PROCESS CONTROL: WHAT TO DO WITH THE LEGACY?

摘要

Many aspects of computer control of chemical plants are currently dominated by the desktop computer industry. Operator workstations are normally "commodity" PCs running one of the flavours of MS Windows. Communication between nodes is by Ethernet. System set-up is done in a Windows Explorer-like environment. There are data links to Excel and Web servers using "OLE" or "OPC". Windows is even being mooted as the operating system for control. During the evolution of the technology over the past 40 years the relative proportions of "proprietary" and "standard" components, both hardware and software, have fluctuated constantly. The suppliers have made use of resources such as Intel and Motorola chips, DEC PDP-series computers, and a variety of operating systems such as CP/M, VMS, and DOS. Early systems were often based on general-purpose mini-computers running special code. Some suppliers, however, made their own computers. This was the early pioneering period when so-called "Direct Digital Control" of valve positions and drive states was thought rather bold.