The Communication Scheme as a Key to Fulfil Hard Real-Time Constraints

4th Euromicro Workshop on Real-Time Systems, Athens, Greece, June 3-5, 1992

Ewald von Puttkamer, Christopher Wetzler & Uwe R. Zimmer

Based on experiences from an autonomous mobile robot project called MOBOT-III, we found hard realtime-constraints for the operating-system-design. ALBATROSS is "A flexible multi-tasking and realtime network-operating-system-kernel", not limited to mobile-robot-projects only, but which might be useful also wherever you have to guarantee a high reliability of a realtime-system. The focus in this article is on a communication-scheme fulfilling the demanded (hard realtime-) assurances although not implying time-delays or jitters on the critical information-channels. The central chapters discuss a locking-free shared buffer management, without the need for interrupts and a way to arrange the communication architecture in order to produce minimal protocol-overhead and short cycle-times. Most of the remaining communication-capacity (if there is any) is used for redundant transfers, increasing the reliability of the whole system. ALBATROSS is actually implemented on a multi-processor VMEbus-system.

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