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

Active control of railway bogies – assessment of control strategies

A number of configurations for active control of railway vehicle bogies are assessed in a consistent framework to provide an effective comparison, using a typical modern bogie as a baseline. For each configuration appropriate control strategies are identified and their relative performances are assessed in terms of straight track stability, curving performance and control requirements

Block-control methods for low-order automotive control

Robust linear and nonlinear control is a continuing requirement for automotive powertrain controls. Newton iteration techniques have been proposed for both nonparametric linear and recently nonlinear control. Such nonparametric methods may eventually allow benefits of both low-order controllers and more rapid calibration time. This paper evaluates the feasibility of such Newton iteration techniques by an experimental comparison of a standard Riccati method a Riccati J-spectral factorisation and a novel l2 algebraic J-spectral factorisation using Newton iteration techniques in a SI engine idle controller. The methods are each applied in a 2- block H∞formulation. The results of experimentally implementing robust idle speed controllers show broadly similar outcomes for all the methods compared and thus indicate the potential of the Newton iteration methods for further development in more advanced nonparametric, low-order and nonlinear control

Wheel-rail profile condition monitoring

Increased railway patronage worldwide is putting pressure on rolling stock and infrastructure to operate at higher capacity and with improved punctuality. Condition monitoring is seen as a contributing factor in enabling this and is highlighted here in the context of rolling stock being procured with high capacity data buses, multiple sensors and centralised control. This therefore leaves scope for advanced computational diagnostic concepts. The rail vehicle bogie and associated wheelsets are one of the largest and most costly areas of maintenance on rolling stock and presented here is a potential method for real time estimation of wheel-rail contact wear to move this currently scheduled based assessment to condition based assessment. This technique utilises recursive ‘grey box’ least squares system identification, used in a piecewise linear manner, to capture the strongly discontinuous nonlinear nature of the wheel-rail geometry

Contact force estimation in the railway vehicle wheel-rail interface

Increased patronage of railways in the UK in the past 20 years has put demands on rolling stock to operate at peak availability with reduced time available for maintenance. One possible tool to enable this is the use of real time fault detection and diagnosis on board railway vehicles to detect faulty components and provide information about the current running condition of the system. This paper discusses the development of one such technique for the estimation of creep forces of the wheel-rail contact. Real time knowledge of which could be used to predict wear of the wheel tread and rail head, predict the formation of rolling contact fatigue, and identify any areas of low adhesion present on the network. The paper covers development of a full vehicle nonlinear contact mechanics model, development of the Kalman-Bucy filter estimation technique and how the technique will be developed and validated in the future

Active fault tolerant control applied to REPOINT, a novel railway track switch

Railway networks are fitted with switches and crossings that enable trains to move from one track to another however they present a single point of failure. Existing track switches actuation is performed in the open loop presenting a research gap where closed-loop fault tolerant control can be applied to track switch actuation in order to improve railway network performance. A new railway track switch, REPOINT has been developed at Loughborough University with a new electromechanical design that incorporates actuator redundancy to improve the reliability of track switch operation. This paper looks at the development and validation of a sensor fault detection, identfication and accomodation scheme applied to a detailed non-linear model representing the laboratory scale demonstrator of the REPOINT concept. A residual-based fault diagnosis scheme is developed from the comparison of estimates generated by a bank of observers and output measurements. In the presence of sensor faults, a reconstructed signal from the fault detection algorithm is used to replace the measured signal for feedback control and thus safe switching position control is achieved. The results demonstrate that using a reliable fault tolerant control configuration could increase the availability and reliability of the REPOINT track switch

Condition monitoring of rail vehicle bogies

This paper details a range of work carried out by the authors within the general theme of advanced condition monitoring possibilities for rail vehicle bogies. Maintenance of rail vehicle bogies represents one of the largest areas of whole vehicle running costs and their efficient operation is of safety critical importance to the entire rail system. Currently the majority of maintenance is carried out on a scheduled basis which can be time consuming, costly and potentially not effective at fault detection. This paper reviews concepts that could allow real time detection of the condition of the bogie so as to reduce vehicle out of service time and improve safe operation. Concepts reviewed are: the use of condition monitoring for detection of suspension component condition; detection of low adhesion conditions; and assessment of the wheel-rail interface condition

Improving the reliability and availability of railway track switching by analysing historical failure data and introducing functionally redundant subsystems

Track switches are safety critical assets that not only provide flexibility to rail networks but also present single points of failure. Switch failures within dense-traffic passenger rail systems cause a disproportionate level of delay. Subsystem redundancy is one of a number of approaches, which can be used to ensure an appropriate safety integrity and/or operational reliability level, successfully adopted by, for example, the aeronautical and nuclear industries. This paper models the adoption of a functional redundancy approach to the functional subsystems of traditional railway track switching arrangements in order to evaluate the potential increase in the reliability and availability of switches. The paper makes three main contributions. First, 2P-Weibull failure distributions for each functional subsystem of each common category of points operating equipment are established using a timeline and iterative maximum likelihood estimation approach, based on almost 40,000 sampled failure events over 74,800 years of continuous operation. Second, these results are used as baselines in a reliability block diagram approach to model engineering fault tolerance, through subsystem redundancy, into existing switching systems. Third, the reliability block diagrams are used with a Monte-Carlo simulation approach in order to model the availability of redundantly engineered track switches over expected asset lifetimes. Results show a significant improvement in the reliability and availability of switches; unscheduled downtime reduces by an order of magnitude across all powered switch types, whilst significant increases in the whole-system reliability are demonstrated. Hence, switch designs utilising a functional redundancy approach are well worth further investigation. However, it is also established that as equipment failures are engineered out, switch reliability/availability can be seen to plateau as the dominant contributor to unreliability becomes human error

A model of a repoint track switch for control

Track switching provides necessary flexibility to a rail network, allowing vehicles to change routes when necessary. Track switches, however, have historically been prone to failure. To increase asset reliability, a concept for a novel design of switch has been developed which allows multi-channel actuation through a novel actuation and locking mechanism, under a project titled 'Repoint'. This paper describes a mathematical model of the operation a novel Repoint track switch. The model was derived from a first principles physical analysis of the Repoint concept design. The structure of the model mimics the physical structure of the design. Each physical component has an individual sub-model. The model has been used to estimate the actuator drive requirements for a case study mainline switch installation. It has been found that a Repoint track switch could be run from an existing UK signalling power supply. It is anticipated that this model will be used as the basis for a control system design activity for a technology demonstrator installation currently under construction

Railway bogie stability control from secondary yaw actuators

The idea of active control based upon applying a controllable yaw torque between the body and the two bogies has been studied previously, mainly to try and provide enhanced curving capability. This paper extends the idea by examining the opportunities for using secondary yaw actuators to stabilise a bogie having very soft yaw stiffness between the bogie frame and the wheelsets, the objective being to take advantage of the good curving performance offered by the soft primary yaw stiffness