The object-oriented nature of ABB System 800xA makes this DCS one of the most powerful platforms for the development of process control code. Holding true to conventional object oriented programming languages, System 800xA embraces the concepts of inheritance, abstraction, and encapsulation to build hierarchical process control code that is efficient, consistent, and reusable. Unfortunately, most industrial processes are highly integrated and coordinated between control applications. This requires control modules, control diagrams, and control applications to share data across the object boundaries. System 800xA also requires all variables and parameters to be explicitly declared, and, unlike many other DCS and PLC platforms, variables are not globally available due to the object oriented nature.
The complexity of industrial processes, the segmentation of operational units, and the enforcement of explicit declaration and encapsulation combine to create development management problem. Keeping track of communication variables is difficult, particularly when developing control unit code in parallel with other team members. Spelling, abbreviation, capitalization, and a lack of variable description can create an integration nightmare when trying to integrate two or more control units. The use of structured data types for communication does not solve the problem; if a modification to a structured datatype is made, all applications utilizing that datatype must be downloaded simultaneously, or all communications within that datatype will cease. This is productivity problem during code development since not all applications using the datatype may be compilable or error free when a developer requires a download. This creates the need for programmers to be highly coordinated in their development efforts. In a live plant the problems are much more serious, the the loss of communication variables between applications can have catastrophic results on process control, resulting in lost production, quality control issues, equipment failures, injuries, death, and severe environmental impact. For most processes, forgetting to download all applications is too likely of a scenario to fit within the envelope of acceptable risk.
To resolve the development efficiency issue and live plant safety issues, CGK developed a methodology and companion communications object library that allows developers to use structured datatypes for communication (eliminating coordination, spelling, abbreviation, and capitalization errors) while safety resolving the requirement to download all applications utilizing the datatype. Developers can now work and download to virtual controllers independent of each other, and live plant communications will not cease when partial downloads are completed. Contact us to find out more about implementing the CGK communications methodology on your ABB 800xA distributed control system.