Optimal configuration of the mechanical structure and flap actuator for hydrofoils
Abstract: Hydrofoil vessels are becoming more popular and driving marine development forward. Since the water friction is greatly reduced, they allow achieving higher speeds and electrification of the boats. FoilCart is a full electric active controlled hydrofoil boat designed as a research project at KTH. The small version of this boat is considered to be designed in this thesis and an optimal configuration for the mast and rudder of the boat is studied. The study is prone to be used as a basis for hydrofoil wing and flap design and includes research on small electromagnets. The design and dynamics of the hydrofoils are adapted from aeronautics. An idea of a morphing airplane wing has been successfully tested and now evaluated for the hydrofoil application. An electromagnetic actuator is proposed for the actuation of the rudder as competitor to typically used once. This study finds the optimal combination of an actuator and mechanical structure comparing classical actuator (servo) with electromagnetic actuator and classical structure (hingetype) with morphing structure. Those four configurations are evaluated with respect to energy usage, response time, volume of the solution and maximal rudder force. Workflow of the thesis is divided to four main parts: calculations of the hydrodynamic forces to realize the peak torque that the rudder will need to withstand in water, CAD design of each evaluated configuration (including material and actuator studies), prototype manufacturing for the verifications, summary of the information and presentation according to evaluation parameters. The study is concluded with an optimal choice of the configuration with respect to different factors. Servo actuator in combination with hinge-typed structure is most optimal in terms of energy efficiency. The most compact configuration is electromagnetic actuator in combination with hinge-type structure. Maximal rudder force is supplied by the servo meanwhile fastest response is achieved by electromagnetic actuator. Due to better hydrodynamic characteristics, maximal rudder force and compact volume, a configuration of morphing structure and servo actuator is recommended for implementation for miniaturized version of FoilCart vessel. Implementation means a first step to apply morphing structures into marine applications. Each configuration has its own strength and weakness and therefore all four are to be carefully studied before choosing an actuator / structure according to the application.
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