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Sea-state interaction based dynamic model of the Liquid Robotics' Wave Glider: Modelling and control of a hybrid multi-body vessel
A new class of unmanned marine research vessels makes use of wave propulsion to minimise energy requirements during voyages. Existing models of these hybrid sea-surface and underwater craft have not considered if the platform’s interaction with the immediate surrounding sea could be incorporated to...
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| Format: | Thesis |
| Language: | English |
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Department of Electrical Engineering
2019
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| _version_ | 1867613609030320128 |
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| access_status_str | Open Access |
| author | Rampersadh, Gevashkar |
| author2 | Verrinder, Robyn |
| author_browse | Rampersadh, Gevashkar Verrinder, Robyn |
| author_facet | Verrinder, Robyn Rampersadh, Gevashkar |
| author_sort | Rampersadh, Gevashkar |
| collection | Thesis |
| description | A new class of unmanned marine research vessels makes use of wave propulsion to minimise energy requirements during voyages. Existing models of these hybrid sea-surface and underwater craft have not considered if the platform’s interaction with the immediate surrounding sea could be incorporated to allow for more accurate navigation and path planning. To this end a detailed three-dimensional model of one such vessel, the Liquid Robotics’ Wave Glider, has been developed in this study. The multi-body system is described using DenavitHartenberg parametrisation and a Lagrangian approach is used to generate the equations of motion for the body. Physical dimensions are derived from platform measurements and from the product specification sheet, hydrodynamic factors are derived from a SolidWorks model of the system, and added mass components are determined from empirical data. Finally, the dynamic model is verified for a given sea state and multiple sea states are tested to investigate the effect on the model’s performance. The developed Wave Glider model is shown to have a realistic response when hydrodynamic factors, added mass and hydrodynamic damping forces, are included and to sea states in terms of the hydrostatic restorative response. The wave-driven propulsion provided by the hydrofoils is shown to have dependence on the sea state by running the model in an open-loop simulation. Following the model validation, a control system is developed for the Wave Glider model to allow yaw attitude control of the glider using the controllable glider rudder input. The control system is generated making use of quantitative feedback theory (QFT) methods to provide robust control for the under-actuated system. The control scheme is shown to provide suitable performance for sea states that result in variable glider velocities. The model’s performance, in terms of the average velocity, is shown to have dependence on the direction of the sea state by running the model in an open-loop simulation for multiple sea states with sinusoidal waves approaching the Wave Glider model from different directions. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/29352 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:38:51.903Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2019 |
| publishDateRange | 2019 |
| publishDateSort | 2019 |
| publisher | Department of Electrical Engineering |
| publisherStr | Department of Electrical Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/29352 Sea-state interaction based dynamic model of the Liquid Robotics' Wave Glider: Modelling and control of a hybrid multi-body vessel Rampersadh, Gevashkar Verrinder, Robyn Boje, Edward Electrical Engineering A new class of unmanned marine research vessels makes use of wave propulsion to minimise energy requirements during voyages. Existing models of these hybrid sea-surface and underwater craft have not considered if the platform’s interaction with the immediate surrounding sea could be incorporated to allow for more accurate navigation and path planning. To this end a detailed three-dimensional model of one such vessel, the Liquid Robotics’ Wave Glider, has been developed in this study. The multi-body system is described using DenavitHartenberg parametrisation and a Lagrangian approach is used to generate the equations of motion for the body. Physical dimensions are derived from platform measurements and from the product specification sheet, hydrodynamic factors are derived from a SolidWorks model of the system, and added mass components are determined from empirical data. Finally, the dynamic model is verified for a given sea state and multiple sea states are tested to investigate the effect on the model’s performance. The developed Wave Glider model is shown to have a realistic response when hydrodynamic factors, added mass and hydrodynamic damping forces, are included and to sea states in terms of the hydrostatic restorative response. The wave-driven propulsion provided by the hydrofoils is shown to have dependence on the sea state by running the model in an open-loop simulation. Following the model validation, a control system is developed for the Wave Glider model to allow yaw attitude control of the glider using the controllable glider rudder input. The control system is generated making use of quantitative feedback theory (QFT) methods to provide robust control for the under-actuated system. The control scheme is shown to provide suitable performance for sea states that result in variable glider velocities. The model’s performance, in terms of the average velocity, is shown to have dependence on the direction of the sea state by running the model in an open-loop simulation for multiple sea states with sinusoidal waves approaching the Wave Glider model from different directions. 2019-02-06T09:43:06Z 2019-02-06T09:43:06Z 2018 2019-02-05T09:45:05Z Master Thesis Masters MSc http://hdl.handle.net/11427/29352 eng application/pdf Department of Electrical Engineering Faculty of Engineering and the Built Environment University of Cape Town |
| spellingShingle | Electrical Engineering Rampersadh, Gevashkar Sea-state interaction based dynamic model of the Liquid Robotics' Wave Glider: Modelling and control of a hybrid multi-body vessel |
| thesis_degree_str | Master's |
| title | Sea-state interaction based dynamic model of the Liquid Robotics' Wave Glider: Modelling and control of a hybrid multi-body vessel |
| title_full | Sea-state interaction based dynamic model of the Liquid Robotics' Wave Glider: Modelling and control of a hybrid multi-body vessel |
| title_fullStr | Sea-state interaction based dynamic model of the Liquid Robotics' Wave Glider: Modelling and control of a hybrid multi-body vessel |
| title_full_unstemmed | Sea-state interaction based dynamic model of the Liquid Robotics' Wave Glider: Modelling and control of a hybrid multi-body vessel |
| title_short | Sea-state interaction based dynamic model of the Liquid Robotics' Wave Glider: Modelling and control of a hybrid multi-body vessel |
| title_sort | sea state interaction based dynamic model of the liquid robotics wave glider modelling and control of a hybrid multi body vessel |
| topic | Electrical Engineering |
| url | http://hdl.handle.net/11427/29352 |
| work_keys_str_mv | AT rampersadhgevashkar seastateinteractionbaseddynamicmodeloftheliquidroboticswaveglidermodellingandcontrolofahybridmultibodyvessel |