[31,32] for discrete time systems and[33,34] for continuous systems. In Ref. [34] the authors proposed a framework for time-varying parameter estimation in the contin-uous time-domain for a large class of nonlinear systems using a sliding-neural observer. Neural network s have been proposed to estimate the wind speed directly, see the works of [8 e 11 ]. Some of the main drawbacks of these works have been stated before.