Abstract
Many of the theoretical development in the area of control system design based on the system states assume that the system state vector is available for use by the control scheme. In order to exploit these control strategies, a suitable estimate of the state vector must be constructed for use in the original control law. This paper proposes a modified Utkin observer for estimating modal coordinates of structural vibration for the purpose of the vibration control. The original Utkin observer is constructed by the concept based on the sliding mode control theory and has robustness against certain class of uncertainty by virtue of the discontinuous input. The Utkin observer with the robustness would be improved to have much more stability by adding a negative output error feedback term to the observer. This consideration results in the modified Utkin observer.
