Verfahren und Vorrichtung zur Regelung der Vortriebsgeschwindigkeit einer Erzabbaumaschine

摘要

1,217,957. Automatic control systems. CHARBONNAGES DE FRANCE. Jan.23, 1968 [Jan.23, 1967], No.3449/68. Heading G3R. An automatic control system for regulating a parameter comprises means to compare at least one feedback signal representing the parameter with a reference signal representing, at each instant, the value of a regulating quantity, the feedback signal being transmitted, if the parameter exceeds a first threshold value for a time dependent on the excess, with a time delay also dependent on the excess, and being transmitted instantaneously if the parameter exceeds a second threshold value higher than the first. The control system is applied to an ore-cutting machine comprising an electric motor 1 driving the cutting member 3 and a variable delivery hydraulic pump 4 connected in closed circuit with a constant volume hydraulic motor 5 driving a towing cable drum 6 engaging the towing chain 7 of the machine. The lateral speed of movement of the machine is the regulating quantity and is controlled by a jack 8 which varies the inclination of the barrel 41 of the pump 4 to determine its delivery and hence the rotational speed of the motor 5. This speed is made dependent on the current taken by the motor 1 to maintain the current, and hence the power and driving torque, substantially constant. To this end, a feedback signal representative of motor current is obtained from a current transformer 15 and applied to threshold circuits Fig. 3 (not shown) which respectively include the potentiometers P7, P8 and produce signals U1b7 and U1b8. The former signal is applied to an RC circuit 19 whose output signal U11b7, together with the signal U1 b8, is applied to a comparator X controlling the jack 8 via a valve 9 and multi-vibrators T4-T7. The comparator X is also supplied with a signal Ur representative of the inclination of the barrel 41 and hence of the machine speed, which is initially set by adjustment of a potentiometer 14. controlling a signal Ua applied to the comparator X. Normally the machine runs at the set speed and a rated current, for which conditions the control system is inoperative. Should the motor current exceed a first value I 1 a signal U1b7 is produced and a corresponding signal U11b7 is applied to the comparator X increasing at a rate determined by the amount by which the current I 1 is exceeded. If the signal U11b7 reaches a value sufficient to actuate one of the multi-vibrators, the valve 9 is operated to reduce the machine speed and hence the motor current, stabilization occurring when the signals Ur U11b7 become equal corresponding to a new speed/current condition which continues until the next control operation. If the amount and duration of the excess current (over I 1 ) is below a predetermined value (set by choice of the circuit parameters) the signal U11b7 does not reach a value sufficient to operate the valve 9 and the machine continues undisturbed. If the motor current exceeds a second value I 2 (greater than I 1 ) a signal U1b8 is produced which is applied instantaneously to the comparator X to reduce the machine speed until the condition Ur U1b8 is reached. If this condition corresponds to a current between I 1 and I 2 , the signal U11b7 then takes over to reduce the speed and current further. A typical operating cycle for the machine is discussed, Fig.4 (not shown). The machine speed is also controlled by a system 20-23 responsive to the pressure in the hydraulic circuit and corresponding in function to the current feedback system, a discharge valve 20 operating in response to a high pressure P2 (equivalent to I 2 ) and the members 21, 23 operating in response to the excess and duration of pressure over a value P 1 (equivalent to I 1 ). The current and pressure feedback circuits, the comparator X and the control circuit for the valve 9 are described, Fig.3 (not shown) and include a transistor comparator, transistor multi-vibrators or Schmitt triggers, RC circuits and resistor-potentiometerdiode arrangements. The valve 9 is the symmetrical type, with two control windings and automatic return of the slide-valve to a central position. The control system may also be responsive to the temperature of the motor 1, for example by adding a temperature representative signal U# to the current signal from transformer 15. The machine speed can also be controlled (during inactive periods of the current-pressure control system) by a signal from a remote control unit 25 applied to the comparator X.