US2879502A - Collison course fire control system - Google Patents

Description

March 24, 1959 E. E. MILLER I 2,379,502

COLLISION COURSE FIRE CONTROL SYSTEM Filed Jan. e, 1946 2 Sheets-Sheeti l2 Vt E AE:FF RKD A F i m lk ANTENNA INDICATOR iflfltfi' GENERATOR 74 76 1 I '77 f f I 7 GYRQ PRECESS a CQMPUTOR i R, vc At A v NETIC MATERIAL 32 30 FIG. 3 37 3| INVENTOR EDWARD E. MILLER v33 BY W ATTORNEY March 24,1959 E. E. MILLER COLLISION COURSE FIRE CONTROL SYSTEM Filed Jan. 8, 1946 2 Sheets-Sheet 2 FIG. 45

FIG. 4A

FIG. 4D I VOLTAGE OUTPUT AZIMUTH E TOC CLY EE T TV ENOW DE INVENTOR EDWARD E. MILLER ATTORNEY COLLISION COURSE FIRE CONTROL SYSTEM Edward E. Miller, Medford, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application January 8, 1946, Serial No. 639,896 7 Claims. (Cl. 343-7) This invention relates to projectile laying systems and more specifically to the type for laying a projectile, such as a torpedo, at a moving target from a moving craft, such as a PT-boat.

A common firing technique and the one concerned in this invention is that employing the collision course principle, wherein the attacking craft places itself on such a course that, should the target and attacking vessels continue on their respective courses and maintain their velocities, the two vessels would collide. The collision course principle is employed because it ofiers to the attacking vessel the necessary velocity and azimuth heading information of the target vessel and because the collision course condition is one that is easily recognized.

Heretofore an attacking vessel got on a collision course by'making a series of estimated course corrections, but this technique is time consuming requiring a long tracking time for a given degree of accuracy. The present invention describes a system which can place an attacking vessel on a collision course with a single correction in .the' azimuth heading of the attacking craft. The system can be adapted to both radar and visual tracking of the target vessel.

A specific object of this invention is to provide apparatus for rapidly and accurately laying a projectile at a moving target from a moving craft.

Another object is to place an attacking craft on a collision course with a target vessel by means of a single adjustment in the azimuth heading of the attacking craft.

'Another object is to provide projectile laying apparatus whose operation is totally independent of the pitch, roll, or yaw of the vessel on which it is mounted.

Another object is to provide projectile laying apparatus having incorporated therein means for indicating when two coaxial and abutting, mechanically independent shafts are in proper alignment.

Another object is to provide a projectile laying system.

having incorporated therein means for providing a stabilized azimuth marker on a radar indicator scope.

A further object is to provide a projectile laying apparatus having incorporated therein a simple computer for turning one shaft by an amount mathematically related to the motion of a second shaft.

A further object is to provide a projectile laying system which may be operated from either radar or optical data.

Another object is to provide a radar projectile laying system which is operative with either a stabilized or an unstabilized tracking indicator. 7

To achieve these and other objects, apparatus is employed'which is described in detail in the following specification and shown in the accompanying figures, of which:

Fig.1 is an illustration of the collision course principle and the manner in which the present invention is adapted to this firing technique;

'Fig. 2 is a block diagram of the system of the present,

invention;

Fig. 3 is a perspective drawing showing schematically v The approximation improves as the angle Act diminishes, and AB corrections of greater precision can be made ifthe correlation between the radar, the azimuth marker,

and the gyro of the present invention;

Fig. 4A is a graph of the detected output of the azimuth marker of the present invention;

Fig. 4B shows a plan position indicator, or P.P.I., with the azimuth reference lines placed thereon; Fig. 4C is a'circuit which may be employed to produce the azimuth reference lines shown in Fig. 4B.

Fig. 4D shows the waveform of the output of the cirwill of Fig. 4C.

Fig. 5 shows the resistance network computer associated with the gyro-precess means and the ship steering mechanism.

In the accompanying drawings and more specifically in Fig. 1 are shown an attacking craft 11 moving with a constant velocity C and a target vessel 12 traveling at a constant velocity V initially displaced from one another In a time At, the attacking craft 11' travels to a position 13, and the target vessel 12 moves up to a position 14. From the figure it can be seen that by a range R the two vessels shown are not on a collision course and that the attacking vessel 11 will fall astern of the target vessel 12. The condition which indicates to the attacking vessel 11 that the two vessels 11 and'l2 are not on af collision course is that the original relative azimuth angle 1 '0 changes in a time At by an angular amount Act. If the two vessels 11 and 12 were on a collision course, the

relative azimuth angle 0 would remain unchanged as the two vessels approach one another.

To get on the proper collision course at the time |t=At the attacking vessel 11 must alter its course by an angle A 8, and the present invention is based upon the fact that 1 A 8 is determined from the known quantities, range R interval. At, and the easily 5 measurable angle Au. These quantities are related by the velocity V and time approximate mathematical expression V At necessary during the course of attack.

Considering the use of a search radar system with a plan position indicator for giving position information of the target vessel 12, initial range R can be measured' directly on the indicator presentation 15 of Fig. 1. The

knowledge of own velocity V is obvious,and the time interval At may conveniently be chosen as the time for an integral number of complete rotations of the radar antenna. The angle Act can be measured if an azimuth reference line is maintained. Such an azimuth reference is provided by a gyro which is initially uncaged with its axis pointing directly at the target vessel and which presents on the radar azimuth indicator 15 a stable azimuth marker con--- sisting of two adjacent radial lines 19. The oscilloscope radar presentation 15 of Fig. lshows the initial tracking condition with the radar echo 17 at a range R bracketed by the two radial lines 19 of the gyro stable azimuth marker. Indicator picture 16 at a time t=At shows Au as the easily measurableangle between the center line 20 of the stable azimuth markers 19 and the radar echo 18. To solve for the azimuth heading correction angle A3 which is ultimately desired, the gyro originally mentioned is precessed sothat the stable azimuth marker line 20 controlled thereby is brought into azimuth alignment with= By so processing the the radar echo 18 at time t=At. gyro,-the rotation axis thereof is again pointeddirectly computer comes the angle At? which may either go to a helmsman indicator on the attacking vessel or serve to turn the attacking craft directly.

After turning the attacking craft 11 through an angle AB, the attacking and target vessels 11 and 12lie on relative courses which will cause them to collide at point 21. An indication that the two are on collision course is that the new relative azimuth angle 11: remains constant as the two vessels approach one another. This condition is indicated on indicator picture 22 by the successive radar echoes of the target vessel falling within the stable azimuth marker of that indicator. It will be noticed that the indicator shown in Fig. 1 is unstabilized, with the top of the scope representing dead ahead.

Before the two vessels 11 and 12 reach the collision point 21, the attacking craft 11, which in the particular situation considered is making a torpedo attack, swerves in'toward the targetvessel by an angle determinedby the relative velocity of the torpedo and the attacking vessel 11, and releases its projectile 23. The final point of impact of the torpedo with the target vessel is indicated by point 24. The apparatus brought into use after the attacking and target vessels are on a collision course is not a part of the present invention.

'Refer now to Fig. 2 which is a block diagram. A search radar system 70 is employed having an antenna 71 that is sufficiently directive to provide accurate azimuth information and an indicator 72 for presenting both range and azimuth information. Thegyro 73 shown, having an associated precess mechanism 74, provides the desired stabilized reference azimuth information. Both the antenna 71 and one of the gyro supporting frames or gimbals are coupled to an azimuth marker generator 75. It is the latter. unit which places the-aforementioned stable azimuth lines on the radar indicator 72. A computer 76 has its operation dependent on R V At, and A0: in-

-- formation and solves for the azimuth heading correction angle At? which is finally transmitted to the shipsstecring mechanism 77. The arrows on Fig. 2 indicate the direction of flow of information.

Refer now to Fig. 3, which shows schematically the correlation between the radar, the gyro, the azimuth marker generator and the deck of the ship itself. A radar system having an antenna 25 rotatable about the axis AA of shaft 26 is shown with its beam pattern having a.plane of maximum radiation intensity which contains axis AA. Mounted also on shaft 26 or synchro-coupled thereto is the U-shaped bar 29 which is made of magnetic material and which lies in the first plane defined.

A gyroscope having a rotor 30 is mounted on two supports or gimbals 31 and 32, the outer gimbal 32 being mounted on the deck plane 33 of the ship and being rotatable about an axis AA which is perpendicular to the 'deck plane 33. The gyro thus has complete freedom of motion, allowing the rotor axis B--B to be positioned as desired. Rigidly attached to the outer gimbal 32 of thegyro is magnetic coupling bar 34 which is so located that the end of the first coupling bar 29 can sweep closely by and form a closed magnetic loop or circuit without any friction forces being transmitted by the driven bar 29 to upset the gyro alignment. Primary and secondary coils 35 and 36 are wound on coupling bar 29, and it can be seen that with an alternating signal on the primary winding 35, a maximum output signal will appear at the secondary winding 36 when the magnetic bars 29 and 34 are in such rotational alignment that they form a closed magnetic circuit. It is this output signal that is employed to produce the stable azimuth marker on the radar indicator, as will later be discussed.

It should be emphasized that Fig. 3 is' a schematic representation of apparatus of this invention. In an actual system, all of the components may not conveniently line up on a single reference axis AA, but this fact does not cause operation of the actual system to deviate appreciably from that of the simplified one shown in Fig. 3.

Supporting member 37 also does not actually exist, but represents all of the rigid structure on the ship which holds the various components and their associated parts in alignment.

One of the most important features of the system of this invention is that the coincidence between the gyro stable azimuth marker and the target vessel echo on the radar indicator is entirely independent of any roll, pitch or yaw of the attacking vessel. This aspect of the invention can be shown in terms of the structure of the Fig. 3.

The reference axis AA, which is perpendicular to the deck plane 33, and the gyro axis B--B define a first plane which is perpendicular to the deck plane and which contains the magnetic bar 34. A second plane is defined by the axis AA and the radar beam central radiation axis C-C. This plane, also perpendicular to the deck plane, contains a plane of maximum radiation intensity of the radar and the magnetic bar 29. By the related action of magnetic bars 34 and 29, an azimuth marker is placed on the radar P.P.l. scope when these two planes coincide.

In operation, the target by pointing gyro axis the first plane is made to initially contain B-B directly at the target. For a collision course, it is necessary that the target remains at the same relative azimuth bearing with respect to the attacking craft as the two vessels close. Thus, if the attacking craft is on collision course, the gyro axis B-B continues to point at the target and the first plane contains the target no matter how much the attacking vessel pitches, rolls, or yaws. Under this..circumstance, the second plane passes through thelfirst plane and the target simultaneously and the target radar. echo remains centered on the P.P.I. azimuth marker regardless of how much the marker swings on the radar indicator due to the attacking ships instability. Should the attacking vessel be ofi its collision course, however, the relative azimuth bearing of the target will shift and the first plane will no longer contain the target. As a result, the second plane will coincide with the first either before or after the second plane passes through the target, and the radar echoes and the azimuth marker will not be coincident on the indicator.

Another way to analyze this stabilization scheme is to consider that the gyro axis B--B and the radar axis 0-0 are both projected perpendicularly down onto the deck plane. It is these deck projections that are referred to the indicators by the antenna synchro and the magnetic coupling bar. By so referring both the 8-8 and C--C axes to the same reference plane, motion of this plane does not affect the relation between the two projected axes.

The manner in which the double line, stable azimuth marker is formed by the output signal of the magnetic coupling structure previously described is shown in Figs. 4A, 4B, 4C and 4D. Fig. 4A shows the detected envelope 40 of the alternating signal which is produced on the secondary coupling winding 36 of Fig. 3 as the two magnetic coupling bars 29 and 34 of that figure sweep past and couple with one another. From this envelope, it is desired to produce two pulses, symmetrically related to the peak of the curve, which may be used to intensify the radar indicator beam. On the P.P.I. cathode ray indicator, as illustrated in Fig. 4B, two radial lines 45 and 46 are formed and these are symmetrically disposed about an axis 47 which corresponds to the center line 43 of Fig. 4A.

One of a number of circuits which may be used for producing two intensifier pulses at points 41 and 42 of the curve of Fig. 4A is shown in Fig. 4C. The detected prising resistors 52 stages 50 and 51.

far he'yond'cut off" '(biasing means not shown), 's'tartsto conduct when its grid voltage rises to the value 54 of Fig. 4A. Stage 51 is quiescently held in saturation by As'the result of this action, the output voltage has a sharp rise 56.

Stage 51 finally cuts oli, with the conduction of stage" 50 still increasing, and theoutput voltage'falls (57) to the level 58 where stage 50 is finally saturated. The circuit of Fig. 4C has 'thus been flipped over, producing a large voltage pulse 59 at the point 41 of Fig. 4A. A similar pulse 60 is produced at the point 42 of Fig. 4A- as the input voltage to stage 50 falls to its initial value. After inverting and clipping the wave of Fig. 4D at some level 61, the two resulting pulses are placed directly on the intensifier grid of the radar indicator cathode ray tube (P.P.I.) Any number of other types of circuits may be adapted by those skilled in the art to perform-this pulse generating function.

Referring now to Fig. 5, the computer for solving the relation between the azimuth deviation angle Au and the azimuth heading correction angle for collision course AB is shown. This apparatus comprises a AOL gyroprecess means 74'having an input resistance R and adapted to precess the gyro of the system at a rate proportional to the voltage which said precess means receives, a constant speed, rapid start-stop, reversing motor 79 which directs AB information to the turning mechanism of the attacking craft, and a control. box 76 having included'therein a switch for operating the A motor 79 in either direction and for operating the gyroprecess means 74, and a resistive network for controlling the voltage,vand thus the rate of precession, of the Au gyrm recess-mechanism 74.

As previously discussed, the equation which relates Ag? and Act is Since Ae is introduced by a constant rate device (motor 79);. and AG by a variable rate device (gyro-precess means 74), and since the same switch is used for on and off control of both rate devices, the relation between the Ace angle of rotation A5 and the angle of precess Am can: be controlled entirely by adjustment of the variable gyro-..

led to a fictitious +12 voltage point. As a result, resistors 65, 66 and 67 can be effectively placed across a +12 or 12 volt supply by switch 63.

Computation is done by the hand set taps on resistors 66, 67 and by variable resistor 68, and to correlate adjustment of these with the computation which they perform, it must be noted that increasing the control voltage to the A0: gyro-precess means 74, increases the rate of precess thereof and thus decreases the angle Afi generated by the constant speed motor 79. Thus increasing the I operation is based on However, it will be obvioust'o those; skilled in the art that the technique involved might easily be adapted to claim is: p

- 1. Apparatus for laying a projectile at a moving tar- R tap on resistor '67 decreasesg'yro-pre'cess rate, while? increasing the At tap on resistor 66 causes an increase in gyro-precess rate. This is all in keeping with the above equation. Velocity V is introduced to the resis tive network by control of the magnitude R of resistance 68. The R and At resistance controls are linear, while the introduction of V by resistance R; is determined by the equation 1 R4=T/:R3 R being the input resistance of the gyro-precess circuit. The apparatus of the present invention has been described with respect to a projectile laying system Whose the collision course principle.

other types of fire control or navigation and with other than seacraft. Since radar replaces optical systems when darkness, fog, smoke, etc. 'make the latter inoperative, it will be obvious that an optical tracking'meansmightv well be'used under-circumstances favorable thereto in-' stead of the radar described above. The scope of this invention should further be interpreted to encompass the "use of combined optical and radar systems with'one serving as a check upon the-other. Furthermore the simple technique of fully stabilizing the tracking apparame of the present invention against ships pitch, roll, and

yaw is adaptable to any number of other types of systerns requiring similar stabilization. g

The invention described in the foregoing specification need not be limited to the details shown, whichare considered to 'be illustrativeofone form the invention may take. What I desire to secure by Letters Patent and get from a moving craft; said apparatus comprising a radio echo detection and ranging system including a rotary scanning antenna and a range-azimuth indicator, aj gyro, precess means for causing said gyro to precess,

means mechanically coupled to said antenna and said gyro for producing a stable azimuth marker on said indicator, acornputer, said computer-being coupled to said precess means for controlling the rate at which said gyro -pre'cesses, and constant speed reversible motor means controlled by said computer for determining an azimuth heading correction angle mathematically related to a' gy o precess angle. i 21 Apparatus r laying a projectile at a moving target from a moving craft, said apparatus comprising a radioecho detecting and ranging system including a rotary scanning antenna and a' range-azimuth indicator, a gyro having precess means associated therewith, a computer coupled to said precess means for controlling the rate at which said gyro is causedto precess, constantspeed reversible motor means controlled by said computer for determining an azimuth heading correction angle mathematically related to ,agyro precess angle, and means for producing a stable azimuth marker on said indicator, said marker producingmeans including mag netic coupling bars mounted on 'two shafts respectively representing the azimuthal position of the antenna and the rotor of said gyro, said bars being so shaped that they communicate with one another without touching'to form an essentially closed magnetic circuit when said antenna and gyro rotor are in a predetermined azimuthal relationship means for inducing a magnetic field in said bars, and a signal coil associated with one of said bars for conveying an output signal to said indicator.

3. In a fire control system of the type wherein an attacking craft maneuvers to close on a moving target along a collision course, the combination of a radio .pulse echo detecting and ranging system carried by said nave-mos 1 search pulses and receives echo pulses reflected from ire-- mote target anda synchronized plan position indicator for displaying the azimuthandrange of targets so detected, I

means for producing on the face'of said plan position indicator a pair'of angularly dis'posed, illuminated-radial traces during eachcycle of rotation of said directional 1 I antenna, said radial traces defining a sector on said, plan position indicator Which delineates a predetermined I search area covered by said system, means forinitially I locating said sector so that it is centrallydisposedabout the representation on the plan position indicator of the.

tating directional "antenna: which periodically radiates, search pulses and receives echo pulsesreflected from ,re-t

mote targets, and a synchronized plan position indicator directional antenna, said radial traces defining a sector; on said planposition indicator which delineates a predetermined search area covered by said systemmeans- 1 for initially adjusting the time of occurrence of said space I I azimuth bearing-of said moving target, means operative I tion through which'said sector shifts.

targets and a synhcronized planposition indicator for displaying the azimuth and range of targets so detected,

a-generator for producing a pair of spaced pulses during each cycle of rotation ofsaid directionalantenna, means for supplying said spaced pulses to the intensity control electrode of said plaiifposition indicator whereby apair,

of angular'ly' disposed radial traces are produced on the face of said plan position indicator,said radialtraces de- I fining a sector on said. indicator which corresponds to a predetermined amount of search area, means for initially setting the time of occurrenceof said space pulses where I by said sector is symmetrically disposed about a first azi:

i inuth bearing on said plan position indicator of said moving targegand means for varying at a given time later, the time of occurrence of said pair of pulses so that said I I a' predetermined time later. for shifting the location of said 'sectorsothatit 'isagain'centrally' disposed about the. representation of the azimuth bearing of said movingtarget, and means ,for correcting the steering of said at, ,tacking'craft in accordance withthe'amount and direc- I 7 motor for driving the steering mechanism of the attacksector progressively shifts its location until it reaches a position on said .plan position indicator at which it again is symmetrically disposed about a second azimuth bearing of said moving target, the angular distance through which said sector shifts providing a measure of the amount of steering correction that is needed to bring said attacking craft on a collision course to said moving target.

5. In a firev control system of the type wherein an atfor displaying the azimuth and, range of'targetsso de-- 'tected, means for producing on; the face of said plan I position indicator a pair of angularly disposed, illuminated radial "traces duringeach cycle of rotation of said pnl'sesduring each cycle of rotation of said directional antenna so that said sector is symmetricallydisposed aboutthe azimuth bearing on said planposition indicatorof said moving target, and'means vfor subsequently varying the time of occurrence of saidpairsof. pulses during successive cycles of rotation of said directional an-' I I tenna until said sector shifts to a'position at which it again is symmetrically disposed about the ,latest azimuth bearing' of said moving target, the angular distance/through I L which said sectorshifts identifying theazimuthheading correction angle for the collision course.

I '6. In a system as defined in claim 5, means for regulating the rate, atwhich said means for changing the time of occurrence of. said pairs of pulses functions, whereby the time required to shift the position of said sector: is controllable.v I

7. In a system as defined in claim 5, a constant speed ing craft, and meanstor' energizing said motor for a length of time'equal to that required for said selector v to shift its position and in a direction corresponding to I that 'in whichsaid sector moves on said plan position indicator.

I I j References Cited in the'file of thispatent I 1 UNITED STATES ,PATBNTSI 2,369,622

*Toulon Feb. 13,. 1945 I 2,420,016 1 Sanders May 6, 1947 2,420,017 "Sanders May 6, 1947 2,422,697 Meacham June 24, 1947 2,434,813 Sanders Jan; 20, 1948 2,437,286 Witt Mar. 9, 1948 2,447,728 Bartholy Aug. 24, 1948 2,472,129 Streeter June 7, 1949 2,476,746 Libman July'19, 1949 2,488,448 Townes Nov. 15, 1949 2,510,129 Moore June 26, 1950 2,521,726 Ivall Sept. 12, 1950 A 2,547,363 Bishop Apr. 3, 1951 2,552,172 Hawes May 8, 1951 t

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