Patent GB-1453942-A (GB)
Title: Axis command pulse generating apparatus and numerical control equipment incorporating same
IPC: G05B19/4103
Filed: 1973-12-18
Abstract: 1453942 Generating axis command pulses H CUTLER 18 Dec 1973 [29 Dec 1972] 58579/73 Heading G3N  In apparatus providing command pulses to at least two co-ordinate axes, to generate a path in circular interpolation to be followed at a programmed feedrate, feed pulses (FP) on line 72, provided at a rate in accordance with the programmed feedrate data, and the instantaneous path direction, are distributed to one or other of the drives 6, 8 in accordance with the sign of the contents of an error register to which, in use, is added or subtracted the content of one or other of two axis data registers, the latter being updated in mutually opposed polarity senses for each incremental pulse applied to the corresponding drive. Circular interpolation in two dimensions, Fig. 2 (not shown). Path generator 12 comprises X, and Y axis data registers (100X, 100Y), initially storing the components (Xo, Yo) Fig. 2a (not shown) of the initial radius vector. Whenever the content of the error register (110) is less than zero, any feed pulse (FP) is gated to provide a Y drive pulse (YPC) which is also added to the content of register (100Y), the content of the latter being added to the error register. Should the error register content be greater than or equal to zero an X drive pulse is produced and subtracted from register (100X), whose content is subtracted from the error register content. The interpolation can be performed either in the sense of decreasing modules of X, see Fig. 2c (not shown) as above, or increasing modulus of X, see Fig. 2b (not shown) in which case X pulses are added to, Y subtracted from, the respective registers. Linear interpolation Fig. 3 (not shown). The apparatus may be operated in linear interpolation, in two or three, dimensions, in which case one, or two error registers (210, 212), are provided. When the contents of both are less than zero, pulses FP are gated to provide X command pulses XCP each of which causes the content of register (200Y) to be added to error register (210) that of 200X being added to (212). When the sign of the content of register (210) changes, the feed pulses are fed as Y command pulses, the content of register (200X) being subtracted from register (210) the content of (200Z) being added to (212), until the content of the latter changes sign, whence feed pulses are provided, the content of both registers 200X, 200Y being subtracted from register (212) until both registers (210, 212) are again negative in their contents. Control system, Fig. 1. Magnetic or punched tape, 2, or MOS memory, is read to provide feedrate data to unit 70 controlling production of the pulses FP, and sets the path generator 12, and the drives for circular (or linear) interpolation. Path data comprising beginning and end points of a sequence of motions, together with an initial radius vector for segments to be followed in circular interpolation is also provided. For each axis drive, register CCP stores the current commanded position, PCP the programmed commanded position, comparator 24 gating the drive pulses for a commanded direction of motion until the register counts are equal. When such counts are equal for all axes of motion, a new data command is transmitted to the reader 4. The unit 70 may take the form disclosed in Specification 1453941.