Dehlsen Associates’ Centipod wave energy converter’s (WEC) main potential design limitation is the inherent theoretical capture limit of a single degree of freedom (DoF) heaving point absorber. This TEAMER project aimed to leverage the expertise of Oregon State University WESRF’s personnel to implement a second DoF in the existing model predictive control (MPC) optimization formulation, allowing Dehlsen Associates to pursue future exploration of multi-DoF WEC designs.
The modeling and control work in this project began with integration of pitch kinematics and angular momentum into a single pod, state space plant model. A second disturbance vector for pitch excitation was then introduced, allowing for heave-only MPC control with the new 2 DoF state space model. Direct pitch control was then added to the MPC formulation and used to evaluate the heave-pitch controller with linear and non-linear hydrodynamics using 2 DoF MPC and the WEC-Sim model.
The power gain resulting from this project fell within the mean power improvement range anticipated. In moving from 1-DoF (heave) to 2-DoF (heave-pitch), the power gain for a single pod is 13.7% for both the linear and nonlinear hydro results, providing a justification for further pursuit of this line of research and continued work to integrate this DoF with the larger WEC.