A linear-element coupled nonlinear energy harvesting system

This paper presents a linear-spring coupled nonlinear energy harvesting system, which contains linear piezoelectric energy harvesters coupled by linear springs. Although every element of the system is linear, the system will present nonlinear characteristics when it is subjected to excitations because of the geometric nonlinearity induced by coupled motions. Three nonuniform cross-section linear harvesters with the same total length and the different thickness are selected to form the proposed system. Based on Euler-Bernoulli beam assumptions and the geometrical relationship among each element, a detailed modeling process of the proposed system is presented. In order to verify the broadband characteristics, the comparison of the proposed system and its linear counterparts is provided. Under harmonic excitations, the proposed system has much better energy harvesting capacity compared with its linear counterparts. What's more, the energy harvesting performance of the proposed system is a little better than its linear counterparts under random excitations. The results demonstrate that the advantage of the proposed system is enhanced along with increased excitation level. In addition, such non-magnetic nonlinear energy harvesting system can be used in the areas where magnets are forbidden, such as inside the human body.