| The Internet of Things(Io T)technology has facilitated the development of intelligent machinery,smart manufacturing,and smart ships.However,the demand for distributed wireless sensor nodes(WSNs)has increased significantly due to the interconnectedness of billions of nodes.Although the energy consumption of individual sensors has been reduced to the milliwatt(m W)or microwatt(μW)level,the sheer quantity and wide distribution of WSNs pose significant challenges for their power supply.Currently,battery-powered systems are commonly used,but they have limitations in terms of operational lifespan,replacement costs,and environmental pollution.Harvesting ambient energy to provide in-situ power supply is an effective approach to address this challenge.Meanwhile,mechanical vibrations are prevalent and can provide continuous output,making vibration energy one of the most promising micro/nano energy sources for addressing the aforementioned challenges.Among various micro/nano energy harvesting methods,the Triboelectric Nanogenerator(TENG)stands out due to its high output and adaptability,making it highly promising for in-situ power supply to low-power WSNs.Therefore,research on vibration energy harvesting based on TENG holds great significance in promoting the development of intelligent machinery,smart manufacturing,and intelligent monitoring in the era of Io T.The freestanding layer mode TENG has the advantages of setting adaptability and wide application range among different working modes of TENG,and it is more superior in mechanical vibration energy harvesting.Despite significant progress in freestanding layer mode vibration energy TENG research,further in-depth investigation is required to comprehend the vibration characteristics of the freestanding layer under forced vibration and its inherent impact on power generation performance.To address this gap,this study systematically investigates various mechanical vibration energy sources,focusing on two crucial processes: the coupling of mechanical vibration energy as kinetic energy into the device and the electromechanical conversion within the device.The study includes the design of configurations,dynamic analysis,coupled analysis of vibration and power generation characteristics,and demonstration of energy harvesting capabilities in order to reveal the energy conversion mechanism of vibration energy TENG.The primary research contents of this thesis can be summarized as follows:(1)Based on an analysis of the fundamental model of vibration energy conversion and the working principles of TENG,this thesis proposes the design of freestanding layer TENG to accommodate various vibration excitation conditions.A theoretical model is developed specifically for the power generation and an electromechanical conversion equivalent model is constructed.To explore the influence of critical factors on the vibration characteristics and output performance of the vibration energy TENG,a coordinated testing system is designed and assembled.This system utilizes an exciter and a linear motor to enable simultaneous evaluation of vibration and power generation characteristics.The aforementioned work provides a solid foundation for subsequent research endeavors.(2)On basis of the aforementioned theoretical analysis,a harmonic silicone rubber TENG(HSR-TENG)specifically designed for fixed-frequency mechanical vibration is proposed.A dynamic model is developed to analyze the vibration characteristics,key influencing factors,and vibration modes of the flexible belt.It is found that HSR-TENG exhibits superior output performance operating in the first mode.To investigate the main factors and their interaction effects,an orthogonal experimental design is employed.Through the verification of these effects,the "extremely significant" factors that influence the first mode resonance frequency of flexible belt are determined,leading to a matching principle to adapt to excitation.The optimal configuration is determined by surface micro-nano treatment and studying the influence of structural parameters.The study also reveals the mechanism of the effect of vibration intensity on the output performance and bandwidth of the HSR-TENG.Increasing the vibration intensity from 0.4 to 3 leads to an approximate 100% improvement in the output performance.When the vibration intensity is kept constant,the output performance initially increases and then decreases,while the output bandwidth can be expanded from 3Hz to 19 Hz by increasing the vibration intensity from 0.4 to 3.By adjusting the matching frequency to 24 Hz,the output power density reaches 153.9 W/m~3.Furthermore,successful in-situ power supply for a commercial temperature sensor is achieved under the vibration excitation of an air compressor.(3)Building upon research on resonant TENG,a novel non-resonant Bouncing Ball-based TENG(BB-TENG)is developed and comprehensively investigated regarding its vibration and power generation characteristics under variable-frequency excitation.The motion control equations are derived,and the factors influencing its Lyapunov stability are examined.Subsequently,the vibration processes,including bouncing,chaos,critical-contact,and wellcontact,are analyzed using dynamic simulations and high-speed images.The study reveals that the ball’s bouncing depends on the vibration intensity,while other vibration characteristics are determined by the electrode spacing and excitation conditions.Furthermore,it is discovered that the critical contact exhibits a negative correlation with the electrode spacing and a positive correlation with the vibration excitation.The results of investigating excitation and structural parameters on vibration and power generation performances show that BB-TENG exhibits stable voltage output and linearly increasing current with frequency after critical-contact,demonstrating excellent variable-frequency energy harvesting capability.In addtion,the output performance increases with larger ball diameter and electrode spacing.A BB-TENG with ball diameter of 10.5 mm achieves power density of 3 W/m~3 at 35 Hz and 2.5 mm excitation.The voltage signal,obtained through fast Fourier transform,enables vibration frequency monitoring within the range of 10-50 Hz with an error less than 0.03%.Moreover,the power density of the BB-TENG array is increased to 59.783W/m~3,enabling in-situ power supply for a CNTs-PPy ammonia leakage sensor and wireless transmission module by harvesting mechanical vibration energy from a marine diesel engine.(4)In accordance with above research,the study designs a drill pipe-embedded annular type TENG(AT-TENG)specifically adapting to vibrations with combination of flexible and non-resonant characteristics.The flexible deformations of the silicone ring under vibration exhibits excellent durability and enables effective vibration energy harvesting.By analyzing the vibration excitation conditions of AT-TENG,the frequency and amplitude range are determined.Study on the impact of structural parameters on power generation identifies the optimal configuration.Analysis of its vibration characteristics using high-speed images reveals that as the frequency and amplitude increase,the enlarged deformations of the ring result in larger contact area with electrodes,thereby enhancing the output performance.AT-TENG demonstrates a linear positive correlation with both frequency and amplitude,achieving an output voltage of 375 V under a vibration excitation of 5 Hz and 70 mm through synergistic testing of vibration and power generation characteristics.It achieves a minimum output of 65 V within 360° range,indicating arbitrary direction vibration energy harvesting potential.ATTENG attains a power density of 63.7 W/m~3 with an optimal matching load of 400 MΩ.Its capacitance charging characteristics,in-situ power supply for commercial sensors,and precise frequency sensing showcase its enormous potential in vibration energy harvesting and selfpowered vibration sensing.In summary,the research findings presented in this thesis contribute to the enrichment of vibration energy conversion mechanisms and provide a new perspective for innovating in-situ power supply methods for low-power WSNs under various vibration excitation conditions. |
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