International Journal of Applied Electromagnetics and Mechanics - Volume 65, issue 4

Authors: Meng, Kai | Gu, Yong | Ma, Jianhui | Liu, Xidong | Geng, Xiangqian | Liu, Yuxi | Liu, Xuhe | Zhang, Haoming | Shao, Fengxiang

Article Type: Research Article

Abstract: In this study, a novel negative stiffness spring is developed. The developed spring possesses the characteristics of the controllable stiffness and can be employed in vibration isolation system with a low resonance frequency. The controllable electromagnetic negative stiffness spring (CENSS) is obtained by the coaxial permanent magnets (PMs) and the circular current-carrying coils. The stiffness control is accomplished by changing the current in the coils. Furthermore, the mathematical model of CENSS is established, based on the filament method. According to the model, the relationship between the exciting current and the axial stiffness is obtained. Moreover, the influence of the structural …parameters of CENSS on the magnetic force and the stiffness is analyzed. The results demonstrate that the thickness of PMs and the coils have the ability to adjust the range of the negative stiffness. Finally, performance experimental study of CENSS in the stiffness domain is carried out under different exciting currents and thicknesses. The experimental results have shown a good agreement with the model. It demonstrates that the performance of negative stiffness in CENSS can be controlled efficiently by the exciting current and optimized by the thickness. Show more

Keywords: Magnetic stiffness, electromagnetic springs, negative stiffness, vibration isolation

DOI: 10.3233/JAE-201561

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 65, no. 4, pp. 781-802, 2021

Authors: Liu, Chuan | Chen, Renwen | Zhang, Yuxiang | Wang, Liping | Qin, Jinchang

Article Type: Research Article

Abstract: Converting persistent and renewable wave energy into electricity has been studied in recent years. This research develops a novel fully floating three-body direct-drive wave energy converter (DD-WEC) prepared for the research of the multi-body DD-WEC. Its prototype consists of three floating bodies, but both three bodies act as buoys to extract the wave energy, not just a body. And the relative motion of the buoys induces the voltage in Halbach array permanent magnet linear generators coils. Its feasibility is investigated theoretically by analyzing the dynamics of motion of the floating buoys. As a result, parametric design of the WEC is …achieved. The load performance of the DD-WEC is investigated by using the Simulink, and it can be found that the relative displacements between buoys are different. Then, the electromagnetic power of the proposed WEC is much higher compared to a two-body DD-WEC by using numerical simulation Finally, the DD-WEC prototype is manufactured and tested in the wave tank. The results show that the WEC can produce the most electricity for the case with the wave period of 1.6 s, and the maximum voltage reaches 14.2 V, which is consistent with the simulation results. The results show that the proposed DD-WEC is well suited for wave energy conversion. Show more

Keywords: Three-body, direct-drive wave energy converter, Halbach permanent magnet linear generator, electromagnetic power

DOI: 10.3233/JAE-201566

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 65, no. 4, pp. 803-818, 2021