This paper presents a multidisciplinary design optimization framework applied to the development of unmanned aerial vehicles with a focus on radar signature and sensor performance requirements while simultaneously considering the flight trajectory. The primary emphasis herein is on the integration and development of analysis models for the calculation of the radar cross section and sensor detection probability, whereas traditional aeronautical disciplines such as aerodynamics and mission simulation are also taken into account in order to ensure a flyable concept. Furthermore, this work explores the effect of implementing trajectory constraints as a supplementary input to the multidisciplinary design optimization process and presents a method that enables the optimization of the aircraft under a three-dimensional flight scenario. To cope with the additional computational cost of the high-fidelity radar cross section and sensor calculations, the use of metamodels is also investigated and an efficient development methodology that can provide high-accuracy approximations for this particular problem is proposed. Overall, the operation and performance of the framework are evaluated against five surveillance scenarios, and the obtained results show that the implementation of trajectory constraints in the optimization has the potential to yield better designs by 12–25% when compared to the more “traditional” problem formulations.

This paper explores the use of Multidisciplinary Design Optimization (MDO) in the development of Unmanned Aerial Vehicles (UAVs) when the requirements include a collaboration in a System of Systems (SoS) environment. In this work, the framework considers models that can capture the mission, stealth, and surveillance performance of each aircraft, while at the same time, a dedicated simulation module assesses the total cooperation effect on a given operational scenario. The resulting mixed continuous and integer variable problem is decomposed with a multi-level architecture, and in particular, it is treated as a fleet allocation problem that includes a nested optimization routine for sizing a “yet-to-be-designed” aircraft. Overall, the models and the framework are evaluated through a series of optimization runs, and the obtained Pareto front is compared with the results from a traditional aircraft mission planning method in order to illustrate the benefits of this SoS approach in the design of UAVs.

Contemporary aircraft design and development incurs high costs and consumes a lot of time for research and implementation. To minimize the development cost, an improvement of the conceptual design phase is desirable. A framework to support the initial design space exploration and conceptual design phase is presently being developed at Linköping University. In the aircraft design, the geometry carries a critical, discriminating role since it stores a significant part of the information and the data needed for most investigations. Methodology for design automation of a wing with a detailed description such that the geometry is effectively propagated for further analysis is presented in this paper. Initial weight estimation of the wing is performed by combining the weight penalty method with a sophisticated CAD model. This wing model is used for airfoil shape optimization and later for structural optimization. A methodology for automatic meshing of the geometry for CFD and FEM when the surfaces increase or decrease during the design automation is proposed. The framework combining automation capability with shape and structural optimization will enhance the early design phases of aircraft conceptual design.

Aircraft design is an inherently multidisciplinary activity that requires integrating different models and tools to reach a well-balanced and optimized product. At Linköping University a design framework is being developed to support the initial design space exploration and the conceptual design phase. Main characteristics of the framework are its flexible database in XML format, together with close integration of automated CAD and other tools, which allows the developed geometry to be directly used in the subsequent preliminary design phase. In particular, the aim of the proposed work is to test the framework by designing, optimizing and studying a transport aircraft wing with respect to aerodynamic, geometry, structural and accessability constraints. The project will provide an initial assessment of the capability of the framework, both in terms of processing speed and accuracy of the results.

This paper explores novel methodologies for enabling Multidisciplinary Design Optimization (MDO) of complex engineering products. To realize MDO, Knowledge Based Engineering (KBE) is adopted with the aim of achieving design reuse and automation. The aim of the on-going research at Linköping University is to shift from manual modelling of disposable geometries to Computer Aided Design (CAD) automation by introducing generic high-level geometry templates. Instead of repeatedly modelling similar instances of objects, engineers should be able to create more general models that can represent entire classes of objects. The proposed methodology enables utilization of commercial design tools, hence taking industrial feasibility into consideration. High Level CAD templates (HLCt) will be proposed and discussed as the building blocks of flexible and robust CAD models, which in turn enables high-fidelity geometry in the MDO loop. Quantification of the terms flexibility and robustness is also presented, providing a means to measure the quality of the geometry models. Finally, application examples are presented in which the outlined framework is evaluated. The applications have been chosen from three ongoing research projects aimed at automating the design of transport aircraft, industrial robots, and micro air vehicles.

Product development processes are continuously challenged by demands for increased efficiency. As engineering products become more and more complex, efficient tools and methods for integrated and automated design are needed throughout the development process. Multidisciplinary Design Optimization (MDO) is one promising technique that has the potential to drastically improve concurrent design. MDO frameworks combine several disciplinary models with the aim of gaining a holistic perspective of a system, while capturing the synergies between different subsystems. Among all disciplines, the geometric model is recognized as playing a key role, because it collects most of the data required to any other disciplinary analysis. In the present thesis, methodologies to enable multidisciplinary optimization in early aircraft design phases are studied. In particular, the research aims at putting the CAD geometric model in the loop. This requires the ability to automatically generate or update the geometric model, here referred to as geometry-based design automation.

The thesis proposes the use of Knowledge Based Engineering (KBE) techniques to achieve design reuse and automation. In particular, so called High Level CAD templates (HLCts) are suggested to automate geometry generation and updates. HLCts can be compared to parametric LEGO® blocks containing a set of design and analysis parameters. These are produced and stored in libraries, giving engineers or a computer agent the possibility to first topologically select the templates and then modify the shape of each template parametrically.

Since parameterization is central to modelling by means of HLCts, a thorough analysis of the subject is also performed. In most of the literature on MDO and KBE two recurring requirements concerning the geometrical model are expressed: the model should be flexible and robust. However, these requirements have never been properly formulated or defined. Hence, in the thesis a mathematical formulation for geometry model robustness and flexibility are proposed. These formulations ultimately allow the performance of geometric models to be precisely measured and compared.

Finally, a prototyping and validation process is presented. The aim is to quickly and cost-effectively validate analytical results from an MDO process. The proposed process adopts different manufacturing techniques depending on the size and purpose of the intended prototype. In the last part of the thesis, three application examples are presented. The examples are chosen from research projects that have been carried out at Linköping University and show how the proposed theoretical results have been successfully employed in practice.

Kraven på ökad effektivitet utmanar ständigt  produktutvecklingsprocessen. I och med att ingenjörsprodukter blir allt mer komplexa, växer genom hela utvecklingsprocessen behovet av verktyg och metoder för integrerad och automatiserad design. Multidisciplinär Design Optimering (MDO) är en lovande teknik som kan drastiskt förbättra parallell design. I ett MDO ramverk är flera disciplinära modeller sammankopplade för att uppnå ett holistiskt systemperspektiv, men där synergierna mellan olika delsystem också kan fångas upp. Bland alla möjliga discipliner spelar geometrimodellen en central roll, eftersom den innefattar en stor del av all information som är nödvändig för andra disciplinära analyser.

I avhandlingen studeras ett flertal metoder för att möjliggöra multidisciplinär optimering i de tidigaste faserna av flygplansdesign. I synnerlighet är forskningen riktad mot att införa geometriska CAD modeller i designloopen. Det blir därmed nödvändigt att kunna automatiskt generera eller uppdatera geometriska modeller, vilket i avhandlingen kallas för ”geometribaserad design automation”.

Avhandlingen förordar att Knowledge Based Engineering (KBE) tekniker används för att konstruktioner skall kunna automatiseras och återanvändas. Så kallade Hög Nivå CAD mallar (på engelska High Level CAD templates – HLCts) föreslås för att automatiskt generera och uppdatera geometrimodeller. HLCts kan jämföras med parametriska LEGO® klossar som innehåller variabler för design och analys. Mallarna kan samlas i bibliotek; därefter har konstruktörer eller dator agenter möjligheten att först topologiskt välja en mall och sedan ändra på dess utförande genom utvalda parametrar.

Eftersom parameterisering är ett centralt begrepp för HLCt principen, föreslås även en fördjupad analys av ämnet. I stor del av MDO och KBE litteraturen ställs det två återkommande krav på geometrimodellen: modellen bör vara flexibel och robust. Eftersom dessa krav aldrig har getts en formell formulering, förordas i avhandlingen en matematisk beskrivning av modellrobusthet och - flexibilitet. Tack vore formuleringen är det möjligt att noggrant mäta och jämföra till vilken grad geometriska modeller fungerar.

Slutligen presenteras en valideringsprocess baserad på kostnadseffektiva prototyper som används för att snabbt bekräfta analytiska resultat från MDO ramverket. Den föreslagna processen nyttjar olika tillverkningsmetoder, beroende på prototypens tänkta storlek och användning. I sista delen av avhandlingen presenteras även tre applikationsexempel, valda från forskningsprojekt som har bedrivits på Linköpings universitet och som visar hur de teoretiska resultaten har kommit till användning i praktiken.

This paper presents the development of a design framework for the initial conceptual design phase. The focus in this project is on a flexible database in XML format, together with close integration of automated CAD, and other tools, which allows the developed geometry to be used directly in the subsequent preliminary design phase. The database and the geometry are also described and an overview is given of included tools like aerodynamic analysis and weight estimation.

Purpose - The purpose of this paper is to present the latest subscale demonstrator aircraft developed at Linkoping University. It has been built as part of a study initiated by the Swedish Material Board (FMV) on a Generic Future Fighter aircraft. The paper will cover different aspects of the performed work: from paper study realised by SAAB to the first flight of the scaled demonstrator. The intention of the paper is to describe what has been realised and explain how the work is may be used to fit within aircraft conceptual design. Design/methodology/approach - The approach has been to address the challenges proposed by the customer of the demonstrator, how to design, manufacture and operate a scaled demonstrator of an aircraft study in conceptual design within five months. Similar research projects have been reviewed in order to perform the current work. Findings - The results obtained so far have led to new questions. In particular, the project indicated that more research is needed within the area of subscale flight testing for usage in aircraft conceptual design, since a scaled demonstrator is likely to answer some questions but will probably open up new ones. Research limitations/implications - The current research is just in its infancy and does not bring any final conclusion but does, however, offer several guidelines for future works. Since the aircraft study was an early phase concept study, not much data are available for validation or comparison. Therefore, the paper is not presenting new methods or general conclusions. Practical implications - Results from a conceptual aircraft study and a realisation of a scaled prototype are presented, which show that scaled flight testing may be used with some restriction in conceptual design. Originality/value - The value of this paper is to show that universities can be involved in prototype development and can work in close collaboration with industries to address issues and solutions within aircraft conceptual design.

A methodology for an automated design and fabrication of micro-air vehicles (MAVs) is presented. A design optimization framework has been developed that interfaces several software systems to generate MAVs to optimally fulfil specific mission requirements. By means of amulti-objective genetic algorithm, families of MAVs are tailored with respect to objectives such as weight and endurance. The framework takes into consideration the airframe and aerodynamic design as well as the selection and positioning of internal components. The selection of propulsion system components is made from a database of off-the-shelf components. In combination with a three-dimensional printer, physical prototypes can be quickly manufactured. A validation of the framework results from flight tests of a real MAV is also presented.

A fundamental part of aircraft design involves the wing airfoil optimization, establishing an outer shape of the wing which has good aerodynamic performance, good internal volume distribution for fuel and systems and which also serves as an efficient structural member supporting the weight of the aircraft. As for all optimization tasks, the complexity of the problem is directly coupled to the parameterization of the geometry. Of highest relevance are the number of parameters and the number of additional constraints that are required to ensure valid modeling.This paper proposes a parameterization method for two dimensional airfoils, aimed at providing a wide design space, while at the same time keeping the number of parameters low. With 15 parameters defining the wing profile, many of the existing airfoils can be modeled with close tolerance.