The complex curved boundary of the topology optimization model is not conducive to industrial manufacturing hence the necessity to reconstruct the geometrical model. This study presents a general method for the boundary regularization fitting reconstruction of a topological optimization model based on the Freeman code. This method is performed as follows: the unit vector is defined; the vectorized expression of the Freeman code boundary is established; through the concept of the boundary bending parameter, determination of the bending degree of the Freeman code boundary is established; an elemental structure analysis method is proposed, and the logic of the automatic extraction of the control points of the Freeman code boundary fitting is achieved. This method proposes a series of innovative technical methods, such as unit vector definition, boundary bending matrix, and elemental structure analysis method, and designs a complete set of structural analysis logic for a Freeman code type boundary, which can automatically analyze the structure feature of the 8-connected Freeman code boundary, extract the fitting control points on the boundary, and complete the automatic fitting and reconstruction of the boundary. This method is robust and applicable to all Freeman code boundaries. The entire process is automated.
Converting ambient vibration energy into electrical energy is a potential technology for powering wireless sensor networks (WSNs). In this paper, an electromagnetic vibration energy harvester (EVEH) based on a diamagnetic levitation system is proposed for harvesting energy from ultralow-frequency, broadband vibration sources. In this design, a diamagnetic levitation structure is utilized to reduce the operating frequency, and mechanical impact is effectively introduced to broaden the working bandwidth. A simulation model of the energy harvester is built to illustrate the energy conversion process. The performance of the energy harvester is experimentally investigated under harmonic excitation with different acceleration levels and frequencies. At an acceleration of 1 g, a maximum peak-to-peak voltage of 370 mV is measured over a wide frequency range of 3-16 Hz, and the root mean square (RMS) output power at the optimal resistance is obtained as 26.7 μW at the excitation frequency of 6 Hz. In addition, the real-time characteristic of the proposed energy harvester is explored by harvesting energy from human motions such as hand shaking, stepping, and jumping. Compared with recent diamagnetic-levitation-based vibration energy harvesters, the harvester can be efficiently operated in an ultralow-frequency, random, and large-amplitude-vibration environment.
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