Patent GB-1208310-A (GB)
Title: Improvements in or relating to electronic computing apparatus
Inventor: PANSCHOW RUDOLF
IPC: G06J1/00
Filed: 1967-12-21
Abstract: 1,208,310. Interpolating computer. SINA A.G. 21 Dec., 1967, No.58188/67. Headings G4A and G4G. An electronic calculating machine determines the value of a function of two variables at particular required values of the variables, by performing a linear interpolation with respect to one variable between values of the function at two values of that variable bracketing the required value of that variable, this interpolation being performed at each of two values of the other variable bracketing the required value of the latter, and a third linear interpolation with respect to the latter variable between the results of the first two interpolations, the four values of the function used in the first two interpolations being read from a stored table, sums and differences being formed digitally and quotients and products being formed in analogue manner. In Fig. 7, the required values of the variables y, x, in analogue form (from measuring devices or potentiometers), are converted to digital form at 2, the digital values being stored at 3 and in a counter at 2 respectively their more significant portions controlling a motor 6 and gates 8. The motor 6 positions a replaceable information carrier (punched tape or punched cards or film strips) in a store 7, and the gates 8 select some of the (binary) values read from the carrier to provide, in turn, the two pairs of function values for the first and second interpolations respectively. For the first interpolation, the larger and smaller of the two function values are placed in backward counters 11, 10 respectively. The counters 11, 10 are decremented, and a forward counter 13 is incremented, in synchronism, until the backward counter 10 holds zero. Then the forward counter 13 holds the smaller function value and the backward counter 11 holds the difference. The count in 11 now sets the value of the crosscoupling resistance of an analogue " interpolator " 14. The less significant portion of the variable stored at 3 is converted to analogue form at 15 and compared at 17 with the output of the analogue " interpolator " 14. Forward counters 13, 16 are incremented in synchronism, counter 16 controlling the input resistance of the " interpolator " 14 so that an output staircase voltage is produced from the " interpolator " (with a slope inversely proportional to the fixed count at 11), the comparator 17 stopping the counting on equality. The counter 13 holds the first interpolation result, which is now stored at 18. The second interpolation now occurs in the same way, but using the second pair of function values from the store 7. The third interpolation is also similar except that counters 10, 11 are loaded with the results of the first and second interpolations from 18, 13 rather than with a pair of function values from store 7, and the less significant portion of the other variable, transferred from 2 to 3, is converted to analogue form for comparison at 17. The final result is in counter 13 and was also fed as a pulse series to 20 via frequency dividers controlled in accordance with whether the function values used from store 7 were present multiplied by 1, 2, 5 or 10 this being indicated by marks recorded in the store 7 (this use of multiples permits greater accuracy for small values). To handle functions which are not monotonic functions of their variables, a rising or a falling staircase is used, selected by a comparison of the values of the function between which the respective linear interpolation is to be performed.