To realize the harvesting of energy generated by human movement, in this study, a piezoelectric–electromagnetic composite was designed for harvesting the energy generated by low-frequency human motion is designed by combining the principle of power generation and electromagnetic energy conversion of polyvinylidene fluoride (PVDF) piezoelectric materials. First, the structure and working principle of the piezoelectric–electromagnetic composite energy trap were designed and analyzed. Next, the system dynamics model of piezoelectric–electromagnetic coupling power generation was established, and the main influencing factors of the composite energy trap were derived. Moreover, the influence of PVDF piezoelectric materials with different size parameters on the output voltage and the influence of the frequency of the moving permanent magnet on electromagnetic power generation were analyzed. Finally, the prototype was constructed and tested. The results revealed that the output voltage of the piezoelectric–electromagnetic composite energy trap placed horizontally is higher than that of the composite energy trap placed vertically at step frequencies of over 90 steps/min, and the maximum output voltage is 25.6 V at the step frequency of 140 steps/min. The electric energy generated by the composite energy trap can supply power to low-power electronic devices, thus demonstrating the feasibility of collecting human-motion energy for power generation.
The purpose of this paper is to use the principle of hydraulic amplification and design a piezoelectric drive-based hydraulically amplified flexible Braille contact device with good performance output. In this paper, the structure and working principle of the Braille contact device are described, and the theoretical analysis and parametric design of the hydraulic amplification unit are carried out. The influence relationship between the displacement amplification and diameter and height of the reservoir are obtained by using MATLAB simulation analysis, whereas the output displacement of the piezoelectric vibrator and the flexible film under different driving voltages is measured by using a laser micrometer. Subsequently, the experiments are consistent with the theoretical analysis, and the correctness of the theoretical analysis is verified. Finally, experimental tests of the system are implemented. The results suggest that the displacement amplification ratio is 4.16, and the contact displacement formed by the flexible film is 0.226 mm. Thus, the requirements of the touch sensitivity standard for the blind are satisfied when the reservoir diameter is 20 mm and the reservoir height is 3 mm. The filling water is 7.5 ml, and the resonance frequency is 317.5 Hz. This study proves that constructing a Braille bump device in this way is feasible as well as effective.
With the advantages of low cost, universal applicability, and in situ detection, the conic invariant of the tested aperture diameter was obtained by ellipse geometric fitting on the aperture surface. The world coordinate system was established, and the transformation relationship between the world coordinate system and the camera coordinate system was obtained by the calibration. The improved Candy algorithm and coordinate transformation relationship could be used to project the sub-pixel coordinates of the aperture edge onto the aperture surface. Then, the ellipse geometric fitting was performed on the aperture edge curve surface to obtain the conic invariant. Finally, the conic invariant was used to measure the aperture diameter on the test bench.
In order to investigate the optimal power generation performance of piezoelectric materials, a spin-magnetic piezoelectric generator was designed and the relationship between output voltage and speed and external force was derived through theoretical analysis. The maximum deformation and resonant frequency of the piezoelectric oscillator under magnetic drive are derived from simulation analysis. Finally, the relationship between output voltage and magnet size, distance between two magnets, and speed was tested experimentally, and the experimental data agreed with the theoretical analysis. The results show that when the speed is 312 r/min, magnet pitch is 12 mm, and magnet size is 10 mm ∗ 35 mm ∗ 4, the maximum output voltage is 54 V. This can meet the power supply needs of micro and small electronic products.
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