Interconnecting Smart Sensors through Low-Level Fieldbuses to Intranet/Internet

smart sensor, fieldbus, IEEE 1451

Industrial distributed computer-based systems typically encompass, at their lowest level, various digital actuator/sensor-to-controller connections. Those connections, usually based on low-level fieldbuses, constitute the bottom, vendor-dependent segments of hierarchical communication systems that include higher-level fieldbus or LAN backbones and, more recently, an access to and from Intranets/Internet. Hence, the systems must comprise suitable interconnections of incident higher and lower fieldbus segments, which intermediate not only top-down commands and bottom-up responses but also remote system management. The first part of this contribution dedicates attention to the multiple fieldbus interconnecting architectures that fit hierarchical structures with sensors on low-level segments. A special case of the previous problem appears connecting a fieldbus to an Intranet. While for the majority of high-level fieldbuses the solutions are commercially available, they offer, as a rule, a proprietary approach. Similarly to fieldbus-to-fieldbus coupling, it is possible only to map the broad variety of concepts applicable to fieldbus-to-Intranet interconnections. Current industry is migrating away from proprietary hardware and software platforms mentioned above in favor of open and standardized approaches. Internet technologies such as Java, WWW, TCP/IP, and also Ethernet are rapidly becoming the platforms of choice for building next generation distributed measurement and control systems. The second considered framework, which can support the current trend, is the IEEE 1451 smart transducer interface architecture that enables to unify not only interconnecting smart sensors with various fieldbuses but also direct coupling to the Ethernet-based Intranet. The proposed standards include an object-oriented information model targeting software-based, network independent, transducer application environments with a standard digital interface and a communication protocol for accessing sensors and actuators. The case study deals with the real application of a pressure analyzer consisting of a group of smart pressure sensors interconnected by the Ethernet-based Intranet with supporting nodes, enabling also to join to components on various fieldbuses. The complete research task has been aimed at application-driven pressure measurement processes and tools starting with the study of various physical principles and designs of transducers up to the final data processing implementation including internal and external data communications.