JPS62522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an improvement in a process control device that controls a process by, for example, performing P.I.D adjustment.

(2) Prior art Generally, when controlling a process, a set value is set in advance, a control deviation between this set value and a measured process physical quantity (temperature, pressure, flow rate, etc.) is determined, and a quantity proportional to this control deviation is calculated. , or an amount proportional to the integral value of the control deviation over time, or an amount proportional to the change in the control deviation over time. These quantities are called control constants. These control constants P, I, and D (hereinafter expressed as P, I, and D, respectively) are set to values suitable for the process based on the dynamic characteristics of the process (time constant, dead time, etc.) determined by the operating conditions of the process. Set.

Therefore, the above control constants have conventionally been determined as follows. First, a disturbance is applied to the process to be controlled, and a noise signal optimal for the process is selected from among the disturbances, and dynamic characteristics optimal for the process are calculated based on the noise signal. (Hereinafter, this will be referred to as determining the identification value, and the calculation will be referred to as identification calculation.) This calculation is extremely complex, so it is performed using a computer or the like. Next, the control constant for the erroneous process is determined based on the identified value, and
These control constants are set manually or automatically in the process controller.

However, in processes where the amount of change in process physical quantities is large, the operating conditions of the process may change, so several types of control constants are prepared in advance, and new control constants are prepared each time the operating conditions change. Resetting variables to the process controller.

Furthermore, if new control constants are required, identification calculations are performed again based on new operating conditions. This work is performed by human judgment such as an operator.

(3) Problems with the conventional technology The conventional technology has the following problems.

Since several types of control constants are prepared to correspond to the operating conditions of the process, the ability to respond to the operating conditions is naturally limited by the number of prepared control constants, resulting in poor versatility.

In addition, since the identification calculation work causes disturbance to the process, it must be performed at the minimum necessary timing in consideration of the influence on other control systems. Therefore, it would be extremely inappropriate to do it artificially.

Furthermore, since it requires judgment on the part of workers such as operators, it is a burden and is inefficient.

(4) Purpose of the Invention The present invention provides a process control device that automatically adjusts process control constants that match the operating conditions of the process at the minimum necessary level and in a timely manner by incorporating an identification calculation function into the control loop. With the goal.

(5) Structure of the Invention A process control device having an adjustment section that detects a controlled amount of a process, compares it with a set value of the process to obtain a control deviation, and outputs an adjustment signal based on this control deviation and a set control constant. a set value change amount calculation unit that calculates the amount of change in the set value of the process and outputs a first trigger signal if the amount of change is greater than or equal to a predetermined change amount; a control deviation calculation unit that outputs a second trigger signal when the deviation is equal to or greater than a predetermined number of times; an identification calculation section that calculates an identification value, the control constant is calculated based on the identification value of the identification calculation section, and the setting of the control constant of the adjustment section is automatically corrected at a predetermined time to control the process. It is structured as follows.

(6) Embodiment of the invention The figure shows a block diagram of an embodiment of the invention. 1 is a control process indicating a controlled process, and this control process 1 is provided with a detection unit 2 that detects the controlled amount and converts it into an amount that can be compared with a set value described later. This detector 2 is connected to a set value input terminal SV into which the set value of the control process 1 is input, and a comparator 3 which compares the signal from the detector 2 with the set value and outputs a control deviation signal. is connected. Furthermore, a P.I.D adjustment section 4 is connected to this comparison section 3 and outputs a correction operation signal based on the control deviation signal using predetermined control constants (P, I, D). An operating section 5 is connected to the D adjustment section 4 for operating the control process in response to a correction operation signal.

A set value change amount calculating section 6 is connected to the set value input terminal SV, which outputs a trigger signal when the amount by which the set value is changed exceeds a predetermined amount of change. Further, a first control deviation calculation unit 7 is connected to the comparison unit 3, which outputs a trigger signal when the control deviation signal exceeds a predetermined value for n or more consecutive times. A 3-input OR circuit 8 is connected to the first control deviation calculation section 7 and the set value change amount calculation section 6, and a trigger is inputted from the outside at the desired time to the remaining input terminals of this OR circuit 8. An external trigger input terminal 9 is connected via an interface circuit 10. Further, the OR circuit 8 includes the set value change amount calculating section 6, the first
control deviation calculating section 7 and external trigger input terminal 9
An identification calculation unit 11 is connected to the identification calculation unit 11 which performs identification calculation using one of the trigger signals. Further, when the control deviation signal exceeds a predetermined value m times in a row, the comparison section 3 causes the identification calculation section 11 to stop the identification calculation and return to the initial identification value (or stop the control). .) A second control deviation calculation unit 12 that outputs a stop command signal is connected.
Then, the identification calculation section 11 has this identification calculation section 1.
a control constant calculation unit 1 that outputs a new control constant signal in order to change the preset control constant of the P・I・D adjustment unit 4 based on the identification value signal from 1;
3 is connected.

Next, the operation of the control device configured as described above will be described. First, in a normal control state, the P/I/D adjustment section 4 operates with the initially set control constants. That is, the process is controlled in a control loop of control process 1→detection section 2→comparison section 3→P.I.D adjustment section 4→operation section 5→control process 1. Next, when identification calculation is required, that is, when control constants (P, I, and D) need to be changed, the following state is assumed.

B. A state in which the change in set value exceeds a predetermined range of change.

(b) A condition in which the control deviation is greater than a predetermined value and continues for more than a set number of times (n times).

C A state in which a trigger signal is input from the external trigger input terminal.

In other words, in the case of state a), the set value input terminal
The amount of change from the initial setting value of the new set value signal input from the SV is calculated by the set value change amount calculation unit 6, and it is determined that this amount of change exceeds a predetermined amount of change. , At this time, a trigger signal is input from the set value change amount calculating section 6 to the OR circuit 8.

In the case of condition (b), the control deviation signal output from the comparison section 3 is sequentially compared with a predetermined value in the control deviation calculation section 1, and if the control deviation signal is larger than this value, the control deviation signal is output from the comparison section 3. Count the number of times (for example, the number of pulses from a built-in pulse generator),
When the number of times continues to be n or more, a trigger signal is input from the first control deviation calculating section 7 to the OR circuit 8.

In the case of state c), when the control constants of the control system are intentionally changed, for example when trying to combine with other control systems, a trigger signal is input to the OR circuit 8 manually or automatically. be done.

One or more of the trigger signals output in the above a), b), and c) are input to the identification calculation section 11 via the front OR circuit 8. Then, the identification calculation unit 11 newly applies a disturbance to the process, determines the dynamic characteristics, and calculates the identification value. This calculated identification value is input to the control constant calculating section 13, and a new control constant is calculated. This calculated control constant is
is entered and newly set. In this way, the control loop consisting of the control process 1→detection section 2→comparison section 3→P/I/D adjustment section 4→operation section 5→control process 1 is controlled by the newly set control constants. control.

In addition, if the apparent trigger signal for identification calculation is generated due to an unexpected failure of the P・I・D adjustment section 4 or the sensor (not shown) of the detection section 2, unnecessary A second control deviation calculation section 12 is connected to the comparison section 3 in order to prevent the identification calculation from destabilizing the process and the plant. The second control deviation calculation unit 12 sequentially compares the control deviation signal input from the comparison unit 3 with a predetermined value, counts the number of times the control deviation signal is larger than this value, and calculates the number of times the control deviation signal is larger than this value. When the number of times is m or more consecutively, a stop command signal is output to the identification calculation section 11. Then, the identification calculation section 11 that receives this stop command signal stops the identification calculation performed by the trigger signal output in the above-mentioned states (a), (b), and (c), and outputs an initial identification value. (or outputs a signal to stop the control), that is, the control constants are returned to their initial values, and the process enters the initial control state. (Or the control will be stopped.) Note that the present invention is not limited to the above embodiments, and can be modified in various ways without departing from the gist thereof.

(7) Effects of the Invention According to the present invention, it is possible to automatically perform process identification calculation and automatically correct the control constant of the adjustment section according to the plant conditions. In addition, by determining the timing of identification calculation according to predetermined conditions, identification calculation can be performed at the optimal timing, which improves the accuracy of correcting control constants and allows identification to be performed at the minimum necessary level and in a timely manner. Control constants can be easily corrected by calculation. In other words, it is possible to provide an extremely versatile process control device that can reduce as much as possible the unstable factors that affect processes and plants, and can easily reduce the burden on workers such as operators.

[Brief explanation of the drawing]

The figure shows a block diagram of a process control device according to the present invention. 4... P/I/D adjustment section, 6... Set value change amount calculation section, 7... First control deviation calculation section, 11...
Identification calculation unit, 12...Second control deviation calculation unit, 1
3... Control constant calculation section.

Claims (1)

[Claims] 1. An adjustment unit that adjusts the process based on a set control constant; and a set value change amount calculation unit that calculates the amount of change in the set value of the process and outputs a first trigger signal if the amount of change is greater than or equal to a predetermined amount of change. , a control deviation calculation unit that compares the control deviation value of the process with a predetermined deviation value and outputs a second trigger signal when the control deviation value of the process is equal to or greater than the predetermined deviation value for a predetermined number of times; The process is performed by an external trigger input means to be input, and one of the first trigger signal, the second trigger signal, and the third trigger signal, or both of the first trigger signal and the second trigger signal. It includes an identification calculation section that calculates an identification value, and a control constant calculation section that calculates a control constant based on the identification value signal of the identification calculation section and corrects the setting of the control constant of the adjustment section. A process control device characterized by automatically controlling a process at certain times.