“…Among them, optimizing the external circuit (Huang et al, 2019), using of the structural stability (Łygas et al, 2019) and nonlinearity (Litak et al, 2010; Wang and Inman, 2013; Yang et al, 2013; Zhao et al, 2013), and other methods were explored to improve energy harvesting performance. Particularly, different types of energy harvesters with broadband dynamic characteristics were designed and tested (Azadeh-Ranjbar et al, 2020; Kim, 2020; Machů et al, 2020; Wang et al, 2020).…”