Abstract: Propeller thrust fluctuation is the major factor that induces vibration in a shaft-hull system. Based on the frequency domain model of the shaft-hull system, dynamic characteristics of this system are discussed and the mechanism of suppressing the system vibration by applying control force on the shaft is analyzed. An adaptive feedforward control strategy is proposed in terms of the mechanism. Numerical results demonstrate that control forces applied on the shaft are able to cancel the fluctuating thrust force to reduce the longitudinal vibration of the shaft and the hull. The influence of parameters on the coupled system is also discussed and the results show that location of the control forces have little effect on the control performance, different thrust stiffness results in different control force level, and the convergence rate of the control error changes with the thrust stiffness, but it will keep unchanged when the stiffness is large enough. An experimental model is established to verify numerical analyses. Stiffness of the thrust bearing changes the longitudinal vibration frequency of the shaft, and the proposed active control strategy is able to suppress the shaft and hull vibration effectively.

Key words: Active vibration suppression, Adaptive feedforward control, Coupled vibration, Longitudinal vibration control