Abstract
Development of vehicle electronic systems, due to continuous improvement of vehicle performance, requires meeting ambitious goals from the performance, reliability, safety, and functionality points of view. This problem is exacerbated when we consider integration of several subsystems (VDC, ARC) that collaborate to a single vehicle function. The behaviour of each subsystem involves interaction with all the integrated ones, and such interactions are extremely complex to describe and control, especially in the presence of potential faults when dealing with safety requirements or alternative control strategies. An increasingly important role is therefore a suitable specification methodology, which allows system designers to model, understand, evaluate and simulate system behaviour before committing to a particular solution or starting the implementation phase.
This paper presents the research activities that FIAT Auto, in cooperation with Politecnico di Torino, is currently developing for establishing such a specification methodology, by exploiting the Unified Model Language (UML). The aim of this approach, from the point of view of a car system designer, is a comprehensive specification methodology that allows vehicle concept validation and tight control over supplier-provided part specifications.
UML is a standard object-oriented specification methodology, widely deployed by the software engineering community, that allows using a graphical notation to describe the system, its hierarchical decomposition, the interactions between sub-systems, and in some cases it allows high-level simulations.
The application of an UML-based methodology to automotive system requires adapting it to the characteristics of embedded, real-time, dependable, low-cost automotive systems. Some researchers already proposed some partial solutions to this problem, such as the CARTRONIC systems developed by Bosch, the AIT-WOODDES lead by Peugeot-Citroen, or the Automotive-UML initiative by Daimler Chrysler research.
In integrated systems, the responsibilities of the car manufacturer include design of the system level, thus the focus of this research activity is in capturing a multidisciplinary view of the vehicle system, by combining performance requirements coming from mechanical design, safety requirements analysed via aero spatial methods, and electrical and power issues. All of these requirements will be captured in the UML model of the integrated vehicle system, and will allow the analysis of interaction between subsystems and qualitative and quantitative evaluation of design constraints to be passed to part suppliers.
The methodology currently under developemnt is being applied to a first case study, that will be presented in the paper: a yaw rate/lateral acceleration sensor, and in particular its interactions with other vehichle active control systems, both in nominal cases and under faulty conditions.