FBM207C FOXBORO
There are still many advanced control algorithms.At present,many control software companies and DCS manufacturers both domestically and internationally are competing to develop engineering software packages for advanced control and optimized control,hoping to embed advanced control and optimized control strategies in configuration software.
When a large amount of on-site information is directly entered into the computer control system through intelligent instruments or through the field bus,there is a problem of sharing and interacting with on-site information by internal computer applications.Due to the lack of unified connection standards,industrial control software often requires the development of dedicated drivers for hardware devices.
Once the hardware device is upgraded,it is necessary to make changes to the corresponding driver program,which increases the maintenance cost of the system.Even if the SCADA in the computer has independent drivers,it is generally not allowed to access the same devices simultaneously,otherwise it is easy to cause system crashes.It can be seen that the on-site control layer,as the bottom layer of the entire enterprise information system,inevitably needs to be integrated with the process management layer and business decision-making layer.This also poses the problem of how monitoring computers communicate and transmit information with other computers.Because the control system is often a special system developed by different manufacturers,which has poor compatibility with each other,and lacks an effective communication interface with high-level commercial management software,the communication specification problem has become the bottleneck that restricts the control system from breaking through the”information silo”.
The appearance of OPC(OLE for Process Control)has established a set of communication interface specifications that meet the requirements of industrial control,so that the control software can efficiently and stably access data to hardware devices,and the application software can also flexibly exchange information,greatly improving the interoperability and adaptability of the control system
From a software perspective,OPC can be seen as a standard for a’software bus’.Firstly,it provides a channel standard for real-time data transmission between different applications(even between applications on different workstations connected through a network);Secondly,it also defines the format for transmission and exchange in channels for process control needs.The architecture of the OPC standard is a client/server model,which divides software into OPC servers and OPC clients.The OPC server provides necessary OPC data access standard interfaces;OPC customers access OPC data through this standard interface.
The software developed using the OPC standard is based on common data and interface standards,so it has strong universality with each other.This has very practical significance in the field of industrial control.OPC servers can be provided by different suppliers,and their code determines the way the server accesses physical devices,data processing,and other details.But these are all transparent to OPC client programs,and they only need to follow the same specifications or methods to read data from the server.Similarly,software suppliers only need to add OPC interfaces to their software to obtain data from OPC servers without worrying about underlying details.Through the OPC interface,OPC client programs can connect to one or more different OPC servers.At the same time,an OPC server can also be connected to multiple client programs,forming a many to many relationship.Any product that supports OPC can achieve seamless integration with the system.Due to the fact that OPC technology is based on DCOM,client programs and servers can be distributed on different hosts,forming a networked monitoring system.
