High precision closed loop servo system

Abstract

Abstract 1,092,691. Programmed machine tool control. FUJITSU Ltd. Dec. 14, 1964 [Dec.14, 1963], No. 50915/64. Heading G3N. [Also in Division G4] A movable member of a machine control system is positioned by an hydraulic motor controlled by an hydraulic valve positioned by an electric pulse motor the direction of rotation and rotation of which is controlled by a driving means, signals from a movement detector, corresponding to the movement and direction of movement of the member, being fed back to the driving means to prevent movement of the member in excess of that determined by the driving means. As shown, Fig. 1 a control unit 11 comprising a reader for a punched or magnetic tape, or a manual keyboard, provides positive or negative control pulses on lines 12, 13, respectively, to a motor driving circuit 14. The motor driving circuit comprises a reversible ring counter and an amplifier, the output of which on lines 18, 19 controls the operation of an electric pulse motor 17 Fig. 5 (not shown). The rotation of a shaft 21 of the motor 17 positions an hydraulic rotary pilot valve 51 determining the supply of fluid to an hydraulic motor 53, Fig. 3 (not shown). The motor 53 rotates at a speed and in a direction corresponding to the angle of rotation of a core 58 of the hydraulic valve 51. A shaft 66 of the motor 53 is coupled to a control shaft or feed screw 81 of a machine 82 through a gear-box 83. The shaft 81 drives a table 84 through a nut 85 and the extent of table movement is derived as a plurality of pulses, from a photo-electric device 86, having a polarity indicative of the direction of movement, Fig. 9 (not shown). The movement pulses are fed to a synchronizer 87 along lines 88, 89. The synchronizer Fig. 12, comprises independent branches for the positive and negative pulses having a common clock pulse, at higher rate than the movement pulses, on a line 91 from the control unit 11. The clock pulse on line 91 is phase shifted by half-a-cycle from the control pulses. Bi-stable circuits 122, 133, enabled by clock pulses on line 91, together with a NOT-circuit 121 and an AND-gate 124 are connected between the input line 88 and an output line 93. An output pulse, has a duration of one clock period and occurs during the clock period succeeding that in which the input pulse terminates. The synchronizer prevents the simultaneous presentation of control and movement pulses to the reversible ring counter of the motor driving circuit 14. It is stated that a differentiating circuit 131 can be utilized at the input to the circuit 14 to shorten the pulse duration. In operation, a control pulse causes the reversible ring counter to count one and rotate the pulse motor 17 one step, the motor 53 moves in correspondence and positions the table 84 so that a feedback pulse is produced by the device 86 which, through the synchronizer 87 causes the counter to return to zero.

Inventors

No inventors recorded.

Bibliographic Details