• Selective laser melting of a high precision turbomachinery application in IN718 alloy

      Wood, Paul; Gunputh, Urvashi; Williams, Gavin; Carter, Wayne; Boud, Fathi; Bahi, Slim; Rusinek, Alexis; Kowalewski, Zbigniew; Nowak, Zdzisław; Libura, Tomasz; et al. (2021)
      The paper describes the manufacture of an outlet guide vane (OGV) component, in IN718 alloy, used in jet engines by Selective Laser Melting (SLM). The OGV component is a static part in the last stage of the compressor and is characterised as a series of airfoils or vanes secured by two flanged rings. The part tolerances at the leading and trailing edge require a high dimensional precision of +/-0.072 m whilst the profile tolerances are slightly more generous. The current challenge to manufacture a prototype OGV in IN718 alloy from a wrought stock involves a lengthy machining process in a hard-to-machine alloy. The tooling access is greatly restricted between the curved vanes, and the process involves careful fixturing and process management to mitigate residual stress in the component arising from the removal of material.
    • Analysis of machining performance of Inconel 718 printed by PBF-LM (powder bed fusion laser melting)

      Diaz-Alvarez, A; Diaz-Alvarez, J; Wood, P; Gunputh, U; Rusinek, A; Miguelez, M; University of Derby (2021)
      Additive manufacturing based on powder bed fusion laser melting (PBF-LM) is receiving increased attention in nickel-base superalloys manufacturing, due to the difficulty of removal processes of superalloys. PBF-LM process involves the use of high-energy laser beam (continuous or pulsed) to melt a thin layer of metal powder under an inert or near-inert gas atmosphere. After rapid solidification, a new layer of powder is deposited and exposed again to the laser, repeating the process until the whole piece is obtained. The Inconel 718 alloy is one of the most widely used nickel-based alloys in jet engines and industrial steam turbines for components that operate at high temperature and require high resistance to fatigue and corrosion. Additive manufacturing processes commonly require further finishing operations in order to achieve dimensional and surface specifications of the workpiece. The present study focuses on the analysis of machining of Inconel 718 pieces manufactured through the PBF-LM process, when it is compared with the reference piece manufactured through conventional method. This paper investigates the cutting forces and the relationship to tool wear in machining Inconel 718 alloy obtained through the PBF-LM technique and conventional methods.
    • A novel technique for dynamic shear testing of bulk metals with application to 304 austenitic stainless steel

      Jia, B.; Rusinek, A.; Pesci, R.; Bernier, R.; Bahi, S.; Wood, P.; ENSAM-Arts et Métiers ParisTech, Paris; Lorraine University, France; Institute of Fundamental Technological Research, Warsaw, Poland; Carlos III University, Madrid; et al. (Elsevier BV, 2020-09-03)
      This paper describes a new single-shear specimen (SSS) and method to characterize the dynamic shear behavior of bulk metals using a traditional Split Hopkinson Pressure Bar (SHPB). By this method, the shear behavior of materials can be tested conveniently over a wide range of strain rates within 105 s−1. This technique was applied to a 304 austenitic stainless steel (ASS) under shear strain rates from 0.001 s−1 to 38700 s−1 at room temperature. Based on finite element (FE) simulations, it was found that the deformation of the specimen shear zone was dominated by shear stress/strain components. Stress state parameters represented by stress triaxiality and Lode angle parameter were found very close to zero, indicating a deformation mode of simple shear. Besides, an obvious gap existed between the local deformation behavior in the specimen shear zone and the macroscopic stress-strain relations measured by the strain gauges on the SHPB bars. A correction coefficient method was adopted to extract the real shear behavior from the experimentally obtained force-displacement data. Through comparisons between the tested and simulated stress-strain curves, a good agreement was obtained.
    • Influences of horizontal and vertical build orientations and post-fabrication processes on the fatigue behavior of stainless steel 316l produced by selective laser melting

      Wood, Paul; Libura, Tomasz; Kowalewski, Zbigniew L.; Williams, Gavin; Serjouei, Ahmad; University of Derby; The Polish Academy of Sciences; Nottingham Trent University (MDPI AG, 2019-12-14)
      In this paper, the influences of build orientation and post-fabrication processes, including stress-relief, machining, and shot-peening, on the fatigue behavior of stainless steel (SS) 316L manufactured using selective laser melting (SLM) are studied. It was found that horizontally-built (XY) and machined (M) test pieces, which had not been previously studied in the literature, in both stress-relieved (SR) or non-stress-relieved (NSR) conditions show superior fatigue behavior compared to vertically-built (ZX) and conventionally-manufactured SS 316L. The XY, M, and SR (XY-M-SR) test pieces displayed fatigue behavior similar to the XY-M-NSR test pieces, implying that SR does not have a considerable effect on the fatigue behavior of XY and M test pieces. ZX-M-SR test pieces, due to their considerably lower ductility, exhibited significantly larger scatter and a lower fatigue strength compared to ZX-M-NSR samples. Shot-peening (SP) displayed a positive effect on improving the fatigue behavior of the ZX-NSR test pieces due to a compressive stress of 58 MPa induced on the surface of the test pieces. Fractography of the tensile and fatigue test pieces revealed a deeper understanding of the relationships between the process parameters, microstructure, and mechanical properties for SS 316L produced by laser systems. For example, fish-eye fracture pattern or spherical stair features were not previously observed or explained for cyclically-loaded SLM-printed parts in the literature. This study provides comprehensive insight into the anisotropy of the static and fatigue properties of SLM-printed parts, as well as the pre- and post-fabrication parameters that can be employed to improve the fatigue behavior of steel alloys manufactured using laser systems.
    • Additive manufacturing of graded structures in IN718

      Wood, Paul; Gunputh, Urvashi; University of Derby (2019-08)
      Workshop at LSU, USA 13th to 16th August 2019
    • Selective laser melting of stainless steel 316L pressure fittings

      Wood, Paul; University of Derby (2019-04-19)
      Workshop presentation DYNAMAT, 17-19 April 2019, Nicosia, Cyprus.
    • Module layout optimization using a genetic algorithm in light water modular nuclear reactor power plants.

      Wrigley, P.A.; Wood, P.; Stewart, Paul; Robertson, D.; University of Derby; University of Sheffield; Rolls-Royce Plc (Elsevier, 2018-11-03)
      The Small Modular Reactor (SMR) concept is designed such that it will solve some of the construction problems of large reactors. SMRs are designed to be “shop fabricated and then transported as modules to the sites for installation” (IAEA, 2018). As a consequence they theoretically have shorter build schedules and require less capitalinvestment(Locatelli etal.,2014).Factory builtmodulescanalsoincreasesafetyandproductivity, dueto higher quality tools and inspection available. A literature review has highlighted substantial work has been undertaken in the research, development and construction of different types of reactors and reactor modules but the design of balance of plant modules has not been extensively researched (Wrigley et al., 2018). The focus of this paperis a casestudy for balanceofplant modulesin alightwaterreactorwhich alsocould haveapplications to other reactor types. Modules thataredesignedfor factorybuildandtransport maybebuiltinastandardized moduleapproach.By maximizing module size for transport, this maximizes work offsite, to achieve the cost and schedule savings associated. A design method needs to be developed to help support this approach. To enable this, a three step method is proposed: group components into modules, layout the modules and arrange components inside the modules. The Shearon Harris nuclear power plant was chosen for its publically available data. A previous study on this plant used matrix reordering techniques to group components and heuristically assign them to large modules, built for construction in an assembly area on site, highlighting a potential capital cost savings of 15%. This paper utilizes the same allocation of components to modules as the previous study but aims to undertake the challenge of how balance of plant modules should be arranged. The literature review highlighted that although the facility and plant layout problem has been extensively researched, mathematical layout optimization has not been applied to nuclear power plants. Many techniques for layout optimization have been developed for facilities and process plants however. The work in this paper develops an optimization model using a genetic algorithm for module layout and allocation within a nuclear power plant. This paper analysed two configurations of modules, where balance of plant modules are located on either one or two sides of the nuclear island. The objective function was to minimise pipe length. In the original research, where the plant was configured for assembly on site, the balance of plant modules are located around three sides of the nuclear island. The objective function was calculated at 14,914. As the distances are calculated rectilinearly, this number would be higher in reality as pipework has to be routed around containment. The optimization reduced the objective function by 33.9% and 37.8% for the three and four floor layouts respectively when balance of plant modules are located on two sides of the nuclear island. Furthermore, when modules are located on one side of the nuclear island, the objective function was reduced by 45.4% and 46.1% for three and four floor layouts respectively. This will reduce materials used, reduce build time and hence reduce the cost of a nuclear power plant. This method will also save design time when developing the layout of modules around the plant.
    • Module layout optimization using a genetic algorithm in light water modular nuclear reactor power plants.

      Wrigley, P.A.; Wood, Paul; Stewart, Paul; Hall, Richard; Robertson, D.; University of Derby; University of Sheffield; Rolls-Royce Plc (Elsevier, 2018-11-03)
      The Small Modular Reactor (SMR) concept is designed such that it will solve some of the construction problems of large reactors. SMRs are designed to be “shop fabricated and then transported as modules to the sites for installation” (IAEA, 2018). As a consequence they theoretically have shorter build schedules and require less capital investment (Locatelli et al., 2014). Factory built modules can also increase safety and productivity, due to higher quality tools and inspection available. A literature review has highlighted substantial work has been undertaken in the research, development and construction of different types of reactors and reactor modules but the design of balance of plant modules has not been extensively researched (Wrigley et al., 2018). The focus of this paper is a case study for balance of plant modules in a light water reactor which also could have applications to other reactor types. Modules that are designed for factory build and transport may be built in a standardized module approach. By maximizing module size for transport, this maximizes work offsite, to achieve the cost and schedule savings associated. A design method needs to be developed to help support this approach. To enable this, a three step method is proposed: group components into modules, layout the modules and arrange components inside the modules. The Shearon Harris nuclear power plant was chosen for its publically available data. A previous study on this plant used matrix reordering techniques to group components and heuristically assign them to large modules, built for construction in an assembly area on site, highlighting a potential capital cost savings of 15%. This paper utilizes the same allocation of components to modules as the previous study but aims to undertake the challenge of how balance of plant modules should be arranged. The literature review highlighted that although the facility and plant layout problem has been extensively researched, mathematical layout optimization has not been applied to nuclear power plants. Many techniques for layout optimization have been developed for facilities and process plants however. The work in this paper develops an optimization model using a genetic algorithm for module layout and allocation within a nuclear power plant. This paper analysed two configurations of modules, where balance of plant modules are located on either one or two sides of the nuclear island. The objective function was to minimise pipe length. In the original research, where the plant was configured for assembly on site, the balance of plant modules are located around three sides of the nuclear island. The objective function was calculated at 14,914. As the distances are calculated rectilinearly, this number would be higher in reality as pipework has to be routed around containment. The optimization reduced the objective function by 33.9% and 37.8% for the three and four floor layouts respectively when balance of plant modules are located on two sides of the nuclear island. Furthermore, when modules are located on one side of the nuclear island, the objective function was reduced by 45.4% and 46.1% for three and four floor layouts respectively. This will reduce materials used, reduce build time and hence reduce the cost of a nuclear power plant. This method will also save design time when developing the layout of modules around the plant.
    • A computational strategy for damage-tolerant design of hollow shafts under mixed-mode loading condition.

      Lepore, Marcello Antonio; Yarullin, Rustam; Maligno, Angelo; Sepe, Raffaele; University of Salerno; Kazan Scientific Center of Russian Academy of Sciences; University of Derby; University of Naples Federico II; Department of Industrial Engineering; University of Salerno; Via G. Paolo II 132-84084 Fisciano Italy; Kazan Scientific Center of Russian Academy of Sciences; Lobachevsky Street 2/31-420111 Kazan Russia; et al. (Wiley, 2018-10-14)
      Three‐dimensional numerical analyses, using the finite element method (FEM), have been adopted to simulate fatigue crack propagation in a hollow cylindrical specimen, under pure axial or combined axial‐torsion loading conditions. Specimens, made of Al alloys B95AT and D16T, have been experimentally tested under pure axial load and combined in‐phase constant amplitude axial and torsional loadings. The stress intensity factors (SIFs) have been calculated, according to the J‐integral approach, along the front of a part through crack, initiated in correspondence of the outer surface of a hollow cylindrical specimen. The crack path is evaluated by using the maximum energy release rate (MERR) criterion, whereas the Paris law is used to calculate crack growth rates. A numerical and experimental comparison of the results is presented, showing a good agreement in terms of crack growth rates and paths.
    • Analysis of parameters influencing build accuracy of a SLM printed compressor outlet guide vane

      Otubusin, Adetayo; Wood, Paul; Appleby, John; Adamczuk, Rafael; University of Derby; Florida Turbine Technologies (UK) Ltd, Derby (American Society of Mechanical Engineers, 2018-08-30)
      The paper describes the manufacture of an outlet guide vane (OGV) of jet engines by the Selective Laser Melting (SLM) process, in view of current challenges for conventional machining approaches such as; high airfoil profile tolerances, limited tooling access and hard to machine materials like nickel-chromium-based super alloys. Within this paper, analysis was conducted to investigate the influence of build parameters on possible distortion during printing that affect the build accuracy. These parameters include the part orientation on the build plate, thickness change to the flanges and the positioning of the support structure of each part. The configurations are 3D printed using the SLM approach. The chosen material is IN625. The printed parts are 3D scanned and the results are compared to the original CAD design. The results confirmed the presence of distortions in printed parts and the effect of parameter changes. Furthermore, it was shown that improvements to the print parameters are necessary to achieve a satisfactory profile tolerance.
    • Design for plant modularisation: nuclear and SMR.

      Wrigley, Paul; Wood, Paul; Stewart, Paul; Hall, Richard; Robertson, Dan; University of Derby; Rolls-Royce Plc; University of Derby, Derby, UK; University of Derby, Derby, UK; University of Derby, Derby, UK; et al. (ASME Journals, 2018-07-22)
      The UK Small Modular Reactor (UKSMR) programme has been established to develop an SMR for the UK energy market. Developing an SMR is a multi-disciplinary technical challenge, involving nuclear physics, electrical, mechanical, design, management, safety, testing to name but a few. In 2016 Upadhyay & Jain performed a literature review on modularity in Nuclear Power. They concluded that although modularisation has been utilised in nuclear to reduce costs, more work needs to be done to “create effective modules”. Hohmann et al also concluded the same for defining modules in the chemical process plant industry. The aim of this paper is to further define modules with a particular focus on an SMR for the UK market, the UKSMR. The methods highlighted may be relevant and applied to other international SMR designs or other types of plant. An overview and examination of modularisation work in nuclear to date is provided. The different configurations are defined for the Nuclear Steam Supply System (NSSS) in primary circuits and then for Balance of Plant (BOP) modules. A top level design process has been defined to aid in the understanding of design choices for current reactors and to further assist designing balance of plant modules. The paper then highlights areas for additional research that may further support module design and definition.
    • Preference-based evolutionary algorithm for airport surface operations.

      Weiszer, Michal; Chen, Jun; Stewart, Paul; Zhang, Xuejun; Queen Mary University of London; University of Derby; Beihang University; National Key Laboratory of CNS/ATM (Elsevier, 2018-04-21)
      In addition to time efficiency, minimisation of fuel consumption and related emissions has started to be considered by research on optimisation of airport surface operations as more airports face severe congestion and tightening environmental regulations. Objectives are related to economic cost which can be used as preferences to search for a region of cost efficient and Pareto optimal solutions. A multi-objective evolutionary optimisation framework with preferences is proposed in this paper to solve a complex optimisation problem integrating runway scheduling and airport ground movement problem. The evolutionary search algorithm uses modified crowding distance in the replacement procedure to take into account cost of delay and fuel price. Furthermore, uncertainty inherent in prices is reflected by expressing preferences as an interval. Preference information is used to control the extent of region of interest, which has a beneficial effect on algorithm performance. As a result, the search algorithm can achieve faster convergence and potentially better solutions. A filtering procedure is further proposed to select an evenly distributed subset of Pareto optimal solutions in order to reduce its size and help the decision maker. The computational results with data from major international hub airports show the efficiency of the proposed approach.
    • Evaluating the environmental dimension of material efficiency strategies relating to the circular economy.

      Walker, Stuart; Coleman, Nick; Hodgson, Peter; Collins, Nicola; Brimacombe, Louis; University of Sheffield; Tata Steel; Savills Property Management (MDPI, 2018-03-01)
      Material efficiency is a key element of new thinking to address the challenges of reducing impacts on the environment and of resource scarcity, whilst at the same time meeting service and functionality demands on materials. Directly related to material efficiency is the concept of the Circular Economy, which is based on the principle of optimising the utility embodied in materials and products through the life-cycle. Although materials such as steel, on account of high recycling rates at end-of-life, are amongst the most ‘circular’ of manufactured materials, significant opportunities for greater material efficiency exist, which are yet to be widely implemented. Life Cycle Assessment (LCA) is commonly used to assess the environmental benefits of recovering and recycling materials through the manufacturing supply chain and at end-of-life. Using an example taken from renewable energy generation, this paper explores the correlation between product circularity and the environmental case for strategies designed to improve material efficiency. An LCA-based methodology for accounting for the recovery and reuse of materials from the supply chain and at end-of-life is used as the basis for calculating the carbon footprint benefits of five material efficiency scenarios. The results are compared with a number of proposed material circularity indicators. Two conclusions from this exercise are that (i) LCA methodologies based around end-of-life approaches are well placed for quantifying the environmental benefits of material efficiency and circular economy strategies and (ii) when applying indicators relating to the circularity of materials these should also be supported by LCA-based studies.
    • Simplified and accurate stiffness of a prismatic anisotropic thin-walled box.

      Canale, Giacomo; Rubino, Felice; Weaver, Paul M.; Citarella, Roberto; Maligno, Angelo; Rolls-Royce Plc; University of Salerno; University of Bristol; University of Derby (Bentham Open, 2018-02-14)
      Background: Beam models have been proven effective in the preliminary analysis and design of aerospace structures. Accurate cross sectional stiffness constants are however needed, especially when dealing with bending, torsion and bend-twist coupling deformations. Several models have been proposed in the literature, even recently, but a lack of precision may be found when dealing with a high level of anisotropy and different lay-ups. Objective: A simplified analytical model is proposed to evaluate bending and torsional stiffness of a prismatic, anisotropic, thin-walled box. The proposed model is an extension of the model proposed by Lemanski and Weaver for the evaluation of the bend-twist coupling constant. Methods: Bending and torsional stiffness are derived analytically by using physical reasoning and by applying bending and torsional stiffness mathematic definition. Unitary deformations have been applied when evaluation forces and moments arising on the cross section. Results: Good accuracy has been obtained for structures with different geometries and lay-ups. The model has been validated with respect to finite element analysis. Numerical results are commented upon and compared with other models presented in literature. Conclusion: For cross sections with a high level of anisotropy, the accuracy of the proposed formulation is within 2% for bending stiffness and 6% for torsional stiffness. The percentage of error is further reduced for more realistic geometries and lay-ups. The proposed formulation gives accurate results for different dimensions and length rations of horizontal and vertical walls.
    • Robust fault estimation for wind turbine energy via hybrid systems.

      Odofin, Sarah; Bentley, Edward; Aikhuele, Daniel; University of Derby; Nothumbria University; Bells University of Technology (Elsevier, 2017-12-15)
      The rapid development of modern wind turbine technology has led to increasing demand for improving system reliability and practical concern for robust fault monitoring scheme. This paper presents the investigation of a 5 MW Dynamic Wind Turbine Energy System that was designed to sustain condition monitoring and fault diagnosis with the goal of improving the reliability operations of universal practical control systems. A hybrid stochastic technique is proposed based on an augmented observer combined with eigenstructure assignment for the parameterisation and the genetic algorithm (GA) optimisation to address the attenuation of uncertainty mostly generated by disturbances. Scenarios-based are employed to explore sensor and actuator faults that have direct and indirect impacts on modern wind turbine system, based on monitoring components that are prone to malfunction. The analysis is aimed to determine the effect of concerned simulated faults from uncertainty in respect to environmental disturbances mostly challenged in real-world operations. The efficiency of the proposed approach will improve the reliability performance of wind turbine system states and diagnose uncertain faults simultaneously. The simulation outcomes illustrate the robustness of the dynamic turbine systems with a diagnostic performance to advance the practical solutions for improving reliable systems.
    • Primary and albedo solar energy sources for high altitude persistent air vehicle operation

      Smith, Tim; Trancossi, Michele; Vucinic, Dean; Bingham, Chris; Stewart, Paul; University of Lincoln; Sheffield Hallam University; Vrije Universiteit Brussel; University of Derby (Multidisciplinary Digital Publishing Institute (MDPI), 2017-04-22)
      A new class of the all electric airship to globally transport both passengers and freight using a ‘feeder‐cruiser’ concept, and powered by renewable electric energy, is considered. Specific focus is given to photo‐electric harvesting as the primary energy source and the associated hydrogen‐based energy storage systems. Furthermore, it is shown that the total PV output may be significantly increased by utilising cloud albedo effects. Appropriate power architectures and energy audits required for life support, and the propulsion and ancillary loads to support the continuous daily operation of the primary airship (cruiser) at stratospheric altitudes (circa 18 km), are also considered. The presented solution is substantially different from those of conventional aircraft due to the airship size and the inherent requirement to harvest and store sufficient energy during “daylight” operation, when subject to varying seasonal conditions and latitudes, to ensure its safe and continued operation during the corresponding varying “dark hours”. This is particularly apparent when the sizing of the proposed electrolyser is considered, as its size and mass increase nonlinearly with decreasing day‐night duty. As such, a Unitized Regenerative Fuel Cell is proposed. For the first time the study also discusses the potential benefits of integrating the photo‐voltaic cells into airship canopy structures utilising TENSAIRITY®‐based elements in order to eliminate the requirements for separate inter‐PV array wiring and the transport of low pressure hydrogen between fuel cells.
    • Experimental studies of turbulent intensity around a tidal turbine support structure

      Walker, Stuart; Cappietti, Lorenzo; University of Sheffield; Università degli Studi di Firenze (MDPI, 2017-04-07)
      Tidal stream energy is a low-carbon energy source. Tidal stream turbines operate in a turbulent environment, and the effect of the structure between the turbine and seabed on this environment is not fully understood. An experimental study using 1:72 scale models based on a commercial turbine design was carried out to study the support structure influence on turbulent intensity around the turbine blades. The study was conducted using the wave-current tank at the Laboratory of Maritime Engineering (LABIMA), University of Florence. A realistic flow environment (ambient turbulent intensity = 11%) was established. Turbulent intensity was measured upstream and downstream of a turbine mounted on two different support structures (one resembling a commercial design, the other the same with an additional vertical element), in order to quantify any variation in turbulence and performance between the support structures. Turbine drive power was used to calculate power generation. Acoustic Doppler velocimetry (ADV) was used to record and calculate upstream and downstream turbulent intensity. In otherwise identical conditions, performance variation of only 4% was observed between two support structures. Turbulent intensity at 1, 3 and 5 blade diameters, both upstream and downstream, showed variation up to 21% between the two cases. The additional turbulent structures generated by the additional element of the second support structure appears to cause this effect, and the upstream propagation of turbulent intensity is believed to be permitted by surface waves. This result is significant for the prediction of turbine array performance.
    • Retardation effects due to overloads in aluminium-alloy aeronautical components

      Maligno, Angelo; Citarella, Roberto; Silberschmidt, Vadim V.; University of Derby; University of Salerno; University of Loughborough; Institute for Innovation in Sustainable Engineering; University of Derby; Quaker Way, Derby DE1 3HD UK; Department of Industrial Engineering; University of Salerno; via Giovanni Paolo II, Fisciano SA Italy; Wolfson School of Mechanical and Manufacturing Engineering; Loughborough University; Loughborough UK (Wiley, 2017-02-08)
      Fatigue data are generally derived under constant-amplitude loading conditions, but aircraft components are subjected to variable-amplitude loading. Without interaction effects, caused by overloads and underloads intermingled in a loading sequence, it could be relatively easy to establish a crack growth curve by means of a cycle-by-cycle integration. However, load-spectrum effects largely complicate a crack growth under variable-amplitude cycling. In this paper, fatigue crack growth behaviour of aeronautical aluminium alloy 2024-T3 was studied. Effects of various loading conditions such as stress ratio and amplitude loadings were investigated. In particular, the effect of different overloads on the fatigue crack growth was simulated using Zencrack code. Preliminary analyses on Compact Tension (CT) specimens proved that the numerical results generated were in agreement with the results provided by an afgrow code for the same conditions. A case study was carried out on a helicopter component, undergoing repeated overloads, to compare numerical results obtained implementing yield zone models in Zencrack.
    • Condition parameter estimation for photovoltaic buck converters based on adaptive model observers

      Cen, Zhaohui; Stewart, Paul; Derby University (IEEE, 2016-10-31)
      DC-DC power converters such as buck converters are susceptible to degradation and failure due to operating under conditions of electrical stress and variable power sources in power conversion applications, such as electric vehicles and renewable energy. Some key components such as electrolytic capacitors degrade over time due to evaporation of the electrolyte. In this paper, a model-observer based scheme is proposed to monitor the states of Buck converters and to estimate their component parameters, such as capacitance and inductance. First, a diagnosis observer is proposed, and the generated residual vectors are applied for fault detection and isolation. Second, component condition parameters, such as capacitance and inductance are reconstructed using another novel observer with adaptive feedback law. Additionally, the observer structures and their theoretical performance are analyzed and proven. In contrast to existing reliability approaches applied in buck converters, the proposed scheme performs online-estimation for key parameters. Finally, buck converters in conventional dc–dc step-down and photovoltaic applications are investigated to test and validate the effectiveness of the proposed scheme in both simulation and laboratory experiments. Results demonstrate the feasibility, performance, and superiority of the proposed component parameter estimation scheme.
    • Toward a more realistic, cost-effective, and greener ground movement through active routing: A multiobjective shortest path approach

      Chen, Jun; Atkin, Jason A. D.; Locatelli, Giorgio; Weiszer, Michal; Ravizza, Stefan; Stewart, Paul; Burke, Edmund K.; University of Derby (IEEE, 2016-10-31)
      This paper draws upon earlier work, which devel- oped a multiobjective speed profile generation framework for unimpeded taxiing aircraft. Here, we deal with how to seamlessly integrate such efficient speed profiles into a holistic decision- making framework. The availability of a set of nondominated unimpeded speed profiles for each taxiway segment, with respect to conflicting objectives, has the potential to significantly impact upon airport ground movement research. More specifically, the routing and scheduling function that was previously based on distance, emphasizing time efficiency, could now be based on richer information embedded within speed profiles, such as the taxiing times along segments, the corresponding fuel consumption, and the associated economic implications. The economic implica- tions are exploited over a day of operation, to take into account cost differences between busier and quieter times of the airport. Therefore, a more cost-effective and tailored decision can be made, respecting the environmental impact. Preliminary results based on the proposed approach show a 9%–50% reduction in time and fuel respectively for two international airports: Zurich and Manchester. The study also suggests that, if the average power setting during the acceleration phase could be lifted from the level suggested by the International Civil Aviation Organization, ground operations may simultaneously improve both time and fuel efficiency. The work described in this paper aims to open up the possibility to move away from the conventional distance-based routing and scheduling to a more comprehensive framework, capturing the multifaceted needs of all stakeholders involved in airport ground operations.