Enhanced broadband 2-DOF rotational energy harvester incorporating centrifugally stiffened and softened beams

This study proposes a two-degree-of-freedom (2-DOF) rotational bistable piezoelectric energy harvester that integrates a centrifugally stiffened beam with a centrifugally softened beam. An electromechanically coupled nonlinear dynamic model is established based on the extended Hamilton’s principle, and the dynamic responses and electrical output characteristics are investigated through numerical and experimental studies. The results show that the complementary centrifugal tuning characteristics of the two beams produce two dominant response regions and a corresponding dual-peak broadband electrical response over the investigated rotational-frequency range up to 125 rad/s. Compared with a typical one-degree-of-freedom (1-DOF) rotational bistable harvester, the proposed 2-DOF design expands the frequency-swept displacement-response bandwidth by 112.5%. Experimental results further verify the predicted evolution of motion states and the dual-peak voltage output. Using an average-power threshold of 1 μW, the experimentally validated effective power band extends continuously from approximately 40 to 125 rad/s. In addition, a self-powered TPMS demonstration confirms that the harvested rotational energy can be rectified and regulated to drive a commercial wireless sensor. The proposed design offers a practical strategy for broadening the operational bandwidth of rotational piezoelectric energy harvesters for tire-mounted self-powered sensing applications.