Patent GB-931048-A (GB)
Title: Apparatus for controlling relative motion by electric pulses, especially for automatic machine tool control
IPC: G05B19/4103
Filed: 1961-12-07
Abstract: 931,048. Numerical control systems. BENDIX CORPORATION. Dec. 7, 1961 [Dec. 8, 1960], No. 43873/61. Class 38 (6). [Also in Group XIX] A machine tool is provided with a digital computer so that the tool either moves linearly for distances specified on a binary-coded-. decimal punched tape at a velocity similarly specified on the tape; or else moves in a circular path between first and second co-ordinates specified on the tape, again at the specified velocity. Movement along each of the 3 possible axes of the machine tool is effected by motors which respond to incremental pulses, the speed of movement being proportional to pulse frequency and the displacement to the total number of pulses. Linear motion.-The feed rate, and the sense and magnitude of the required displacement along X, Y and Z axes are recorded serially in binary decimal code on a manually prepared punched tape, Fig. 2 (not shown). The four addresses are read and converted into simple binary code at 32, the 3 displacement addresses being prefixed by a "0" or a " 1 " to indicate sense. The displacement addresses are then multiplied by 2 a sufficient number of times to ensure that the most significant digit of the largest of the 3 numbers occupies the next. space to the " sense " digit, for convenience in subsequent operations. All four addresses are then placed serially in a recirculatory store 48 of the magneto-striction wire type, access to the appropriate address being obtained by clock pulses from a generator 38. At intervals determined by another timing generator 76, which forms the basic speed control of the machine tool the feed-rate address is supplied via an adder 810 to a storage register 82 where it is repeatedly added to itself, and a feed pulse is generated at 84 each time register 82 overflows. Thus a train of feed pulses is generated having a frequency proportional to the recorded feed rate. The feed pulses open a gate 72 so that the displacement addresses can similarly be repeatedly added to themselves by the adder 80 and the appropriate part of the register 82 to produce overflow pulses which are detected at 86 to form the command pulse train for the machine tool servos. The repetitive addition is stopped after 2N cycles, where N is the number of digits in the longest of the 3 displacement addresses. Circular interpolation.-The X and Y coordinates of the beginning and end of the cut are recorded on the punched tape and converted to simple binary code as above, store 48 accommodating the beginning addresses, and a store 50 accommodating the end addresses. The train of feed pulses is generated as above. The X and Y addresses from store 48 are initially added to themselves in register 82 as before but the overflow pulses from the X address are used to control the Y servo and vice versa. Moreover the overflow pulses pass through a gate 100 to a half adder or subtractor 70 which either adds or subtracts a "1 " from the X. and Y addresses as they pass from store 48 to the adder 80. The correct sign is controlled by a sign store 102, in accordance with the desired direction of movement round the circle, and also in accordance with the particular quadrant in which the operation is taking place. The process continues until a comparator 54 detects that the modified X and Y addresses from 70 coincide with the end of cut addresses stored at 50. Specifications 848,509 and 848,647 are referred to.