| Cyber-Physical System (CPS) is a kind of novel intelligent complex system with the integration and collaboration of computing, communication and controlling technologies. In CPS, one of most important requirements is to guarantee the data transmitted from the physical world to all interested entities real-time and reliably. From this perspective, CPS can be seen as a data-centric data distribution service system. DDS (Data Distribution Service) is a data-centric data exchange specification for real-time application proposed by OMG, and has a good support for the dynamic and real-time of data. However, providing reliable and timely data dissemination services is especially challenging for CPS since they often operate in highly unpredictable environments, so DDS can not be used into CPS perfectly.In order to make DDS adapt into CPS deeply, in this paper, Data-Centric Publish-Subscribe model of DDS is improved from real-time, reliability and credibility in the unstable environment, and then proposes CPS-DDS model. Firstly, in the CPS-DDS model, this paper proposes a continuous data transmission mechanism, which can reduce the overhead of computation and communication, while ensuring the system’s real-time on slow or unstable network. Secondly, we use the double loop control strategy to control the accuracy threshold dynamically, and then guarantee the QoS/QoD, and enhance reliability of the system. Thirdly, we ensure the credibility and privacy of data by using the key infrastructure.Finally, we carry out experiments by using the CPS-DDS prototype. First, we verify the feasibility of the continuous data transmission mechanism. Then, through the contrast experiment with OpenDDS, confirmed that the continuous data transmission mechanism can effectively reduce the computation and communication load. Lastly, we test the adaptive ability of CPS-DDS under both stable and unstable environment, and concluded that CPS-DDS system has robustness in an unstable environment. |
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