Application of the extended high gain observer to underactuated mechanical systems

For underactuated mechanical systems the use of disturbance estimators has been limited. For fully actuated mechanical systems, disturbance cancellation techniques have been studied and used to reduce the effect of disturbances on system performance. Particularly, the extended high gain observer has shown promising results in performance recovery. However, using the extended high gain observer to estimate and cancel the disturbance in one link of an underactuated system results in adding that disturbance to other links. This paper explores the effects of applying the extended high gain observer to an underactuated mechanical system. We show that the extended high gain observer can be used to reduce the effect of disturbances in a rotary pendulum system.