JP3110818B2 - Process control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process control system comprising a controller having a control function and an input / output device for performing input / output processing (I / O processing) of signals to / from the process equipment. About.

[0002]

2. Description of the Related Art Conventionally, in general, among process control devices,
FIG. 3 shows a configuration of a process control system including a controller having a control function and an input / output device for performing I / O processing. That is, a controller 1 for executing a control program for controlling a process device, performing arithmetic processing necessary for controlling the process device, and controlling and managing the entire system, and a signal for the process device for each process device. Input / output (I / O) device for controlling input / output of
Are connected by an input / output (I / O) bus 3. Then, the controller 1 collects input data of each I / O device 2 via the I / O bus 3,
A control operation is performed to determine an output value. On the contrary, the output value is sent to the I / O device 2 via the I / O bus 3 and is output from the I / O device 2 to the corresponding process equipment.

In such a conventional process control system, when a failure occurs in the controller 1 and the process cannot be controlled, or when the I / O bus 3
Causes an error in the controller 1 and each I / O device 2,
When the communication with the I / O devices 2, 2,... Cannot be performed, the output values of the I / O devices 2, 2,. And it was.

[0004]

However, in such a conventional process control system, as described above, a failure occurs in the controller or a failure occurs in the I / O bus, and the controller and each I / O device are connected to each other. In the event that communication between the devices is interrupted and control becomes impossible, control is stopped and emergency intervention by the operator is required, which places a heavy burden on the operator for monitoring the process control system. There was a point.

[0005] The present invention has been made in view of such a conventional problem, and an input / output device (I / O device) (I / O) by the controller due to a failure of the controller or a failure of the I / O bus. If the control of the (/ O device) becomes impossible, the control of the process equipment can be continued on the I / O device side in order to prevent the control from stopping and the operator's urgent intervention is required, thereby reducing the burden on the operator. It is an object to provide a process control system that can be mitigated.

[0006]

According to the present invention, there is provided a process control comprising a controller for performing a process control operation, and an input / output device connected to the controller for performing input / output control of signals with process equipment. In the system, a process value (PV) is periodically read from a process device to the input / output device when the controller is normal, and a set value (SV) and an operation value (MV) are received from the controller. PID simulation means for calculating PID parameters from SV, PV, and MV values; storage means for storing the SV values and the PID parameters calculated by the PID simulation means; Reads SV and PID parameters stored in storage means Performs PID operation, is provided with a local PID control means for outputting to the process equipment in search of MV.

[0007]

[0008]

In the process control system of the present invention, the PID simulation means provided on the input / output device side periodically reads the process value (PV) from the process equipment when the controller is normal and sets the set value (SV) from the controller. ) And the operation value (MV), and using the auto-tuning function to calculate P
The ID parameter is calculated, and the PID parameter is stored in the storage unit together with the SV value from the controller.
The PID simulation calculation and the storage of the PID parameter and the value of the SV are updated at regular intervals.

When any abnormality occurs in the controller and communication with the input / output device cannot be performed, the SV value and the PID parameter stored in the storage device are stored by the local PID control means on the input / output device side. Is read, the MV is obtained by performing a PID operation, and this is output to the process equipment, so that the PID control is continued on the input / output device side.

In this way, even if an abnormality occurs on the controller side, the control is not immediately stopped and the necessity of an emergency operation by the operator is reduced.

[0011]

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a functional block diagram of an embodiment of the present invention. A controller 1 generally used in the prior art is connected to the controller 1 via an input / output bus (I / O bus) 3. Input / output device (I / O device) 2
The input / output device 2 includes an input unit 21 for receiving an input signal and a process value PV from a process device, an output unit 22 for outputting an operation value MV and other output signals to the process device, and a controller 1 A transmission unit 23 for transmitting and receiving data to and from the I / O bus 3, an arithmetic processing unit (CPU) 24 for performing control, control arithmetic processing, and input / output processing of the apparatus itself, and a control arithmetic operation performed by the CPU 24 ROM 25 for storing programs for processing, input / output processing, and other fixed data;
Data such as SV and MV sent from the side, input unit 2
RAM 26 for storing PV input via the PC 1 and PID parameter data obtained by the CPU 24, etc.
It has.

Next, the operation of the process control system having the above configuration will be described.

FIG. 2 shows a flowchart of the operation procedure performed by the CPU 24. The process according to this operation procedure is
This is performed by the CPU 24 according to a program stored in the ROM 25.

First, an input signal is fetched from the input unit 21 and
The PV is calculated and stored in a file on the RAM 26. At the same time, this PV data is transmitted to the I / O
It is provided to the bus 3 and transferred to the controller 1 (step S1).

Subsequently, it is determined whether or not the controller 1 is normal.
Manipulated variable MV from process value PV received from I / O device 2
Is calculated and transmitted to the I / O device 2 through the I / O bus 3 and the transmission unit 23. At this time, the set value SV
Is also sent to the I / O device 2. CPU 24 of I / O device 2
Converts the MV and SV sent from the controller 1 into RA
Register in the file on M26 and simultaneously output MV to output unit 22
(Steps S2 and S2)
3).

After that, the SV2, PV, and MV read the ROM2
5 according to the control operation program stored in
Simulation operation (that is, identifying the PID control system)
That operation) is performed, the input SV, output to PV MV
PID parameter that gives
26 is registered in the file.

In this way, when the controller 1 is normal and the data transmission between the respective I / O devices 2 is normal via the I / O bus 3, the I / O devices controller 1 by the auto-tuning function is a two-side
Calculating PID parameters as MV are obtained to provide the
Then , the parameter data is stored together with the latest set value SV, process value PV, and operation value MV.
26 is always updated to the latest data (step S
4).

If data cannot be exchanged between the controller 1 and the I / O device 2 due to an error in the controller 1 or an error in the I / O bus 3, the CPU 24 1 (steps S1 and S2), the CPU 24 detects the abnormality, and reads the program file stored in the ROM 25.
PID parameters stored in LE and RAM 26, S
The PID calculation according to the control calculation program is performed from the V value to calculate the manipulated variable MV (step S5), the obtained MV is output from the output unit 22 to the outside, and the control of the process device is continued (step S6).

The PID parameters stored in the RAM 26 by the I / O device 2 are adjusted by the auto-tuning function for each operation and are always set to the latest values.

As described above, in the process control system of this embodiment, the host controller 1 generally performs more complicated calculations than simple PID control calculations. Although it is difficult for the I / O device 2 to transmit, the PID control system is identified by the auto-tuning function when the host controller 1 is normal, and as a result, the operation amount MV obtained by the controller 1 is approximated. Then, a PID parameter for outputting the MV to be output is obtained and stored in the RAM 26.

When the controller 1 is normal,
Since the value of the PID parameter is always finely adjusted by the auto tuning function , the controller 1
, The control operation on the own card side, that is, the transition to the local PID control operation can be smoothly performed.

Further, when a failure occurs in the controller 1, the output value is fixed in the conventional system, but in the method of the present invention, the loop control is continued by the control arithmetic function incorporated therein. MV
It is possible to prevent a dangerous situation in which the value is fixed.

Further, since the auto-tuning function can be operated even during the execution of the local control, the parameters can be finely adjusted, and a more secure backup function can be provided.

It should be noted that the present invention is not limited to the above-described embodiment. In some cases, it is desired to execute a fixed value output of the MV rather than to continue the control when the controller goes down. Therefore, a function of selecting whether to execute the local control or to output the fixed value can be added. Furthermore, by periodically loading all the parameters required for the control operation into the I / O device, a local PID for backup of the I / O device is provided.
Control can be performed.

[0027]

As described above, according to the present invention, the manipulated variable MV obtained as a result of the PID control operation performed by the controller when the controller is normal is controlled by the input / output process value PV and the setting set by the controller. Value SV
The PID parameter for providing these SV, PV, and MV is periodically calculated and stored by an auto tuning function , and when an abnormality occurs in the controller, the local PID control means reads the PID parameter. The PID control is read out, the manipulated variable MV for the process input value PV is obtained by PID control calculation, and this is output to the process device, so that the PID control can be continued. This eliminates the need for an emergency operation by the operator and does not place an excessive burden on the operator.

[0028]

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment.

FIG. 3 is a block diagram of a general process control system.

[Explanation of symbols]

 Reference Signs List 1 controller 2 input / output device (I / O device) 3 input / output bus (I / O bus) 21 input unit 22 output unit 23 transmission unit 24 arithmetic processing unit (CPU) 25 ROM 26 RAM

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G05B 1/00-7/04 G05B 11/00-11/60 G05B 13/00-13/04 G05B 17/00-17 / 02 G05B 21/00-21/02

Claims (1)

(57) [Claims] 1. A process control system comprising: a controller for performing a process control operation; and an input / output device connected to the controller for performing input / output control of a signal with a process device. When the controller is normal, the process value (PV) is periodically read from the process equipment, and the set value (SV) and the operation value (MV) are received from the controller.
PID for calculating PID parameters from PV and MV values
Simulating means and storing the value of the SV,
Storage means for storing the PID parameters calculated by the PID simulation means, and when the controller is abnormal, the SV and PID parameters stored in the storage means are read and PID calculation is performed, and MV is obtained and output to the process equipment. A process control system including local PID control means.