Steady State Plant Availability under Sensor/Actuator Faults

G. Tortora, B. Kouvaritakis, and D. Clarke (UK)


fault tolerance, plant availability, intelligent instrumentation


Earlier work [1],[2] has dealt with the problem of accom modating failures in sensors and/or actuators by consider ing the dynamic effects of failures on the outputs. In many practical applications, however, it is paramount to ensure that the control system respects output constraints in the steady state. Should this not be possible then shutdown is inevitable, rendering considerations of the dynamic ef fects irrelevant. The property of being able to meet these steady state output constraints is defined in this paper as plant availability and necessary and sufficient conditions are developed for ensuring plant availability in the pres ence of constraints. The problem is cast in both open-loop and closed-loop formulations. The results of the paper are illustrated by means of numerical examples.

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