Railway wheel fault diagnosis using a fuzzy-logic method

A simple method for diagnosis of railway wheel defects using fuzzy-logic is proposed. The method is based on vibration measurements at different train speeds on healthy wheels and wheels with defects known a priori. The measured vibrations are statistically analyzed and confidence intervals for healthy and defective wheels depending on train speed and frequency of analysis are established. To facilitate the implementation of the method a fuzzy-logic is adopted. The fuzzy-logic model stores the obtained experience in a database and performs the decision making on damage extent and consequently the need of preventive maintenance. In view of the obtained results, the advantages and the limitations of the proposed approach as well as suggestions for further improvements are presented and discussed.     

PIV measurement of the flow past a generic car body with wheels at LES applicable Reynolds number

Experiments by using 2D–2C Particle Image Velocimetry (PIV) were carried out and reported concerning the flow field past a generic car body (modified Ahmed body) which is equipped with wheels and wheel-arches. The Reynolds number was chosen to not exceed 2E+5 based on the height of the Ahmed body which makes it possible to investigate the same configuration by means of Large Eddy Simulation (LES). The wheels were rotating but the ground was stationary. The wheel-ground contact was realized by means of small rectangular openings below the wheels in the ground plane in which the wheels were immersed. The transition contour of the immersed wheels and the ground, as well as the rectangular openings below the wheels were properly sealed to prevent parasite flow and to provide well defined boundary conditions for an upcoming LES investigation.The flow field was measured in several planes with normal vectors pointing towards the directions normal to the free stream. Statistical characteristics of the flow are provided and discussed.     

Parametric analysis of lugged wheel performance for a lunar microrover by means of DEM

The purpose of this study was to develop a numerical tool to simulate the performance of lugged wheels designed for a lunar microrover. The performance was analyzed using a Discrete Element Method (DEM) whose accuracy was validated for interactions between lugged wheels and soil. DEM analysis indicated that, on flat horizontal lunar surfaces, wheels with 18 10-mm-high lugs would provide less net traction than would wheels with 36 5-mm-high lugs.     

Visualization and analysis of wheel camber angle effect for slope traversability using an in-wheel camera

This paper visualizes and analyzes an effect of a wheel camber angle for the slope traversability in sandy terrain. An in-wheel camera developed in this work captures the wheel-soil contact phenomenon generated beneath the wheel through a transparent section of the wheel surface. The images taken by the camera are then analyzed using the particle image velocimetry. The soil flows with various wheel camber angles are analyzed with regard to the soil failure observed on the slope surface. The analysis reveals that the slope failure and soil accumulation in front of the wheel significantly affect the wheel forces and distributions of the wheel sinkage in the wheel width direction. Further, the side force of the wheel in traversing a slope decreases as the slip ratio increases because the shear stress in the slope downward direction decreases owing to the slope failure.     

Distance unimodular equivalence of graphs

Let G be a connected graph and D(G) be its distance matrix. In this article, the Smith normal forms of the integer matrices D(G) are determined for trees, wheels, cycles, complements of cycles and are reduced for complete multipartite graphs.     

Development of in-wheel sensor system for accurate measurement of wheel terrain interaction characteristics

Planetary rovers need high mobility on a rough terrain such as sandy soil, because such a terrain often impedes the rover mobility and causes significant wheel slip. Therefore, the accurate estimation of wheel soil interaction characteristics is an important issue. Recent studies related to wheel soil interaction mechanics have revealed that the classical wheel model has not adequately addressed the actual interaction characteristics observed through experiments. This article proposes an in-wheel sensor system equipped with two sensory devices on the wheel surface: force sensors that directly measure the force distribution between the wheel and soil and light sensors that accurately detect the wheel soil surface boundary line. This sensor design enables the accurate measurement of wheel terrain interaction characteristics such as wheel force distribution, wheel–soil contact angles, and wheel sinkage when the powered wheel runs on loose sand. In this article, the development of the in-wheel sensor system is introduced along with its system diagram and sensor modules. The usefulness of the in-wheel sensor system is then experimentally evaluated via a single wheel test bench. The experimental results confirm that explicit differences can be observed between the classical wheel model and practical data measured by the in-wheel sensor system.     

Wm∨Pn的交叉数

在Klesc M给出的联图W_3 V P_n的交叉数的基础上,继续对联图Wm V Pn（m=4,5）的交叉数cr进行了研究,得到了cr（W3 V Pn）=Z（5,n）＋n＋「n/2＋1」以及cr（W5 V Pn）=Z（6,n）＋n＋3[n/2」＋1,n≥2.     

一类混合Ramsey数

设a(G)表示图G的点荫度,m为正整数,H为连通图,混合Ramsey数v(a;m;H)被定义的为最小的正整数P,使得对任意P阶图G则有a(G)≥m或者H包括于G^-。本文给出了v(a;m;H)的一种计算方法,并对图Cn和轮Wn确定了v(a;n;Cn)和v(a;m;Wn)的值。