Recent researchers have focused on scavenging energy from ambient vibrations or movements by using piezoelectric energy harvesters. Rotary movements are regarded as potential energy resources as they can be utilized in windmills or turnstile gates in stations. This study aims to study the vibrational interference that could occur in the typical rotational plucking energy harvester with circularly distributed plectra on the outer ring plucking on the circular array of multiple piezoelectric cantilevers on the inner hub. In this structure, the plucking frequency will be increased to times of the input rotational frequency since multiple plectra will participate in the deflection of each piezoelectric cantilever for one rotational cycle. A model is established based on the Hamilton’s principle for the basic electromechanical part and the Hertzian contact theory for the solution of plucking force. Based on the developed model, the simulation results of the system responses of the rotational plucking energy harvester (RPEH) in a wide rotational frequency range reveal that the system may be suppressed by the vibrational interference such that the energy output is restricted as the rotational frequency is increased. The induced plucking force has also been plotted to reproduce the dynamic contact process and investigate the variation of the force amplitude with rotational frequency. An overall investigation of the energy harvesting performance also indicates the influence of the vibrational interference on the RPEH structure.
Non-harmonic excitations are widely available in the environment of our daily life. We could make use of these
excitations to pluck piezoelectric energy harvesters. Plucking piezoelectric energy harvesting could overcome the
frequency gap and achieve frequency-up effect. However, there has not been a thorough analysis on plucking
piezoelectric energy harvesting, especially with good understanding on the plucking mechanism. This paper is aimed to
develop a model to investigate the plucking mechanism and predict the responses of plucking piezoelectric energy
harvesters under different kinds of excitations. In the electromechanical model, Hertzian contact theory is applied to
account for the interaction between the plectrum and piezoelectric beam. The plucking mechanism is clarified as a
cantilever beam impacted by an infinitely heavy mass, in which the multi-impact process prematurely terminates at
separation time. We numerically predict the plucking force, which depends on piezoelectric beam, Hertzian contact
stiffness, overlap area and plucking velocity. The energy distribution is investigated with connected resistor.
Impact excitation is common in the environment. Impact piezoelectric energy harvesting could realize frequency up-conversion. However, the dissipation mechanism in impact piezoelectric energy harvesting has not been investigated so far. There is no comprehensive model to be able to analyze the impact piezoelectric energy harvesting thoroughly. This paper is aimed to develop a generalized model that considers dissipation mechanism of impact piezoelectric energy harvesting. In this electromechanical model, Hertzian contact theory and impact dissipation mechanism are identified as constitutive mechanisms. The impact force is compared and the energy distribution is analyzed so that input energy corresponds to impact dissipated energy, structural damping dissipated energy and harvested electrical energy. We then nondimensionalize the developed model and define five dimensionless parameters with attributed physical meanings, including dimensionless parameters of impact dissipation, mass ratio, structural damping, electromechanical coupling, and electrical load. We conclude it is more accurate to consider impact dissipation mechanism to predict impact force and harvested energy. The guideline for improving harvested energy based on parametric studies of dimensionless model is to increase mass ratio, to minimize structural damping, to maximize electromechanical coupling, to use optimal load resistance for impedance matching, and to choose proper impact velocity .