Model-based design methodologies are commonly used in industry for the development of complex cyber-physical systems (CPSs). There are many different languages, tools, and formalisms for model-based design, each with its strengths and weaknesses. Instead of accepting some weaknesses of a particular tool, an alternative Communicated by Prof. J. Sztipanovits, M. Broy, and H. Daembkes. This work is partially based on previous work published by the authors [7,8,15] is to embrace heterogeneity, and to develop tool integration platforms and protocols to leverage the strengths from different environments. A fairly recent attempt in this direction is the functional mock-up interface (FMI) standard that includes support for co-simulation. Although this standard has reached acceptance in industry, it provides only limited support for simulating systems that mix continuous and discrete behavior, which are typical of CPS. This paper identifies the representation of time as a key problem, because the FMI representation does not support well the discrete events that typically occur at the cyber-physical boundary. We analyze alternatives for representing time in hybrid co-simulation and conclude that a superdense model of time using integers only solves many of these problems. We show how an execution engine can pick an adequate time resolution, and how disparities between time representations internal to co-simulated components and the resulting effects of time quantization can be managed. We propose a concrete extension to the FMI standard for supporting hybrid co-simulation that includes integer time, automatic choice of time resolution, and the use of absent signals. We explain how these extensions can be implemented modularly within the frameworks of existing simulation environments.

This paper presents a master algorithm for co-simulation of hybrid systems using the Functional Mock-up Interface (FMI) standard. Our algorithm introduces step revision to achieve an accurate and precise handling of mixtures of continuous-time and discrete-event signals, particularly in the situation where components are unable to accurately extrapolate their input. Step revision provides an efficient means to respect the error bounds of numerical approximation algorithms that operate inside co-simulated FMUs. We first explain the most fundamental issues associated with hybrid co-simulation and analyze them in the framework of FMI. We demonstrate the necessity for step revision to address some of these issues and formally describe a master algorithm that supports it. Finally, we present experimental results obtained through our reference implementation that is part of our publicly available open-source toolchain called FIDE

Synchronous reactive models are used by automotive suppliers to develop functionality delivered as AUTOSAR components to system integrators (OEMs). Integrators must then generate a task implementation from runnables in AU-TOSAR components and deploy tasks onto CPU cores, while preserving timing and resource constraints. In this work, we propose an integrated synthesis flow that addresses both sides of the supply chain. On the supplier side, from synchronous models, we generate AUTOSAR runnables that promote reuse and ease the job of finding schedulable implementations. On the integrator side, we find the mapping of runnables onto tasks and allocation of tasks on cores that satisfy the timing constraints and are memory e cient.

Nanoscale circuits operating at sub-threshold voltages are affected by growing impact of random telegraph signal (RTS) and thermal noise. Given the low operational voltages and subsequently lower noise margins, these noise phenomena are capable of changing the value of some of the nodes in the circuit, compromising the reliability of the computation. We propose a method for improving noise-tolerance by selectively applying feed-forward reinforcement to circuits based on use of existing invariant relationships. As reinforcement mechanism, we used a modification of the standard CMOS gates based on the Schmitt trigger circuit. SPICE simulations show our solution offers better noise immunity than both standard CMOS and fully reinforced circuits, with limited area and power overhead.

Models are used in cyber-physical systems to improve the quality of the system and its development process by early validation and verification, using simulation, synthesis, and model-checking. Control algorithms are often specified and developed using Simulink models, with the limitation that the model is abstracted from the execution platform, with its computation and communication delays, and the generated code is meant to be executed in a single core. We propose a model-driven approach and tool support to specify the execution platform, the software and message implementation of synchronous models, and enable correct deployment and/or the evaluation of the impact of the delays of the selected platform on the system performance

This paper presents FIDE, an Integrated Development Environment (IDE) for building applications using Functional Mock-up Units (FMUs) that implement the standardized Functional Mock-up Interface (FMI). FIDE is based on the actororiented Ptolemy II framework and leverages its graphical user interface, simulation engine, and code generation feature to let a user arrange a collection of FMUs and compile them into a portable and embeddable executable that efficiently co-simulates the ensemble. The FMUs are orchestrated by a well-vetted implementation of a master algorithm (MA) that deterministically combines discrete and continuous-time dynamics. The ability to handle these interactions correctly hinges on the implementation of extensions to the FMI 2.0 standard. We explain the extensions, outline the architecture of FIDE, and show its use on a particularly challenging example that cannot be handled without the proposed extensions to FMI 2.0 for co-simulation.

No abstract

No abstract