Date of Award
Doctor of Philosophy in Ocean Engineering
Stephen C. Licht
Biomimetic propulsion is an active area of research in the field of robotics. This work presents advancements to help improve the performance of vehicles employing oscillating foil propulsion. For vehicles operating near the sea floor, ground effect on rolling and pitching foils was investigated in Manuscript 1. The ‘ground effect’ was found to be present and to cause a repulsion force on the foil as well as an increased thrust force. It was also shown that ground effect can be activated by biasing the foil into the ground effect zone while the vehicle maintains a greater distance from the boundary. The effects on the foil due to `ground effect' were compared to previous work done with heaving and pitching foils showing that `ground effect' is an inherently 3 dimensional phenomena and studies using 2 dimensional constrained flow cannot be extrapolated into rolling and pitching foils. The second manuscript expands on this work, investigating the effect that free surface has on the oscillating foil. Similar to `ground effect' it was found that the presence of the boundary creates a repulsive force pushing the foil away from the boundary. However, instead of increased thrust, the free surface causes a decrease in thrust forces on the foil. The third manuscript uses an analytical model to design a control system that uses force feedback from the foil in order to compensate and estimate a constant disturbance such as crossflow. The control system was able to compensate for a constant crossflow and was able to estimate the angle of the crossflow based on the force feedback to within 0.5 degrees. These advancements will help improve vehicles with oscillating foil propulsion that will open up new opportunities for investigation and exploration of complex oceanic environments.
Perkins, Matthew, "ADVANCEMENTS IN BIOMIMETIC UNDERWATER PROPULSION: BOUNDARY INTERACTIONS AND CROSSFLOW COMPENSATION" (2019). Open Access Dissertations. Paper 963.