Abstract Rotary electromagnetic generators that have high power density, large power output, and large rotational inertia are increasingly used in vibration energy-harvesting systems. When applied to single-degree-of-freedom (SDOF) systems, it is found that the inertance reduces the system frequency bandwidth. Furthermore, the maximum power output of SDOF systems is limited by the mechanical damping and the maximum allowable stroke. Two-degrees-of-freedom (2DOF) energy-harvesting systems have been proposed in recent years and demonstrated to have larger power output and wider bandwidth compared with SDOF systems. However, a considerable additional physical mass has to be added to an SDOF system to create a 2DOF energy-harvesting system, which may increase the total weight and requires more space. By utilizing the rotational inertia of the electromagnetic generator and a line-to-rotation mechanism as inerter, an inerter-based 2DOF system that requires neglectable additional physical mass is proposed, in which a spring and an inerter are connected in series between the primary mass and the vibration base. Parameters including the mass ratio, the frequency tuning ratio, the spring ratio, and the damping ratio, were optimized for the inerter-based 2DOF system. Optimal specific power with stroke limitation was obtained. A benchmark test using an energy harvesting backpack was done to validate the analysis results. Both analyses and experimental tests show that the inerter-based 2DOF can have larger specific power and larger power-to-stroke ratio compared with its SDOF counterpart. The energy conversion efficiency is also improved. Compared with the conventional 2DOF system, the inerter-based 2DOF system is not only lightweight but also less sensitive to parameter changes.

中文翻译：

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基于惯性的二自由度系统的振动能量收集

摘要 具有高功率密度、大功率输出、大转动惯量的旋转电磁发电机在振动能量收集系统中得到越来越多的应用。当应用于单自由度 (SDOF) 系统时，发现惯性会降低系统频率带宽。此外，单自由度系统的最大功率输出受到机械阻尼和最大允许行程的限制。近年来，人们提出了双自由度 (2DOF) 能量收集系统，并证明与单自由度系统相比具有更大的功率输出和更宽的带宽。然而，必须向单自由度系统添加相当多的额外物理质量才能创建 2DOF 能量收集系统，这可能会增加总重量并需要更多空间。利用电磁发电机的转动惯量和线转机构作为惯性器，提出了一种基于惯性器的2DOF系统，该系统需要可忽略的附加物理质量，其中弹簧和惯性器串联连接在初级质量之间和振动底座。质量比、频率调谐比、弹簧比和阻尼比等参数针对基于惯性的 2DOF 系统进行了优化。获得了具有行程限制的最佳比功率。使用能量收集背包进行基准测试以验证分析结果。分析和实验测试表明，与单自由度相比，基于惰性的 2DOF 可以具有更大的比功率和更大的功率冲程比。能量转换效率也得到提高。