Formal development of feedback control system with fault accommodation

Control systems are vulnerable to faults in control loops where faults may cause abrupt and damaging responses. These systems with fault accommodation are becoming more and more important while appearing in flight control, robots control and nuclear reactor control etc, and calling for more rigorous development approach. A formal approach is explored in this paper, basec on Extended Duration Calculus, for the development of such kind of systems. A typical example of control system with fault accommodation, two-level control system, is used for illustrating our approach. Its high level consists of an event-driven supervisor which reacts to the change of plant due to faults occurrence, and its low level consists of normal controller, reconfigured controller and other components with FDI (Fault Detection and Isolation) mechanism. Firstly performance and system specifications of the case are formulated in EDC; Then they are refined step wisely into specification of the supervisor and the low level components. Finally the whole system performance is verified EDC framework.