JPH01266684A - Distributed control system - Google Patents

Abstract

PURPOSE:To shorten the cycle of data collection essentially without increasing the number of communication lines remarkably by providing a buffer to store data from a field equipment transiently in a control station (FCS). CONSTITUTION:A data fetch program F2 in the FCS receiving a startup request from an operator's station OPS checks whether or not the data of the field equipment F is registered in the buffer bf, and registers it newly when it is not registered. Also, when no data with the additionally designated number of data exists, all of the data in the buffer bf are transmitted to the OPS. And a trend collection program 01 in the OPS stores transmitted data in the buffer D, and supplements the data at an old side with null data when the number of data is insufficient for the designated number. Next, a trend display program 02 displays the data on a CRT. Thus, by providing the buffer bf, it is possible to contract the cycle of the data collection essentially without increasing the number of communication lines remarkably.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a distributed control system comprising a control station that receives data from field devices and an operator's station that periodically collects data from the control station. The aim is to reduce the burden of data communication between the two parties.

<Prior art> In a distributed control system such as the one described above, when displaying trend graphs, etc. at the operator's station,
The operator's station communicates with the control station, collects data from field devices, and buffers it in its own internal main memory and auxiliary memory.

<Problems to be Solved by the Invention> In the trend data collection method as described above, if an attempt is made to shorten the data collection cycle of the operator's station, the number of communications will increase and the communication load will increase.

The present invention is intended to solve such problems, and aims to substantially shorten the data collection cycle without significantly increasing the number of communications.

Means for Solving the Problems> The present invention provides a buffer for storing data from field devices on the control station side, and the outline of the invention is as follows.

That is, in a distributed control system consisting of a control station that receives data from field devices and an operator's station that periodically collects data from the control station, the data from the field devices is temporarily stored in the control station. A buffer is provided, and the operator's station specifies the number of data and a process data address in a data collection cycle and starts a data retrieval program to be added to the buffer on the control station side. the number of received data or the number of data in the buffer is transmitted to the operator's station, and when the number of received data is less than the specified number, the operator's station sequentially fills in invalid data on the older side of the time. It is a distributed control system.

Effects> In the distributed control system of the present invention, the control station stores data from field devices according to a data collection cycle. The operator's station retrieves data from the buffer in the control stage, and retrieves multiple pieces of data at a time.The interval at which the operator's station retrieves data from the control station is longer than the time when the data in the buffer in the control station is stored. Also set it short.

<Embodiment> The figure shows a configuration example of a distributed control system implementing the present invention.

In this figure, F represents field devices such as valves and thermometers, Fe2 is a control station that collects data from field devices F, B is a communication bus, and OPS has a CR7 display device and manages the entire system. This is an operator's station that also communicates with the control station FC5 to collect data and display trends.

A hardware feature of the present invention is that the control station F
This is because a buffer bf for temporarily storing data from field device F is installed in C8.

Next, the operation of the system of the present invention in which this buffer bf is installed will be explained according to the operation program set in each station.

The control station FC8 has a data collection program F1.
Accordingly, data from field device F is buffered in buffer bf every data collection cycle.

On the other hand, the operator's station OPS requests data from the control station FC3 in the following cases. That is,
At the start of trend data display, while trend data is being displayed, and when trend data is not displayed, the data collection cycle is 1 second while trend data is being displayed, and the data collection cycle is 1 second when trend data is not being displayed. The period is shorter than the time when the buffer bf in the control station FC3 becomes full, for example, one minute.

In the above three cases, Operator's Station OPS
The trend collection program 01 starts.

The trend collection program F1 calculates the number of data items that should be stored in the buffer bf after a certain period of time has passed since the previous data retrieval, and controls this data number and process data address! 7 Te'yo''/
FC8') It is given to the data retrieval program F2 to issue a startup request. A data/address correspondence table F3 is set in the control station FC8 to facilitate calls from the operator's station OPS.

Now, the data retrieval program F2, which has received a startup request from the operator's station OPS, checks whether data has already been registered in the buffer bf, and if not, newly registers it. Furthermore, if there is no data for the specified number of data, as much data as is present in the buffer bf is transmitted to the operator's station ops.

The trend collection program 01 in the operator's station OPS stores the transmitted data in buffer D. If the number of data items is less than the specified number, the old data will be supplemented with invalid data.

Next, the trend display program 02 at the operator's station displays this data as a trend on the CRT.

Here, the reason why the operator's station OPS specifies the number of data and specifies the data using the process data address from the control station FC3 is because one of the stations has a system down or the database is This takes into consideration the possibility that differences may occur between the two states due to reloading, etc.

In this way, the control station FC8III is provided with a buffer bf to temporarily store several pieces of data from the field device F, and the operator's station OPS reads this buffer bf. A large amount of data can be read out, and a predetermined number of data can be collected without increasing the number of communications between the operator's station OPS and the field control station FC8.

<Effects of the Invention> As described above, according to the distributed control system of the present invention, several pieces of data in the buffer can be exchanged between the operator's station and the field control station without significantly increasing the number of communications. Since the data can be read at once, the data collection cycle can be substantially shortened.

[Brief explanation of the drawing]

The figure is an example showing the configuration of the distributed control system of the present invention. F...Field device, Fe2...Control station, OPS...Operator's station, bf.
...Buffer, Fl...Data collection program, F
2...Data retrieval program, F3...Data/address correspondence maple, 01...Trend collection program, 02...Trend display program, D...Buffer. npc, operator tab 7;-Kobashiro

Claims (1)

[Claims] (1) In a distributed control system consisting of a control station that receives data from field devices and an operator's station that periodically collects data from the control station, the control station temporarily stores data from the field device. The operator's station specifies the number of data and the process data address in a data collection cycle, and starts a data retrieval program to be added to the buffer on the control station side. the number of received data or the number of data in the buffer is transmitted to the operator's station, and when the number of received data is less than the specified number, the operator's station sequentially fills in invalid data on the older side of the time. distributed control system.