JPS61224008A - Sample value pi controlling device - Google Patents

Abstract

PURPOSE:To cope with disturbance that occurred in the middle of a controlling operational period by providing a disturbance detecting device and executing propotional integrating operation forcibly for a fixed time when the output of the device is generated. CONSTITUTION:A disturbance detecting device 404 watches upper limit, lower limit, amount of deviation and rate of change of measured values PV, and transmits a forcible operation command signal PA when one of then exceeded allowable values. When the timing of the signal PA is out of operating time in a controlling operation period, a signal PL for executing operation by the timing rises up, and make a PI (proportional integration) operating device 402 execute operation forcibly. The detection of disturbance is executed at a fixed period at a period quicker than a period of controlling operation, and when the new disturbance is found after the next detection period, the forcible operation similar to the above-mentioned is executed. Thus, the controlling characteristic of the controlling device can be improved additionally.

Description

[Detailed description of the invention] <Industrial application field> Concerning improvement of control characteristics.

<Prior art> In the figure, 1 is a pipe through which process fluid F flows, 2 is a flow rate sensor, Pv is a flow rate measurement value output, 3 is a flow rate control valve,
MY is the operation output of the control valve, and 4 is the sample P! It is a control device. In terms of functional blocks, this control device 4 includes a deviation calculation means 401 that calculates the deviation between the measured value pv and the control target value sp, and a deviation calculating means 401 that calculates the deviation 1 by proportional integration at a constant calculation period and transmits an operation output. PI calculation means, timing means 403 for supplying the timing signal PL for sample control to this calculation means, ! : The operation output path can be maintained at the operation output based on the previous operation except during the period when the control operation is being executed.

FIG. 5 is an explanatory diagram of the operation, and (4) shows the waveform of the timing signal PL, which takes the form of a repetitive pulse signal having a calculation period T and a calculation time τ. (B) is a waveform diagram showing changes in the measured value pv with respect to the control target value sp, and (C) is a waveform of the manipulated output MY that is transmitted by proportional integral calculation of the deviation for τ time every period τ.

Sample value P! has traditionally been used as a control algorithm for control loops with large dead time and time constants. Although it has been proven theoretically and empirically that the control is effective, the operation output based on the previous calculation is retained during the calculation cycle, so if a disturbance occurs during this period, the Since the correction is made to wait until the timing of the next calculation, the correction operation is delayed and the control amount deviates greatly from the target value, creating a problem.

Figure 5 shows this situation. Even if a disturbance occurs at t1 in the middle of the calculation cycle and the measured value pv deviates significantly from sp, causing a large sense of deviation, this corrective action will not be performed until the next calculation cycle. The calculation timing t2t is delayed, and during this period the control amount continues to be largely deviated from the target value, which may have a very serious adverse effect depending on the type of process.

<Problems to be Solved by the Invention> An object of the present invention is to solve the above-mentioned problems and to provide a sample value P that can be handled even when a disturbance occurs in the middle of a control calculation cycle.
Means for Solving the Problems in Providing an I Adjustment Device The structural feature of the present invention is that the deviation between the measured value and the control target value is A sample value PI that executes a proportional-integral calculation and transmits a manipulated output, and holds that manipulated output until the next control calculation cycle at times other than the above.
The control device is provided with means for detecting the occurrence of a disturbance, and means for forcibly executing the proportional-integral calculation for a certain period of time and transmitting an operation output when the output of the means is generated.

When it is detected that a disturbance has occurred in the middle of the control cycle, a predetermined proportional-integral calculation is immediately executed for the deviation at the timing of this detection, and an operation is performed to make the control l match the target value. Output is emitted. After that, the control shifts to a steady cycle.

<Example> An example will be described with reference to the functional block diagram shown in FIG. Components that are the same as those in FIG. 4 are given the same reference numerals and their explanations will be omitted.

4G4 is the disturbance detection means and is the upper limit of the measured value pv.

The lower limit, the size and rate of change of the deviation S are monitored, and when any of them exceeds the allowable value, a compulsory calculation command signal PA is sent. If the timing of this signal PA falls outside the calculation time τ within the control calculation cycle T, the signal PL for executing the calculation at that timing rises, P! Arithmetic means 402 r
Forcibly make the c operation an executable expression. After t1, the routine returns to the normal control calculation cycle. Disturbance detection is periodically executed at a faster cycle than the control calculation cycle T, and if a new disturbance is discovered after the next detection cycle, a forced computation similar to the above is executed.

FIG. 2 is an explanatory diagram of the operation. When a disturbance is detected at time t1, which is before the normal time T in the previous calculation cycle, the calculation command signal PA is generated as shown in (b), and
The time calculation is immediately executed at the timing tl, the operation output side is updated, and the disturbance is controlled in a direction that immediately converges.

FIG. 3 is a flowchart showing the outline of signal processing when the functions shown in FIG. 1 are realized in software by means using a computer.

It is executed every disturbance detection period, and if the calculation is not being executed at the timing when the disturbance occurs, the calculation is executed immediately, the timer for determining the control calculation period is reset, and the operation output MY is updated and held.

In the present invention, the objects of disturbance detection are not limited to measured values and deviations as in the above embodiments, but are measurable disturbances that have a harmful effect on the process! Needless to say, it includes all the elements.

Furthermore, in the embodiment, the control cycle after the forced computation is performed is the normal control cycle T, but it is also possible to make the control cycle T constant independently of the timing of the forced computation due to the occurrence of a disturbance. It is.

Effect> As explained above, according to the present invention, a predetermined proportional-integral calculation can be executed immediately in response to a disturbance occurring in the middle of a control calculation cycle, so that the sample value P! The control characteristics of the control device can be further improved, and its range of application can be expanded.

[Brief explanation of drawings]

Fig. 1 is a functional block diagram showing one embodiment of the present invention;
3 is a flowchart showing the procedure of signal processing, FIG. 4 is a functional block diagram showing an example of a conventional device, and FIG. 5 is a diagram explaining the operation. DESCRIPTION OF SYMBOLS 1... Fluid pipe line, 2... Flow rate sensor, 3... Control valve, 4... Control device, 401... Deviation calculation means, 4
02... PI calculation means, 403... Timing means, 404... Disturbance detection means. Agent Patent Attorney Shinsuke OzawaFigure 3

Claims (1)

[Claims] Executes proportional-integral calculation on the deviation between the measured value and the control target value for a certain period of time every certain control calculation cycle and transmits the manipulated output, and after the above-mentioned certain time, the manipulated output is held until the next control calculation cycle. A sample value PI control device that is equipped with a means for detecting the occurrence of a disturbance, and a means for forcibly executing the above proportional-integral calculation for a certain period of time and transmitting a manipulated output when the output of the means is generated. PI control device.