Robust control for independently rotating wheelsets on a railway vehicle using practical sensors

This paper presents the development of H-infinity control strategy for the active steering of railway vehicles with independently rotating wheelsets. The primary objective of the active steering is to stabilize the wheelset and to provide a guidance control. Some fundamental problems for active steering are addressed in the study. The developed controller is able to maintain stability and good performance when parameter variations occur, in particular at the wheel-rail interface. The control is also robust against structured uncertainties that are not included in the model such as actuator dynamics. Furthermore the control design is formulated to use only practical sensors of inertial and speed measurements, as some basic measurements required for active steering such as wheel-rail lateral displacement cannot be easily and economically measured in practice

The benefits of mechatronically-guided railway vehicles: A multi-body physics simulation study

Mechatronically-guided railway vehicles are of paramount importance in addressing the increasing interest in reducing wheel-rail wear and improving guidance and steering. Conventional passively-guided rail vehicles are limited by the mechanical constraints of the suspension elements. Currently, a typical rail vehicle suspension needs to be sufficiently stiff to stabilize the wheelsets while being complaint enough to negotiate curved track profiles. The suspension is therefore a compromise for the contradictory requirements of curving and stability. In mechatronic vehicles, actuators are used with the conventional suspension components to provide additional stiffness or damping forces needed to optimise a vehicle for a wide variety of scenarios, and not rely on a sub optimal combination of passive components. This research demonstrates the benefits of active guidance and steering when compared to a conventional vehicle using simulation results from a multi-body simulation software Simpack. It also provides insights into the relative performance of the mechatronic schemes. The Simpack modeling allows for a complex model with high fidelity, which provides an additional level of proof of the control algorithms working on a real rail vehicle. Each vehicle is assessed in terms of guidance on straight track, steering on curved track, actuation requirements and wheel-rail wear. Significant benefits are demonstrated in one of the guided vehicles with independently-rotating wheelsets

Control of the Lateral Displacement Restoring Force of IRWs for Sharp Curved Driving

This paper presents a lateral displacement restoring force control for the independently rotating wheelsets (IRWs) of shallow-depth subway systems. In the case of the near surface transit, which has recently been introduced, sharp curved driving performance is required for the city center service. It is possible to decrease the curve radius and to improve the performance of the straight running with the individual torque control. Therefore, the individual torque control performance of the motor is the most important point of the near surface transit. This paper deals with a lateral displacement restoring force control for sharp curved driving. The validity and usefulness of the proposed control algorithm is verified by experimental results using a small-scale bogie system.This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT & Future Planning(No. 2013R1A1A1061048

Development of an intelligent sensing technique for active control of railway vehicles with independently rotating wheels

This thesis continues the development of an intelligent sensing scheme; using practical techniques for estimating the vehicle variables and economic measurements, which are mounted away from any arduous environments. The independently rotating wheelset design (IRW) de-couples the wheels; losing the mechanical feedback inherent with the conventional solid axle. The issue with the IRW, however, is that the natural curving characteristic is lost as a result, and therefore it is necessary to provide steering to the wheelset, to avoid flange contact and guide the wheelset, which can be supplied using a yaw constraint: passively or actively. As primary feedback variables aren’t readily available to measure, and are costly to provide, the Kalman filter has been used to provide full state optimal estimation of the dynamic system. Involving random perturbations to return the necessary states required, the Kalman filter allows the controller and actuator to apply active steering to the IRW. This thesis applies the Kalman-Bucy filter to a closed loop system with a mechatronic vehicle. A simple P controller is used to provide a torque to the actuators. The novelty about this work is that the sensors are mounted to the vehicle body, avoiding the extreme climactic conditions that a sensor would usually see if mounted to the axle. Re-formulating the Kalman filter to include curvature and cant within the state space and output matrices has been assessed to see if the curving performance will be maintained or improved. Altering the amount of sensors used has also been assessed, to see how the curving performance is affected. This can coincide with assessing whether the system will work, should one or more of the sensors fail

Rolling stock technology for the future

The paper presents a vision for future rolling stock with a timescale of 30-50 years to identify the key changes that are likely to be influential, in particular to meet the challenges associated with the UK’s ambitious technical strategy. Overall it suggests the authors’ vision for future rolling stock, not necessarily as a perfect prediction, but certainly to highlight the main possibilities

Control of railway wheelsets – A semi-active approach

This paper presents a detailed study of semi-active approach for railway wheelsets. A number of control strategies for active primary suspensions for both solid axle wheelset and independently rotating wheelsets are examined in detail and the key requirements of energy flows on both curved and straight tracks are investigated. A semi-active control scheme is then proposed for the independently rotating wheels and a comprehensive performance evaluation is provided to demonstrate that the proposed semi active control system can be used to continuously and reliably provide the necessary steering control without the need for the energy injection of full active control

Mechatronic guidance of rail vehicles through switches and crossings to enable vehicle-based switching

The research presented in this thesis demonstrates the theory that a mechatronic rail vehicle could be used on conventional switches and crossings (S\&Cs) to reduce wear. Railway track switches withstand high vertical and lateral forces leading to wear and damage. This necessitates a disproportionately high level of maintenance of over 10 \% of total maintenance costs, despite accounting for less than 0.1 \% of the network length. Mechatronically-guided rail vehicles are of paramount importance in addressing the increasing interest in reducing wheel-rail wear across the network and improving guidance and steering. Conventional passively-guided rail vehicles are limited by the mechanical constraints of the suspension elements. Currently, a typical rail vehicle suspension needs to be sufficiently stiff to stabilize the wheelsets while being complaint enough to negotiate curved track profiles. The suspension is therefore a compromise for the contradictory requirements of curving and stability. In mechatronic vehicles, actuators are used with the conventional suspension components to provide pseudo stiffness or damping forces needed to optimise a vehicle for a wide variety of scenarios, which can be positive or negative. This means that the vehicle is not reliant on a sub-optimal combination of passive components. Previous research in the area of mechatronic rail vehicles has shown the performance improvement in different straight or curved track profiles compared to a conventional vehicle. In this thesis, three vehicle configurations discussed previously in the literature, are evaluated on several different track profiles. These are the secondary yaw control (SYC), actuated solid-axle wheelset (ASW) and driven independently-rotating wheelsets (DIRW) steering mechanisms. The vehicle models are implemented in a multi-body simulation software Simpack to obtain high fidelity simulations that are comparable to a real rail vehicle. The DIRW vehicle showed the best performance in terms of reduced wear and minimal flange contact and was therefore chosen for studying its performance on a conventional S\&C. The DIRW vehicle was simulated on a C switch which is the most common on the UK mainline and on a high speed H switch. The results show that the DIRW vehicle gives a significant reduction in wear and reduces flange contact on the through and diverging routes of both S\&Cs. This proves the theory that active vehicles could be used to reduce impact forces at conventional S\&Cs. This could be an intermediate step towards a longer term vision of having a track switch without any moving parts where the switching is vehicle-based instead of track-based. Ultimately, if active elements on the vehicle could fully control the route while the track switch was completely passive i.e. had no moving parts, the reliability of the railways as a transport system would increase significantly. The technology could be combined with electronically-coupled vehicles which could form longer trains on busier routes and decouple to serve intermediary routes

Semi-active control for independently rotating wheelset in railway vehicles with MR dampers

This thesis presents details of an investigation of a controller for MR damper in the implementation of semi-active control, for primary suspensions of the independently rotating railway vehicles. This research focuses on using MR damper and it addresses on three main aspects when designing semi-active control systems for this application.One aspect is magnetorheological dampers categorised as a controllable fluid damper which can reversibly change from a flowing viscose fluid to semi-solid viscose fluid. The second aspect is the controllable yield strength can change in a millisecond by inducing an electric or magnetic field. Third aspect is MR damper is cheaper than actuators which are usually use in full active controllerThis research is a combination of a lookup table based on the inverse MR damper model to control the current input (to the MR damper) from required force and relative velocity of the device. The MR damper produces the desired force as precisely as possible. However, it is not possible to have precise knowledge of MR parameters and it is also difficult to account for the hysteresis present in MR dampers in the lookup table. Therefore, an additional local PI feedback controller is also used to improve the robustness for the MR control.As the main result, this study provides a comparison between semi-active controller with the use of MR damper and a full active controller system. The results show semi-active controller with the use of MR damper performed as good as full active controller. However semi-active control systems with MR dampers offer an overall efficiency and robustness when compared to the full active control system. Also, this system delivers comparable performance with the benefit of increased reliability and lower cost.In order to assess the developed system comprehensively, a two–axle vehicle model and a full bogie vehicle model are both evaluated individually in the study.The performance and robustness assessments of the developed semi-active controller with the full active control system are evaluated with the use of both two–axle vehicle model and the full bogie vehicle model with different operational track features such as curved track and straight track with lateral irregularities with various travel speeds.This study designed and developed a semi-active control systems with use of MR damper in primary suspension for independent rotation wheelsets in railway vehicles. Computer simulation results verified the suggested semi-active control is able to provide required stability and guidance control for independently- rotating wheelsets. Also, the result performed as well as full active control with the advantage of utilizing a lower cost device for semi-active control rather than an expensive actuator for full active control