Browsing by Author "Morris, Alan J."
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Item Open Access Analytical wing weight prediction/estimation using computer based design techniques(Cranfield University, 1987) Murphy, N. A. D.; Morris, Alan J.Item Open Access Desaid : the development of an expert system for aircraft initial design(Cranfield University, 1991-07-25) Nah, Seung-Hyeog; Morris, Alan J.As all engineering works are a blend of theory and empiricism, aircraft design, by its nature, represents a mixture of aircraft designer's knowledge obtained from aeronautical engineering disciplines and its usage combined with his experience. This means not only the application but also the integration of all the fundamental knowledge of aerodynamics, structure, propulsion, stability and control, operational and economic aspects, etc., based upon the designer's judgements and experiences. Thus the tasks involved in designing an aircraft configuration, without exception, show complex characteristics, considering the fact that aircraft configuration design means the integration of components such as lifting surfaces ( wing ), fuselage, power-plant, control surfaces ( tail or canard ), and undercarriage. The discrepancies and mismatches among the aircraft components make the configuration design iterative, repetitive, and thus time - consuming. Such complexities of configuration design processes often require compromise, through trial and error, to resolve conflicts between the major design areas. Moreover, it takes tens of years to become a experienced design expert whose sound judgement, based upon experience and profound knowledge, influences greatly the aircraft configuration design. The differences in judgements depend upon the designers' imagination and experience, and they are the cause of variations in aircraft configurations. Therefore, the efforts were made to overcome those difficulties which hinder the aircraft designer from making the task of configuration design more efficient, and further to assist the aircraft designer in getting an easy and interactive preliminary aircraft configuration without always relying upon design experts. Hence the current research project is directed at the development of an expert system for aircraft design. This involves the use of Artificial Intelligence and its programming language called PROLOG ( PROgramming in LOGic ). The research started from a thorough analysis of the major component design areas and has constructed an EXPERT SYSTEM to find out the efficient Control Mechanism which can search intensively for the solutions to design problems for all types of aircraft; civil and military, subsonic and supersonic, conventional and unconventional, etc. In addition, users can have access to the explanations of important items such as a design process, terminology, equations, and results. The explanation facility is one of the most important functions of Expert Systems. Partly due to the limit of computer capacity and partly due to the magnitude of laborious program execution at this stage, the system implementation has focused on the high - subsonic, conventional and jet transport aircraft categories. The approach taken was to find an efficient and effective control mechanism ( i. e. an Inference Engine ), which integrated the PARAMETRIC STUDY, WING DESIGN, FUSELAGE DESIGN, ENGINE DESIGN, TAIL DESIGN, UNDERCARRIAGE DESIGN, WEIGHT ANALYSIS AND COST ANALYSIS into a whole configuration system. The comparison between Expert System results and existing aircraft such as Boeing 747, Airbus 300 series, BAe 146 series, McDonnell Douglas MD series, etc., showed the permissible ranges of error to be within about 10 %. Such results enable the Expert System to claim that it can act as a useful design tool for the aircraft designer in the initial stage of aircraft configuration design. Finally, the author believes that the control mechanism devised for this Expert System can be used as a sound basis for extending the Expert System to include other types of aircraft and further to encompass spacecraft design, as the designer wishes.Item Open Access Development of an aircraft design expert system(Cranfield University, 1988-04) Alsina, J.; Morris, Alan J.The aircraft design process is characterised by the application of a wide range of knowledge across many disciplines based upon a certain degree of judgement and experience of the designer. A two pass approach has been taken towards the development of an aircraft design expert system based on the requirements of two conceptually different design steps namely, wing design and aircraft configuration. The current status of the work is one where an actual program for wing design exists with supporting documentation, and a very effective examination of the knowledge base performed based on the detail investigation of overall aircraft design process with particular emphasis on the wing design and the aircraft configuration design steps. The approach taken accomplishes the objectives of the current research in defining the knowledge base, providing tools and specifications for tools to be used within an aircraft design expert system closely following the problem-solving techniques utilised by the design expert.Item Open Access Error control in finite elements for fluid modelling.(Cranfield University, 1997-10) Onomor, E.M.; Morris, Alan J.The main objective of this thesis was to ascertain and to catalogue the possible sources of errors in the finite element method when used for fluid modelling. Some of these errors are inherent in the finite element method whilst others are introduced by the user when performing a fluid mechanical analysis. This thesis distinguishes from the two and provides where possible, ways of preventing or controlling them. The form is based on the SAFESA Technical manual, which is an equivalent for structural analyses. Focus is then made, as an example, on a real world problem; "The Backward Facing Step" where, based on experimental data an element sensitivity analysis is performed within ANSYS/FLOTRAN. This analysis attempts to determine the magnitude of errors associated with prescribed element distortions in relation to aspect ratio, skew angle and taper ratio. The results contained within are in the form of graphical velocity profile plots, contour plots and tables at the varying distortions. The results show a strong deviation from the control mesh as the distortion is increased.Item Open Access Evaluating the impact of knowledge-based CAD on aerostructural design(Cranfield University, 1998-01) Bates, J. P.; Morris, Alan J.Knowledge based enhancements to CAD systems are currently being offered as a means of furthering designer performance in the product development process. A considerable body of research has already taken place to define how such systems work and further options are currently being explored to build on achievements to date. However, the uptake of such systems in industrial practice is not widespread and assessment of such systems are not well documented in the literature. The present work first reviews current CAD practice as 'computer-aided drafting' and highlights the limitations and difficulties associated with the continued exclusive use of such systems in design. The need for proper uptake of knowledge-based CAD systems is then described, demonstrated and assessed. This thesis considers some of the difficulties associated with introducing knowledge based CAD systems onto the critical path of engineering programmes and sets out to evaluate the performance of one such system in the context of a live aircraft development project. The commercially available /knowledge-based engineering ÄUKBE) system ICAD from Concentra Ltd is selected for assessment in the context of aero structural design. A case study demonstrator is developed to automate the solid modelling of light alloy fuselage frame sectors and applied in practical design trials to determine its performance against well understood conventional CAD system expectations. The major contribution of the thesis is in assessing the impact on working practice of introducing KBE systems into the aircraft design process. The business benefits of using KBE systems in an aerospace engineering programme are quantified. Some ideas for the extended functionality of such systems to achieve a greater level of generic applicability are presented and implications of use of such systems discussed. Finally, recommendations for the extended deployment of KBE systems to achieve strategic market advantage in an aerospace context are given.Item Open Access Expert System for Structural Optimization Exploiting Past Experience and A-priori Knowledge.(Cranfield University, 1994-11) Kuntjoro, Wahyu; Morris, Alan J.The availability of comprehensive Structural Optimization Systems in the market is allowing designers direct access to software tools previously the domain of the specialist. The use of Structural Optimization is particularly troublesome requiring knowledge of finite element analysis, numerical optimization algorithms, and the overall design environment. The subject of the research is the application of Expert System methodologies to support nonspecialists when using a Structural Optimization System. The specific target is to produce an Expert System as an adviser for a working structural optimization system. Three types of knowledge are required to use optimization systems effectively; that relating to setting up the structural optimization problem which is based on logical deduction; past, experience; together with run-time and results interpretation knowledge. A knowledge base which is based on the above is set, up and reasoning mechanisms incorporating case based and rule based reasoning, theory of certainty, and an object oriented approach are developed. The Expert SVstem described here concentrates on the optimization formulation aspects. It is able to set up an optimization run for the user and monitor the run-time performance. In this second mode the system is able to decide if an optimization run is likely to converge to a, solution and advice the user accordingly. The ideas and Expert System techniques presented in this thesis have been implemented in the development; of a prototype system written in C++. The prototype has been extended through the development of a user interface which is based on XView.Item Open Access Finite element model updating in structural dynamics using design sensitivity and optimisation(Cranfield University, 1998-10) Calvi, Adriano; Morris, Alan J.Model updating is an important issue in engineering. In fact a well-correlated model provides for accurate evaluation of the structure loads and responses. The main objectives of the study were to exploit available optimisation programs to create an error localisation and updating procedure of nite element models that minimises the "error" between experimental and analytical modal data, addressing in particular the updating of large scale nite element models with severe requirements on the mode shapes correlation. A new methodology and procedure that allows the semi-automatic adjustment of a large nite element dynamic model of a structure to better represent the dynamic characteristics of an actual structure was developed. The key aspect of the procedure is a "two steps" optimisation process to achieve a complete correlation of the modal data. Eigenfrequency deviations and mode shapes cross-othogonality (CO) and/or modal assurance criterion (MAC) are used in the objective functions for the estimation problem of the updating parameters, that are the variables for tuning the analytical model. Theoretical aspects and practical implementation conceming CO and MAC, and their derivatives, have been fully developed and the advantages of using these mode correlation indices in the objective function have been largely commented. The selection of the updating parameters is a complex issue and can be still considered a partially open point. In the new procedure the suggested automated selection of the updating parameters by means of a preliminary calculation of the element modal strain energy and eigenvalue sensitivities is adequate for the reduction of the frequency deviations but could not be to improve the correlation indices of the mode shapes. The new procedure was successfully applied four times: to a cantilever beam model, the Garteur model, the Spacehab dynamic model and the Mini-Pressurised Logistics Module model. The last application was a real life application on a large scale structural mathematical model and in this case the procedure was mainly used for error localisation purposes. The developed procedure is robust, effective and efficient, thus the original objectives of the study were largely met.Item Open Access Intelligent Link Between Design, CAD and Structural Analysis(Cranfield University, 1998) Trebilcock, R. M.; Morris, Alan J.; Thompson, D.; Baker, J. C.This study outlines the requirement for a company to be able to manage its intellectual capital. On the basis of this requirement this study presents a new design methodology based around the requirements of the military aircraft industry. It tackles the difficult management problem of capturing, storing and re-using valuable company product knowledge. The detailed research documented in this thesis focuses on the conceptual design area of this methodology. Work in this area has resulted in the development of a further methodology for the conceptual design arena. This methodology is called the intelligent conceptual engineering system (ICES). The ICES methodology embraces the artificial intelligence disciplines of knowledge-based systems and case-based reasoning. Through the evolutionary development of the ICES methodology a significant contribution to knowledge has been made in three areas. Firstly, this study introduces a new method of assigning justifiable numerical weights to design drivers acting on the design process. Secondly, the work introduces the novel concept of using secondary rules in the knowledge-based system so a 'best structure' can be derived from the manufacturing and structures perspectives. Finally, this work adds a new concept to case-based reasoning called the 'jury technique'. These concepts, developed to support the ICES methodology have been placed in a prototype design decision support tool.Item Open Access Knowledge-based cost modelling for innovative design(Cranfield University, 2000) Rehman, S.; Guenov, Marin D.; Morris, Alan J.; Saggu, J.The contribution to new knowledge from this research is a novel method for modelling production costs throughout the design phase of a product's lifecycle, from conceptual to detail design. The provision of cost data throughout the design phase allows management to make more accurate bid estimates and encourages designers to design to cost, leading to a reduction in the amount of design rework and product's time to market. The cost modelling strategy adopted incorporates the use of knowledge-based and case-based approaches. Cost estimation is automated by linking design knowledge, required for predicting design features from incomplete design descriptions, to production knowledge. The link between the different paradigms is achieved through the blackboard framework of problem solving which incorporates both case-baseda nd rule-based reasoning. The method described is aimed at innovative design activities in which original designs are produced which are similar to some extent to past design solutions. The method is validated through a prototyping approach. Tests conducted on the prototype confirm that the designed method models costs sufficiently accurately within the range of its own knowledge base. It can therefore be inferred that the designed cost modelling methodology sets out a feasible approach to cost estimation throughout the design phase.Item Open Access An MDO concept for large civil airliner wings(Cranfield University, 1998-10) Gantois, K.; Morris, Alan J.This thesis investigates the application of Multi-Disciplinary Design, Anal- ysis and Optimisation to the design of a large civil airliner, similar in size as the future A3XX. For the first time structural optimisation, manufacturing cost and aerodynamic effects are simultaneously integrated within a realistic, complex aircraft design problem: the wing box of such a large airliner. A novel multi-level system was developed to incorporate structural effects and manufacturing cost: mass is treated at a top-level while costs are treated at a structural sub-level. It allows a designer to study cost changes with respect to design changes and the interaction of cost with other disciplines such as structures and aerodynamics. The flexibility of the system allows companies to import their own results or cost data and to perform cost studies based on historical data or highly novel processes. Structural optimisation of the wing box using MSc/NASTRAN and STARS, the development of a metal and composite cost model and the overall MDO methodology are being discussed.Item Open Access Multilevel optimum design of large laminated composite structures(1986-08) Watkins, R. I.; Morris, Alan J.A general method for the optimal design of large laminated composite structures, that allows full design variable (ply thickness and orientation) freedom, has been developed .. The number of variables and constraints, and hence the problem size, being dealt with at any given moment in the optimization process is kept within reasonable bounds by using a multilevel optimization scheme. The optimization process is split into a system level and an element level. At the system level the entire structure is considered and the individual laminae thicknesses (not ply angles) are sized so as to minimize the total structural weight within the constraints placed on the system. These constraints can include strain, displacement, buckling and gauge limits. Once the design has converged at this level the optimization process then switches to the element level. The objective function at the element level combines a weight function and a strain energy change function into a utility function which is minimized and in which the relative importance of each part is reflected by weighting coefficients. Minimizing the change in strain energy ensures load path continuity when switching between the two levels of optimization, and so decouples the problems at the two levels. Continuous lamina thickness and ply-angle variation is used to minimize the element level objective function while satisfying strain, buckling and gauge constraints. In this way optimum use is made of the material in each element, without changing the the load paths in the overall structure and thereby ensuring that the constraints at the system level are still satisfied. The procedure switches between the two levels until overall convergence has been achieved. Structures representative of straight, forward swept and delta wings are used to illustrate the effectiveness of the system and to show that the optimal designs produced are feasible and realistic, and compare favourably with designs obtained by more conventional and intuitive methods.Item Open Access Structural optimization of aircraft lifting surfaces to satisfy flutter requirements(Cranfield University, 1986-06) Souahi, A.; Morris, Alan J.The research reported in this thesis is concerned with the structural weight optimization of aircraft lifting surfaces when subjected to the satisfaction of flutter requirements. The main text is intended primarily as an expository account on the work and as such it aims at introducing and defining the subject of research and presenting the results. Accordingly, the mathematics have been simplified to the utmost in the main text and heavy theoretical treatments are revealed in the appendices. As the aim of this work is not directed at in-depth studies of the physical nature of flutter nor for a comprehensive treatment of structural optimization, the basic concepts of these two subjects are touched upon in the beginnings of chapters II and III respectively. We concluded these two chapters by clarifying the class of flutter, constraints and design variables for which the program we developed is designed. We endeavored to keep the problem to within certain practical boundaries without loosing too much of either its generality or its applicability to structures in realistic operational environments.