| 摘要 |
PURPOSE:To provide the subject device wherein the stage is shifted by accelerating the speed from the low speed, and is retarded as it approaches the target position, thereby to cause the stage to reach the target position in a short time and accurately. CONSTITUTION:A target value is afforded to a register 9, where it is compared 12 with the shifting quantity stored in a counter 11. When the result of comparison exceeds a predetermined value, flip-flops 13 and 14 are set and a pulse ''H'' is supplied to open a gate 18. The pulse from a variable frequency oscillator 17 are supplied to a motor 8. The pulse ''H'' is integrated 15, and a voltage addition value 16 is saturated in a period I. Accordingly, the output pulse of the oscillator 17 increases its frequency in the period I, and assumes a high predetermined frequency determined depending upon the saturation value of an integration circuit 15. Accordingly, the difference between the stored value of the register 9 and that of the counter 11 is reduced, and it is compared 12 with the predtermined value, the flip- flop 14 being reset and the integration circuit 15 is discharged, thus the input signal of the oscillator 17 being reduced to the initial value. When the stored value of register 9 coincides with that of the counter 11, the flip-flop 13 is reset, and the gate 13 is closed to stop the supply of pulses to the motor. |
