JPH01191901A - Process controller - Google Patents

Abstract

PURPOSE:To eliminate the overshoot, etc., by controlling in steps the set value at the levels near the target value and stopping temporarily the rise or the fall of the set value before the target value to repeat the rerise and the refall of the set value. CONSTITUTION:A process is connected to a cooling water pipe and the inside of the process is controlled to a prescribed temperature by the cooling water flowing via a flow rate meter and an open/close valve. A set value controller 7 consists of a set value storage part 8, a control value setting part 8, a comparison part 10, a pulse generating part 11, a switch part 12, and a set value output part 13. The part 8 stores a set value pattern containing the final target value SV1 and SV2. Then the part 9 sets the control value alpha that decides a specific preceding percentage of the set value to be switched in steps in accordance with the process characteristics. The part 10 decides whether or not the set value under output has reached a switching time point SV1-alpha (or SV2+alpha) and gives a pulse generating command to the part 11 at the switching time point.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a process control device useful for program control of various plants such as paper pulp, cement, and chemical plants.

(Prior Art) Program control in process equipment is to control a controlled object based on programmed setting values.
Overshoot or undershoot with respect to the final target value can be prevented only by operating the controller or driver.
This is done by adjusting fiMV.

(Problem to be Solved by the Invention) However, in the conventional program control as described above, overshoot or undershoot is prevented by adjusting the operation ffiMV, so there is a problem that it takes a long time to settle. There is a problem in that it is difficult to make adjustments, and overshoot or undershoot inevitably occurs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a process control device that can improve the above-mentioned problems and suppress overshoot or undershoot with respect to the final target value as much as possible.

(Structure of the Invention) (Means for Solving the Problems) The present invention solves the above problems, in a process control device that controls a process control target by operating a controller based on a set value given in advance. The present invention is characterized by the provision of set value adjusting means for adjusting the set value stepwise around the final target value.

(Function) In the present invention, the set value is adjusted stepwise around the target value,
After the set value is temporarily stopped rising or falling before reaching the target value, it is repeatedly raised or lowered again, so even if overshoot or undershoot occurs at each step on the controller or driver side, The debt can be reduced to a very small amount.

(Embodiment) FIG. 1 is an explanatory diagram of the configuration of a temperature control device as an embodiment of the present invention.

As shown in the figure, process 1 shown in this example is connected to a cooling water pipe, and the inside thereof is controlled to a predetermined temperature by cooling water flowing in through a flow meter 2 and an on-off valve 3. ing.

A thermocouple 4 is disposed in the process 1, and the temperature detected by the thermocouple 4 is fed back to the temperature controller 5.The temperature controller 4 also has a flow mIQ controller. 6 is connected, and the controller 6 controls the opening control valve 3 so that the flow ff1Q detected by the flow mountain needle 2 becomes a predetermined value.

In particular, in this example, a set value regulator 7 is connected to the temperature controller 5.

As shown in FIG. 2, the set value regulator 7 includes a set value storage section 8, an adjustment m setting section 9, a comparison section 10, a pulse generation section 11, a switching section 12, and a set value output section. It consists of 13.

The set value storage section 8 stores a set value pattern having the final target value SV+ and SV2.

The adjustment amount setting section 9 determines what percentage of the final target value SV+, SV2.
The adjustment amount α that determines whether to switch stepwise from the previous set value is set according to the characteristics of the process, and in this embodiment, the stepwise switch is performed from the set value 10% before.

The comparator 10 determines that the setting value currently being output is at the switching time SV+
-α (or SV2+α>) is determined. When the switching time point is reached, a pulse generation command is output to the pulse generation section 11.

In response to the pulse generation command, the pulse generation section 11 generates a pulse train signal having a frequency according to the characteristics of the process to the switching section 1.
Output to 2.

The switching section 12 is provided between the set value storage section 8 and the set value output section 13, and switches the intercept 12a according to the cycle each time the pulse train signal arrives. In other words,
The intercept 12 a is normally in contact with the set value output side 12 b and supplies the set value stored in the set value storage section 8 to the set value output section 13 . Further, when a pulse arrives, the segment 12a switches to the set value holding side 12c to hold the current set value for a time corresponding to the pulse width.

The set value output section 13 outputs the set values adjusted stepwise before the final target value SV+ and SV2 to the temperature regulator 5 via the switching section 12 as described above.

Then, the temperature controller 5 outputs a command for setting a predetermined flow rate to the flow rate controller 6 based on the adjusted set value (temperature set value).

In the above configuration, in the set value adjuster 7, after the initially set set value is adjusted stepwise around the final target value,
The temperature controller 5 is controlled based on this adjusted set value and overshoot or undershoot is absorbed for each step, so that almost no overshoot or undershoot occurs for the final target values 'SV+ and SV2.

Therefore, as shown in FIG. 3, in the control amount characteristic A (broken line in the figure) for the conventional set value, the final target value SVI
An overshoot (undershoot) exceeding (SV2) is observed, and it takes a long time for this to settle; however, as in this example, the final target value SVI
When the set value is adjusted stepwise on the near side of (SV2), almost no overshoot (undershoot) occurs in the controlled variable characteristic B (-dotted chain line in the figure), and the settling time is short. This makes it possible to stabilize the control.

Although the present embodiment has been described above as an example of temperature control using cooling water, the same applies to temperature control using a heater or other process control.

Note that the present invention is not limited to the above-mentioned embodiments, but can be implemented in other embodiments by making appropriate design changes.

〔Effect of the invention〕

As described above, the present invention can perform process control using stepped set values near the final target value, thereby suppressing overshoots and undershoots with respect to the final target value as much as possible, resulting in a stable process. Can be controlled.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the configuration of a set value adjuster, and Fig. 3 is an explanatory diagram showing the set value and operation amount before and after adjustment on the same graph. be.

Claims (1)

[Claims] In a process control device that controls a process control target by operating a controller based on a set value given in advance, a set value adjustment that adjusts the set value stepwise around a final target value. A process control device characterized by being provided with means.