Reduced-order Modeling Method for Longitudinal Vibration Control of Propulsion Shafting

The propulsion shafting is one typically continuous, elastic and stepped body. To design an active controller for propulsion shafting by applying the modern control theory, an accurate reduced-order model with lumped parameters is required. This research concentrated on the reduced-order modelling method for longitudinal vibration control of a direct transfer marine propulsion shafting. The longitudinal vibration modes of the propulsion shafting were determined with one-dimension elastic wave approach based on its continuous model in advance. Taking into account of the unobservability and uncontrollability of mode nodes, the nodes of the neglected low highest mode were selected as locations of the reduced-order model mass points. By modifying mode shapes of the reduced-order model with sensitivity analysis, the reduced-order model can accurately represent the first low order modes of the continuous propeller-shafting system, enabling the effectiveness of controller design in the physical state space.