Roger M. Goodall

Control and monitoring for railway vehicle dynamics

Over the last twenty to thirty years, railway vehicle dynamics has changed from being an essentially mechanical engineering discipline to one that is increasingly starting to include sensors, electronics and computer processing. This paper surveys the application of these technologies to suspensions and running gear, focused upon the complementary issues of control (which has been reviewed within Vehicle System Dynamics previously) and monitoring (which has not previously been reviewed). The theory, concepts and implementation status are assessed in each case, from which the paper identifies the key trends and concludes with a forward look at what is likely to develop over the next years.

ACTIVE CONTROLS IN GROUND TRANSPORTATION--A REVIEW OF THE STATE-OF-THE-ART AND FUTURE POTENTIAL

SUMMARY Active control systems offer significant functional advantages over passive systems; their introduction into production-line vehicles, however, is cautious and slow. This survey describes the recent progress in the analysis, design and technology of active controls in vehicles. It includes the state-of-the-art of their introduction into operation as well as their future potential in view of recent advances in technology and computer aided design strategies. The survey has been limited to suspensions for vehicles on roads and tracks.

ACTIVE RAILWAY SUSPENSIONS: IMPLEMENTATION STATUS AND TECHNOLOGICAL TRENDS.

SUMMARY The paper provides a comprehensive survey of active railway suspensions, covering both basic concepts and significant practical implications around the world. A critical review of technological opportunities, both current and future, is included, and the final section takes a speculative look at long term trends.

Active suspension control of flexible-bodied railway vehicles using electro-hydraulic and electro-magnetic actuators

Abstract Lighter railway vehicles are going to become the norm in the future as the operator pushes towards a more economical operation. This paper looks into ways of applying classical control methods using “skyhook damping” to minimise the flexibility effects that arise as a consequence of having lighter vehicles, and in particular includes the effects of real actuator dynamics. Two and three actuators schemes are considered: two of them are located at the front and rear secondary suspension pivot points, with a third actuator at the centre of the vehicle primarily targeted at reducing the effects of the main bending mode of the vehicle body. Hydraulic actuators are used at the front and rear while an electro-magnetic actuator is connected to the centre of the vehicle.

Linear and non-linear skyhook damping control laws for active railway suspensions

Abstract This paper presents and compares different control strategies for applying “skyhook” damping control laws in active suspension systems for railway vehicles. It first examines a number of linear approaches for filtering the absolute velocity signal in order to optimise the trade-off between the random and deterministic track input requirements, and then what can be achieved using non-linear methods based upon Kalman-filters is explored. The principles that are developed are general and can be applied to both vertical and lateral secondary suspensions, although the paper concentrates upon the vertical direction and quantifies the performance achievable for a particular combination of track characteristics.

Monitoring Lateral Track Irregularity from In-Service Railway Vehicles

Abstract Maintaining the alignment of railway track is vitally important for the smooth and safe passage of railway vehicles. Poor track alignment can result in poor ride quality, flange contact, or even flange climb. Accurate horizontal track geometry can be measured using a dedicated track recording vehicle or from a full track geometry recording system mounted on an in-service vehicle. This paper describes the use of sensors mounted on the bogie of an in-service vehicle to estimate the mean track alignment without the use of optical or contact sensors. In principle, either bogie lateral acceleration or yaw rate can be processed to give an estimate of mean lateral track irregularity, but a yaw rate gyro provides consistent estimates down to lower vehicle speeds than does an accelerometer and does not require compensation for the effects of bogie roll. An improved estimate can be obtained by inverting the dynamic relationship between the mean track alignment and the bogie yaw motion. This is demonstrated with results from a Class 175 vehicle. Continually monitoring the lateral response of a bogie on an in-service vehicle, using only a yaw rate gyro, can provide data enabling the prioritization of maintenance operations.

Mechatronic developments for railway vehicles of the future

Abstract Railway vehicles have principally been designed by mechanical engineers since railways began in the early 1800s, i.e. before electronics and feedback control were invented. Today however they contain substantial amounts of electronic and computer control, in particular the traction systems, which have been converted entirely. However electronic control can also be applied to the vehicle suspension and guidance functions, which can provide large improvements in performance. More significantly, incorporation of sensors, controllers and actuators into the design process from the start can enable vehicle designers to take advantage of different mechanical configurations which are not possible with a purely mechanical approach—in other words the true spirit of mechatronics. The paper reviews the concepts, the current state-of-the-art and opportunities for mechatronic developments for railways for the future.

Passive suspensions incorporating inerters for railway vehicles

This paper investigates the possibility of improving the performance of railway vehicle suspensions by incorporating a newly developed mechanical device known as the inerter. A comparative study of several low-complexity passive suspension layouts is made. Improved performance for the lateral and vertical ride comfort, as well as lateral body movement when curving are demonstrated in comparison with the conventional suspension layout. The constraints imposed are to maintain the same level of other performance metrics. The calculations and optimisations are based on linearised plan-view and side-view high-speed train mathematical models.

RECENT DEVELOPMENT IN ACTIVE STEERING OF RAILWAY VEHICLES

Summary This paper presents the recent development on active steering for railway vehicles, and carries out a technical appraisal of different actuation schemes and control approaches. It brings together the latest research activities and findings for the full active steering techniques for rail vehicles with the solid-axle wheelsets, independently-rotating wheelsets and wheel-pairs without axles, but relevant work on passive and semi-active solutions is also briefly described. Potential benefits of the use of a combination of modern control technology and mechatronic approach are evaluated, and in particular solutions for the difficult design trade-off between the stability and the curving performance are presented. Various actuation configurations are discussed, and advantages and drawbacks of those schemes are investigated. The outline design using a number of control methods is analysed, and measurement requirement and state estimation techniques essential for implementation of the active steering schemes are also explored. In addition the issue of safety criticality is highlighted and a possible approach for developing fault-tolerant systems is proposed. Overall the paper provides an authoritative assessment of the major advances in actively-steered wheels and addresses outstanding critical issues.

Model-based condition monitoring at the wheel–rail interface

The dynamics of a rail vehicle is driven by the interaction between the wheel and rail. Any change to, for example, the shape of the wheel–rail profile or the contact adhesion conditions will change the response of the vehicle. The condition monitoring challenge is to interpret these changes into useful condition information. This paper presents the ongoing research into model-based condition monitoring at the wheel–rail interface applied to two applications: (i) wheel–rail profile estimation; and (ii) low adhesion detection. The wheel–rail profile estimation was carried out on a linearised simulation model that included a nonlinear conicity function. This function could be successfully estimated by also estimating the lateral track irregularities and giving the Kalman Filter self-updating information about the shape of the conicity function. The low adhesion detection was carried out on a complex nonlinear half vehicle model that included saturating contact force equations. The contact forces could be estimated by considering the half vehicle floating on a set of contact forces. Low adhesion conditions can be implied by the relative magnitudes of these contact forces.