Maximization of the harvested power from piezoelectric bimorphs with multiple electrodes under dynamic excitation

Maximization of the harvested energy from piezoelectric bimorphs has been the objective of many researchers in the past few years. Most of the previous work focused on bimorphs covered with a single pair of electrodes, leading to a great loss of generated power due to charge cancellation from areas with opposite strains. In this paper, we assume the bimorph is covered with multiple pairs of electrodes to overcome the problem of charge cancellation. We focus on circular bimorphs subject to base excitation at different frequencies. We also assume that the capacitances attached to the electrodes are controllable and can be optimized to maximize the power output at a given excitation frequency. Moreover, we change the topology of the bimorph by making its thickness vary with the radius of the bimorph. Numerical examples show that the harnessed power can be maximized by increasing the capacitance of anti-nodal elements while decreasing that of nodal elements. Also, decreasing the thickness of piezoelectric layers at anti-nodal elements allows more straining and hence the generation of more power. It is shown that the compatibility of the topology of the piezoelectric bimorph with the shape of the second axisymmetric mode yields more power compared with its compatibility with the first mode.