Observability and Dynamic Observers

Abstract

Observability is a property of a dynamic system together with its observable inputs and outputs, according to which the latter alone suffice to determine exactly the state of the system. A data processor which performs state determination is called an “observer.” In an intuitive sense observability is a property dual to controllability: a system is controllable if any state can be reached by suitable choice of input; it is observable if (when the input is known) its state can be computed by suitable processing of the output. For linear time-invariant systems this intuitive duality translates into a precise algebraic duality.