Vibration reduction of a pitch-roll ship model with longitudinal and transverse absorbers under multi excitations

This paper presents an application of passive vibration control to a non-linear spring pendulum system simulating a ship’s roll motion. This leads to a four-degree-of-freedom (4-DOF) system subjected to multi external and parametric excitations. Two absorbers in the longitudinal and transverse directions are designed to control the vibration near the simultaneous primary, sub-harmonic and internal resonance where system damage is probable. The theoretical results are obtained to second order approximations applying the multiple scale perturbation technique (MSPT). The stability of the steady-state solution near the simultaneous resonance case is investigated and studied applying frequency response equations. The effects of the absorbers and some system parameters on the vibrating system are studied numerically. The simulation results are achieved using MATLAB 7.0 programs Shampine et al. (2003) [16]. Comparison with the available published work is reported.