US3609883A

US3609883A - System for simulating the firing of a weapon at a target

Info

Publication number: US3609883A
Application number: US887516A
Authority: US
Inventors: Rune Torsten Isidor Erhard
Original assignee: Bofors AB
Current assignee: Saab Bofors AB
Priority date: 1969-12-23
Filing date: 1969-12-23
Publication date: 1971-10-05
Anticipated expiration: 1988-10-05

Abstract

THE INVENTION CONCERNS A SYSTEM FOR SIMULATING THE FIRING OF A WEAPON, IN PARTICULAR A WEAPON MOUNTED ON A MOVABLE WEAPON CARRIER, AT A TARGET, PARTICULARLY A MOVING TARGET THE SIMULATOR SYSTEM INCLUDES A RADIATION TRANSMITTER FOR EMITTING A NARROW BEAM OF OPTICAL RADIATION, WHICH IS MOUNTED ON OR COUPLED TO THE WEAPON SO AS TO FOLLOW THE AIMING MOVEMENTS OF THE WEAPON IN AZIMUTH AND ELEVATION. THE TRANSMITTER COMPRISES A MIRROR OR SOME SIMILAR OPTICAL MEMBER DETERMINING THE EMISSION DIRECTION OF THE TRANSMITTER AND THIS MIRROR IS ROTATABLE SO THAT THE EMISSION DIRECT CAN BE MOVED IN AZIMUTH AS WELL AS IN ELEVATION BY CORRESPONDING ROTATION OF THE MIRROR. BEFORE THE INSTANT WHEN THE FIRING OF A PROJECTILE WITH THE WEAPON AT THE TARGET IS SIMULATED, THE MIRROR IS LOCKED IN A PREDETERMINED POSITION SUCH THAT THE EMISSION DIRECTION OF THE TRANSMITTER IS PARALLEL TO THE DIRECTION OF FIRE OF THE WEAPON. AT THE INSTANT OF A SIMULATED FIRING OF A PROJECTILE THIS LOCKING IS RELEASED AND THE MIRROR BECOMES GYROSTABILIZED SO AS TO BE INDEPENDENT OF ANY SUBSEQUENT MOVEMENTS OF THE WEAPON. IN ITS GYRO-STABILIZED UNLOCKED STATE THE MIRROR IS ALSO COUPLED TO A SERVOMOTOR FOR ROTATION OF THE MEMBER IN A DIRECTION CAUSING A CHANGE OF THE EMISSION DIRECTION OF THE TRANSMITTER IN ELEVATION. A COMPUTER UNIT IN THE SYSTEM COMPUTES THE PROPER GRAVITY CORRECTION ANGLE OR SUPERELEVATION ANGLE OF THE WEAPON FOR THE FIRING OF A REAL PROJECTILE AT THE TARGET AND PRODUCES A SIGNAL PROPORTIONAL TO THIS COMPUTED GRAVITY CORRECTION ANGLE. THIS SIGNAL IS SUPPLIED TO SAID SERVOMOTOR SO THAT THE GYROSTABILIZED EMISSION DIRECTION OF THE RADIATION TRAMSMITTER IS LOWERED IN ELEVATION THROUGH AN ANGLE EQUAL TO THE COMPUTED GRAVITY CORRECTION ANGLE. THE COMPUTER UNIT COMPUTES ALSO THE TIME OF FLIGHT TO THE TARGET FOR A REAL PROJECTILE AND AFTER A TIME INTERVAL EQUAL TO SAID COMPUTED TIME OF FLIGT AFTER THE INSTANT OF THE SIMULATED FIRING OF A PROJECTILE THE COMPUTER UNIT ACTIVATES THE RADIATION TRANSMITTER TO EMIT A SHORT PULSE OF RADIATION. ON THE TARGET RADIATION SENSITIVE RECIEVING MEANS ARE PROVIDED FOR DETECING ANY RADIATION PULSES RECEIVED AT THE TARGET FROM THE RADIATION TRANSMITTER ON THE WEAPON.

Description

R. T. l. ERHARD Oct. 5, 1971 SYSTEM FOR SIMULATING THE FIRING OF A WEAPON AT A TARGET 2 Sheets-Sheet 1 Filed Dec. 23, 1969 RUNE TORSTEN lS/DOR ER/MRD Oct. 5, 1971 R. T. l. ERHARD SYSTEM FOR SIMULATING THE FIRING OF A WEAPON AT A TARGET 2 Sheets-Sheet 2 Filed Dec. 23, 1969 HY C A T TDRNE 15 United States Patent US. Cl. 35-25 1 Claim ABSTRACT OF THE DISCLOSURE The invention concerns a system for simulating the firing of a weapon, in particular a weapon mounted on a movable Weapon carrier, at a target, particularly a moving target The simulator system includes a radiation transmitter for emitting a narrow beam of optical radiation, which is mounted on or coupled to the Weapon so as to follow the aiming movements of the weapon in azimuth and elevation. The transmitter comprises a mirror or some similar optical member determining the emission direc tion of the transmitter and this mirror is rotatable so that the emission direction can be moved in azimuth as well as in elevation by corresponding rotation of the mirror. Before the instant when the firing of a projectile with the weapon at the target is simulated, the mirror is locked in a predetermined position such that the emission direction of the transmitter is parallel to the direction of fire of the weapon. At the instant of a simulated firing of a projectile this locking is released and the mirror becomes gyrostabilized so as to be independent of any subsequent movements of the weapon. In its gyro-stabilized unlocked state the mirror is also coupled to a servomotor for rotation of the member in a direction causing a change of the emission direction of the transmitter in elevation. A computer unit in the system computes the proper gravity correction angle or superelevation angle of the weapon for the firing of a real projectile at the target and produces a signal proportional to this computed gravity correction angle. This signal is supplied to said servomotor so that the gyrostabilized emission direction of the radiation transmitter is lowered in elevation through an angle equal to the computed gravity correction angle. The computer unit computes also the time of flight to the target for a real projectile and after a time interval equal to said computed time of flight after the instant of the simulated firing of a projectile the computer unit activates the radiation transmitter to emit a short pulse of radiation. On the target radiation sensitive receiving means are provided for detecting any radiation pulses received at the target from the radiation transmitter on the weapon.

In order that military combat practices may be carried out in a realistic manner without risks for the personnel and the equipment taking part in the practice there is a great need of a system for simulating the firing of a weapon, such as a gun or a missile launcher, which is positioned in the terrain or mounted on a movable weapon carrier, at a target, in particular moving targets, such as tanks, other vehicles, landing crafts etc. Especially there is a need of a system for simulating combat between tanks. In order to make it possible to carry out combat field practices in a manner as realistic as possible such a simulator system must be so designed that it does not prevent the target and the weapon with its crew acting in a manner that would be natural and necessary in genuine combat. Further it must be designed to indicate immediately, whether a simulated projectile fired by the weapon would have hit the intended target in the real case. Further, the simulator system must give evidence not only to the skill and precision of the crew of the weapon but also of the ice accuracy and the reliability of those directing and aiming means that the weapon may be provided with, such as sighting instruments, lead angle computers, control servos for the laying of the weapon etc.

For simulator systems for the purpose mentioned above it has been suggested in the prior art to replace or simulate a real projectile fired by the Weapon with a pulse of radiation Within the optical wave length range, for instance from a laser, which is emitted from the weapon in a direction dependent on the direction of the weapon and which if hitting the intended target actuates a radiation sensitive receiver device mounted on the target which indicates in some suitable manner that it has received a radiation pulse emitted from the weapon. Simulator systems based on this principle are described for instance in the US. patent specifications 3,143,811 and 3,243,896. Prior art simulator systems of this general type do not, however, permit a really realistic combat practice in the field and especially not practices with moving targets and weapons mounted on moving weapon carriers, as for instance tank combat practices. The reason for these deficiencies in the prior art systems is primarily that in these systems due consideration is not taken to the facts that an optical radiation pulse has a straight path of propagation whereas a real projectile has a curved trajectory and that the propagation time for an optical radiation pulse from the weapon to the intended target is negligible as compared with the time of flight of a real projectile. Moreover, it has not been taken into account that in genuine combat and in particular at a weapon mounted on a movable weapon carrier one wishes generally to change the direction of the weapon and often also the position of the weapon as soon as a projectile has been fired.

The object of the present invention is therefore to provide an improved system for simulating the firing at a target, in particular a movable target, with a weapon which can be laid in azimuth and elevation, in particular a weapon mounted on movable weapon carrier, which system comprises a radiation transmitter for emitting a narrow beam of optical radiation mounted on or coupled to the weapon so as to follow the aiming of the weapon in azimuth and elevation, means for activating said radiation transmitter to emit a short pulse of radiation a predetermined time interval after a manually initiated signal simulating the firing of a projectile with the weapon, and a radiation sensitive receiver device mounted on the target for indicating radiation pulses that may be recaived at the target. The expression optical radiation is in the present connection intended to encompass radiation within the infrared, visible and ultraviolet wavelength ranges.

Characteristic for the simulator system according to the invention is that the radiation transmitter includes a member for determining the direction of emission of the transmitter, which member is rotatable for moving said direction of emission in azimuth as well as in elevation and may be locked in a predetermined attitude relative to the weapon such that the direction of emission of the transmitter is parallel to the direction of fire of the weapon and in its unlocked state is gyrostabilized and coupled to a servo-motor for rotation of the member in a direction causing movement in elevation of the direction of emission in accordance with a control signal supplied to said servomotor, and that computing means are provided for computing the time of flight of a real projectile fired by the weapon at the target and the proper gravity correction or superelevation angle for the weapon when firing at the target and for producing a signal proportional to said superelevation angle, said computer being adapted in response to the manually initiated signal simulating the firing of a projectile to release the locking of said member determining the direction of emission of the radiation transmitter and to apply the signal proportional to the computed superelevation angle as a control signal to said servomotor'and toactivate' said radiation transmitter after a time interval equal to the computed time of flight of a real projectile.

As in the simulator system according to the invention the radiation transmitter is mounted on or coupled to the weapon so as to follow the aiming of the weapon in azimuth and elevation and the gyro-stabilized member in the radiation transmitter determining the direction of emission of the transmitter in azimuth as well as elevation is normally locked in such a position relative the weapon that the direction of emission of the transmitter is parallel to the direction of fire of the Weapon, the direction of emission of the transmitter will coincide with the direction of fire of the weapon at the instant when the firing of a projectile is simulated, for instance in that the firing button of the weapon is depressed. Therefore, the emission direction of the radiation transmitter will suffer from exactly the same errors as the direction of the Weapon, whether these errors are caused by errors of the crew when aiming the weapon, errors in the superelevation angle and lead angle estimated by the crew or partially or entirely computed by a fire control device belonging to the weapon, or by inaccuracies in the sighting and aiming means of the weapon. As at the instant of the simulated firing of a projectile the locking between the weapon and the member determining the emission direction of the radiation transmitter is released and said member is thereafter gyrost'abilized, the emission direction of the transmitter will not be affected by any movements of the Weapon in azimuth or elevation subsequent to the instant of the simulated firing of a projectile. As furthermore the computer included in the system computes the proper superelevation angle for firing a real projectile at the target and by means of the servomotor coupled to the gyro-stabilized member determining the emission direction reduces the elevation of said emission direction of the transmitter exactly through said computed superelevation angle and also computes the correct time of flight to the target for a real projectile and activates the transmitter to emit a radiation pulse no until after said time of flight, the emitted radiation pulse will hit the target and activate the radiation sensitive receiver device on the target only under the provision that the weapon was aimed correctly at the instant for the simulated firing of a projectile. If on the contrary the aiming of the weapon was incorrect at said instant or if the target has moved during the computed time of flight of a real projectile in some other way (with a difierent speed or in a different direction) than presumed by the weapon crew or the fire control computer, the emitted radiation pulse will not hit the target and thus not actuate the radiation sensitive receiver on the target.

In the following the invention will be further described with reference to the accompanying drawing, in which FIG. 1 illustrates schematically the basic principle of the simulator system according to the invention;

FIG. 2 is a simplified perspective view of an embodiment of a radiation transmitter shown only by way of example, which can be used in a simulator system according to the invention; and

FIG. 3 shows only by way of example a block diagram for an embodiment of the computer, which may be used in a simulator system according to the invention for cooperation with the radiation transmitter shown in FIG. -2.

FIG. 1 shows schematically a tank 1 provided with a simulator system according to the invention for simulating the firing of the gun of the tank 1 at a moving target 2 consisting of another tank. It is assumed that the target 2 moves in the direction 3 with a certain speed. The crew in the tank 1 acts exactly in the same Way that they would do in genuine combat, that is they observe the target 2 by means of the sighting instrument in the tank and estimate or compute by means of the fire control aids, such as range meter, lead angle computer and similar devices, that may be provided in the tank, the direction that the gun barrel 4 of the tank shall have in order to hit the target 2 with a real projectile. Assume for instance that it is estimated or computed that at a certain instant the barrel 4 should be aimed at the point 6 in order that a projectile tired at said instant shall hit the target 2. The direction to this aiming point 6 deviates from the direction to the target 2 at the instant of firing, firstly by the lead angle which is dependent on the speed and the direction of movement of the target 2', the range to the target and the time of flight of a real projectile to the target, and secondly by a superelevation angle or gravity correction angle which depends on the curved trajectory of the real projectile. If the position of the aiming point 6 has been estimated or computed correctly and the gun barrel 4- of the tank 1 is aimed properly at the aiming point 6, a real fired projectile would due to the movement of the target 2 during the time of flight of the projectile and to the curved trajectory 7 of the projectile hit the target 2 in the point of impact 8. If on the contrary there exists some error in the computation or estimation of the position of the aiming point '6 or in the aiming of the barrel 4 at the aiming point at the instant of firing, a real fired projectile would not hit the target 2.

For simulating a real fired projectile the system according to the invention includes an optical radiation transmitter 9 so mounted on the tank 1 that it participates in or follows the movements of the gun barrel 4 in azimuth as well as elevation. As in the illustrated example of the invention the tank 1 is assumed to be of the type in which the gun barrel 4 is fixed in the tank body and consequently is aimed by movements of the entire tank body, the radiation transmitter 9 is mounted directly upon the upper surface of the tank body. If instead the tank were provided with a rotatable gun turret with the gun barrel mounted for elevation therein, the radiation transmitter 9 would instead be mounted on a part of the gun which is aimed in azimuth as well as in elevation or coupled to such a part of the gun so as to follow the aiming movements of the barrel. The radiation transmitter 9 includes a member determining the direction of emission of the radiation, which member is movable or adjustable for variation of the emission direction in azimuth as well as elevation. During the aiming of the barrel 4 at the estimated or computed aiming point 6, however, said member in the radiation transmitter 9 is locked in such a position that the emission direction 10 of the transmitter is parallel to the direction 5 of. the barrel 4. Thus, also the emission direction 10 of the radiation transmitter 9 will be aimed at the estimated or computed aiming point 6. At the instant of firing, that is when the tank crew indi cates or simulates the firing of a projectile at the target 2, for instance by depressing the firing button of the gun, the locking of the member in the transmitter 9 determining the emission direction is released and as this member is gyro-stabilized in its unlocked state, the emission direction 10 will not after the firing instant be affected if the direction of the barrel 4 should be changed in azimuth and/or elevation, for instance while the tank crew aims the gun in a new direction for firing a new projectile at the same or another target. On the other hand, however, the member in the transmitter 9 determining the emission direction 10 of the transmitter is controlled from a computer unit 11 in such way that the emission direction 10 is lowered in elevation through an angle corresponding to the correct supereievation angle or gravity correction angle for the firing at the target 2, which angle has been computed by the computer unit 11. After a time interval after the simulated firing instant equal to the correct time of flight to the target 2 for a real projectile, which time of flight is also computed by the computing unit '11, the computer unit 11 activates the transmitter 9 to emit a short pulse of radiation. It is appreciated that this radiation pulse will hit the target 2 in the point 8, if the crew in the tank 1 or the fire control system in the tank has estimated or computed resp. the position of the aiming point 6 correctly and the barrel 4 was aimed properly at said point at the instant of the simulated firing. In any other case the emitted radiation pulse will obviously not hit the target 2. The target is provided with a radiation sensitive receiving device, for instance comprising one or several radiation sensitive elements 12, such as photodetectors, mounted on the target 2 so as to be activated by radiation from the transmitter 9 incident upon the vul nerable portions of the target 2. This receiver device indicates, for instance by means of light, sound or smoke signals, that it has received a radiation pulse emitted by the transmitter 9.

For a realistic simulation of a duel between two tanks 1 and 2 an additional simulator system according to the invention is obviously necessary, which has its transmitter and its computer unit mounted on the tank 2 and its radiation sensitive receiver device mounted on the tank 1.

As mentioned in the foregoing, the computer unit in the simulator system has to compute firstly the correct superelevation angle for firing at the target and secondly the time of flight to the target for a real projectile. Using the symbols:

V =the muzzle velocity of the projectile =the mean velocity of the projectile D:the range to the target t =the time of flight of the projectile U the superelevation or gravity correction angle,

one has obviously tf=D/V As known to those skilled in the art the mean velocity of the projectile can be expressed by the series V =V c D+c D -}-c D (2) For most types of ammunitions a suflicient accuracy is achieved with the three first terms in this series and for projectile velocities well above twice the speed of sound the first two terms are sufficient.

As also known in the art the superelevation angle may be approximated with sufficient accuracy by the series in which generally one or two terms are sufiicient for good accuracy. In the expressions (2) and (3) the quantities c c 0 etc. and k k k etc. are constants.

For a correct computation of the superelevation angle U and the time of flight t the computer unit needs obviously information about the actual range D to the target. This information can be supplied to the computer in several different ways. In a simple embodiment of the invention the information about the range to the target may be supplied to the computer from the training supervisors that are generally always present at field practices, for instance from a supervisor who sits on the tank and has a suitable range meter. In this case the range value can be fed into the computer of the simulator system manually by said supervisor. Alternatively, correct range values can be supplied to the computer over a remote data transfer link. In a more sophisticated system according to the invention the system itself may be provided with its own range meter, as for instance a radar range meter, a laser range meter or some other type of electronic or optoelectronic range meter, from which the computer is continuously supplied with information about the correct range to the target. If a range meter operating with optical signals is used, the optical signals from the range meter must of course have another frequency than the radiation pulses from the transmitter 9 used for simulating real projectiles. If a simulator system according to the invention is to be used together with a weapon which is provided with its own accurate range meter, information about the range to the target may of course be obtained from this range meter, wherefore the simulator system does not have to be provided with any range meter of its own.

FIG. 2 shows schematically and in a perspective view a preferred embodiment of the radiation transmitter 9. This includes a casing 35 shown very schematically only, which is mounted on the weapon or coupled to this in such a way that it follows the movements of the weapon in azimuth as well as in elevation. Inside the casing 35 there is a suitable radiation source 13, as for instance a laser, a luminescence diode, a laser diode or a xenon lamp, which can be activated to emit a short pulse of radiation. The radiation from the radiation source 13 is by a suitable optical system, including for instance a condensor 14, a diaphragm 15 and an objective 16, directed as a narrow radiation beam towards a mirror 17, which deflects the radiation beam through an exit opening 18 in the front wall of the casing 35. Consequently, the direction of emission 10 is determined by the mirror 17 which is universally pivoted about a stationary point in the casing 35 so that the emission direction 10 can be moved in azimuth as well as in elevation by variation of the attitude of the mirror 17.

For this purpose the mirror 17 is supported for rotation about an axis SS in a frame 19, which in its turn is supported for rotation about an axis HH in two

stands

20 and 21 which are stationary in the transmitter casing 35. The two axes SS and HH are mutually perpendicular and it is assumed that the transmitter casing 35 is mounted in such an attitude that the axis HH is normally parallel to the elevation axis of the gun barrel, whereas the axis SS is normally parallel to the azimuth or train axis of the barrel.

By rotation of the frame 19 about the axis HH it is consequently possible to move the emission direction 10 in elevation, whereas by rotation of the mirror 17 about the axis SS the emission direction 10 can be moved in azimuth. The mirror 17 and thus also the emission direction 10 can be kept gyro-stabilized independent of the movements of the transmitted casing 35 and thus of the member supporting the transmitter casing by the aid of a gyro-stabilized platform 22 which is supported by the frame 19 and rotatable in this about an axis SS which is parallel to the axis S S. In conventional manner the gyro-stabilized platform 22 is provided with two angular velocity sensing gyros G and G so mounted on the platform 2 2 that the one gyro G senses the angular velocity of the platform 22 relative to the inertial space about the axis S'S' and produces a signal proportional to this angular velocity, whereas the second gyro G senses the angular velocity of the platform 22 about the axis HH and produces a signal proportional to this angular velocity. The output signal from the gyro G can in conventional manner be applied as a control signal to a servomotor M which is stationary in the transmitter casing 35 and coupled to the frame 19 for rotation thereof about the axis HH, whereas the signal from the gyro G can be applied as a control signal to a servomotor M which is coupled to the platform 22 for rotating this about the axis SS. When the signals from the gyros G and G are applied as control signals to the servomotors M and M respectively, the platform 22 is, as well known in the art, maintained stabilized in space about the two axes HH and S'S'.

The gryo-stabilized platform 22 is coupled to the mirror 17 through the frame 19 and also through a link system including two

rigid links

23 and 24. The one end of the link 23 is attached to the gyro-stabilized platform 22, whereas the one end of the link 24 is attached to the mirror 17. The opposite end of the link 24 is shaped as a fork 24a having a straight groove pointing at the pivot centre of the mirror 17. The opposite end of the link 23 is provided with a pin 23a which is displaceable in the fork-shaped end 24a of the link 24. The frame 19 and the gyro-stabilized platform 22 are positioned in the transmitter casing 35 in such a manner that the axis HH is parallel to the radiation beam incident upon the mirror 17 from the radiation source 13 and that the distance between the pivot centre of the platform 22 and the pivot centre of the mirror 17 is equal to the distance from the pivot centre of the platform to the outer end of the link 23. It is appreciated that this connection between the gyrostabilized platform 22 and the mirror 17 has as a result that a given angular rotation of the platform 22 about the axis S'S' causes an exactly equal angular rotation of the emission direction 10 about the axis -5 and that a given angular rotation of the platform 22 about the axis HH causes an exactly equal angular rotation of the emission direction about said same axis. Consequently, the emission direction 10 follows exactly the position of the platform 22 and if the platform 22 is gyro-stabilized relative to the support of the transmitter the emission direction 10 of the transmitter will also be gyro-stabilized relative to said support.

As mentioned in the foregoing, however, the emission direction 10 and thus the mirror 17 shall normally be locked relative to the transmitter casing 35 and thus relative to the direction of fire of the weapon in such an attitude that the emission direction 10 is parallel to the direction of fire of the weapon. In the illustrated embodiment of the invention this is achieved in that the platform 22 is locked in a corresponding attitude by means of the servomotors M and M For this purpose a position signal generator, such as a potentiometer, P and P respectively is coupled to each of the servomotors M and M respectively so as to produce a signal with a magnitude and a polarity dependent upon the angular deviation of the platform 22 about the axis S'S' and the axis HH respectively from the predetermined desired locking posi tion. The electrical connection is shown in FIG. 3, that is the output signals from the position signal generators P and P are through

switches

25 and 26 and the servoamplifiers 27 and 28 applied as control signals to the servomotors M and M respectively. It is appreciated that with this connection the two servomotors will automatically maintain the platform 22 and thus also the mirror 17 and the emission direction 10 in the desired locked position, in which the output signals from the two position signal generators P and P are zero. The object of the

switches

25 and 26 will be discussed in further detail in the following.

FIG. 3 shows, also by way of example, the circuit diagram for an embodiment of the computer 11:. This includes two signal multiplicators, in the illustrated example consisting of potentiometers P1 and P2, which are set in agreement with the range D to the target in some of the manners discussed in the foregoing. The potentiometer P1 is supplied with a constant voltage, which for the sake of simplicity is assumed to have the value 1, whereas the potentiometer P2 is supplied with the output voltage from the potentiometer P1. Consequently, P1 produces a signal proportional to the range D to the target, whereas the potentiometer P2 produces an output signal proportional to D These two signals are connected to separate inputs of an amplifier 29. This amplifier is also supplied with a constant signal, which for the sake of simplicity is assumed to have the value 1. These input signals are amplified and summed in the amplifier 29 with the proportionality constant k k and k respectively so that the output signal of the amplifier 29 is proportional to the first three terms in the series expression (3) for the gravity correction angle U. This output signal is connected to a signal comparator 30, to which also the output signal from the gyro G is applied but with the opposite polarity as compared with the signal from the amplifier 29. The computer 11 includes also a second amplifier 31 which is supplied with the signals proportional to D and D respectively from the two potentiometers P1 and P2 and also with a signal proportional to the muzzle velocity V of a real projectile. These three input signals are amplified and summed in the amplifier 31 with such polarities and in such proportions that the output signal from the amplifier 31 corresponds to the three first terms in the expression (2) for the mean velocity V of the projectile. The output signal from the amplifier 3'1 proportional to V is applied to a signal division circuit 32 which is also supplied with the signal proportional to D from the potentiometer P1 and which is adapted to produce an output signal proportional to D/V that is a signal proportional to the time of flight I to the target for a real projectile. This output signal is supplied to a suitable timing device 33, such as an electric timer circuit, an electro-mechanical timer or similar, so that the time span of this timing device is adjusted to be equal to the computed time of flight I The timing device 33 can be started in that a switch 34 manually operated by the tank crew, for instance the firing button for the tank gun, is closed temporarily.

When the timing device 33 starts, it actuates the two

switches

25 and 26 so that these are switched to their opposite positions. In this way the locking of the gyrostabilized platform 22 and thus of the mirror 17 and the emission direction 10 is released. Instead the output signals from the gyros G and G are connected to the servomotors M and M respectively, whereby the platform 22 and thus also the mirror 17 and the emission direction 10 of the transmitter become gyro-stabilized and independent of any subsequent movements of the tank in azimuth or elevation. As, however, the output signal from the amplifier 29 is connected to the signal comparator 30 with the opposite polarity to the signal from the gyro G the servomotor M will obviously rotate the platform 22 and thus also the mirror 17 and the emission direction 10 of the transmitter about the axis HH with an angular velocity relative to the inertial space which is proportional to the magnitude of the signal from the amplifier 29. At the end of the time span of the timing device 33, which is proportional to the computed time of flight I of a real projectile, the emission direction 10 of the transmitter has consequently been lowered in elevation through an angle exactly equal to the correct gravity correction angle U for the firing of a real projectile at the target. When the timing device 33 runs out after the time of flight t of the projectile, the timing device 33 activates the radiation source 13 in the transmitter 9 to emit a short pulse of radiation. Immediately thereafter the timing device 33 actuates again the

switches

25 and 26 so that they are returned to the positions illustrated in FIG. 3. This causes the servomotor M and M to return the platform 22 and thus also the emission direction 10 of the transmitter to the predetermined locking position, in which the emission direction 10 is parallel to the direction of the gun barrel 4, whereby the simulator system is prepared for a simula tion of the firing of a new projectile.

It is appreciated that also various other embodiments of a simulator system according to the invention are possible. Thus, for instance the radiation transmitter may be designed in various ways. Essential is only that the emission direction of the transmitter can be locked relative to the weapon so as to be parallel to the direction of fire of the weapon, but that this locking can be released and that the emission direction thereafter in its unlocked state is gyro-stabilized and independent of any movements of the weapon and/or the support of the weapon. In said gyro-stabilized unlocked state it must, however, be possible to move the emission direction of the transmitter through a predetermined angle from its initial position in response to the operation of the computer unit in the system.

Of course, also the computer unit can be designed in various ways by the use of various types of computer components and various mathematical expressions for the computation of the gravity correction angle and the time of flight. It is also appreciated that the computer may be designed to compute not only the proper gravity correction angle for the firing at the target but also the proper correction angles necessary for instance due to wind forces upon the real projectile and the rotation of the real projectile. The computer may also be designed to take into consideration any tilt of the elevation axis of the gun barrel at the instant of firing. If the computer unit is amplified in some of these respects, it must compute necessary correction angles for the emission direction of the radiation transmitter in elevation as well as in azimuth, wherefore the computer must actuate the member in the radiation transmitter determining the emission direction for variation of the emission direction in elevation as well as in azimuth.

Finally, it shall be pointed out that the simulator system is not disturbed by any changes of the train angle or the elevation angle of the weapon subsequent to the instant of the simulated firing of a projectile, that is during the computed time of flight for a real projectile, but that a certain disturbance of the operation of the simulator system will appear if the weapon and thus also the radiation transmitter should during said time interval move from its position at the instant of the simulated firing of a projectile. As normally, however, the Weapon is stationary at the instant of firing and hardly can change its position in the terrain in any significant extent during the short time of flight of the projectile, which is of the order of l to 2 seconds, any disturbances of this type in the operation of the simulator system will be extremely small.

What is claimed is:

1. A system for simulating the firing of a weapon (4), comprising: a weapon mounted on a movable weapon carrier, a moving target, a radiation transmitter (9) for emitting a narrow beam of optical radiation coupled to the weapon so as to follow the movements in azimuth and elevation of the direction of fire of the weapon, means for activating said radiation transmitter to emit a short pulse or radiation a predetermined time interval after a manually initiated signal simulating the firing of the weapon, and radiation sensitive receiving means (12) on the target for detecting radiation pulses received at the target, said radiation transmitter includes a member (17), responsive to a pulse of radiation from a radiation source within the transmitter, for determining the emission direction (10) of the transmitter, said member being rotatable for moving said emission direction in azimuth as well as elevation, means for releasably locking said member in a predetermined position relative to the weapon such that the emission direction of the transmitter is parallel to the direction of fire of the weapon, gyro means (G G located within said transmitter for stabilizing said member when in its unlocked state, and servomotor means (M for rotating said member in a direction causing a movement of the emission direction of the transmitter in elevation in agreement with a control signal supplied to said servomotor means, and a computing means (11) adapted to receive information relative to target distance and velocity of an actually fired projectile, to be simulated are provided for computing the time of flight (t for a real projectile fired with the weapon at the target and the proper gravity correction angle (U) for the weapon when firing a real projectile at the target and for producing a signal proportional to said gravity correction angle, said computing means being adapted in response to said manually initiated signal simulating the firing of a projectile to release the locking of said member (17) and connect said signal proportional to the computed gravity correction angle as a control signal to said servomotor means (M and to activate said radiation transmitter after a time interval equal to said computed time of flight.

References Cited UNITED STATES PATENTS 3,143,811 8/1964 Tucci et al. 3525 3,243,896 4/1966 Immarco et al 3525 3,452,453 7/1969 Ohlund 3525 FOREIGN PATENTS 1,114,094 5/1968 Great Britain 3525 ROBERT W. MICHELL, Primary Examiner I. H. WOLFF, Assistant Examiner US. Cl. X.R. 273101.1