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Adaptive inertia tuning of an energy harvester for increasing its operational bandwidth

Adaptive inertia tuning of an energy harvester for increasing its operational bandwidth
Adaptive inertia tuning of an energy harvester for increasing its operational bandwidth
A rotational energy harvesting system comprises a sprung mass coupled to an electrical generator through a motion transmission system such as a ball screw. In this paper, the operational bandwidth of a rotational energy harvester is expanded by varying its moment of inertia and load resistance of the generator. It is shown that the resulting tuneable device produces significantly higher amounts of harvested power. In addition to mass and stiffness, the natural frequency of a rotational device is defined by its moment of inertia, an additional design parameter that enables implementing the approach presented here. This parameter also determines the apparent mass (inertance) of the device, an important factor that allows a small additional mass to increase the apparent mass hugely and hence increase the overall power density of the harvester.

It is shown that the system with variable load resistance shows a good performance at frequencies around the natural frequency of the device whereas away from resonance frequencies the system with variable moment of inertia produces more power. The approach described in this paper is a first step in the direction of having an autonomous energy harvester with a wide operational bandwidth. One of the advantages of the presented method is that, unlike some other methods, changing the adjustable parameters (i.e., moment of inertia and load resistance) can be conducted intermittently. In other words, this approach only consumes power during the tuning operations and does not use energy once the harvester is tuned at its optimum conditions.

These tuneable rotational systems should be used where the excitation frequency varies slowly (e.g., in marine environment) as any sudden changes in frequency would result in an instantaneous change in the apparent mass and the device may even stall. To implement the device effectively, some kind of predictive control may need to be used that can detect frequency variations fast enough for the inertia to change in a timely manner. This aspect that is outside the scope of this paper is currently under investigation.
Operational bandwidth; Rotational harvester; Variable inertia
3492-3497
Moshrefi-Torbati, Mohamed
65b351dc-7c2e-4a9a-83a4-df797973913b
Hendijanizadeh, Mehdi
9631d6d8-f4fb-4088-8d66-950699eba189
Sharkh, Suleiman M.
c8445516-dafe-41c2-b7e8-c21e295e56b9
Moshrefi-Torbati, Mohamed
65b351dc-7c2e-4a9a-83a4-df797973913b
Hendijanizadeh, Mehdi
9631d6d8-f4fb-4088-8d66-950699eba189
Sharkh, Suleiman M.
c8445516-dafe-41c2-b7e8-c21e295e56b9

Moshrefi-Torbati, Mohamed, Hendijanizadeh, Mehdi and Sharkh, Suleiman M. (2017) Adaptive inertia tuning of an energy harvester for increasing its operational bandwidth. Procedia Engineering, 199, 3492-3497. (doi:10.1016/j.proeng.2017.09.463).

Record type: Article

Abstract

A rotational energy harvesting system comprises a sprung mass coupled to an electrical generator through a motion transmission system such as a ball screw. In this paper, the operational bandwidth of a rotational energy harvester is expanded by varying its moment of inertia and load resistance of the generator. It is shown that the resulting tuneable device produces significantly higher amounts of harvested power. In addition to mass and stiffness, the natural frequency of a rotational device is defined by its moment of inertia, an additional design parameter that enables implementing the approach presented here. This parameter also determines the apparent mass (inertance) of the device, an important factor that allows a small additional mass to increase the apparent mass hugely and hence increase the overall power density of the harvester.

It is shown that the system with variable load resistance shows a good performance at frequencies around the natural frequency of the device whereas away from resonance frequencies the system with variable moment of inertia produces more power. The approach described in this paper is a first step in the direction of having an autonomous energy harvester with a wide operational bandwidth. One of the advantages of the presented method is that, unlike some other methods, changing the adjustable parameters (i.e., moment of inertia and load resistance) can be conducted intermittently. In other words, this approach only consumes power during the tuning operations and does not use energy once the harvester is tuned at its optimum conditions.

These tuneable rotational systems should be used where the excitation frequency varies slowly (e.g., in marine environment) as any sudden changes in frequency would result in an instantaneous change in the apparent mass and the device may even stall. To implement the device effectively, some kind of predictive control may need to be used that can detect frequency variations fast enough for the inertia to change in a timely manner. This aspect that is outside the scope of this paper is currently under investigation.

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Accepted/In Press date: 12 September 2017
e-pub ahead of print date: 12 September 2017
Keywords: Operational bandwidth; Rotational harvester; Variable inertia

Identifiers

Local EPrints ID: 414869
URI: http://eprints.soton.ac.uk/id/eprint/414869
PURE UUID: 026882df-36d4-4689-b243-0bfc920a3c5b

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Date deposited: 12 Oct 2017 16:31
Last modified: 06 Oct 2020 19:45

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