Unmanned Aircraft Design. Mohammad Sadraey H.

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СКАЧАТЬ low cost. Every system is made up of components or subsystems, and any subsystem can be broken down into smaller components. For example, in an air transportation system, the UAV, terminal, ground support equipment, and controls are all subsystems. The UAV life-cycle is illustrated in Figure 1.3.

      A UAV must feature product competitiveness, otherwise, the producer and designer may not survive in the world marketplace. Product competitiveness is desired by UAV producers worldwide. Accordingly, the systems engineering challenge is to bring products and systems into being that meet the mission expectations cost-effectively. Because of intensifying international competition, UAV producers are seeking ways to gain sustainable competitive advantages in the marketplace.

      It is essential that UAV designers be sensitive to utilization outcomes during the early stages of UAV design and development. They also need to conduct life-cycle engineering as early as possible in the design process. Fundamental to the application of systems engineering is an understanding of the system life-cycle process illustrated in Figure 1.3. It must simultaneously embrace the life cycle of the manufacturing process, the life cycle of the maintenance and support capability, and the life cycle of the phase-out and disposal process.

      The requirements need for a specific new UAV first comes into focus during the conceptual design process. It is this recognition that initiates the UAV conceptual design process to meet these needs. Then, during the conceptual design of the UAV, consideration should simultaneously be given to its production and support. This gives rise to a parallel life cycle for bringing a manufacturing capability into being.

      Traditional UAV configuration design attempts to achieve improved performance and reduced operating costs by minimizing maximum takeoff weight. From the point of view of a UAV customer, however, this method does not guarantee the optimality of a UAV program. Multidisciplinary design optimization (MDO) is an important part of the UAV configuration design process. It first discusses the design parameters, constraints, objectives functions, and criteria and then UAV configuration classifications. Then the relationship between each major design option and the design requirements are evaluated. Then the systems engineering principals are presented. At the end, systems engineering approach is applied in the optimization of the UAV configuration design and a new configuration design optimization methodology is introduced.

      The design of a UAV within the system life-cycle context is different from the design just to meet a set of performance or stability requirements. Life-cycle focused design is simultaneously responsive to customer needs and to life-cycle outcomes. The design of the UAV should not only transform a need into a UAV/system configuration, but should ensure the UAV’s compatibility with related physical and functional requirements. Further, it should consider operational outcomes expressed as safety, producibility, affordability, reliability, maintainability, usability, supportability, serviceability, disposability, and others, as well as the requirements on performance, stability, control, and effectiveness.

      An essential technical activity within this process is that of evaluation. Evaluation must be inherent within the systems engineering process and must be invoked regularly as the system design activity progresses. However, systems evaluation should not proceed without guidance from customer requirements and specific system design criteria. When conducted with full recognition of design criteria, evaluation is the assurance of continuous design improvement. There are a number of phases through which the system design and development process must invariably pass. Foremost among them is the identification of the customer related need and, from that need, the determination of what the system is to do. This is followed by a feasibility analysis to discover potential technical solutions, the determination of system requirements, the design and development of system components, the construction of a prototype, and/or engineering model, and the validation of system design through test and evaluation. The system (e.g., UAV) design process includes four major phases: (1) Conceptual Design, (2) Preliminary Design, (3) Detail Design, and (4) Test and Evaluation. The four phases of the integrated design of a UAV are summarized in Figure 1.4. Sections 1.10–1.13 present the details of these design phases.

      Figure 1.4: Design process and formal design reviews.

      In the conceptual design phase, the UAV will be designed in concept without the precise calculations. In another word, almost all parameters are determined based on a decision making process and a selection technique. On the other hand, the preliminary design phase tends to employ the outcomes of a calculation procedure. As the name implies, in the preliminary design phase, the parameters that are determined are not final and will be altered later. In addition, in this phase, parameters are essential and will directly influence the entire detail design phase. Therefore the ultimate care must be taken to insure the accuracy of the results of the preliminary design phase. In the detail design phase, the technical parameters of all components (e.g., wing, fuselage, tail, landing gear (LG), and engine) including geometry are calculated and finalized.

1.10 CONCEPTUAL DESIGN

      Throughout the conceptual system design phase (commencing with the need analysis), one of the major objectives is to develop and define the specific design-to requirements for the system as an entry. The results from these activities are combined, integrated, and included in a system specification. This specification constitutes the top “technical-requirements” document that provides overall guidance for system design from the beginning. Conceptual design is the first and most important phase of the UAV system design and development process. It is an early and high-level life cycle activity with potential to establish, commit, and otherwise predetermine the function, form, cost, and development schedule of the desired UAV system. The identification of a problem and associated definition of need provides a valid and appropriate starting point for design at the conceptual level.

      Selection of a path forward for the design and development of a preferred system configuration, which will ultimately be responsive to the identified customer requirement, is a major responsibility of conceptual design. Establishing this early foundation, as well as requiring the initial planning and evaluation of a spectrum of technologies, is a critical first step in the implementation of the systems engineering process. Systems engineering, from an organizational perspective, should take the lead in the definition of system requirements from the beginning and address them from a total integrated life-cycle perspective.

      As the name implies, the UAV conceptual design phase is the UAV design at the concept level. At this stage, the general design requirements are entered in a process to generate a satisfactory configuration. The primary tool in this stage of design is the “selection.” Although there are variety of evaluation and analysis, but there are no much calculation. The past design experience plays a crucial role in the success of this phase. Hence, the members of conceptual design phase team must be the most experienced engineers of the corporation. Figure 1.5 illustrates the major activities which are practiced in the UAV conceptual design phase. The fundamental output of this phase is an approximate three-view of the UAV that represents the UAV configuration.

      Figure 1.5: UAV conceptual design.

      A UAV comprised of several major components. It mainly includes wing, horizontal tail, vertical tail, fuselage, propulsion system, landing gear, control surfaces, and autopilot. In order to make a decision about СКАЧАТЬ