Patent GB-1115717-A (GB)
Title: Control units
IPC: G05B19/4103
Filed: 1966-09-09
Abstract: 1,115,717. Digital calculators. INTERNATIONAL BUSINESS MACHINES CORPORATION. 9 Sept., 1966 [1 Oct., 1965], No. 40355/66. Heading G4A. [Also in Division G3] A control unit for a device having a part movable in two co-ordinate directions in response to control pulses comprises registers storing the values of distances to be travelled in each direction by the part, an arithmetic unit comparing the larger distance with the smaller value and successively increasing multiples thereof and a pulse generator responsive to the arithmetic unit for generating a pulse corresponding to the larger value after each comparison indicating a positive difference and for generating pulses corresponding to both values and for reinstating the comparison succession after all other comparison results with the current contents of the registers as new starting values. As shown, Fig. 1, recorded numerical data from a source 10, comprising change of position signals X, Y, on lines 20, 22 respectively are fed to an interpolator 12, producing pulses on lines 24, 26 for X and Y motion controls 14, 16 which produce analogue signals for moving a table 18 an incremental distance for each pulse received. X and Y position feedback signals are fed on lines 28, 29 to the interpolator, or, by operation of switches SW1, SW2 the interpolation is modified by the pulses on lines 24, 26. The interpolator compares the position signals to determine which is the larger and derives the difference, a pulse is then emitted for movement along the axis corresponding to the larger signal and the larger signal is reduced, by feedback by one pulse. The difference is compared with the smaller signal and if this time it is zero a pulse is developed for each axis of movement and both the signals reduced by feedback by one. The sequence is continuously repeated until both signals fall to zero and the table is at the programmed position. In the interpolator, Fig. 4, the recorded numerical data is stored in counters 60, 62. A start signal initiates a trigger 65 which energizes an AND gate 64 and initiates a trigger 71 starting a sequence clock 73. At clock time 1 the AND gate 64 is opened to transfer the contents of counter 60 to register 68; at the same time the contents of the counters are interrogated by a zero test circuit 67 and when both are zero the trigger 71 is turned off stopping the operations. When the contents of the counters are not zero, at clock time 2 the contents of register 68 and counter 62 are combined in a subtractor 70 and gated via an AND gate 72 to a register 74. When a comparator 76 indicates that the contents of register 74 is zero an AND gate 79 is energized at clock time 3 to turn on a Y pulse trigger 80 so that at clock time 4 both X and Y pulses are generated from AND gates 82, 83 to cause movement of the table. The pulses from AND-gate 83 are also fed to reduce the count in X counter 60 and the 1 signal from the trigger 80 is fed through an AND gate 90 to reduce, at clock time 5, the count in Y counter 62. When the value in register 74 is greater than zero the trigger 80 remains in the 0 state and at clock time 4 only an X pulse from the AND gate 83 is generated to move the work-table. The X pulse also reduces the count in X counter 60 by one. At clock time 5 register 68 is reset and at clock time 6 the contents of register 74, which contains the result of the subtraction in subtractor 70, is transferred to register 68 through an AND gate 87. At clock time 1 of the next cycle a zero test occurs and register 74 is reset. At clock time 2 the output of subtractor 70 is transferred to register 74 through AND gate 72. The sequence then continues in dependence on the comparison in comparator 76. The cycles are continued until the position signals are reduced to zero when an output from the zero test circuit 67 resets the run trigger 71 which stops the clock 73.