Using a planning scheduler to improve the flexibility of real-time fieldbus networks

• Type: Article in International Scientific Journal
• Date: 1999

Authors

Luis Almeida (Author) Other; Pasadas, R (Author) Other; Fonseca, JA (Author) Other

Journal

Title: Control Engineering Practice

Vol. 7

Pages: 101-108

ISSN: 0967-0661

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 21 Citations

Scopus - 21 Citations

Other information

Authenticus ID: P-001-5GC

DOI: 10.1016/s0967-0661(98)00143-9

Abstract (EN): A typical approach to real-time fieldbus arbitration is to use an off-line scheduler that generates a cyclic static table containing the allocation of bus-time-slots to the transaction of process-control variables. This approach, e.g, as used in the Factory Instrumentation Protocol fieldbus, is rather inflexible in the sense that any system changes, such as the addition of a sensor, requires an interruption of the fieldbus operation. In this paper the use of a planning scheduler is proposed to overcome such inflexibility. This scheduler compromises between the advantages and disadvantages of typical dynamic and static scheduling A sufficient schedulability condition is also derived, in order to overcome the typical inability of dynamic (or even planning) schedulers to guarantee schedulability for long-term system operation. The evaluation of this condition incurs very small run time overhead, and can therefore be used with advantage in a fieldbus system that relies on the planning scheduler. An experimental test is described, to illustrate how the planning scheduler works.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8