Christopher P. Ward

Contact Force Estimation in the Railway Vehicle Wheel-Rail Interface

Abstract 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.

Adhesion estimation at the wheel–rail interface using advanced model-based filtering

The railway industry in the UK is currently expanding the use of condition monitoring of railway vehicles. These systems can be used to improve maintenance procedures or could potentially be used to monitor current vehicle running conditions without the use of cost prohibitive sensors. This paper looks at a novel method for the online detection of areas of low adhesion in the wheel/rail contact that cause significant disruption to the running of a network, particularly in the autumn season. The proposed method uses a Kalman–Bucy filter to estimate the creep forces in the wheel–rail contact area; post-processing is then applied to provide information indicative of the actual adhesion level. The algorithm uses data that, in practice, would be available from a set of modest cost inertial sensors mounted on the vehicle bogie and wheel-sets. The efficacy of the approach is demonstrated using simulation data from a nonlinear dynamic model of the vehicle and its track interface.

Real Time Detection of Low Adhesion in the Wheel/Rail Contact

Condition monitoring of railway vehicles has been highlighted by the railway industry as a key enabling technology for future system development. The primary uses for this could be the improvement of maintenance procedures and/or the identification of high-risk vehicle running conditions. Advanced processing of signals means these tasks could be accomplished without the use of cost prohibitive sensors. This paper presents a system for the on-board detection of low-adhesion conditions during the normal operation of a railway vehicle. Two different processing methods are introduced. The first method is a model-based approach that uses a Kalman–Bucy filter to estimate creep forces, with subsequent post processing for interpretation into adhesion levels. The second non model-based method targets the assessment of relationships between vehicle dynamic responses to observe any behavioural differences as a result of an adhesion-level change. Both methods are evaluated in specific case studies using a British Rail (BR) Mark 3 coach, inclusive of a BR BT-10 bogie, and a generic modern passenger vehicle based on a contemporary bogie design. These vehicles were chosen as typical application opportunities within the UK. The results are validated with data generated by the multi-body simulation software VAMPIRE® for realistic data inputs, representing a key scientific achievement.

Models for estimation of creep forces in the wheel/rail contact under varying adhesion levels

Areas of extremely low adhesion between the wheel and rail can cause critical problems in traction and braking that can manifest in issues such as signals being passed at danger. There is currently a lack of real-time information regarding the state and location of low-adhesion areas across rail networks. The study presented here examines the scientific challenges of understanding the change in vehicle running dynamics with variations in adhesion using the latest thinking of adhesion at micro-slip. This understanding supports the generation of suitable low-order dynamic models for use with a model-based estimator that infers adhesion levels in the wheel/rail contact using signals from modest-cost sensors that could be fitted to in-service vehicles. This paper presents verification of this technique by using simulated inertial measurement produced from a high-fidelity multibody simulation in a series of ‘blind’ tests.

Rethinking rail track switches for fault tolerance and enhanced performance

Railway track switches, commonly referred to as ‘turnouts’ or ‘points,’ are a necessary element of any rail network. However, they often prove to be performance-limiting elements of networks. A novel concept for rail track switching has been developed as part of a UK research project with substantial industrial input. The concept is currently at the demonstrator phase, with a scale (384 mm) gauge unit operational in a laboratory. Details of the novel arrangement and concept are provided herein. This concept is considered as an advance on the state of the art. This paper also presents the work that took place to develop the concept. Novel contributions include the establishment of a formal set of functional requirements for railway track switching solutions, and a demonstration that the current solutions do not fully meet these requirements. The novel design meets the set of functional requirements for track switching solutions, in addition to offering several features that the current designs are unable to offer, in particular to enable multi-channel actuation and rail locking, and provide a degree of fault tolerance. This paper describes the design and operation of this switching concept, from requirements capture and solution generation through to the construction of the laboratory demonstrator. The novel concept is contrasted with the design and operation of the ‘traditional’ switch design. Conclusions to the work show that the novel concept meets all the functional requirements whilst exceeding the capabilities of the existing designs in most non-functional requirement areas.

Modelling and building of experimental rig for high redundancy actuator

The high redundancy actuator (HRA) concept is a novel approach to fault tolerant actuation. It refers to an actuator that consists of relatively large number of actuation elements, connected both in series and parallel to form a single actuator. This configuration improves the reliability and availability of the actuator and thus provides a high degree of fault tolerance. The HRA also reduces the need for over-sizing an actuator especially in safety-critical applications such as aerospace. HRA is suitable to a wide range of actuation technology but this paper focuses on a linear electromechanical actuator (EMA) due to its extensive application not only in industrial machinery but in aircraft and the aerospace industry in general. This paper presents ongoing and future work to demonstrate the concept of a fault tolerant system high redundancy actuator through a 3-by-4 series-in-parallel linear electromechanical actuator.

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.

Benefits of mechatronically guided vehicles on railway track switches

Conventional rail vehicles struggle to optimally satisfy the different suspension requirements for various track profiles, such as on a straight track with stochastic irregularities, curved track or switches and crossings, whereas mechatronically guided railway vehicles promise a large advantage over conventional vehicles in terms of reduced wheel–rail wear, improved guidance and opening new possibilities in vehicle architecture. Previous research in this area has looked into guidance and steering using multi-body simulation models of mechatronic rail vehicles of three different mechanical configurations – secondary yaw control, actuated solid-axle wheelset and driven independently rotating wheelsets (DIRW). The DIRW vehicle showed the best performance in terms of reduced wear and minimal flange contact and is therefore chosen in this paper for studying the behaviour of mechatronically guided rail vehicles on conventional switches and crossings. In the work presented here, a mechatronic vehicle with the DIRW configuration is run on moderate and high-speed track switches. The longer term motivation is to perform the switching function from on-board the vehicle as opposed to from the track as is done conventionally. As a first step towards this, the mechatronic vehicle model is compared against a conventional rail vehicle model on two track scenarios – a moderate speed C type switch and a high-speed H switch. A multi-body simulation software is used to produce a high fidelity model of an active rail vehicle with independently rotating wheelsets where each wheel has an integrated ‘wheelmotor’. This work demonstrates the theory that mechatronic rail vehicles could be used on conventional switches and crossings. The results show that the mechatronic vehicle gives a significant reduction in wear, reduced flange contact and improved ride quality on the through routes of both moderate and high-speed switches. On the diverging routes, the controller can be tuned to achieve minimal flange contact and improved ride quality at the expense of higher creep forces and wear.

Simulation of a Condition Monitoring Scheme for a Neutral Beam Injector Cryogenic Pump

Abstract This paper presents the simulation testing of a model-based condition monitoring scheme for the Joint European Torus neutral beam cryogenic pumping system. The scheme was tested by examining its response to a range of realistic simulated faults. Ten faults were tested. The scheme detected each of the faults and uniquely identified six of them. The scheme was shown to have an improved performance compared to the current manual detection method.

Detection of low adhesion in the railway vehicle wheel/rail interface: assessment of multi-bodied simulation data

Low adhesion in the wheel/rail interface of railway vehicles creates safety and punctuality issues in terms of missed station stops and signals passed at danger. RSSB project T959 is tasked with developing advanced monitoring techniques for the detection of adhesion in this key interface. A number of techniques were developed and initially tested on simplified models of a rail vehicle. The efficacy of these techniques is now being tested with more representative data produced by multi-bodied physics simulation package Vampire. This paper therefore covers the outcomes of the Vampire testing, initial application of a Kalman-Bucy filter creep force estimator to the Vampire data, and application of a data comparison method based upon the Sprague and Geers method, also to the Vampire data.