Development of a Low-Friction Testbed for Model Scale Wave Energy Converter Control System Studies

Wave energy research data quality is greatly limited by friction. Small-scale models used for research do not produce large amounts of power, so any parasitic system losses can considerably cut into data quality. This paper discusses the development and validation of a low-friction testbed for model scale wave energy converter control system studies. This testbed is designed for heave-only, point absorber testing. The testbed low friction is achieved by non-contact components including air bearings, a voice coil power take-off (PTO), and a laser position sensor. The design of a scaled-model WEC with accurate data collection on forces and motions in wave tank testing is crucial for WEC modeling and PTO systems validation. A combination of dry bench testing and wave tank experiments are conducted without any external actuation. The primary objectives were to evaluate the model's capabilities and identify potential friction losses. A mathematical model was employed for validation, and the comparison between experimental and simulated data yielded highly promising results; the comparison revealed a close match between the experimental and simulated data across a wide range of amplitudes and frequencies for monochromatic waves. Furthermore, during the actuation of the voice coil, a slight discrepancy was observed, primarily attributed to the hypothesized frequency-dependent behavior of the coil's force constant, denoted as K
t
. A constant K
t
for all frequencies does not seem to yield accurate results. These findings and development are key for the advancement of WECs, control algorithms, and the overall performance of this technology in real-world applications.