A formal approach to collaborative modelling and co-simulation for embedded systems

Abstract

The effective use of model-based formal methods in the development of complex embedded systems requires the integration of discrete-event models of controllers with continuous-time models of their environments. This paper proposes a new approach to the development of such combined models (co-models), in which an initial discrete-event model may include approximations of continuous-time behaviour that can subsequently be replaced by couplings to continuous-time models. An operational semantics of co-simulation allows the discrete and continuous models to run on their respective simulators and managed by a coordinating co-simulation engine. This permits the exploration of the composite co-model's behaviour in a range of operational scenarios. The approach has been realised using the Vienna Development Method (VDM) as the discrete-event formalism, and 20-sim as the continuous-time framework, and has been applied successfully to a case study based on the distributed controller for a personal transporter device.

Towards Semantically Integrated Models and Tools for Cyber-Physical Systems Design

“…These were embodied in the Crescendo tool 6 based on a master-slave architecture with the Overture and 20-sim simulators acting as slaves. Co-simulation was defined by a reconciled operational semantics [8]. The technology and industry experience are described in [9].…”

“…Second, it stands alone in a development process and assumes the engineer both understands what they wish to model before starting, and has external means to analyse the results of simulation. These concerns formed the basis for developing an integrated tool chain in the ongoing INTO-CPS project 8 .…”

A rigorous approach to the design of resilient cyber-physical systems through co-simulation

“…Methods have been described for co-model construction [9] and these have been piloted in industry case studies in several sectors [10]. Modelling patterns have been developed for classes of faults and fault tolerance mechanisms on the basis of industry need.…”

“…Applications of the methodology to this case study include initial VDM modelling of the whole system as a "way in" to more detailed co-modelling; a DE-first approach to construction of the co-model [9], following general controller patterns described in the guidelines; and modelling of faults and fault tolerance mechanisms following patterns from the guidelines. Exploration of the human element of the system (including user input and reaction to stimuli) is possible using combinations of the two modelling languages combined with the scripting features of the DESTECS tool.…”

Getting Software Engineering out of Isolation

“…While control engineering typically uses tools operating on Continuous-Time (CT) models, software engineering is founded on Discrete-Event (DE) models. In order to evaluate alternative designs and support early defect analysis or correction, it is essential that engineers collaborate across disciplines in short windows of opportunity [14], [15]. Modelbased approaches provide a way of encouraging collaboration, but engineers need to jointly perform design evaluation and analysis using models expressed in different tools.…”