Continuous-discrete adaptive observers for a class of nonlinear systems with sampled output

This paper considers the continuous-discrete time adaptive observer design for a class of nonlinear systems with unknown constant parameters and sampled output measurements. The proposed observer is in impulsive dynamics form with an inter-sample output predictor, where the observer state flows continuously when the output is not available, and a corrective term corresponding to measured samples is used to update the observer state. By assuming appropriate persistent excitation conditions and following a technical lemma, an upper bound of the sampling intervals is derived, with which, the convergence of the observer state and unknown parameters can be ensured. Finally, the proposed observer is used in an example of single-link flexible-joint robot manipulator to show the effectiveness.