Patent GB-1016942-A (GB)
Title: Improvements in and relating to position predicting computers
IPC: G06G7/80
Filed: 1964-02-06
Abstract: 1,016,942. Electric analogue calculating; digital electric calculators. CONTRAVES A.G. Feb. 6, 1964 [Aug. 19, 1963], No. 5022/64. Headings G4A and G4G. A computer used in predicting the polar co-ordinates of a moving target at a given future time contains arrangements which continuously evaluate differences where γ m , # m , α m  are the momentary polar coordinates of the target as observed by a tracking instrument at an origin at a time t 0  and (γ v , # v , α v ) are the co-ordinates of a position V at which the target was at a past time t 0  - #, # being a fixed period. From these values the factors are evaluated, where and From these factors further factors a t =s v #/#, b t =b v #/#, c t =c v #/#, and d t = d v #/#, are evaluated where # is the time taken by a projectile fired at the time t 0  from the origin to intercept the target at the predicted position. Finally, using these factors, the equations are solved to give γ t , ## t , #α t , the required polar co-ordinates being γ t , # m +## t , α m +#α t . The differences #γ v , ## v , #α v  first evaluated may each be derived in an apparatus as shown in Fig. 3. The instantaneous value of the appropriate co-ordinate of the target (γ m , # m  or α m ) is fed as a shaft rotation to a converter P x , which feeds an electrical analogue signal to an increment signal transmitter IGX (t 0 ). From this, incremental signals are fed to an adder IA 1  and to a store VW # , where the signal is delayed by a period T, after which it is fed, sign reversed, to the adder IA 1  which thus evaluates The output is fed to a further IA 2  where the output from an incremental transmitter IG#x v  on the shaft of a servomotor M#x v  is subtracted from it, the difference being used as the input to the servomotor. The servomotor shaft is therefore positioned in accordance with #x v , and this position may be converted to an electrical signal by means of the converter P#x v . The predicting computer (Fig. 4) may be considered as divided into three parts TR1, PR1 and VR, the first part TR1 serving to derive the factors a v , b v , c v , d v . This part includes three of the difference deriving apparatuses described above, TB γ1 , TB# 1  and TBα 1 , provided respectively with inputs representing the co-ordinates γ m , # m , α m . Also included are sign changing units (-), adding units (+) and resolvers G 0 . By the logical combinations of these units according to the equations (1) to (4) the required functions are derived, and are fed to the multipliers Q in the part PR1. These carry out multiplication by the factor #/# to produce the functions at, b t , c t  and d, which are fed to the third part VR wherein the equations (5) to (7) are solved. The servo loop including the motor M# enables the continuous checking and correction of the time #, used in the multipliers PR1, to be carried out. The time # is set into the multipliers and also into a ballistic computer BR, which from this, the angle # t  and information regarding the projectile, computes the oblique distance γ t  which the projectile will travel in the time #. This is compared with the computed distance γ t  for the oblique distance to the target after this time, and any difference causes the servomotor M# to adjust the shaft W# to ensure that # is such that the projectile and target arrive at the same place at this time. The servo-arrangement based on servomotor M## t  acts in accordance with equation (5) above, the servomotor shaft setting in accordance with ## t , and that based on servomotor M#α t , acts in accordance with equation (7). The Specification describes an embodiment wherein a quadratic rather than a linear extrapolation to the collision point is carried out, the polar co-ordinates of two earlier target positions, at times (t 0  - #) and (t 0  - 2#) being used together with the position at time t 0  to establish the quadratic extrapolation law. Two sets of circuitry each similar to TR1 of Fig. 4 are used, one for each time period, one delivering a v1  - d v1 , corresponding to a period #, and the other a v2  - d v2 , corresponding to the period 2#. These are combined to produce functions a t2  - d t2  according to equations similar to which represent quadratic extrapolation. From these functions the required outputs are produced in the unit VR as before (Fig. 5, not shown).