JP2015141644A - Data collection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve conventional problems that an excessive communication load is imposed on a control line 105 and a control system is possibly made unstable as a whole if an OPC-DA client transmits a request to acquire process data to an OPC-DA server 107 at arbitrary timing and the OPC server executes the request of the process data on a process controller at the arbitrary timing as it is.SOLUTION: A process controller sequentially executes process input, control computation, and process output in a control cycle. After the process output, process data is multicast on a control line, whereby an OPC-DA server can acquire the process data in each control cycle at a low load. While loads on the line and each piece of equipment can be alleviated, real-time performance depends on the control cycle. Furthermore, it is possible to ensure the acquisition of data for which the process output is confirmed since control computation and process input-output processes cannot be interrupted.

Description

The present invention relates to a data collection device. For example, process control equipment that performs feedback control, sequence control, process state monitoring, etc., an OPC-DA server connected to the control line of the process control apparatus, and process data of the process control apparatus from the information line via the OPC-DA server The present invention relates to a process monitoring control system configured by a host device including an OPC-DA client that collects data.

  In plant facilities, standardization of interfaces of devices and equipment is promoted, and a system hierarchy as shown in FIG. 1 is generally achieved. That is, field devices such as the transmitter 101 and the control valve 102 are connected to the field bus 103 to form a field layer. The process operation monitoring console 106 and the OPC-DA server 107 connected to the process control device 104 via the control line 105 constitute a distributed control system layer. In the production management layer, an information line 110 connecting the production management system 108 and the OPC-DA client 109 and the distributed control system layer constitutes the production management layer.

  OPC-DA is formulated as a process data access specification, and is mainly used as a standard interface for connecting the production management layer and the distributed control system layer. In FIG. 1, the OPC-DA server 107 is arranged in the distributed control system layer, and relays process data of the process control device 104 to the OPC-DA client 109 without passing through the control monitoring device. The function of the OPC-DA server can be included in the process operation monitoring console.

  The production management system can obtain and set data of the distributed control system layer from the OPC-DA client, but the OPC-DA client itself can also be included in the production management system.

The OPC-DA server 107 and the process control device 104 are connected by a control line 105. The OPC-DA server is required to have a function of collecting process data of the process control device at a constant period and acquiring process data from the process control device 104 in response to a request from the OPC-DA client 109.

JP-A-11-327630

  The OPC-DA client requests the OPC-DA server 107 to acquire process data at an arbitrary timing. If the OPC server makes a process data request to the process control apparatus at an arbitrary timing, there is a possibility that an excessive communication load is generated on the control line 105 and the entire control system becomes unstable.

Furthermore, considering that the process control device processes the data collection request during the control calculation, it is necessary to trade off whether to respond to the process data in the middle of the calculation or to wait for the data response until the calculation is completed. .

The above problems are solved by the configurations described in the claims. Specifically, for example, the process control device multicasts process data onto the control line at the end of each control period. The OPC-DA server that has received the multicast stores the received process data in the memory buffer. At the time of a request from the OPC-DA client, the process data in the memory buffer is returned to suppress the load on the control line and the process control device.

  According to the present invention, in a control system including a process control device and an OPC-DA server / client, the OPC-DA server collects process data stored in the process control device in synchronization with a control cycle under a low load. can do.

Further, the request of the OPC-DA client is processed by the OPC-DA server, which contributes to the stability of the entire control system without imposing a load on the control line or the process control device.

Hierarchical diagram of system including OPC-DA server and client Process data flow diagram Communication processing time using the conventional method Communication processing time according to this embodiment

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 2 shows a flow of process data from the process control device to the OPC-DA client via the OPC-DA server.

  The control system shown in FIG. 2 includes process control apparatuses 201 and 202, OPC-DA servers 203 and 204, a control line 105 connecting the process control apparatus and the OPC-DA server, OPC-DA clients 206 and 207, and an OPC-DA server. The information line 110 is connected to a client.

  For the hardware of the control line 105 and the information line 110, for example, a standardized network such as Ethernet (registered trademark, trademark holder: Fuji Xerox Co., Ltd.) is used, connection type peer-to-peer communication using TCP communication and connectionless communication using UDP Type multicast communication is possible.

  The process control apparatus 201 sequentially executes a process input 207, a calculation 208, a process output 209, and a multicast process 210 at predetermined control cycles (for example, 1 second).

  In the multicast processing 210, process data 211 on the process control device 201 is transmitted to the control line 105.

  The process data 212 multicasted on the control line is received by the OPC server 203, the OPC server 204, and the process control apparatus 202. The multicast communication 212 is not performed by a request from the OPC-DA server.

  When the OPC-DA server 203 receives the process data, it stores it in the memory buffer 213 secured in advance. The memory buffer 213 determines an area and address for each process control apparatus, and the process data of the process control apparatus 202 is stored in an area different from the process control apparatus 201.

  By performing the same processing in the OPC-DA server 204, the process data of the process control devices 201 and 202 can be collected in the memory buffer of the OPC-DA server every control cycle.

  Patent Document 1 describes a method in which a PLC periodically transmits data by making a request from an OPS having a built-in OPC server in a system in which a PLC and an OPC server are connected. Since the process control apparatus actively performs multicasting of process data at the start of the control operation, a request from the OPC server is not necessary. Further, in Patent Document 1, process data registered in a group is a collection target. However, in the present invention, since all process data on the process control apparatus is transmitted, the communication load of the control line is equal to the number of request data. Do not depend.

  The process data stored in the memory buffer on the OPC-DA server can be transmitted to the OPC client (214). Further, since the process data is multicast, it is also stored in another OPC-DA server 204. Even when the OPC client 207 is added later, process data can be collected without increasing the load on the control line.

  There are two types of transmission methods to the client: a method of transmitting the response data after receiving a request from the client, and a method of transmitting at a period set by the client.

  FIG. 3 and FIG. 4 show that the loads on the control line 105 and the process control apparatus 201 are constant regardless of the method of the process data communication 214 between the OPC-DA server and the OPC-DA client.

  FIG. 3 shows the communication processing time according to the conventional method. The horizontal axis indicates the processing time unit, and in either case of reception or transmission, it is 1 unit time. Two units of time are required for reception and transmission. In the figure, data transmission / reception is performed twice. The OPC-DA client sends a data request to the OPC-DA server. The OPC-DA server requests process data from the process control device through the control line.

  When receiving the request, the process control device transmits the corresponding process data to the OPC server. When the OPC-DA server receives the process data, it relays it to the OPC-DA client. This process is performed twice.

  In FIG. 3, the waiting time of the OPC-DA client requires 16 unit hours, the OPC-DA server requires 12 unit hours, and the process control apparatus requires 4 unit hours.

  Furthermore, when the process control apparatus is executing the calculation process (208) in FIG. 2, a trade-off is required between whether the calculation process is completed or the process data being calculated is responded.

  FIG. 4 shows the communication processing time according to the present invention. The process control device 104 multicasts process data to the OPC-DA server in synchronization with the control cycle. Since multicast is performed in synchronization with the control of the process control apparatus itself, processing can be performed in one unit time. Since the OPC server does not need to issue a request, it can be processed in one unit time only for reception.

  When there is a request from the OPC client, the OPC server responds with the process data in the memory buffer. This process is performed twice.

  In FIG. 4, the waiting time of the OPC-DA client is 8 unit hours, the OPC-DA server is 6 unit hours, and the process control device is 2 unit hours.

Compared with the conventional method, the OPC-DA client, the OPC-DA server, and the process control device can be shortened to a processing time of 50%. In FIGS. 3 and 4, when the number of data exchanges on the control line is counted, the conventional method is 4 times and the present invention is 2 times, and the load on the communication line can be reduced by 50%.

DESCRIPTION OF SYMBOLS 101 Transmitter 102 Control valve 103 Fieldbus 104 Process control device 105 Control line 106 Operation console 107 OPC-DA server 108 Production management system 109 OPC-DA client 110 Information line

201 Process control device 1
202 Process control device 2
203 OPC-DA server 1
204 OPC-DA server 2
205 OPC-DA client 1
206 OPC-DA client 2
207 Process input process 208 Arithmetic process 209 Process output process 210 Multicast process 211 Process data 212 on the process control device 212 Multicast process data 213 Memory buffer 214 Transmission to OPC-DA client

Claims (4)

A process operation monitoring console having a processing device, a display device, and a key input device; a process control monitoring device having a processing device and a process input / output interface; a communication line connecting the two; In a data collection method executed by a process monitoring control system comprising an OPC-DA server and an OPC-DA client connected as communication devices,
A data collection method characterized in that the OPC-DA server collects process data from a process control device without delay while reducing the communication load of the communication line and maintaining process data consistency. In claim 1,
The process control device transmits process data which is a control calculation result to a communication line;
A data collection method characterized by In claim 1,
The OPC-DA server acquires process data from the communication line;
A data collection method characterized by A process control device for controlling the process of the equipment in the plant;
An OPC-DA server for storing process data transmitted from the process control device;
An OPC-DA client that requests and obtains process data from the OPC-DA server;
With
The process control device transmits the process data obtained in the control cycle to the OPC-DA server for each control cycle,
The OPC-DA server, when there is a request for process data from the OPC-DA client, transmits the process data obtained in the latest control cycle transmitted from the process control device to the OPC-DA client.
Process monitoring and control system characterized by