【作者】 张兰；

【导师】 彭艳；

【作者基本信息】 上海大学 ， 机械电子工程， 2023， 硕士

【摘要】 随着科技飞速发展,低功耗电子产品的应用愈发广泛,供能需求与日俱增。但持续供能成为限制其发展的短板。振动俘能技术可将环境中储量丰富的振动能转换为电能,有望满足低功耗电子产品的供能需求。电磁俘能器作为主流的振动能转换装置之一,由于内阻低、输出电流大、技术成熟度高等优势得到广泛应用。但电磁俘能器仍面临体积严重限制输出功率和带宽窄的困境。幅值截断现象可拓宽电压带宽,有望解决带宽窄的难题,但严重降低电压幅值。因此提升电磁俘能器的功率密度(输出功率与体积的比值)至关重要。本文以直线电磁俘能器为研究对象,以局部优化系统参数进而提升功率密度为研究点,主要围绕线圈连接方式、导线截面积、冲击距离三个因素展开研究。与此同时,探究了激励加速度、系统阻尼比、刚度比、间距等参数对输出特性的影响。主要研究工作如下:第一,同等体积下,以线圈连接方式为变量,阐述了连接方式与功率密度的制约关系。基于ANSYS平台搭建仿真模型和等效电路,比较了8种连接方式下的输出功率。结果表明,非对称电路结构降低了输出功率。功率密度随连接方式的变化趋势与输出功率相同。第二,同等体积下,以导线截面积为变量,阐述了导线截面积对功率密度的影响。建立了基于一般线性系统的直线电磁俘能器的机电耦合模型,比较了9种导线截面积对输出功率的影响,有限元仿真验证了理论分析的趋势。结果表明,随着导线截面积持续增大,即线径从0.1 mm增大至0.5 mm,输出功率呈先增大后减小的趋势,线径为0.12 mm时输出功率最大。功率密度随导线截面积的变化趋势与输出功率相同。第三,以冲击距离为变量,阐述了冲击距离对直线电磁俘能器幅值截断现象的影响;设计了基于阶段线性系统的样机构型并构建其等效模型;用龙格库塔法和平均法解析了不同阶段的幅频特性曲线。结果表明,在[0,5]的无量纲频率区间内,减小阻尼比和增大刚度比拓宽了带宽并保持较高的幅值,减小间距在拓宽带宽的同时降低了幅值。在[15 Hz,25 Hz]的实际频率区间内,增大冲击距离,幅值截断现象减弱,即电压带宽减小,幅值增大。第四,以冲击距离为变量,阐述了冲击距离与直线电磁俘能器功率密度的制约关系;基于有限元仿真分析了冲击距离对电压的影响规律;制造样机并搭建实验平台开展扫频实验、驻频实验、阻抗匹配实验和充电实验,验证了理论推导和有限元仿真结果。结果表明,随着冲击距离持续增大,即弹簧长度从5 mm增大至40 mm,幅值截断现象减弱,功率密度先增大后减小,当弹簧长度为30 mm时,在10 Hz,1.0g(g表示重力加速度,g=9.8 m/s~2)的激励条件下,外部负载为383Ω时,直线电磁俘能器的功率密度达到最大值2.358 m W/cm~3。更多还原

【Abstract】 With the rapid development of science and technology,the application of low-power electronic products has become more widespread,and the demand for energy supply is increasing.But continuous energy supply has become a shortcoming limiting the development of low-power electronic products.Vibration-based energy harvesting technology can convert abundant vibration energy in the environment into electric energy,which is expected to meet the energy supply requirements of low-power electronic products.As a mainstream vibration energy conversion device,electromagnetic energy harvesters have been widely used due to low internal resistance,large output current,and high technical maturity.However,the research of electromagnetic energy harvesters still confronts the problem of volume seriously limiting the output power and narrow bandwidth.The amplitude truncation phenomenon can broaden the voltage bandwidth and is expected to solve the narrow bandwidth,but it seriously reduces the voltage amplitude.Therefore,improving the power density(ratio of the output power to volume)is urgent.This thesis takes the linear electromagnetic energy harvester as the research object and takes the local optimization of the system parameters to improve power density as the research point.It mainly focuses on three parameters:coil connection mode,wire cross-sectional area,and impact distance.Meanwhile,the parameters of excitation acceleration,system damping ratio,stiffness ratio,spacing are explored.The main research work is as follows:Firstly,we take the coil connection mode as the variable and set the volume of the electromagnetic energy harvester as a constant.The restriction relationship between the coil connection mode and power density is expounded.The simulation model and equivalent circuit are built based on the ANSYS platform,and the output power of 8connection modes is compared.The results show that the asymmetric circuit reduces the power.The variation trend of the power density with connection mode is identical to that of output power due to the same volume.Secondly,we take the wire cross-sectional area as the variable and set volume of the electromagnetic energy harvester as a constant.The restriction relationship between the wire cross-sectional area and power density is expounded.The electromechanical coupling model of linear electromagnetic energy harvester based on a general linear system is established.The output power of nine wire cross-sectional area is compared.The simulation analysis validates the theoretical result.The results show that as the cross-sectional area of the wire continues to increase,that is,the wire diameter increases from 0.1 mm to 0.5 mm,the output power increases and then decreases.The output power reaches the maximum at the wire diameter of 0.12 mm.The variation trend of power density with wire diameter is identical to that of output power.Thirdly,we take the impact distance as a variable.The influence of impact distance on amplitude truncation of electromagnetic energy harvester is expounded.The prototype configuration based on a piecewise linear system is designed and its equivalent model is constructed.The amplitude-frequency characteristic curves of different stages are analyzed by the Runge-Kutta method and the averaging method.The results show that in the dimensionless frequency range of[0,5],reducing the damping ratio and increasing the stiffness ratio increase the bandwidth and maintain a high amplitude,and reducing the initial spacing can broaden the bandwidth but reduce the amplitude.In the actual frequency range of[15 Hz,25 Hz],the longer impact distance weakens the amplitude truncation effect and leads to a narrower voltage bandwidth and a larger voltage amplitude.Fourthly,we take the impact distance as the variable.The restriction relationship between the impact distance and the power density of the linear electromagnetic energy harvester is expounded.The influence of impact distance on voltage is obtained by simulation analysis.The prototypes were manufactured and the experimental platform was built to carry out a series of experiments(sweeping frequency experiment,holding frequency experiment,impedance matching experiment and charging experiment)to verify the theoretical and simulation results.The results show that the amplitude truncation effect weakens when the impact distance increases,that is,spring length increases from 5 mm to 40 mm.When the spring length is 30 mm,the power density reaches a maximum of 2.358 m W/cm~3 at the 383Ωload,and the excitation is 10 Hz,1.0g(g is the gravitational acceleration,g=9.8 m/s~2).更多还原