Abstract
Abstract A nonlinear inerter pendulum vibration absorber is integrated with an electromagnetic power take-off system (called IPVA-PTO) and is analyzed for its efficacy in ocean wave energy conversion of a spar platform. The IPVA-PTO system shows a nonlinear energy transfer phenomenon between the spar and the IPVA-PTO which can be used to convert the vibration energy of the spar into electricity while reducing the hydrodynamic response of the spar. The hydrodynamic coefficients of the spar are computed using a commercial boundary-element-method (BEM) code. It is shown that the energy transfer is associated with 1:2 internal resonance of the pendulum vibration absorber, which is induced by a period-doubling bifurcation. The period-doubling bifurcation is studied using the harmonic balance method. A modified alternating frequency/time (AFT) approach is developed to compute the Jacobian matrix involving nonlinear inertial effects of the IPVA-PTO system. It is shown that the period-doubling bifurcation leads to 1:2 internal resonance and plays a major role in the energy transfer between the spar and the pendulum. The response amplitude operator (RAO) in heave and the capture width of the IPVA-PTO-integrated spar are compared with its linear counterpart and it is shown that the IPVA-PTO system outperforms the linear energy harvester as the former has a lower RAO and higher capture width.
Published Version
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