Excitation Force Identification of Multiple Devices in Railway Vehicles Based on Modal Superposition Method and Kalman Filter

The excitation force identification of multiple devices in railway vehicles is studied. The vertical dynamic coupling model between the flexible car body of high-speed train and the under-chassis active device with excitation itself is established based on the modal superposition method. The excitation force from device is identified based on Kalman filter. A modal order selection method is developed for improving the identification accuracy based on tolerance index. The identification effects of single and multiple active devices including single-frequency steady-state, multi-frequency steady-state, impact, sawtooth wave and square wave excitation forces are analyzed. An error limit range of 5% is defined to evaluate the identification results. The results show that the method is suitable for the identification of various steady-state and transient-state excitation forces, and the identification results of excitation forces of single and multiple active devices have good accuracy.

Multi-Degrees of Freedom System and Hydrodynamic Principle

A system with one degree of freedom is far from reality, because we do not take into account all the degrees of freedom. In order to be close to the reality, it is necessary to use a system with several degrees of freedom. Efforts in this chapter are concentrated to the study of multi-degrees of freedom system, whether for a free undamped and forced damped system, by detailing the modal superposition method as well as a coupled coordinates. We finish the chapter with hydrodynamic study using Hozner method as well as some applications.

Vibration characteristics analysis of composite floating rafts for marine structure based on modal superposition theory

Composite materials have become a research hotspot in the field of vibration and noise reduction for their high strength, high damping, and other outstanding mechanical properties in recent years. In this paper, the effect of laminated materials on the dynamic performance of floating rafts is investigated based on modal superposition theory using the finite element method. The detailed derivation of the modal superposition theory was made, and taking T700 fiber-reinforced composite material as an example the damping effect of the floating raft structure in three cases was discussed: whether the composite material is laid or not, different layup angles, and different layup positions. The research shows that laying composite materials can improve damping effect of the floating raft and the changes in both the laying angle and the laying position will affect its dynamic performance. Moreover, the damping performance of the structure is inversely correlated with its stiffness within a certain range.