Farah Bouakrif  , Djamel Boukhetala  , Fares Boudjema  , 
    Disturbance Observer Based Tracking Control for Robot Manipulators with Model Uncertainty,
    Journal of Engineering and Applied Sciences,
    Volume 2,Issue 6,
    2007,
    Pages 1066-1073,
    ISSN 1816-949x,
    jeasci.2007.1066.1073,
    (https://makhillpublications.co/view-article.php?doi=jeasci.2007.1066.1073)
    Abstract: This study presents a disturbance observer based tracking control for robotic manipulators. The tracking control problem is formulated as a disturbance rejection problem, with the mechanical nonlinearities, unmodeled dynamics and external disturbances lumped into the disturbance term. The global stability of the composite controller and observer is guaranteed, this result is based on Lyapunov theory. In simulation, the tracking control of a two link manipulator is used as an example to verify the proposed algorithm, when the Coulomb and Viscous friction is considered as an external disturbance.
    Keywords: Tracking control;disturbance observer;nonlinearities;robot manipulator