Haigang Tian

Vibration-related issues are common causes of failure in precision machines, and energy harvesting techniques can help mitigate harmful vibrations and recycle waste energy. This Letter introduces an electromagnetic energy harvester utilizing a quasi-zero stiffness mechanism to achieve simultaneous vibration isolation and energy harvesting. The system utilizes mutually exclusive magnets to generate positive stiffness and flexible bending beams to offer negative stiffness, which counterbalances each other to realize quasi-zero stiffness. Physical prototypes were fabricated, and their vibration isolation and energy harvesting performance were assessed under various magnet distances and excitation conditions. Experimental results validate that the proposed system achieves both vibration isolation and energy harvesting. It exhibits outstanding vibration isolation performance when the frequency exceeds 5 Hz. Notably, the magnet distance significantly affects the energy harvesting performance: compared to the 37 mm configuration, adjusting the magnet distance to 41 and 39 mm increased the power output by 54.9% and 31.7%, respectively. This study lays an important foundation for advancing integrated vibration isolation and energy harvesting technologies.

Current wind tunnels possess a large space volume and high manufacturing cost, which are not suitable for investigating micro energy harvesters. This paper aims to design and fabricate a small, portable and low-speed wind tunnel for energy harvesting. A wind tunnel structure was first designed, a finite element analyses is then utilized to obtain the airflow velocity and turbulence intensity at the testing section, and the influence of the structural parameters of the wind tunnel on the flow field performance is finally investigated to achieve better performance. An experimental prototype of the wind tunnel was fabricated to verify the simulation results. Results demonstrated that the distribution uniformity and average turbulence intensity at the test section decrease first and then increase with the increase of both the diffuser and contraction lengths. The rectifying and damping effect of the honeycomb increase with increasing porosity and thickness. When the diffuser and contraction lengths are 850 mm and 480 mm, respectively, a better distribution uniformity and a lower turbulence intensity can be achieved. Experimental results were in good agreement with the simulation values. The maximum airflow velocity can reach up to 24.74 m/s, and the minimum error was only 1.23%. The designed wind tunnel achieved low-speed, small, portable and stable functions. This work provides an important guidance for further investigating the piezoelectric energy harvesting.