Reducing the Priority Inversion of CAN Communications by Scheduling Messages at the Outgoing Queue

摘要

Due to the increased availability of low cost network technology, the use of networks to interconnect sensors, actuators and controllers is now widely accepted for the implementation of feedback control systems. To ensure the correct behaviour of such a system, the communication network must provide a reliable and timely communication service. The components with the highest impact on the communication delays are the Medium Access Control (MAC) protocol and the local communication stack. Therefore, an adequate communication stack is of utmost importance to guarantee the timing correctness of the feedback control application. In this paper, we propose the use of state-of-the-art scheduling algorithms to manage the outgoing queue of the local communication stacks. We demonstrate that it is possible to improve the responsiveness of applications supported by the CAN communication protocol, by using just a light scheduling middleware to adequately schedule each of the outgoing queues. We also show that implementing such middleware even on top of COTS communication hardware permits a substantial reduction in the occurrence of priority inversions in the communication medium, and therefore a decrease in the number of deadline misses for highly loaded network scenarios.