This paper describes optimum values of an electrical circuit for energy harvesting using a beam and piezoelectric elements. Energy harvesting techniques recover energy from the environment. We target the energy harvesting methods that extract energy from mechanical vibration systems in this research. Vibration energy is usually extracted through electrical circuits using electromechanical transducers such as DC motors and piezoelectric elements. In order to extract energy effectively, these electrical circuits and additional vibration systems must be optimally tuned. The optimum values of an electrical circuit and additional vibration system can be derived based on impedance matching when a vibration source includes only a single excitation frequency; however, in certain cases, vibration sources include several excitation frequencies. The optimum values derived based on impedance matching are not optimum when the vibration source includes several excitation frequencies. Therefore, we additionally investigated the case of random excitation as a representative of such cases in this research. The optimum values for the case of random excitation are also effective for the cases of free vibration including impulse excitation. The governing equations were formulated using equivalent mechanical models in this research. The combination of a beam and a piezoelectric element was used as the piezoelectric energy harvester because the thorough formulation of the governing equations for this configuration was not found in the research literature. The optimum values of the electrical circuit and additional vibration system were derived using the governing equations. The effectiveness of the optimum values was verified through numerical calculations.
2017 The Japan Society of Mechanical Engineers