Vibration energy is becoming a significant alternative solution for energy generation. Recently, a great deal of research has been conducted on how to harvest energy from vibration sources ranging from ocean waves to human motion to microsystems. In this paper, a theoretical model of a piecewise-linear (PWL) nonlinear vibration harvester that has potential applications in variety of fields is proposed and numerically investigated. This new technique enables automatic frequency tunability in the energy harvester by controlling the gap size in the PWL oscillator so that it is able to adapt to changes in excitations. To optimize the performance of the proposed system, a control method combining the response prediction, signal measurement and gap adjustment mechanism is proposed in this paper. This new energy harvester not only overcomes the limitation of traditional linear energy harvesters that can only provide the maximum power generation efficiency over a narrow frequency range but also improves the performance of current nonlinear energy harvesters that are not as efficient as linear energy harvesters at resonance. The proposed system is demonstrated in several case studies to illustrate its effectiveness for a number of different excitations.
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Vibration Energy Harvester With Piecewise Linear Nonlinear Oscillator and Controllable Gap Size
Recently, vibration energy harvesting has been seen as a viable energy source to provide for our energy dependent society. Researchers have studied systems ranging from civil structures like bridges to biomechanical systems including human motion as potential sources of vibration energy. In this work, a bench-top system of a piecewise-linear (PWL) nonlinear vibration harvester is studied. A similar idealized model of the harvester was previously looked at numerically, and in this work the method is adjusted to handle physical systems to construct a realistic harvester design. With the physically realizable harvester design, the resonant frequency of the system is able to be tuned by changing the gap size between the oscillator and mechanical stopper, ensuring optimal performance over a broad frequency range. Current nonlinear harvester designs show decreased performance at certain excitation conditions, but this design overcomes these issues while also still maintaining the performance of a linear harvester at resonance. In this investigation, the system is tested at various excitation conditions and gap sizes. The computational response of the resonance behavior of the PWL system is validated against the experiments. Additionally, the electromechanical response is also validated with the experiments by comparing the output power generated from the experiments with the computational prediction.
more » « less- Award ID(s):
- 1902408
- NSF-PAR ID:
- 10399947
- Date Published:
- Journal Name:
- Volume 10: 34th Conference on Mechanical Vibration and Sound (VIB)
- Volume:
- 10
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract A nonlinear inerter pendulum vibration absorber is integrated with an electromagnetic power take-off system (called IPVA-PTO) and is analyzed for its efficacy in ocean wave energy conversion of a spar platform. The IPVA-PTO system shows a nonlinear energy transfer phenomenon between the spar and the IPVA-PTO which can be used to convert the vibration energy of the spar into electricity while reducing the hydrodynamic response of the spar. The hydrodynamic coefficients of the spar are computed using a commercial boundary-element-method (BEM) code. It is shown that the energy transfer is associated with 1:2 internal resonance of the pendulum vibration absorber, which is induced by a period-doubling bifurcation. The period-doubling bifurcation is studied using the harmonic balance method. A modified alternating frequency/time (AFT) approach is developed to compute the Jacobian matrix involving nonlinear inertial effects of the IPVA-PTO system. It is shown that the period-doubling bifurcation leads to 1:2 internal resonance and plays a major role in the energy transfer between the spar and the pendulum. The response amplitude operator (RAO) in heave and the capture width of the IPVA-PTO-integrated spar are compared with its linear counterpart and it is shown that the IPVA-PTO system outperforms the linear energy harvester as the former has a lower RAO and higher capture width.
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A nonlinear inerter pendulum vibration absorber is integrated with an electromagnetic power take-off system (called IPVA-PTO) and is analyzed for its efficacy in ocean wave energy conversion of a spar platform. The IPVA-PTO system shows a nonlinear energy transfer phenomenon between the spar and the IPVA-PTO which can be used to convert the vibration energy of the spar into electricity while reducing the hydrodynamic response of the spar. The hydrodynamic coefficients of the spar are computed using a commercial boundary-element-method (BEM) code. It is shown that the energy transfer is associated with 1:2 internal resonance of the pendulum vibration absorber, which is induced by a period-doubling bifurcation. The period-doubling bifurcation is studied using the harmonic balance method. A modified alternating frequency/time (AFT) approach is developed to compute the Jacobian matrix involving nonlinear inertial effects of the IPVA-PTO system. It is shown that the period doubling bifurcation leads to 1:2 internal resonance and plays a major role in the energy transfer between the spar and the pendulum. The response amplitude operator (RAO) in heave and the capture width of the IPVA-PTO-integrated spar are compared with its linear counterpart and it is shown that the IPVA-PTO system outperforms the linear energy harvester as the former has a lower RAO and higher capture width.more » « less
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null (Ed.)Fiber-based flexible piezoelectric composites with interdigitated electrodes, namely Macro-Fiber Composite (MFC) structures, strike a balance between the deformation and actuation force capabilities for effective underwater bio-inspired locomotion. These materials are also suitable for vibration-based energy harvesting toward enabling self-powered electronic components. In this work, we design, fabricate, and experimentally characterize an MFC-based bio-inspired swimmer-energy harvester platform. Following in vacuo and in air frequency response experiments, the proposed piezoelectric robotic fish platform is tested and characterized under water for its swimming performance both in free locomotion (in a large water tank) and also in a closed-loop water channel under imposed flow. In addition to swimming speed characterization under resonant actuation, hydrodynamic thrust resultant in both quiescent water and under imposed flow are quantified experimentally. We show that the proposed design easily produces thrust levels on the order of biological fish with similar dimensions. Overall it produces thrust levels higher than other smart material-based designs (such as soft material-based concepts), while offering geometric scalability and silent operation unlike large scale robotic fish platforms that use conventional and bulky actuators. The performance of this untethered swimmer platform in piezoelectric energy harvesting is also quantified by underwater base excitation experiments in a quiescent water and via vortex induced-vibration (VIV) experiments under imposed flow in a water channel. Following basic resistor sweep experiments in underwater base excitation experiments, VIV tests are conducted for cylindrical bluff body configurations of different diameters and distances from the leading edge of the energy harvesting tail portion. The resulting concept and design can find use for underwater swimmer and sensor applications such as ecological monitoring, among others.more » « less
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Abstract Vibration‐based energy harvesting for enabling next‐generation self‐powered devices is a rapidly growing research area. In real‐world applications, the ambient vibrational energy is often available in non‐deterministic forms rather than the extensively studied deterministic scenarios, such as simple harmonic excitation. It is of interest to choose the best piezoelectric material for a given random excitation. Here, performance comparisons of various soft and hard piezoelectric ceramics and single crystals are presented for electrical power generation under band‐limited off‐resonance and wideband random vibration energy‐harvesting scenarios. For low‐frequency off‐resonance excitation, it is found that soft piezoelectric ceramics based upon lead zirconate titanate (e.g., PZT‐5H and PZT‐5A) outperform their hard counterparts (e.g., PZT‐4 and PZT‐8), and likewise soft single crystals based upon lead magnesium niobate and lead titanate as well as PZT (e.g., PMN‐PT and PMN‐PZT) outperform the relatively hard ones (e.g., manganese‐doped PMN‐PZT‐Mn). Overall, for such off‐resonance random vibrations, PMN‐PT is the most suitable choice among the materials studied. For wideband random excitation with a bandwidth covering the fundamental resonance of the harvester, hard piezoelectric ceramics offer larger power output compared to soft ceramics, and likewise hard single crystals produce larger power compared to their soft counterparts. Remarkably, a hard piezoelectric ceramic (e.g., PZT‐8) can outperform a soft single crystal (e.g., PMN‐PT) for wideband random vibration energy harvesting.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1115/DETC2022-89948
