Patent GB-1113106-A (GB)
Title: Anti-aircraft sighting device
IPC: G01S13/66
Filed: 1965-05-20
Abstract: 1,113,106. Radar sighting computer. BOFORS A.B. 20 May, 1965 [3 June, 1964], No. 21441/65. Heading G4G. A radar antenna A (Fig. 1), pivoted on a stand 2 on a horizontal rotary platform 1 tracks a target M, and is laid in elevation by D.C. controlled servomotor SH and in azimuth by D.C. controlled servomotor SS. The antenna is excited by transmitter/ receiver R incorporating a range measuring unit driven by D.C. controlled servomotor SA, and signals # s , # h , # a  represent deviations of azimuth elevation, and range from the target. Signal # s  controls servomotor SS through adder 4, signal # h  controls servomotor SH through adder 5, and signal # a  controls servomotor SA through adder 6 to track the target, while tachogenerators T 1 , T 2 , T 3  produce corresponding rate of rotation signals which are connected to the adder circuits of the respective servomotors. To compensate for insufficiently rapid response of the servomotors in tracking a target passing close to the system at high speed, there is provided an electric analogue computer K supplied with azimuth SV and elevation angles hv, and the range Al of the target as measured by the radar, over mechanical linkages from the servomotors, and also the azimuth velocity SV, the elevation velocity #hv and the range velocity Al as electrical signals from the servo-control circuits of the radar to control other servomotors of the computer; which calculates from the data supplied the azimuth acceleration SV, the elevational acceleration #hv, and the range acceleration #Al of the target with respect to the radar site, assuming that the target is moving on a straight course with variable velocity. Signals proportional to these variables are applied through integrators I 1 , I 2 , I 3  together with corresponding error signals # s , # h , # a  from the radar to control the respective servo systems through adders 4, 5, 6, so that the radar follows the target with high accuracy. It is shown mathematically that (Figs. 2, 3, 4, not shown) and the computer K (Fig. 5) comprises a reference A.C. source 7 energizing potentiometer P 1  responsive to range Al which excites series potentiometers P 2 , P 3  responsive to SV and cos (hv) respectively to develop a voltage representing Al s#v cos (hv). The output of P 1  also energizes potentiometer P 4  responsive to h#v whose output is proportional to Al.h#v and applied to an input of resolver R 1  rotated by angle hv of the target. The resolver also receives the output of potentiometer P 5  responsive to A#l, and the resolver output represents A#l cos hv - Al h#v sin hv, which is connected together with that of P 3  to a unit 8 producing an output representing the square root of the sum of the squares of the inputs, to represent Fh by a direct voltage according to (4), which is applied to adder 9 controlling servomotor F driving potentiometer P 6  producing a voltage Fh from reference D.C. source 10 which is fed back to the adder and also supplied to a differentiating circuit 11 producing a voltage representing F#h also fed back to the adder, and applied through A.C. modulator M, to potentiometer P 7  driven by the servomotor to produce an A.C. voltage representing F#h/Fh. A potentiometer P 8  responsive to 1/Al  is energized by a voltage representing Al from potentiometer P 5  to produce a voltage representing A#l/Al, and a potentiometer P 9  responsive to h#v whose output voltage is applied to series potentiometers P 10 , P 11  multiplying by the sine and reciprocal cosine of hv, so that the combined output represents h#v tan (hv). This voltage and the output voltage of P 8  are multiplied by + 2, - 2 respectively and combined in adder 12 with the output voltage ofpotentiometer P 7 . The resultant voltage is connected to potentiometer P 12  responsive to S#V; to produce an alternating voltage representing #S#V (equation 1), which is demodulated at D 1  to produce a direct voltage representing #S#V. Squaring potentiometer P 13  responsive to s#v produces a voltage representing (s#v)<SP>2</SP> applied to cosine potentiometer responsive to hv, whose output is applied to sine potentiometer P 15  responsive to hv, to produce an output representing s#v<SP>2</SP> sin hv cos hv, and adder circuit 13 receives a voltage representing F#h/Fh from potentiometer P 7  to the output of potentiometer, P 8  x(- 2) to produce a voltage representing F#h/Fh-2Al/Al , which is multiplied by h#v in potentiometer P 16  and combined in adding circuit 14 with the output of potentiometer P 15  x(- 1) to produce a voltage representing #h#v according to equation (2), which is demodulated at D 2  to a corresponding direct voltage. Potentiometer P 17  responsive to A#l receives the voltage representing Fh/Fh from potentiometer P 7 , and potentiometer P 18  respective to A#l receives the voltage representing h#v from potentiometer P 9 . A further cosine potentiometer P 19  responsive to hv receives the output from potentiometer P 14  representing cos hv, and its output is combined with that of P 18 in adding circuit P 15 , whose output is connected to potentiometer 20 responsive to Al, and the resultant output representing Al[(sv cos hv)<SP>2</SP> + hv<SP>2</SP>] is combined with that of potentiometer P 17  representing #Fh/Fh A#l in adding circuit 6 to produce a voltage representing #A#l which is demodulated at D 3  to a corresponding direct voltage. The direct voltages representing #Al, #hv, #sv are connected to the appropriate points in the control circuits of servomotors SA, SH, SS (Fig. 1). Other forms of computer K may be employed.