Wheel-rail Adhesion Research Articles

Wheel flat detectability for Y25 railway freight wagon using vehicle component acceleration signals

A wheel flat is a common fault in railway vehicles that may develop after incorrect brake application, or localised wheel-rail adhesion reduction. Operators detect wheel flats using wayside systems that are not capable of delivering real-time alarms. A wheel flat defect was modelled and introduced to a railway wagon multibody dynamic simulation to study the vehicle dynamic behaviour triggered by such wheel tread defect. Bogie-based and car body-based wheel flat detection was evaluated to determine eventual hardware robustness and signal processing requirements for on-board wheel flat detection devices. Various vehicle operating conditionds and wheel flat defects were simulated to analyse the wheel flat impact propagation throughout the railway vehicle bodies. Wheel defect detectability was assessed using detectability indicators (DIs) based on envelope power spectrum analysis, crest factor and RMS. It was found that bogie and car body-based wheel flat detectability is highly dependent on the track characteristics. The wheel flat signature was reduced in the wheelset-bogie and bogie-car body interfaces, indicating that advanced signal processing techniques are required for bogie-based and car body-based wheel flat detection systems. The DIs showed clear differences between healthy and faulty wheelset and bogie frame acceleration signals, which is promising for eventual on-board wheel flat detection systems.

Train braking simulation with wheel-rail adhesion model

ABSTRACT This paper modelled the vehicles in conventional Longitudinal Train Dynamics (LTD) as 2D models that considers suspensions and wheel-rail contact. The Polach model was used as the adhesion model for faster computing speeds. A 2D train model was developed and solved using a parallel computing technique called Message Passing Interface. A train with the configuration of 1 locomotive + 120 wagons + 1 locomotive + 120 wagons was simulated in three different braking scenarios: emergency brake, full-service brake and minimum service brake. The same simulations were also conducted using a LTD model and the results are compared with those of the 2D train model. The comparisons indicate that: (1) wheelset rotational inertia needs to be considered in LTD models to achieve matched results with the 2D train model; (2) in most cases, simulated coupler forces from the 2D train model are slightly lower than those from the LTD model; (3) during minimum service brake and full-service brake, the differences of simulated coupler forces between the two models are lower than 100 kN; and (4) during emergency brake, a maximum difference of 266 kN was simulated, which accounts for 35% of the maximum force simulated by the LTD model.

An analysis of the self-excited torsional vibration of high-speed train drive system

In this paper, a simplified torsional vibration model of drive system with three degrees of freedom is established, and the elasticity of wheelset is considered. In addition to the same wheel-rail adhesion condition for the two wheels, the different wheel-rail adhesion conditions for the two wheels have been considered for the first time, and the mechanism of the vibration forms is explained from the viewpoint of energy. The nonlinear system is linearized at the origin (equilibrium position), and the critical stability curve of the linearized system is drawn according to the eigenvalues of the linearized system in the state space. The results show that the vibration forms of the system are mainly determined by the relationships between the average creep rate and the critical creep rate of the wheel driven directly by motors. When the resistance moments do positive work on the system, they input energy to the system, and the responses do not tend to the origin and produce self-excited vibration. When the resistance moments do negative work on the system, they dissipate energy to system, and the responses tend to the origin. For the linearized system at the origin, the system is more stable at the origin when following factors occur, a gentler negative slope of the adhesion curve, a faster speed, a lighter wheel load, and a larger the moment of inertia of wheels.

Optimal Utilization of Adhesion Force for Heavy-Haul Electric Locomotive Based on Extremum Seeking with Sliding Mode and Asymmetric Barrier Lyapunov Function

An optimal utilization of adhesion force based on extremum seeking with sliding mode (SMES) and asymmetric barrier Lyapunov function (ABLF) is proposed for heavy-haul electric locomotives (HHELs), which can eliminate the wheel skidding at optimal adhesion point and achieves maximum traction for HHELs. First, the state equation of wheel-rail adhesion control system is described. The optimal utilization of adhesion force and anti-slip control are analyzed considering the condition changes at the wheel-rail surface. Then, the nonsingular terminal sliding mode observer (NTSMO) is designed to achieve the accurate adhesion coefficient of the wheel-rail. Finally, the SMES method for HHEL is developed to obtain the optimal slip speed and the maximum adhesion coefficient of the uncertain wheel-rail surface. Meanwhile, the ABLF controller is designed to achieve anti-slip control for HHELs in the optimal adhesion state. Comparing with the conventional differential acceleration control (DAC) method, the simulations and experiments verify that the proposed method can achieve optimal adhesion anti-slip control with quick dynamic response, and the HHEL achieves maximum traction.

Study of wheel-rail adhesion during braking maneuvers

The present work aims to better understand the phenomenon of adhesion under degraded conditions during railway braking maneuvers with the aim of optimizing the anti-slip algorithms in order to reduce damage to the profiles of wheels and rails and to minimize the braking distance. The proposed approach is based on the analysis of experimental data acquired during braking tests carried out on track, considering different types of vehicles and different types of contaminants, able to reproduce the typical degraded adhesion conditions occurring during normal operation. The work describes a numerical model that allows to evaluate the dynamics of the vehicle during the braking operation and to correlate the pressures to the brake cylinder, which are related to the braking forces, and the angular velocities measured on the axles of the vehicle, with the adhesion coefficient.

Development of Novel Composite Powder Friction Modifier for Improving Wheel-rail Adhesion in High-speed Train

Development of Novel Composite Powder Friction Modifier for Improving Wheel-rail Adhesion in High-speed Train

Aspects regarding braking process of passenger trains with different braking systems in composition

The paper investigates the influence of different braking systems on the braking process of railway passenger vehicles, considered individual, as well as in train composition. The study focuses on the braking capacity – evaluated by stopping distance – and on the longitudinal dynamic of train, involving vehicles fitted with either disc brakes in fast-action, or cast iron block brakes in high power action mode. The specific dependence of the correspondent friction engenders particular braking characteristics. If associated to the limited braking forces by wheel-rail adhesion, different stopping distances result, while time evolution of braking process generates specific response of in-train forces, depending on vehicles’ combination in the train body. The study is based on MATLAB numerical simulations. For higher accuracy, experimental data of air pressure evolution in brake cylinders were adequately implemented. Simulations were performed for trains consisting of five coaches on four axles hauled by a six axle locomotive. All possible combinations of braking characteristics in the train composition were considered. Compression and tension forces in couplers and stopping distances are presented as results. The current study continues our previous research in this area. To our knowledge, such aspects of braking process in passenger trains were not investigated by other authors.

Study on the comfort of high-speed train drivers in a windy environment

Conducting the study on the comfort of high-speed train drivers in a windy environment, this paper based on the logical sequence of “train aerodynamic characteristics - vehicle dynamic response - human biomechanical properties - human body comfort evaluation”. Taking the domestic CRH3 high-speed train as the research object. Firstly, the aerodynamic loads acting on the car bodies of the train under different wind speeds and different vehicle speeds were calculated. Then considering the effect of the wheel-rail adhesion and the irregularity of the track line, establish a vibration transfer model of ‘rail - wheelset - bogie - carriage - seat’, the aerodynamic loads are loaded onto the train to calculate vehicle dynamics and train vibration response under different operating conditions, the vibration characteristics of carriages and seats are obtained. Subsequently, the seat-human vibration transfer model were established and the seat vibration response was introduced into the human dynamics model to calculate the vibration response of different body parts of the driver under different operating conditions. And on the basis which are mentioned above, we summarized the influence rule of wind speed and train speed on human vibration response, From the human body's own point of view, the main factors affecting comfort and the mechanism of action were analyzed. Finally, the comfort standard was integrated to evaluate the comfort of the driver.

Analysis of the influence of magnetic stiffness on running stability in a high-speed train propelled by a superconducting linear synchronous motor

There are two major obstacles that prevent a conventional train from achieving high speed: the limitation of wheel–rail adhesion and the increase of instability in the wheel–rail running dynamics. To overcome these problems, a new hybrid train model is introduced in this study. This train utilizes a superconducting linear synchronous motor (SC-LSM), instead of a traction motor, for propulsion; therefore, this train does not have the limitation of adhesion between the wheel and the rail. Using an SC-LSM also improves the stability of the train during high-speed operations. The magnetic stiffness between the train and the guideway is additionally generated by using the SC-LSM, which is favorable for the running stability at a high speed. This study focuses on the magnetic stiffness and its effect on the running stability in the proposed hybrid train model. First, the magnetic stiffness in the SC-LSM is investigated both theoretically and experimentally. Then, a train dynamic model including the magnetic stiffness is developed and the effect of magnetic stiffness on the running stability is analyzed through various simulations.

Adhesion Control Strategy Based on the Wheel-Rail Adhesion State Observation for High-Speed Trains

In this paper, an adhesion control strategy based on the wheel-rail adhesion state observation is proposed for high-speed trains. First, the high-speed train single axle dynamics model is established. Then, a modified adhesion control method is proposed. The scheme observes the tangential force coefficient between wheel and rail through full dimension observer and forecasts the slope of the adhesion-slip curve by the recursive least squares method with forgetting factor. Meanwhile, a feasibility analysis of the method and the control parameters tuning is conducted. Afterwards, the experimental study of the proposed adhesion control is carried out based on a 5.5 kW induction motor drag platform using dSPACE simulation technology. The experimental results confirm the feasibility of the adhesion control method proposed in this paper. Using the proposed adhesion control method can achieve high wheel-rail adhesion performance under variable complex road conditions.

Deformation processes within wheel-rail adhesion in contact area

The study of working surface deformation during interaction of open-pit locomotive tires allowed defining outstanding features of phenomena occurring in the contact area of interacting surfaces. It was found that processes typical for plastic saturated contact occur in the area of wheel-rail interaction of industrial railway transport. In case of plastic deformation exposed to heavy loads typical for open-pit locomotives, upon all rough surfaces of the contour contact area being fully deformed, the frame on which they are found is exposed to plastic deformation. Plastic deformation of roughness within the contact area of interacting surfaces leads to the increase in the actual area of their contact and, therefore, increases the towing capacity of mining machines. Finally, the available data on deformation characteristics with regard to processes occurring in the contact area of wheel-rail interaction will allow making theoretical forecasts on the expected design value of friction coefficient and, therefore, the towing capacity of open-pit locomotives.

About the influence of wheel-rail adhesion on the maximum speed of trains

Wheel-rail adhesion is a fundamental aspect in rail transport, with high impact on traction and braking of trains. In the case of high speeds trains, wheel-rail adhesion is particularly important, as the maximum usable traction force is limited by the adhesion force. The present paper analyses the influence of wheel-rail adhesion on the maximum speed of trains, considering ranges of usual values for the track gradient and the adhesion coefficient and the real data of two Japanese high-speed trains. Analysis shows that low adhesion and high track gradient result in significant reduction of train speed.

Online Accurate Estimation of the Wheel-Rail Adhesion Coefficient and Optimal Adhesion Antiskid Control of Heavy-Haul Electric Locomotives Based on Asymmetric Barrier Lyapunov Function

This paper proposes a new scheme of online accurate estimation of wheel-rail adhesion coefficient and optimal adhesion antiskid control of heavy-haul electric locomotives (HHEL) based on sliding mode and asymmetric barrier Lyapunov function (ABLF) theory. To achieve optimal adhesion control of the HHEL, it is necessary to precisely estimate the wheel-rail adhesion coefficient. However, the adhesion coefficient is difficult to be measured with a conventional physical sensor. The first novelty of this paper is to design a smart adhesion coefficient sensor based on sliding mode observer (SMO). The perception of the adhesion coefficient is transformed into the observation of load torque of the traction motors, and the wheel-rail adhesion coefficient is further calculated by using the load torque observed value. The HHEL achieves maximum traction from operating in the optimal adhesion point. However, wheel skidding is most likely to occur at this point. According to the changing trend of the adhesive coefficient characteristic curve, the operating state of a locomotive can be divided into two regions: the stable and skid regions. The second novelty of this paper is the adaptation of ABLF to guarantee that the HHEL operated at a stable region and the optimal adhesion antiskid control of HHEL is achieved. Finally, the simulation and experimental results verify the feasibility and effectiveness of the proposed method.

Коэффициент использования сцепной массы локомотива с групповым тяговым приводом колесных пар

Objective: To improve accuracy of analytical calculation of adhesive weight of constructed and newly projected locomotives with wheelset group tractive drive. To bring out analytical dependence of a locomotive’s adhesive weight usage coefficient from a number of wheelsets in a group tractive engine considering constructive features of a vehicle, operating conditions and power equipment cycle of operation. Methods: Analytical dependences and a mathematical model were obtained on the basis of higher mathematics, laws of theoretical mechanics, reliability theory, probability theory, wheel-rail adhesion theory and the laws of self-excited frictional oscillations during slippage. Results: Mathematical model was developed to determine the highest value of a twisting moment, in the process of which occurs different slippage of a wheelset group tractive drive of a locomotive, taking into account the stochastic character of wheel-rail adhesion, shaking at the moment of starting and in the process of running. Characteristic curve of equalizing factor was plotted from a generalized parameter of a locomotive tractive drive. Practical importance: Analytical dependences make it possible to identify the right adhesive weight of a locomotive with wheelset group tractive drive for conducting traction calculations and the assessment of locomotive’s tractive capacity in the process of operation on different cycles of power equipment and movement speed. The level of dynamic load on group tractive drive components was determined, taking into account constructive features of trucks and power transmission, such as the jet thrust location of wheelset axial gear units, as well as maintenance conditions – movement speed and irregularities of a railway track. The results of the study may be applied in projecting the new and constructed locomotives.

Taking Traction Control to Task: High-Adhesion-Point Tracking Based on a Disturbance Observer in Railway Vehicles

Railway vehicles have been based on a wheel-rail system since the system's origination. Therefore, the adhesion-coupling behavior between wheel and rail is the fundamental element of railway traction [1]. However, low vehicle wheel-rail adhesion caused by high humidity, rain, snow, oil, or decomposing leaves is a common problem that can cause damage to some elements of the traction system and decrease traction performance [2]. It may even give rise to safety problems and reduce comfort, not to mention delays and their corresponding economic impact. Good traction control to ensure the system is working at high adhesion point is therefore critical and mandatory for the traction control units (TCUs) [2]-[6].

About the influence of wheel slide protection devices action on longitudinal dynamic of trains

Wheel slide protection devices (WSPD) are destined to avoid important sliding of wheels during braking actions in case of temporarily impaired wheel-rail adhesion by correspondent reductions of air pressure in brake cylinders. Accordingly, longer braking distances and higher longitudinal in-train forces occur, potentially affecting the traffic safety and the passengers comfort. A general analyse and evaluation of these effects are the main targets of the present study. The theoretical considerations are sustained by simulations of braking process, considering situations of normal, respectively diminished wheel-rail adhesion determining random actuations of WSPD. The air pressure evolution in brake cylinders of was experimentally determined on a computerized brake system test stand and adequately used as input in simulations. The results indicate an increase of in-train forces and a more complex evolution of the longitudinal dynamic actions between the vehicles in the case of degraded wheel-rail adhesion, when the random actuation of WSPD have major influence in the whole braking process.

TECHNIQUE OF MEASUREMENT OF WORKING RAIL PROFILE CURVATURE RADIUS. ERRORS AT INDIRECT MEASUREMENTS

The article suggests a practical method of indirect curvature radius measurements of the working surface worn profile due to rail operation to create a conformal contact locomotive wheel tread with the rail. Conformal contact can provide an increase of the coefficient wheel-rail adhesion in the contact spot and lead to contact stress decrease due to an increase of the actual contact area of the interacting surfaces. The measured radius of curvature is used to restore the worn rail profile by of the rail surface grinding. It is established that in connection with the presence of random factors affecting on the surface of driving path at interaction of the locomotive wheel with the rail, random errors should be excluded from the obtained measurement results or the magnitude of the random components of errors should be estimated. At indirect measurements, it is not easy to find the best estimate of the true value of the measured size because of the unknown law of error distribution. On the basis of theoretical studies, the paper justifies a simplified formula for determination of the variance of the indirect measurement function of rail profile curvature radius according to the mathematical expectations and variances of the measured arguments. Simultaneous measurement of several arguments of the indirect measurement function leads to a correlation dependence of the arguments, that is taken into account in the proposed technique. Based on the measurement data, confidence intervals are constructed to estimate the mathematical expectation and the standard deviation of the radius of curvature of the rail. The question of choosing the number of measurements to achieve a specified accuracy of the curvature radius of the rail surface profile is considered.

Introducing wheel-rail adhesion control into longitudinal train dynamics

Introducing wheel-rail adhesion control into longitudinal train dynamics

Hybrid Propulsion Unit

The authors presented a conceptual idea of a high-speed mainline with a maximum speed of 400–450 km/h. The use of rotary engines requires more energy at high speeds, there are difficulties with current collection, wheel-rail adhesion, etc. At the same time, the use of a linear traction motor at low speeds is not justified from an economic point of view, but efficient at high speed in terms of operation. In this regard, an option of a combined or hybrid traction propulsion unit is offered, in which the positive aspects of previous models interfit.

Analysis of torque transmitting behavior and wheel slip prevention control during regenerative braking for high speed EMU trains

The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability, improving the adhesion utilization, and achieving deep energy recovery. There remain technical challenges mainly because of the nonlinear, uncertain, and varying features of wheel-rail contact conditions. This research analyzes the torque transmitting behavior during regenerative braking, and proposes a novel methodology to detect the wheel-rail adhesion stability. Then, applications to the wheel slip prevention during braking are investigated, and the optimal slip ratio control scheme is proposed, which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control. The proposed methodology achieves the optimal braking performance without the wheel-rail contact information. Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.