Terumichi Yoshiaki

In recent years, some systems which contain a floating body, such as Unmanned Aerial Vehicle (UAV) connected with a tether, are used for transportation. However, the coupling motion of the system is not easily predicted with high accuracy and may induce instability of the floating body. Therefore, to control the system, comprehension of the motion of the whole system is of great importance to control the system. In this investigation, modeling and formulation of the tethered system which contains a floating body is presented using Absolute Nodal Coordinate Formulation (ANCF) and the result of the numerical simulation of the motion is discussed.

This paper proposes a method to simulate the primary bending vibration in a test stand consisting of one-third segment car body and a full-scale bogie of magnetically levitated (maglev) vehicles. The purpose of this system is to evaluate an effect of flexural vibration to the ride comfort on maglev vehicles. The system utilizes hardware-in-the-loop simulation (HILS). The HILS system calculates internal forces acting from remaining two-thirds segment car body which is missing in reality, and applies constraint forces equivalent to the internal forces to the one-third segment using electric actuators.

Behavior analysis of a coupled train under crash condition has several difficulties, because a coupled train has structural, mechanical and kinetic aspects. Many kinds of behavior can be observed when longitudinal heavy force is applied to a train set. Such as; vertical train buckling, car body deformation, coupler collapse and overriding. The objective of this study is to clarify the processes and the mechanisms of a train set behavior under these conditions, including impact force. In this study, in order to analyze the train set motion, we developed a numerical simulation model which can simulate dynamic behaviors including structural deformation, mechanical behavior and kinetic motion on a straight track. The numerical simulation model consists of both the structural models which are formulated by FEM (finite element method) and the kinematic models which are based on the MBD (multi body dynamics) theory. In this model, the FEM model was validated by comparison with the results of the collision test using the full scale test car. Simulations with large kinetic displacement and structural deformation under two types of load conditions were conducted by means of this model. One being a low speed heavy load condition, such as a relief operation, and the other a high speed light load condition, such as a collision with a relatively light weight foreign obstacle at very high speed. Large deformation processes and mechanisms data of a train set under wide load conditions ranging from low speed against a heavy obstacle to high speed against a light obstacle obtained from the simulations and experiment are comprehensively clarified.

A restraint on the wear of train wheels and rails of a railway is required to improve running safety and reduce maintenance cost. Wear is one of the problems that need to be settled in managing railway property. In order to deal with this problem, it is fundamental that we understand the mechanism of wear between rail and wheel. For this purpose, in this study an experimental approach to wear development using test stand that has controlled environment with respect to contact parameters and factors influential in causing wear is taken. In the experiments conducted, a 1/5 scaled rolling stock test stand consisting of a wheel set and two rail rollers is used. A comparison was made of the worn wheel surfaces and the creep force under various contact interface conditions such as coefficient of friction and radius of curvature. The contact interface conditions included a dry surface condition and a friction modifier-applied condition, in which low coefficient friction and high positive friction were used as friction modifiers. By studying photographs of worn wheel surfaces and the creep forces under various conditions, the mechanism of wear development at the rail/wheel contact point is examined. In particular, we clarify the influence of the creep force on the wear coefficient and the status of the worn wheel surfaces.

One method to evaluate the running stability of railway vehicles is a running test on roller rigs. In this study, we carried out running tests in order to investigate the differences in the dynamic behavior of half-body and full-body vehicle models on roller rigs in frequency response tests with vertical and rolling forced excitations. By means of a vehicle dynamics analysis by computer simulation, we evaluated the influence of the center of gravity of the body on the dynamic behavior of the vehicle. As a result, it was verified that, for both vertical and rolling forced excitations, when the gravity position of body is equal to the center of body, the dynamic behavior of the full-body vehicle model is nearly the same as that of the half vehicle model in the each excited direction. Otherwise, the dynamic behavior of the full-body vehicle model is different to that of the half vehicle model, because of a pitching movement of the body in the case of vertical forced excitations and a rolling and yawing movement of the load frame in the case of rolling forced excitations.