Hydrofoil vessels show unstable behaviour when operating in foilborne condition. Therefore, an active control system (ACS) is used. Designing an ACS requires an accurate dynamic model. While many theoretical frameworks have been proposed, experimentally validated models for hydrofoil vessels remain limited. This study aims to identify the pitch and height dynamics of the Flying Fish 1 hydrofoil demonstrator. For this, the closed loop system identification (CLSI) method in combination with a multisine excitation signal is used. The identified dynamics will be compared to a parametric dynamical model derived from literature. And, using the resulting frequency domain data, an attempt is made to improve the control performance of the pitch and height control loops.

The CLSI method, in combination with the multisine disturbance signal proved to be an effective method. Accurate frequency domain results were obtained within the frequency range of 1 to 10 Hz. Within this range, the parametric dynamic model aligned well with experimental data. The experiment was repeated three times at 4.0, 4.5 and 5.0 m/s and resulted in similar responses, aside from a negative trend in magnitude at increasing velocities. The use of frequency domain tuning led to an increase in phase margin for the pitch controller and a bandwidth increase of 667\% for the height controller. The results show that CLSI is a powerful tool in estimating the dynamics of a hydrofoil vessel, laying the foundation for advanced control strategies and improved system performance.