JPH086607A - Process controller - Google Patents

Abstract

PURPOSE:To perform control which is as precise as possible by providing an input control means and a control arithmetic means with timers and measuring the delay time of input data, and calculating a manipulated variable in consideration of the delay time together with the idle time of a process itself. CONSTITUTION:A timer 2e measures the elapsed time from the input of process data to an input control means 2 to the reception of a data input request command. A timer 6b, on the other hand, measures the elapsed time from the issue of the data input request command by a control arithmetic means 6 to the completion of the reception by the control arithmetic means 6. Then a CPU 2b when sending the process data out to the control arithmetic means 6 sends the elapsed time measured by the timer 2e out together with the process data and a CPU 6b calculates a manipulated variable on the basis of the process data in consideration of the elapsed times measured by the timers 2e and 6d. Consequently, the control which is as precise as possible can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process controller for performing input control, control calculation, and output control by distributed processing.

[0002]

2. Description of the Related Art The structure of a conventional process cotton roller is shown in FIG. This process controller has an input control means 2
And a control calculation means 6 and an output control means 8, and these means are connected by a transmission line 4. The input control means 2 has an input unit 2a, a CPU 2b, a memory 2c, and a transmission control unit 2d. The control calculation unit 6 has a transmission control unit 6a, a CPU 6b, and a memory 6c,
The output control means 8 has a transmission control unit 8a, a CPU 8b, a memory 8c, and an output unit 8d.

Next, the structure and operation of this process controller will be described. The CPU 2b of the input control means 2 outputs a sampling command at regular intervals, and based on this sampling command, process data indicating the process state of the plant is stored in the memory 2c via the input unit 2a.

On the other hand, the CPU 6b of the control calculation means 6 issues a data input request command at predetermined intervals via the transmission control section 6a and sends it to the input control means 2 via the transmission path 4. Then, the CPU 2b of the input control means 2 receives the data input request command via the transmission control unit 2d, and transfers the process data stored in the memory 2C to the transmission control unit 2d.
d, sent to the control calculation means 6 via the transmission path 4. The sent process data is written in the memory 6c via the transmission control unit 6a. Then, based on the process data written in the memory 6c, the CPU 6 calculates the operation amount data in consideration of the response delay (dead time) of the process itself.
b. This calculated operation amount is the CPU 6
It is sent to the output control means 8 via the transmission control section 6a and the transmission path 4 by b. Then, the CPU 8 of the output control means 8
In b, the operation amount data is stored in the memory 8c, and the operation amount data stored in the memory is output at a predetermined output cycle.
It is sent to the plant via d and the plant is controlled.

[0005]

As described above, in the conventional process controller, each process of input control, control calculation, and output control is distributed, and in the control calculation process, the dead time of the process itself is reduced. The amount of operation considered is required. For this reason, if the input / output processing cycle and the time required for transmission are short, no problem will occur. However, there is a problem that accurate control cannot be performed.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a process controller capable of performing control with the highest possible accuracy.

[0007]

A process controller according to the present invention takes in a first memory and process data indicating a process state of a plant in a first memory at a predetermined first cycle and issues a data input request command. Based on the first
Input control means having a first CPU for sending out the process data taken into the memory, a transmission line, and the input control means are connected by a transmission line, a second memory, and a predetermined second The data input request command is issued to the input control means at a cycle, the process data sent from the input control means is received, the received process data is taken into the second memory, and the process of the plant is processed based on the process data. The control CPU having a second CPU for calculating and outputting the operation amount data in consideration of the dead time, and the control calculator are connected by a transmission line, and the second CPU is connected.
And a third CPU for storing the manipulated variable data output from the plant, and a third CPU for sending the manipulated variable data stored in the third memory to the plant at a predetermined third cycle. In a process controller including output control means, a first timer is provided in the input control means for measuring an elapsed time from when the process data is taken into the input control means until a data input request command is received. At the same time, a second timer for measuring the elapsed time from when the data input request command is issued from the control calculation means until the control calculation means completes the reception of the process data is provided in the control calculation means, and the first CPU processes the process. When the data is sent to the control calculation means, the elapsed time measured by the first timer is sent together with the process data, and the second C
The PU is characterized in that the operation amount is calculated based on the process data in consideration of the dead time of the process and the elapsed time measured by the first and second timers.

[0008]

According to the process controller of the present invention configured as described above, when calculating the manipulated variable data, not only the dead time of the process itself but also the progress measured by the first and second timers is calculated. The time, that is, the delay time of the input data is also taken into consideration. As a result, it is possible to perform control with higher accuracy than in the conventional case. Note that the manipulated variable data is usually calculated in consideration of the delay time of the output data, but in this case, the empirically obtained data is used as the delay time of the output data.

Further, if the delay time of the output data is actually measured using a timer and the manipulated variable data is calculated also using this measured delay time, control with even better accuracy can be performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the configuration of an embodiment of a process controller according to the present invention. The process controller of this embodiment is the same as the conventional process controller shown in FIG.
The input control means 2, the control calculation means 6, and the output control means 8 are provided with a timer 2e, a timer 6d, and a timer 8d, respectively. The timer 2e counts an elapsed time t1 from when the process data is taken in by the input control means 2 until the CPU 2b of the input control means 2 receives the data input request command from the control calculation means 6. The counted elapsed time t1 is sent to the control calculating means 6 by the CPU 2b together with the process data when a data input request command is issued from the control calculating means 6. On the other hand, the timer 6d counts the elapsed time t2 from when the data input request command is sent from the control calculation means 6 until the process data is taken into the memory 6c.
The total time t1 + t2 of the elapsed times t1 and t2 is the delay time of the input data. The timer 8d counts the elapsed time t3 from the start of receiving the manipulated variable data from the control calculation means 6 to the completion of the output of the manipulated variable data from the output control means 8. This elapsed time t3 is called the delay time of the output data, and the CPU of the control calculation unit 6 is transmitted from the CPU 8b via the transmission control unit 8a, the transmission path 4, and the transmission control unit 6a.
6b. The CPU 6b takes into account the dead time of the process itself, the delay time of the input data, the delay time of the output data, and the manipulated variable at the time when the output control means 8 will output the process data stored in the memory 6c. Is calculated. The calculated manipulated variable data is immediately sent to and stored in the memory 8c via the transmission control unit 6a, the transmission path 4, and the transmission control unit 8a. Then, this manipulated variable data is sent to the plant via the output unit 8d at the next output timing.

As described above, the operation amount is calculated in consideration of not only the dead time of the process itself but also the delay time of the input data and the delay time of the output data. It can be carried out.

In the above embodiment, the delay time of the output data is used as the delay time of the output data in the calculation of the manipulated variable, but the delay time of the output data obtained up to now is used. The maximum delay time may be used to calculate the manipulated variable. Further, when the delay time of the output data is empirically known, the empirically known data is used to calculate the manipulated variable, and the timer 8e in the output control means 8 may be omitted.

If the timer 2e is set to zero and starts counting when the input value of the process data is updated, the process data stored in the memory 2c is sent to the control calculation means 6. Even after that, the timer 2e continues to count until the next sampling of process data is input. When the data input request command is sent again from the control calculation means 6 to the input control means 2 in such a state, the control calculation is performed in response to the data stored in the memory 2c, that is, the previous data input request command. The same data as the data sent to the means 6 is again sent to the control calculation means 6. However, the elapsed time t1 sent together with this data has a larger value than in the previous case. Therefore, when the timer 2e operates as described above, regarding the delay of the input value, if the elapsed time exceeds a certain time, as shown in FIG. There is no waste of carrying out the control calculation with the same input value.

The delay time of the output data can be used for the response of the process after the output or the answer check in the case of sequence control. The delay of the response of the process is a dead time and is incorporated in the control calculation means, but more accurate control can be performed by adding the delay time of the output data to the dead time. The answer back check time of the sequence processing can be accurately diagnosed by adding the delay time of the output data.

If a large disturbance does not occur, the input value does not change much, or increases or decreases at a substantially constant level. Therefore, in this embodiment, since the process input data and the elapsed time thereof (delay time of the input data) are also captured by the control calculation means 6, it is possible to predict the process input data at the present time, and this prediction is performed. The manipulated variable data may be calculated based on the obtained data.

Further, in this embodiment, the delay time of the input / output data is measured by using the timer provided in each means. However, instead of the timer, each means is provided with a clock to process the elapsed time. The time of implementation may be used as a parameter.

[0017]

According to the present invention, at least the input control means and the control operation means are provided with timers to measure the delay time of the input data, and the operation time is calculated in consideration of this delay time together with the dead time of the process itself. Therefore, it is possible to perform control with higher accuracy than in the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a process controller according to the present invention.

FIG. 2 is a timing chart illustrating effects of the embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional process controller.

[Explanation of symbols]

 2 input control means 2a input section 2b CPU 2c memory 2d transmission control section 2e timer 4 transmission path 6 control calculation means 6a transmission control section 6b CPU 6c memory 6d timer 8 output control means 8a transmission control section 8b CPU 8c memory 8d output section 8e Timer

Claims (2)

[Claims] 1. A first memory and process data indicating a process state of a plant are loaded into the first memory at a predetermined first cycle, and loaded into the first memory based on a data input request command. The first to send the collected process data
An input control unit having a CPU, a transmission line, and the input control unit are connected by the transmission line, a second memory, and the data input request command at a predetermined second cycle. Process data sent from the input control means to the second memory, the received process data is taken into the second memory, and a manipulated variable in consideration of the dead time of the process of the plant based on the process data. A second CPU that calculates and outputs data
And a third memory for storing operation amount data output from the second CPU, the third memory being connected to the control arithmetic means by the transmission path. An output control unit having a third CPU that sends the manipulated variable data stored in the plant to the plant at a predetermined third cycle, and the process controller includes: A first timer for measuring an elapsed time from the time when the data input request command is received until the time when the data input request command is issued from the control calculation device; A second timer for measuring an elapsed time until the control calculation means completes reception of the process data is provided in the control calculation means, and the first CPU is configured to process the process data. When it is sent to the control calculation means, the elapsed time measured by the first timer is sent together with the process data, and the second CPU measures the dead time of the process and the first and second timers. A process controller that calculates an operation amount based on the process data in consideration of the elapsed time. 2. A third timer for measuring an elapsed time from the start of receiving the manipulated variable data from the control calculation means to the completion of transmission to the plant is provided in the output control means.
The process controller according to claim 1, wherein the second CPU calculates the manipulated variable data in consideration of the elapsed time measured by the third time.