This paper presents the conceptual model and the fundamental mechanisms for software development in the context of the Brite-EuRam "Safety Related Fault Tolerant Systems in Vehicles" (nicknamed X-By-Wire) project. The objective of the X-By-Wire project is to achieve a framework for the introduction of safety related fault-tolerant electronic systems without mechanical backup in vehicles. To achieve the required fault tolerance level, an X-By-Wire system must be designed as a distributed system comprising a number of fault-tolerant units connected by a reliable real-time communication system. The time-triggered TTP/C real-time communication protocol was selected for the communication system. At the logical design level, the so-called XBW model was developed to combine the basic mechanisms for system design (BASEMENT and DFR). For the detailed software design of embedded distributed fault-tolerant hard real-time systems, the framework of the DFR meta object model is used. The model supports systematic error detection strategies for achieving fail silence behaviour at the node level and fault tolerance strategies for achieving fail-operational behaviour at the system level. Within the X-By-Wire project, a prototype of a steer-by-wire system is developed. This prototype demonstrates the application of the principles, model, and mechanisms developed by the X-By-Wire partners.
Abstract