Patent GB-1051640-A (GB)
IPC: G05B19/37
Abstract: 1,051,640. Programme control of machine tools. GENERAL ELECTRIC CO. Nov. 21, 1963 [Nov.21. 1962 (3)], No.46031/63. Heading G3N. Command data is prepared on a punched tape and represents in each block, 6 decimal binary coded indication to provide for a resolution of 0À0001 of an inch for positioning up to 100 inches, coded indication of the axis to which the position relates, a parity indication and an end of block coded indication. The tape is fed to a reader 31 four outputs of which are connected to a read-in counter 21 and these and the other outputs of the reader are fed to a number recognition circuit 32, an address recognition circuit 33 and a sequence control circuit 34. The positioning arrangement is described for the X-axis only and the receipt of an X axis address from the reader 31 by the address circuit 33 causes a row counter 35 to be reset and to develop outputs in dependance on control signals T3, T4, of the timed sequence of control signals Fig. 15 (not shown) produced by the sequence control circuit 34 and since T3 is  the first to occur after the recognition of the address, the reset of command phase counters 36-38 is initiated. Zero-offset values are manually set by coded switches, Fig. 16 (not shown), for the coarse and fine command phase counters 36, 38. The zerooffset values are transferred to the phase counters on the receipt of the T4 control signal. Presetting of command data is effected after the reading of the X-address, the tape being stepped and the first digit read. A time sequence of the control signals is generated by the circuit 34 and in response to the signal T1 the read digit is set in the counter 21. The signal T1 is also applied to the number recognition circuit 32 which causes, since a number has been detected, a signal to count-down pulses from the counter 21 which are fed to the appropriate decade of the coarse and fine command phase counters 36, 38. The counter 21 is counted down by 50KC pulses derived from the first decade of a pulse rate divider 50, which is fed at 125KC by a pulse rate generator 70 which is enabled by the control signal T3. When the count in the read-in counter 21 has been reduced to zero a gate is blocked so that the number held in the first digit of the coarse command phase counter 36 is equal to that originally in the read in counter. The control signal T4 resets the counter 21. The tape is then stepped and the sequence repeated until all six digits have been read into the appropriate decades of the coarse and fine phase counters.  The medium command phase counter 37 is set by transferring selected digits from the fine and coarse decades, which comprise binary stages weighted 1, 2, 4, 5 to the appropriate binary stage of the medium decades which are weighted 1, 2, 4, 8. The transfer is effected by the control signal T3 through a flip-flop 9 which is set on the occurrence of the next triggering pulse from the second decade of the pulse rate divider and applies a signal to the transfer leads of the medium counter decades. The generation of phase-coded command signals is effected at the next occurring termination of a count of a thousand in divider 50 which initiates the counting in the command phase counters. The pulse rate generator 70 triggers the inputs of the fine and course command phase counters and the medium command phase counter. In response to recurring trigger impulses each command phase counter increases the number registered therein and as they reach a count of 1, 000 each counter resets to zero and continue counting, a logic 0 signal being produced at the "1" output of the most significant decade of each counter. The instant of occurrence of these logic 0 signals with respect to the time at which counting commenced is commensurate with the numbers preset therein. The commanded position outputs signals are phase coded signals representing the coarse, medium and fine components, respectively, of the input command data as modified by the preselected zero offset. Phase - coded position signals are generated by conventional feed back resolvers 43, 44, 45, which are energized in quadrature by the output of the pulse-rate divider 50 through a resolver supply 51. The output of each resolver is applied to a wave-shaper wherein their sine wave output is squared. The actual position output signal of the wave shapers are thus phase modulated signals wherein the time of transition from a first to a second state occurs with respect to the 250 cycle reference signal developed by the pulse rate divider 50. The resolvers are geared 46, 47 so that one revolution of the coarse resolver represents 100 inches of movement, of the medium resolver 2 inches of the fine resolver 0À1 inch. Positioning is effected in five zones of successively narrower range each being defined by a distance from the commanded position. The determination of whether the commanded position is larger or smaller than the actual position is accomplished by examining the order in which the command and actual position signals occur in time with respect to a reference signal chosen to allow for over-shoot i. e. for commanded position within a range 0-98 inches the reference is 99 inches. This is effected by a coarse command comparator 43. The direction and speed of apparatus travel is such that when outside the coarse zone a fast positioning rate is selected and within the coarse zone by a comparison of command and position signals. Within the coarse zone i.e. 0À6 of an inch the flop conditioned by selected stages of the coarse command phase-counter. Within a first intermediate zone i. e. 0-2 of an inch signal responsive to the signals from the medium command phase counter reduces the positioning rate to an intermediate value. Within a second intermediate zone of À080 of an inch and subsequently a third zone of À030 of an inch, a phase discriminator determines the actual phase differences between the fine command and the fine position signals to derive an analog signal proportional to the phase difference so that the positioning rate is proportional to the positioning error. Final positioning within a À002 of an inch zone is effected through the fine command phase counter, de-energizing a capacitively slugged relay not shown, so that the motor 49 positions within the zone.