A modal disturbance estimator for vibration suppression in nonlinear flexible structures

This paper presents a control strategy for the suppression of vibration due to unknown disturbance forces in large, nonlinear flexible structures. The control action proposed, based on the modal approach, consists of two contributions. The first is the well-known Independent Modal-Space Control, which increases system damping and improves its behavior close to the resonance frequencies. The second is a disturbance estimator, which calculates the modal components of the external forces acting on the system and compensates for them using actuator forces. The system modal coordinates, required by both logics, are estimated through a modal state observer.The proposed control logic is tested on a flexible boom. The paper reports the numerical and experimental results both for the linear and nonlinear (large motion) boom configuration.

► Independent Modal-Space Control allows to suppress vibrations in resonance. ► Disturbance estimator suppresses vibrations due to any external force. ► A combination of these two control logics is proposed. ► The control logic is validated both numerically and experimentally. ► The method is robust with respect to the system uncertainties and nonlinearity.