Sharif Digital Repository

Wheel wear has been a concern in the railway for several decades. Studying the form change of the wheel/rail contacts in particular railways consisting of sharp curves helps to identify the risk of severe or catastrophic wear to minimize maintenance costs in order to be competitive in the transportation business. In this paper, the wheel/rail contact was studied on the particular railways. The experimental measurement of wheel profiles was used as an input to Hertz Contact Theory (HCT). It was found that: 1) for these railways the wheel flange is highly worn; 2) a 5th order polynomial function is appropriate to model the wear behavior of the critical wheel; 3) the minimum and maximum contact... 

An advanced method using progressive concept of geometrical correspondence is applied to create a new wheel/rail contact model based on virtual penetration theory. The geometry and contact mechanism are solved simultaneously because of the independency in a defined correspondence. The model takes the penetrated profiles of wheel and rail and also associated creeps as inputs, and produces driving contact forces as output. The advantage of this model is that it doesn't require pretabulation of rigid contact situation. The method allows calculating flexible, non-elliptical, multiple contact patches during integration of the model. Consequently the rails with substructures can vibrate separately... 

A new optimal control law for direct yaw moment control, to improve the vehicle handling, is developed. Although, this can be considered as part of a multi-layer system, for the traction control of a motorized wheels electric vehicle, but the results of this study are quite general and can be applied to other types of vehicles. The dynamic model of the vehicle system is initially developed and, using the well-known optimal control theory, an optimal controller is designed. Two different versions of control laws are considered here and the performance of each version of the control law is compared with the other one. The numerical simulation of the vehicle handling with and without the use of... 

A new control law for direct yaw moment control of an electric vehicle is developed. Although this study is considered as part of a global control system for the traction control of a four motorized wheel electric vehicle, but the results of this study is quite general and can be applied to other types of vehicles. The dynamic model of the system has been analyzed and, in accordance with the optimal control theory, an optimal controller is designed. Two different versions of the control law have been considered and the performance of each version has been separately studied and compared with each other. Finally, the numerical simulation of the vehicle-handling model with and without the use... 

In this paper the analytical and simulation modelling of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out. Using the numerical method, the performance of adiabatic rotary dehumidifier and enthalpy wheels are parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. A comparison of solutions for different conditions used in the air dehumidifier has been investigated according to the previously published studies. These approaches have been developed for enthalpy wheels. The simulated results have been compared with the published actual values of an experimental work. This... 

Wheel wear is one of the major costs in railway tracks consisting of sharp curves. In this paper, wear behavior of S1002 profiles of wheels in the "Southern Line" of Iran's railway, which consists of a large number of distinct and/or consecutive sharp curves, is studied using the field data measuring technique. Based on wear behavior analysis of all wheels, an optimal wagon maintenance technique called the "first and second limits" is suggested to minimize the wagon's cost per traveled distance. The results show that: 1) A severe wheel flange wear occurs for all wheels in comparison to the wheel tread wear in normal tracks; 2) A wagon's detachment for repair of critical wheels on its four... 

Laser ablation is a novel non-mechanical wheel preparation method for optimizing the treatment costs of superabrasive tools. In this study the thermal effects of picosecond laser radiation on CBN superabrasive grinding wheel surface is analytically and experimentally investigated. The analytical approach is intended to find threshold process parameters for selective ablation of cutting grains and bond material. It has been analytically and experimentally shown that, the extent of material degradation is defined by the maximum surface temperature induced by the laser radiation which is in turn defined by the laser beam energy. It is also suggested that, the depth of laser thermal effects is... 

It is a great challenge for the universities to present undergraduate students the fundamental knowledge needed to develop intelligent unstable robots. Due to the inherent instability and nonholonomic constraints, the problem of two-wheeled inverted pendulum (TWIP) mobile robot is appealing and challenging case in control and dynamic systems. In this paper, an approach is presented to introduce undergraduate students of the control engineering, the principle of developing a. TWIP mobile robot. For this purpose, a. conceptual design algorithm for TWIP robots is contributed and based on the algorithm and the design criteria, a. prototype of the robot is constructed. In the construction... 

A study of the wheel and rail wear phenomenon can provide a chance for the optimal use of wheel profile, which results in cost efficiency, dynamic stability, travel comfort, and safety to prevent the derailment, especially in curves. In this paper, the experimental data are recorded based on the field measurements for worn wheels of a passenger wagon in the "Southern line" of Iran's railway system and are combined with the dynamic simulations to study the effects of severe wheel flange wear on the dynamics of wagon. The results show that the amount of wheel wear (especially the wheel flange) directly impacts the dynamic behavior of the wagon in curves. In addition, based on the history of... 

A study of the wheel and rail wear phenomenon can provide a chance for the optimal use of wheel profile, which results in cost efficiency, dynamic stability, travel comfort, and safety to prevent the derailment, especially in curves. In this paper, the experimental data are recorded based on the field measurements for worn wheels of a passenger wagon in the "Southern line" of Iran's railway system and are combined with the dynamic simulations to study the effects of severe wheel flange wear on the dynamics of wagon. The results show that the amount of wheel wear (especially the wheel flange) directly impacts the dynamic behavior of the wagon in curves. In addition, based on the history of... 

In this paper the analytical and simulation modelling of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out. Using the numerical method, the performance of an adiabatic rotary dehumidifier is parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. An approach to compare the solutions for different conditions used in air dehumidifier has been investigated according to the previous published studies. Comparing the simulated results with the published actual values of an experimental work substantiates the validity of model. The model accuracy with respect to the key... 

In this article a train model is developed for studying train derailment in passing through bends. The model is three dimensional, nonlinear, and considers 43 degrees of freedom for each wagon. All nonlinear characteristics of suspension elements as well as flexibilities of wagon body and bogie frame, and the effect of coupler forces are included in the model. The equations of motion for the train are solved numerically for different train conditions. A neural network was constructed as an element in solution loop for determination of wheel-rail contact geometry. Derailment factor was calculated for each case. The results are presented and show the major role of coupler forces on possible... 

The innovative powertrain configuration of modern electric vehicles with four-wheel independent drive (4WID) provides the possibility of simple and exact yaw moment control by controlling the electric motor of every wheel independently. In this study, a genuine control strategy for optimum direct yaw moment control is proposed. Although this can be considered as a global control system for traction control of 4WID electric vehicles, the analysis is quite general and can be applied to other types of vehicle. The directional vehicle model is derived and, in accordance with the optimal control theory, an optimum yaw moment controller is designed. Two versions of the control law are developed... 

This work presents the optimization of a solar collector surface in solar desiccant wheel cycle which for cooling process with typical configuration naming desiccant wheel, heat exchanger and water spray evaporative cooler. In this cooling cycle the thermal solar energy has used to heat the regeneration air of desiccant wheel cycle. The optimum solar collector surface has determined by taking into account of design parameters such as velocity of air, wheel speed, thickness of the desiccant and hydraulic diameter of the desiccant wheel and also operating conditions such as outside temperature, outside relative humidity, regeneration air temperature and total solar irradiance. For this... 

In this paper, LQG/LTR controller is designed for attitude control of the geostationary satellite at nominal mode. Usage actuator is the reaction wheel and control torque is determined by the LQR regulator. LQR controller signal has good performance, if all states are considered in feedback, but does not include model and sensors noises. Usage sensors are sun and earth sensors and EKF is used for estimation of noisy states. Then, LQG and LQG/LTR controllers are designed based on the estimated states, and are compared with LQR controller. The results show that robustness and performance of LQG/LTR are better than LQG and its control overshoot is smaller than LQR. The term that is provided in... 

In this article effects of sleepers defect on rail vehicle vibration have been investigated. Two parallel rails of the track have been modeled as Euler-Bernoulli beams on elastic points as rail pads. Also sleepers have been modeled as visco-elastic Euler-Bernoulli beams. It is assumed that, some sleepers under the rail track have been fractured and modeled by two beams. The wheelset has 5 DOF which are longitudinal, vertical and lateral movements plus roll and axial rotations. To determine normal contact force between wheel and rail, relative position of wheel and rail has been determined at each instant. Using the coordinate of each wheel points in rail coordinate system, the penetration of... 

In this paper, GyroSym, a compact highly-stable single-wheel robot is introduced. Symmetrical flywheels have been used as its stabilization mechanism to keep the wheel upright. Thanks to the type of the flywheel used, the dynamic equations of the robot is simplified, the torque needed to tilt the spin axis is reduced, and the space is drastically minimized. Besides, a centrifugal clutch is used to smooth the motion of the robot in forward motion. Two controllers, fuzzy and fuzzy-Padé, were implemented based on their ability to stabilize the robot. Although both prevented the GyroSym from falling over, neither can entirely cancel out the effects of nonlinear behaviors that is present in the... 

Historically, most of the maintenance tasks in rolling stock companies are devoted to Preventive Maintenance which leads to some problems such as erroneous maintenance work, unnecessary maintenance tasks, etc. Therefore, it is essential to develop effective maintenance strategies to deal with these problems. While the safety is a significant factor in rolling stock industries, the most well known and widely applied maintenance optimization strategy is so called Reliability Centered Maintenance (RCM). The aim of this paper is to discuss the implementation of RCM to make maintenance of rolling stock of the Raja Passenger Train Corporation more cost effective. Therefore, the paper presents RCM...