Height and Wave State Observer for Hydrofoil Boats : For a smoother ride in wavy conditions

Sammanfattning

Hydrofoil technology enables the electrification of high-speed leisure boats and ferries, as these vessels consume less energy than conventional displacement or planing designs. However, hydrofoil boats can be unstable, especially in wavy conditions, and then need an active control system to ensure stable flight. To implement such an active control system, a state observer is required, which is the main focus of this thesis. The estimated states are the height above the calm water surface, vertical velocity, and the wave amplitude, frequency, and phase. A linear discrete-time-invariant Kalman filter is used for height estimation, with additional wave filters tested. The wave frequency is estimated using the Aranovskii frequency estimator, the amplitude is estimated with a low-pass filter, and the phase is estimated using an extended Kalman filter. The phase-time-path difference from the height sensors’ measurements is used to estimate the waves’ direction of propagation. The complete observer was then evaluated in multiple experiments of increasing complexity. First, the observer behaviour was tested in simulations using sine waves and JONSWAP-spectrum waves at different headings. The observer was verified with recorded data from a Candela C-8, before being tested in sea trials with the current control system. Finally, the observer was tested with a newly developed model predictive controller.