DE2426966C3 - Method and device for regulating the discharge from a bunker - Google Patents

Description

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The invention relates to a method and a device for regulating the discharge from a bunker, whose actual weight is recorded with an integrating transducer.

The regulation of the discharge from a bunker or a similar container is used in numerous applications carried out in such a way that an electrical quantity proportional to the filling weight is differentiated. the The measured variable obtained by differentiation is fed to the discharge control loop as an actual value.

The discharge control, which works with the differentiating measuring method, can also be carried out digitally will. In this case, an electronic tracking system follows the container weight, which is measured by means of a Load cell is detected. Weight-weighted pulses are emitted from the measuring device. The pulse frequency is compared with a reference frequency in an up / down counter. "5

Such differentiating measurement methods are susceptible to interference, in particular from higher-frequency ones Sources. These disturbances occur mainly in bunkers for bulk goods. As a result of inner movement of the bulk material and due to the sliding of the bulk material on the embankments is differentiated Container weight signal very harmonic

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With a "restless", i. H. showing rapid changes Actual value, the discharge control can also be very uneven. If the actual value is smoothed occurs, the dynamic behavior of the control loop is adversely affected. Such a differentiating Measuring device cannot be easily implemented with an indicating measuring instrument.

Integrating transducers are known for determining the weight of the bunker, but they were but not used for a bunker discharge control because it is not proportional to the discharge rate Send signal.

The object of the invention is therefore to provide a method and a device for regulating the discharge of the bunker execute that the advantages of an integrating measuring device, high resolution and high shutdown accuracy regardless of the discharge rate, with a low susceptibility to failure.

This object is achieved according to the invention in that the measured at the beginning of a control cycle Bunker actual weight is set as a digital number in a counter so that the counter then operates at a frequency corresponding to the target value of the bunker discharge it is counted down during a predetermined period of time so that the counter reading reached with the actual bunker weight is compared at the end of the control cycle and that the result of this comparison is used as a manipulated variable is used to change the bunker discharge.

This process, which works in digital technology, is used to regulate the discharge by means of an integrating transducer causes a high resolution and high cut-off accuracy regardless of the output power. The integration time can be freely selected with optimal adaptation to the operating conditions will. The susceptibility to failure is very low.

A particularly advantageous device according to the invention for performing the method with a Bunker, an integrating measuring transducer for the actual bunker weight and a driven one in the Variable speed bunker discharge unit, the parts of a control circuit for regulating the bunker discharge are, is characterized in that an up-down counter is provided in the control loop, whose Inputs via switching devices controlled by a control unit, optionally with the transducer or a frequency generator can be connected, the output of which is connected to an input of a comparator whose other input is connected to the transducer, which via its output the Bunker discharge device controls. This control loop is made up of relatively simple ones that are less prone to failure Components built.

The invention is explained in more detail below in the description and drawing on the basis of a schematic exemplary embodiment.

The figure shows a control circuit for bunker discharge control in a block diagram.

A bunker 1 has a discharge device 2, for example a screw conveyor, which is of a Motor 3 is driven at a variable speed. The bunker 1 is based on a transducer 4, which is designed as a strain gauge load cell

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can be and part of an integrating measuring system 5 is, in which the weight of the full hunk I is in digital form.

At the end of a measurement / cycle of a given duration If the measuring system 5 sends a signal 5 I to a l.eit plant 6. At the beginning of a control cycle, the tail unit gives 6 a signal .S'3 to an AND element 7, whereby the Uigilalwert pending at an output of the measuring system 5 of the bunker weight in a forward-backward counter 8 is set, which is set with a frequency / iuii, which corresponds to the target value of the bunker discharge, against Zero counts.

The frequency Λ «· ι · is an input of the payer 8 supplied via an AND element 9 from a frequency generator IO at which the frequency Λ ,, ιι either unmiltel rs bar is set or to which the setpoint in the form of a setpoint voltage from a setpoint adjuster Il is fed; in the latter case! would be the frequency generator OK a voltage frequency / wanciler. The AND gate 9 is controlled by a signal 56 which is emitted by the control unit 6 and also the measuring system 5 is fed.

After a measuring cycle of a predetermined time has elapsed, the signal 56 is sent via the AND element 9 of the counter 8 stopped and in a comparator 12, which is connected to an output of the measuring system 5 and an output of the counter 8 is connected, a comparison of the target counter reading in the counter 8 with the actual value of the bunker weight in the measuring system 5 is carried out.

At the comparator 12 there is a dependent wedge on the comparison result an output signal 54 or an output signal S5. The signal 54 is logical 1 if the actual value in the measuring system 5 is greater than the count in the counter 8; the signal 55 is logical 1 when the The actual value in the measuring system 5 is less than the counter country in the counter 8; both signals 54 and 55 are logic 0. when the actual value in the measuring system 5 is equal to the status of the counter 8. The signal 54 becomes an AND gate 13, the signal 55 is fed to an AND element 14, each of which has two further inputs sen, at which a signal 52 from the tail unit 6 or the output of an oscillator 15 are present. The out The AND gate 13 has a "forward" input of the counter 8 and a "forward" input output of a counter 16 connected; the output of the AND gate 14 is with a "backward" -F.ingaiii: of the counter 8 and a "backward" input of the counter 16 are connected. Depending on whether the Signa! 5 4 or the signal 55 is logic 1, the oscillator 15 counts the counters 8 and 16 forwards or backwards if the signal 52 is also a logic 1. The impulses of the oscillator 15 are allowed through until the signals 54, Si of the comparator 12 have the logical zero, i.e. H. until the status of counter 8 is equal to the actual value in meter 5. The counter reading in counter 16 corresponds now, converted in a digital-to-analog converter 17, a new manipulated variable for the discharge organ 2.

In the embodiment according to FIG. The motor 3 of the discharge screw 2 is preceded by a control amplifier 18 which is controlled by the converter J7. It goes without saying that another discharge device can also be used.

The next measurement and control cycle begins again by the control unit 6 with the signal 56 via the AND element 9 lets the pulses with the set frequency / should pass to the counter 8 and the measuring system 5 starts up.

At the end of the control cycle, the counter 8 contains the last actual value of the bunker weight. During the In the blind phase of the measuring system, the counter 8 is paid back with a discharge rate proportional to the frequency. The counter reading in counter 8 thus corresponds to the extrapolated bunker weight. On at one off The comparator 19 connected to the counter 8 can thus store a setpoint memory in a connected bunker Record and signal 20 stored switching points with high accuracy. With one of the Comparator 19 controlled switch 21 can interrupt the discharge process exactly at the desired switching point will.

The described control device can be used for a quantity measurement (e.g. for a control measurement between two fixed bunker fill levels) a very high resolution can be achieved.

1 sheet of drawings

Claims (3)

Palent claims: 1. Procedure for regulating the discharge from a bunker, the actual weight of which is linked to an integrating Transducer is detected, thereby marked that that at the beginning a control cycle measured bunker actual weight is set as a digital number in a counter that the Then counter with a frequency corresponding to the target value of the bunker discharge during a predetermined period of time is paid back that the counter reading reached with the bunker actual weight is compared at the end of the control cycle and that the result of this comparison is used as a manipulated variable is used to change the bunker discharge. 2. Apparatus for performing the method according to claim I with a bunker and an integrating measuring sensor for the actual bunker weight and a driven, variable speed bunker discharge organ, which are part of a control loop for regulating the bunker discharge, characterized in that a forward in the control loop -Reverse counter (8) is provided, the inputs of which are via a tail unit (6) controlled switching devices (7, 9) optionally with the transducer (4, 5) or a frequency transmitter (10) can be connected, the output of which is connected to an input of a comparator (12) is, whose other input is connected to the measuring transducer (4,5), which via its output the bunker discharge device (16, 17, 18,3,4) controls. 3. Apparatus according to claim 2, characterized in that optionally in each case a forward input or a backward input of the forward-backward counter (8) and one of the bunker discharge device (17, 18, 3, 2) controlling up / down counter (16) via two of the outputs the comparator (12) controlled switching devices (13, 14) can be connected to an oscillator (15) are.