Performance Analysis of a Real-Time Control Network Test Bed in a Linux-Based System With Sporadic Message Arrivals

Abstract

This paper describes the results from a real-time network test bed for a Linux-based control system with event-driven message traffic. Interest has grown in the use of Linux as a cost-effective alternative to expensive proprietary real-time operating systems. However, kernel tasks in Linux can cause random delays in message transmissions. Event-driven traffic can result in unpredictable message inter-arrival rates. Nondeterministic delays in message transmissions and sporadic message arrival times complicate the design of the network as they require the use of an estimation technique to analyze feasibility. Random temporal behavior can lead to network overloads, where it becomes unavoidable that some messages will be late. We discuss the design and feasibility analysis for the network and evaluate the network's performance in the presence of random kernel delay and sporadic message arrivals. Three message scheduling approaches are evaluated using different Linux configurations at different levels of network loading.

Real-time Ethernet networks for motion control

“…In some cases the networks employed were completely dedicated (sometimes even explicitly designed) for the NCS application as described, for example, in [23], where the authors developed a real-time closed loop control system with a sampling period of 600 ns. Conversely, other analysis, even if not specifically related to motion control systems, have taken into consideration commercially available networks [24], [25], [26], [27]. Clearly, RTE networks may be profitably employed in NCSs as well, pro-vided that a tight synchronization with the application(s) running on the controller is maintained.…”