WO2021124330A1

WO2021124330A1 - System for precision guidance of munitions

Info

Publication number: WO2021124330A1
Application number: PCT/IL2020/051298
Authority: WO
Inventors: Avishay Guetta; Michael Yagudaev; Dekel SOLOMON; Doron Shoham; Boris Frenkel
Original assignee: SHILAT OPTRONICS Ltd
Current assignee: SHILAT OPTRONICS Ltd
Priority date: 2019-12-16
Filing date: 2020-12-16
Publication date: 2021-06-24
Anticipated expiration: 2022-06-16
Also published as: WO2021124330A8; IL271483A

Abstract

Methods and systems for trajectory correction of a projectile or a munition during flight. The projectile comprises a force generator disposed on a module rotatable around the projectile's longitudinal axis, to generate a force in a direction to correct the trajectory of the projectile. The force generator may have a nozzle, adapted to expel a jet of gas in the desired direction, and a valve for controlling the duration of the expulsion. Guidance of the projectile may be achieved by defining the position of the target on a camera array using a telescopic sight, and detecting an optical signal emitted by an encoded light source, mounted on the projectile, and determining its position in the camera array. Determination of the range of the projectile then enables calculation of the actual trajectory, and if necessary, optically encoded correction signals are sent to the projectile for appropriate trajectory correction.

Description

SYSTEM FOR PRECISION GUIDANCE OF MUNITIONS

FIELD

The present disclosure relates to the field of projectile trajectories, and specifically to systems and methods of adjusting the trajectory of a munition or missile during flight.

BACKGROUND

When a projectile is launched towards its target, whether continuously-propelled or in ballistic motion, forces such as winds, air pockets, or gravity may cause the projectile to veer off course, and thus away from its target.

In order to adjust the trajectory of a projectile during flight, a force needs to be applied to the projectile, in a direction other than the direction of motion, most conveniently from a calculation viewpoint, at an angle perpendicular to the projectile’s direction of motion, which is generally along the longitudinal axis of the projectile.

In order to generate such a force, a number of force generators are installed on the projectile, and instructed to generate the force as required. Each force generator generally comprise a nozzle for releasing a jet of compressed fluid, generally a gas, aligned in a direction orthogonal to the axis of the projectile, such that the release of the jet of gas generates a force lateral to the motion of the projectile, and in the opposite direction to the nozzle, thus affecting the trajectory of the projectile. The flow of the gas is typically controlled by a valve.

Prior art projectiles generally use at least three such force generators situated at different points around the projectile’s axis, to generate forces in different directions, in order to generate an overall combined force in the direction required to adjust the trajectory of the projectile during flight. Each nozzle would then require its own valve to determine the direction of the combined force, and this would require a complex valving and valve timing system.

The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.

SUMMARY

The present disclosure describes new exemplary systems for guidance systems for use on a projectile, which overcomes the disadvantages of the use of multiple force generators. In the presently described systems, the projectile is equipped with a variable direction correction module, implemented by mounting the force generator on a section of the projectile that is rotatable around the proj ectile’ s long axis. A force generator is disposed on the rotating module, such that a force can be generated at any orientational angular direction around the projectile’s longitudinal axis by rotating the rotatable correction module to position the force generator at the desired orientational angular direction on the rotating module. Thus during the flight of the projectile, should the trajectory of the projectile need adjusting, the rotating module can be rotated to direct the force generator at the desired orientational angular direction around the projectile’s longitudinal axis. This has the advantage that a force can be generated in any required direction using just one force generator, as opposed to using multiple force generators as used on prior art projectiles, which generate a force in the desired direction by means of their concomitant controlled valve arrangement. The force generator itself may conveniently comprise a nozzle which is connected by a valve to a source of compressed gas, such that opening of the valve ejects a stream of gas from the nozzle, thus generating a reactionary force on the nozzle and hence the entire projectile in the opposite direction to the direction of the gas stream.

Many munitions are fired with an applied spin, in order to increase stability during flight. Under these circumstances, in order to generate a force in a desired direction, prior art systems need to coordinate the operation of multiple force generators at a very fast rate in order to maintain a force in one direction relative to the ground, to counteract the effect of the spin on the force generators of the projectile. This is done for instance by synchronizing the operation of the force generators with the spin. Thus, if the trajectory of the projectile needs to be changed to be oriented so that it acquires an additional motion in the -x direction, and to do so a force needs to be generated in the opposing direction, +x, then each force generator rapidly generates a force for a short predetermined time during which the force generator is pointing in the x direction, and stops generating a force as soon as the projectile has spun such that that generator is no longer pointing in direction x. This involves a complex, timed valve sequencing procedure.

In order to obviate the need for a complex synchronization of multiple force generators, in the currently disclosed system, the rotating module incorporating the force generator emitting a steady stream of gas, is spun at the same rotational speed as the projectile, but in the reverse direction. This essentially cancels out the effect of the rotation of the projectile, by generating a reference co-ordinate system of the force generator which has an essentially stationary angular orientation in space, and hence reiatrve to the ground. As a result, a static frame of reference is now generated for use in defining the required direction of force relative to the horizontal plane defined by the ground, without the effect of the spin of the projectile.

Thus, if the trajectory of the spinning projectile needs to be oriented more in direction -x, and to do so a force needs to be generated in an opposing direction x, the effective angular position of the force generator can be implemented using the spinning module. This may be performed by decreasing or increasing the speed of the spinning module for a short predetermined time, such that it no longer spins at essentially the same speed as the projectile for that short predetermined time, and thus the effective angular position of the spinning module can be rotated around the projectile’s longitudinal axis, to effectively direct the nozzle or force generator in direction x. As soon as the force generator is virtually pointing in the desired direction, the spinning module is returned to spinning at the same angular speed as the spin of the projectile, but in the reverse direction. Thus the force generator has now achieved a new angular position, pointing in direction x, despite the fact that the projectile, and the force generator, are both spinning rapidly in opposite directions, and application of the gas stream from the nozzle can now implement the required force on the projectile in the -x direction.

The term projectile is used throughout the application to mean any object travelling through space on a trajectory, and the force causing the projectile to travel forwards may be generated either by kinetic energy transferred to the projectile only at the time of its projection, which may be called the firing time, or the projectile may comprise a propulsion mechanism for continuous thrusting of the projectile forward during its flight, such as on a rocket propelled missile.

Another novel feature of the presently disclosure relates to the method of guidance of the projectile to its target. A conventional way of achieving accurate targeting is by applying a designating beam to the target and using a seeker mechanism on the projectile to home onto the designated spot. This method has the disadvantage that the designating beam can be readily detected, and hence its source targeted by the target’s forces, and additionally, that the seeker head on the projectile may considerably increase the cost and complexity of the projectile. According to the projectile guidance system described in this disclosure, an optical guidance system is described in which the position of the target is first acquired by aiming the optical direction of an imaging system at the target, using a passive telescopic sight bore-sighted to the optical imaging system. This has the advantage that it is completely passive and hence not readily detected. The optical imaging system is thus able to define the pixels of the image representing the target on its screen. The optical imaging system is also able to define the position of the projectile, by detecting a coded optical beam emitted by the projectile. The use of a detection imaging camera of the type described in the system described in the published International patent application No. WO2011/073980 for “Laser Daylight Designation and Pointing” having a common inventor with the present application, enables the detection of the coded optical beam emitted by the projectile to be readily detected even against the high optical intensity of the daytime sky. The azimuthal and elevation position of the projectile is thus known, and can be displayed on the screen of the imaging camera, together with the previously determined position of the target, which may advantageously be displayed at the center of the image. Thus, as the projectile gets closer to the target, the pixels representing its position should move closer to the target pixel position.

The above described detection camera enables the azimuth and elevation of the tracked projectile to be determined, but not its range, which is the third factor needed for determining its position in space. In order to determine whether the projectile is on its correct course to hit the target, and hence to determine whether any course correction is required, the range must also be inserted into the controller for calculating the actual trajectory and whether the projectile needs course correction to hit its target. According to a first exemplary method, the system then uses the pre-calculated trajectory of the munition or projectile, based on its initial muzzle velocity and factors such as the wind speed and ambient temperature, to calculate the expected range of the projectile, and hence the expected strike position. In order to increase the accuracy of the range determination, according to another exemplary method, a laser range finder can be used, projecting an encoded beam towards the projectile, and detecting its reflection from a retroreflector mounted on the projectile. Once all of the controller calculations have been completed, the system can send course changing instructions, if necessary, by means of an optical communication link to the munition, or by any other wireless transmission link.

There is thus provided in accordance with an exemplary implementation of the devices described in this disclosure, a system for adjusting the trajectory of a projectile during flight, the projectile comprising:

(i) a rotatable module comprising a unit adapted to generate a force on the projectile in a direction other than the longitudinal axis of the projectile,

(ii) a motor adapted to rotate the rotatable module around the longitudinal axis of the projectile, and (iii) a controller adapted to control:

(a) the orientation of the rotatable module around the longitudinal axis of the projectile, and

(b) the duration of the application of the force expulsion of the jet of fluid, such that the trajectory of the projectile is adjusted according to control instructions.

In such a system, the force generator may comprise at least one nozzle adapted to expel a jet of fluid in a direction generally orthogonal to the longitudinal axis of the projectile. The jet of fluid may be a jet of gas, the force generator further comprising a container adapted to hold a volume of the compressed gas and a valve for releasing the gas through the at least one nozzle. Alternatively, the force generator may comprise a device for combustion of a solid or liquid propellant for generating the force.

In any of the previously described systems, the controller may receive trajectory correction signals from a control system on the ground. Alternatively, the projectile may further comprise a seeker, the seeker adapted to identify a target, and to provide correction instructions to amend the projectile trajectory towards the target. Furthermore, the controller may be adapted to continuously control the trajectory during flight. According to a further implementation of such systems, the projectile may further comprise an inertial unit configured to measure the orientation and angular velocity in space of the projectile.

In any of the above described systems, the force generator may be located close to the center of gravity of the projectile, such that actuation of the force generator does not amend the pitch of the projectile. Alternatively, the force generator may be located close to an extremity of the projectile, such that actuation of the force generator amends the pitch of the projectile.

In any of the above systems, if the projectile is spinning during flight, the motor is adapted so that when no correction is being applied to the projectile, it rotates the rotatable module continuously around the longitudinal axis of the projectile, at the same rotational speed as the spinning projectile, but in the opposite angular direction, such that an essentially static spatial frame of reference is generated for the force generator. In such a case, when a correction of the trajectory of the projectile is required, the controller may be adapted to control the speed of spin of the rotating module for a predetermined time, such that the rotating module can be configured to spin at a rate slower or faster than the spin of the projectile. The system is then such that the change of speed of spin ot the rotating module changes the angle at which the frame of reference of the force generator is directed.

In any of the previous embodiments involving a spinning projectile, the controller may be further adapted to control the duration of force generated by the force generator, such that the controller is adapted to adjust the trajectory of the projectile by a desired direction and amount.

Finally, in any of the previously described systems, the controller can maintain a predetermined trajectory by comparing the measured position of the projectile with the predetermined trajectory.

There is further provided according to another implementation of the present application, a method for guiding a projectile along a trajectory towards a target, the projectile having a force generator adapted to generate a force lateral to the longitudinal axis of the projectile, the method comprising:

(i) monitoring the trajectory of the projectile to determine whether the trajectory requires adjusting in order for the projectile to reach the target,

(ii) determining the magnitude and direction of a force needed from the force generator to adjust the trajectory as required, the force generator being disposed on a module, rotatable around the longitudinal axis of the projectile,

(iii) rotating the rotatable module around the longitudinal axis of the projectile, such that the orientation angle of the force generator around the longitudinal axis is the angle required to generate the force in the required direction, and

(iv) applying the force for a time calculated to adjust the trajectory as required.

In such a method, the force generator may comprise at least one nozzle adapted to expel a jet of fluid in a direction generally orthogonal to the longitudinal axis of the projectile. The jet of fluid may be a jet of gas, the force generator further comprising a container adapted to hold a volume of the gas in a compressed state, and a valve for releasing the gas through the at least one nozzle.

There is yet further provided according to another implementation of the present application, an optical system for guiding a projectile along a predetermined trajectory to a target, the system comprising: (i) a two-dimensional imaging camera adapted to detect encoded light signals from a source on the projectile, and to determine the azimuthal and elevation position of the projectile from the imaged positions of the encoded light received form the projectile,

(ii) a sighting telescope coupled to the two-dimensional imaging camera, such that the two- dimensional imaging camera can be bore-sighted to the target, and

(iii) a controller determining from the relative positions of the pixels representing the target and the pixels representing the projectile, in combination with the range of the projectile, whether the projectile is proceeding along its predetermined trajectory to the target.

In such a system, the encoded light signals from the source on the projectile enable the projectile to be identified against a background illumination of higher intensity than the light source. In either of the above described cases, the encoded light signals may be generated by a pulsed CW laser diode.

Additionally, the range of the projectile may be determined either by a calculation using the weight, launch speed and launch angle of the projectile, and at least one of the wind speed and the ambient environmental temperature. Alternatively, the range of the projectile may be determined by use of a laser rangefinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which:

Figs.1 A and IB illustrate schematically an exemplary projectile according to the currently disclosed system having a rotatable module for directing a force generator for trajectory correction of the projectile during flight;

Figs 1C shows an alternative embodiment with the force applied off-axis from the projectile; Fig. ID is a cross sectional view of the force generator and its rotational abilities;

Fig. 2 illustrates one exemplary implementation of an optical guidance system, incorporating a control system remote from the projectile to determine the relative azimuth and elevation angles between the projectile and the target;

Fig. 3 shows a second exemplary implementation of such an optical guidance system; and Fig. 4 shows yet another exemplary implementation of an optical guidance system, but unlike that of Figs. 2 and 3, utilizing a designating beam for a projectile having a seeker unit. DETAILED DESCRIPTION

Reference is first made to Fig. 1A to Fig. ID, illustrating various exemplary implementations for adjusting the path of a projectile during flight, by incorporating on the projectile, a force generator 18, mounted in a rotatable module that can rotate around the longitudinal axis of the projectile.

As illustrated in Figs. 1A and IB, the projectile 16 of the currently disclosed system is shown having a rotatable module 2, which can rotate around the longitudinal axis 5 of the projectile 16. The rotating module 2 rotates the force generator 18 which generates a force F for trajectory correction of the projectile 16 during flight. The exemplary force generator shown in Figs. 1A to ID comprises a nozzle 19 for releasing a jet of compressed fluid, generally a gas, aligned in a direction lateral to the axis of the projectile, such that the release of the jet of gas generates a force F lateral to the motion of the projectile, and in the opposite direction to the nozzle, thus affecting the trajectory of the projectile. The flow of the gas is typically controlled by a valve. Although a single nozzle is shown in the example devices of this disclosure, it is to be understood that a double or a multiple nozzle may be used to provide the same effect. As an alternative, the force generator 18, may use combustion of a solid or liquid propellant to generate the force.

The system uses an associated flight controller, which includes information regarding the projectile's target destination, and which monitors the flight path of the projectile to determine whether the projectile is on course to reach its target, or whether the trajectory of the projectile needs appropriate correction. The controller may be remote from the projectile, such as in the launcher station, or, alternatively, may be mounted on the projectile. In some embodiments, part of the controller is mounted on the projectile, and some is remote from the projectile, as will be explained hereinbelow.

Fig. IB illustrates schematically the detailed operation of the system. The system includes a controller (not shown), which may track the projectile’s orientation and angular velocity in space using an inertial unit 9, mounted on the projectile, or alternately or in addition, using optical guidance techniques, as will be mentioned hereinbelow. This enables the calculation as to whether the projectile is maintaining a satisfactory trajectory, or whether a force is needed to correct the trajectory of the projectile. Should correction be required, the controller instructs an electric motor 10 to adjust the orientation angle of the rotating module 2 around the projectile’s longitudinal axis 5, via rotation ot the rotating module 2, so that force generator 18 points in the direction required to generate the appropriate force F. The angular orientation of the force and the magnitude of force to be generated may be calculated by the controller using a predefined trajectory calculating algorithm, and the controller may thereby send the rotating module 2 instructions regarding the direction in which to generate the force and the duration of the force, in cases where the force is constant, or the strength at which the force should be generated, the latter case being where there is control over the extent of the opening of the nozzle valve. The angular position of the force generator 18 relative to the projectile may be measured by a rotary encoder, which may be optical or magnetic, or by its own inertial unit. The force F may advantageously be applied close to the projectile’s center of gravity 4. Typically, the force is generated at an angle generally perpendicular to the longitudinal axis 5 of the projectile, however the force may be generated at any angle, including at an angle to the longitudinal axis 5 of the projectile, as will be described with reference to Fig. 1C hereinbelow.

As is commonly done, the projectile may be fired or launched spinning around it longitudinal axis, for maintenance of stability during flight, and to average out forces which may affect the projectile’s trajectory. In embodiments in which the projectile 16 is directed with an applied spin, the rotating module 2 is generally configured to spin around the longitudinal axis 5 of the projectile, at the same speed as the projectile 16, but in the reverse direction. The rotation speed of the rotating module can be controlled by using the output of the inertial unit to provide the motor controller with instructions for the required motor current. As a result of the spinning module spinning in the reverse direction of the spin of the projectile but at the same speed, the force generator 18 remains in a fixed orientational angular position relative to the rotational angle around the direction of the trajectory of the projectile, and hence also relative to the ground, such that the effective direction in which the force generator is pointing is constant. This cancels out the spinning effect of the rotation of the projectile 16 with regard to the angular direction in which the force generator is directed.

Should the controller determine that the trajectory of the projectile needs adjusting during the flight of the projectile, the spinning module 2 can be controlled such that it is instructed to rotate for a limited short period of time at a slower speed, or a faster speed (but in a reverse direction) than the spinning projectile itself, such that the orientational angular position of the force generator is transformed around the projectile’s longitudinal axis 5, such that force F can be generated in the desired direction. Reference is now made to Fig. 1C which show an additional exemplary embodiment of the devices and systems of the present disclosure, in which rotating module 2B is placed at the rear end of the projectile 16. In this case, the operation of the force generator, even if directed in a radial direction, will exert a moment on the projectile, and will thus have an effect on the pitch of the projectile, altering its trajectory. Such a pitch correction may not be the case for the force generator of the embodiments in Figs. 1A and IB, where the force generator is intended to act through the center of gravity of the projectile. In addition, the force generator 18 in the embodiment of Fig. 1C is shown as a tilting force generator, such that its moment can be adjusted as necessary by tilting the unit 18 at different directions relative to the longitudinal axis 5 of the projectile. Such adjustment of the moment is in addition to that generated by changing the level of the force provided by the generator. The force generator can also be positioned on axis, and all of the pitch adjustment generated by tilting the force generator. In an alternative embodiment, the rotating module 2B can be placed at the front end of the projectile.

Reference is now made to Fig. ID showing a cross-sectional view of the rotating module 2 illustrated in Figs. 1A and IB. The force generator 18 can be rotated such that it rotates in a clockwise direction 11, or anti-clockwise direction 12, such that force F can be effectively generated from any point around the projectile’s circumference 13. The rotating module may only be rotatable in one direction, or may be able to rotate both clockwise and anti-clockwise.

Reference is now made to Fig. 2, which illustrates one exemplary implementation of a guidance system, incorporating a control system 22 remote from the projectile 21 to determine the relative azimuth and elevation angles between the projectile 21 and the target 27, and, should the projectile be moving off-course, to instruct the projectile 21 to adjust its trajectory during flight so that it hits its target 27. The projectile 21 may optionally use a rotatable force generator as described with reference to Figs. 1A to Fig. ID hereinabove, to adjust its trajectory, or it may use any other motion adjustment mechanism for adjusting the trajectory of the projectile, such as the use of variable guidance fins.

Fig. 2 illustrates a launcher 23, for launching a projectile 21 towards a target 27. In a common exemplary embodiment, the “launcher” could be a gun or cannon barrel, and the projectile a shell fired by the gun at the target, or a rocket propelled munition, which, after firing, continues on its trajectory ballistically, or even with propulsion assistance. The term “launcher” or “launch” is intended to cover all such embodiments. The projectile 21 is shown in flight. A control system 22, which may be mounted on the launcher 23 of the projectile, or disposed in another location, first determines the position of the target 27 by aligning a smart imaging camera 25, to define the position of the target in the camera image array. This is achieved by ensuring that the sighting telescope 26 used to detect the target 27 is bore-sighted with the imaging camera 25.

Using the example of a shell munition fired from a cannon 23, the munition 21 is aimed at the target 27 using a trajectory computer (not shown) which calculates the required elevation and azimuth of the barrel, and, taking into account the expected muzzle velocity of the projectile and its known weight, and the wind speed and temperature conditions, calculates the expected trajectory of the projectile, from the moment it leaves the launcher barrel 23 to the target position 27. According to this first embodiment, the position of the projectile along its trajectory may be determined by the measured time elapsed from the point of firing, and interpolating that time onto the model of the trajectory calculated by the trajectory computer.

The actual position of the projectile along its trajectory is determined by using the range as calculated above, and a smart imaging camera 25 to determine the elevation and azimuth of the projectile. The smart imaging camera is so-called since it should advantageously include circuitry not only to detect the pixel levels in the images detected, but also is in logic connection with circuitry which is able to analyse the pixel levels obtained, and to distinguish those related to a signal of interest, and to input the position of such pixels of interest to the system computer for generating positional data. The smart imaging camera 25 detects the position of the projectile in the air by means of an optical signal emitted by an encoded light source 29, preferably mounted in the rear part of the projectile. The smart camera is recognizes the pixel or pixels in the smart camera imaging array, in which optical signals emitted by the encoded light source 29 are detected above the background illumination, which may have a significantly higher level than the encoded optical signals. This can be optionally achieved by the discrimination circuitry described in the above mentioned International patent application No. WO201 1/073980 for “Laser Daylight Designation and Pointing” Laser Daylight Designation System ("LDDP"), having a common inventor, and common ownership with the current application. Other known methods of detection may however, also be used.

The launcher controller 22 tracks the position of the projectile using the above described information, and can follow its progress by the position of the pixel or pixels representing the projectile. Since the smart camera 25 is bore-sighted onto the target 27, it can also see the target position, most conveniently positioned at the centre of the image. If the flight controller determines that the projectile is off course from its predetermined trajectory, and will thus miss the target, it instructs an optical communication transmitter or transceiver, 24 to transmit optically coded instructions to the projectile for altering its course anywhere in the trajectory. The projectile carries an optical receiver 28 for receiving these instructions. The projectile 21 uses the correction signals to adjust its trajectory as instructed, optionally by generating a force in the required direction, using the force generator controlled by rotating/spinning module described in Figs. 1A-D above. The angular orientation of the force and the magnitude of force to be generated may be calculated by a controller on the projectile 21, or may be provided by the control system 22. The projectile can thus be guided along the whole of its trajectory, to ensure that it hits its intended target 27 accurately.

In order to enable the munition to be tracked over a wide region, the optical transmission and detection components of the guidance system should concomitantly have large fields of view. Thus, as shown in Fig. 2, the smart camera 25 has a large field of view, designated A in the drawing, and the optical instruction transmitter or transceiver 24, has a corresponding broad file of view B, both so that the munition can be tracked and controlled over a large range in the field. Similarly, the encoded light source 29 on the munition, also has a large field of view C, so that it can be detected by the smart camera 25 at largely different ranges, bearings and altitudes. The optical receiver or transceiver 28 on the munition should likewise have a lagre field of view.

This system therefore enables the accurate guidance of a projectile to its target with the double advantages that (i) there is no need for a generally high-cost seeker on the projectile, and (ii) there is no need for an active designating beam transmitted from the launcher system or nearby, which could give away to the target the information that it is being targeted, and from where it is being targeted.

Reference is now made to Figure 3, which, in addition to the trajectory guidance system described hereinabove with reference to Fig. 2, uses a laser range finder (LRF) 39 to actively determine the accurate range of the projectile 21. This range is thus accurately known without reliance on a calculated flight trajectory using assumptions regarding air resistance, wind direction and the temperature in the region of the flight path of the projectile. More accurate correction signals can thus be sent to the projectile. The projectile position determination by the control system is thus based on the azimuth-elevation angles that are measured by a smart imaging camera 25, using the system described hereinabove with reference to Fig. 2, and by the accurate measurement of the range to the projectile, such that the position is known with high accuracy and at a high sampling rate.

The LRF 39 is adapted to transmit an encoded detection beam over a wide angular range D, unlike a conventional LRF that transmit a collimated beam of light. An optical retro -reflector device 31 mounted on the munition 21 reflects the LRF light directly to the LRF receiver 39, where the potentially weak encoded reflected beam can be detected by its encoding from the strong optical background signal.

The control system 22 can then send correction control signals to the projectile, which may instruct a rotating/spinning module to position a force generator in the required position, as explained hereinabove, and can generate a force in the direction required to affect the trajectory as instructed by the launcher.

Reference is now made to Fig. 4 which illustrates an alternative implementation of the presently disclosed systems and methods, in which the projectile 41 comprises a seeker 48 to determine whether the flight path of the projectile 41 is on-course, such that the projectile is set to reach its target 47, and a rotating module 46, as is described hereinabove with reference to Fig. 1A to Fig. ID, to correct the trajectory of the projectile 41, should it be required.

In one implementation, a trajectory control system 42, which optionally comprises the launcher 43 of the projectile 41, includes a laser designator 44 which is directed towards the desired target 47 of the projectile 41, and designates the target 47 with an encoded laser beam. This encoded beam may advantageously be a modulated CW laser beam, as is described in the above referenced WO2011/073980. The seeker 48, which is mounted in the nose of the projectile 41, locates the encoded laser beam impinging on the target 47, typically using a tracking camera of the type described in WO2011/073980. The projectile 41 is controlled by an internal flight- control system 45 that receives correction signals from the integrated seeker 48, such that should the trajectory of the projectile require correction towards the designator spot on the target, the flight controller instructs the rotating module 46 to rotate such that the force generator points towards a desired orientational angle, such that a force can be generated in the direction as determined by the flight controller 45.

Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present drsciosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. Furthermore, it is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.

Claims

CLAIMS We claim:

1. A system for adjusting the trajectory of a projectile during flight, the projectile comprising: a rotatable module comprising a unit adapted to generate a force on the projectile in a direction other than the longitudinal axis of the projectile; a motor adapted to rotate the rotatable module around the longitudinal axis of the projectile; and a controller adapted to control:

(i) the orientation of the rotatable module around the longitudinal axis of the projectile, and

(ii) the duration of the application of the force expulsion of the jet of fluid, such that the trajectory of the projectile is adjusted according to control instructions.

2. A system according to claim 1 wherein the force generator comprises at least one nozzle adapted to expel a jet of fluid in a direction generally orthogonal to the longitudinal axis of the projectile.

3. A system according to claim 2 wherein the jet of fluid is a jet of gas, the force generator further comprising a container adapted to hold a volume of the compressed gas and a valve for releasing the gas through the at least one nozzle.

4. A system according to claim 1 wherein the force generator comprises a device for combustion of a solid or liquid propellant for generating the force.

4. A system according to any of the previous claims wherein the controller receives trajectory correction signals from a control system on the ground.

5. A system according to any of the previous claims wherein the projectile further comprises a seeker adapted to identify a target, and to provide correction instructions to amend the projectile trajectory towards the target.

6. A system according to any of the previous claims wherein the controller is adapted to continuously control the trajectory during flight.

7. A system according to any of the previous claims wherein the projectile further comprises an inertial unit configured to measure the orientation and angular velocity in space of the projectile.

8. A system according to any of the previous claims wherein the force generator is located close to the center of gravity of the projectile, such that actuation of the force generator does not amend the pitch of the projectile.

9. A system according to any of the previous claims wherein the force generator is located close to an extremity of the projectile, such that actuation of the force generator amends the pitch of the projectile.

10. A system according to any of the previous claims, adapted for use on a spinning projectile, wherein, when no correction is being applied to the projectile, the motor is adapted to rotate the rotatable module continuously around the longitudinal axis of the projectile, at the same rotational speed as the spinning projectile, but in the opposite angular direction, such that an essentially static spatial frame of reference is generated for the force generator.

11. A system according to claim 10 wherein when a correction of the trajectory of the projectile is required, the controller may be adapted to control the speed of spin of the rotating module, for a predetermined time, such that the rotating module can be configured to spin at a rate slower or faster than the spin of the projectile.

12. A system according to claim 11, wherein the change of speed of spin of the rotating module changes the angle at which the frame of reference of the force generator is directed.

13. A system according to any of claims 10 to 11 wherein the controller is further adapted to control the duration of force generated by the force generator, such that the controller is adapted to adjust the trajectory of the projectile by a desired direction and amount.

14. A system according to any of the previous claims, wherein the controller maintains a predetermined trajectory by comparing the measured position of the projectile with the predetermined trajectory.

15. A method for guiding a projectile along a trajectory towards a target, the projectile having a force generator adapted to generate a force lateral to the longitudinal axis of the projectile, the method comprising: monitoring the trajectory of the projectile to determine whether the trajectory requires adjusting in order for the projectile to reach the target; determining the magnitude and direction of a force needed from the force generator to adjust the trajectory as required, the force generator being disposed on a module, rotatable around the longitudinal axis of the projectile; rotating the rotatable module around the longitudinal axis of the projectile, such that the orientation angle of the force generator around the longitudinal axis is the angle required to generate the force in the required direction; and applying the force for a time calculated to adjust the trajectory as required.

16. A method according to claim 15, wherein the force generator comprises at least one nozzle adapted to expel a jet of fluid in a direction generally orthogonal to the longitudinal axis of the projectile.

17. A method according to claim 16 wherein the jet of fluid is a jet of gas, the force generator further comprising a container adapted to hold a volume of the compressed gas and a valve for releasing the gas through the at least one nozzle.

18. An optical system for guiding a projectile along a predetermined trajectory to a target, the system comprising: a two-dimensional imaging camera adapted to detect encoded light signals from a source on the projectile, and to determine the azimuthal and elevation position of the projectile from the imaged positions of the encoded light received form the projectile; a sighting telescope coupled to the two-dimensional imaging camera, such that the two- dimensional imaging camera can be bore-sighted to the target; and a controller determining from the relative positions of the pixels representing the target and the pixels representing the projectile, in combination with the range of the projectile, whether the projectile is proceeding along its predetermined trajectory to the target.

19. A system according to claim 18, wherein the encoded light signals from the source on the projectile enable the projectile to be identified against a background illumination of higher intensity than the light source.

20. A system according to either of claims 18 and 19, wherein the encoded light signals are generated by a pulsed CW laser diode.

21. A system according to any of claims 18 to 20, wherein the range of the projectile is determined by a calculation using at least the weight, the launch speed and launch angle of the projectile, and at least one of the wind speed and the ambient environmental temperature.

22. A system according to any of claims 18 to 20, wherein the range of the projectile is determined by use of a laser rangefinder.