US2356830A

US2356830A - Fire control computer

Info

Publication number: US2356830A
Application number: US467339A
Authority: US
Inventors: George A Crowther
Original assignee: Ford Instrument Co Inc
Current assignee: Ford Instrument Co Inc
Priority date: 1941-02-11
Filing date: 1942-11-30
Publication date: 1944-08-29
Anticipated expiration: 1961-08-29

Description

' Aug. 29, 1944.

G. A. cRowTl-IER FIRE CONTROL COMPUTER Original Filed Feb. 11, 1941 2 Sheets-Sheet l RHS INVENTOR Georqe. Ulwwhmf- A TTORNE Y @EMM m Aug. 29, 1944.

235. BEGlSTEBS.

Patented Aug. 29, 1944 @Smidt UUE FIRE CONTROL COMPUTER George A. Crowther, Manhasset, N. Y., assigner to Ford Instrument Company, Inc., Long Island City, N. Y., a corporation of New York Original application February 11, 1941, Serial No.

378,367. Divided and this application November 30, 1942, Serial No. 467,339

Claims.

, This application is a division of application Serial No. 378,367, iiled February 11, 1941.

'I'his invention relates to gun-re control computers and particularly to that type of computers used to control the ring of guns against aircraft.

The problem of the control of gun-fire against aircraft may be divided into two classes; (1) Where the aircraft or target is approaching directly towards its objective or the point of observation and the firing gun, and (2) where the target is passing at a distance to one side or the other of the observing and ring point. The invention herein disclosed is applied to the first mentioned class. that some of the principles thereof are applicable to the solution of problems of the second mentioned class.

In considering the solution of the problem of anti-aircraft lire control to which this inventionI is applied as one embodiment thereof, it is assumed that the target is directly approaching its objective, which is the point of observation and the point of ring of the gun, at a substantially constant height above the horizontal plane of the objective, such as would be done in horizontal-bombing of a selected point. Upon the picking up of the target by observers at the objective, the direct or slant range of the target and its elevation above the horizontal, expressed in angular units, are observed by instruments well known in the art and from the observed data the height of the target and the horizontal range may be determined, or if the height of the target is known or obtained by observations and the elevation is observed, the slant range and the horizontal range may be determined.

From experimental data obtained during target practices, the most eiective ranges of the guns are known as well as the time in seconds required to set and adjust the sights and the fuses of the projectiles and to load and re the projectiles. In this specification, the time re- .quired to set the observed values into the mechanisms, for the mechanisms to calculate the advance range or fuse setting and the sight angle, and the time required to adjust the sight and gun and load and fire the gun is defined as the preparation period of time. This preparation period is arbitrarily selected and is based upon experience under various circumstances of operation.

The object of the invention is to provide a mechanism settable in accordance with an observed range or height and elevation angle of It will of course be understood an approaching aircraft target and settable in accordance with the speed of the target and the selected preparation period of time following the instant of the observations, for computing the sight angle or difference in elevation of the gun and the line of sight at the instant of iiring and the time-setting values of the fuses of the fired projectiles.

Mechanisms for accomplishing the objects of the invention and their operation will be understood by considering the following description and accompanying drawings in which:

Fig. 1 is an elevation side view of an aircraft target directly approaching an observing and ring point at a constant height and showing the consecutive angular and linear relations of the target to the observing and firing point; and

Fig. 2 is a diagrammatic View of a mechanism to compute the values required in the control of the lire of the gun.

Referring particularly to Fig. 1, an aircraft or target I is directly approaching the observing and ring point O at a constant height (H) above the horizontal O-O' and at a horizontal speed of St.

When the target I reaches point A, observers at O observe the direct or slant range (R) and the elevation angle of the target (A1), from which the height (H) and the horizontal range (RH) may be calculated by the equations resulting from the right angle triangle OAA of H=R sin AI and RH=R cos AI, respectively. A is the projection of the point A on the horizontal 0---0 The preparation period of time (X) is selected as required and multiplied by the speed of the target (St) to give the distance traveled by the target during the time (X) represented by the length of line AB, thus defining the point B at which the target I will be at the end of the preparation period. The value of the distance AB may be expressed by the equation The horizontal range of target I at point B (RHS) is equal to the observed horizontal range minus the distance AB or From the right angle triangle OBB', the elevation of the target when at point B (A3) will be the angle whose tangent is the height divided by the horizontal range to the point B, or

From ballistic tables or curves obtained from experimental data the time of flight (t) of projectiles is known for various combinations of horizontal ranges and heights. As is well known the time of ight (t) is the period of time between the instant of firing of the projectile and the instant of its intercepting the target. The travel of the target during this period of time is equal to the speed of the target multiplied by the time of flight or t'St, and is indicated on Fig. 1 by the line BC, or l This distance determines the point of `intercept (C) and a perpendicular dropped from C determines the point C'. It is obvious that OC represents the horizontal range to the point of intercept (RH2) and that The elevation angle of the point of intercept (A2) is obtained from the right angle triangle OCC and is the angle whose tangent is the height divided by the horizontal range to the point of intercept (RH2) or H A2-tan 1RH2 (6) The elevation of the gun above the line of sight to the point B, to allow for the movement of the target during the time of flight is known as vertical angular deflection (Ut) and may be ex- Dressed as Ut=A2-A3 (7) It is obvious that the distance AC is equal to (X-l-t) St and that Also from ballistic tables and curves obtained from experimental data the correction in elevation, known as super elevation (e) that must be applied to `compensate for the shape of the trajectory of the projectile, is known for various combinations of horizontal ranges and heights. The total elevation of the gun above the line of sight is known as sight angle (Us) and may be expressed as The mechanism required for the mechanical solution of the problem as set forth in detail hereinbefore is connected as a closed or regenerative system, that is, one section of the mechanism modifies or partially controls the movement of a second section, and the output of the second section is combined in or partially controls the movement of a third section and the output movement of the third section is connected back to affect or modify the movement of the first or second section. Such mechanisms as a system are stable and operable,`when the movement thus connected back to modify the input to a preceding section is only a small part of the total input to that section and therefore has a much reduced effect on the output of the section which is connected back.

Referring particularly to Fig. 2, the vector inputs of the vector analyzer or component solver 2 are the observed direct range (R) set in by handle 3 and shaft 4 and the observed elevation of the target (A1) from the point of observation (O) set in by handle 5 and shaft 6. The set in values of R and A1 are made visually available by dials 'I and 8 geared to shafts 4 and 6, respectively. The outputs of component solver 2 are shafts 9a and I D, the rotational positions of which represent height (H) and horizontal range (RH), respectively. Shaft 9a is connected to shaft 9 through differential 9b the third side of which is shaft 9c to which is geared zero reader dial 9d.

Shaft 9 is moved by handle 9e to set the value of height into the rest of the mechanism, by bringing the zero reader dial 9d to its zero position by the connection of shaft 9 to the differential 9b. The value of height (H) set into'the mechanism is indicated by the dial 91 geared to shaft 9. If height is known, instead of range, the height is set in by handle 9e and dial 9i to the observed value. Any displacement of the zero reader dial is removed by operating the range handle 3 to bring the zero reader dial back `to zero. This will introduce a value of range (R) corresponding to the value of elevation A1 and height (H) set into the mechanism.

The inputs of the conventional multiplier I2 are the estimated speed of the target (St) setV in by handle I3 and shaft I4 and the sum of the preparation time (X) and the time of flight (t). The value of X is set in by handle I5, shaft I6, differential I1 and shaft I8. The set in value of X is made visually available by dial I9 geared to shaft I6. The set in value of St is made Visually available by dial I4a geared to shaft I4. The generation of the value of the time of flight (t) represented by the rotation of shaft 20 will be described hereinafter.

The output of multiplier I2, (X -I-t) St, is transmitted by shaft 2| to differential 22 where it is combined with the motion of shaft I0 representing horizontal range (RH). 'I'he output of differential 22, RH-(X-i-T) St or RH2 (see Equation 8) is transmitted by shaft 23 to a conventional three-dimensional cam unit, or which the other input is shaft 9 representing height (H). Cam 24 of this unit consists of a solid rotated by the shaft 23 representing horizontal range (RH2). The surfaces of the various lateral cross-sections of the solid along its axis form a cam surface to give to cam follower 25 a motion proportional to the time of flight of the projectile for the range represented by the rotational position of the cam andthe value of height represented by the axial position of the follower 25. The cam follower 25 is positioned parallel to the axis of the cam 24 to engage the various lateral sections of the solid cam in accordance with the value of height (H) as represented by rotational position of the threaded portion of shaft 9, which engages the threaded carriage on which follower 25 is mounted for rotational movement. Cam follOWer 25 is kept in engagement with the cam surface by spring 26 and its motion is transmitted to elongated gear 21 on shaft 20 by the toothed sector 28 to which follower 25 is secured. Shaft 20 is connected to differential I1 to introduce time of flight into multiplier I2 as previously described.

Shaft 23 representing horizontal range (RH2) is also connected as one input to position one of the component slides of a conventional vector solver 29. The input for positioning the other component slide of the Vector solver is shaft 9 representing height (H). The output of vector solver 29 is shaft 30, which is driven by the vector gear, the rotational position of which represents the angle of the point of intercept (A2), as shown by Equation (6). The vector gear is provided with a radial slot in which is slidably mounted a pin 29a which projects through slots in the component slides. The radial position of the pin 29a Z631 tltiii l trib.

and the angular position of the vector gear are determined by the intersection of the component slides.

The inputs of the conventional multiplier 3| are shaft I4 representing target speed (St) and shaft 20 representing time of flight. The output of multiplier' 3| is shaft 32 the rotational position of which represents t-St. The motion of shaft 32 is combined with that of shaft 23 rep-f resenting horizontal range (RH2) by differential 33 and the output of differential 33, shaft 34, is connected to vector solver 35 as one input thereto, the other input being shaft 9 representing height. The output of vector solver 35 is shaft 36, the rotational position of which represents the value of the elevation angle of the point of firing (A3). The value of A2 minus A3 is obtained by connecting shafts 30 and 36 to differential 31, the output of which is shaft 38. The rotational position of shaft 38 represents Ut (see Equation '1).

The value of the super elevation (e) is obtained by the three dimensional cam 39, which is similar in construction and operation to cam 24, except the surface of cam 39 is such that the radial positions of the cam follower 4|) relative to shaft 23 represent super elevation (e). The position of the cam follower 40 and the associated toothed sector controls the rotational position of the elongated gear 4| in accordance with the value of the super elevation (e) corresponding to the values of horizontal range and height represented by shafts 23 and 9 respectively.

The motion of shaft 42 which is driven by elongated gear 4| is combined with that of shaft 38 by differential 43, the output of which, shaft 44, represents the sight angle (Us). The sight angle is made visually available by dial 45 geared to shaft 46 which is connected to shaft 44 by differential 41. Arbitrary corrections in sight angle may be applied to shaft 46 by shaft 48 which is connected to differential 41, the other input of which is shaft 44. Shaft 48 is moved by handle 49. The Values of the corrections are made visually available by dial 58 geared to shaft 48.

As the fuses of the projectiles are set in accordance with the time of flight (t), shaft 20 is connected to graduated dial 5l by differential 52 and shaft 53. The other input to differential 52, shaft 54, is provided to apply arbitrary corrections to dial 5|. Shaft 54 is moved by handle 55. The values of the corrections are made visually available by dial 56 geared to shaft 54.

It has been found that the deflection due to the drift of a projectile is substantially proportional to the super elevation (e) of the gun relative to the line of sight. Therefore dial 51, suitably calibrated from experimental data to give values of drift for corresponding values of super elevation, is connected to shaft 42 by shaft 58 through .g

differential 59. Corrections in deflection may be added by moving handle 60 on shaft 6| which is connected to the third side of differential 59. The value of the corrections in deection is vmade visually available by dial 62 geared to shaft It is obvious that various changes may be made by those skilled in the art in the selections of mechanisms and mode of operation within the scope of the following claims.

I claim:

1. A closed system fire control computer, for a gun firing at a target approaching at a constant height above a horizontal plane, comprising a vector analyzer including a settable vector member representative of the direct range and elevation angle of the target position at an observing instant and component members movable to positions representative of the horizontal range and height components of the target position, a multiplier settable in accordance with the sum of a selected preparation period of time and the period of the time of flight of the projectile and the speed of the target for positioning an output in accordance with the change in horizontal range during the combined preparation and flight periods, a second multiplier settable in accordance with the flight period and the speed of the target for positioning an output in accordance with the change in horizontal range of the target during the period of time of flight of the projectile, means for combining the movements of the outputs of said multipliers and the movement of the horizontal range member for moving a pair of elements in accordance with the horizontal ranges of the target at the end of the respective periods, a pair of vector means settable by the movements of the respective elements and the height member of the vector analyzer for determining the angles of elevation of the target at the end of the respective periods, means for combining the outputs of said pair of vector means for determining the vertical angular deflection, and ballistic computing means settable in accordance with the position of the element representing the horizontal range of the target at the end of the flight period and in accordance with the height member for determining the super elevation of the gun and the flight period, and means operably connecting the output of the ballistic computing means representing the flight period to the input members of the said multipliers settable in accordance with the period of time of flight of the projectile.

2. A closed system fire control computer, for a gun firing at a targetapproaching at a constant height above a horizontal plane, comprising a vector analyzer including a settable vector member representative of the direct range and elevation angle of the target position at an observing instant, a first component slide movable to a position representative of the horizontal range component of the target position and a second componentslide movable to a position representative of the height component of the target position, means settable in accordance with a selected preparation period of time, means movable in accordance with a computed period of time of flight of the projectile, a rst differential for combining the movements of the preparation period means and the ight period means, a first multiplier connected to the output of the first differential means and also settablein accordance with the speed of the target. a second differential for combining the output of the first multiplier and the movement of the first component slide, a first ballistic computing means settable by the said second component slide and the output of the second differential for determining the flight period, means connecting the output of the first ballistic means to the flight period movable means, a second multiplier settable by the flight period movable means and in accordance with the speed of the target, a third differential for combining the output of the second multiplier and the output of the second differential, a first vector means settable by the output of the third differential and the movement of the said second component slide, a second vector means settable by the output of the second differential and the movement of the said second component slide, a fourth differential for combining the outputs of the first and second vector means for obtaining the vertical angular deflection, a second ballistic computing means settable by the said second component slide and the output of the second differential for determining the super elevation of the gun, and a fifth differential for combining the outputs of the fourth differential and the second ballistic means whereby the output of the ilfth differential represents the desired elevation angle between the gun and the sight.

'3. A closed system fire control computer, for a gun firing at a target approaching at a, constant `height above a horizontal plane, comprising a vector analyzer including a settable vector member representative of the direct range and elevation angle of the target position at an observing instant and component members movable to positions representative of the horizontal range and height components of the target position, a multiplier settable in accordance with the sum of a selected preparation period of time and the period of the time of flight of the projectile and the speed ofthe target for positioning an output in accordance with the change in horizontal range during the combined preparation and flight peri- 4 ods, a second multiplier settable in accordance with the flight period and the speed of the target for positioning an output in accordance with the change in horizontal range of the target during the period'of time of flight of the'projectile, means for combining the movements of the outputs of said multipliers and the movement of the horizontal range member for moving a pair of elements in accordance with the horizontal ranges of the target at the end of the respective periods, a pair of vector means settable by the movements of the respective elements and the height member of the vector analyzer for determining the angles of elevation of the target at the end of the respective periods, means for combining the outputs of said pair of vector means for determining the vertical angular deflection,

ballistic computing means settable in accordance with the position of the element representing the horizontal range of the target at the end of the flight period and in accordance with the height member for determining the flight period, and means operably connecting the output of the ballistic computing means representing the flight period to the input members of the said multipliers settable in accordance with the period of time of flight of the projectile.

4. A closed system re control computer, for a gun firing at a target approaching at a constant height above a horizontal plane, comprising a vector analyzer including a settable vector member representative of the direct range and elevation angle of the target position at an observing instant and component members movable to positions representative of the horizontal range and height components of the target position, a multiplier settable in accordance with the sum of a selected preparation period of time and the period of the time of flight of the projectile and the speed of the target for positioning an output in accordance with the change in horizontal range during the combined preparation and flight periods, a secondmultiplier settable inaccordance with the ilight period and the speed of the target for positioning an output in accordance with the change in horizontal range of the target during the period of time of flight of the projectile, means for combining the movements of the outputs of said multipliers and the movement of the horizontal range member for moving a pair of elements in accordance with the horizontal ranges of the target at the end of the respective periods, a pair of vector means settable by the movements of the respective elements and the height member of the vector analyzer for detering the angles of elevation of the target at the end of the respective periods, means for combining the outputs of said pair of vector means for determining the vertical angular deflection, ballistic computing means settable in g accordance with the position of the element representing the horizontal range of the target at the end of the flight period and in accordance with the height member for determining the super elevation of the gun and the flight period, means operably connecting the output of the ballistic computing means representing the flight period to the input members of the said multipliers settable in accordance with the period of time of flight of the projectile, and means settable in accordance with the position of the output of the ballistic computing means representing the super elevation for determining the angle of drift of the projectile.

5. A closed system re control computer, for a gun firing at a target approaching at a constant height above a horizontal plane, comprising members movable to positions in accordance with the horizontal range and the height of the target, a multiplier settable in accordance with the sum of a selected preparation period of time and the period of the time of flight of the projectile and the speed of the target for positioning an output in accordance with the change in horizontal range during the combined preparation and flight periods, a second multiplier settable in accordance with the flight period and the speed Aof the target for positioning an output in accordance with the change in horizontal range of the target during the period of time of flight of the projectile, means for combining the movements of the outputs of said multipliers and the movement of the horizontal range member for moving a p air of elements in accordance with the horizontal ranges of the target at the end of the respective periods, a pair of vector means settable by the movements of the respective elements and the height member for determining the angles of elevation of the target at the end of the respective periods, means for combining the outputs of said pair of vector means for determining the vertical angulamdeggztion, ballistic computing means settable in accordance with the position of the element representing the horizontal rangengfwthe target at the end of the flight period andin accordance with the height member for determining the flight period.

GEORGE A. CROWTHER.