A Nonlinear Concept of Electromagnetic Energy Harvester for Rotational Applications

Abstract

Many industrial applications incorporate rotating shafts with fluctuating speeds around a required mean value. This often harmonic component of the shaft speed is generally detrimental, since it can excite components of the system, leading to large oscillations (and potentially durability issues), as well as to excessive noise generation. On the other hand, the addition of sensors on rotating shafts for system monitoring or control poses challenges due to the need to constantly supply power to the sensor and extract data from the system. In order to tackle the requirement of powering sensors for structure health monitoring or control applications, this work proposes a nonlinear vibration energy harvester design intended for use on rotating shafts with harmonic speed fluctuations. The essential nonlinearity of the harvester allows for increased operating bandwidth, potentially across the whole range of the shaft's operating conditions.

Physical realisation of a nonlinear electromagnetic energy harvester for rotational applications

“…The rotor is experiencing base-type excitation due to the acceleration of the shaft, as well as excitation due to the electromechanical interactions in the energy harvester. 25 The corresponding equation of motion is given by:…”

“…Gun et al [24][25][26] presented a nonlinear energy harvester concept for rotational applications. The harvester is essentially a rotor brushless permanent magnet direct current (DC) motor connected to a rotating shaft by a spring with cubic stiffness coefficient of nonlinearity.…”

“…The harvester dynamics gave rise to a condition where a jump down frequency of the occurring Duffing oscillator (harvester) is unattainable due to the frequency dependent vibration amplitude increasing the jump down frequency as the excitation frequency increases. 24,25 The design of broadband vibration energy harvesters for rotational systems -in particular propulsion applications -has been the main motivation behind this work. This originates from the ever increasing requirements to obtain accurate, real-time information for structural health monitoring during operation, without the use of batteries and harnessing.…”

“…A physical prototype of a nonlinear (duffing-type) electromagnetic vibration energy harvester for rotational applications is presented. The prototype has been developed based on a previously discussed concept of the authors [24][25][26] and validates the associated modelling work. The cubic stiffness coefficient of nonlinearity is induced in the harvester using conical springs.…”

An Ultra-Low Frequency Magnet-Tethered Vibration Energy Harvester for Self-Powered Sensing

“…Abdelnaby and Arafa [8] proposed an electromagnetic EH capable of generating 0.14 mW from 5 Hz excitation frequency and 1.8 mm excitation amplitude. Other critical influences in energy harvesting using electromagnetic transductions include applications of cantilever beams [8][9][10], rotational mechanisms [11][12][13][14] and pendulum-based structures [15][16][17].…”