This paper deals with the exact feedback linearization of nonlinear plants
using estimated states. Under appropriate hypotheses, exact linearization c
an be achieved through transformation of states and feedback. We assume tha
t the states cannot be measured so that a nonlinear observer, with exponent
ial convergence, is included in the loop. We establish sufficient condition
s to guarantee that the overall system trajectories asymptotically converge
to those obtained with feedback linearization utilizing the true states. W
e apply our results to control an electrical drive using a permanent-magnet
synchronous motor without mechanical and optical sensors. The behaviour of
our control scheme is illustrated by simulations.