![]() These projects are existence proofs that deterministic CPS models are possible and practical.Rajat Acharya, in Satellite Signal Propagation, Impairments and Mitigation, 2017 8.2.3.3 Rake receiver The second project is Ptides (programming temporally-integrated distributed embedded systems), which shows that deterministic models for distributed cyber-physical systems have practical faithful realizations. The first project is PRET, which shows that the timing precision of synchronous digital logic can be practically made available at the software level of abstraction. Two projects show that deterministic CPS models with faithful physical realizations are possible and practical. ![]() Cyber-physical systems, however, combine these models in such a way that determinism is not preserved. Key deterministic models that have proven successful include differential equations, synchronous digital logic and single-threaded imperative programs. ![]() Deterministic models have historically proven extremely useful and arguably form the kingpin of the industrial revolution and the digital and information technology revolutions. This paper is about better engineering of cyber-physical systems (CPSs) through better models. I demonstrate the power of the idea with examples including model optimization and automatic model construction. The research has a wide range of practical applications. By using a shared variable to represent the model under transformation, the overhead caused by communication with transient data packages is eliminated. The event queue and the notion of model time enable the scheduling of future tasks. It allows transformation tasks to be composed hierarchically. I show that Ptera is an appropriate control language for transformation workflows. Realizing their limitations in expressiveness and efficiency, I create the Ptera (Ptolemy event relationship actor) model of computation based on event graphs. Existing control languages include finite state machines and dataflow diagrams. To improve flexibility over traditional approaches, I introduce extensions to allow complex transformation rules with variable structures to be specified with compact higher-order descriptions.Ī transformation workflow consists of basic transformations controlled in a control language. The semantics of transformation rules is defined based on graph transformation theory. This makes it convenient for the designers to use the technology. I invent a syntax for transformation rules, which is close to the modeling language that designers use to create the input models. I define a basic transformation with a transformation rule, which describes the relationship between input models and the result of the transformation. In this dissertation I present my work on a flexible and efficient model transformation technique, which includes a transformation engine and a formal and expressive control language. Here we report on the outcomes dur-ing the first two years of the project. The objective is a framework for designing deployable timed distributed systems. This project seeks to elevate timing and distribution to the level of the programmers model, so that applications are built by di-rectly expressing timing and distribution properties. These technologies, however, are used with relatively conventional concurrency models (threads and processes). Existing methods such as real-time operating systems, time-triggered networks, and network time synchronization deal with parts of the problem. Given time synchronization with some known precision, we believe that distributed applications should be designed and developed differently, and that time synchronization can help with robust coordination of un-reliable components. The introduction of network time synchronization such as IEEE 1588 makes possible time coherence that has not traditionally been part of the com-putational models. ![]() Applications include industrial au-tomation, instrumentation systems, and networked embed-ded software systems. Such systems coordinate components on a network, and timeliness matters. ![]() This project seeks models of computation, software tech-niques, and analytical models for distributed timed sys-tems. ![]()
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