Enhancing the performance of backpack energy harvester using nonlinear inerter-based two degrees of freedom design

• Published in: Smart materials and structures Vol. 29; no. 2; pp. 25007 - 25017
• Main Authors: Liu, Mingyi, Tai, Wei-Che, Zuo, Lei
• Format: Journal Article
• Language: English
• Published: IOP Publishing 01.02.2020
• Subjects: energy harvesting; mechanical motion rectifier; nonlinear inerter; stroke limit; two degrees of freedom
• ISSN: 0964-1726; 1361-665X
• DOI: 10.1088/1361-665X/ab5cf2

In many vibration energy harvesting systems, the vibration stroke is limited by the physical space constraint. Furthermore, when using an oscillating backpack to harvest energy from human walking, the stroke is of great concern to human comfort. In this paper, a nonlinear inerter-based two degrees of freedom (2DOF) energy harvesting system that can harvest large power at a limited stroke is proposed. The inerter nonlinearity is achieved by adding a mechanical motion rectifier (MMR) to the system. The design and modeling of the nonlinear inerter-based 2DOF energy harvesting device are explained in detail. The mechanical system is then converted to an analogous electrical model for simulation and optimization. Optimal power is achieved while the stroke is limited to a desired value. It is shown that the maximum stroke over the working frequency range can be reduced 32% after the introducing the MMR to this linear 2DOF system. The maximum stroke over the working frequency range can be further reduced while the power is not significantly compromised by using difference electrical impedance. Although the maximum average power output is decreased compared with the linear 2DOF system, the nonlinear inerter-based 2DOF system has a larger power output compared with the optimal single degree of freedom (SDOF) system with almost the same maximum stroke. Finally, the modeling and simulation results are validated by experiments. The nonlinear inerter-based 2DOF design can be applied to vibration energy harvesting systems to obtain large power with limited stroke.