Graphical Development of Software for Programmable Logic Controllers

Graphical languages are standard in the field of computer programming. Complex software development is best handled by graphically connecting pre-built, fully tested and highly specialized software components, instead of writing and debugging thousands of lines of code. Modern programming environments include complete libraries of such components. In the field of Programmable Logic Controllers (PLCs), this is not the case. PLC programs can be developed using graphical languages, as Ladder Diagrams (LD) or Function Block Diagrams (FBD), but the standard libraries are very limited, so the programmer must develop his own libraries, building software objects from scratch. In this paper, a framework is presented for automatically building complex software modules using based on two key pillars: on the one hand, using object oriented concepts as encapsulation, inheritance and generic programming, and, in the other one, closely following the physical model of the objects used in building electrical control cabinets (ECBs).