  This paper studies the reduced-order or full-order, dead-beat observer
problem for a class of nonlinear systems, linear in the unmeasured states. A
novel hybrid observer design strategy is proposed, with the help of the notion
of strong observability in finite time. The proposed methodology is applied to
a batch reactor, for which a hybrid dead-beat observer is obtained in the
absence of the precise measurements of the concentration variables. Moreover,
the observer is used for the estimation of the frequency of a sinusoidal
signal. The results show that accurate estimations can be provided even if the
signal is corrupted by high frequency noise.
