US3366346A - Remote missile command system - Google Patents

Description

Jan. 30, 1968 w. B. M KNIGHT ETAL 3,366,346

REMOTE MISSILE COMMAND SYSTEM Filed July 19, 1965 3 Sheets-Sheet 2 I I MISSILE MISSILE DETECTOR FM DYNAMICS TRACKING UNIT AMPLIFIER DEMODULATOR REFERENCE SIGNAL COMPARISON AMPLIFIER NETWORK 3| A IMITII NEL z CHAN BIAS COMMANO ERROR COOER TRANSt-ATOR /I IMITER ELEVATION CHANNEL R COMMAND ERROR CODER TRANSLATOR/ LIMITER I FIG. 2

AMPLITUDE I ERROR v 50 4O 3O 20 IO 0 IO 20 3o 40 5o ANGLEW'LS) 0.0 VOLTS FREQUENCY 6 -Wi||i m B. McKni hf LOnnIe N. McClus y Nicholas J. MOn us INVE TORS.

w. B. M KNIGHT ETAL REMOTE MISSILE COMMAND SYSTEM Jan. 30; 1968 3 Sheets-Sheet Filed July 19, 1965 Lonnie N. McClus y Nicholas J. Mongus INVENTORS.

BY W J, Wail United States Patent 3,366,346 REMGTE MISSILE EOM'MAND SYSTEM William B. McKnight, Somerville, Lonnie N. McClusky,

Torrey, and Nicholas J. l /iangus, Huntsville, Ala, as-

signors to the United States of America as represented by the Secretary of the Army Filed July 19, 1965, Ser. No. 473,572 3 Claims. (Cl. 244-311) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.

This invention relates generally to a system for guiding missiles to a target which has been acquired and sighted by visual or other means. More particularly the present invention relates to an infrared detector which senses the line-of-sight of a missile launched at a selected target, and provides signals indicating errors of the missile line-ofsight compared with its own line-of-sight. The line-ofsight of the detector is centered by an operator on the target, most likely a tank.

In the field of command guidance of air-to-ground or ground-to-ground missiles primarily for use against tanks, at number of problems are presented by a system of visual missile tracking. Manual operation of controls that guide self-propelled missiles to the target require a highly skilled, highly trained operator. Even so, the reflexes of a man are very often too slow to hit a moving target. Due to these slow reflexes, the missile used has to be a slow speed one. Further, the eyesight of a man, unaided, is insufiicient when the target is at a far distance. If he uses an optical device, he will have difiiculty in acquiring both the missile and the target in his field of view at the same time especially just after firing of the missile. If he tries to overcome this by using unaided eyesight at first to get the missile in line with the target and then switch to an optical device, there will be a time, when he is changing to the optical device and bringing it to sight on the missile that the missile is not under control. This is obviously undesirable.

It is therefore an object of this invention to provide a missile guidance system which requires a minimum of skill for the operator.

A further object of the present invention is to provide a guidance system in which the operator may at all times use an optical aid.

A still further object of the invention is to use an automatic infrared guidance system in combination with manual control to acheive high accuracy guidance.

In the field of command guidance of air-to-ground and ground-to-ground missiles which are primarily used against tanks, a number of improvements over manual missile tracking are provided by an infrared missile tracker which furnished error signals to the missile and maintains it on a direct line-of-sight. Infrared automatic command guidance allows the use of relatively high speed missiles, and overcomes the loss of missiles resulting from inadequate manual guidance. The use of this invention allows the unskilled operator to successfully hit the target, as the operator is only required to center an optical sight on the target and pull the trigger.

The invention further resides in and is characterized by various novel features of construction, combinations, and arrangements of parts which are pointed out with particularity in the claims annexed to and forming a part of this specification. Complete understanding of the invention and an introduction to other objects and features not specifically mentioned will be apparent to those skilled in the art to which it pertains when reference is made to the following detailed description of a specific embodiment thereof and read in conjunction with the appended drawing. The drawing, which forms a part of the specification,

presents the same reference characters to represent correspending and like parts throughout the drawing, and wherein:

FIGURE '1 shows a pictorial representation of the semiautomatic infrared command system according to the invention;

FIGURE 2 illustrates a system in block diagram in accordance to the invention;

FIGURE 3 is a graph of the relative control signal vs. the error angle or the target;

FIGURE 4 illustrates a cut away view of the missile tracking unit of the present invention showing only front lines;

FIGURE 5 shows the design of the reticle pattern used in this invention, and

FIGURE 6 illustrates the relationship of the input to the output of the FM demodulator wherein the abscissa is the input in frequency and the ordinate is the output in volts.

In order to better understand the operation of the system described in the figures a description of their components referred to is first presented. FIGURE 1, which is a pictorial representation of the semiautomatic system, shows a missile 1 in flight heading toward the target 3 which is a tank. An infrared source 4 (such as sodium flare) is attached to the missile. Missile is guided by signals from the command unit 5. The missile is shown to be a wire guided missile but may use any of the well known command guided missiles. Likewise, the output circuitry of the command unit may be the input of the well known command links. A launcher 7 is shown and may be of any desired design. More than one missile may be provided and there also may be more than one launcher.

The output and the fire circuitry of command unit 5 is controlled by the control assembly 9. The control assembly comprises a trigger 11 which controls the fire circuit, a missile tracking unit 13 which provides tracking signals, a telescope 15 which provides a means to sight, and a stock 17 which provides support for the assembly. Telescope 1S and unit 13 have their axes in alignment, insofar as sighting on a distant target is concerned.

In FIGURE 2 the missile tracking unit 13 is shown as having its output connected to an input of an infrared detector amplifier 21. The output of amplifier Z1 is connected to the input of the F M demodulator 23 whose output is one of the inputs of comparison network 25. The other input of network 25 is the reference signal amplifier 27. A scan drive power unit 29 is provided for unit 13.

Comparison net work 25 has control signal outputs 86 and 87 which are added with bias means 31 and 32 sent to the azimuth and elevation channels. The azimuth and elevation channels each contain an error translator limiter 34 and 3S and a command coder 37 and 38. The outputs of the command coders are coupled either by wire or wireless to the missile dynamics 40, for guiding the missile. FIGURE 3 shows the plot of the relative control signal output of the phase comparison network against the error in angle of the missile.

FIGURE 4 shows a cut away view of the missile tracking unit 13. This unit is a modified cassegrain optical system (folded telescope). A casing 43 encircles the components of the device. Infrared radiation from source Al on the missile enters the front of the device through correcting lens 45, reflects off the primary mirror 47 to the secondary mirror 49 and passes on to a reticle 51. The reticle is in the focal plane of mirror 49. The radiation energy passes through reticle 51, field lens 53, and lens 55' to an immersed IR detector 57. The output of detector 5'7 is connected to amplifier 21 by way of cable 66.

Secondary mirror 49 is mounted for rotation by the shaft 63 of the motor drive of unit 65. Mirror 49 is not mounted at a 90 angle with respect to shaft 63, but is skewed with respect thereto. Sun baffles 67 are black grooves cut in the structure to trap stray radiation, especially from the sun. Motor drive and reference signal generator 65 has a generator which is driven by the motor. Suitable optical filters may be provided at the front of casing 43 at/or in the correcting lens 45 for filtering out all the radiation except the infrared radiation to be detected.

FIGURE shows a reticle 51 for chopping the infrared energy which is focused thereon. Reticle 51 is a disc-like structure and may be of any desired configuration. A suitable form of the reticle of this invention comprises a plurality of alternate pie shaped opaque portions 70 and translucent portions 71, with respect to the radiant energy to be detectedin this case infrared energy. By translucent is meant the ability to transmit the waves of the radiant energy to be received. A quartz glass may be used for the reticle of this invention.

Operation The operator 75 (FIGURE 1) sights a target 3 and determines which missile can be fired so as to come in sight of the detector 13. He then sets the controls on command unit 5 so as to select the proper missile (only one missile is shown in FIGURE 1) and to provide any needed bias. Operator 75 now sights on the target through telescope 15, pulls the trigger 11, and continues to keep the target within the telescopes cross-hairs until the missile 1 impacts against the target. The operator now may select another target and repeat the operation.

After trigger 11 is depressed command unit 5 causes the selected missile to be launched, and its infrared source to start emitting. Infrared radiation emitted from the source on the selected missile enters detector 13 by Way of the correction lens 45. This radiation is reflected by primary mirror 47 to skewed mirror 49 and is focused onto reticle 51. It is passed through reticle 51 and a field lens 53 and is refocused to an immersed IR de tector 57. The rotation of the motor of unit 65 causes the image of a point in the field of view to describe a circle in the focal plane. The reticle is located in. this focal plane. The reticle, therefore, chops the infrared energy and causes IR detector 57 to have an alternating current output. If the image (this being the infrared source 4 which is affixed to the missile) is centered on the aixs of detector 13, the circle will be centered on the reticle and will cause an output of IR detector 57 which represents a carrier signal frequency. However, if the missile is off axis, the circle will no longer be centered on the reticle (see dotted circle 84 of FIGURE 5) and will cause a frequency deviation in the carrier signal.

The output of detector 57 is amplified by IR detector amplifier 21 (FIGURE 2) and then sent to FM demodulator 23 where, after demodulation and filtering, the frequency deviation of the carrier signal is represented by a signal output 82. The function of demodulator 23 is shown by FIGURE 6 wherein the abscissa is the input signal frequency and the ordinate is the output 82 of the demodulator. Signal output 82 is equal to the frequency of the reference signal generator output of unit 65 which is the r.p.s. of the mirror 49. It can easily be seen from FIGURES 5 and 6 that the phase of signal 82 will change with respect to the polar angle of the center of circle 84; therefore the polar angle, with respect to the axis of detector 13, of the missile can be equated to the phase of signal 82-. Once the phase of the reference signal with respect to the position of the mirror 49 is set, then a comparison network 25 can compare these two signals in phase and produce control signal outputs 86 and 87 which are proportioned so as to indicate the polar error angle in X and Y coordinates. The amplitude of signal 82, therefore, can be converted into control signals 86 and 87 with respect to the error angle function as shown in FIGURE 3. The reason the amplitude falls off after an angle error of more than 10 milsnot indicated by FIG- URE 6is that the circle 84 on the reticle will no longer encircle the center of the reticle at such an error angle. However, even if circle 84 made by the image does not inclose the center of the reticle, the phase of signal 82 will still give a true indication of the polar angle. This is because even if circle 84 were to be above center, the bottom of circle will still have the highest frequency and the top will still have the lowest. Since this usually happens only just after the launching of the missile, the missile has suflicient time, even with minimum guidance, to come into line with detector 13.

Comparison network 25 compares signal 82 with the reference signal 28 in both phase and amplitude and produces control signal outputs 86 and 87 representative of X-Y coordinates. Signal 86 indicates azimuth (left or right) information, and signal 87 indicates elevation information. These signals are sent to the azimuth channel and the elevation channel respectively. Biases 31 and 32 may be added to these signals to initially guide the missile to a position in the field of view of the detector 13. Bias 32 may also be used to compensate for the gravitation pull on the missile by adding a constant down error component to signal 87. The azimuth and elevation channels translate and limit their inputs into error position of the missile, and their command coders 37 and 38 code this information and send it on to the missile. In this specific embodiment a wire guided missile is shown and the coded signals would be sent along the wires 90 (FIGURE 1) to the missile 1. However any command guided missile may be used, such as electromagnetic radiation guided missiles. The missile dynamics 40 contains a control section which receives the outputs of coders 37 and 38 and converts it into guidance control for the guidance section of missile dynamics 40. The guidance section then causes the missile to fly into and to stay in the line of sight of the detector 13, and therefore, in the line of sight of telescope 15. This will, of course, send the missile to the target 3.

An embodiment of the invention which is preferred has been chosen for purposes of illustration and description only. The preferred embodiment illustrated is not intended to be exhaustive nor to limit the invention to the precise form disclosed. It is chosen and described in order to best explain the principles of the invention and their application in practical use to thereby enable others skilled in the art to best utilize the invention in various embodiments and modifications as are best adapted to the particular use contemplated. It will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention as set forth in the disclosure, and that in some cases certain features of the invention may sometimes be used to advantage without a corresponding use of other features. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. Accordingly, it is desired that the scope of the invention be limited only by the appended claims.

We claim:

1. A missile guidance system comprising a radiant energy detector unit having a reference axis; a missile having a radiant energy source and missile control means; said detector unit being so constructed as to detect the polar position and the azimuth and elevation coordinates of the radiant energy source with respect to said axis and to present at its output a carrier wave which is frequency modulated to represent the polar position of the missile; first means connected to said detector units output so as to have a signal output representative of said detected position; second means connected to an output of said first means so as to have error signal outputs representative of error polar position of the radiant source (and, therefore, the azimuth and elevation coordinates of the missile); third means having inputs connected to the outputs of said second means for transferring said error position to the control means of said missile, wherein said control means controls the guidance of the missile to bring the missile into line with the axis of the radiant energy detector; first and second bias source means; said first bias means being connected to an input of said third means so as to bias the azimuth coordinate; and said second bias means being connected to another input of said third means so to bias the elevation coordinate.

2. A guidance system as set forth in claim 1, wherein said second means comprises a demodulator connected to the output of the first means; a reference signal having a frequency output equal to the frequency output of said demodulator; a comparison network; and wherein said reference signal has a voltage and phase related to that of an output of said demodulator such that said comparison network-which has said reference signal and said output of the demodulator as its inputs-produces said coordinates outputs of said second means.

3. A guidance system as set forth in claim 2, further comprising a control assembly having a stock means; telescope means and said detector unit being connected to and aligned with said stock means; and said telescope having a sighting axis which is in substantial alignment with the reference axis of said detector unit.

References Cited RODNEY D. BENNETT, Primary Examiner.

BENJAMIN A. BORCHELT, SAMUEL FEINBERG,

Examiners. M. F. HUBLER, Assistant Examiner.

Claims (1)

1. A MISSILE GUIDANCE SYSTEM COMPRISING A RADIANT ENERGY DETECTOR UNIT HAVING A REFERENCE AXIS; A MISSILE HAVING A RADIANT ENERGY SOURCE AND MISSILE CONTROL MEANS; SAID DETECTOR UNIT BEING SO CONSTRUCTED AS TO DETECT THE POLAR POSITION AND THE AZIMUTH AND ELEVATION COORDINATES OF THE RADIANT ENERGY SOURCE WITH RESPECT TO SAID AXIS AND TO PRESENT AT ITS OUTPUT A CARRIER WAVE WHICH IS FREQUENCY MODULATED TO REPRESENT THE POLAR POSITION OF THE MISSILE; FIRST MEANS CONNECTED TO SAID DETECTOR UNIT''S OUTPUT SO AS TO HAVE A SIGNAL OUTPUT REPRESENTATIVE OF SAID DETECTED POSITION; SECOND MEANS CONNECTED TO AN OUTPUTS OF SAID FIRST MEANS SO AS TO HAVE ERROR SIGNAL OUTPUTS REPRESENTATIVE OF ERROR POLAR POSITION OF THE RADIANT SOURCE (AND, THEREFORE, THE AZIMUTH AND ELEVATION COORDINATES OF THE MISSILE); THIRD MEANS HAVING INPUTS CONNECTED TO THE OUTPUTS OF SAID SECOND MEANS FOR TRANSFERRING SAID ERROR POSITION TO THE CONTROL MEANS OF SAID MISSILE, WHEREIN SAID CONTROL MEANS CONTROLS THE GUIDANCE OF THE MISSILE TO BRING THE MISSILE INTO LINE WITH THE AXIS OF THE RADIANT ENERGY DETECTOR; FIRST AND SECOND BIAS SOURCE MEANS; SAID FIRST BIAS MEANS BEING CONNECTED TO AN INPUT OF SAID THIRD MEANS SO AS TO BIAS THE AZIMUTH COORDINATE; AND SAID SECOND BIAS MEANS BEING CONNECTED TO ANOTHER INPUT OF SAID THIRD MEANS SO TO BIAS THE ELEVATION COORDINATE.

Images