In order to reduce the natural frequency of the piezoelectric vibration energy harvester, improve performance of the piezoelectric vibration energy harvester, and meet the requirements of energy acquisition in the low-frequency vibration environment, a variable-section circular piezoelectric vibration energy harvester is presented. The dynamic model and electromechanical coupling model of variable-section circular piezoelectric vibration energy harvester are established. The main factors affecting the output performance of piezoelectric vibration energy harvester are analyzed. The structure parameters of piezoelectric vibration energy harvester are optimized by orthogonal experiment. An experimental platform is built to test output voltage and output power of piezoelectric vibration energy harvester. The experimental results show that when the number of energy harvester is 4 and the external load is 180KΩ, the parallel output power can reach 0.213mW, which can meet the requirements of micro-power device power supply.
In order to realize 3-dimensional, wide-band vibration energy harvesting in low-frequency and low-amplitude environments, a multi-layer Z-type beam piezoelectric harvester structure is proposed. Nonlinear mass and instabilities of horizontal and longitudinal are introduced by the multi-layer Z-type beam structure. Simulation and experiment results show that when the number of beam layer is 7 and excitation intensity is 0.8 g, there are more than 4 voltage peaks within 5–40 Hz, the maximum voltage is above 16 V, the maximum output power can reach 180 μW, which greatly widens harvesting frequency band. When exciting in horizontal and vertical directions, the maximum voltages peaks are all above 10 V, the number of voltage peaks are all above 5, maximum output powers can reach 108 μW and 53 μW respectively, by which 3-dimensional energy harvesting is verified. Next, the performances of arrays are studied. When the arrays number is 12, excitation intensity reduces to 0.2 g, nearly 90% of the voltage response amplitudes for parallel arrays within 15–40 Hz are above 4 V, almost all the voltage response amplitudes for series arrays are above 5 V within 17–40 Hz, even response amplitudes are all above 10 V within 23–33 Hz. The maximum output power generated by parallel arrays is up to 864.5 μW. So, wide-band 3-dimensional vibration energy harvesting for low amplitude environment is realized by multi-layer Z-type vibration energy harvester. Finally, the feasibility that wireless switch could be powered by the multi-layer Z-type vibration energy harvester parallel arrays from low-frequency and low-amplitude environment is verified.
Because the mine is damp and dark, it is not easy to detect the rigid tank channel’s structural failure directly. Therefore, we judged the tank channel’s surface condition by detecting the magnitude of the vibration displacement of the lifting container. In our study, we used a laser vision system to measure the structural vibration displacement. In order to accurately segment the laser spot information from the vibration image, we proposed an approach that links the relationship between the gray value of the area adjacent to the threshold point and the background’s gray value to the target in the image. We used MCE to evaluate the segmentation effect of threshold segmentation and verified the improved algorithm’s accuracy by detecting the pixel centroid of laser spots. Results show that the improved algorithm in our study has the best threshold segmentation effect, the error classification can be close to 0.0003, and the minimum deviation of the obtained vibration displacement is close to 0.1 pixels, which can realize the accurate extraction of the vibration signal of the vertical shaft tank. The novelty of this method lies in the accurate threshold segmentation and noise reduction processing of the laser speck vibration image under various interference environments in the operation of the mine hoisting system and the accurate acquisition of vibration signals. The research work provides a basis for the accurate evaluation of mechanical faults of automation technology.
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