[4] [4] YILDIRIM T, ZHANG J, SUN S, et al. Design of an enhanced wideband energy harvester using a parametrically excited array ［J］. J Sound Vib, 2017, 410: 416-428.

[5] [5] ALDRAIHEM O J, BAZ A. Energy harvester with a dynamic magnifier ［J］. J Intell Mater Syst Struct, 2011, 22(6): 521-530.

[6] [6] ABDELKEFI A, NAYFEH A H, HAJJ M R, et al. Energy harvesting from a multifrequency response of a tuned bending-torsion system ［J］. Smart Mater Struct, 2012, 21(7): 075029.

[7] [7] ABDELMOULA H, SHARPES N, ABDELKEFI A, et al. Low-frequency zigzag energy harvesters operating in torsion-dominant mode ［J］. Appl Energy, 2017, 204: 413-419.

[9] [9] ERTURK A, INMAN D J. A distributed parameter electromechanical model for cantilevered piezoelectric energy harvesters ［J］. J Vib Acoust, 2008, 130(4): 041002.