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In this paper, a coordinated scheduling strategy is proposed to reduce end-to-end response time in distributed control systems based on the CAN (controller area network). For the strategy, the analysis of practical end-to-end response time in the worst case is performed priory with considering real-time multi-task operating systems. The end-to-end response time is composed of response time in real-time multi-task scheduling of the operating systems, response time in the CAN communications, and delay caused by asynchronous timing between the operating systems and the CAN communications. The coordinated scheduling strategy is focused on the reduction of the delay caused by asynchronous timing between operating systems and network communications. An online deadline assignment strategy is proposed for the coordination. In the strategy, periods are defined as hard deadlines, and the deadlines of the DMS (deadline monotonic scheduling) are defined as soft deadlines with online assignments for the coordination. The performance enhancement with the coordinated scheduling strategy is validated through simulation tests, by performance comparison between a system with the proposed coordinated scheduling strategy and the system without the coordinated scheduling strategy.
Date of Conference: 28 Sept.-2 Oct. 2004