An Effective Semi-analytical Model for the Inner Forced Vibration of the Power System in UUVs

Since the power and propulsion system is of great essence for the Underwater Unmanned Vehicles (UUVs), the analysis of its free or forced vibration characteristics is becoming increasingly important in view of the fact that it is also the main cause of vibration and noise. A typical power system consists of power equipment (e. g. an electric motor) and a thin cylindrical or conical shell, the free vibrational characteristics of which are analyzed separately in most researches or using rigid body assumption to model the system. The finite element method (FEM) may compensate for the disadvantages of high order modal analysis in rigid body assumption, but is usually of poor computation efficiency even for the high-performance computers. An effective semi-analytical model is introduced in this paper to improve the research techniques in the forced vibration and noise analysis of power system. The transfer matrix method (TMM) is adopted to build a discrete model, which is composed of discrete disks and rotor segments with distributed mass and elasticity, for the forced vibration of power equipment. Unlike FEM, the order of transfer matrix in TMM stays with the number of initial state variables and does not increase with the degree of freedom of the system. A spring-damper element is created to model the power equipment's mounting system on the shell, which completes the excitation transfer path from the power equipment to the shell. A power series solution is used to solve the Donnell-Mushtari equation of motion of the conical shell wherein the forced vibration is considered. Simulation results present the proposed semi-analytical model combines the computation precision with efficiency.