A nonlinear energy harvester for torsional oscillations

© Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics. All rights reserved. Torsional fluctuations around the mean speed of a rotating shaft represent a typical source of undesirable energy losses in many industrial applications. Furthermore, many control and structural health monitoring systems in rotordynamics require an ever-increasing number of sensors. Currently, powering a wireless sensor mounted on a rotating shaft is feasible using either slip rings or batteries, both of which often incur high maintenance costs in applications with difficult access or when idle due to malfunction. In this paper, an electromagnetic energy harvester prototype is manufactured by adapting a commercially available permanent magnet DC motor. The energy harvesting capabilities of the device are preliminary tested and compared to theoretical predictions

Physical realisation of a nonlinear electromagnetic energy harvester for rotational applications

Control and structural health monitoring sensors are becoming increasingly common in industrial and household applications due to recent advances reducing their manufacturing costs, size and power consumption. Nevertheless, providing power for these sensors poses a key challenge to engineers, particularly in system locations where limited access renders regular maintenance infeasible due to high associated costs. In the present work, the design and physical prototype testing of a nonlinear electromagnetic vibration energy harvester is presented based on a previously reported concept of the authors. The harvester is activated by the torsional speed fluctuations of a rotating shaft. Experimental testing in a rig driven by an electric motor confirms the harvester’s properties and the modelled oscillatory behaviour. This novel rotational vibration energy harvester concept may generate over 10 mW of electrical power for a broadband speed range of approximately 400 rpm (in the examined rotational system with set fluctuating speed) for wireless sensing purposes on rotating shafts

Ultra-low frequency energy harvesting using bi-stability and rotary-translational motion in a magnet-tethered oscillator

Harvesting ultra-low frequency random vibration, such as human motion or turbine tower oscillations, has always been a challenge, but could enable many potential self-powered sensing applications. In this paper, a methodology to effectively harness this type of energy is proposed using rotary-translational motion and bi-stability. A sphere rolling magnet is designed to oscillate in a tube with two tethering magnets underneath the rolling path, providing two stable positions for the oscillating magnet. The generated magnetic restoring forces are of periodic form with regard to the sphere magnet location, providing unique nonlinear dynamics and allowing the harvester to operate effectively at ultra-low frequencies (< 1 Hz). Two sets of coils are mounted above the rolling path, and the change of magnetic flux within the coils accomplishes the energy conversion. A theoretical model, including the magnetic forces, the electromagnetic conversion and the occurring bi-stability, is established to understand the electromechanical dynamics and guide the harvester design. End linear springs are designed to maintain the periodic double-well oscillation when the excitation magnitude is high. Parametric studies considering different design factors and operation conditions are conducted to analyse the nonlinear electromechanical dynamics. The harvester illustrates its capabilities in effectively harnessing ultra-low frequency motions over a wide range of low excitation magnitudes