An experimental and theoretical study of an omnidirectional pendulum energy harvester

  • Philipp Sommermann

Student thesis: Doctoral Thesis

Abstract

The spherical pendulum is mathematically well described and different scholars contributed to the topic in the past. Nevertheless, in the field of pendulum-based energy harvesting the interoperation of a simple pendulum is prevailing over the spherical pendulum. The energy harvester’s application areas, and probably its overall capacity, may be limited as a result of this reduction in degrees of freedom. To that end, this work presents the omnidirectional energy harvester that operates independently of the direction of excitation. The numerical evaluation of the energy harvester observes quasiperiodicity and chaotic dynamics for different forcing conditions but with an increase in the power take-off the dynamics of the energy harvester become generally more periodic. The dynamics of the system are highly dependent on the excitation frequency, excitation amplitude, damping ratio, and power take-off torque. In the experimental analysis two power take-off modes of different levels are compared. In the frequency responses the softening characteristics of the spherical pendulum are observed. Additionally, excitation frequency up- and down-sweeps are included to observe the broadening of the operational range of the energy harvester. Interestingly the excitation frequency up-sweep shows a large increase in the operational region meaning the spherical pendulum shows hardening characteristics. An optimal operational point is defined close to the maximum deflection in the upper nonlinear jump region. For the comparison of the numerical and experimental results the numerical results undergo a simple trigonometric transformation. With an adaption of the excitation amplitude the numerical results show the main characteristics of the experimental results including the hardening effect during the excitation frequency up-sweep of the experiments.
Date of Award24 Jan 2023
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde
SupervisorMatthew Cartmell (Supervisor) & Haofeng Chen (Supervisor)

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