JPS5854407B2 - Batch process control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a batch process control method.

More specifically, the present invention relates to a method for accurately terminating a batch operation.

In controlling a batch process, it is often done to observe the integrated value of measurement signals when a certain control operation is started, and to end the control operation when this integrated value reaches a predetermined value.

When a computer is used as a control device, observation of the integrated value is performed intermittently at regular intervals due to its time-sharing operation, so observation may not be performed exactly when the integrated value reaches the set value. .

For this reason, when observation comes around, the integrated value may already have exceeded the set value.

Since the computer ends the control operation only at this time, the time at which the operation ends is delayed, and the integrated value of the measurement signal also deviates from the set value.

In order to solve this problem, it is possible to shorten the integrated value observation period to reduce the delay in the end of the operation and the difference between the integrated value and the set value, but if the observation period is shortened, the calculation This is not desirable as it increases the burden on

Conventionally, the instantaneous value of the measurement signal is observed at an appropriate fixed period, and this value is subtracted from the set value each time, and when only a small amount remains, the observation period is shortened to increase the accuracy of the end point.

However, in that case, there are two calculation programs, one for regular use and one for high speed.
Furthermore, as the cycle is shortened, the number of subtractions increases, so the set value remaining amount must be converted accordingly, and the shortened cycle must be accurately maintained.

An object of the present invention is to provide a method for accurately completing a batch operation without shortening the observation cycle.

In the method of the present invention, when the integrated value reaches close to the set value, the end time of the batch operation is predicted based on the difference, and the batch operation is ended at the predicted time.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a conceptual block diagram of a batch process control device to which the present invention is applied, and FIG. 2 is an explanatory diagram of its operation.

3 is a more detailed configuration diagram of the computer 1 and the interface 2, and FIG. 4 is a flow diagram of a program for implementing the present invention. In FIG. 3 and an integrated flowmeter 4 to control the injection of fluid into the tank 5.

The valve 3 is opened according to a command from the computer 1, and the injection of fluid is started.

The injection amount is cumulatively measured by the cumulative flow meter 4, and the computer 1 reads the cumulative value at a constant period TM.

The reading cycle TM is determined to an extent that does not impose a large burden on the computer 1.

The computer 1 also processes a large number of input/output signals (not shown) in a time-sharing manner.

The details of the usurpation of computer 1, interface, and chair 2 can be found in Part 3.
It is as shown in the figure.

That is, the computer 1 has a processor CPU and a main computer.
The memory MM and the timer TIM are interconnected by a data bus BS, and an interface 2 is connected to the bus BS of the computer 1.

The processor CPU operates according to the programs and data stored in the main memory MM,
It is designed to process various data for process control.

Of the data stored in the main memory MM, only those necessary for explaining the present invention are shown: S is the set value of the integrated flow rate, △ is a constant value for correcting the set value S, and S
Mn is the latest accumulated flow rate measurement value read by the processor CPU, SMn-1 is the accumulated flow rate measurement value read last time, and TM is the reading cycle of the accumulated flow rate.

The interface 2 operates according to instructions from the processor CPU, takes in the measured value of the integrated flowmeter 4, supplies a control signal to the valve 3, and exchanges signals with other operation terminals or detection terminals (not shown).

As the injection progresses, the measured value of the integrated flow meter 4 changes almost linearly as shown in a in Figure 2, and the input signal obtained by the computer 1 by reading this at a constant cycle is as shown in the figure. Changes in a step-like manner.

A set value S for the integrated value is provided inside the computer 1, and a value obtained by subtracting a constant value Δ from this set value S is used as a reference value for determining the valve closing point.

The constant value Δ is an integrated value of the flow rate from when the valve 3 starts to close until it is completely closed when the valve is closed.

Therefore, when the integrated value of the flow rate reaches the reference value S-Δ, the valve 3 is closed.

Note that △ may be ignored depending on the case.

Every time the calculator 1 reads the measured value SMn of the integrating flowmeter 4, it calculates the difference between the reference value S-△ and the measured value SMn, and the difference between the measured value SMn and the previous measured value SMn-1. Compare size.

The difference between the reference value S-△ and the measured value SMn represents the gap between the current integrated flow rate value and the reference value, and the difference between the measured value SMn and the previous measured value SMn-1 represents the integrated value per cycle. Represents the increase in flow rate.

Therefore, since the integrated flow rate will not reach the reference value even if the periodic fluid is allowed to flow, the computer 1 maintains the opening degree of the valve 3 at the current state until the next observation point.

In contrast, since it is predicted that the integrated flow rate will reach the reference value during the next cycle, the opening degree of the valve 3 is maintained at the current level for the time expressed by the following equation and then closed.

:3) The time T given by the formula is the predicted time for the integrated flow rate to reach the reference value.

The predicted time T is set in a timer, and when the time is up, the computer 1 closes the valve 3.

The fluid flows roughly by Δ until the valve 3 is completely closed, and the integrated flow rate matches the set value S.

Therefore, at the next observation, it is detected that the integrated flow rate matches the set value, and the batch end is notified.

Such operations are performed by a program as shown in FIG.

In Figure 4, BTCH is the name of the program,
When controlling a batch process, the processor CPU executes this program at regular intervals TM.

In this program, step 1 is the measurement of the integrated flow f
This is the step of determining whether WSMn matches the set value S. If a match is determined here, the process branches to step 8, performs batch end processing, and exits to return.

If they do not match, branch to step 2 to determine whether the gap between the current cumulative flow measurement value and the reference value is greater than the increase in cumulative flow per cycle; if so, Branching to step 3, the previous integrated flow rate measurement value S
Mn-1 is updated with the current accumulated flow rate measurement value SMn and exits to return.

If it is determined in step 2 that the gap between the current cumulative flow rate measurement value and the reference value is not greater than the increase in cumulative flow rate per period, the process branches to step 4, and step (3) is performed.
The time TR is determined by the formula, and in step 5, this time TR is set in the timer TIM in FIG. 3, and in step 6, the timer TIM is set.
Wait for the IM time-up, and when the time-up occurs, a command to close valve 3 is output at step 7, and the process exits to return.

If the present invention is not used, the valve is not closed at the predicted time T, so the cumulative flow rate exceeds the set value at time n+1, and this is detected and valve 3 is closed, but the cumulative flow rate is not the set value. Karakake becomes something separate.

The maximum error in the cumulative flow rate is the increase in the cumulative flow rate per observation period.

As described above, according to the present invention, batch operations can be accurately completed without shortening the observation cycle.

Since it does not shorten the observation period, it does not place a large burden on the computer.

Also, since we do not provide two observation periods, there is no need to provide two processing programs with different speeds.
Moreover, no conversion program is required.

However, although a calculation program for the predicted time is required, the calculation is simple so the program does not become complicated.

[Brief explanation of the drawing]

Fig. 1 is a conceptual block diagram of a batch process control device to which the present invention is applied, Fig. 2 is an explanatory diagram of operation, Fig. 3 is a detailed block diagram of the device in Fig. 1, and Fig. 4 is a diagram of the present invention. It is a flow diagram of a program when implementing. 1...11 machines, 2-=- interface,
3... Valve, 4... Integral flow meter, 5...
····tank.

Claims (1)

[Claims] 1. A method for controlling by computer a batch process that is to be controlled until the cumulative value of a controlled variable matches a desired set value, the method comprising controlling the cumulative value of the controlled variable at a constant period TM. Obtain the measured value SM of the integrated value of the controlled variable by monitoring, and find the difference between the latest measured value SMn and the set value S, and this difference is the change ΔSMn in the measured value SM per monitoring period TM. When the difference is smaller than the change △SMn, the control operation is continued as it is, and when the difference is smaller than the change △SMn, the control operation is maintained as it is for the time TR=TM(S-8Mn)/△sMn of the following equation, and then control is performed. Batch process control method for termination.