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2005 : Extending CORBA for Hard-Real Time Systems

Thomas Losert
Today, the usage of distributed real-time systems is state of the art for solving control problems, e.g., chemical plant or automotive control systems. Such systems usually consist of physically separated computing entities, sensors, and actuators, which are interconnected via a real-time communication infrastructure for exchanging data.

It turns out that many of these solutions are based on legacy systems and require a vast amount of mental effort for their comprehension. These systems generally are labeled as ’complex’. Especially in safety critical systems, i.e., systems where missing a deadline may cause severe damage to human, animal, machine, or environment, reducing complexity as far as appropriate is essential. One approach in order to achieve this reduction is the introduction of an architecture that supports composability in the value domain as well as in the temporal domain.

The main contribution of this thesis is a CORBA-based architecture for a distributed hard real-time system, which provides end-to-end predictability, while retaining temporal composability, by defining a generic interface based on an Interface File System and a communication layer that is accessed in a time-triggered manner. The communication model that has been chosen for this architecture supports networks in bus topology as well as networks in star topology as special cases. Thus, every algorithm for this architecture can be used for both of these topologies.

CORBA is an open standard, which provides developers of distributed systems with a flexible middleware, capable of integrating complex applications in heterogeneous environments. It allows interoperability between components on different platforms and written in different programming languages. Since CORBA has been originally designed for large business applications, it is not perfectly suited for hard real-time applications running on embedded systems with very limited resources. The existing Real-Time-CORBA specification results in a bigger footprint than traditional CORBA and does not support temporal composability, which is a key principle for reducing mental complexity in a distributed hard real-time system.

As a further contribution, an algorithm for the fault-tolerant measurement of the propagation delay is presented, which allows to compensate it.

  author =      "Thomas Losert",
  title =       "Extending {CORBA} for Hard-Real Time Systems",
  address =     "Treitlstr. 3/3/182-1, 1040 Vienna, Austria",
  school =      "Technische Universit{\"a}t Wien, Institut f{\"u}r Technische Informatik",
  month =       may,
  year =        2005
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