A Scheduling Method Based on Deadline for CAN-based Networked Control Systems

In order to satisfy timeliness of messages and improve system´s flexibility in networked control systems (NCS) based on controller area network (CAN), a distributed dynamic message scheduling method based on deadline of message (DM) was proposed. In this method, provided that a message is successfully transmitted, transmission requirement of the next message immediately occurs in the same node. If only a node obtains a chance of sending message, the message can be successfully transmitted to the destination. Identifier of message is dynamically changed in this method, the change does rely on elapsed time (since the preceding message can be transmitted) and the DM. The longer the elapsed time is or the shorter DM is, the higher priority level of message is. When the DM satisfies a certain condition, the method can guarantee that all messages are transmitted within given DM and fairly allocate network bandwidth to message streams. Nodes using this scheduling method also have high flexibility. A necessary condition of full schedulability of messages is obtained and the condition is proved, some examples verify its correctness