Running Dynamics of Rail Vehicles

The investigation of rail vehicle running dynamics plays an important role in the more than 200 year development of railway vehicles and infrastructure. Currently, there are a number of new requirements for rail transport associated with the reduced environmental impact, energy consumption and wear, whilst increasing train speed and passenger comfort. Therefore, the running dynamics of rail vehicles is still a research topic that requires improved simulation tools and experimental procedures. The book focuses on the current research topics in railway vehicles running dynamics. Special attention is given to high-speed railway transport, acoustic and vibrational impact of railway transport to the surroundings, optimization of energy supply systems for railway transport, traction drives optimization and wear of wheels and rails

The dynamic interaction between a magnetically levitated vehicle and a flexible track

The only commercially operating magnetically levitated (maglev) transport system in the world is the link between Birmingham International Airport and the National Exhibition Centre. Comparative financial analysis for this route showed that the construction costs for both wheeled and maglev systems were similar and that the cost of the guideway accounted for over 70% of the total. In part this was because the guideway was elevated; a likely requirement for any future urban system. A substantial reduction in installation costs for a system of this nature can only be achieved by the use of cheap, lightweight and flexible guideways. The British Rail Research maglev vehicle was designed for use on a rigid guideway and it was known that excessive flexibility would make the suspension control system unstable. The aim of the study was to develop a maglev suspension control strategy that was insensitive to guideway flexibility. Vibration measurements were carried out on the Birmingham guideway to establish its modal properties. It was found to be sufficiently rigid to allow the existing controller to work without problems .Measurements were also made on the guideway of a Swiss cablecar transit system. This was felt to represent the extremes of both lightness and flexibility and established the range of guideway dynamics that were likely to be encountered. For the initial experimental work, a section of the British Rail maglev test track was modified to incorporate three sections of flexible track. A personal computer was installed on board the vehicle and software was written to aid frequency response testing and dynamic system modelling. Tests were carried out to establish the dynamic parameters of the new sections of guideway. The existing rigid guideway controller separated magnet control from suspension control. Guideway flexibility destroys this separation and induces additional feedback terms that degrade system stability. Theoretical studies of an improved controller took advantage of the fact that that the suspension magnets act directly onto the guideway and affect the position of both vehicle and guideway. As the guideway is lightly damped it is only flexible over a narrow bandwidth and the new suspension controller is able to use vehicle inertia to react forces that control the guideway at its natural frequency. Theory suggested that this would restore the separation of magnet and suspension control even with a flexible guideway. For a variety of reasons, experimental implementation of the new controller proved to be difficult. Suspension performance on the flexible portions of the guideway was never adequately demonstrated. The work did however enable a very accurate theoretical model of the system to be developed. This model contrasted with earlier predictions because, on rigid guideways, it predicted substantially smaller phase margins than the earlier models had suggested. It showed that the new controller had only modest benefits relative to the original rigid guideway suspension controller. This led to the development of an improved controller, a "lumped" controller where magnet and suspension control are not separated. Modelling for a single degree of freedom vehicle on a single mode guideway showed that large improvements in suspension performance could be made. Further modelling of a three degree of freedom vehicle and a five mode three degree of freedom flexible guideway used parameters that represent the production vehicles at Birmingham. This work defined limits for guideway flexibility and vehicle dynamic performance and showed that maglev guideways for production scale vehicles, with the "lumped" controller, can be very flexible indeed. The major aim of the project was achieved. A suspension controller was developed that will allow a maglev vehicle to work on a guideway that is far lighter, more flexible and far cheaper than the guideway required for a conventional wheeled vehicle

Reliability Analysis Of Low-Frequency Ac Transmission System Topology Of Offshore Wind Power Plants

Many countries and regions of the world are planning to reduce the energy sector\u27s carbon footprint and increase sustainable energy sources. To this end, wind power has become one of their primary renewable energy sources. However, wind power\u27s significant challenges relate to the need for long transmission lines that connect the offshore wind power plants to the onshore grid. The three major transmission configurations and design topologies of High Voltage AC (HVAC) Transmission, High Voltage DC (HVDC) Transmission, and Low-Frequency AC (LFAC) Transmission for offshore wind power resources have been thoroughly discussed both in industry and academia. HVAC is the standard transmission system for short and long distances. In contrast, HVDC is a popular solution for the long-distance transmission of offshore wind power generators. In recent years, LFAC transmission topology at 20Hz has become an alternative solution to HVAC and HVDC transmission systems. The significant advantages of LFAC transmission are the substantial increment of transmissible power over traditional AC transmission systems and the elimination of offshore converter stations. The absence of an offshore converter system renders LFAC transmission less costly compare to the HVDC system. The efficient design and reliability of offshore wind power transmission topologies are essential requirements for the transmission grid\u27s smooth operation. This thesis work extensively investigated and reviewed the LFAC transmission topologies over HVAC and HVDC transmissions topologies of offshore wind power plans. Different methods are used to assess the reliability performance of system designs. In this research, the state of the art of the simulation models for three transmission systems have been developed for reliability analysis of the above three transmission systems topologies using Fault tree analysis (FTA). This research has identified several reliability performance characteristics including minimal cut sets, importance measures, and time-based matrics (i.e, number of failures and mean unavailability) of the transmission systems, and compared these characteristics among three transmission systems. For reliability performance analysis, the time-base metrics, such as mean-unavailability and number of failures of the systems over 10,000 hours of operation, importance measures, or reliability importance measures, such as Critical Importance Measure (CIM) and Risk Reduction Worth (RRW), and Cut Sets have been calculated. The thesis has successfully identified major fault events for all the three transmission systems, and that the large switch is the most critical piece of equipment in the HVAC system, while the AC/DC or DC/AC converter is the most critical piece of equipment in the HVDC system, and the DC/AC converter and Cycloconverter are the most critical components in the LFAC transmission system. Furthermore, to enhance the offshore transmission systems reliability and ensure their smooth operation, effective and reliable offshore wind power generation predictions are critical. To this end, this research work also introduces the necessary offshore wind power forecasting tools

Resonant DC link converters and their use in rail traction applications

Conventional 'hard switching' converters suffer from significant switching loss due to thesimultaneous imposition of high values of current and voltage on the devices during commutation.Resonant converters offer a solution to this problem. A review of resonant circuit topologies ispresented, which includes a summary of the interference problems which may occur when usingpower converters in the rail traction environment. Particular attention is given to the ResonantDC Link Inverter (RDCLI) which shows a great deal of pronuse using currently availabledevices.The frequency domain simulation of RDCLIs is discussed as a means of rapidly evaluatingcircuit behaviour, especially in relation to modulation strategies. A novel modulation strategy isproposed for Resonant DC Link Inverters, based on a procedure known as Simulated Annealingwhich allows complex harmonic manipulations such as han-nonic minimisation, to be performed.This is despite the fact that RDCLIs are constrained to use Discrete Pulse Modulation wherebyswitch commutations are restricted to specific moments in time. The modulation algorithms wereverified by use of a low-power test rig and the results obtained are compared against theoreticalvalues. Details of the hardware implementation are also included.A single-phase pulse-converter input stage is described which may be incorporated into theResonant DC Link Inverter topology. This input stage also benefits from soft-sVVItching andallows four-quadrant operation at any desired power factor. A modulation scheme based onSiMulated Annealing is proposed for the pulse-converter, to achieve hannomc control whilst alsosynchronising with the supply wavefon-n. Practical results are presented and compared with thoseobtained by simulation and calculation.Finally the design of Resonant DC Link Converters is discussed and reconunendations made forthe choice of resonant components based on the minimisation of overall losses. Comparisons aremade between hard-switching and soft-switching converters in terms of loss and harmonicperformance, in an attempt to quantify the benefits which may be obtained by the application ofsoft-switching

The dynamic interaction between a magnetically levitated vehicle and a flexible track

The only commercially operating magnetically levitated (maglev) transport system in the world is the link between Birmingham International Airport and the National Exhibition Centre. Comparative financial analysis for this route showed that the construction costs for both wheeled and maglev systems were similar and that the cost of the guideway accounted for over 70% of the total. In part this was because the guideway was elevated; a likely requirement for any future urban system. A substantial reduction in installation costs for a system of this nature can only be achieved by the use of cheap, lightweight and flexible guideways. The British Rail Research maglev vehicle was designed for use on a rigid guideway and it was known that excessive flexibility would make the suspension control system unstable. The aim of the study was to develop a maglev suspension control strategy that was insensitive to guideway flexibility. Vibration measurements were carried out on the Birmingham guideway to establish its modal properties. It was found to be sufficiently rigid to allow the existing controller to work without problems .Measurements were also made on the guideway of a Swiss cablecar transit system. This was felt to represent the extremes of both lightness and flexibility and established the range of guideway dynamics that were likely to be encountered. For the initial experimental work, a section of the British Rail maglev test track was modified to incorporate three sections of flexible track. A personal computer was installed on board the vehicle and software was written to aid frequency response testing and dynamic system modelling. Tests were carried out to establish the dynamic parameters of the new sections of guideway. The existing rigid guideway controller separated magnet control from suspension control. Guideway flexibility destroys this separation and induces additional feedback terms that degrade system stability. Theoretical studies of an improved controller took advantage of the fact that that the suspension magnets act directly onto the guideway and affect the position of both vehicle and guideway. As the guideway is lightly damped it is only flexible over a narrow bandwidth and the new suspension controller is able to use vehicle inertia to react forces that control the guideway at its natural frequency. Theory suggested that this would restore the separation of magnet and suspension control even with a flexible guideway. For a variety of reasons, experimental implementation of the new controller proved to be difficult. Suspension performance on the flexible portions of the guideway was never adequately demonstrated. The work did however enable a very accurate theoretical model of the system to be developed. This model contrasted with earlier predictions because, on rigid guideways, it predicted substantially smaller phase margins than the earlier models had suggested. It showed that the new controller had only modest benefits relative to the original rigid guideway suspension controller. This led to the development of an improved controller, a "lumped" controller where magnet and suspension control are not separated. Modelling for a single degree of freedom vehicle on a single mode guideway showed that large improvements in suspension performance could be made. Further modelling of a three degree of freedom vehicle and a five mode three degree of freedom flexible guideway used parameters that represent the production vehicles at Birmingham. This work defined limits for guideway flexibility and vehicle dynamic performance and showed that maglev guideways for production scale vehicles, with the "lumped" controller, can be very flexible indeed. The major aim of the project was achieved. A suspension controller was developed that will allow a maglev vehicle to work on a guideway that is far lighter, more flexible and far cheaper than the guideway required for a conventional wheeled vehicle

Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version

On the performance of base-isolated buildings: a generic model

Ground-borne vibration has existed ever since the development of urban road and rail networks. Vibration generated by the moving traffic propagates through the ground and into buildings, resulting in unacceptable levels of internal noise and vibration. A common solution to this increasingly significant problem is the base-isolation of buildings by incorporating vibration isolation bearings between the buildings and their foundations. This technique has been employed for over forty years but the exact performance of base isolation remains uncertain. This dissertation is concerned with the development of a generic computational model; generic in that it accounts for the essential dynamic behaviour of a typical base-isolated building in order to make predictions of isolation performance. The model is a linear one, formulated in the frequency domain, and consists of a two-dimensional portal-frame model of a building coupled to a three-dimensional boundary-element model of a piled-foundation. Both components of the model achieve computational efficiency by assuming they are infinitely long and using periodic structure theory. The development of the model is described systematically, from the modelling of a building and its isolation bearings to that of its foundation. The majority of the work is concerned with the piled-foundation model, which is comprehensive in that it accounts for the vertical, horizontal and rotational motion of the pile heads due to both direct pile-head loading and interaction through wave propagation in the surrounding soil. It is shown that this level of detail is important in the prediction of base isolation efficiency. A key question facing designers is not only how but on what basis base isolation should be assessed, since fundamental problems exist with the existing measures of isolation performance. Power flow analysis is explored and the concept of power flow insertion gain, based on the total mean vibrational power flow entering a building, is introduced as a useful measure of isolation performance. This is shown to offer clear benefits by providing a single measure of performance that is suitable for design purposes. Finally, the development of a prototype force-sensitive vibration isolation bearing is described as a contribution to verifying base-isolation theory with experiments.This work was supported by the Engineering and Physical Sciences Research Council (PhD Studentship

Buildings and Structures under Extreme Loads II

Exceptional loads on buildings and structures are known to take origin and manifest from different causes, like natural hazards and possible high-strain dynamic effects, human-made attacks and impact issues for load-bearing components, possible accidents, and even unfavorable/extreme operational conditions. All these aspects can be critical for specific structural typologies and/or materials that are particularly sensitive to external conditions. In this regard, dedicated analysis methods and performance indicators are required for the design and maintenance under the expected lifetime. Typical issues and challenges can find huge efforts and clarification in research studies, which are able to address with experiments and/or numerical analyses the expected performance and capacity of a given structural system, with respect to demands. Accordingly, especially for existing structures or strategic buildings, the need for retrofit or mitigation of adverse effects suggests the definition of optimal and safe use of innovative materials, techniques, and procedures. This Special Issue follows the first successful edition and confirms the need of continuous research efforts in support of building design under extreme loads, with a list of original research papers focused on various key aspects of structural performance assessment for buildings and systems under exceptional design actions and operational conditions