Patent GB-893387-A (GB)
Title: Improvements in or relating to analogue interception computers
Inventor: JOHNSTON JAMES STEWART
IPC: F41G7/30
Filed: 1960-03-17
Abstract: 893,387. Analogue interception computers. DECCA RECORD CO., Ltd. March 9, 1961 [March 17, 1960], No. 9567/60. Class 37. An interception computer determines, by means of a loop circuit the displacement AYI, OXI in a cartesian co-ordinate system of the inteception point K (Fig. 1) with respect to the initial interceptor position I and the displace- A ment ( AXT, YT) of K with respect to the initial target position. The effect of wind may also be taken into account (Fig. 2, not shown). The circuit of Fig. 3 determines the required interceptor course. D.C. signals corresponding to AXI, #YI are derived by the circuit (see below) and are fed to a unit 20 providing an output D.C. voltage corresponding to ##XI<SP>2> + #YI<SP>2>= #PI. OPI is divided by the interceptor speed and multiplied by the target speed to obtain #PT by an amplifier 21 having input and feedback resistors 22, 23 respectively of magnitudes corresponding to the interceptor and target speeds respectively. #PT is resolved into #YT, #XT in a sine cosine potentiometer PT the shaft of which is set in accordance with the bearing of the target. #YI, #XI are derived from summing amplifiers 25, 31 having inputs of #YT, YT, - YI and #XT, XT - XI (where XT, YT and YI, XI represent the initial target and interceptor positions respectively). #XI, #YI are then fed to the inputs of 20, through sign inverter 46, 50, if necessary, since 20 operates only in one quadrant, and may be shown on a meter to indicate the course. If the input date is such that no interception is possible one or more of the amplifiers will be saturated and operate a warning device. In another embodiment (Fig. 5, not shown) #XT and #YT are derived by computing the time taken for the interceptor to reach the inception point and multiplying this by the components of target speed by integrators producing linear sawtooth waveforms having slopes corresponding to the target speed components. Corrections for wind are added to #XI, #YI. In the embodiment shown in Fig. 6, XT, YT and XI, YI are derived by integrating XT, YT, XI, YI at 100, 101, 102, 103, and are added to #XT, #YT and to wind correction components to provide inputs to the modulus computing circuit which computes #PI. #PI is compared with a signal corresponding to interceptor displacement derived by integrating interceptor speed SI, in a comparator 120 which initiates a pulse when the inputs are equal, the pulse controlling staticizers 105, 106 in which XT, YT values are stored. The staticizers provide outputs corresponding to #XI, #YT, since the time interval between the initiation of operations and the production of the pulse corresponds to the time taken for the interceptor to reach the interception point from its initial position. The course to be flown is indicated on 131. Warning means is included if interception is not possible or if the total distance the interceptor has to travel exceeds a certain limit. The staticizers may also be removed from the loop. Fig. 4 shows a circuit for deriving the modulus of two inputs comprising an amplifier 40 including biased diodes in both its input circuits and its feed-back path. Specification 873,999 is referred to.