Autonomous onboard computer systems using real time trace models

Abstract

In the paper some particularities of the autonomous spacecraft computer systems are discussed. The ways to reach the autonomy are described - high reliability and adaptability of the system, reached by application of AI elements formal structural models (specification, verification and real time control) and dynamic reconfiguration. A method using trace models In real time for testing of system operations is described. The method is suitable for systems specified by process algebras (CSP - Communicating Sequential Processes, Timed CSP, ASM - Abstract State Machine, and TAM - Temporal Agent Model) where process tracts are used. The computing processes and these in the hardware are observed. Special control processes (tracers) are specified. They allow to control in real time the correspondence of the real system traces and preliminary computed traces (the formal specification) and send messages to the other subsystems when no correspondence (e.g. to specification and dynamic reconfiguration subsystems). The method allows finding in real, time the software and hardware incorrectly functioning (disparity of the traces) based on rigorous mathematical specification. In the paper are described: an autonomous control system structural model, an algorithm for real time traces control, software simulations (laboratory models) of autonomous systems, the faults and reaction of the tracer-processes, all based on CPPCSP - C++ Communicating Sequential Processes library. The application of trace models in real time allows find any system incorrectly operating and this is one of the ways for,increasing the onboard computer systeme reliability and to achieve full operation autonomy.