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• A novel M-PEH with built-in outer-inner magnetic tri-stable oscillators (TOS) is proposed for energy harvesting enhancement. • Built-in outer-inner magnetic TOSs brings more compact structure but wider bandwidth and higher power generation. • Synchronous nonlinear coupling interaction between the outer and inner TOS benefits to energy harvesting enhancement. • Effective bandwidth and output power increased by 300% and 662% compared to the 1-DOF magnet coupling tri-stable PEH. • Practical applications prove the M-PEH meeting the power supplying requirements of engineering community. Tri-stable oscillators have been widely used to develop various nonlinear broadband energy harvesters. Focusing on further achieving high-performance piezoelectric energy harvester under broadband vibrations, a novel M-shaped 2-DOF piezoelectric energy harvester (M-PEH) with built-in outer-inner magnetic tri-stable oscillators is proposed, in which an inner magnetic tri-stable oscillator is built-in into a U-shaped outer magnetic tri-stable oscillator using its cut-out cantilever beam, assisted by the coupling interface to further enhance the dynamic responses. A complete physical model by considering the nonlinear coupling interaction between the outer-inner magnetic tri-stable oscillators is established to describe the dynamic performances under different system parameters. The theoretical model is well validated by experiments, which show that the proposed M-PEH has more compact size, wider operating frequency and higher power generation, offering an effective bandwidth of 20.1 Hz (5.1–25.2 Hz) at base excitation A = 5 m/s2, and achieving maximum output voltage 8.5 V and total peak power 26.7 μW. Compared to the original magnetic-coupling nonlinear tri-stable PEH, the effective bandwidth and total power have increased by 300 % and 662 % respectively, and the average power density is increased by 917 %. In addition, four main coupling interaction modes between the outer and inner built-in tri-stable oscillator are observed, in which the nonlinear synchronous coupling interaction is conducive to generating inter-well motion, leading to more mechanical energy being transferred from the outer tri-stable oscillator to the inner built-in tri-stable oscillator, thereby improving power generation capacity. Besides, the coupling interaction between these two tri-stable oscillators produces two close resonances which can be easily tuned to form a wide operating bandwidth. Practical applications prove that the proposed M-PEH has the ability to power low-powered electronic products, meeting the power supplying requirements of engineering community. [ABSTRACT FROM AUTHOR]

A piezo-magneto-elastic-electric hybrid structure composed of a piezo-magneto-elastic multi-stable harvester (PMEH), a mass-spring-damper elastic supporting oscillator (ESO) and a nonlinear synchronous switching power extraction (SSPE) circuit is proposed to achieve high-performance energy harvesting over a wide bandwidth. Governing equations describing the dynamic and electrical responses of the hybrid structure with two SSPE circuits are derived, and their steady-state solutions are then solved with harmonic balance method and given along via theoretical simulations. Experimental results exhibit qualitative agreement with the theory. The results show that the coupling nonlinearities between the PMEH and SSPE can broad the bandwidth and enhance the power extraction. The hybrid structure with SSPE can offer a wide range of global inter-well oscillation from 2Hz − 13Hz, and generates a maximum extracted power of 20 µW. Field experiment and practical applications demonstrate that the hybrid structure combining with SSPE circuit has the potential promising in powering low-powered electronic devices. [ABSTRACT FROM AUTHOR]

Ultrasound vibrations, which are abundant in our everyday environment, have long been widely used in industrial applications and medical therapeutics. While there have massive number of studies on harvesting the low-frequency vibration energy to power the low-powered electronic devices, there are few literatures on the ultrasound vibration energy harvesting. In order to validate the feasibility of ultrasound vibration energy harvesting, this article takes a rotary-type piezoelectric ultrasound actuator (PUA) as the research object, a new PZT ring with appropriate zoning and polarization is bonded onto its elastomer top surface to harvest the vibration energy induced by the ultrasound waves. The manufacturing process and operating mechanism of the modified PUA are firstly introduced. Then, the electromechanical coupled model is derived based on the equivalent circuit method, and the dynamic and energetic characteristics of the ultrasound vibration energy harvesting under three excitation modes (i.e., two standing waves and one traveling wave excitations) are theoretically studied. The experimental results testify the theoretical values, and the feasibility of ultrasound vibration energy harvesting is also validated by experiments and an application example. When the PUA is excited by traveling ultrasound wave with amplitude 67 V and frequency 35.1 kHz, the maximum harvested power of each sector of the new PZT ring and λ/4 sector of the bottom PZT ring reach 58 mW and 82.4 mW, respectively, which fully meet the power supplying requirements of low-powered electronic products and implantable medical systems. [ABSTRACT FROM AUTHOR]