Visual programming expedites process control [of power stations]

Software development and maintenance costs continue to decrease as recent graphical user-interface (GUI) techniques advance. Improvement in the hardware cost-performance has also supported GUI success. In the area of modulating control for power plants, however, cost decreases have already been achieved through user-friendly forms. In the area of programmable logic controllers, there are three types of programming methods: relay ladder logic, Boolean, and high level language. Recently, the development of a programmable logic controller with the latest fashioned user interface (such as the window, icon, menu, and pointer environment on a control engineering workstation) has come on the market. Although its GUI features are quite good, it is not easy for plant engineers to use due to the various programming forms (e.g. ladder logic diagrams) which are often used. The system featured in this article has been developed and commercialized for direct digital modulating control prior to the programmable controller. The construction and maintenance tools for the system are set up in workstations and personal computers. The tool is familiar to instrument and control designers and has more GUI uses. The key to the design of this system, however, is the use of input frames containing control block diagrams, which are constructed from several standard operational elements