Research On Design And Optimization Methods For The Speed Performance Of Autonomous Sailboats

In recent years,there has been a growing demand for improved ocean observation capabilities due to the development of ocean big data technology and the expansion of marine scientific research into deep and distant seas.Autonomous sailboats,as windpowered ocean observation platforms,have emerged as a powerful complement to existing systems.However,the design and optimisation of autonomous sailboats have received relatively little research attention compared to control methods.As the design of autonomous sailboats dramatically affects their performance,preliminary design and optimisation significantly limit their speed performance,reducing ocean observation efficiency and area passability.To address this issue,this thesis,based on the project "New Hydrofoil Autonomous Sailboat"(Y8K7080702),conducts systematic research to improve the speed of autonomous sailboats.The goal is to provide a theoretical basis and technical guidance for developing and enhancing these platforms.The main contributions of this thesis can be summarised as follows:1.Systematic review and analysis of autonomous sailboat designs: The thesis reviews and analyses the designs in the context of ocean observation requirements.It identifies the speed as the primary limitation of the current platform,which is attributed to its susceptibility to capsizing.The reasons behind the conflict between speed and overturning resistance are thoroughly analysed,along with the challenges designers face in achieving an optimal balance.Two countermeasures are proposed to overcome challenges: using computational fluid dynamics simulation and simulation-driven design techniques to find the optimal trade-off or enhancing the overturning resistance’s environmental adaptability.2.Quantitative evaluation method for autonomous sailboat speed: Considering the significant design space and lack of prior performance estimates for autonomous sailboats,the thesis proposes a speed quantification evaluation method based on computational fluid dynamics simulation and an optimisation solver.The introduction of computational fluid dynamics simulation enables the evaluation of any autonomous sailboat design.An optimised genetic algorithm solver and an optimisation strategy based on neighbourhood information are presented to enhance the evaluation accuracy and computational efficiency.This research provides an effective method for comparing designs and is a basis for optimising autonomous sailboat design.3.Design method for speed optimisation of autonomous sailboats: The thesis proposes a simulation-driven design method to address the need for a systematic approach to autonomous sailboat design.This approach tackles the challenge of sampling the vast design space without prior performance estimation by incorporating Bayesian optimisation and knowledge transfer techniques.The research offers a systematic and quantitative approach to autonomous sailboat design,enabling the identification of the optimal trade-off between speed and overturning resistance.4.Speed optimisation of autonomous sailboats based on stabilising hydrofoils: For enhancing the environmental adaptability of autonomous sailboats and mitigating the trade-off between overturning resistance and speed,the research introduces various environmental adaptive mechanisms for dynamic overturning resistance.The passive hydrofoil is chosen as the stabilising device,and a specific hydrofoil solution is designed.Hydrodynamic simulations explore hydrofoils’ stability,drag,and speed enhancement effects with different aspect ratios.This research validates the effect of stabilising hydrofoils in the speed enhancement of autonomous sailboats and provides design information and technical insights for realising hydrofoil-assist autonomous sailboats.