# Dynamic Characteristics Analysis of a Rigid Body System with Spatial Multi-Point Supports
###### Abstract
In the research on vibration isolation of diesel engine systems of high/medium power levels, some work on the analysis of the arrangement of vibration isolators and the influence of variation of stiffness and damp has been carried out. [PERSON] et al. [11] established a general dynamics model to describe the system dynamics of high-power engines with different numbers of mounts. [PERSON] et al. [12] established a six-degrees-of-freedom rigid body dynamics model for marine diesel generator sets and conducted an evaluation study on the vibration transmitted from the support to the engine body. With improvement of vibration and noise reduction requirements, complex two-stage vibration isolation systems, and large float raft vibration isolation systems that can carry dozens of power equipment have gradually been developed and applied [13; 14; 15]. [PERSON] et al. [16] studied the transfer function curve of the two-stage vibration isolation system with different stiffness ratios, and the vibration transfer energy can be reduced when the stiffness ratio of the upper and lower isolators increased as much as possible. [PERSON] et al. [17] endured a multi-parameter optimization method for the natural frequency of the float raft vibration isolation system, where the natural frequency of the vibration isolation system could be limited to a narrow range by optimizing the stiffness of the raft body and the stiffness of the sub-raft connecting rod, to achieve the best vibration isolation effect. While people were studying the theory and engineering application of two-stage vibration isolation systems, the semi-active and active control of two-stage vibration isolation devices has also received extensive attention, and the main idea is to control the stiffness and to damp the vibration isolation system in real-time through some means to achieve a good vibration isolation effect [18; 19; 20]. [PERSON] et al. [21] employed global optimization technology to adjust adaptive hydraulic mount design parameters (mount flexibility, mount inertia parameters, etc.) for tuning an adaptive mount to different road and engine conditions, in order to achieve vibration isolation under low and high frequency excitations. In addition to the above research on the dynamic characteristics of the multi-support structure system of the power plant for automobiles, locomotives, ships, and in the aviation field, researchers have also studied the dynamic characteristics of the multi-support engine nacelle mounting system, mainly regarding the dynamic coupling characteristics of the engine and the suspension inside the nacelle [22; 23]. Few studies on the dynamics of aeroengine lubrication oil tank-mounting structure system have been documented, and studies on the influence of mounting structure (mount number, location, and stiffness, etc.) on aeroengine lubrication oil tank system have not been documented. [PERSON] [24] built the fluid-structure interaction model by MSC/Dytran while analysing the influence factor of oil tank sloshing and analysed the structure dynamics by Msc/Nastran. [PERSON] [25] proposed a three-dimensional, time accurate particle-cluster approach to predict highly dynamic airborne tank fuel sloshing and impact effects, as well as analyzed the dynamic behaviour of fuel inside a more complex geometry by simulating liquid sloshing in a toroidal tank. The results of this showed that fuel impact forces have a significant contribution to the pitch characteristics of external fuel tank. [PERSON] et al. [26] proposed a topology optimization method that considered the local stiffness of the mounting structure of the oil tank assembly, which improved the overall stiffness of the support, while considering the local stiffness. Through this method, the stiffness distribution of the bracket became more reasonable. In summary, there are few studies on the dynamics of rigid body systems with spatial multi-point elastic supports, and there is a gap in the dynamics research of the lubrication oil tank-mounting structure system.