| 1. |
- Köhler, Elof, 1980, et al.
(författare)
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Impact of designed asymmetries on the effective bandwidth of a backfolded piezoelectric energy harvester
- 2019
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Ingår i: Sensors and Actuators, A: Physical. - : Elsevier BV. - 0924-4247. ; 292, s. 77-89
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Tidskriftsartikel (refereegranskat)abstract
- For the successful realization of autonomous wireless sensors, they will have to be able to harvest energy from their surroundings. Vibrational energy harvesting is one possible power source for wireless sensors, since vibrations are abundant in many environments. In order to make vibrational energy harvesters more useful, a broad bandwidth is desirable since many vibrations are stochastic in nature. In this paper we implement asymmetry to a backfolded piezoelectric energy harvester to achieve broader effective bandwidth with maintained power output. The optimized harvester achieves a minimum of 2.75 V in the frequency range 92–162 Hz with peak power output of 1.80 mW. Asymmetry based on different lengths of the conjoined cantilevers is experimentally and numerically shown to have the largest impact on the bandwidth, compared to the impact of modified mass loadings.
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| 2. |
- Staaf, Henrik, 1976, et al.
(författare)
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Achieving increased bandwidth for 4 degree of freedom self-tuning energy harvester
- 2018
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 1095-8568 .- 0022-460X. ; 420, s. 165-173
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Tidskriftsartikel (refereegranskat)abstract
- The frequency response of a self-tuning energy harvester composed of two piezoelectric cantilevers connected by a middle beam with a sliding mass is investigated. Measurements show that incorporation of a free-sliding mass increases the bandwidth. Using an analytical model, the system is explained through close investigation of the resonance modes. Resonance mode behavior further suggests that, by breaking the symmetry of the system, even broader bandwidths are achievable.
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| 3. |
- Staaf, Henrik, 1976, et al.
(författare)
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Effective piezoelectric energy harvesting with bandwidth enhancement by assymetry augmented self-tuning of conjoined cantilevers
- 2019
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Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403. ; 150, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Vibrational energy harvesting offers a potential power supply for future intelligent wireless sensors. In order to make vibrational energy harvesters more useful, a broad bandwidth is desirable since many vibrations are stochastic in nature. In this paper we use a piezoelectric self-tuning energy harvester to demonstrate the importance of designing for asymmetry in a system of conjoined cantilevers. Asymmetry is achieved by varying the piezoelectric cantilever lengths as well as the proof mass weights. In addition to bandwidth broadening, a self-tuning effect is experimentally demonstrated by a sliding mass. The measurement results confirm previous model predictions.
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| 4. |
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| 5. |
- Johansson, Martin, 1973, et al.
(författare)
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Approximate boundary conditions for a fluid-loaded elastic plate
- 2005
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 1520-8524 .- 0001-4966. ; 118:6, s. 3436-3446
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Tidskriftsartikel (refereegranskat)abstract
- Approximate boundary conditions for an infinite elastic layer immersed in a fluid are derived. By using series expansions in the thickness coordinate of the plate fields, the displacements fields are eliminated, adopting the three-dimensional equations of motion. The sums and differences of the boundary pressure fields and their normal derivatives are related through a set of approximate boundary conditions, one symmetric and one antisymmetric. These equations involve powers in the layer thickness together with partial derivatives with respect to time as well as the spatial variables in the plate plane. The approximate boundary conditions can be truncated to an arbitrary order, and explicit relations are presented including terms of order five. Comparisons are made with effective boundary conditions using classical plate theories. The numerical examples involve reflection and transmission of plane waves incident on the plate at different angles, as well as the pressure fields due to a line force. Three fluid-loading cases are studied: modest, heavy, and light loadings. The results using truncated approximate boundary conditions are compared to exact and classical plate solutions. The examples show that the accuracies of the power series approximations of order three and higher are very good in the frequency interval considered.
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| 6. |
- Johansson, Martin, 1973, et al.
(författare)
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Dispersion free wave splittings for structural elements
- 2006
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Ingår i: Computers and Structures. - : Elsevier BV. - 0045-7949. ; 84:7, s. 514-27
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Tidskriftsartikel (refereegranskat)abstract
- Wave splittings are derived for three types of structural elements: membranes, Timoshenko beams, and Mindlin plates. The Timoshenko beam equation and the Mindlin plate equation are inherently dispersive, as is each Fourier component of the membrane equation in an angular decomposition of the field. The distinctive feature of the wave splittings derived in the present paper is that, in homogeneous regions, they transform the dispersive wave equations into simple one-way wave equations without dispersion. Such splittings have uses both for radial scattering problems in the 2D cases and for scattering problems in dispersive media. As an example of how the splittings may be applied, a direct scattering problem is solved for a membrane with radially varying density. The imbedding method is utilized, and agreement is obtained with an FE simulation.
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| 7. |
- Persson, Peter, et al.
(författare)
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Byggande av lätta trähus i tätbebyggda städer
- 2020
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Ingår i: Bygg & Teknik. ; 3, s. 24-26
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Strävan efter ett hållbart byggande med miljövänliga material har bidragit till ett ökat intresse för trämaterial. Samtidigt förtätas städerna alltmer och mark nära kollektivtrafik behöver tas i anspråk. Eftersom lätta konstruktioner kan vara känsliga för vibrationer finns risk för att husen som byggs inte tillfredsställer kraven på en god inomhusmiljö med avseende på buller och vibrationer. Om det går att beräkna och förutsäga buller och vibrationsnivåer tidigt i designprocessen så finns det goda möjligheter att hitta tekniska lösningar som fungerar. Problemet idag är att beräkningsmodellerna är alltför komplicerade och kräver specialistkompetens. Vår ambition är att utveckla en användarvänlig, effektiv och rimligt säker modell för att prediktera vibrationer i lätta trähus nära spårbunden trafik.
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| 8. |
- Staaf, Henrik, 1976, et al.
(författare)
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Selftuning energy harvester by sliding weight
- 2017
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Ingår i: Svenska Mekanikdagarna 2017, 12-13 juni, Uppsala, Sverige.
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Konferensbidrag (refereegranskat)abstract
- This presentation reports design and measurements of a piezoelectric harvester with self-tuning for wider bandwidth and coupled piezoelectric cantilevers to maintain a high power output by extended strain distribution. The harvester is intended for powering sensors on gas turbines and has certain conditions on size, temperature and frequency
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| 9. |
- Staaf, Henrik, 1976, et al.
(författare)
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Smart design piezoelectric energy harvester with self-Tuning
- 2017
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 922:1
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Konferensbidrag (refereegranskat)abstract
- Piezoelectric energy harvesting on a gas turbine implies constraints like high temperature tolerance, size limitation and a particular range of vibrations to utilise. In order to be able to operate under these conditions a harvester needs to be space effective and efficient and to respond to the appropriate range of frequencies. We present the design, simulation and measurements for a clamped-clamped coupled piezoelectric harvester with a free-sliding weight, which adds self-Tuning for improved response within the range of vibrations from the gas turbine. We show a peak open circuit voltage of 11.7 V and a 3 dB bandwidth of 12 Hz.
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| 10. |
- Staaf, Henrik, 1976, et al.
(författare)
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Verification of Self-Tuning 4DOF Piezoelectric Energy Harvester with Enhanced Bandwidth
- 2018
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we present an analytical model to predict enhanced bandwidth for a piezoelectric energy harvester with self-tuning, accomplished by a sliding mass. The model predicts that by implementing asymmetry of different piezoelectric cantilever lengths , the bandwidth can theoretically approach 60 Hz. Validation measurements demonstrate an increased 3dB bandwidth up to 21 Hz with 150 mW, by configuration 23/17 mm in open length – providing sufficient power for a ZigBee to continually transmit.
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