Wheel Load Variation Research Articles

Energy Efficient Torque Allocation Design Emphasis on Payload in a Light-Duty Distributed Drive Electric Vehicle

Light-Duty Electric Vehicle (LDEV) with a distributed drive powertrain provides several potential advantages in terms of flexibility, controllability and responsiveness over conventional powertrains. The precise distribution of driving and braking torque of such configuration is crucially vital for improving the overall performance and efficiency of the vehicles. This paper proposes a new torque allocation (TA) model emphasizing the wheel load variation due to the passenger occupancy payload. A light-duty vehicle model is developed along with the occupancy payload arrangement and a dynamic tire-road friction estimation method for the control system for wheel slip. This proposed TA algorithm uses offline optimization to derive the necessary transmissible torque to the driving wheels. Unlike conventional optimization, it adopts a set of predefined distribution coefficients. Therefore it can execute in a real time platform without high computation power and additional hardware requirements. The efficiency of the model is analyzed using Indian Urban Drive Cycle (IN-UDC). A comparative analysis using a traditional torque allocation model highlights the contributions of this novel torque allocation. The results obtained from various simulations demonstrate the effectiveness of the proposed new TA algorithm.

Analysis of the Influence of Suspension Actuator Limitations on Ride Comfort in Passenger Cars Using Model Predictive Control

Active suspension systems help to deliver superior ride comfort and can be used to resolve the objective conflict between ride comfort and road-holding. Currently, there exists no method for analyzing the influence of actuator limitations, such as maximum force and maximum rate of change, on the achievable ride comfort. This research paper presents a method that is capable of doing this. It uses model predictive control to eliminate the influence of feedback controller performance and to integrate both actuator limitations and necessary constraints on dynamic wheel-load variation and suspension travel. Various scenarios are simulated, such as driving over a speed bump and inner city driving, as well as driving on a country road and motorway driving, using a state-of-the-art quarter-car model, parameterized for a luxury class vehicle. It is analyzed how comfort, or in one scenario road-holding, can be improved with consideration for the actuator limitations. The results indicate that actuator rate limitation has a strong influence on vertical vehicle dynamics control system performance, and that relatively small maximum forces of around 1000 to 2000 N are sufficient to successfully reject disturbances from road irregularities, provided the actuator is capable of supplying the forces at a sufficiently high rate of change.

Theoretical cross-wind speed against rail vehicle derailment considering the cross-running wind of trains and the dynamic wheel-rail effects

In this paper, a theoretical formula was proposed that predicts the derailment index due to a cross wind applied to a rail vehicle considering the cross running wind condition of two running trains as well as the dynamic wheel-rail effects. The recently developed derailment theory on a wheelset was applied to this new cross wind derailment formula. Contrary to the conventional formulas, this new derailment formula was derived considering a dynamic derailment coefficient (Q/P) under normal running, the friction coefficient between the wheel and the rail, the wheel load variation, the cross running wind effects, and the cross wind. Using this proposed formula, the derailment pattern and the critical cross wind speed of derailment could be predicted for various cross running wind conditions of two running trains. Finally, for some typical examples, the results of this proposed formula were compared and verified with those of the conventional formulas and the numerical simulation of multi-body dynamics software, Recurdyn.

2C21 Development of secondary suspension for improvement of wheel load variation (Part1)(Safety-Vehicle)

When railway vehicles run at exit transition curve, track twist produce wheel load variation. Especially if vehicle has air suspension, behavior of leveling valve increases diagonal differential pressure (Twist component of unbalance of air suspension pressure). Increase of wheel load variation makes margin of tight curve passing safety small. In order to improve running safety, reducing wheel load variation is very important. In this paper, authors have developed newly secondary suspension "connecting of front and rear air springs" for reducing wheel load variation in transition curve. This valve system can flow small amount of air at low differential pressure and flow large amount of air at high differential pressure. The developed air suspension system has evaluated with trial running in the test line. The test data show diagonal differential pressure is improved proximately 40%.

2C22 Development of the secondary suspension for the improvement of the wheel load variation (Part2)(Safety-Vehicle)

Improving running safety in sharp curves, especially in transition curve, reducing wheel load variation is very important. When railway vehicle runs in transition curve section, superelevation gradually reduces continuously and the plane consisted of right and left rail is twisted. This track twist produce diagonal differential pressures of secondary suspensions in the car which makes unbalance of wheel load in the car. So we developed newly system "connecting front and rear air springs" to reduce wheel load variation. Connecting front and rear air springs has an effect of cancellation of diagonal differential pressures, which can be realized by additional air pipings and differential pressure valves. We installed this system in Tokyo Metro Chiyoda line train, and carried out test run to evaluate the effect of this system. The test data show wheel load variation rate of proposed system was improved compared to conventional system. And the diagonal differential pressure (equal to car body twist) was significantly improved with this system.The test results show that wheel load variation rate is improved approximately from 20% to 30%, as a result, derailment coefficient data was improved approximately from 15% to 25% for each curves in the test.

Study on the Wheel Load Variation Simulation Method of Automobile ABS Performance Test Bench

A method of wheel load variation simulation for automobile ABS performance test bench is presented in the paper. To simulate the wheel load variation of the detected vehicle, the wheel placement angle on the rollers can be changed by adjusting the wheelbase between the ABS performance test bench’s two rollers, which support the same wheel. Equivalent wheel load is defined to reflect wheel load variation simulation, and the relationship among the equivalent wheel load, roller adhesion coefficient and wheel placement angle is also be analyzed. The simulation results show that the equivalent wheel load is not only can greater than wheel load many times, but also can less than wheel load. The minimum equivalent wheel load is determined by the critical wheel placement angle.

Identification of Iron Rusts on Rail by X-Ray Diffraction and Vibrational Analysis

A periodical unevenness of the running surface of rails is formed on ascending slope of submarine railway tunnel. One of the causes has been concluded due to the combination of a low friction and wheel load variation induced by some kinds of iron oxides and oxyhydroxides with various coefficients of friction on the rail, though it has not been made clear yet. In this study, X-ray diffraction and Raman scattering spectroscopic analysis were attempted to identify iron rusts on the rail as a process to solve the periodic unevenness of the rail suffering many railway companies.

横風を受けた鉄道車両の挙動に関する動的解析モデルの構築および検証

It is very important to be able to estimate the critical wind speed of overturning precisely, because railway vehicles are becoming lighter and increasing running speed, which lead to conditions disadvantageous to prevention of railway accidents involving overturning of the vehicle by strong crosswind. Therefore, evaluation of the critical wind speed with consideration on the effect of dynamic behavior of the vehicle is required, that is, the difference between the static analysis and the dynamic analysis is needed to be clarified quantitatively. Thus, in order to analyze the dynamic behavior of the vehicle subjected to crosswind, we constructed a dynamic analysis model which was developed based on the static analysis model, and examined the effect of the frequency of the crosswind on the dynamic behavior of the vehicle. Further, in order to verify the validity of the dynamic simulation program prepared by using the dynamic analysis model, we conducted a full scale experiment applying lateral force to the vehicle dynamically. As a result, it has been verified that the dynamic simulation program is valid for evaluating the wheel load variation of the vehicle which is subjected to crosswind. Consequently, the effect of the frequency of crosswind on the bahavior of the vehicle has been clarified, the critical wind speed of overturning has been evaluated more precisely, and also the difference between the static analysis and the dynamic analysis has been evaluated quantitatively.

360545 ANALYTICAL STUDY OF THE MECHANISM OF WHEEL LOAD VARIATION ON A TWO-AXLE BOGIE(Safety,Technical Session)

The purpose of this study is to investigate the mechanism of wheel load variation of a high-speed train running on rail track with short-wavelength irregularity effecting on the running safety. In order to investigate the mechanism, the numerical simulation is conducted. The simulation model consists of the two-axle bogie and the track. The track consists of rail, rail pad, sleeper, ballast. The rail is expressed as the flexible beam described using the Absolute Nodal Coordinate Formulation in order to obtain the rail deformation more precisely. As a result of this study, we obtained further the information of the wheel load variation while two wheels passing on the rail with irregularity. That is, the wheel load variation rate of two-axle bogie model at 270km/h becomes larger in the case of the irregularity wavelength 1.1-1.2m as well as one-axle bogie model. However, the difference between the leading wheel and the trailing wheel occurs in terms of the magnitude. And the magnitude relation between the leading wheel and the trailing wheel changes according to the wavelength with the irregularity. We discuss the mechanism of these phenomenon obtained by the simulation.

362140 DEVELOPMENT OF SUBWAY BOGIE TO REDUCE WHEEL LOAD VARIATION(Bogie,Technical Session)

For subway vehicle that runs through many curve sections, the demand to increase speed at curve sections is increasing. On the other hand, subway lines also have characteristics of small super elevation transition rate at transition curve sections, and wheel load reduction at the transition curve sections should be minimized, especially in an empty condition, since excessive wheel load reduction may cause a derailment of the vehicle. In this paper, the authors examine factors causing wheel load variation such as distortion of vehicle body or bogie. By full vehicle model stand test, the authors have confirmed that distortion of vehicle body would be the most effective factor for a bogie with air suspension.

Wheel Load Variation in Coupled Motion Between Wheel and Flexible Track with Short-Wave Irregularity

The decrease of wheel load variation is one of the most important issues which must be solved in railway dynamics. The purpose of this study is to make clear the mechanism of wheel load variation by the numerical simulation by the analytical model which is based on the concept of the multibody dynamics. In this study, we were able to figure out the in-depth mechanism of the wheel load variation, particularly, concerning the phenomenon that the wheel load variation suddenly decreases with more than wheel velocity at which the 1st natural frequency of system consists with the irregularity passing frequency.

Analysis on Wheel Load Variation in Coupled Motion between Wheel and Track

The decrease of wheel load variation is one of the most important subjects in order to further enhance stability, safety and ride comfort of high-speed train. In this paper, we conduct the simulation analysis on wheel load variation in order to investigate the influence of the specifications of both vehicle and track on wheel load variation of high-speed train, and in order to derive the appropriate specifications to decrease the wheel load variation. As a result of the eigen value analysis and the time history response analysis, we figured out as follows : The wheel load variation is mainly caused by the vertical motion of the wheel/rail at the basis on the primary natural vibration of the wheel/rail system; the wheel load variation is influenced a great deal by the relation between the natural frequency of wheel rail and the frequency determined by both running speed and the interval of support springs.

Analysis on Wheel Load Variation in Coupled Motion Between Running Wheel and Track with Irregularity

The decrease of wheel load variation is effective in enhancing stability, safety of high-speed train. In this paper, we conduct the simulation analysis on wheel load variation in order to figure out the mechanism of wheel load variation in consideration of track irregularity such as sine wave and to investigate the influence of the relation between unsprung mass and static wheel load. As a result, we figured out as follows : The wheel load variation at high speed increases according as the wheel speed because the vertical inertia force of wheel increases widely by high-speed running along the flexible rail with irregularity. If sleeper passing frequency and the irregularity passing frequency is close to the primary natural frequency of the wheel/rail system, the wheel load variation becomes larger. The decrease of wheel mass is very effective in decreasing the wheel load variation in comparison with the decrease of static wheel load.

Evaluation of Countermeasures against Differential Settlement at Track Transitions

This paper describes a study which looked at the mechanism of wheel load variation that results from changes in railroad track stiffness, loose railroad ties on ballasted trackside, and other factors. Results are presented from a field inspection, a cyclic-movement loading test, and dynamic analysis performed on the ballasted trackside of the end portion of a slab track, as well as on a precast and prestressed concrete crossing. The paper also presents an evaluation of countermeasures against differential settlement occurring at track transitions. Resilient and larger railroad ties are shown to be the most effective in reducing ballast vibration and settlement

134 車輪と短波長狂いのある柔軟軌道の連成運動を考慮した輪重変動解析

134 車輪と短波長狂いのある柔軟軌道の連成運動を考慮した輪重変動解析

Ride comfort performance of different active suspension systems

This paper presents a comparative of different active and semi-active suspension systems in order to research the improvement in ride comfort and handling stability compared with the equivalent passive systems. The two-degrees-of-freedom model (quarter-car model) is employed in the analysis of seven different active suspension control strategies: LQR-LQG, Robust design, Kalman filter, Skyhook damper, Pole-assignment, Neural network and Fuzzy logic. Computer simulations of the different active models and the equivalent passive systems are performed to obtain the vertical acceleration of the sprung mass and the vertical wheel load variation. The vertical acceleration of the sprung mass is processed to evaluate the ride comfort behaviour and the vertical wheel load variation is used to evaluate the handling stability of the different active suspension control systems.

A401 QUASI-STATIC ANALYSIS OF THE WHEEL LOAD VARIATION OF PNEUMATIC SUSPESION RAILWAY VEHICLES ON TWISTED CURVES

Railway vehicles of pneumatic suspension have a tendency to produce large wheel road variation on a twisted curve due to operation of the height control valve of air springs installed between both side air springs of the truck. In this paper, equations of moment equilibrium of the pneumatic suspension vehicle on the twisted curves are introduced quasi-statically, and effects of nonlinear characteristics of the height control system on the wheel load variation are analyzed. Analytical results are also examined by using the full size model test apparatus. The result shows preset pressure value of the air pressure balance valve plays an important role on the wheel load.

Study on the Wheel Load Variation of the Rail Vehicle in Air Spring Deflation.

Study on the Wheel Load Variation of the Rail Vehicle in Air Spring Deflation.

Probabilistic analysis of vehicle vibrations

The dynamical analysis of random vehicle vibrations requires an integrated investigation of guideway roughness, nonlinear vehicle dynamics and human sensation to vibration exposure. The stochastic analysis of the total system is discussed in the frequency domain and the time domain. Nonlinearities are considered by statistical linearization techniques. Then, the variances of wheel load variation, car body acceleration and human sensation are determined by spectral density analysis as well as by covariance analysis.