1 Overview
OLE for process control - OLE for process control is an industrial standard, which is the world's leading automation and soft, hardware companies and Microsoft's cooperation. This standard defines how to use the Microsoft operating system to exchange automated real-time data between PC-based clients. Organizations to manage this standard are OPC Foundation. The foundation of the foundation is more than 220 worlds. Including almost all of the world's control systems, instrumentation and process control systems are main suppliers. The Pioneer of the OPC Foundation-A "Special Working Group" consisting of Fisher-Rosemount, Rockwell Software, Opto 22, Intellution, and Intuitive Technology, developed a basic and operational operation after a year of work OPC specification. The standard of the simplified first phase was released in August 1996.
With the introduction of the DCOM technology supported by Windows 95 in February 1997, the newly established OPC Foundation in September 1997 revised the OPC specification, adding some standards such as data access, and the OPC specification has been further improved. OPC is based on Microsoft's Distributed Internet Application (DNA) architecture and Component Object Model (COM) technology, which is designed according to easy scalability. The OPC specification defines an industrial standard interface, which makes COM technology to apply applications such as process control and manufacturing automation. OPC is a communication standard for an OLE / COM mechanism as an application. OLE / COM is a customer / server mode with the advantages of language independence, code reuse, and easy integration. The OPC specifies the interface function, regardless of the form of on-site equipment, customers access to a unified manner, ensuring the transparency of the software to the customer, so that the user is completely detached from the low-level development.
2. Traditional process control system structure
The traditional process control system is a one-to-one system, any HMI or other upper monitoring software or other application software (such as trend software, data reporting and analysis, etc.) requires a dedicated driver when using some hardware devices. . As shown below:
Figure 1 Traditional process control system structure
The final result of the system build is:
1 software needs to develop N drivers using N-class hardware devices; M * N drivers need to develop M * N drivers using N hardware devices; each additional new application needs to develop N hardware devices Driver; each additional new hardware devices need to develop new device drivers for M software;
In the example shown above, three application systems completed by four control devices require 3 * 4 = 12 drivers. New application software or hardware devices will only grow rapidly in the type of driver.
3. Process control system structure based on OPC technology
Process control system based on OPC technology can perfectly solve the above problems of traditional methods. The basic system structure is shown below:
Figure 2 Process control system structure based on OPC
Any device only needs to provide a driver for any software system, and the end result after the system build is:
M Software To use N-class hardware devices, only N drivers are required. Each additional 1 new application does not require another development of hardware devices; each additional new hardware device only needs to develop a driver for 1 new device;
In the example shown above, three applications completed by the four control devices require only four drivers. New application software or hardware devices can easily extend your system.
Since the OPC specification is based on OLE / COM technology, the OLE / COM extension remote OLE automation and DCOM technical support TCP / IP and other network protocols, OPC customers can be physically separated, distributed to different nodes of networks.
