JPS62219009A - Process controller - Google Patents

Abstract

PURPOSE:To use a relatively small-sized computer to raise an accurate alarm by operating a maximum estimated value and an estimated time of arrival at a limit value of a state variable or the like in an arithmetic part. CONSTITUTION:An arithmetic part 1 defines an estimated quadratic curve used to estimate one state variable or the like (y) as y(t)=at<2>+bt+c and generates a set of ternary symultaneous equations where (a)-(c) are unknown numbers on a basis of a state variable or the like y0 at a current time t0 and state variables or the like y1 and y2 at past times t1 and t2 and solves them to determine uniquely the estimated quadratic curve and obtains a maximum estimated value ym. An estimated time td of arrival at the limit value is obtained in accordance with a preliminarily set limit value yd, and an estimated time DELTAt of arrival at the limit value is obtained. The first comparing part 2 outputs binary signal '1' if the maximum forecasted value ym is larger than the estimated time td, and the second comparing part 3 outputs binary signal '1' if the estimated value DELTAt is equal to or shorter than a preliminarily set time tau. An alarm signal generating part 4 consists of an AND circuit to which output signals of the first and second comparing parts 2 and 3 are inputted, and the output is outputted to a display part.

Description

[Detailed Description of the Invention] [Summary] In a process control device, the controlled object is brought into a dangerous state based on the maximum value of the state quantity obtained from the predicted quadratic curve and the time until the state quantity reaches a preset limit value. It is configured to warn the operator before reaching the target.

[Industrial application field]

The present invention relates to a computer-based process control device.

A process control device is a control device that controls processes such as heat treatment and chemical treatment that are included in various processes in the manufacturing industry.
The operation amount to obtain a desired output is determined from state quantities such as composition and output, and the controlled object is controlled based on this.

Generally, in a control system that includes a process control device and a controlled object, the amount of operation given from the process control device to the controlled object, the state of the controlled object, etc. 3 quantities (when the state quantity cannot be directly measured, the output of an observer that reproduces the state quantity from the manipulated variable and output).

It goes without saying that limit values are set for and outputs (hereinafter collectively referred to as state quantities, etc.) to prevent danger, and control is performed so that the state quantities, etc. do not reach the limit values.

However, just in case, it is necessary to issue an accurate warning if it is anticipated that a state quantity or the like will exceed a limit value.

[Problems to be solved by conventional technology and the invention] If the characteristics of the controlled object are known, future values can be predicted from the current values of state quantities, etc., and based on this, a warning can be issued to prevent danger. I can do it.

However, when it comes to large-scale control objects, In addition to having a large number of elements such as 3N, the characteristics are extremely complex, including nonlinear elements. For this reason, large-scale computers are required to predict future values. Another problem is that calculations take a long time, for example, it takes 5 minutes to predict one minute of light.

Furthermore, if the characteristics are unclear, it is difficult to predict future values, so there is a problem that accurate warnings cannot be issued.

That is, an object of the present invention is to make it possible to issue accurate warnings for danger prevention by using a relatively small computer.

[Means for solving problems]

FIG. 1 shows a diagram of the principle of the process control device according to the present invention.

That is, the calculation section 1, the first comparison section 2, and the second comparison section 3
and an alarm signal generation section 4. First, in the calculation section 1, a prediction quadratic curve is generated for predicting the future value of the state quantity, etc., from the current value of the state quantity, etc. of the controlled object and two past values. From the obtained predicted quadratic curve, the predicted maximum value of the state quantity, etc., ie, the predicted maximum value Y m +, and the time until the state quantity, etc. reach the preset limit value ya, ie, the predicted limit value arrival time Δt. Calculate.

Next, the first comparison unit 2 converts the predicted maximum value y1 obtained by the calculation unit 1 into a limit value ya of a preset state quantity, etc.
, while the second comparison section 3.

The predicted limit value arrival time Δt is compared with a preset time τ, and an alarm signal is generated from the alarm signal generation unit 4 based on the comparison results in the first comparison unit 2 and the second comparison unit 3.

[Effect]

In general, state quantities, etc. show complex changes, but for short periods of time, or partially, they can be considered as part of a quadratic curve, and this quadratic curve is uniquely defined by the current value and two past values of the state quantity, etc. Determined.

The calculation for calculating the predicted maximum value y and the time Δt until the state quantity etc. reach the limit value ya from the obtained predicted quadratic curve is the former, that is, the calculation of the predicted quadratic curve is a three-dimensional simultaneous -
The latter operation is to solve a quadratic equation, and both can be done in a short time using a relatively small computer.

〔Example〕

FIG. 2 shows an embodiment using a block diagram.

The control unit 5 controls the target value set from the outside and the output and output fed back from the controlled object 6. The amount of operation to be applied to the controlled object 6 is determined based on the three quantities, and the controlled object 6 is controlled based on this.

Note that state quantities that cannot be directly measured are:

The output of an observer (not shown) that reproduces the state quantity from the output and the manipulated variable is used.

The calculation unit 1 calculates a prediction quadratic curve for predicting one state quantity etc. y (t) = a t 2 + b t + c
−−−−−−−−−−−−−−−−−−−−(1)
Let, the state quantity etc. y0 at the current time t0 and the past time 1. and state quantity equal y at t2.

From y2 and y2, a three-dimensional simultaneous equation (2) with a, b, and c as unknowns is created and solved to uniquely determine the predicted quadratic curve of equation (1).

That is, let the obtained solutions be A, B, and C.

The predicted quadratic curve is.

It is expressed as y(t)=A t2 +B t +C-----------(5).

Next, find the differential value of the right side of equation (5), and from the equation with this as O, the time t, ffl when the state quantity etc. becomes maximum or minimum
By finding and substituting this into equation (5).

Find the predicted maximum value y1.

Also, assuming that the preset limit value is ya, y = A t2
+]3 t +C----1・----1----
--- Solve (6), find the predicted limit value arrival time td as the smaller solution, and find the predicted limit value arrival time Δt from this.

The first comparison unit 2 compares the predicted maximum value 3'm obtained by the calculation unit 1 with a preset limit value yt of a state quantity, etc., and when )'vn>3'd, a binary signal "1" is generated. ” is output.

On the other hand, the second comparison unit 3 calculates the predicted limit value arrival time Δt
is compared with a preset time τ, and when Δt≦τ, a binary signal “1” is output.

The alarm signal generating section 4 is constituted by an AND circuit which receives the output signal of the first comparison section 2 and the output signal of the second comparison section 3 as input, and the output is sent to the character display device/audio via the display section 7. This is communicated to the operator through output devices, alarm lamps, alarm sounds, etc.

If the solution to equation (6) is an imaginary number, )'m ku)', L.

This is a case where it is predicted that a dangerous situation will not occur.

The above prediction is performed for each state quantity etc. that requires an alarm.

Note that the calculation section 1 can be constructed at low cost, such as by using a microprocessor, but it can also be included in the control section 5.

If the alarm prediction time is short compared to the reaction speed of the controlled object, time-sharing processing can be performed using a microprocessor, and the system can be configured with one calculation unit 1.

〔Effect of the invention〕

As explained above, according to the present invention, an accurate alarm signal can be generated by using a relatively small computer such as a microprocessor, and the entire control system including the controlled object can be prevented from becoming in a dangerous state. can be prevented.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the principle of the present invention. FIG. 2 is a block diagram of the embodiment. In the figure. 1 is the calculation section, 2 is the first comparison section. 3 indicates the second comparison section, and 4 indicates the alarm signal generation section. Figure 1 Figure 2

Claims (1)

[Claims] A predicted quadratic curve obtained by generating a predicted quadratic curve that predicts a future value of a state quantity from a current value and two past values of a state quantity of a controlled object including a manipulated variable and an output. an arithmetic unit (1) that calculates a predicted maximum value of a state quantity predicted from and a predicted limit value reaching time until the state quantity reaches a preset limit value; A first comparison section (2) that compares the predicted time to reach the limit value, a second comparison section (3) that compares the predicted time to reach the limit value with a preset time, and a comparison result of the first comparison section (2) and a second comparison section. Comparison part (3
1. A process control device comprising: an alarm signal generating section (4) that generates an alarm signal based on a comparison result obtained by (4).