Research on Permanent Magnet-Induction Magnetic Screw for Wave Energy Conversion

A new type of permanent magnet-induction magnetic screw (PMI-MS), as a linear rotary actuator (LRA) with high thrust density and high energy conversion efficiency compared with the traditional direct-drive wave energy conversion (DD-WEC), is proposed and applied in wave energy conversion (WEC). The proposed PMI-MS adopts the method of quasi-Halbach magnetization array and hybrid excitation to overcome the shortcomings of the non-adjustable thrust of the permanent magnet magnetic screw (PM-MS) and the low thrust density of the induction magnetic screw (I-MS). At the same time, the special structure of adjacent teeth with different heights on the mover can improve the electromagnetic thrust generated by the electric excitation, thereby further improving the thrust adjustment capability and thrust density of the PMI-MS. Compared with conventional PMI-MS, it has higher thrust density and higher wave energy conversion efficiency compared with the wave energy linear generators. To optimize and design the PMI-MS, analytical methods and global optimization algorithms are adopted. Finally, finite element simulations are used to verify that the proposed PMI-MS has higher thrust density.