Independently Rotating Wheels Research Articles

Multiagent Reinforcement Learning for Active Guidance Control of Railway Vehicles with Independently Rotating Wheels

This paper presents a novel data-driven multiagent reinforcement learning (MARL) controller for enhancing the running stability of independently rotating wheels (IRW) and reducing wheel–rail wear. We base our active guidance controller on the multiagent deep deterministic policy gradient (MADDPG) algorithm. In this framework, each IRW controller is treated as an independent agent, facilitating localized control of individual wheelsets and reducing the complexity of the required observations. Furthermore, we enhance the MADDPG algorithm with prioritized experience replay (PER), resulting in the PER-MADDPG algorithm, which optimizes training convergence and stability by prioritizing informative experience samples. In this paper, we compare the PER-MADDPG algorithm against existing controllers, demonstrating the superior simulation performance of the proposed algorithm, particularly in terms of self-centering capability and curve-negotiation behavior, effectively reducing the wear number. We also develop a scaled IRW vehicle for active guidance experiments. The experimental results validate the enhanced running performance of IRW vehicles using our proposed controller.

Semi-active control of independently rotating wheels in railway vehicles

ABSTRACT This paper presents an in-depth analysis of steering and guidance problems of independently rotating wheels (IRWs) in railway vehicles and provides an engineering insight into the possibilities for passive and/or semi-active control possibilities that do not require expensive full-active systems. The theoretical development is then supported in the study by carrying out a comprehensive performance evaluation in comparison with a full active control. The study demonstrates that the independently rotating wheelset may be effectively controlled via semi-active approaches to provide the wheelsets with the necessary steering on curves and self-centring ability on a straight track with irregularities with performance comparable with full active systems.

Robust LPV-H∞ control for active steering of tram with independently rotating wheels

A new methodology is proposed in this study for active steering of a tram with independently rotating wheels (IRWs). This methodology has been developed specifically to improve the tram’s steering capability and to reduce wheel-rail wear. The tram is represented by a complex dynamic model with a diverse range of operating conditions, and traditional active steering methods cannot ensure that the tram can remain well-controlled throughout the entire range of operating conditions. The linear parameter-varying (LPV)- H∞ control method proposed in this paper uses variable parameter theory to represent the nonlinearity, the parameter uncertainty, and the external force changes in the IRW. The LPV- H∞ steering controller can not only ensure the robustness of the uncertain system, but also can balance the complexity and the performance of the controller. This allows the tram to offer good steering performance under various running conditions. The simulation results presented in this research show that application of the proposed control method improves the running performance of the tram and reduces the wheel-rail wear significantly on both straight and curved tracks when compared with the passive case.

POSSIBILITIES OF IMPROVING A RAIL VEHICLE RUNNING SAFETY WITH INDEPENDENTLY ROTATING WHEELS

This work is focused on the possible ways of improving the running safety of a railway vehicle, which uses IRWs (independently rotating wheels) in a bogie. It discusses the main positive and negative properties of an application of IRWs for a railway vehicle while it is running in a curve. There are evaluated running properties of a railway vehicle in terms of safety for IRWs and a standard wheelset (SW). It is assumed that a wheelset design with IRWs will reduce the risk of derailment of a railway vehicle in a curve with a smaller radius because it will be reached a more favourable distribution of decisive forces in the wheel/rail contact. A designed wheelset with IRWs differs from other IRWs designs; in this case, only a flange can rotate independently from a wheel treat surface about the axis of rotation. Further, this research presents an analysis of a friction forces distribution of the friction forces in a contact of a flange and a rail head and a comparison with an SW. The obtained results allow concluding that it is advisable to use the wheels with the perspective wheel design (including independently rotating) to reduce the resistance to movement and improve the running properties of a railway vehicle for safety.

Electric Drive Solution for Low-Floor City Transport Trams

The urban transport system based on trams as the basic means of transport is one of the oldest systems of human transport in urban agglomerations. A tram is a more efficient, cheaper-to-operate, and greener means of transport compared to a bus. Striving to enable the use of this means of transport by elderly and disabled people, constructors and manufacturers of tram vehicles began to consider the requirements of the ordering parties—organizers of municipal public transport—in their solutions. The basic condition for disabled and elderly people to use tram transport is the possibility of safe and efficient entry and exit from the vehicle at tram stops. The fulfillment of this condition is possible only in the case of tram vehicles with a low 100% floor, and this, in turn, requires the replacement of trolleys with traditional wheelsets, that is, trolleys with independently rotating wheels, in the construction of the running gear. A wheelset with independently rotating wheels (IRW) does not have self-centering properties, and, thus, problems may arise with excessive wear of wheel and rail profiles and with continuous contact of the wheel flange with the rail, which may, consequently, lead to derailment. Driving a vehicle on the track in this case is governed by different laws. To prevent such phenomena, it is required to use the wheel drive control system, which allows for the stabilization of the vehicle movement on the track. Both the introduction of independently rotating wheels in the construction of the bogie and the drive connected to the wheel control system requires research and analysis to confirm the correctness of the assumptions made. The innovative solution of the control system in the case of a tram vehicle was patented and then the patent was implemented to produce a low-floor tram with 100% low floor by a Polish tram manufacturer. This article presents the results of the work carried out on the adoption of the concept of a running gear and drive solution for a low-floor tram vehicle with independently rotating wheels and the results of simulation analysis of the drive control of such a system, using mathematical models of the mechanical system (running gear) and the electrical system (motor drive control system).

Estimating the wheel lateral position of a mechatronic railway running gear with nonlinear wheel–rail geometry

The “Next Generation Train” (NGT) is a double-deck high speed train concept in light-weight design that has been established as a technical and project framework in which the German Aerospace Center gathers its long-term railway vehicle research. To reduce wheel and rail wear and to enhance the passenger capacity, a mechatronic running gear with independently rotating wheels (IRW) is a key vehicle component under research. This running gear requires an advanced control of the lateral dynamics in order to fully exploit its potential in minimizing wear and noise, but this relies on information on its lateral position relative to the track. In daily railway operation it is difficult to directly measure this displacement of the wheel-pair. However, according to previous work it is possible to design an appropriate observer to estimate the lateral position, but its estimation accuracy highly depends on the chosen sensor configuration. Nevertheless, it was shown that the lateral dynamics of the running were not completely reproduced by the system description especially at suddenly changing directions in the movement of the IRW. In this work the system description is complemented by a nonlinear description of the wheel–rail geometry. Therefore, an observability analysis and an observer synthesis to estimate the lateral position for the nonlinear system of the 1:5 scaled hardware running gear is carried out. For validation purposes an extended Kalman filter with the U-D formalism is implemented at the real-time environment of the testbed and the estimation accuracy of the observer configurations is compared.

Modeling and simulation of a control system of wheels of wheelset

Modern light rail vehicles, such as a tram or rail bus, due to the need to provide mobility for the elderly or disabled people and the requirements of operators operating passenger rail transport or transport in urban areas must have a 100% low floor. Structurally, this is associated with the use of wheelset with independently rotating wheels (IRW) in such vehicles. It is also possible to use a bogie structure without the use of a wheelset axle by mounting the wheels directly in the side parts of the bogie frame. This construction is more complex and will not be discussed in this article. Bearing in mind the dynamic behavior of such vehicles during operation (lateral stability, profile wear) in various driving conditions (curve traffic, crossovers) and taking into account operating costs, it becomes necessary to install wheel rotation control systems to maintain center movement mass of the wheelset around the centerline of the track. The subject of the article will be considerations on modeling and simulation of rail vehicle bogie motion with IRW sets including the wheel control system. Nominal and mathematical models of the analyzed vehicle will be presented, as well as a controlled strategy based on the comparison of the angular velocities of the wheels of the wheelset A review of works on solutions of such systems will be presented, and a control concept will be proposed. The summary contains conclusions regarding the possibility of practical use of the proposed method of steering wheels of a wheelset in the c ase of independently rotating wheels.

Active control of independently-rotating wheels with gyroscopes and tachometers – simple solutions for perfect curving and high stability performance

Although a passive independently-rotating wheel-pair (IRW) is not well suited for curve negotiation due to an inability to provide the necessary steering, an active IRW system offers the potential to realise perfect curving with a satisfactory running stability. Simple control solutions to realise automatic steering and stability of the IRW system are proposed in this paper. In this control approach, only gyroscopes and tachometers are adopted for the measurements. Associated with a prototype of a two-axle IRW vehicle, the active control strategies for both motor-driven and actuator-driven solutions are illustrated. The simulation results demonstrate significant alleviations in the wheel/rail interactions with perfect-curving performances and superior running stabilities owing to the proposed control strategies.

Hardware-in-the-Loop Simulation for Active Control of Tramcars With Independently Rotating Wheels

The wheelset is an important part that affects the dynamics of railway vehicles. The main purpose of the wheelset is to solve the problem of stability, curve performance, comfort, and wear. A conventional railway vehicle adopts rigid-axle wheelset (RW) due to the self-centering mechanism. On the other hand, independently rotating wheels (IRWs) have not been widely applied in the railway industry, since they do not generate any self-centering mechanism. It creates excessive wear, and derailment may occur. However, the IRWs have excellent curving performance compared with the RWs, and it enables realizing a low-floor structure that is convenient for passengers to get on and off. The recent active control technology has made it possible to generate a centering force in the IRWs. There are still many obstacles for the practical use of this technology, and it is necessary to verify the control strategies through various test methods. In this paper, an analytical model is derived, and an active control strategy is studied. To verify the validity of the active control strategy, a novel hardware-in-the-loop simulation (HILS) configuration using a real-time model and a motor-generator set are proposed.

Observer design for a railway running gear with independently rotating wheels

The German Aerospace Center bundles its railway research in the long-term project “Next Generation Train” (NGT). The NGT is a high speed train concept in light-weight design and double-deck configuration. To reduce wheel and rail wear and to enhance the passenger capacity, a mechatronic running gear with independently rotating wheels (IRW) is designed. This configuration requires an advanced control of the lateral dynamics in order to fully exploit the potential in minimizing wear and noise. In terms of a model-based control design, the controller performance highly depends on the estimated lateral position of the running gear relative to the track. In a practical environment it is difficult to directly measure this displacement of the wheel-pair. Therefore this article deals with the question which sensor configuration enables an appropriate estimation of the lateral displacement and is suitable for observer design. Hence, an observability analysis and an observer synthesis to estimate the lateral position for the nonlinear system of the 1:5 scaled hardware running gear is carried out. For validation purposes three estimators are implemented at the real-time environment of the testbed and the estimation errors of the observer configurations are compared.

Dynamics of a running gear with IRWs on curved tracks for a robust control development

AbstractAs a major task of the DLR‐internal project “Next Generation Train”, robust state feedback control with gain scheduling was sucessfully applied to guide the experimental running gear with independently rotating wheels (IRWs) at a 1:5 scaled roller rig, see [1]. However, the adaptation of the control structure to the 1:1 multibody model requires to additionally consider the properties of curved tracks. For that reason, an analytical model of a running gear with IRWs is deduced using Euler‐Lagrange‐equations and taking superelevation and track curvature into account. Furthermore, the complexity of the system is reduced to allow for a robust feedback control synthesis and feed‐forward control including model inversion. Finally, the model is discussed and a first approach for a feed‐forward control in transition curves is shown. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A study on the optimum design of high-speed low-floor bogie with independently rotating wheels

The low-floor bogie is a prior technology in countries and companies that want to develop the tram. The Low-floor tram (LFT), which includes low-floor bogies, is easy to embark and disembark because of the low floor height. In addition, it can be driven on urban as well as rural tracks. Furthermore, emissions such as NOx and SOx can be reduced. Due to these advantages, this innovative technology is expected to change the public transport system. To improve utilization in a downtown area, the technology for the low-floor bogie should satisfy conditions of a high-speed of over 80 km/h and minimum radius within a 25 mR curve for smooth running on a track that has a severe turning radius. Moreover, the wheelset should not be located in the bogie, and the components inside the bogie need to be wellarranged to satisfy the full low-floor condition. In this study, to develop an over-80 km/h class high-speed low-floor bogie that can be driven safely on a 25 mR curved track, a conceptual design of the LFT multibody dynamics model was constructed and dynamic characteristics were assessed by dynamic analysis. The modeling modification with Independently rotating wheels (IRW) needed to steer actively through semi-active suspension and the optimization using Design of experiments (DOE) were then performed. Through DOE method, the optimum combination of design parameters could be obtained and, the driving performances such as ride stability, comfort and safety of the LFT could then be improved about 7 %. The results of this work are available to detail design and development of LFT.

Dynamic of Friction Coupling Independently Rotating Wheels for High Speed

A new lateral coupling structure with independently rotating wheels (IRW) is proposed, and longitudinal creepage is obtained by replacing the gear pair with the friction pair to synchronize the rotation speed of left and right wheels. The auxiliary wheelset made up of two friction wheels can be placed either under the primary suspension or on the frame. Vehicles dynamics models with three different kinds of bogies are developed, including friction coupling bogie with independently rotating wheels (FCIRW-bogie), bogie with independently rotating wheels (IRW-bogie), and bogie with rigid wheelsets, and their guiding and resetting capability when negotiating large-radius curves are compared and analyzed. Results show that FCIRW has the advantages of both IRW and rigid wheelset. On the straight track, FCIRW has sufficient wheel-rail longitudinal creep force to assist the reset; its critical speed is much higher than that of the rigid wheelset. On the curved track, the whole vehicle wear power of FCIRW-bogie vehicle is about 2/3 of the rigid axle level.

Integrated active control of independently rotating wheels on rail vehicles via observers

As the well-known difficulties are that feedback signals are not easy and economical measurement in practice for active control, this paper presents a study of state estimation for active control of independently rotating wheels (IRW) based on observers. The reduced-order observer and high-order sliding mode observer are used to provide reliable and accurate estimations of the wheel pair state and track curvature using practical sensors. This proposed method uses less sensors than the one of previous studies. Furthermore, lateral accelerator and yaw velocity sensors (gyros) are economical and available for active steering and stability control system to obtain the required feedback signals. The wheels’ relative rotational speed, track curvature and yaw angle of wheelsets are the feedback signals for IRW active control approach. Computer simulations are used to verify the effectiveness of proposed methods and assess control performance in stability and negotiation.

Design of the wheel profile of an independently rotating wheel with inverse tread conicity by considering the trajectory of the center of gravity

The self-alignment of independently rotating wheels (IRWs) with inverse tread conicity cannot be realized simply by using a nonlinear concave wheel profile. A novel wheel profile design method is proposed to solve this problem that is based on the static guidance characteristic of a single isolated wheelset. The procedure is based on a desired lateral geometric force function with respect to the lateral displacement of IRWs with inverse tread conicity. The method focuses on the trajectory of the center of gravity under the wheel/rail contact constraint. A numerical process description and design example are provided and the resulting design is checked using forward contact analysis and the multi-body dynamics analysis software SIMPACK. A lateral restoring force that is proportional to the lateral displacement can be obtained using the proposed design method for the wheel profile.

Analysis of steering performance of differential coupling wheelset

In order to improve the curving performance of the conventional wheelset in sharp curves and resolve the steering ability problem of the independently rotating wheel in large radius curves and tangent lines, a differential coupling wheelset (DCW) was developed in this work. The DCW was composed of two independently rotating wheels (IRWs) coupled by a clutch-type limited slip differential. The differential contains a static pre-stress clutch, which could lock both sides of IRWs of the DCW to ensure a good steering performance in curves with large radius and tangent track. In contrast, the clutch could unlock the two IRWs of the DCW in a sharp curve to endue it with the characteristic of an IRW, so that the vehicles can go through the tight curve smoothly. To study the dynamic performance of the DCW, a multi-body dynamic model of single bogie with DCWs was established. The self-centering capability, hunting stability, and self-steering performance on a curved track were analyzed and then compared with those of the conventional wheelset and IRW. Finally, the effect of coupling parameters of the DCW on the dynamic performance was investigated.

Electronic differential for tramcar bogies: system development and performance evaluation by means of numerical simulation

The dynamic behaviour of railway vehicles depends on the wheelset configuration, i.e. solid axle wheelset or independently rotating wheels (IRWs). The self-centring behaviour, peculiar of the solid axle wheelset, makes this kind of wheelset very suitable for tangent track running at low speed: the absence of the self-centring mechanism in the IRWs may lead to anomalous wheel/rail wear, reduced vehicle safety and passengers’ discomfort. On the contrary, during negotiation of the sharp curves typical of urban tramways, solid axle wheelsets produce lateral contact forces higher than those of IRWs. This paper illustrates an electronic differential system to be applied to tramcar bogies equipped with wheel-hub motors which allows switching from solid axle in tangent track to IRWs in sharp curve (and vice versa). An electro-mechanical vehicle model is adopted for the design of the control system and for the evaluation of the vehicle dynamic performances.

21413 曲線通過性能と走行安定性の両立のための傾斜軸独立回転輪軸の提案

In the design of railway bogies, the compatibility between curving performance and running stability is important. Especially, there are a lot of tight curved sections in LRTs. Bogie with independently rotating wheels (IRW) could be useful to realize both curving performance and running stability. For example, EEF bogie and IRW with inverse tread conicity have been proposed. In this paper, a new-type IRW with oblique axle is proposed and the equation of motion is derived. Characteristics of hunting motion are investigated with the eigenvalue analysis. Furthermore, full vehicle model simulation with the new-type IRWs is conducted to evaluate curving performance of the proposed IRW.

605 数値解析による新型独立回転輪軸の走行性能検証(OS6 オーガナイズドセッション《振動・音響・制御》)

In the design of railway bogies, the compatibility between curving performance and running stability is important. Especially, there are a lot of tight curved sections in LRTs. Bogie with independently rotating wheels (IRW) could be useful to realize both curving performance and running stability. For example, EEF bogie and IRW with inverse tread conicity have been proposed. In this paper, a new-type IRW with oblique axle is proposed and the equation of motion is derived. Characteristics of hunting motion are investigated with the eigenvalue analysis. Furthermore, full vehicle model simulation with the new-type IRWs is conducted to evaluate curving performance of the proposed IRW.

Development of a new analytical model for a railway vehicle equipped with independently rotating wheels

The urban tram introduced recently has a low-floor structure for the convenience of passengers getting on and off. To adjust the low-floor level and improve performance on curves, most low-floor trams have IRWs (independently rotating wheels) with no central axle between the two wheels. Eliminating the central axle, however, creates several inherent problems, such as insufficient guiding force and excessive wear. To analyze these problems, a new analytical model is described in this paper to describe the dynamic characteristics of IRWs more precisely. This analytical model is developed to consider the effects of longitudinal creep in particular, which have been ignored in conventional analytical models of IRWs. In addition, a running stability analysis based on the newly developed analytical model is conducted to compare the critical speeds of IRW-axle vehicles and rigid-axle vehicles. The dynamic characteristics of an initial disturbance are compared to verify that the analytical model is effective in expressing the dynamic characteristics of IRWs.