Design Options for Hybrid Trains Powered by Hydrogen Fuel Cells and Batteries for Routes in the Highlands of Scotland. Results for the case of a three-coach multiple-unit train

This work builds on and extends a report prepared for the Scottish Association for Public Transport in June 2020 entitled Modelling and simulation of hybrid electric trains powered by hydrogen fuel cells and batteries for routes in the highlands of Scotland: Preliminary results. That report discussed some issues arising in the design of powertrain systems for hybrid hydrogen fuelcell/ battery-electric trains and included preliminary simulation results for the case of a two-coach multiple-unit train. The choice of power ratings of hydrogen fuel cell stacks and battery packs, along with battery storage capacity in fuel cell/battery-electric trains is seldom straightforward and requires careful analysis. This design problem is especially challenging for trains intended for use on routes involving significant distances, few intermediate stations and prolonged steep gradients. The work being reported here involves more detailed modelling of on-board power transmission systems and describes the application of model-based analysis methods and simulation techniques to estimate fuel cell and battery power ratings and battery storage capacity. The case considered here involves a three-coach hybrid configuration and differs significantly from that discussed in the previous report in a number of ways. Conventional simulation methods applied to train performance investigations allow estimates to be made of variables such as speed or position, usually as functions of time, for inputs such as tractive force or power. However, an inverse simulation approach is adopted here which provides the tractive force or power at the rail for a given time history of distance travelled as input. This allows direct investigation of power ratings and storage capacity for the fuel-cell stack and battery pack for specified levels of train performance defined by a required schedule. The mathematical model of the train, on which the simulation is based, is considered in two parts. The standard equations describing longitudinal train movement form the first part of the model, with the equations describing the hydrogen fuel-cell stack, battery pack, power electronic components and traction motors forming a separate sub-model. A simple test route is used initially, with several distinct stages. These involve acceleration from rest, steady state running at the line speed limit, a section with a steep rising gradient and subsequent stages involving coasting and braking. From the analysis carried out using this model and the simulation results from the test route, estimates are made of power and stored energy requirements for a specific section of the West Highland line. From the results it is suggested that a specification for a three-coach hybrid unit for use on steeply graded secondary routes could be based on three 250 kW traction motors, a fuel-cell stack providing a maximum power output of 500 kW together with a 375 kW battery pack providing between 210 kWh and 300 kWh of storage. Preliminary weight estimates suggest that this specification could be achieved for a three-coach train for a gross weight of the order of 135 tonnes, although the volume of the necessary equipment could (at the present time) be difficult to accommodate within restrictions imposed by the UK loading gauge. These calculations allow for inclusion of a pantograph and associated equipment for operation from 25 kV supplies on electrified routes. Conclusions are also reached about additional insight provided by the inverse simulation approach compared with conventional simulation methods when applied to powertrain design issues. It is believed that these benefits could apply also to investigations involving other forms of on-board power transmission and energy storage system

A Review of Developments in Electrical Battery, Fuel Cell and Energy Recovery Systems for Railway Applications: a Report for the Scottish Association for Public Transport

This report outlines the current status of batteries, hydrogen fuel cells and short-term energy storage systems for railway and tramway applications. The report includes discussion of issues associated with regenerative braking and the recovery of energy that would otherwise be dissipated as heat during braking. As well as feeding energy back to the supply grid, as in the case of conventional electrified rail systems, energy recovery may also be achieved using batteries, supercapacitors, flywheels or hydraulic devices and developments in each of these areas are reviewed. The advantages of hybrid systems that involve combinations of different power sources and energy storage methods are emphasised and some associated design optimisation issues are discussed. For each of the developments mentioned, there is a brief account given of some transport applications in the United Kingdom and elsewhere. This is a rapidly developing field and operating experience with vehicles currently entering service in various countries will provide important additional insight within the next two or three years

Modelling and Simulation of Hybrid Electric Trains Powered by Hydrogen Fuel Cells and Batteries for Routes in the Highlands of Scotland : Preliminary Results

This report builds on an earlier review for the Scottish Association for Public Transport on the potential of batteries, hydrogen fuel cells and other short-term energy storage systems for railway and tramway applications. It outlines the development of a train performance model and associated computer simulation software for a design of hybrid multiple unit, powered by a combination of hydrogen fuel cells and batteries. Assumptions underlying the model are discussed in detail. The chosen mode of operation involves steady state conditions for the fuel cells, with the batteries being used to provide additional stored energy for use on gradients and when the train is accelerating. The simulation techniques involve a mix of conventional “forward” simulation and an approach based on an “inverse” simulation method. Simulation results presented are for a case study involving a short section of route chosen to be typical of sections of many rural routes in Scotland, such as the West Highland lines and routes north and west of Inverness or to and from Stranraer. Data relating to the performance of Class 156 diesel multiple units currently used on non-electrified railway lines in Scotland have provided a point of reference in assessing the performance of the hybrid multiple units. Although other studies of hybrid rail vehicles involving hydrogen fuel cell and battery combinations have been published, those have involved routes that are shorter, with more intermediate stations and no prolonged gradients. Conclusions are presented in terms of fuel cell and battery power levels and battery storage capacity required for operation on the type of route being considered. The most important conclusion is that a preliminary specification for a hybrid two-coach unit could involve two 200 kW traction motors, fuel-cells providing a maximum power output of 350 kW and a battery pack giving a maximum power output of 250 kW and 75 kWh of electrical energy storage capacity. Using standard components that are available commencially, approximate calculations suggest that a design based around these power ratings could be implemented within a target weight of 90 tonnes for a two-coach unit. However, it is thought that the limitations of the UK loading gauge could present difficulties in terms of the space required and implementation might only be possible at the cost of some passenger space. Suggestions are made in the report for further simulation work involving a three-coach configuration and for the addition of a pantograph and associated electrical equipment to allow power to be drawn from 25 kV overhead wiring when the unit is operating on electrified routes. Another important recommendation for further work involves development of a detailed route model for a typical line, including exact information about gradients, curvature and local speed restrictions. Assessment of possible journey-time reductions is also important and preliminary results are presented, for the specification given above, using inverse simulation methods. Potential journey-time reductions over a complete route or specific sections could be investigated in future work. Issues of weight could also be linked to performance within the simulation software and advice could be provided to the user when space or weight constraints are violated. The report includes discussion of possible benefits of developing more detailed, physics-based, sub-models of elements such as fuel cells, batteries, traction motors and power electronic components which could be used to replace the much simpler sub-models used in the existing simulation model. This might allow use of well-established and validated sub-models and would extend the range of issues that could be addressed through simulation and allow more accurate assessment of losses in batteries, power electronic components and traction motors over the full range of operating conditions. This could also be of value for checking underlying assumptions within the model and for the development of control and energy management strategies. The report recommends the use of both forward and inverse methods of simulation for applications of this kind as these two approaches, taken together, can provide additional insight that is not obtained so readily from the use of conventional forward simulation methods alone

Some Issues in the Testing of Computer Simulation Models

The testing of simulation models has much in common with testing processes in other types of application involving software development. However, there are also important differences associated with the fact that simulation model testing involves two distinct aspects, which are known as verification and validation. Model validation is concerned with investigation of modelling errors and model limitations while verification involves checking that the simulation program is an accurate representation of the mathematical and logical structure of the underlying model. Success in model validation depends upon the availability of detailed information about all aspects of the system being modelled. It also may depend on the availability of high quality data from the system which can be used to compare its behaviour with that of the corresponding simulation model. Transparency, high standards of documentation and good management of simulation models and data sets are basic requirements in simulation model testing. Unlike most other areas of software testing, model validation often has subjective elements, with potentially important contributions from face- validation procedures in which experts give a subjective assessment of the fidelity of the model. Verification and validation processes are not simply applied once but must be used repeatedly throughout the model development process, with regressive testing principles being applied. Decisions about when a model is acceptable for the intended application inevitably involve some form of risk assessment. A case study concerned with the development and application of a simulation model of a hydro-turbine and electrical generator system is used to illustrate some of the issues arising in a typical control engineering application. Results from the case study suggest that it is important to bring together objective aspects of simulation model testing and the more subjective face- validation aspects in a coherent fashion. Suggestions are also made about the need for changes in approach in the teaching of simulation techniques to engineering students to give more emphasis to issues of model quality, testing and validation

Powering Future Transport in Scotland: A Review for the Scottish Association for Public Transport

This report discusses energy costs and emissions associated with transport in Scotland and reviews options for future power sources for different modes of public transport. Transport provides a major contribution to greenhouse gas and other harmful emissions worldwide and efforts to reduce these are important for all forms of public transport, as well as for private cars and for the movement of freight. The effects of transport policy decisions are recognised, increasingly, as being very important for the electricity supply industry at national and local levels, largely because of the growth in the numbers of electric and hybrid road vehicles. Moving from oil to low carbon energy for transport raises important issues for electrical power generation and distribution systems in addition to challenges already being faced by the electrical power industry as the proportion of generating capacity involving renewables increases. The report starts by considering current energy costs and emissions for different forms of passenger transport and then outlines some current developments in areas such as internal combustion engine technology, battery storage systems and hydrogen fuel cells. Systems involving short-term energy storage and recovery of energy that would otherwise be dissipated as heat during braking are also discussed. Such systems generally involve the use of super-capacitors, flywheels or hydraulic devices. References are provided to the sources of data used in the analysis carried out for this review and, also, to sources of information about relevant developments in science and engineering. For all the new developments mentioned, there is a brief review of some transport applications in the United Kingdom and elsewhere. The possible impact of autonomous vehicles on future car ownership is still not known and the effects of this technology on public transport remain uncertain. As well as discussing autonomous road vehicles, the report makes brief mention of the potential of autonomous systems and increased automation for rail transport and for tramway operations. The benefits of further conventional railway electrification are reviewed in terms of energy usage, costs and emissions and the advantages of a more integrated approach to the provision of public transport in Scotland are emphasised. The value of using mathematical modelling and simulation methods to explore options in transport systems developments and planning is discussed, and the importance of testing simulation models in ways that are appropriate for the intended application is emphasised. This review presents the first results from a continuing study which was started in 2018 and is intended to provide information that should be relevant for those involved in decision-making in Scotland at the time of publication. The quantitative information contained within it clearly needs to be updated on a regular basis. The review concludes with recommendations for the Scottish Association for Public Transport about possible priorities for its efforts to increase public awareness about transport issues and is intended to be the first of a series of publications on transport and energy issues in the Scottish context. The references form an important part of the report and provide a potentially important bibliography which must be augmented and updated regularly

Inverse simulation and analysis of underwater vehicle dynamics using feedback principles

Inverse simulation is a technique used in the modelling of dynamic systems that allows time histories of input variables to be found that generate required model output responses and provide inverse solutions in cases where analytical approaches to model inversion can present difficulties. This paper describes the application of inverse simulation to a nonlinear dynamic model of an underwater vehicle (UUV) and the determination of vehicle control inputs for specified manoeuvres. The approach to inverse simulation used in this application is based on the principles of feedback. Design issues relating to the UUV control surfaces and propeller thrust are highlighted through this procedure. The paper includes an outline of the nonlinear model of the UUV and typical sets of experimental conditions. Feedback loops are designed around the model for selected output variables and the inverse solutions are generated through simulation of this multi-input multi-output closed-loop system. It is shown that the feedback approach can provide inverse solutions for an appropriate choice of loop gain factors and integration time step using a fixed-step integration algorithm. Inverse solutions generated in this way are shown provide insight concerning issues of vehicle handling and manoeuvrability in a more direct fashion than is possible using conventional simulation methods

Methods of system identification, parameter estimation and optimisation applied to problems of modelling and control in engineering and physiology

Mathematical and computer-based models provide the foundation of most methods of engineering design. They are recognised as being especially important in the development of integrated dynamic systems, such as “control-configured” aircraft or in complex robotics applications. These models usually involve combinations of linear or nonlinear ordinary differential equations or difference equations, partial differential equations and algebraic equations. In some cases models may be based on differential algebraic equations. Dynamic models are also important in many other fields of research, including physiology where the highly integrated nature of biological control systems is starting to be more fully understood. Although many models may be developed using physical, chemical, or biological principles in the initial stages, the use of experimentation is important for checking the significance of underlying assumptions or simplifications and also for estimating appropriate sets of parameters. This experimental approach to modelling is also of central importance in establishing the suitability, or otherwise, of a given model for an intended application – the so-called “model validation” problem. System identification, which is the broad term used to describe the processes of experimental modelling, is generally considered to be a mature field and classical methods of identification involve linear discrete-time models within a stochastic framework. The aspects of the research described in this thesis that relate to applications of identification, parameter estimation and optimisation techniques for model development and model validation mainly involve nonlinear continuous time models Experimentally-based models of this kind have been used very successfully in the course of the research described in this thesis very in two areas of physiological research and in a number of different engineering applications. In terms of optimisation problems, the design, experimental tuning and performance evaluation of nonlinear control systems has much in common with the use of optimisation techniques within the model development process and it is therefore helpful to consider these two areas together. The work described in the thesis is strongly applications oriented. Many similarities have been found in applying modelling and control techniques to problems arising in fields that appear very different. For example, the areas of neurophysiology, respiratory gas exchange processes, electro-optic sensor systems, helicopter flight-control, hydro-electric power generation and surface ship or underwater vehicles appear to have little in common. However, closer examination shows that they have many similarities in terms of the types of problem that are presented, both in modelling and in system design. In addition to nonlinear behaviour; most models of these systems involve significant uncertainties or require important simplifications if the model is to be used in a real-time application such as automatic control. One recurring theme, that is important both in the modelling work described and for control applications, is the additional insight that can be gained through the dual use of time-domain and frequency-domain information. One example of this is the importance of coherence information in establishing the existence of linear or nonlinear relationships between variables and this has proved to be valuable in the experimental investigation of neuromuscular systems and in the identification of helicopter models from flight test data. Frequency-domain techniques have also proved useful for the reduction of high-order multi-input multi-output models. Another important theme that has appeared both within the modelling applications and in research on nonlinear control system design methods, relates to the problems of optimisation in cases where the associated response surface has many local optima. Finding the global optimum in practical applications presents major difficulties and much emphasis has been placed on evolutionary methods of optimisation (both genetic algorithms and genetic programming) in providing usable methods for optimisation in design and in complex nonlinear modelling applications that do not involve real-time problems. Another topic, considered both in the context of system modelling and control, is parameter sensitivity analysis and it has been found that insight gained from sensitivity information can be of value not only in the development of system models (e.g. through investigation of model robustness and the design of appropriate test inputs), but also in feedback system design and in controller tuning. A technique has been developed based on sensitivity analysis for the semi-automatic tuning of cascade and feedback controllers for multi-input multi-output feedback control systems. This tuning technique has been applied successfully to several problems. Inverse systems also receive significant attention in the thesis. These systems have provided a basis for theoretical research in the control systems field over the past two decades and some significant applications have been reported, despite the inherent difficulties in the mathematical methods needed for the nonlinear case. Inverse simulation methods, developed initially by others for use in handling-qualities studies for fixed-wing aircraft and helicopters, are shown in the thesis to provide some important potential benefits in control applications compared with classical methods of inversion. New developments in terms of methodology are presented in terms of a novel sensitivity based approach to inverse simulation that has advantages in terms of numerical accuracy and a new search-based optimisation technique based on the Nelder-Mead algorithm that can handle inverse simulation problems involving hard nonlinearities. Engineering applications of inverse simulation are presented, some of which involve helicopter flight control applications while others are concerned with feed-forward controllers for ship steering systems. The methods of search-based optimisation show some important advantages over conventional gradient-based methods, especially in cases where saturation and other nonlinearities are significant. The final discussion section takes the form of a critical evaluation of results obtained using the chosen methods of system identification, parameter estimation and optimisation for the modelling and control applications considered. Areas of success are highlighted and situations are identified where currently available techniques have important limitations. The benefits of an inter-disciplinary and applications-oriented approach to problems of modelling and control are also discussed and the value in terms of cross-fertilisation of ideas resulting from involvement in a wide range of applications is emphasised. Areas for further research are discussed

Some Issues in the Testing of Computer Simulation Models

The testing of simulation models has much in common with testing processes in other types of application involving software development. However, there are also important differences associated with the fact that simulation model testing involves two distinct aspects, which are known as verification and validation. Model validation is concerned with investigation of modelling errors and model limitations while verification involves checking that the simulation program is an accurate representation of the mathematical and logical structure of the underlying model. Success in model validation depends upon the availability of detailed information about all aspects of the system being modelled. It also may depend on the availability of high quality data from the system which can be used to compare its behaviour with that of the corresponding simulation model. Transparency, high standards of documentation and good management of simulation models and data sets are basic requirements in simulation model testing. Unlike most other areas of software testing, model validation often has subjective elements, with potentially important contributions from face- validation procedures in which experts give a subjective assessment of the fidelity of the model. Verification and validation processes are not simply applied once but must be used repeatedly throughout the model development process, with regressive testing principles being applied. Decisions about when a model is acceptable for the intended application inevitably involve some form of risk assessment. A case study concerned with the development and application of a simulation model of a hydro-turbine and electrical generator system is used to illustrate some of the issues arising in a typical control engineering application. Results from the case study suggest that it is important to bring together objective aspects of simulation model testing and the more subjective face- validation aspects in a coherent fashion. Suggestions are also made about the need for changes in approach in the teaching of simulation techniques to engineering students to give more emphasis to issues of model quality, testing and validation

The infrared imaging spectrograph (IRIS) for TMT: on-instrument wavefront sensors and NFIRAOS interface

The InfraRed Imaging Spectrograph (IRIS) is a first light client science instrument for the TMT observatory that operates as a client of the NFIRAOS facility multi-conjugate adaptive optics system. This paper reports on the concept study and baseline concept design of the On-Instrument WaveFront Sensors (OIWFS) and NFIRAOS interface subsystems of the IRIS science instrument, a collaborative effort by NRC-HIA, Caltech, and TMT AO and Instrument teams. This includes work on system engineering, structural and thermal design, sky coverage modeling, patrol geometry, probe optics and mechanics design, camera design, and controls design.Comment: 17 pages, 12 figures, SPIE7735-28

Rural Cultural Studies: Introduction

This themed section of Australian Humanities Review seeks to establish the emerging field of \u27rural cultural studies\u27 firmly on the agenda of the contemporary humanities and social sciences. This is a timely intervention as rural Australia has featured increasingly over the last decade and especially over the last few years as a topic of national policy attention, public commentary and social analysis. If the notion of a crisis in rural Australia has become something of a one-sided cliché, the changes being faced in non-urban-rural, remote and regional-Australia are nonetheless significant, complex and widespread. For example, one of the topics for the federal 2020 Summit, \u27Rural Australia\u27, addressed future policy directions for rural industries and populations. In this wider context, the purpose of the present collection of papers is to argue for the significance of the cultural dimension-and the multiple dimensions of the cultural-in understanding the key issues of demographic change, economic productivity, environmental and climatic crisis, Indigenous/non-indigenous relations and land ownership, and the role of \u27cultural\u27 factors in the renewal, or potential renewal, of country towns and communities