Panjaitan, S.; Frey, G.:
Functional Design for IEC 61499 Distributed Control Systems using UML Activity Diagrams.
Proceedings of the 2005 International Conference on Instrumentation, Communications and Information Technology ICICI 2005, Bandung, Indonesia, pp.64-70, August 2005.
Achieving re-configurability and flexibility of the control software was one of the main factors that stimulated the emergence of the standard IEC 61499. The current paper is concerned with the re-configurability aspect in terms of control process within the scope of this standard of this standard as a task scheduling approach is presented as a probable solution. Task scheduling is proposed as a means of describing the process sequences of a sub-system in an effective and reconfigurable way. When orders of the processes need to be changed for a different mode of operation or even in case of total depreciation of the previous processing sequences, the changes can be actuated through task schedules. This allows re-configurability of the sub-system to be achieved during run-time without stalling the controlled operations. The task schedules can also be associated with a maximum time limit for particular task executions and this may help in monitoring the controlled hardware's actions. For the description of the schedules timing and sequence diagram of UML as well as Gantt charts are investigated. The implementation of the proposed approach on a resource-restricted hardware imposes some additional design constraints.