A Study of the Wheel Geometry Effect on the Dynamic Behavior of Railroad Vehicles

2005 ◽  
Author(s):  
Ahmed A. Shabana ◽  
Mahmoud Tobaa ◽  
Khaled E. Zaazaa
Keyword(s):  
Critical Speed ◽  
Single Point ◽  
Vehicle Stability ◽  
Point Contacts ◽  
Vehicle Model ◽  
Geometric Properties ◽  
Railroad Vehicles ◽  
Wheel Profile ◽  
The Stability ◽  
Railroad Vehicle

The effect of the geometry of a wheel profile that allows only a single point of contact between the wheel and the rail is investigated in this study. The local geometric properties of this profile are compared with the local geometric properties of a profile that allows for two-point contacts in order to understand the basic differences between the two profiles. A simple model is first used to examine the effect of the profile geometry on the stability and nonlinear dynamics of a suspended wheel set. The results obtained in this paper show that the wheel profile can significantly alter the critical speed. Using surface parameters that define the wheel and rail geometry, the global representations of the positions of the points on the wheel and rail surfaces are obtained and used to define the conditions of the contact between the wheel and the rail. Numerical results are presented for a full railroad vehicle model and the effect of the wheel profile on the vehicle stability is investigated. A comparison between the results obtained using the two wheel profiles in the case of wheel climb scenarios is presented.

Effect of the Wheel Geometric Design on the Nonlinear Dynamics of Railroad Vehicles

2005 ◽  
Vol 128 (5) ◽  
pp. 1130-1140 ◽  
Author(s):  
Ahmed A. Shabana ◽  
Mahmoud Tobaa ◽  
Khaled E. Zaazaa
Keyword(s):  
Nonlinear Dynamics ◽  
Simple Model ◽  
Single Point ◽  
Contact Forces ◽  
Geometric Properties ◽  
Normal Contact ◽  
Railroad Vehicles ◽  
Contact Points ◽  
Contact Constraint ◽  
Wheel Profile

The effect of the geometry of a wheel profile that allows only a single point of contact with the rail is investigated in this study. The local geometric properties of this profile are compared with the local geometric properties of a profile that allows for two-point contacts in order to understand the basic differences between the two profiles. A simple model is first used to examine the effect of the profile geometry on the stability and nonlinear dynamics of a suspended wheel set. The results obtained using this simple model show that the geometry of the wheel profile can significantly alter the critical speed. A computational approach is then used to investigate and quantify the effect of the wheel geometry wheel on the dynamics and stability of railroad vehicles. Two methods, the contact constraint and elastic formulations, are used. The contact constraint method employs nonlinear algebraic kinematic constraint equations to describe the contact between the wheel and the rail. The contact kinematic constraints, which eliminate one degree of freedom and do not allow for wheel/rail separation, are imposed at the position, velocity and acceleration levels. The system equations of motion are expressed in terms of the generalized coordinates and the nongeneralized surface parameters. In the formulations based on the elastic approach, the wheel has six degrees of freedom with respect to the rail, and the normal contact forces are defined as a function of the penetration using Hertz’s contact theory or using assumed stiffness and damping coefficients. In the elastic approach that allows for wheel/rail separation, the locations of the contact points are determined by solving a set of algebraic equations. The distribution of the contact forces resulting from the use of the two profiles that have different geometric properties is investigated using the two methods. Numerical results are presented for a full railroad vehicle model and the effect of the wheel profile on the vehicle stability is investigated.

Stable headway prediction of vehicle platoon based on the 5-degree-of-freedom vehicle model

2018 ◽  
Vol 233 (6) ◽  
pp. 1570-1585 ◽  
Author(s):  
Shuming Shi ◽  
Ling Li ◽  
Yu Mu ◽  
Guanghui Chen
Keyword(s):  
Ad Hoc Network ◽  
Ad Hoc ◽  
Rotational Velocity ◽  
Autonomous Vehicle ◽  
Degree Of Freedom ◽  
Vehicle Stability ◽  
Vehicle Model ◽  
Vehicle System ◽  
Vehicle Platoon ◽  
The Stability

Vehicular ad hoc network and cooperative adaptive cruise control system make vehicle platooning with small headway feasible. In the study of the autonomous vehicle platoon system under the vehicular ad hoc network condition, the linear vehicle model is usually used to analyze the minimum space-gap, safety space-gap, and so on. However, the stability of nonlinear vehicle system shows that there are limitations when using the linearized vehicle model to analyze vehicle stability. The linear model cannot reflect the influence of the system nonlinear coupling on the vehicle stability. Therefore, in this paper, we use the validated 5-degree-of-freedom (longitudinal velocity, lateral velocity, yaw rate, front wheel rotational velocity, and rear wheel rotational velocity) nonlinear model to analyze the stable intra-platoon spacing of the autonomous vehicle platoon system under the condition of VANET. In order to study the safety intra-platoon spacing of vehicle platoon running in the complex path, a following controller is designed for vehicle platoon running in the corners. The controller adopts the method of vertical and horizontal decentralized control. The longitudinal control is to realize the expected space-gap of vehicles in vehicle platoon, and the lateral control is to achieve the position and orientation following of the preceding vehicle. Based on the stability verification of the following controller, the following control characteristics of vehicle system are analyzed, and the stable headway required for vehicles in vehicle platoon running in the complex path is predicted by the method of simulation experiment.

Fuzzy Logic Based Vehicle Stability Enhancement Through Combined Differential Braking and Active Front Steering

2005 ◽  
Author(s):  
J. Ahmadi ◽  
A. Ghaffari ◽  
R. Kazemi
Keyword(s):  
Fuzzy Logic ◽  
Steering System ◽  
Vehicle Stability ◽  
Fuzzy Logic Controllers ◽  
Vehicle Model ◽  
Active Front Steering ◽  
Highly Nonlinear ◽  
Road Condition ◽  
The Stability ◽  
Stability Enhancement

This paper examines the usefulness of a combined differential braking and active front steering system on the stability enhancement of a vehicle. The two manipulated inputs for steering intervention are the added front steer angle and the brake torque, where the later is applied at only one wheel at a time. In this study active front steering controller is designed independent of differential braking controller. Since the yaw and lateral motions are highly nonlinear, two fuzzy logic controllers are constructed to compensate the effects of road condition and parameter variation. Computer simulations using nonlinear seven degree of freedom vehicle model show the strong capability of the combined approach and its relative merit compared to the case that one subsystem is actuated.

Impact monitoring characteristics of piezoelectric paint sensor by thermal fatigue analysis for railroad vehicle applications

2020 ◽  
Vol 19 (6) ◽  
pp. 1951-1962
Author(s):  
Kyungwho Choi ◽  
Mun-Young Hwang ◽  
Donghoon Kang ◽  
Myeongcheol Kang ◽  
Dahoon Ahn ◽  
...  
Keyword(s):  
Thermal Fatigue ◽  
Aerodynamic Drag ◽  
Test Results ◽  
Railroad Vehicles ◽  
Additional Layer ◽  
Impact Monitoring ◽  
Nano Powder ◽  
The Stability ◽  
The Impact ◽  
Railroad Vehicle

The strong aerodynamic drag under a railroad vehicle in motion causes the track ballast to fly up and around. The flying ballast can collide with the underside of the coach, damaging the electronics installed there. There are even cases wherein the aerodynamics of fast-moving train causes the gravel to hit the side of the coach and break the windows. Extensive and numerous studies are underway to reduce the damage caused by such phenomena. In this study, a “smart paint sensor” for impact monitoring was fabricated using piezoelectric nano powder and commercial paint for railroad vehicles, and the application of impact monitoring to railroad vehicles was analyzed. The process was simplified because the use of commercial paint eliminated the need to apply an additional layer of functionalized paint. Furthermore, the fact that the paint can be evenly sprayed on a large surface made it suitable for use on large and intricate objects such as a railroad vehicle bogie. Because railroad vehicles are exposed to thermal stress for a long period of time, a thermal fatigue test was conducted in order to figure out the stability of the polymer-based material, which is relatively vulnerable to temperature variations. The test results were used to analyze the impact sensitivity of the piezoelectric paint sensor. For the analysis, a full-size mock-up of the railroad vehicle bogie and an impact monitoring system with piezoelectric paint sensor were implemented in order to visualize the impact signals from differently shaped objects with large surfaces.

Effect of Independently Rotating Wheels on the Dynamic Performance of Railroad Vehicles

2007 ◽  
Author(s):  
Khaled E. Zaazaa ◽  
Brian Whitten
Keyword(s):  
Dynamic Performance ◽  
Equations Of Motion ◽  
Lateral Force ◽  
Ride Quality ◽  
Vehicle Dynamic ◽  
Vehicle Performance ◽  
Railroad Vehicles ◽  
Judicious Choice ◽  
Wheel Profile ◽  
Railroad Vehicle

In recent decades, there has been a considerable effort in improving railroad vehicle dynamic performance. This involves high operational speed with stable behavior, better curving performance, better ride quality, and increased life of the wheel and rail profiles. To achieve this goal, the use of independently rotating wheels (IRW) is proposed as one potential option. Using IRW either partially or totally decouples the pitch rotation of the two wheels of the “wheelset”, thereby reducing or eliminating the longitudinal creepage and thus wheelset hunting motion. On the other hand, the longitudinal creepage is no longer available to provide steering assistance in curves, and continuous flange contact during curving is expected. However, by judicious choice of wheel profile and careful truck design, the lateral force between wheel and rail during curving can be reduced, decreasing the wear on both the wheel and rail profiles. Therefore, such solution is assumed to achieve higher stable operational speed and improved curving behavior. In this paper, the effect of using IRW on railroad vehicle performance is examined. The equations of motion of a single wheelset model and a suspended wheelset model that use IRW are presented and compared with those for similar models that use a rigid wheelset. Using a newly developed general multibody code, a complete vehicle model that uses IRW is examined and compared with one that uses rigid wheelsets. The effect of the IRW system on vehicle dynamic performance is quantitatively presented. In addition, the ability of the contact formulations used in this multibody code for modeling the IRW system is confirmed.

Optimal Torque Distribution for the Stability Improvement of a Four-Wheel Distributed-Driven Electric Vehicle Using Coordinated Control

2016 ◽  
Vol 11 (5) ◽  
Author(s):  
Xizheng Zhang ◽  
Kexiang Wei ◽  
Xiaofang Yuan ◽  
Yongqi Tang
Keyword(s):  
Electric Vehicle ◽  
Sliding Mode ◽  
Single Point ◽  
Coordinated Control ◽  
Least Square ◽  
Vehicle Stability ◽  
Tracking Accuracy ◽  
Torque Distribution ◽  
Lqr Problem ◽  
The Stability

This paper presented an optimal torque distribution scheme for the stability improvement of a distributed-driven electric vehicle (DEV). The nonlinear dynamics and tire model of the DEV are constructed. Moreover, the single-point preview optimal curvature model with the proportional-integral-derivative (PID) process is developed to simulate the driver's behavior. By using coordinated control and sliding mode control, a three-layer hierarchical control system was developed. In the upper level, the integral two degree-of-freedom (DOF) linear model is used to compute the equivalent yaw moment for vehicle stability. With the actuators' restrictions, the middle level solved the linear quadratic regulator (LQR) problem via a weighted least square (WLS) method to optimally distribute the wheel torque. In the lower level, a slip rate controller (SRC) was presented to reallocate the actual torques based on the sliding mode method. The simulation results show that the proposed scheme has high path-tracking accuracy and that vehicle stability under limited conditions is improved efficiently. Moreover, the safety under actuator failure is enhanced.

scholarly journals Steady-state $$\dot{V}{\text{O}}_{2}$$ above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners

2021 ◽  
Author(s):  
Rebekah J. Nixon ◽  
Sascha H. Kranen ◽  
Anni Vanhatalo ◽  
Andrew M. Jones
Keyword(s):  
Steady State ◽  
Critical Speed ◽  
Lactate Concentration ◽  
Practical Interest ◽  
Blood Lactate Concentration ◽  
Distance Runners ◽  
Severe Intensity ◽  
The Stability ◽  
Trained Runners ◽  
Over Time

AbstractThe metabolic boundary separating the heavy-intensity and severe-intensity exercise domains is of scientific and practical interest but there is controversy concerning whether the maximal lactate steady state (MLSS) or critical power (synonymous with critical speed, CS) better represents this boundary. We measured the running speeds at MLSS and CS and investigated their ability to discriminate speeds at which $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 was stable over time from speeds at which a steady-state $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 could not be established. Ten well-trained male distance runners completed 9–12 constant-speed treadmill tests, including 3–5 runs of up to 30-min duration for the assessment of MLSS and at least 4 runs performed to the limit of tolerance for assessment of CS. The running speeds at CS and MLSS were significantly different (16.4 ± 1.3 vs. 15.2 ± 0.9 km/h, respectively; P < 0.001). Blood lactate concentration was higher and increased with time at a speed 0.5 km/h higher than MLSS compared to MLSS (P < 0.01); however, pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 did not change significantly between 10 and 30 min at either MLSS or MLSS + 0.5 km/h. In contrast, $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 increased significantly over time and reached $$\dot{V}{\text{O}}_{2\,\,\max }$$ V ˙ O 2 max at end-exercise at a speed ~ 0.4 km/h above CS (P < 0.05) but remained stable at a speed ~ 0.5 km/h below CS. The stability of $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 at a speed exceeding MLSS suggests that MLSS underestimates the maximal metabolic steady state. These results indicate that CS more closely represents the maximal metabolic steady state when the latter is appropriately defined according to the ability to stabilise pulmonary $$\dot{V}{\text{O}}_{2}$$ V ˙ O 2 .

scholarly journals Electromigration-induced directional steps towards the formation of single atomic Ag contacts

2020 ◽  
Vol 11 ◽  
pp. 680-687
Author(s):  
Atasi Chatterjee ◽  
Christoph Tegenkamp ◽  
Herbert Pfnür
Keyword(s):  
Fourier Transforms ◽  
Single Point ◽  
Point Contact ◽  
Single Atom ◽  
Point Contacts ◽  
Cross Sectional ◽  
Shell Effects ◽  
Theoretical Approaches ◽  
Average Grain Size ◽  
Thinning Process

Even though there have been many experimental attempts and theoretical approaches to understand the process of electromigration (EM), it has not been quantitatively understood for ultrathin structures and at grain boundaries. Nevertheless, we showed recently that it can be used reliably for the formation of single atomic point contacts after careful pre-structuring of the initial Ag nanostructures. The process of formation of nanocontacts by EM down to a single-atom point contact was investigated for ultrathin (5 nm) Ag structures at 100 K by measuring the conductance as a function of the time during EM. In this paper, we compare the process of thinning by EM of structures with constrictions below the average grain size of Ag layers (15 nm) with that of structures with much larger initial constrictions of around 150 nm having multiple grains at the centre constriction prior to the formation of a point contact. Even though clear morphological differences exist between both types of structures, quantized conductance plateaus showing the formation of single point contacts have been observed for both. Here we put emphasis on the thinning process by EM, just before a point contact is formed. To understand this thinning process, the semi-classical regime before the contact reaches the quantum regime was analyzed in detail. For this purpose, we used experimental conductance histograms in the range between 2G 0 and 15G 0 and their corresponding Fourier transforms (FTs). The FT analysis of the conductance histograms exhibits a clear preference for thinning along the [100] direction. Using well-established models, both atom-by-atom steps and ranges of stability, presumably caused by electronic shell effects, can be discriminated. Although the directional motion of atoms during EM leads to specific properties such as the instabilities mentioned, similarities to mechanically opened contacts with respect to cross-sectional stability were found.

A Study of the Lateral Stability of Railroad Vehicles Using a Nonlinear Constrained Multibody Formulation

2001 ◽  
Author(s):  
Davide Valtorta ◽  
Khaled E. Zaazaa ◽  
Ahmed A. Shabana ◽  
Jalil R. Sany
Keyword(s):  
Stability Analysis ◽  
Linear Stability ◽  
Linear Theory ◽  
Linear Stability Analysis ◽  
Numerical Study ◽  
Operating Conditions ◽  
Lateral Stability ◽  
Railroad Vehicles ◽  
Contact Formulation ◽  
The Stability

Abstract The lateral stability of railroad vehicles travelling on tangent tracks is one of the important problems that has been the subject of extensive research since the nineteenth century. Early detailed studies of this problem in the twentieth century are the work of Carter and Rocard on the stability of locomotives. The linear theory for the lateral stability analysis has been extensively used in the past and can give good results under certain operating conditions. In this paper, the results obtained using a linear stability analysis are compared with the results obtained using a general nonlinear multibody methodology. In the linear stability analysis, the sources of the instability are investigated using Liapunov’s linear theory and the eigenvalue analysis for a simple wheelset model on a tangent track. The effects of the stiffness of the primary and secondary suspensions on the stability results are investigated. The results obtained for the simple model using the linear approach are compared with the results obtained using a new nonlinear multibody based constrained wheel/rail contact formulation. This comparative numerical study can be used to validate the use of the constrained wheel/rail contact formulation in the study of lateral stability. Similar studies can be used in the future to define the limitations of the linear theory under general operating conditions.

The stability analysis using Lyapunov exponents for high-DOF nonlinear vehicle plane motion

2021 ◽  
pp. 095440702110433
Author(s):  
Shuming Shi ◽  
Fanyu Meng ◽  
Minghui Bai ◽  
Nan Lin
Keyword(s):  
Stability Analysis ◽  
Quantitative Analysis ◽  
Lyapunov Exponents ◽  
Plane Motion ◽  
Vehicle Model ◽  
Motion Stability ◽  
Motion System ◽  
Nonlinear Vehicle Model ◽  
The Stability ◽  
Different Characteristics

The Lyapunov exponents method is an excellent approach for analyzing the vehicle plane motion stability, and the researchers demonstrated the effectiveness under 2-DOF vehicle model. However, whether the Lyapunov exponents approach can effectively reveal the characteristics of high-DOF nonlinear vehicle model is the key problem at present. In this paper, the Lyapunov exponents is applied to quantitatively analyze the stability of the nonlinear three and five degree of freedom vehicle plane motion system. The different characteristics between 2-DOF and high-DOF model are revealed and explained by using Lyapunov exponents. It illustrates the feasibility of using Lyapunov exponents to analyze the stability of high-DOF vehicle models, which supplements and perfects the existing quantitative analysis conclusion.

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