With the increasing demand for energy resource, the development of marine energy harvesting technology has attracted widespread attention. Herein, a spherical electret wave power generator is designed and constructed for ocean wave energy harvesting. Based on electrostatic induction from electret material, the generator converts wave energy into electric energy through the bias voltage of the folded electret power generation unit. With ultra-low excitation frequency at 2Hz, the peak-to-peak output voltage and output power can be reached up to around 300 V and 20 mW, respectively. Compared with other traditional wave energy generators, the utilization of space in the sphere is improved by the folded structure, which also has the advantages in terms of simple structure, high-energy conversion efficiency, light weight and small size. The generator is also capable of collecting low-frequency vibration energy in random directions, as well as realizing large-scale power supply after deploying an array of structures.

We propose a new linearization point selection method based on a global maximum error controller for the trajectory piecewise-linear (TPWL) model order reduction (MOR). This method is based on a simple fact that the simulation cost of the TPWL model is very low, and selects the state at which the responses of the current TPWL model and the full nonlinear model have the maximum difference as a new linearization point. Numerical results show that the proposed method can generate the TPWL model of smaller size and higher accuracy, and can easily be extended to generate the TPWL model for multiple training inputs.