Streamlined Experimental Approach to System Identification of WEC Dynamics and Excitation Characteristics

Abstract Understanding the dynamics of wave energy converters (WECs) is crucial for optimizing their design and performance. Empirically-based modeling can capture complex dynamics that are otherwise difficult to model with first principles, however collecting empirical test data typically involves long, costly testing campaigns. In this study we present the system identification and validation of a multi-input, single-output model of the Lab Upgrade Point Absorber (LUPA). The total testing duration of approximately 2 hours demonstrates significant efficiency compared to traditional week-long testing campaigns. We use a single experimental dataset to derive both the excitation transfer function and intrinsic admittance transfer function, which we express in a non-parametric form relative to the power take off (PTO) degree of freedom (DOF). The dataset contains a series of six trials, with two distinct power levels in the multisine excitation signals for each input. The inputs are the PTO force signal for active actuation and the concurrently generated irregular waves, implemented with white noise (WN) and pink noise (PN) spectra, respectively. For each power level we implemented the input signals with three different phase vectors. Validation experiments showed good agreement (approx. 70% goodness-of-fit) with the identified models, indicating the effectiveness of the approach.