Quality management of real-time data in cyber-physical systems
Jiantao Wang · 2013
This thesis investigates how to manage the quality of real-time data in a cyberphysical system. We present intensive theoretical analysis and extensive performance evaluation of the designed algorithms. The major work is outlined as follows. Temporal data consistency is very important in cyber-physical systems. A cyberphysical system is a system featuring a tight combination of, and coordination between, the system’s computational and physical elements. In a cyber-physical system, the update tasks that aim at updating real-time data always have transmission delays or jitters from the sources to the destinations. In Chapter 2, we present how to maintain the temporal consistency of real-time data when different types of jitters are taken into consideration. We first present a novel algorithm to guarantee the temporal consistency of real-time data when the jitter of each update task has a limited bound. Based on the novel algorithm, an enhanced algorithm is presented to provide statistical temporal consistency of real-time data when the jitter of each update task is unbounded and unpredictable. Performance evaluation shows that both algorithms can provide good temporal data consistency when different kinds of jitters are considered. Maintaining the temporal consistency of real-time data has a close relationship with meeting the deadlines of control tasks. Unfortunately, these two goals, maintaining temporal data consistency and meeting the control tasks’ deadlines, conflict with each other and are difficult to be achieved at the same time. To address the conflict, in Chapter 3, we present a fixed priority co-scheduling algorithm. It uses periodic update tasks to maintain the temporal consistency of real-time data. It judiciously decides the priority order among all the update tasks and control tasks