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Conceptual and Control System Design of a Lagrangian Float

Tid: On 2020-07-22 kl 10.00 - 11.00

Plats: Zoom (https://kth-se.zoom.us/j/63578290886)

Respondent: Anna Madlener

Opponent: Filip Klaesson

Handledare: Jakob Kuttenkeuler (Department of Engineering Mechanics), Peter Sigray (Department of Engineering Mechanics), Joana Filipa Gouveia Fonseca (Department of Decision and Control Systems)

Examiner: Kalle Henrik Johansson

Abstract: Lagrangian floats are autonomous drifting buoys that ideally behave identical to the surrounding water particles in the water column. Existing examples of Lagrangian floats are often costly and heavy, carrying expensive sensor and data collection equipment, which prevents their scalability to larger fleets or broader usage. There is significant oceanographic benefit to be expected from the deployment of a larger group of Lagrangian floats operating together to sample the environment during mission times of weeks or months, such as the tracing of interval waves. The development of such a fleet of Lagrangian floats realistically requires a scalable and low cost design, focused rather on a simple mechanical and low weight structure as opposed to elaborate sensing equipment. Therefore, the aim of this thesis is to firstly develop a design tool that allows user-friendly dimensioning of a Lagrangian float according to necessary conditions of feasibility. Secondly, this thesis presents a control mechanism to autonomously adjust the float's buoyancy. The control should facilitate two operational modes: keeping a target depth in the presence of disturbances or uncertainties, and profiling the water column over a long period of time while neither consuming excessive energy nor risking the loss of significant data collection. Future work will entail the mechanical realization of the suggested prototype as well as improved nonlinear or adaptive control techniques ideally tailored for internal wave trajectory following.