Abstract

Abstract

Abstract

Abstract
Controller Area Network (CAN) is a fieldbus network suitable for small-scale Distributed Computer Controlled Systems (DCCS), being appropriate for sending and receiving short real-time messages at speeds up to 1 Mbit/sec. Several studies are available on how to guarantee the real-time requirements of CAN messages, providing preruntime schedulability conditions to guarantee the real-time communication requirements of DCCS traffic. Usually, it is considered that CAN guarantees atomic multicast properties by means of its extensive error detection/signaling mechanisms. However, there are some error situations where messages can be delivered in duplicate or delivered only by a subset of the receivers, leading to inconsistencies in the supported applications. In order to prevent such inconsistencies, a middleware for reliable communication in CAN is proposed, taking advantage of CAN synchronous properties to minimize the runtime overhead. Such middleware comprises a set of atomic multicast and consolidation protocols, upon which the reliable Communication properties are guaranteed. The related timing analysis demonstrates that, in spite of the extra stack of protocols, the real-time properties of CAN are preserved since the predictability of message transfer is guaranteed.

Abstract

Abstract
In this paper, we are interested in the study and analysis of how activities are executed at the lowest level of the manufacturing networks hierarchy. At this level, a Real-Time Distributed Database (RTDD) provides a logical link between local applications. The role of the Fieldbus network is to link local sites enabling their interactions and preserving RTDD temporal and spatial consistency. Specific characteristics of Fieldbus supported RTDDs, such as a `deterministic transaction subset', allow us to introduce the `network transparency' concept, which is the basis of a proposed overall system development. An [Iso, SC5] based model is presented, providing an efficient method to describe the network transparency concept into standardized description techniques.