Integrated Framework for Aircraft Design and Assembly Tradeoffs

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Huynh, Dat
Mavris, Dimitri N.
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Aircraft passenger traffic is expected to increase and lead to demand for 40,000 new aircraft by 2040. Aircraft production rates have been rising to meet this demand, but delivery backlogs are growing at even faster rates. Large backlogs can lead to missed deliveries, canceled orders, and traffic congestion due to too few planes for too many passengers. This comes at a time when the two primary aircraft manufacturers, Boeing and Airbus, are competing for dominance in a market that a third competitor, Comac, is poised to enter as well. Increased production rates to better meet customer demand would thus also allow one of them to gain the edge over the others. Aircraft production rates must be increased and done so without inducing enormous costs to meet passenger demand and to stay competitive. Changes to aircraft assembly, which constitutes up to 50% of total production time and up to 30% of total production cost, during the design process can address this. Current Design for Assembly methods addressing assembly changes during the design process range from Product Lifecycle Management techniques to various methods in Systems Engineering and have been used to great success. However, few such methods consider aircraft design in their analysis, which would enable further tradeoff capabilities and greater production rate and cost improvements. Those methods that do explicitly incorporate aircraft design analysis alongside the assembly analysis insufficiently consider several key assembly aspects such as assembly sequence planning (ASP) and more detailed assembly line balancing (ALB), which can be used to optimize the assembly line. This work establishes a better connection between the aircraft design and assembly disciplines and joins them by accounting for geometry and material factors common to both using ASP and ALB. First, the correct analysis fidelity for the aircraft design process and ASP's geometric reasoning process is determined to allow geometry data to easily flow between the two, linking them. Then, the ASP and ALB analyses are combined and augmented to account for the novel materials traded during aircraft design and the manufacturing processes used to make them. Afterwards, the most promising assembly sequences are optimized for using metrics representative of both ASP and ALB so that sub-optimal assembly sequences are not line balanced, reducing the overall problem size to explore the large design space more efficiently. From all this an integrated aircraft design and assembly framework is made that strives to obtain higher production rates, lower costs, and better tradeoffs by leveraging the additional feedback loops produced via consideration of variables common to both disciplines. Finally, this framework is tested and compared with a state-of-the-art framework on a representative aircraft's wingbox and its production system. The developed framework demonstrates it is able to obtain significantly higher throughput and lower cost values by simultaneously: sizing the aircraft to meet its performance requirements; accounting for the aircraft's geometry via ASP determining assemblability and ALB determining the consequent task time, cost, and space requirements; incorporating the aircraft's material system via usage of specialized sequences in ASP and identification of optimal line balances in ALB given the material's manufacturing process and its subsequent resource requirements; and flowing all this manufacturing information back upstream to maximize the aircraft's manufacturability during its sizing. The developed framework is thus able to make tradeoffs such as what size the aircraft should be for a given performance, throughput, and cost requirement, what the maximum production rate is given a design, material, manufacturing process, and spatial constraint, and what costs are incurred given a desired production rate. This provides the designer with a greater understanding of the problem and its constraints and allows them to see what factors can help them increase production rate as well as what the associated costs are.
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