JPH02201501A - Variably set value controller - Google Patents

Abstract

PURPOSE:To operate a process without stopping the correcting operation at the time of entrance of a set value into a dead zone by preventing the control output from being kept at the value as it is by balance between a process signal and the set value at the time of entrance of the process signal into the dead zone of a dead zone element. CONSTITUTION:When a set value 25 of a setter 14 is gradually reduced to enter into the dead zone of a square root extracting computing element 11, a signal 122 goes to '0', and an output signal 123 goes to '0' after the set time of a delay reset circuit 103, and an output signal 124 of an AND circuit 101 goes to '0' also, and thereby, a proportional integral computing element 13 is manually operated. At this time, a signal 121 is selected as a signal 125 because a switching circuit 105 is connected to a setter 106, and preliminarily set '0%' of the setter 106 is tracked by the computing element 13, and thereby, an output 26 is 0%, and a control valve is completely closed. Thus, though a flow rate enters into the dead zone, a phenomenon that the correcting operation does not function is eliminated when the actual flow rate is not zero.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a control device with variable set values.

[Conventional technology]

Conventionally, a typical control device is as shown in FIG. The operation when the set value changes in Figure 3 is shown in Figure 4.
As shown in the figure. A flow control device will be explained as an example. Generally, in the case of a flow rate control system, the differential pressure is measured at the orifice 3, this one word is subjected to square root calculation in the calculation 11, and the set value of the setting device 14 is compared with the deviation calculator 12 to determine the deviation from the set value. 23 is calculated, proportional integration is performed by the proportional integral calculator 13, and a control signal 28 for operating the control valve 2 is output. Note that 15 is an operating device that generates a control signal 28 based on a signal 26. Since flow rate measurement using the orifice 3 has poor accuracy in a low flow rate range, a dead zone is generally provided in the computing unit 11.

When the set value is set to zero in the control system shown in FIG.
becomes zero, and the output of the proportional integral calculator 13 (control output 2B)
is the value t at that time, and the set value is actually zero,
Even though the flow rate is small, the correction operation no longer occurs (section A in FIG. 4).

[Problem that the invention seeks to solve]

With conventional technology, when the set value becomes zero as described above,
When the flow rate falls within the dead zone, an event occurs in which the corrective action does not work even though the actual flow rate is flowing, and the flow rate remains flowing.

The present invention aims to solve such problems.

[Means to solve the problem]

In the present invention, there is provided a means for determining that the set value has entered the dead zone of the process signal, a means for setting the control output to a certain value based on this determination, and a means for determining that the set value has gone outside the dead zone of the process signal. The above-mentioned problem is solved by a control device that includes means for determining and means for returning control to automatic control based on this determination.

[Effect]

With this configuration, when it is determined that the set value is within the dead zone of the process signal, the control output is set to a certain value to prevent the process value from remaining, and furthermore, the set value is set within the dead zone of the process signal. When you go outside, the control can be returned to automatic again by determining this again.

〔Example〕

When the present invention is applied to the conventional control system shown in Fig. 3,
This will be explained with reference to FIG. FIG. 2 shows the operation in this case. Devices that are the same as those in FIG. 3 are designated by the same reference numerals. In the present invention, a determiner 104 is coupled to the output of the setter 14, and sets the value of the dead zone of the square root calculator 1, and when the set value 25 of the setter 14 is outside the dead zone, the value of the dead zone is set. The signal 122 becomes @1''.

Now, when the set value gradually decreases and enters the dead zone of the square root calculator 11, this signal 122 becomes "0", passes through the delay recovery circuit 103 and the delay circuit 102, and is output after the set time of the circuit 103. The signal 123 becomes "0", and the output signal 124 of the AND circuit 101 also becomes "0"5, whereby the proportional-integral calculator 13 becomes manual. At this time, the signal 125 is selected as the signal 121 because the switching circuit 105 is connected to the setter 106, and the preset "0" of the setter 106 is tracked by the calculator 13.

As a result, the output signal 26 becomes O, and the control valve 2 becomes fully closed.

Next, when the set value increases gradually, when the set value goes outside the dead band, the signal 122 of the 1 determiner 104 becomes "1", the output signal 123 of the delay circuit 102 becomes "1" after the set time, and the signal 124 also becomes "1". It becomes “1”. As a result, after the signal at 125 is switched from 105 to 29, the arithmetic unit 13 becomes automatic and the signal at 26°28 becomes an automatic control signal.

〔Effect of the invention〕

As described above, in the present invention, in a control device that includes a dead zone element in a process signal and further varies a set value, when the set value falls within the dead zone, the process can be operated without stopping the correction operation. can do.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a control device according to an embodiment of the present invention, and FIG. 2 is an operational diagram when the present invention is applied. FIG. 3 is a configuration diagram of a conventional flow rate control device. FIG. 4 shows an operation diagram of a conventional device. Figure 1

Claims (1)

[Claims] Due to problems with signal accuracy, it is necessary to include a dead band element in the process signal, and in a control system where the set value is variable, there is a means to determine when the set value has reached a minute value, and a means for determining when the dead zone has entered the dead zone using this determination means. A means for setting the control signal to a certain value based on the determination result of the dead band element is provided, and when the process signal enters the dead zone of the dead zone element, the process signal and the set value are balanced and the control output remains at the same value. A control device characterized in that it is not held in place.