Embedded systems are suffering a radical transformation in many aspects. Ancient isolated real-time applications are being interconnected by wireless (WIFI or the new802.15.4 standards) and traditional wired technologies, resulting in a new generation of distributed real-time applications that expand to a great variety of domains.
The revolution does not seem constrained to any particular field: military, information, surveillance, and even conservative industrial systems may benefit from the technological revolution.
However, the new generation of embedded distributed systems challenges current infrastructures also. In many cases, it must deliver end-to-end real-time performance and offer also an acceptable quality-of-service (QoS) in open systems which must interact at some point with humans. Other systems have batteries that must be preserved over the time, introducing new constraints in the algorithms and models that rule their behavior.
One global technology that may speed the adoption of these new principles in industrial systems is Java. In an industrial environment, Java can be used as a “lingua franca” to fight against heterogeneity stemmed from having different kinds of operating systems and processing infrastructures.
Other advantages stem from the availability of additional programming interfaces for other domains. So far, Java addressed systems that range from the tiny 802.15.4 motes (like SPOT tech to large application servers .
Java also offers support for real-time and embedded systems, with commercial products that implement RTSJ (The Real-Time Specification for Java) and promising specifications like DRTSJ (The Distributed Real-Time Specification for Java) that target distributed environments.
Together with other technologies such as JINI (i.e., a fault-tolerant discovery framework) and DDS (Data-Distribution Service), they form the base of a rather realistic Java-centric approach that eases the development, deployment, and maintenance of next generation industrial applications.
Unfortunately, real-time Java is a recent technology and itsintegration in other Java systems, especially those that expand current real-time Java horizons, requires additional exploration and integration decisions.
Some of these technologies, like JINI or DDS, lack a clear characterization of the implications that the use of a real-time Java virtual machine is going to have on its interfaces and the changes they require on its current model to profit from the predictability of a real-time Java virtual machine. In other cases, like in DRTSJ, the interfaces were defined and implementations are under development.
This article extends the current practice by introducing a real-time Java-centric architecture for industrial systems. The architecture integrates existing and upcoming technology to define a Java-based approach.
It is a three layer architecture, with each one related to a particular network whichinterconnects the different elements. The high-level network is the business network (BN), which interconnects general purpose elements (i.e. mail servers, data bases and file servers) to the Internet.
The second layer – general purpose real-time networks (GPRTN) – interconnects special nodes in charge of providing interconnection to different factory floor elements and different industrial services like real-time databases. It is also in charge of controlling the data that are sent from the floor elements to the Internet (devices are not directly connected to the business system; all information should flow via the industrial layer before being sent to the Internet).
Lastly, at the third level are machine and sensor networks (DMSN), which are specific to a particular industrial environment (e.g. Profibus, Wireless HART and other wired/wireless networks), provide access to control devices.
The empirical evidence, included in the article, illustrates the performance of the core of the industrial layer of this architecture.
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