Discrete Dynamics in Nature and Society
Volume 5 (2000), Issue 2, Pages 89-96

Unveiling uncertain forces in second-order driven oscillators via internal model: A discrete-time feedback

R. Femat and C. Jiménez-gallegos

Universidad Autónoma de San Luis Potosí Apdo Postal 3-90, S.L.P., San Luis Potosí 78231, Mexico

Received 17 February 2000

Copyright © 2000 R. Femat and C. Jiménez-gallegos. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Unveil uncertain forces acting into (or onto) systems is a very interesting and old problem. Indeed, a lot effort has been devoted to develop procedures which results in the understanding of the uncertain forces and its effects. This contribution deals with recovering of the dynamics of the uncertain forces from measurements (time series). The main idea is to construct an internal model of the nonlinear system and design a discretetime feedback in such way that the model/system differences be stabilized at origin. In principle, if the internal model tracks the trajectory of the nonlinear system, then the uncertain force is recovered by the stabilizing command.