KR820002105B1 - Control system of level in being a gab - Google Patents

Abstract

The object of this system is to present a control system of level in a gab which shows prompt response and stability. When the error is out of a gap, it feeds back control output signal computed by the average of influx or effluence. When the error is in a gap, it produces the computed signal. In Fig.1 LC is a level control device, FC is a flux control device. Both devices are connected in series. The LC is primary, and FC is secondary. In Fig.2 if level h rises from a gap, influx is reduced and feedback of level h is performed. IF level h comes in a gap, control action dies out.

Description

Level control method with dead band

1 is a conceptual diagram of a control system to which the present invention is applied.

2 is an explanatory diagram of the operation of the apparatus of FIG.

3 is a detailed configuration diagram of the liquid level control device in FIG.

4 is a conceptual diagram of another control system to which the present invention is applied.

5 is a detailed configuration diagram of the liquid level control device in FIG.

The present invention relates to a level control method having a dead band.

For example, in order to control the liquid level or the like, a control device having a dead band is used.

Control devices with deadbands are also called gap-width controllers.

Conventional gap width controllers produce a control output signal when the deviation between the measured value and the set value is greater than the dead band (gap), return the deviation within the dead band, and when the deviation falls within the dead band, the control output signal is removed. It is fixed by the last tooth.

However, this fixed control output signal continues to reverse the deviation again, so the deviation finally jumps to the other side to pass through the deadband.

When the deviation jumps to the opposite side, the deviation returns to within the dead zone by the control output signal corresponding to this new deviation and finally jumps out in the original direction.

Therefore, when the conventional gap width control system is used, control becomes vibrating inevitably.

This vibration becomes more prominent as the gain of the gap width control system is increased, so that the control response and safety are not compatible.

An object of the present invention is to provide a level control method having a dead zone in which both control response and safety are compatible.

The present invention calculates the control output signal based on the average value of the inflow flow rate or the outflow flow rate while the deviation is out of the dead zone and returns it to the original state output. When the deviation is within the dead zone, the calculated output signal is output. will be.

Hereinafter, the present invention will be described with reference to the drawings.

1 is a conceptual configuration diagram when the present invention is applied to liquid level control.

In Fig. 1, LC is a liquid level control device having a dead zone, and FC is a flow rate control device, and both are connected in series with the liquid level control device LC as the primary side and the flow rate control device FC as the vehicle side. The low liquid level is used as the measurement value LC, and this and the control output signal according to the liquid level set value hs and the deviation are generated, and this is given to the flow controller FC as the flow rate set value fs. The liquid level controller LC uses the inflow flow rate f _in as an auxiliary input signal.

Flow control device FC is a measure word f _in the sluggish flow of the low flow rate and RS, an animation control signal output according to the deviation between the set values fs, gives it to the flow control variable FV.

The liquid in the low RS flows _out at the flow rate f _out according to the acceptance.

The liquid level changes depending on the difference between the inflow flow rate f _in and the outflow flow rate f _{out, but} the flow rate of the inflow liquid is controlled so that there is no change in the liquid level by the serial connection of the liquid level controller LC and the flow controller FC.

Control is performed as follows.

The operation explanatory diagram is shown in FIG.

When the liquid level h rises and out of the dead zone, the inflow flow rate f _in is reduced by the control action according to the deviation, and the return of the liquid level h is performed.

If the liquid level h falls within the dead zone, the control action due to the deviation is lost, and the control output signal is fixed to the value just before the liquid level h enters the dead zone.

Since the fixed control output signal is such that the inflow flow rate f _in is smaller than the outflow flow rate f _out to return the liquid level h, the liquid level h is returned again and finally corresponds to the liquid level set value h _s .

If it is left as it is, the liquid level returns to the dead zone on the opposite side, but at this time, the control output signal is changed, and the inflow flow rate f _in flows out as the solid line of f _in the lower half of FIG. Equalizing f _out will stop the return of the liquid level h.

The level h can then be stabilized in the dead zone as long as the outflow flow rate fout remains unchanged. In addition, although the change of f _{in in} FIG. 2 is expressed extremely rapidly, this is because the time scale is coarse, and in practice, it changes continuously with a certain inclination.

Then when the flow rate f _out changes, the liquid level h changes, but when it comes out of the dead zone, it is controlled as above and after returning the liquid level h to the vicinity of the set value h _s, the inflow flow rate f _in becomes equal to the new flow rate f _out , Stabilization of the liquid level h is performed. If the speed of return is made faster than the change of the outflow flow rate f _{out, the number} of levels h will remain in a dead zone, and the vibration of a level will be suppressed.

Therefore, even if the gain of the control system is increased and the quick response is increased, the safety of the control is not impaired.

The outflow flow rate f _out is not measured directly but calculated | required by calculation.

First, when the level h goes out of the deadband and returns, the level is expressed by the following equation.

다만' A는 저조 RS의 단면적으로 하고, 액위 h가 불감대를 뛰어난 시점을 t=0로 한다. 액위 h가 불감대내에 복귀한 시점을 t₁로 하면, 이때 액위 h는 h_H에 같으므로,

However, 'A' is the cross-sectional area of the low RS, and the time point at which the liquid level h is excellent in the dead band is t = 0. If the level h returns to the dead zone as t ₁ , then the level h is equal to h _H ,

It becomes

If the flow rate f _out does not change between t = 0 and t = t ₁ ,

f _out (t) = f _out (= schedule) (4)

Therefore, in the relation of equation (3), f _out is given by

In other words, the outflow flow rate f _out is obtained as an average value of the inflow flow rate f _in during the t ₁ period.

Equation (5) does not include the capacitance coefficient (cross-sectional area) of the low-order RS at all, and thus has generality not affected by the structure of the processor.

The above control is mainly performed by the action of the liquid level controller LC.

The details of the liquid level controller LC are shown in FIG.

In FIG. 3, CON is a control operator having a dead band and is equivalent to a conventional gap width control system.

CF ₁ and CF ₂ are comparators, INT ₁ and INT ₂ are integrators, and DV is a divider.

The control operator CON and the comparators CF ₁ and CF ₂ are given as input signals a deviation e between the liquid level measurement h and the liquid level set value hs.

Comparator CF _1, CF _2, the dead band is given for setting the set value Ws, and the deviation e _S, respectively.

The deviation set value e _S is smaller than the dead band set value Ws and becomes almost zero.

Integrators INT ₁ and INT ₂ are given inflow flow signals f _in and constant d through switching switches SW ₁ and SW ₂ , respectively.

The switching switches SW ₁ and SW ₂ both have open contacts.

These switches are switched by the output signal of the comparator CF ₁ .

When the absolute value of the deviation e becomes larger than the dead band set value Ws, the comparator CF ₁ inputs the switching switches SW ₁ and SW ₂ to the inflow flow signal f _in and the constant value d, respectively. In addition, comparator CF ₁ changes integrator INT ₁ and INT ₂ prior to this switching.

When the absolute value of the deviation e is smaller than the dead band set value Ws, the comparator CF ₁ feeds the switching switches SW ₁ and SW ₂ to the open contact side.

The divider DV converts the output path of the integrator INT _{1 as} the output signal of the integrator INT ₂ .

The output signal of the divider DV is given to the switching switch SW ₃ like the output signal of the control calculator CON, and one of these output signals is output as the flow rate set value f _s .

The switching switch SW ₃ is switched by the output signals of the comparators CF ₁ and CF ₂ .

The comparator CF ₁ inputs the switching switch SW ₃ to the control operator CON when the absolute value of the deviation e is greater than the dead band set value Ws, and the comparator CF ₂ sets the switching switch SW ₃ when the absolute value of the deviation is smaller than the deviation set value e _S. Input to the calculator DV side.

Such a liquid level control device LC operates as follows.

When the deviation e is out of the dead band, the switching switch SW ₃ is fed to the control calculator CON side by the output signal of the comparator CF _{1 and} the output signal of the control calculator CON is output as the inflow flow rate setting value f _s . This output signal corresponds to the deviation e and serves to return the liquid level h into the dead zone. The CF comparator ₁ is input again by the output signal of the integrator INT ₁ wherein, at the same time by changing them into the INT ₂ switching switch SW _1, SW ₂ flow signal f _in each of the inlet flow side and the work side value d.

Thus, integrators INT ₁ and INT ₂ change the last integral and then start integration for each input signal.

The change is to be done in a very short time.

When the deviation e returns to the dead band, the switching switches SW ₁ and SW ₂ are fed to the open contact side by the output signal of the comparator CF ₁ .

As a result, the integration of the integrators INT ₁ and INT ₂ stops, and the integrated values up to that point are held.

The output signal of the integral value INT ₁ is the integral value of the inflow flow rate f _in between the deviation e is out of the dead zone, and the output signal of the integrator INT ₂ represents the time when the deviation e is out of the dead band.

Therefore, the output signal of the divider DV at this time is given by the equation (5), and indicates the outflow flow rate fout. Even if the deviation e returns to the dead zone, the output signal of the control operator CON is output as the flow rate setting value f _s for a while, so that the deviation e becomes smaller again, and when this becomes smaller than the deviation setting value e _s , the output signal of the comparator CF ₂ The switching switch SW ₃ is fed to the calculator DV side.

As a result, the output signal f _out of the divider DV is output as the flow rate setting value f _s .

Thus, the inflow flow rate f _in is controlled to be equal to the outflow flow rate f _out , and the liquid level h is stable near the set value h _{s in} the dead zone.

In the above, the present invention can be applied to the case where the liquid level is controlled by the serial connection of two control apparatuses, or when the single control apparatus also controls the liquid level as shown in FIG.

In Fig. 4, the liquid level controller LC having a dead zone controls the flow rate control valve FV in accordance with the deviation between the liquid level h of the low tank RS and the liquid level set value h _s .

The details of the liquid level controller LC are shown in FIG.

In Fig. 5, the same symbol as that in Fig. 3 is lit.

In this system, the inflow flow rate f _in is not measured directly, so it is converted at the opening degree of the flow control valve FV.

Since the opening degree of the flow control valve FV corresponds to the output signal of the control calculator CON, it can also be converted into this output signal.

G ₁ is a conversion circuit for this purpose, and converts the shift degree signal or the control output signal p into the inflow flow rate f _in . Since the outflow flow rate f _out is calculated | required by the inflow flow volume f _in , _in order to give this to the flow control valve FV as a control output, it is necessary to convert f _out into the side control signal. G ₂ is an inversion circuit for the name. The other part is the same as the apparatus of FIG. 3, and the same operation is performed.

Therefore, when the liquid level h is turned back to near the set value h _s in the dead zone, the inlet flow rate f _in a controlled equal to the outlet flow rate f _out is carried out to stabilize the liquid level h.

The present invention can also be applied to the case where the liquid level is kept constant by controlling the inflow flow rate or the case where the liquid level is kept constant by controlling the outflow flow rate.

At this time, in each case, the inflow flow rate f _in and the outflow flow rate f _out may be changed and considered.

The present invention is not limited to liquid level control, but can be generally applied to level control having a dead band.

In the present invention as described above, the control output signal is calculated based on the average value of the inflow flow rate or the outflow flow rate while the deviation is outside the dead zone, and when the deviation is within the dead zone, the calculated output signal is output. It is compatible with the quick response of level control and safety.

Claims (1)

The outflow flow rate or inflow flow rate is measured by determining the level of the reservoir determined by external factors, and the level is constant by adjusting either the inflow flow rate or the outflow flow rate based on the deviation between the measured value and the set value. In the level control device having a dead zone, when the level deviation is outside the dead zone, the control output according to the deviation is used to adjust either the inflow flow rate or the outflow flow rate, and at the same time adjust the inflow flow rate or the outflow flow rate being adjusted. A level control method in which the inflow flow rate or the outflow flow rate is adjusted by a control output based on the average inflow flow rate or the outflow flow rate obtained from the flow rate integration value obtained up to that time when the level is substantially equal to the set value by integration.

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