Bi-level Integrated System Collaborative Optimization Method And Its Application To The Overall Conceptual Design Of Deep Sea Space Station

Deep Sea Space Station is a complex system engineering involving many high-techs and disciplines, such as hydrodynamics, structure, material, energy and propulsion, maneuverability and control etc. There are many mutual interactions and even contradictions among these disciplines, so the overall conceptual design of Deep Sea Space Station (DSSS) is a typical Multidisciplinary Design Optimization (MDO) problem. However, traditional design method can not consider the mutual influence sufficiently among these disciplines, and depends much on the designer's experience, so it often leads to suboptimal design instead of optimal design and reduces the general performance of DSSS. Besides, there are some disadvantages of traditional design method: long design cycle, low efficiency and no experience for the DSSS design, so it will result in rapid increase of R&D cost with the direct application of traditional design method to the overall conceptual design of DSSS. Therefore, the traditional design method is not fit to the optimal design of the DSSS. In order to solve the difficulty faced by the overall conceptual design of DSSS, new design theory and method is necessary to break through the limitation of the traditional design method and to realize the system optimal design of the DSSS.Under this circumstance, the present study is a part of the National Defense Basic Scientific Research Project–"key techniques research of Deep Sea Space Station"supported by the Commission of Science, Technology and Industry for National Defense of the People's Republic of China. It introduces Multidisciplinary Design Optimization (MDO) method emerged from aeronautics and astronautics fields for complex engineering integrated optimization problems, and explores feasibility and applicability of MDO method to the overall conceptual design of DSSS. Focusing on MDO method and its application to the overall conceptual design of DSSS, this thesis mainly consists of the following aspects:1. Review about the related research areaProgress of researching Deep Sea Space Station in the world, as well as MDO's research and application status are overviewed. The significance of the MDO's application to the overall conceptual design of DSSS is stated. The development, difficulties and main research contents of MDO are reviewed.2. Comparison of different MDO MethodsThree representative MDO methods: MDF, CO and BLISS are studied and described in detail about the mechanism and mathematical models. Combined with multi-attribution decision method, one benchmark example provided by NASA is adopted to compare these three MDO methods quantitatively with different initial points. The result shows that: (1) For different engineering object, the suitable MDO method will be different, there is no absolutely best one; (2) Based on BLISS and CO to propose a new MDO method will contribute a lot to the overall conceptual design of DSSS in practical sense.3. Development of Bi-Level Integrated System Collaborative Optimization (BLISCO) based on the main characteristics of BLISS and COWhile maintaining the collaborative mechanism of CO, BLISCO is proposed with the decomposition of design variables into system design variables and subsystem design variables, and the replacement of compatibility constraint with the sum of coupled output responses as an integrated objective of subsystem, which idea comes from BLISS. Two benchmark examples provided by NASA are adapted to testify the performance of BLISCO. The results show that BLISCO is an effective MDO method with accurate result, reliable robustness and satisfaction of convergence. Furthermore, BLISCO will be a powerful tool to realize the overall conceptual design of DSSS based on MDO.4. Overall conceptual design of HOV based on BLISCOIn order to better realize the overall conceptual design of DSSS based on MDO and to explore feasibility and applicability of BLISCO to the overall conceptual design of submersible, BLISCO is successfully applied to the overall conceptual design of HOV. The result shows that the general performance of HOV is highly improved, design cycle is much decreased, and the integrated effect of BLISCO is better than PGA-CO. Therefore, BLISCO can be applied to the MDO of submersible completely, and the successful overall conceptual design of HOV will provide engineering support for the overall conceptual design of DSSS based on BLISCO.5. Research on the System Synthesis Model of DSSSBased on the characteristics of DSSS, a System Synthesis Model (SSM) is developed for DSSS. It includes six modules, which are hull, resistance & propulsion, energy, structure, weight & hydrostatic equilibrium and maneuverability. The inputs and outputs of different modules are also defined. According to the application with Design Structure Matrix (DSM), a reasonable design sequence is established, and it is found that there are two characteristics of SSM: (1) many data exchanges between different modules; (2) there is only feed forward and no feed back. Therefore, the overall conceptual design of DSSS is a sequential process, which belongs to the weak coupling system. This research has laid a solid foundation for the overall conceptual design of DSSS based on BLISCO.6. Research on the application of BLISCO method to the overall conceptual design of DSSSAfter the DSSS is decomposed into hydrodynamic subsystem, structure subsystem and general performance subsystem based on the SSM, BLISCO is applied to the overall conceptual design of DSSS. The successful application with BLISCO reveals that: (1) decomposition with three subsystems is feasible; (2) BLISCO can be applied to the overall conceptual multidisciplinary design optimization of DSSS efficiently.The innovative research works in this thesis can be summarized as follows:1. Based on the main characteristics of BLISS and CO, BLISCO is developed in this thesis. According to the benchmark tests, the several advantages of BLISCO are revealed, which enriches and develops the MDO method;2. Focused on the characteristics of DSSS, a parametric System Synthesis Model (SSM) is developed. With the decomposition of DSSS into three subsystems based on the SSM, BLISCO is successfully applied to the overall conceptual design of DSSS, which realizes the overall conceptual multidisciplinary design optimization of DSSS.3. In order to overcome the numerous calculations and low efficiency during the application of PGA-CO to overall conceptual design of HOV, BLISCO is applied to the overall conceptual design of HOV. General performance and design efficiency of HOV are much improved by BLISCO, which validates the superiority of BLISCO again.