JPH01245301A - Control device - Google Patents

Abstract

PURPOSE:To calculate a proper manipulated variable by individually executing the integration control and a proportional differential control of a process value and synthesizing a manipulated variable based on the integration control with that based on the proportional differential control. CONSTITUTION:An integration gain setting circuit 12 on a connection line 10 multiplies the gain of '0', '+' and '-' by a deviation en between an objective value and a process value PV in accordance with the size of the deviation en and outputs a gain correction value ie'n. A corrected deviation e'n is applied to an integration circuit 14 every sampling period Ti and the circuit 14 calculates a manipulated variable by integrating the corrected deviation e'n and sends the calculated value to an adder 15. In a line 20, a preceding process value PVn-1 is held 21, a current process value PVn is subtracted 24, directivity gain with a gap is generated from a differential gain setting circuit 24 in accordance with the size of a difference DELTAPV in each sampling period, the obtained gain is differentiated 25, the differentiated result is added to the adder 15 to be a synthesizing circuit, the adder 15 adds a manipulated variable differential term to a manipulated variable integrating term obtained from the circuit 14 and outputs a manipulated variable MV.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a control device.

(Prior art) For example, when changing the number of operating blowers, pumps, etc. to control the level of gas holders and reservoirs, conventionally the sixth
A control device as shown in the figure is used.

This conventional control device is composed of a subtractor 1 between a target value and a process value, a PID calculator 2, and a sampling timer 3, and it performs proportional control operation, integral control operation, etc. depending on the deviation between the process value and the target value. The differential control operation is performed simultaneously.

(Problem to be Solved by the Invention) However, in such a conventional control device, the only place where the control period is set is the sampling timer 3 for the PID output, and the period is set independently for the integral term and the differential term. Since it was not possible to set the settings, if a control operation was performed to keep the process value constant, commands to start and stop the blower and pump would be issued frequently.
On the other hand, if the sampling period is set long, there is a problem in that the Brose value becomes unstable.

This invention was made in view of these conventional problems, and it completely separates the sampling period of the proportional term and the sampling period of the integral term, and maintains the control amount within a certain range in the integral term. Transient correction should be done using a proportional term,
It is an object of the present invention to provide a control device that can perform stable liquid level control without frequently starting and stopping devices to be controlled such as blowers and pumps.

[Structure of the Invention] (Means for Solving the Problem) The control device of the present invention includes a gain setting circuit that sets an integral gain based on the gapped bending pattern characteristic depending on the magnitude of the deviation between the process value and the target value. , an integral sampling switch that provides an integral sampling period; an integrating circuit that integrates the output of the integral sampling switch and outputs an integral term manipulated variable; A proportional sampling switch that determines the period, a proportional gain setting circuit that sets a gapped directional gain for the output from this proportional sampling switch, and a proportional gain setting circuit that differentiates the output of this proportional gain setting circuit and outputs a differential manipulated variable. The device includes a differentiating circuit, and a synthesizing circuit that synthesizes the output of the proportional differentiating circuit with the output of the integrating circuit.

(Function) In the control device of the present invention, the sampling period is set individually for the integral circuit and the proportional-differential circuit, and the integral circuit side performs M control to keep the controlled variable within a certain range. By performing transient correction using a proportional term, it is possible to perform stable liquid level control by reducing blower and pump startup and digital operations.

(Example) Hereinafter, embodiments of the present invention will be explained in detail based on the drawings.

FIG. 1 shows an embodiment of the present invention, in which an integral control line 10 includes a subtractor 11 between the target value S and the process value P, and a gap with a gain of 0 depending on the magnitude of the deviation en. A setting circuit 12, an integral sampling switch 13, an integrating circuit 14, and an adder 15 are provided.

Also, as the differentiation line 20, a hold circuit 21 for the process value P■ of the previous sampling time, a subtractor 22 for the previous process value PVn-1 and the current process value PVn in this hold circuit 21, and a proportional term sampling for setting the differentiation period. It includes a switch 23, a proportional gain setting circuit 24, and a differentiation circuit 25.

Sampling cycle generation circuits 16.26 are connected to each of the sampling switches 13.23, and the sampling cycles of the sampling switches 13.23 are individually set by these sampling cycle generation circuits 16.26.

The operation of the control device having the above configuration will be described next.

In the integral gain setting circuit 12 of the integral line 10, 0. +
, − is multiplied by this deviation en to correct the gain, e
Output n-.

Then, this corrected deviation 6n- is given to the integration circuit 14 every sampling period TI, and the operation amount is calculated by integrating it in the integration circuit 14, and this is output to the adder 15.

In the differential line 20, the previous process value PVn-1 is held in the hold circuit 21, the current process value PVn is subtracted by the subtracter 22, and the differential gain setting circuit 24 is used in accordance with the magnitude of the difference ΔPv for each sampling period. is multiplied by the gapped directional gain, differentiated by the differentiation circuit 25, and the result of this differentiation operation is sent to the adder 1 as a synthesis circuit.
5, the manipulated variable differential term is added to the manipulated variable integral term of the integrating circuit 14, and the manipulated variable MV is output.

In this way, integral control and proportional derivative control are performed separately on the process value PV, and the manipulated variable by proportional derivative control is combined with the manipulated variable by integral control, and an appropriate manipulated variable MV can be calculated. It is.

FIG. 2 shows an embodiment of a level control device for a gas holder.

Generally, the amount of gas used B repeatedly increases and decreases significantly depending on the operating process of each piece of equipment, and it is necessary to maintain the gas pressure at a constant value even during such load fluctuations and supply stable gas to each piece of equipment. A gas holder is installed to suppress this pressure fluctuation, and in the equipment shown in FIG.
4 is provided.

Further, a supply gas flow rate detector 35, a usage gas flow rate detector 36, and a level meter 37 for the gas holder 34 are installed as a process value detection system.

The level detection signal a of the level meter 38 of the gas holder 34 is input to the level control device 39, and this level control device 3
In step 9, the operation amount b required to maintain the gas level within the allowable range of the gas level of the gas holder 38, that is, the increase or decrease in the number of operating blowers, is calculated and given to the operating number calculation circuit 40 of the blowers based on the gas usage amount. It will be done.

The number of operating blowers calculation circuit 40 calculates the number of operating blowers from the gas usage amount C, and adds it to the increase/decrease signal of the number of operating blowers from the level control device [39], and this calculation result d is given to the number of operating blowers determining circuit 41 It will be done.

As shown in FIG. 3, the blower operating number determination circuit 41 issues an operation command for 653 units...3 units, 622 units... 2 unit operation command, d≧1 unit... 1 unit operation command, Outputs the operation number command f, and blower 3 is activated according to this command.
1 to 33 are operated, and the level of the gas holder 34 is controlled to be maintained within a certain range.

FIG. 4 shows the control function flow of such a level control device for a gas holder. Based on the gapped polygonal line characteristic of the integral gain setting circuit 53, the level of the gas holder 38 is within the "H" and "L" levels. The correction amount O when
It is separated into a gain correction amount when the gain is outside the "H" or "L" range.

When the gain correction amount is determined to be 0 by the H, L determination section 51, the hold circuit 52 holds the previous operation amount, and when it is outside the "H" or "L" range, the gain correction amount is determined according to the magnitude of the deviation. The gain setting circuit 53 determines the gain correction amount on the + side and the - side, and the integration circuit 55
It is integrated by

In this way, the control target value has a range of "H" and "L",
By performing gain correction and integrating when the level is outside the "H" or "L" range, a command to increase or decrease the number of operating blowers is output.

In addition, for correction of the integral control output, a hold circuit 57 for the previous holder level and a differential sampling switch 58 are used to adjust the amount of change Δ in the holder level every differential sampling period.
PV (=PVn-PVn-1) is obtained, multiplied by the polygonal characteristic of the differential gain setting circuit 59 that sets the gap/directional gain, and added to the integrating circuit 55.

The change detection period of this differential control line can be set by the differential sampling period generator 60 independently of the integral sampling period, so that level changes in processes with large time constants can be quickly detected and appropriate for the required number of blowers. It can be effectively used to apply corrections.

The control operation amount output of the integrator 55 is added as a correction value for the required number of blowers based on the gas usage amount information. That is, in the actual process, the main criterion for determining the number of operating blowers is the amount of gas used, and the output of the integrating circuit 55 is added to the number of operating blowers determined from the amount of gas used. Final increase/decrease determination circuit 61 for the number of operating blowers
given to.

To explain this operation based on the timing chart shown in Fig. 5, three units have been operated up to the time T1, the holder level is higher than the H'' level, the integral control output outputs one manipulated variable, and the differential control output also commands one operation amount, the control operation amount d decreases step by step, and at the time T2 when the three-unit operation is commanded and the bell Ll is turned off, two units are operated, and the output of the integral control is still one operation. While outputting the amount, the number of operating vehicles is reduced until time T3.

However, once the number of units in operation is reduced to one, the gas level in the gas holder will gradually decrease if the amount of gas used is large.
Then, the gas level was "H".

When the level is between "L", the integral control circuit holds the manipulated variable, continues to operate one unit, and outputs a command to increase the number of operating units even if the actual gas level is low, as long as the level is not cut to "L". do not.

When the gas level drops below the reference level at time T4, the integral control circuit outputs a command to increase the number of operating units for the first time.
Moreover, the differential control circuit also outputs a + correction, and the required operation amount d for the number of units increases, and the time T when two units start operating and the bell L2 is turned off.
Two units enter operation at time T5, and if the gas level is maintained at an even lower level, three units enter operation at time T6.

When the gas level exceeds the "L" level due to the operation of these three units, it will enter the "H" range, so a hold command is issued for the number of units in operation, and the gas level will continue to rise until the gas level exceeds the 'H' level. Machine operation will continue.

In this way, the operation amount obtained by the integral control operation is corrected by the differential control operation, and furthermore, the number of operating blowers is determined to increase or decrease based on the increase or decrease in the actual gas consumption. When the level is within the "H" and "L" ranges, the current number of operating vehicles is held without increasing or decreasing the number of operating vehicles, and only when the level deviates from the "H" and "L" ranges is integral control and proportional derivative control performed. Since the number of units in operation is controlled by increasing or decreasing the number of units in operation, accurate level control of the gas holders is realized with less frequent generation of proer start and stop commands.

[Effects of the Invention] As described above, according to the present invention, the integral control circuit and the differential control circuit are separated and the sampling period and gain are set individually. If the sampling period of the proportional-derivative control is set to match the response speed of the process, the response can be accelerated and stable control can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is a block diagram of another embodiment of the invention, Fig. 3 is an explanatory diagram explaining the operation of the above embodiment, and Fig. 4 is a block diagram of the above embodiment. FIG. 5 is a diagram illustrating the operating characteristics of the above embodiment, and FIG. 6 is a block diagram of the conventional example. 10... Integral control line 11... Subtractor 12...
- Integral gain setting circuit 13... Integral sampling switch 14... Integrating circuit 15... Adder 16...
・Sampling cycle generation circuit 20...Differential control line 21...Hold circuit 2
2...Subtractor 23...Differential sampling switch 24...Differential gain setting circuit 25...Differentiation circuit 26...Sampling period generation circuit

Claims (1)

[Scope of Claims] A gain setting circuit that sets an integral gain based on a gapped polygonal line characteristic depending on the magnitude of the deviation between a process value and a target value, an integral sampling switch that provides an integral sampling period, and an integral sampling switch that provides an integral sampling period. an integrator circuit that integrates the output and outputs an integral term manipulated variable; a proportional sampling switch that calculates the change in the process value in a sampling period different from the sampling period of the integrator circuit; and an output from the proportional sampling switch. a proportional gain setting circuit that sets a gapped directional gain for the proportional gain setting circuit, a differentiation circuit that differentiates the output of this proportional gain setting circuit and outputs a differential operation amount, and synthesizes the output of this differentiation circuit with the output of the integration circuit. A control device comprising a synthesis circuit.