GB1286866A - Servomechanism - Google Patents

Abstract

1286866 Programmed control of machines; automatic speed control FUJITSU Ltd 21 Nov 1969 [21 Nov 1968] 57222/69 Headings G3N and G3R [Also in Divisions H2 and G4] A servo-mechanism control circuit for supplying stepping motor drive pulses, compensated in dependence on motor, load, comprises a numerical control device 100, Fig.1, containing a pulse-generator developing command pulses which are fed on a line 101 to a pulse train converter 102 which transmits a smoothly varying train of command pulses to an electro-hydraulic pulse motor 107, comprising an electric pulse motor 108, a rotary pilot valve 109 and a hydraulic motor 110. An output shaft 111 of the motor 107 drives a machine tool 112. The command pulses on line 113 count up a counter 118 which is counted down by pulses, from a transducer 119 coupled to shaft 111, to derive the actual error e. The command pulses are also fed through a gate 115 enabled for a certain time by a signal on line 116, to a counter 114, reset through line 117, in which is stored a valve e s proportional to the command pulse frequency and representing the desired system error. The desired error e s is compared with the actual error e in a comparison circuit 120 the output of which controls a gain circuit 124 raising the gain, (defined as the ratio of command pulses to error) by one step when e >e s and lowering the gain by one step when e < e s. The pulse train converter 102 comprises, Fig.3, a register 103 fed with the command pulses on a line 301 to an addition input and the output motor drive pulses on line 316, to a subtraction input. The accumulated error is fed, in binary form, on lines 1 2 0-1 2 n to transistors QO-QN which are rendered non-conductive by a logic "1", that is zero-voltage, on a line so that a current path exists through a corresponding path such as that comprising resistors R30, R40 and diode DO. The resistance value of each path associated with the transistors are weighted in accordance with the corresponding binary valve and determined the pulse frequency of an resistancecapacity oscillator 305 comprising a unijunction transistor Q5. The output of the oscillator is fed, on line 315 to a wave-shaping amplifier 306 comprising transistors Q6, Q7. The gain adjusting circuit 124, Fig.1, is similar to the circuit of Fig.3, except that the transistors corresponding to QO-QN vary the capacitance of the emitter circuit of the unijunction transistor.