Kim, Jesung
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Publication Distributed-Code Generation from Hybrid Systems Models for Time-delayed Multirate Systems(2005-09-19) Anand, Madhukar; Fischmeister, Sebastian; Kim, Jesung; Lee, InsupHybrid systems are an appropriate formalism to model embedded systems as they capture the theme of continuous dynamics with discrete control. A simple extension, a network of communicating hybrid automata, allows for modeling distributed embedded systems. Although it is possible to generate code from such models, it is difficult to provide formal guarantees in the code with respect to the model. One of the reasons for this is that, the model is set in continuous time and concurrent execution with instantaneous communication, whereas the generated code is set in discrete time with delayed communication. This can introduce semantic differences between the model and the code such as missed transitions, faulty transitions, and altered continuous behavior. The goal of faithful code generation is to minimize these differences. In this paper, we propose a relaxed criteria of relative faithful implementation. Based on this criteria, we propose dynamically adjusting the guard at runtime using estimates of errors for preventing faulty transitions. We also identify a sufficient condition to ensure no missed transitions in the code.Publication Generating Sound and Resource-Aware Code from Hybrid System Models(2006-03-15) Anand, Madhukar; Kim, Jesung; Fischmeister, Sebastian; Lee, InsupModern real-time embedded systems are complex, distributed, feature-rich applications. Model-based development of real-time embedded systems promises to simplify and accelerate the implementation process. Although there are appropriate models to design such systems and some tools that support automatic code generation from such models, several issues related to ensuring correctness of the implementation with respect to the model remain to be addressed. In this work, we investigate how we can derive sampling rates for distributed real-time systems generated from a hybrid systems model such that there are no switching discrepancies and the resources spent in achieving this are a minimum. Of particular interest are the resulting mode switching semantics and we propose an approach to handle faulty transitions and compute execution rates for minimizing missed transitions. As a guiding example for our approach, we describe a hybrid systems model for vehicle coordination in which one vehicle acts as a leader and a second follows the leader guaranteeing to maintain a safe distance between the two vehicles.Publication Code Generation from Hybrid Systems Models for Distributed Embedded Systems(2005-05-18) Anand, Madhukar; Kim, Jesung; Lee, InsupCode generation from hybrid system models is a promising approach to producing reliable embedded systems. This approach presents new challenges as the precise semantics of the model are hard to capture in the code. A framework for generating code was introduced for single threaded/processor environments. Here, we extend it by considering code generation for distributed environments. We also define criteria for faithful implementation of the model. To this end, we define faulty and missed transitions. For preventing faulty transitions, we build on the idea of instrumentation we have developed for sound simulation of hybrid systems. Finally, we present sufficient conditions to avoid missed transitions and provide examples.