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 analyze the nonlinear electromechanical dynamics. The harvester illustrates its capabilities in effectively harnessing ultra-low frequency motions over a wide range of low excitation magnitudes.

No 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.

No abstract

Many industrial applications incorporate rotating shafts with fluctuating speeds around a desired mean value. This often harmonic component of the shaft speed is generally undesirable, since it can excite parts of the system and can lead to large oscillations (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 supply power to the sensor and extract data from the rotating application. 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 shaft’s operating conditions.