Wave basin testing of optimal PTO control of 6-float M4 WEC

Power-take-off (PTO) control is applied to the multi-float attenuator-type wave energy converter (WEC) M4, with two PTOs in a 6-float configuration, and tested experimentally in a wave basin. Previous control applications using wave predictions from auto-regression (AR) and linear non-causal optimal control (LNOC) have shown average power to be increased by 30%-100% in numerical simulations. In this experiment two DC servo-motors are used to execute the control algorithm implemented on a microprocessor. Average power is calculated from the recorded torque and hinge velocity measurements. Both causal and non-causal control are applied, with deterministic sea wave prediction (DSWP) rather than AR, and a torque limit of 3 Nm, and also 6 Nm for the non-causal case. Causal control improves average power by up to 49% while non-causal (LNOC) by up to about 116% with a 3 Nm torque limit and 274% with a torque limit of 6 Nm.