method a firing installation 100, which comprises a surveying
means 20 and a weapon system (effector) 10, from which a shot or
projectile 15 can be fired on a trajectory or flight path 1. The
surveying means 20 constructed as a stationary or mobile, automotive
unit is provided e.g. with a radar, laser, IR or TV tracking unit
21 as a sensor and by means of this individual or several time-succ-
eeding fired shots 15 can be surveyed over a given period of time
and sighted over a given local area with a beam S or beams Sl n.
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The weapon system 10, which is also constructed as a stationary or
mobile, automotive unit and which can also be constructionally comb-
ined with the surveying means containing the fire control computer, ~ -
has a weapon tube 11, which is adjustable for attacking targets with
the aid of not shown means with respect to the controllable para- -
meters, such as the directional quantities azimuth and elevation. -
Fig. 2 shows in block circuit diagram form the principle of the above-
described firing installation 100, in which 22 is a command post,
35 a firing control computer unit, 10 the weapon system and 15 or
l51_n the fired shots, 20 the surveying means and 25 a computer with
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memory. The data channels between the blocks carry the following
informations:
information on the available fixed or variable target parameters;
43 controllable parameters such as firin8 elements and directional
quantities;
47 measured trajectory parameters of the pilot shots Sl n;
48 calculated, predetermined parameters.
According to fig. 1 the trajectories 11 n between the weapon system
and the shots 151 n and the test beams Sl n between the shots
151_n and the surveying means are also shown in fig. 2.
The functional sequence of the inventive method can be gathered in
the following way from the block circuit diagram of fi8. 2. From
the command post 22 via data channel 40 data of the target parameters
are supplied to the firing control computer unit 35 and the latter
supplies the calculated controllable parameters via data channel
43 to the weapon system 10. The trajectories 11 n of the projectiles
or shots 151 n fired by the weapon system 10 are surveyed or tracked
by the surveying or tracking means 20 and the trajectory data are
supplied via data channel 47 to computer 25. The latter calculates
and optionally intermediately stores the predetermined parameters,
which are supplied via data channel 48 to the firing control computer
unit 35. The latter takes account of the predetermined parameters
when calculating the controllable parameters, which are supplied
to the weapon system 10 via the data channel 43, in order to be able
to fire real shots or projectiles with the corresponding weapon sett-
ing. In a special method variant an estimate of the vO vector is
calculated from the survey of the first trajectory portion and its
amount and direction varies from the theoretically e~pected vO vector.
By taking into account this result enabling direct conclusions to
be drawn on the departure error, it is ensured that systematic and
statistical deviations of the control gun and the pilot or initial
shot are not transferred to the following true shots.
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If in a possible embodiment of the inventive method, particularly
for firing at moving targets, both the trajectories of the pilot
shots and the path of motion of the target are surveyed by the same
surveying means 20, then the firing control computer unit 35 can
be constructionally combined with the computer 25, which obviates
the inputting of target parameters via data channel 40.
