• Analysis and design of a nonlinear vibration-based energy harvester - a frequency based approach

      Uchenna, Diala; Simon, Pope; Lang, Zi-Qiang; University of Sheffield (IEEE, 2017-08-24)
      The benefits of nonlinear damping in increasing the amount of energy (power) harvested by a vibration-based energy harvester (VEH) has been reported where it was revealed that more energy can be harvested using nonlinear cubic damping when compared to a VEH with linear damping. As has been reported, this only occurs when the base excitation on the VEH, at resonance, is less than the maximum base excitation. A maximum harvester base excitation results in a maximum distance the harvester mass can move due to its size and geometric limitations. The present study is concerned with the analysis and design of a VEH using a nonlinear frequency analysis method. This method employs the concept of the output frequency response function (OFRF) to derive an explicit polynomial relationship between the harvested energy (power) and the parameter of the energy harvester of interest, i.e. the nonlinear cubic damping coefficient. Based on the OFRF, a nonlinear damping coefficient can be designed to achieve a range of desired levels of energy harvesting. It is also shown that using the OFRF the harvester throw (the displacement of the mass of the harvester), can be predicted using the designed damping coefficient.
    • Geometric nonlinear damper design — A frequency based approach

      Uchenna, Diala; Okafor, K.C.; Zi-Qiang, Lang; University of Sheffield (IEEE, 2018-02-08)
      In this study, the vibration transmissibility of a single-degree-of-freedom (SDOF) with a linear damper having a configuration perpendicular to a linear vertical spring is analyzed using a nonlinear frequency analysis method. The concept of the output frequency response function (OFRF) is employed to derive an explicit polynomial relationship between the system output response (relative displacement of the mass) and the parameter of interest which is the nonlinear damping coefficient. With the derived OFRF polynomial, various damping parameters were designed for desired output responses.