his article deals with the identification of nonlinear models T in observer canonical form of hydraulic servo-drives from sampled data of input-output measurements. The data are processed by a modified Recursive Instrumental Variables algorithm, to provide input-output relationships of the plant dynamics. From the parameters of the input-output relations, continuous state-space nonlinear models can be derived. Tests were performed on a strongly nonlinear hydraulic drive which has been used for

more »

... esearch in our laboratory for several years. Results demonstrate good correspondence between the data and the identified models.