Fault-Adaptivity in Hard Real-Time Component-Based Software Systems

Complexity in embedded software systems has reached the point where we need run-time mechanisms that provide fault management services. Testing and verification may not cover all possible scenarios that a system encounters, hence a simpler, yet formally specified run-time monitoring, diagnosis, and fault mitigation architecture is needed to increase the software system’s dependability. The approach described in this paper borrows concepts and principles from the field of ‘Systems Health Management’ for complex aerospace systems and implements a novel two level health management architecture that can be applied in the context of a model-based software development process.

At the first level, the Component-level Health Manager (CLHM) provides localized and limited service for managing the health of individual software components. A higher-level System-level Health Manager (SLHM) manages the health of the overall system. SLHM includes a diagnosis engine that uses a Timed Failure Propagation (TFPG) model automatically synthesized from the system specification built in the model-based design environment that accompanies the runtime system. SLHM also includes a reactive timed state machine used for mitigation, whose code is also generated from the model-based specification. This paper uses simple examples to illustrate the use of the approach.