Development of a non-linear hydrodynamic maneuvereing model of a diver delivery vehicle
Sammanfattning: The SEAL Carrier is a marine hybrid craft with capacity to travel both on the surface and completely submerged with main objective to transport a group of divers. The craft is developed for transporting a unit of combat divers in and out the of area of operation where the high speed at surface and low signature when submerged are key features. In order to reduce the workload for the pilots during longer transports in submerged mode the manufacturer James Fisher Defence (JFD) has instigated two master theses with the aim to develop an automated depth control.This thesis concerns the ÿrst part in this project and describes the development of a hydrodynamic model of the craft. The main purpose of the model is to re°ect the behavior of the craft with focus on depth maneuvers so it can be used as a tool for the development of such a controller.Initially the fundamental theory that this mathematical model is established from is presented and explained. From how positions and motion of an underwater craft is expressed with well established methods the six equa-tions of motion necessary to fully describe these are derived. For estimating the external forces acting on the craft a semi-empirical approach is presented in order to obtain expressions and estimations of these. With these results a platform for the model have been established in the programming environment MATLAB/SIMULINK. With this platform as basis a procedure for manipulating the external forces in order to achieve a better repre-sentation of the real craft is presented.The developed model experiences some di˝culties to capture the motion of the real craft during maneuvers in depth. The cause for this is considered to be because of the methods used for expressing the hydrodynamic forces developed by the hull. The function of the model to serve as a tool for the development of a depth controller is still to be veriÿed and tests are planned. The developed model has a modular design that enables simple modiÿcations of the implemented theory as well as structural modiÿcations for future development and improvements.
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