GB1561670A

GB1561670A - Devices for tracking and calculating antiaircraft fire

Info

Publication number: GB1561670A
Application number: GB52490/76A
Authority: GB
Original assignee: GALILEO SpA OFF; Officine Galileo SpA
Current assignee: GALILEO SpA OFF; Officine Galileo SpA
Priority date: 1976-06-01
Filing date: 1976-12-16
Publication date: 1980-02-27
Also published as: FR2353822B1; IT1070381B; DE2658683A1; DE2658683C2; FR2353822A1; NO764237L; CH612498A5; SE7614067L; NO147157C; BE853081A; NO147157B

Abstract

The device comprises a series of aligned diodes, and an optical block for the formation on an aiming screen of a luminous reproduction in terms of value and direction, of the cursor (M-T), of which one end constantly coincides with the trace (T) of the firing line; the module of the said cursor, and its direction, which is obtained by rotating a plate which supports the diodes, are provided by a computer which receives evaluated data, and data supplied by the aiming device. The aiming device then maintains the target such that it coincides with the other end (M) of the cursor. <IMAGE>

Description

(54) IMPROVEMENTS IN OR RELATING TO DEVICES FOR TRACKING AND CALCULATING ANTI-AIRCRAFT FIRE (71) We, OFFICINE GALILEO S.p.A., an Italian Body Corporate of Foro Bonaparte 31, Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a fire control system for a gun, such as an anti-aircraft gun.

The basic problem when aiming at moving targets, in particular aircraft, is that of computing the lead angle and advancing the firing line by this angle vis-a-vis the line of sight. When firing, it is thus necessary to give up the parallelism between line of sight and gun axis, i.e. the firing line. The gun aimer continuously keeps the line of sight locked onto the target, while the firing line must be moved forward by an angle which at every moment varies depending upon the target distance and apparent speed thereof.

According to the present invention, there is provided a fire control system for use with a gun, comprising means for forming on a tracking screen a luminous line representing the lead angle in size and direction, with one end being constantly coincident with the scan of the firing line and with the data of the lead angle being supplied by data processing means which receives data supplied by tracking effected by keeping the target in coincidence with the other end of said luminous line, said means for forming said luminous line comprising a series of aligned light sources a different number of said sources being illuminated as a function of the size of the lead angle starting from an origin coincident with the scan of the firing line to produce a luminous line having a length which represents the size of the lead angle, the light sources being carried by support means which rotates around said origin as a function of the direction of the lead angle whereby the angular direction of the luminous line represents the direction of lead angle and optical means for projecting the image of the luminous line onto the tracking screen with a collimation to infinity.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 illustrates the gun aimer's field of sight; Figures 2 and 3 show, in perspective and in section, an optical block combined with a sighting device in a fire control system in accordance with the invention; Figure 4 is a front elevation showing a device for producing a luminous line- which represents the lead angle; Figure 5 is a section on line V-V of Figure 4; Figure 6 is an elevation of an angularly movable support structure which carries the device of Figure 4; Figure 7 is a section taken on line VII VII of Figure 6; and Figure 8 shows the fire control system mounted on the gun.

The lead angle can be represented as a vector which joins the line of sight from the gun aimer to the target with the firing line (see Figure 1). This vector can be represented in the gun aimer's sight field in the form of a line TM with a variable length (which represents the lead angle) and an orientation coincident with the instantaneous direction of motion of the target, i.e.

the "apparent course" angle, usually measured with respect to the horizon, as indicated by reference 8 in Figure 1. The line will thus rotate around the centre of the sight field (point T) which in its turn coincides with the gun firing line.

The system to be described provides a visual representation of the aforesaid vector in the form of a luminous line appearing in the sight field of an appropriate sighting device whose optical axis is always kept aligned with the gun barrel, one end of the vector being fixed and coincident with the point T which represents the firing line, while the other end M instantaneously coincides with the target, i.e. the line of sight.

Accordingly, if the gun aimer tracks the target in such a manner as always to keep it coincident with the end M, the firing line T will precede the line of sight M exactly by the lead angle.

The system includes data processing means in the form of a computer which continuously processes in real time the instantaneous value of the lead angle and displays it as a luminous line controlled in length and orientation. The computer carries out its calculations in accordance with the instantaneous tracking data, i.e. the angular speed of the gun in traverse and elevation and its angle of elevation, and also in accordance with estimated data relating to the target course fed into the computer by the aimer before tracking starts. The calculation is developed mostly by postulating that the motion of the target is rectilinear and of uniform speed.

The sighting device used is preferably of the reflex type and includes a semi-reflecting surface on which the image of the lead angle, in the form of a luminous line, is reflected and through which the gun aimer can view directly the target without enlargement or restriction in size. As shown in Figures 2 and 3, the reflex sighting device includes two blocks 3 and 5 of optical glass suitably shaped and glued together along a metallized surface 7 which forms the semireflecting plane. An end face SA of the composite block thus obtained is part-spherical and metallized in such a manner as to form a part-spherical mirror facing internally of the block. The end face 3A opposite the part-spherical face 5A is curved to compensate for the aberrations of the partspherical mirror. The image of the lead angle arrives through the face 3A.As shown in particular in Figure 3, the image of the rectilinear luminous line arriving as indicated by the arrow fl is seen by the righthand eye D of the aimer together with the background, in which the possible target may appear. The left-hand eye S, which merely views the background, permits the total sight range V to be viewed and this is almost equivalent to that which can be viewed with free, direct vision.

The mirror 5A acts like a collimator in relation to the luminous source, whose rays are thus seen by the eye as coming from infinity, exactly like the rays coming from the target appearing in the sight range.

The composite sighting block 3, 5, including the device generating the rectilinear line, is mounted (see Figure 8) on a support 9 resting adjustably on an arm 11A of a rotary supporting casing 11, which follows exactly the elevation angle of the gun B, besides following its horizontal movements.

The luminous line which represents the lead angle in the sight range of the sighting device, is formed by a semi-conductor device carried by an angularly movable support structure. It includes a series of (for example approximately sixty or more) gallium arsenide light emitting diodes (LED), indicated at 14 and arranged in a straight line in side-by-side relation so as to form a luminous line constituted by a series of luminous points. The luminous points may be energized, i.e. illuminated, separately one from another, through conductors 15A and 15Y in such a manner as to produce a luminous line having a variable length starting from an origin point represented by a diode 14A which is always illuminated and represents the firing line, i.e. the point T of Figure 1.The individual diodes are preferably spaced from one another by about 0.5 mm and the entire assembly of diodes has a length of approximately 30 mm. The light emitting diodes 14 are of the high brilliancy type and may be red, which ensures a good chromatic contrast relative to the sky. The diodes 14 are arranged diagonally under a transparent display 16 forming part of a sealed casing 18.

The semi-conductor device is mounted on a disc-like support structure 20 which can be angularly oriented according to the apparent course of the target. The display 16 is arranged in such a manner that the diode 1 4A always corresponds to the firing line.

The number of diodes 14 instantaneously energized is such as to cause the length of the line to correspond with the lead angle.

That diode 14B, located instantaneously at the other end of the luminous line represents the point to be made coincident with the target, i.e. the line of sight. The focal length of the mirror SA is chosen so as to present the luminous line to the gun aimer in its totality, at an apparent angle of approximately 16 degrees. This amplitude in fact corresponds to the maximum lead angle which is likely to occur with aircraft having speeds of up to 350 metreslsecond when flying an attack run. The disc-like support structure 20 is in the form of a printed circuit and is rotated by a computing servomechanism in accordance with the apparent angle of the target course, i.e. the angle 8 of Figure 1. The diode 14A is located in the centre of rotation of the structure 20.

There is thus obtained a luminous line which is controlled in length through progressive energization of the luminous diodes, to represent the lead angle. This line is also oriented according to the apparent course angle by pivoting around the point T, i.e. the diode 14A, according to the apparent course of the target, this line coinciding with the correct orientation of the lead angle. The gun aimer thus has merely to keep the end M of the luminous line formed on the display, i.e. the point formed by the diode 14B, on the target.

The computer receives as inputs, values or magnitudes introduced in the form of voltages, which are characteristic of the motion of the target, in particular, the linear speed of the target, the nodal distance or cross range (as hereinafter defined), the instantaneous angular speeds of the firing line in traverse and elevation, and the angle of elevation of the firing line.

The linear speed of the target is estimated by the gun aimer and introduced at the start of the tracking. Usually he will select the closest one of five or six predetermined speeds included between 150 and 350 metres/second.

The nodal distance or cross range is the minimum distance which is determined during the flight which is assumed to be rectilinear and uniform, between the target and the tracking station. Also for this magnitude, the gun aimer usually selects the closest one of five or six predetermined values included between 300 and 800 metres. It is to be noted that these estimates are facilitated by the fact that the gun will usually be located for the defence of a particular target and that the aircraft will have to follow certain more or less predetermined attack courses.

The two estimated values are introduced into the computer in the form of D.C. voltages selected with simple switches.

Besides the two estimated values, the computer receives, again in the form of D.C.

voltages, data relating to the two angular speeds of the firing line; the data relating to the angle of elevation of the firing line is, however, introduced in a mechanical form, i.e. as an angle of rotation.

With this input data, two fixed and three variable during the tracking, the electronic computer which is of the analog digital type, processes continuously and in real time sup plies two output values, viz the size of the lead angle and its direction. The first is supplied as electrical data which controls a number of diodes to be energized starting from the diode at the origin; the lead angle direction is on the contrary a mechanical output, i.e. an angular rotation (angle 6) of the means which moves the support structure 20. The computer effects a conventional kinematic-ballistic calculation.

The first control system described is especially suitable for use with rapid-firing machine guns having calibers ranging from 20 to 30 millimetres equipped with followup links or servomotors designed to control as to speed, the motion of the gun in both traverse and elevation. With these guns, the gun aimer, while sitting in a seat which moves with the gun, uses a control stick with two degrees of freedom to control the tracking direction and velocity.

WHAT WE CLAIM IS:- 1. A fire control system for use with tracking screen a luminous line representing the lead angle in size and direction, with one end being constantly coincident with the a gun, comprising means for forming on a scan of the firing line and with the data of the lead angle being supplied by data processing means which receives data supplied by tracking effected by keeping the target in coincidence with the other end of said luminous line, said means for forming said luminous line comprising a series of aligned light sources, a different number of said sources being illuminated as a function of the size of the lead angle starting from an origin coincident with the scan of the firing line to produce a luminous line having a length which represents the size of the lead angle, the light sources being carried by support means which rotates around said origin as a function of the direction of the lead angle whereby the angular direction of the luminous line represents the direction of lead angle, and optical means for projecting the image of the luminous line onto the tracking screen with a collimation to infinity.

2. A system as claimed in claim 1, wherein the luminous sources comprise light emitting diodes.

3. A system as claimed in claim 1 or claim 2, wherein said optical means comprise a reflex type optical block, with an inclined semi-reflecting surface and a partspherical collimation surface.

4. A system as claimed in any one of the preceding claims, wherein the data processing means receives estimated fixed data such as linear speed of the target and nodal distance, and variable data provided during tracking, such as the angular speeds of the firing line in traverse and elevation and the elevation angle thereof, and said data processing means supplies as an output the lead angle in digital form as the number of energised light sources, and the direction of the lead angle as an angular rotation of said support means.

5. A first control system substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. keep the end M of the luminous line formed on the display, i.e. the point formed by the diode 14B, on the target. The computer receives as inputs, values or magnitudes introduced in the form of voltages, which are characteristic of the motion of the target, in particular, the linear speed of the target, the nodal distance or cross range (as hereinafter defined), the instantaneous angular speeds of the firing line in traverse and elevation, and the angle of elevation of the firing line. The linear speed of the target is estimated by the gun aimer and introduced at the start of the tracking. Usually he will select the closest one of five or six predetermined speeds included between 150 and 350 metres/second. The nodal distance or cross range is the minimum distance which is determined during the flight which is assumed to be rectilinear and uniform, between the target and the tracking station. Also for this magnitude, the gun aimer usually selects the closest one of five or six predetermined values included between 300 and 800 metres. It is to be noted that these estimates are facilitated by the fact that the gun will usually be located for the defence of a particular target and that the aircraft will have to follow certain more or less predetermined attack courses. The two estimated values are introduced into the computer in the form of D.C. voltages selected with simple switches. Besides the two estimated values, the computer receives, again in the form of D.C. voltages, data relating to the two angular speeds of the firing line; the data relating to the angle of elevation of the firing line is, however, introduced in a mechanical form, i.e. as an angle of rotation. With this input data, two fixed and three variable during the tracking, the electronic computer which is of the analog digital type, processes continuously and in real time sup plies two output values, viz the size of the lead angle and its direction. The first is supplied as electrical data which controls a number of diodes to be energized starting from the diode at the origin; the lead angle direction is on the contrary a mechanical output, i.e. an angular rotation (angle 6) of the means which moves the support structure 20. The computer effects a conventional kinematic-ballistic calculation. The first control system described is especially suitable for use with rapid-firing machine guns having calibers ranging from 20 to 30 millimetres equipped with followup links or servomotors designed to control as to speed, the motion of the gun in both traverse and elevation. With these guns, the gun aimer, while sitting in a seat which moves with the gun, uses a control stick with two degrees of freedom to control the tracking direction and velocity. WHAT WE CLAIM IS:-

1. A fire control system for use with tracking screen a luminous line representing the lead angle in size and direction, with one end being constantly coincident with the a gun, comprising means for forming on a scan of the firing line and with the data of the lead angle being supplied by data processing means which receives data supplied by tracking effected by keeping the target in coincidence with the other end of said luminous line, said means for forming said luminous line comprising a series of aligned light sources, a different number of said sources being illuminated as a function of the size of the lead angle starting from an origin coincident with the scan of the firing line to produce a luminous line having a length which represents the size of the lead angle, the light sources being carried by support means which rotates around said origin as a function of the direction of the lead angle whereby the angular direction of the luminous line represents the direction of lead angle, and optical means for projecting the image of the luminous line onto the tracking screen with a collimation to infinity.