Research And Design Of Real-Time Scheduling Of Node Operating System For Cyber Physical System

With the rapid development of computing, communication, control and other 3C technology, the physical world which human is survival for is moving in the direction of network and information technology and the cyber-physical system has become a new trend in the global information technology and industrial development. CPS that focuses on the close integration and coordination of computing resources and physical resources, needs to complete the perception, interconnect and feedback functions dynamic, reliably and in real-time. As a core part of CPS, scheduling system is the key module. How to design a scheduling strategy to meet the requirements of CPS attribute, is a new challenge for existing theories and technology of CPS.Based on the analysis of existing node operating systems’ scheduling mechanisms and characteristics, and considering the features of the node operating systems which are real-time, dynamic, openness, predictability and low overhead, this thesis presents a hierarchical scheduling framework and designs the BWI-RIP scheduling policy. This strategy which does not need to know task-related information in advance, can schedule hybrid tasks with multiple time demands, and can address the issues of shared resources, such as resource competition.Firstly, based on the node operating systems’ features, we model on the scheduling system and give the definitions, task model and resource model of the system. Secondly, in-depth study on the basis of the existing framework and considering of existing a variety of task time requirements in this system, this thesis creates a hierarchical scheduling framework, which can schedule soft real-time and hard real-time tasks together and also have good scalability. The OS scheduler of this framework uses the EDF algorithm scheduling servers in the bottom, and the servers with a certain percentage of CPU time schedule a set of tasks and provide resources services. Then, according to the characteristics of CPS scheduling, this thesis analyzes the deficiencies of existing static scheduling algorithms when scheduling various types of tasks and accessing shared resources that need to know the information of the tasks in advance. Again, on the basis of the framework, we design the bandwidth inheritance protocol (BWI) which combines the constant bandwidth server and priority inheritance protocol. This strategy not only can schedule hard real-time and soft real-time tasks together, but also can solve the priority inversion phenomenon. Meanwhile, this thesis makes a combination of BWI and resource isolation mechanism (PIP), this hybrid scheduling strategy solves the problem that hard real-time tasks may miss their deadline. Furthermore, for the properties, this thesis makes a schedulability analysis, and theoretically proves that this strategy can ensure the real-time performance of the system. Finally, through experimental evaluation comparison, it turns out proving that the hybrid scheduling strategy designed in this thesis basically meets the design goals and needs of CPS Node Operating System. It has the value of further research and can be used in real application.