AN ARRANGEMENT FOR FIRE CONTROL

Abstract: The invention relates to a tracking radar (17) rigidly connected to the fire tube (11) of a gun and influencing the set motors (14) of the gun in order to, after locking onto a target, bring the radar axis and thereby the axis of the fire tube (11) to follow the target. According to the invention the tracking radar (17) is accommodated in a protection en­ velope (20) which is fixedly mounted on the elevation system (12) of the gun and which at the front end in the fire direction is closed by a radome (21). The protection envelope (20) and radome (21) are dimensioned so as to withstand the forces arising at fire, in particular toprevent the compression waves arising at fire to deform the antenna means of the radar (17), so that the radar will be effective with substantially main­ tained accuracy also during the fire.

Description: The invention relates to an arrangement for fire control of a gun (10) comprising a tracking radar unit (17) with radar transmitter/receiver and antenna means, mounted on the gun (10), so that the axis of the antenna means forms a given angle with the axis of the barrel (11), and producing control signals for the setting motors of the barrel (11) in order to, after locking on a target, bring the radar axis and thereby the axis of the barrel (11) to follow the target by influencing the said setting motors in a closed servo loop, the tracking radar unit (17) being encapsulated within a radar envelope. Such an arrangement is known from the brochure "BOFORS Air Defence Weapons, 40 mm all weather BOFI AA System". By mounting the tracking radar unit encapsulated within a radar envelope on the gun, an improved all-weather-capability at gun fire control is achieved. However, there is a mechanic influence on the radar at fire, caused by compression waves from the mouth of the barrel recoil and damping forces. This produces a mechanical environment with large accelerations within a wide frequency range. In this system, in which the tracking radar is included in the servo loop of the gun, this gun is directed to a predicted forward point in the firing moment. Then there is no requirement for simultaneous radar tracking and firing. This involves that the compression waves at fire do not influence the radar during the tracking phase. However, in certain applications it is a desire that it shall be possible to utilize the tracking radar also during fire. Under this condition it shall maintain high accuracy and large operation range. The radar shall furthermore have MTI-function and multi-target tracking. It is assumed that the barrel and the radar axis are parallel or have predictable static and dynamic deviations. Each such unknown deviation produces an error contribution from the radar. The error contribution of the radar can be described in the terms resolution and accuracy. With resolution is meant the ability of the radar to discriminate between two adjacent targets. The resolution ability is measured in lateral and in range. The lateral resolution is substantially the same as the lobe angle in the horizontal plane. The range resolution is a function of the pulse length. With accuracy is meant the ability of the radar to measure the position of a target. The accuracy can be better than the resolution. In other words, a target can be localized with errors, which are smaller than the lobe width and pulse length, respectively. The accuracy of a radar is to a large extent coupled to the radar antenna. A radar antenna which is deformed by compression waves produces an erroneous angular information. The determination of the position of the target will be erroneous. The object of the invention is to achieve an arrangement of the kind described in the opening paragraph, in which the tracking radar substantially maintains its accuracy under the mentioned difficult operation condition, so that it also functions during fire. According to the invention this is achieved thereby that the tracking radar unit (17) including its radar envelope is supported within a protecting envelope (20), which is rigidly mounted on the elevation system (12) of the gun (10), the tracking radar unit (17) and the protecting envelope (20) being connected together by resilient damping elements (24) at opposite surfaces of the protecting envelope (20) and the radar envelope with an internal spacing between the protecting envelope (20) and the radar envelope (17), which protecting envelope (20) at the front-end comprises a radome (26) and which protecting envelope (20) is dimensioned to withstand the forces arising at fire and in that the protecting envelope (20) has connections (32,33) for supply of cooling air or heating medium to the space between the protecting envelope and the radar envelope. Due to this construction the radar unit including its radar envelope is protected well by the protecting envelope. As a consequence of the envelopes being connected together by resilient damping elements, the transmission of mechanical loads and shocks from the gun barrel is avoided. Therefore this radar unit can also function during fire and simultaneous radar tracking and firing becomes possible for a gun with such a radar unit. Via the connections, the radome can be defrosted with a heating medium and the IR-radiation of the radar can be reduced by means of cooling air. According to another aspect of the invention, the protecting envelope exclusive of the radome and the radome are made of plastics material, preferably reinforced plastics material. This will result in a low total weight and thereby low strains on the fastening points on the gun. According to further aspects of the invention, the protecting envelope is coated by an IR-reflecting surface layer, and the protecting envelope has got a sectional shape conforming to a corner of the gun mount. With this shape of the protecting envelope, a higher mechanical rigidity of the envelope and possibility to a better fastening of the same will be achieved with a given mateial quantity and weight. The invention is illustrated by means of example with reference to the accompanying drawings, in which Fig. 1 and 2 show a simplified side view and a plan view, respectively, of an automatic gun with tracking radar mounted directly on the elevation system of the gun in according with the invention, Fig. 3 shows a sectional view through the tracking radar mounted in a protection envelope according to the invention and Fig. 4 shows a sectional view along the line A-A in Fig. 3. In Fig. 1 and 2 reference numberal 10 designates a gun tower, 11 is a fire tube and 12 an elevation part. The gun tower 10 is swingable in lateral direction about a vertical axis 13 and is adjusted about the said axis by means of a set motor, which is represented by the circle 14. The fire tube 11 and the part 12 are rigidly mounted together and form together the elevation system of the gun, which system is swingable about a horizontal axis 15. The elevation system is adjusted in height direction about the said axis 15 by bans of a set motor, which is represented by a circle 16. A tracking radar 17 is mounted directly on the elevation system of the gun, more closely on the elevation part 12, and contains radar transmitter/receiver and radar antenna and signal processing means. The axis of the radar antenna is suitably adjusted to be parallel with the axis of the fire tube. The tracking radar 17 generates control signals for the set motors 14 and 16, as indicated by the conductors 18 and 19, so that closed servo loops are formed in which, after locking onto a target, the radar axis and thereby the axis of the fire tube are kept directed towards the target. According to the invention the tracking radar 17 is mounted within a protection envelope or a cassette 20 which in turn is fixedly mounted on the elevation part 12 of the gun. At the front, i.e. in the fire direction, the cassette is closed by a radome 21. In the shown example the tracking radar 17 has a front part 17', where the radar antenna is situated, which has larger dimensions than the remainder 17'' of the tracking radar so that between the two parts is formed a shoulder 22. The cassette 20 is shaped in corresponding manner and consists of two parts 20', 20'' and an intermediate shoulder 23. After mounting of the tracking radar in the cassette the shoulder 22 on the radar bears against the shoulder 23 on the cassette so that the said last shoulder will form reference surface for the radar. The radar can be rigidly mounted within the cassette or, as in the shown example, fastened via a resilient damping element 24. At its open front end the cassette is terminated by a fastening flange 25 and the radome has a corresponding flange 26 adapted to be fastened to the said flange on the cassette. As is evident from Fig. 4 the cassette 20 with tracking radar 17 is mounted on a corner 27 of the elevation part 12 and is for this pulse shaped with an indentation consisting of two mutually perpendicular plane sides 28, 29 which are placed on the part 12 at the said corner 27. This shape of the cassette with an indentation will increase the mechanical rigidity of the cassette and will improve the possibilities to an effective fastening on the elevation system. In the side walls of the cassette there are two openings 30, 31 with connection tubes 32, 33 adapted to be connected to a source of cooling medium or heating medium. The cassette as wall as the radome may be made of plastics reinforced with Kevlar. In order to reduce the influence of sun irradiation on the radar the cassette can suitably be coated with an IR-reflecting layer. After mounting the radome on the cassette this cassette and radome will form a closed envelope. Through this envelope a cooling medium or heating medium can be brought to circulate by connecting the connection tubes to a source for cooling medium or heating medium. The circulation of a cooling medium can be used in order to decrease the IR-radiation and thereby to decrease the possibilities of discovery by means of IR-detectors. Circulation of a heating medium, e.g. heated air, can be used in order to prevent ice coating. The mounting is very simple. First the cassette is fastened rigidly on the outside of the elevation system be means of screws or in another manner. Thereafter the radar is introduced with its small end part through the open end of the cassette until the shoulder on the radar will bear against the shoulder on the cassette, possibly with intermediate damping element, and is screwed onto the cassette or fixed in another manner. Finally, the radome is placed at the open end of the cassette and the flanges on the cassette and radome are mounted together, e.g. by means of screws. Before mounting the radome on the cassette or after demounting of the radome the radar is easily available for adjustment relative to the fire tube so that the radar axis will be exactly parallel to the axis of the fire tube. For this purpose adjustment screws or the corresponding (not shows) may be present at the fastening place between tracking radar and cassette.

Claims: An arrangement for fire control of a gun (10) comprising a tracking radar unit (17) with radar transmitter/receiver and antenna means, mounted on the gun (10), so that the axis of the antenna means forms a given angle with the axis of the barrel (11), and producing control signals for the setting motors of the barrel (11) in order to, after locking on a target, bring the radar axis and thereby the axis of the barrel (11) to follow the target by influencing the said setting motors in a closed servo loop, the tracking radar unit (17) being encapsulated within a radar envelope, characterized in that the tracking radar unit (17) including its radar envelope is supported within a protecting envelope (20), which is rigidly mounted on the elevation system (12) of the gun (10), the tracking radar unit (17) and the protecting envelope (20) being connected together by resilient damping elements (24) at opposite surfaces of the protecting envelope (20) and the radar envelope with an internal spacing between the protecting envelope (20) and the radar envelope (17), which protecting envelope (20) at the front-end comprises a radome (26) and which protecting envelope (20) is dimensioned to withstand the forces arising at fire and in that the protecting envelope (20) has connections (32,33) for supply of cooling air or heating medium to the space between the protecting envelope and the radar envelope. An arrangement as claimed in Claim 1, characterized in that the protecting envelope (20) exclusive of the radome (26) is made of plastics material. An arrangement as claimed in Claim 1 or 2, characterized in that the radome (26) is made of plastics material. An arrangement as claimed in Claim 2 or 3, characterized in that the plastics material is reinforced plastics material. An arrangement as claimed in any of the Claims 1-4, characterized in that the protecting envelope (20) is coated by an IR-reflecting surface layer. An arrangement as claimed in any one of the Claims 1-5, characterized in that the protecting envelope (20) has got a sectional shape conforming to a corner of the gun mount (10).

Inventors: LARSSON, KLAS GOERAN INGEMAR, LINDHOLM, ROLF CHRISTER, STROEM, JOHAN PAUL, Larsson, Klas Göran Ingemar, Ström, Johan Paul
Applicants: BOFORS ELECTRONICS AB
Application year: 1985
Main classification: F41G5
IPC codes: F41G3, F41G5, G01S13, H01Q1