Generalised Design Models For EMS Maglev

The paper presents a generic modelling approach for electro-magnetic suspension (EMS) systems which brings together both fundamental principles and specific design factors to provide generalised models that can be adapted for any application. Key system parameters and typical electro-magnetic design factors are used to produce practical models for EMS controller design

Maglev: an unfulfilled dream?

Although Maglev has been technically developed in a variety of forms, and has had some limited operational success, the dream envisaged in the 1960s and 1970s of wide-scale commercial implementation remains elusive. This paper provides a technical and historical appraisal, starting with the expected features believed in the early days to characterise Maglev, and reviews the actual achievements against these expectations, i.e. to assess the progress towards the original dream and its viability. The conclusion includes a commentary on the present day opportunities and barriers, and offers some suggestions for emphasis into the future. The objective is to stimulate a discussion aimed at helping to understand why the dream remains largely unfulfilled

New insights from fractional order skyhook damping control for railway vehicles

Active suspensions for railway vehicles have been a topic of research for a number of decades and while their applications in service operation are limited it seems clear that they will in due course see widespread adoption. Railway suspension design is a problem of compromise on the non-trivial trade-off of ride quality vs track following (guidance), and the skyhook damping control approach has been paramount in illustrating the potential benefits. Since skyhook damping control, various advanced control studies appeared contributing to redefine the boundaries of the aforementioned trade-off. Yet there is no study on the impact of fractional order methods in the context of skyhook railway active suspensions, and in particular related to skyhook damping control. This is the area to which this paper strongly contributes. We present findings from a current project on fractional order controllers for railway vehicles active suspensions, in particular work on the effect of fractional order methods in basic skyhook damping control schemes, i.e. pure and intuitively-based skyhook. Firstly we present a brief review of conventional skyhook damping control and then proceed to a rigorous investigation of the impact of fractional order on the ride quality / track following trade-off. The relevant benefits from fractional order methods are appraised and new insights highlighted

Combining active structural damping and active suspension control in flexible bodied railway vehicles

There is a desire to design lightweight railway vehicle bodies for future high speed trains. Previously, suppression of structural vibration of the flexible lightweight vehicle body was attempted via use of active suspensions (conventional actuators) or by structural damping via piezoelectric actuators, with the aim being to improve the ride quality. In a railway vehicle the typical active suspension setup comprises front and rear suspension conventional actuators, while adding more macro-actuator elements to minimise structural vibrations can substantially impact vehicle weight and location considerations. In this paper, we show that piezoelectric actuator control can provide complementary action to active suspensions. Decentralized control is adopted for combined active structural damping and active suspension design via Linear Quadratic Gaussian (LQG) method and modal control with skyhook damping respectively. The side-view model of a flexible-bodied railway vehicle integrated with piezoelectric actuators and appropriate sensor outputs is derived and the placement of the piezoelectric actuators and sensors is addressed via structural norms. It is shown that vibrations of both the flexible modes and rigid modes are suppressed effectively. This suggests that with the combined approach, control by both piezoelectric actuators and suspension actuators could be used in a more efficient way to address vibrations in light railway vehicle bodies

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

Operational reliability calculations for critical systems

Reliability theory deals with the effect of mean time to repair upon overall system failure rates, but for critical systems such calculations are not what is required because an important performance criterion relates to operational failures, which are fundamentally different to unsafe failures: essentially they are the result of the system-level response to avoid unsafe failures. This paper introduces the particular problem for critical systems in general, presents an analysis of some of the relevant conditions and provides some simulation results in the context of a railway active suspension application that illustrate the overall effects and trends

Reliability of 2-out-of-N:G systems with NHPP failure flows and fixed repair times

It is commonplace to replicate critical components in order to increase system lifetimes and reduce failure rates. The case of a general N-plexed system, whose failures are modeled as N identical, independent nonhomogeneous Poisson process (NHPP) flows, each with rocof (rate of occurrence of failure) equal to λ(t), is considered here. Such situations may arise if either there is a time-dependent factor accelerating failures or if minimal repair maintenance is appropriate. We further assume that system logic for the redundant block is 2-out-of-N:G. Reliability measures are obtained as functions of τ which represents a fixed time after which Maintenance Teams must have replaced any failed component. Such measures are determined for small λ(t)τ, which is the parameter range of most interest. The triplex version, which often occurs in practice, is treated in some detail where the system reliability is determined from the solution of a first order differential-delay equation (DDE). This is solved exactly in the case of constant λ(t), but must be solved numerically in general. A general means of numerical solution for the triplex system is given, and an example case is solved for a rocof resembling a bathtub curve

Hydraulic actuation technology for full- and semi-active railway suspensions

The paper describes a simulation study that provides a comprehensive comparison between full-active and semi-active suspensions for improving the vertical ride quality of railway vehicles. It includes an assessment of the ride quality benefits that can theoretically be achieved with idealised devices, and also examines the impact of real devices based upon hydraulic actuation technology

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