Stabilisation of nonlinear systems by qualitative feedback controllers

The paper concerns the problem of stabilising a nonlinear system by means of a controller that has access merely to qualitative state measurements [x(k)] and qualitative control inputs [u(k)]. Necessary and sufficient conditions for the existence of a stabilising qualitative controller are given. The results refer merely to the qualitative model of the plant, which is represented by a nondeterministic automaton. The important consequence of these results is that only a qualitative model of the plant is required for finding qualitative feedback controllers