Hall, Frank Richard; Spence, Peter Julian; Kenward, Christopher A. (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.
Wrigley, P.A.; Wood, P.; Stewart, Paul; Robertson, D. (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.
Stewart, Paul; Stone, David; Fleming, Peter (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.
Maligno, Angelo; Citarella, Roberto; Silberschmidt, Vadim V.; Soutis, Constantinos (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.
Use of cold tooling is beneficial in the sheet metal forming. This paper presents simulations of the process with the objective of investigating issues associated with thermal management, and of providing thermo-mechanical data for future research.
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.
Stewart, P.; Gladwin, D.; Stewart, J.; Cowley, R. (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.
Stewart, P; Gladwin, D; Parr, M; Stewart, J (2009-11-05)
In this article, the multi-objective design of a fuzzy logic augmented flight controller for a high performance fighter jet (the Lockheed-Martin F16) is described. A fuzzy logic controller is designed and its membership functions tuned by genetic algorithms in order to design a roll, pitch, and yaw flight controller with enhanced manoeuverability which still retains safety critical operation when combined with a standard inner-loop stabilizing controller. The controller is assessed in terms of pilot effort and thus reduction of pilot fatigue. The controller is incorporated into a six degree of freedom motion base real-time flight simulator, and flight tested by a qualified pilot instructor.
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
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.
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