Hong-Xiang Zou

A broadband compressive-mode vibration energy harvester enhanced by magnetic force intervention approach

This letter presents a magnetic force intervention approach to enhance the performance of a broadband compressive-mode vibration energy harvester. The magnetic force intervention promotes a magnetic oscillator to vibrate within a desired work area. A magnetic stator drives the magnetic oscillator away by employing a repulsive magnetic force, while two magnetic stoppers (upper and lower magnets) limit the unwanted large displacement of the magnetic oscillator and drive it back toward the magnetic stator. Numerical and experimental results show that the performances of a compressive-mode bistable vibration energy harvester under low-frequency (<10 Hz) weak excitation can be significantly enhanced by using magnetic stoppers. Moreover, the magnetic force that acting against the magnetic stopper can also generate electricity.

Tunable rotating-mode density measurement using magnetic levitation

In this letter, a density measurement method by magnetic levitation using the rotation mechanism is presented. By rotating the entire magnetic levitation device that consists of four identical magnets, the horizontal centrifugal force and gravity can be balanced by the magnetic forces in the x-direction and the z-direction, respectively. The controllable magnified centripetal acceleration is investigated as a means to improve the measurement sensitivity without destabilization. Theoretical and experimental results show that the density measurement method can be flexible in characterizing small differences in density by tuning the eccentric distance or rotating speed. The rotating-mode density measurement method using magnetic levitation has prospects of providing an operationally simple way in separations and quality control of objects with arbitrary shapes in materials science and industrial fields.

Y-type three-blade bluff body for wind energy harvesting

A three-blade bluff body for wind energy harvesting is proposed and designed. The bluff body with a Y-type cross-section is formed by three rigid thin blades and fixed at the free end of a piezoelectric cantilever beam. Simulations and experiments confirmed that this three-blade structure can achieve much higher energy output than a square prism. The output voltages of horizontal harvesters with different half-angles between the two front blades of the bluff body were measured first. The half-angle dramatically affected the performance of the energy harvester. Half-angles between 60° and 80° are found to be the optimal values for generating a high output voltage. In addition, the performance of the harvester can be enhanced when the length ratio of the rear blade to the front blade is in the range of 4/3–5/3. Interestingly, the output voltage of the vertical three-blade harvester was higher than that of the horizontal one and the optimal half-angle in this case was also between 60° and 80°.A three-blade bluff body for wind energy harvesting is proposed and designed. The bluff body with a Y-type cross-section is formed by three rigid thin blades and fixed at the free end of a piezoelectric cantilever beam. Simulations and experiments confirmed that this three-blade structure can achieve much higher energy output than a square prism. The output voltages of horizontal harvesters with different half-angles between the two front blades of the bluff body were measured first. The half-angle dramatically affected the performance of the energy harvester. Half-angles between 60° and 80° are found to be the optimal values for generating a high output voltage. In addition, the performance of the harvester can be enhanced when the length ratio of the rear blade to the front blade is in the range of 4/3–5/3. Interestingly, the output voltage of the vertical three-blade harvester was higher than that of the horizontal one and the optimal half-angle in this case was also between 60° and 80°.

Asymmetry bistability for a coupled dielectric elastomer minimum energy structure

In this paper, a novel design of asymmetry bistability for a coupled dielectric elastomer minimum energy structure (DEMES) is presented. The structure can be stable both in the stretched and curved configurations, which are induced by the geometry coupling effect of two DEMESs with perpendicular bending axes. The unique asymmetry bistability and fully flexible compact design of the coupled DEMES can enrich the active morphing modes of the dielectric elastomer actuators. A theoretical model of the systems strain energy is established to explain the bistability. Furthermore, a prototype is fabricated to verify the conceptual design. The experimental results show that when the applied voltage is below a critical transition one, the structure behaves as a conventional DEMES, once the applied voltage exceeds the critical voltage, the structure could change from the stretched (curved) configuration to the curved (stretched) configuration abruptly and maintain in a new stable configuration when the voltage is removed. A multi-segment structure with the coupled DEMES is also presented and fabricated, and it displays various voltage-actuated morphings. It indicates that the coupled DEMES and the multi-segment structures can be useful for the soft and shape-shifting robots.