Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41G—WEAPON SIGHTS; AIMING
  • F41G7/00—Direction control systems for self-propelled missiles
  • F41G7/20—Direction control systems for self-propelled missiles based on continuous observation of target position
  • F41G7/22—Homing guidance systems
  • F41G7/226—Semi-active homing systems, i.e. comprising a receiver and involving auxiliary illuminating means, e.g. using auxiliary guiding missiles
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41G—WEAPON SIGHTS; AIMING
  • F41G7/00—Direction control systems for self-propelled missiles
  • F41G7/20—Direction control systems for self-propelled missiles based on continuous observation of target position
  • F41G7/22—Homing guidance systems
  • F41G7/2273—Homing guidance systems characterised by the type of waves
  • F41G7/2293—Homing guidance systems characterised by the type of waves using electromagnetic waves other than radio waves
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F42—AMMUNITION; BLASTING
  • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
  • F42B10/00—Means for influencing, e.g. improving, the aerodynamic properties of projectiles or missiles; Arrangements on projectiles or missiles for stabilising, steering, range-reducing, range-increasing or fall-retarding
  • F42B10/60—Steering arrangements
  • F42B10/66—Steering by varying intensity or direction of thrust
  • F42B10/661—Steering by varying intensity or direction of thrust using several transversally acting rocket motors, each motor containing an individual propellant charge, e.g. solid charge

Definitions

• the munition includes a plurality of photoconductive sensing elements that both enable calculation of a variance between the flight axis of the munition and an illuminated target and trigger at least one on-board diverter to reduce that variance.
• Projected munitions frequently include a guidance seeker system that enables the projectile to calculate a variance from a target and to make one or more in-flight course corrections to increase the likelihood of the projectile disabling or destroying the target.
• One such guidance seeker system is disclosed in United States Patent No. 5,529,262 by Horwath that discloses a guidance seeker system actuated via a continuous beam of ultraviolet, visible or infrared light.
• This seeker system includes a reticle with concentric, alternating, bands of light transmitting and light non-transmitting rings.
• the beam generates pulses as the target moves across the reticle field. The periodisity of these pulses is used to determine deviation of the target from a center line of the reticle. Circumferential thrusters on the projectile are then used to effect a necessary course change.
• U.S. Patent No. 6,076,765 by Horwath utilizes a reticle having a pattern discontinuity effective to generate a singly periodic pulse once each projectile revolution.
• the periodisity of pulses generated by the target sweeping across the reticle field enables the projectile to determine the line of flight variance between the projectile and the target.
• the singly periodic pulse enables the projectile to determine its rotation position. Utilizing this information, an appropriate ring diverter is fired to reduce or eliminate the variance.
• Spinning reticle-based guidance seeker systems require a constant light source.
• light is not limited to the visible spectrum, but includes infrared, ultra-violet as well as other portions of the spectrum.
• an infrared source on the target is utilized, i.e. a "heat seeking" missile.
• passive guidance systems Such systems where the seeker is drawn to a light source originating on the target are referred to as passive guidance systems.
• a semi-active guidance system guides a projectile to a target that is externally illuminated.
• external illumination is by a laser beam.
• the laser generating this laser beam may be mounted on the projectile, or alternatively, located on a separate platform, such as a helicopter or spotter plane.
• One semi-active guidance seeker system is disclosed in United States Patent No. 5,102,065 to Couderc et al. This patent discloses a homing system utilizing a laser that tracks both a target and a missile. The homing system determines the variance between the two and transmits course correction instructions to the missile that are then effected by small explosive charges or rudder adjustments.
• the above mentioned guidance seeker systems require a steady state target signal or a steady state illumination signal from a target designator. They may also be amenable to pulsed signals having a repetition rate much faster than the highest frequency signal generated by the seekers.
• the laser designator To reduce the power required, and therefore the size and cost of laser designators, it is desired for the laser designator to be a low repetition rate laser that generates pulse sequences too slow for the operation of the prior art guidance seekers. There remains, therefore, a need for a guidance seeker system effective for use with low repetition rate pulse lasers that may be utilized with either spinning projectiles or nonspinning projectiles.
• the guidance seeker system is useful with both pulsed and nonpulsed target designators and with both spinning and nonspinning projectiles.
• the guidance seeker system includes an optics package having a plurality of photoconductive sensing elements. These photoconductive sensing elements are electrically coupled to one or more diverters that are disposed about an exterior surface of the projectile. Selective firing of diverters guides the projectile to the target.
• the optics package includes a lens system that transmits the target designator beam to the photoconductive sensing elements as either a focused spot or as a defocused spot.
• the guidance seeker system is useful with target designators that generate beams of short pulses with slow pulse repetition rates and may be used to discern coded laser pulses.
• Another advantage of the guidance seeker system of the invention is that it calculates and corrects for variance from a target utilizing a focused beam. When used in a defocused beam mode, the seeker system determines and corrects for both variance and projectile rotation.
• the guidance seeker system includes a recirculating shift register that compensates for a prefired or otherwise inactive diverter.
• a guidance seeker system effective to guide a projectile to a target comprising an optics package disposed at a forward end of the projectile.
• the optics package includes a plurality of photoconductive sensing elements and has a lens disposed between the target and the photoconductive sensing elements at a distance, D, from the photoconductive sensing elements.
• a plurality of course diverters are mounted on an exterior surface of the projectile wherein illumination of one or more of the photoconductive sensing elements causes the plurality of course diverters to reduce a variance between a present flight path of the projectile and the target.
• Figure 1 graphically illustrates short duration, low repetition rate, pulses generated by a laser designator.
• Figure 2 graphically illustrates coding of laser pulses.
• Figure 3 graphically illustrates a portion of the optics associated with the guidance seeker system of the present invention.
• Figure 4 is a top planner view of a photodetector containing a plurality of photoconductive sensing elements useful with the guidance seeker system of the invention.
• Figure 5 is a perspective, and partially broken, view of a projectile employing the guidance seeker system of the present invention.
• Figure 6 illustrates the interaction between a plurality of photoconductive sensing elements and a plurality of course diverters in accordance with the invention.
• Figure 7 illustrates the application of a defocused target designator beam in accordance with the invention.
• FIG. 8 graphically illustrates the information obtained from the defocused target beam of Figure 7.
• Figure 9 illustrates the relationship between a plurality of photoconductive sensing elements and a plurality of course diverters for a nonspinning projectile.
• the guidance seeker system of the invention is described with particular emphasis on projected munitions whereby the projectile includes an explosive charge that is intended to detonate either on contact with a target or proximate to the target thereby disabling or destroying that target
• the guidance seeker system is equally applicable to nondestructive applications where it is desirable to direct a projectile to a desired target.
• One method of identifying a target referred to as semi-active target designation, illuminates the target with an external light source. This is referred to as "designating" the target and the light source referred to as the "designator.”
• a guidance seeker system onboard a projectile locates the illuminated target and directs the projectile to that target.
• a highly focused coherent beam of light such as a beam generated by a laser, is particularly useful for target designation.
• the laser to generate short duration pulses at a relatively slow repetition rate.
• an exemplary pulse duration 10 is between about 15 nanoseconds and 100 nanoseconds.
• the pulse spacing 12 is from about 0.033 seconds to about 0.05 seconds, generating between about 20 and 30 pulses per second (i.e. a pulse frequency of between 20 Hertz and 30 Hertz).
• the laser pulses may be coded as illustrated in Figure 2. While the pulse duration 10 remains substantially constant, the pulse spacing 12 1 is varied according to a pre-set code.
• the guidance seeker may contain a logic circuit programmed to recognize and respond to the pre-set code and to ignore designator signals not corresponding to that code.
• Any laser capable of generating pulses meeting the above requirements may be utilized.
• One preferred laser is a neodymium/YAG (yttrium, aluminum, garnet) laser.
• the laser 14 is preferably mounted on a platform other than the projectile.
• the laser 14 may be mounted on a helicopter or spotting aircraft.
• the laser 14 generates a pulsed beam 16 that is reflected from a target 18.
• a reflected pulse 20 is collected by lens 22 and transmitted onto at least one of a plurality of photoconductive sensing elements 24 contained within a photodetector 26.
• the photoconductive sensing elements 24 are preferably symmetrically disposed about a central axis 28 of the photo detector 26.
• the central axis 28 is aligned with the line of flight of the projectile, such that if the line of flight is aligned with the line of the reflected pulse, the reflected pulse strikes the central axis and does not strike any one of the photoconductive sensing elements thereby indicating that no course correction is required.
• reflected pulse 20 strikes at least one photoconductive sensing element. Illumination of the photoconductive sensing element 24 generates an electric pulse that effects a projectile course correction.
• a suitable photodetector typically includes at least four photoconductive sensing elements 24 and may include up to about 20 symmetrically arranged about the central axis 28.
• a metal casing such as a TO-39 case, not shown, supports the photodetector 26 and functions as a common cathode.
• Each of the photoconductive sensing elements 24 has its own anode.
• the photoconductive sensing elements are typically non-conductive, but become electrically conductive when irradiated with a laser pulse.
• the voltage transmitted through a photoconductive sensing element when irradiated is a function of light intensity and generally ranges up to about 1.2 volts.
• FIG. 5 is a perspective, and partially broken, view of a projectile 32 employing the guidance seeker system of the present invention.
• the projectile 32 is generally symmetrically disposed about a central axis 34 that also constitutes the line of flight of the projectile.
• the projectile 32 is expelled from a gun barrel, mortar, cannon, or other suitable means with an aerodynamically shaped forward end 36 leading the projectile in flight.
• the projectile has a metallic housing 38 that contains an explosive, a detonator, and an optics package 40.
• the optics package 40 is mounted at the forward end 36 of the projectile.
• Mounted on an exterior surface of the metallic housing 38 are a plurality of course correctors 42.
• the course correctors are a plurality of diverter elements 44 encircling the center of gravity of the projectile 32.
• Each diverter is a small, on the order of one gram charge, explosive that when detonated creates an impulse that nudges the projectile to change the line of flight to one more likely to impact the target.
• from detonation of one diverter until the projectile is ready for a second course correction is on the order of 0.100 seconds.
• An exemplary number of diverters for a 69.85 mm (2.75 inch) rocket is from about
• the photodetector 26 is mounted rearward, relative to the forward end 36, of the lens 22 such that lens 22 is disposed between the target and the photo-detector 26.
• a distance, D, between the lens 22 and photodetector 26 may be equal to the focal length of that lens, for a focused beam embodiment or may be a distance other than the focal length for a defocused beam.
• a typical focal length for lenses utilized with the optics package of the invention is one centimeter. Utilizing the lens equations:
• do distance to object
• d, distance to image from lens axis
• Output signals from the photoconductive elements mounted on photodetector 26 are pre-amplified and conditioned by electronics package 46 and then applied to the appropriate filing circuit associated with a desired diverter 44. Wires 48 may be utilized to transmit the output signal to the appropriate firing circuit.
• the projectile 32 may be either a spinning projectile or a non-spinning projectile. If a spinning projectile, the rate of spin is typically on the order of 1000 revolutions per second.
• output signals 50 from the photoconductive sensing elements 24, are typically voltage pulses having a voltage on the order of millivolts.
• the output signals 50 are passed through an amplifier 52 where the signal is pre-amplified and conditioned to 100 millivolts.
• a recirculating shift register 54 is clocked to a frequency, f, that is a multiple of the spin frequency of the projectile.
• a multiplication factor, n is equal to the number of photoconductive sensing elements in the ring.
• Shift register 54 transmits the conditioned output signal 50 1 via an appropriate firing circuit to the diverter 44 aligned with an irradiated photoconductive sensing element 24. Generation of the firing pulse and activation of the diverter occurs almost instantaneously and is effective to nudge the projectile to a line of flight closer to the target. It is anticipated that the next laser impacting the photodetector will strike closer to central axis 28.
• a single nudging of the projectile may not be effective to align the projectile with the target, or the target may be moving such that additional course corrections are required.
• Irradiation of another photoconductive sensing element 24 ' is effective to actuate another diverter 44 1 to again nudge the projectile in the appropriate direction.
• photoconductive sensing element 24 will be irradiated a second time.
• Diverter 44 has already been fired and is now inactive. In that event, or if diverter 44 has been deemed defective, the shift register delays transmission of amplified signal 52 for a time equal to f/n whereby next available diverter 44 1 ' has rotated to the original position of diverter 44.
• This step can be repeated if the neighboring diverter element is also spent until a live element is encountered.
• the shift register 54 thus accomplishes electronic derotation of the frame of reference assuring that steering impulses are always directed properly.
• a focused designator beam applies a high intensity of light to a single photoconductive sensing element generating a high voltage pulse from that element.
• D it is desirable that D not equal the focal length of lens 22.
• photoconductive sensing elements 24 are irradiated with a defocused beam 56.
• Defocused beam 56 is sufficiently large to irradiate a plurality of photoconductive sensing elements 24.
• the voltage passed through each of photoconductive sensing elements 24 is proportional to the intensity of the irradiating beam and the larger the surface area of a specific photoconductive sensing element irradiated, the larger the voltage output from that photoconductive sensing element.
• both the divergence, D, of the projectile from the target axis and the angle of rotation, R, between the projectile and the target may be determined.
• Knowledge of the angle of rotation is useful because it specifies the direction of the divert impulse.

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Fluid Mechanics (AREA)
• Electromagnetism (AREA)
• Aiming, Guidance, Guns With A Light Source, Armor, Camouflage, And Targets (AREA)
• Optical Radar Systems And Details Thereof (AREA)

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• 2000
  • 2000-07-20 WO PCT/US2000/019925 patent/WO2001016547A2/en active IP Right Grant
  • 2000-07-20 EP EP00986176A patent/EP1196733B1/de not_active Expired - Lifetime
  • 2000-07-20 DE DE60023007T patent/DE60023007T2/de not_active Expired - Fee Related
  • 2000-07-20 AU AU22458/01A patent/AU2245801A/en not_active Abandoned

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