A Sensitivity-based Coordination Method And The Application To Structural Optimization Of Aircraft Families

With the development of market economy and globalization,the competition in aviation industry becomes increasingly fierce.Under this backdrop,aircraft design based on product families has received considerable attention from both industry and academia in recent years.Aircraft family can not only reduce the time for development,but also provide significant opportunities for aircraft life cycle cost reduction.The current flight vehicle design theories and methods focus primarily on single aircraft design,and it is necessary to develop the design theories and methods for aircraft families.The multidisciplinary design optimization(MDO)methods are methodologies that design the complex engineering systems by coherently exploiting the couplings and synergisms between the different disciplines,which have obtained widespread application in aviation and aerospace fields.This dissertation aims at to develop the optimization method for aircraft family structural problems by taking advantage of the basic idea and techniques in MDO filed.Around this key idea,the following works have been done in this thesis:1.The concepts of aircraft family is introduced,and the corresponding classification standards are presented,then review the application status,benefits,and problems found during development process of each types of aircraft family,respectively.2.The optimization methods in product family design fields are studied and reviewed.The problem formulation of product family optimization problem is introduced firstly.Then present a review on the optimization methods for product family problems.The algorithm structure and development process of each optimization methods are described and analyzed in detail,which provides a theoretical foundation and guideline for devising new method.3.The sensitivity-based coordination method(SCM)is proposed in this thesis,and the optimum sensitivity analysis and its application to the system level of SCM is then investigated.Compared with typical MDO methods,the innovation of SCM is that the system level coordinates the shared variables based on sensitivity information,and the coordinated shared variables are determined by minimizing performance deviation and constraints violation.The optimal target of subproblem is to minimize the sum of global objective and a penalty function,and both quadratic and augmented Lagrangian penalty functions can be used.Compared with general sensitivity derivative,the optimum sensitivity derivative includes more information and can improve the efficiency of system level in SCM.The optimum sensitivity analysis based on 1st-order information and 2st-order information is investigated,and then applied to SCM respectively.4.The numerical performance of SCM is investigated through two test examples,and the results are compared with that obtained through collaborative optimization(CO)and analytical target cascading(ATC)methods.The penalty functions in both SCM and ATC adopt quadratic and augmented Lagrangian penalty function,respectively.Besides,the sensitivity information in SCM used general sensitivity derivative and optimum sensitivity derivative,respectively.The results suggest that SCM is robust and leads to a substantial reduction in computational effort compared with CO and ATC method.Regarding the penalty function,results show that the augmented Lagrangian penalty function can improve the efficiency and optimum results for both ATC and SCM methods compared with quadratic penalty function.Regarding the sensitivity derivative,results show that the SCM based on optimum sensitivity derivative is more efficient and robust and can get a better solution compared with the general sensitivity derivative.5.To demonstrate the potential application scenario of structural design of aircraft families,two original examples are proposed in this paper: the wing structure design problem for a modular unmanned aerial vehicle(UAV)family and the nose gear reinforced frame structure design problem for an aircraft family.The SCM is successfully applied to the two problems,which further highlights the efficiency and robustness of SCM.The research in this thesis shows that the SCM has extensive applied foreground and practical value in both aircraft family and MDO field.The work of this dissertation also can provide a theoretical basis for further study or improvement of the design methodology for aircraft family design.