• Advances in control engineering

      Stewart, Paul; University of Derby (Multidisciplinary Digital Publishing Institute (MDPI), 2015-06-30)
      The last twenty years have seen a radical step-change in the capability and application of Control Engineering, brought about by advances in computational speed and capacity. Control design for contemporary, complex engineering systems has developed alongside Computer Aided Control System Design, powerful real-time embedded computation, and both off-line and on-line optimization techniques. This Special Issue will bring together papers, which particularly describe recent advances in Control Engineering in industrial applications and complex engineering systems, describing the application of novel theory across all areas of Automation. Papers which include practical experimental results are particularly encouraged, as are papers which set Control advances in the wider context of, for example, society, economics, energy and environment.
    • Aircraft taxi time prediction: Comparisons and insights

      Ravizza, Stefan; Chen, Jun; Atkin, Jason A. D.; Stewart, Paul; Burke, Edmund K.; University of Lincoln (Elsevier, 2014-01)
      The predicted growth in air transportation and the ambitious goal of the European Commission to have on-time performance of flights within 1 min makes efficient and predictable ground operations at airports indispensable. Accurately predicting taxi times of arrivals and departures serves as an important key task for runway sequencing, gate assignment and ground movement itself. This research tests different statistical regression approaches and also various regression methods which fall into the realm of soft computing to more accurately predict taxi times. Historic data from two major European airports is utilised for cross-validation. Detailed comparisons show that a TSK fuzzy rule-based system outperformed the other approaches in terms of prediction accuracy. Insights from this approach are then presented, focusing on the analysis of taxi-in times, which is rarely discussed in literature. The aim of this research is to unleash the power of soft computing methods, in particular fuzzy rule-based systems, for taxi time prediction problems. Moreover, we aim to show that, although these methods have only been recently applied to airport problems, they present promising and potential features for such problems.
    • Assessment of structural integrity of subsea wellhead system: analytical and numerical study

      Maligno, Angelo; Citarella, Roberto; Silberschmidt, Vadim V.; Soutis, Constantinos; University of Derby; University of Salerno; Loughborough University; University of Manchester (Italian Group of Fracture, 2015-01)
      Subsea wellhead systems exposed to severe fatigue loading are becoming increasingly a significant problem in offshore drilling operations due to their applications in wells with higher levels of pressure and temperature, situated at larger depths and in harsher environments. This has led to a substantial increase in the weight and size of offshore equipment, which, in combination with different loading conditions related to the environmental factors acting on the vessel and riser, has greatly increased the loads acting on subsea well systems. In particular, severe fatigue loading acting on the subsea wellhead system was detected. For this reason, a combined analytical and numerical study investigating the critical effect of crack depth on the overall structural integrity of subsea wellhead systems under cyclic loading was carried out. The study is based on a Linear Elastic Fracture Mechanics (LEFM) approach.
    • Commutation of permanent-magnet synchronous AC motors for military and traction applications

      Stewart, Paul; Kadirkamanathan, Visakan; University of Sheffield (Institute of Electrical and Electronic Engineers, 2003-06-05)
      The permanent-magnet ac (PMAC) motor requires accurate position information to be supplied to the controller so that the applied currents can be modulated in synchronism with the rotor. In the flux-weakening region of operation, accurate rotor position information is critical to control the relative phase of the applied stator voltages. The design of controllers, which can operate without direct position feedback, have been the subject of intense development. The most commonly cited justifications for the elimination of the absolute position encoder are those of cost, and the reduction of the overall dimensions of the motor. However, certain military specifications apply stringent constraints to the use of both sensors and estimation techniques. Absolute encoders are frequently prohibited for applications such as tank turret drives due to their relatively fragile nature. Fully sensorless operation has been the focus of development for all classes of electric motors, but again is precluded not only in certain military applications, but also in traction applications for a number of manufacturers.
    • Comparison of two novel MRAS based strategies for identifying parameters in permanent magnet synchronous motors.

      Liu, Kan; Zhang, Qiao; Zhu, Zi-Qiang; Zhang, Jing; Shen, An-Wen; Stewart, Paul; University of Lincoln UK (Springer., 2010-11-11)
      Two Model Reference Adaptive System (MRAS) estimators are developed for identifying the parameters of permanent magnet synchronous motors (PMSM) based on Lyapunov stability theorem and Popov stability criterion, respectively. The proposed estimators only need online detection of currents, voltages and rotor rotation speed, and are effective in the estimation of stator resistance, inductance and rotor flux-linkage simultaneously. Their performances are compared and verified through simulations and experiments. It shows that the two estimators are simple and have good robustness against parameter variation and are accurate in parameter tracking. However, the estimator based on Popov stability criterion, which can overcome the parameter variation in a practical system, is superior in terms of response speed and convergence speed since there are both proportional and integral units in the estimator in contrast to only one integral unit in the estimator based on Lyapunov stability theorem. In addition, there is no need of the expert experience which is required in designing a Lyapunov function
    • A computational strategy for damage-tolerant design of hollow shafts under mixed-mode loading condition.

      Lepore, Marcello Antonio; Yarullin, Rustam; Maligno, Angelo Rosario; 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.
    • 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.
    • A controlled migration genetic algorithm operator for hardware-in-the-loop experimentation

      Gladwin, Daniel; Stewart, Paul; Stewart, Jill; University of Sheffield (International Federation of Automatic Control, 2011-06)
      In this paper, we describe the development of an extended migration operator, which combats the negative effects of noise on the effective search capabilities of genetic algorithms. The research is motivated by the need to minimize the num-ber of evaluations during hardware-in-the-loop experimentation, which can carry a significant cost penalty in terms of time or financial expense. The authors build on previous research, where convergence for search methods such as Simulated Annealing and Variable Neighbourhood search was accelerated by the implementation of an adaptive decision support operator. This methodology was found to be effective in searching noisy data surfaces. Providing that noise is not too significant, Genetic Al-gorithms can prove even more effective guiding experimentation. It will be shown that with the introduction of a Controlled Migration operator into the GA heuristic, data, which repre-sents a significant signal-to-noise ratio, can be searched with significant beneficial effects on the efficiency of hardware-in-the-loop experimentation, without a priori parameter tuning. The method is tested on an engine-in-the-loop experimental example, and shown to bring significant performance benefits.
    • 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.
    • Design of robust fuzzy-logic control systems by multi-objective evolutionary methods with hardware in the loop.

      Stewart, Paul; Stone, David; Fleming, Peter; University of Sheffield (Elsevier, 2004-05-10)
      Evolutionary development of a fuzzy-logic controller is described and is evaluated in the context of hardware in the loop. It had been found previously that a robust speed controller could be designed for a DC motor motion control platform via off-line fuzzy logic controller design. However to achieve the desired performance, the controller required manual tuning on-line. This paper investigates the automatic design of a fuzzy logic controller directly onto hardware. An optimiser which modifies the fuzzy membership functions, rule base and defuzzification algorithms is considered. A multi-objective evolutionary algorithm is applied to the task of controller development, while an objective function ranks the system response to find the Pareto-optimal set of controllers. Disturbances are introduced during each evaluation at run-time in order to produce robust performance. The performance of the controller is compared experimentally with the fuzzy logic controller which has been designed off-line, and a standard PID controller which has been tuned online. The on-line optimised fuzzy controller is shown to be robust, possessing excellent steady-state and dynamic characteristics, demonstrating the performance possibilities of this type of approach to controller design.
    • Dynamic model reference PI control of permanent magnet AC motor drives

      Stewart, Paul; Kadirkamanathan, Visakan; University of Sheffield (Elsevier, 2001-11)
      The permanent magnet AC motor drive (PMAC) is a multivariable, non-linear, closely coupled system subject to saturation due to finite DC supply voltage and hard current limits for protection of the drive hardware. Model following controls can be applied to this class of motor with PI current controllers enabling tracking of quadrature current command values. The presence of a finite supply voltage constraint results in reduced system performance when the current regulators saturate. A dynamic model reference controller is presented which includes the currents and voltage limits, constraining the magnitude of the command signals, operating the system to just within the bound of saturation, allowing the PI controllers to accurately track the commanded values and retain control of the current vectors. This regime ensures maximum possible dynamic performance of the system. The system and controller is simulated and experimentally verified, controller gain being found by Monte Carlo simulation.
    • Dynamic model tracking design for low inertia, high speed permanent magnet ac motors

      Stewart, Paul; Kadirkamanathan, Visakan; University of Sheffield (Elsevier, 2007-01-17)
      Permanent magnet ac (PMAC) motors have existed in various configurations for many years. The advent of rare-earth magnets and their associated highly elevated levels of magnetic flux makes the permanent magnet motor attractive for many high performance applications from computer disk drives to all electric racing cars. The use of batteries as a prime storage element carries a cost penalty in terms of the unladen weight of the vehicle. Minimizing this cost function requires the minimum electric motor size and weight to be specified, while still retaining acceptable levels of output torque. This tradeoff can be achieved by applying a technique known as flux weakening which will be investigated in this paper. The technique allows the speed range of a PMAC motor to be greatly increased, giving a constant power range of more than 4:1. A dynamic model reference controller is presented which has advantages in ease of implementation, and is particularly suited to dynamic low inertia applications such as clutchless gear changing in high performance electric vehicles. The benefits of this approach are to maximize the torque speed envelope of the motor, particularly advantageous when considering low inertia operation. The controller is examined experimentally, confirming the predicted performance.
    • Electrical power and energy systems for transportation applications

      Stewart, Paul; Bingham, Chris; University of Derby (Multidisciplinary Digital Publishing Institute (MDPI), 2016-07-14)
      This book contains the successful invited submissions [1-25] to a Special Issue of Energies on the subject area of “Electrical Power and Energy Systems for Transportation Applications�.
    • Energy harvesting and power network architectures for the multibody advanced airship for transport high altitude cruiser-feeder airship concept

      Smith, Tim; Bingham, Chris; Stewart, Paul; Allarton, R.; Stewart, Jill; University of Lincoln (Institution of Mechanical Engineers, 2013-01-09)
      This article presents results of preliminary investigations in the development of a new class of airship. Specific focus is given to photo-electric harvesting as a primary energy source, power architectures and energy audits for life support, propulsion and ancillary loads to support the continuous daily operation of the primary airship (cruiser) at stratospheric altitudes (similar to 15 km). The results are being used to drive the requirements of the FP7 multibody advanced airship for transport programme, which is to globally transport both passengers and freight using a 'feeder-cruiser' concept. It is shown that there is a potential trade off to traditional cost and size limits and, although potentially very complex, a first-order approximation is used to demonstrate sensitivities to the economics of the lifting gas. This presented concept is substantially different to those of conventional aircraft due to the airship size and the inherent requirement to harvest and store sufficient energy during 'daylight' operation to guarantee safe operation during 'dark hours'. This is particularly apparent when the sizing of the proposed electrolyser is considered, as its size and mass increases nonlinearly with decreasing daylight duty. The study also considers the integration of photovoltaics with various electrical architectures, in safety critical environments. A mass audit is also included that shows that if the electrolyser was omitted in such systems, the overall impact will be small compared to structural and propulsion masses. It should be noted that although the technology bias is application specific, the underlying principles are much widely applicable to other energy harvesting and power management sectors.
    • 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.
    • 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.
    • FEM simulation of a crack propagation in a round bar under combined tension and torsion fatigue loading

      Citarella, Roberto; Maligno, Angelo; Shlyannikov, Valery; University of Salerno; University of Derby; Russian Academy of Sciences (Italian Group of Fracture, 2015-01)
      An edge crack propagation in a steel bar of circular cross-section undergoing multiaxial fatigue loads is simulated by Finite Element Method (FEM). The variation of crack growth behaviour is studied under axial and combined in phase axial+torsional fatigue loading. Results show that the cyclic Mode III loading superimposed on the cyclic Mode I leads to a fatigue life reduction. Numerical calculations are performed using the FEM software ZENCRACK to determine the crack path and fatigue life. The FEM numerical predictions have been compared against corresponding experimental and numerical data, available from literature, getting satisfactory consistency
    • Generator voltage stabilisation for series-hybrid electric vehicles.

      Stewart, P.; Gladwin, D.; Stewart, J.; Cowley, R.; University of Sheffield (Elsevier, 2008-02-11)
      This paper presents a controller for use in speed control of an internal combustion engine for series-hybrid electric vehicle applications. Particular reference is made to the stability of the rectified DC link voltage under load disturbance. In the system under consideration, the primary power source is a four-cylinder normally aspirated gasoline internal combustion engine, which is mechanically coupled to a three-phase permanent magnet AC generator. The generated AC voltage is subsequently rectified to supply a lead-acid battery, and permanent magnet traction motors via three-phase full bridge power electronic inverters. Two complementary performance objectives exist. Firstly to maintain the internal combustion engine at its optimal operating point, and secondly to supply a stable 42 V supply to the traction drive inverters. Achievement of these goals minimises the transient energy storage requirements at the DC link, with a consequent reduction in both weight and cost. These objectives imply constant velocity operation of the internal combustion engine under external load disturbances and changes in both operating conditions and vehicle speed set-points. An electronically operated throttle allows closed loop engine velocity control. System time delays and nonlinearities render closed loop control design extremely problematic. A model-based controller is designed and shown to be effective in controlling the DC link voltage, resulting in the well-conditioned operation of the hybrid vehicle.
    • Heating apparathus and method

      Hall, Frank Richard; Spence, Peter Julian; Kenward, Christopher A.; University of Derby (Intellectual Property Office, 2012-09-05)
      This invention relates and apparatus arranged to locally heat, perhaps rapidly, a work-piece and associated methods. In particular the invention relates to the heating of a conductive work-piece. In particular, but not exclusively, the invention relates to an apparatus and method arranged to rapidly perform diffusion bonding at one or more localised regions of the work-piece. In particular, but not exclusively, this invention relates to an apparatus arranged to rapidly join sheets of metal and/or metal alloys at one or more localised regions using diffusion bonding. The apparatus may also relate to a testing apparatus and method.
    • Improved decision support for engine-in-the-loop experimental design optimization.

      Gladwin, D; Stewart, P; Stewart, J; Chen, R; Winward, E; University of Sheffield; University of Lincoln.; Loughborough university (Sage., 2009-09-25)
      Experimental optimization with hardware in the loop is a common procedure in engineering and has been the subject of intense development, particularly when it is applied to relatively complex combinatorial systems that are not completely understood, or where accurate modelling is not possible owing to the dimensions of the search space. A common source of difficulty arises because of the level of noise associated with experimental measurements, a combination of limited instrument precision, and extraneous factors. When a series of experiments is conducted to search for a combination of input parameters that results in a minimum or maximum response, under the imposition of noise, the underlying shape of the function being optimized can become very difficult to discern or even lost. A common methodology to support experimental search for optimal or suboptimal values is to use one of the many gradient descent methods. However, even sophisticated and proven methodologies, such as simulated annealing, can be significantly challenged in the presence of noise, since approximating the gradient at any point becomes highly unreliable. Often, experiments are accepted as a result of random noise which should be rejected, and vice versa. This is also true for other sampling techniques, including tabu and evolutionary algorithms. After the general introduction, this paper is divided into two main sections (sections 2 and 3), which are followed by the conclusion. Section 2 introduces a decision support methodology based upon response surfaces, which supplements experimental management based on a variable neighbourhood search and is shown to be highly effective in directing experiments in the presence of a significant signal-to-noise ratio and complex combinatorial functions. The methodology is developed on a three-dimensional surface with multiple local minima, a large basin of attraction, and a high signal-to-noise ratio. In section 2, the methodology is applied to an automotive combinatorial search in the laboratory, on a real-time engine-in-the-loop application. In this application, it is desired to find the maximum power output of an experimental single-cylinder spark ignition engine operating under a quasi-constant-volume operating regime. Under this regime, the piston is slowed at top dead centre to achieve combustion in close to constant volume conditions. As part of the further development of the engine to incorporate a linear generator to investigate free-piston operation, it is necessary to perform a series of experiments with combinatorial parameters. The objective is to identify the maximum power point in the least number of experiments in order to minimize costs. This test programme provides peak power data in order to achieve optimal electrical machine design. The decision support methodology is combined with standard optimization and search methods — namely gradient descent and simulated annealing— in order to study the reductions possible in experimental iterations. It is shown that the decision support methodology significantly reduces the number of experiments necessary to find the maximum power solution and thus offers a potentially significant cost saving to hardware-in-the-loop experimentation.