Fee ~~~~gu~a~~e unction Block in Distributed Csintrol Systems
Peter G. Neumann, René Simon · 1996
AbslrucP - The Function Block (FB) technology provides for the st~n~ard~z~~~on of the whole application process in a Distributed Control System (DCS) if common modelis and tools are agreed ad used. This pager presents a basic model of the application functions and the co-operation of its elements. It shows how this model can be applied to the different components of the DCS (e.g. in modelling a single device). ~~r~er~~ore the in~e~nat~on~ standardization process is analysed and compared with the presented model. 1. STARTING-POINT AND MBTPVATIQN Currently an intensive discussion on Function Block technology is running world-wide. It intends to create a coninion infrastructure for the operation of the automation functions which are the results of the algorithm design. The discussion includes the specification and implementation of the Function Block framework, the functions for execution and mode control of Function 13locks and Function Block networks as well as the interaction models for distributed processing. Despite of some common features the momentary use of Function Blocks in rnariufacturing and process automation differs in several aspects. In manufacturing automation, which is determined by the use of programmable logic controllers (PLC), a very fine granularity of Function Block applications is found, i.e. these Function Block applications are composed of very small basic Function Blocks (e.g. an ,,or gate). The Function Block applications are hierarchically structured and customized to the concrete application. In process automation a more gross granularity IS found, the basic Function Blocks are much more complex (e.g. a PID block with around 40 inputs and outputs). The basic Function Blocks are connected in flat structures. Although only some parts of the basic Function Block's functionality are used in a concrete application, the necessary resources (e.g. processor, memory) are working under full load.