Zhengbao Yang

Theoretical and experimental investigation of a nonlinear compressive-mode energy harvester with high power output under weak excitations

Harvesting ambient vibration energy is a promising method for realizing self-powered autonomous operation for low-power electronic devices. Most energy harvesters developed to date employ bending-beam configurations and work around the resonant points. There are two critical problems that have hindered the widespread adoption of energy harvesters: insufficient power output and narrow working bandwidth. To overcome these problems, we proposed a novel energy harvester, called a high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH). The HC-PEH delicately synthesizes the merits of the force amplification effect of the flexural motion and the dynamic properties of elastic beams, and thus is capable of high power output with wide working bandwidth. In this paper, theoretical and experimental studies were performed on the HC-PEH. Taking nonlinear stiffness, nonlinear damping, and nonlinear piezoelectricity into account, we developed an analytical model that provides comprehensive insight into the nonlinear mechanical and electrical behaviors of the system. The analytical results closely render the experimental data and demonstrate great performance enhancement. In the experiment, a maximum power output of 54.7 mW is generated at 26 Hz under an acceleration of 4.9 m s−2, which is over one order of magnitude higher than other state-of-the-art systems.

Toward Harvesting Vibration Energy from Multiple Directions by a Nonlinear Compressive-Mode Piezoelectric Transducer

We propose a new concept for harvesting vibration energy from multiple directions. Our approach effectively exploits the nonlinear vibration of a doubly clamped elastic rod, converting and amplifying excitations to compressive loads in piezoelectric materials. The proposed multidirectional compressive-mode piezoelectric energy harvester (MC-PEH) is capable of isotropically harnessing vibration energy from any angle in a plane. Meanwhile, the MC-PEH demonstrates a high-voltage output and a wide working bandwidth, along with the distinct softening nonlinear phenomena. Theoretical analysis and experimental testing are performed and exhibit good agreement over a range of excitation frequencies. This study enhances the practicability and adaptability of using energy harvesters in a complex environment.

Reversible Nonlinear Energy Harvester Tuned by Tilting and Enhanced by Nonlinear Circuits

Nonlinear vibration is capable of effectively extending the frequency bandwidth of energy harvesters. Either hardening or softening nonlinearity has been used in various designs to achieve broad-bandwidth energy harvesting. In this paper, we propose a new method to achieve reversible hysteretic responses, i.e., both hardening and softening nonlinear responses, mechanically without additional magnetic interactions. This tunable nonlinearity endows energy harvesters with a great adaptability to environment. The proposed energy harvester is composed of a flexural center and two mass blocks, supported by a pair of elastic rods that are fixed on a vibration base. Different nonlinear responses are invoked by tilting the fixed-fixed elastic rods at different angles. A lumped-parameter model is developed to simulate the nonlinear electromechanical coupling system, and that is analytically solved by virtue of the high-order perturbation technique. The dynamic responses under different frequencies and accelerations are analytically characterized and compared well with the experimental data measured from a fabricated prototype. Furthermore, a nonlinear conditioning circuit (self-powered series synchronized switch harvesting on inductor) is constructed and tested with the proposed nonlinear energy harvester, with which the performance is enhanced about 200% for both resistive loads and capacitive loads.

Modeling and parametric study of a force-amplified compressive-mode piezoelectric energy harvester

Piezoelectric energy harvesters have great potential for achieving inexhaustible power supply for small-scale electronic devices. However, the insufficient power-generation capability and the narrow working bandwidth of traditional energy harvesters have significantly hindered their adoption. To address these issues, we propose a nonlinear compressive-mode piezoelectric energy harvester. We embedded a multi-stage force amplification mechanism into the energy harvester, which greatly improved its power-generation capability. In this article, we describe how we first established an analytical model to study the force amplification effect. A lumped-parameter model was then built to simulate the strong nonlinear responses of the proposed energy harvester. A prototype was fabricated which demonstrated a superior power output of 30 mW under an excitation of 0.3g ( g = 9 . 8 m/s2). We discuss at the end the effect of geometric parameters that are influential to the performance. The proposed energy harvester is suitable to be used in low-frequency weak-excitation environments for powering wireless sensors.

Study on the hydrodynamics and kinematics of a biomimetic fin propulsor actuated by SMA wires

A flexible noiseless and high-efficient propulsor plays a prominent role in the performance of underwater vehicles. This paper presents a micro flexible caudal fin propulsor actuated by shape memory alloy (SMA) wires. To improve the responding frequency and fatigue of the SMA wires, a pair of slots is designed. So the SMA wires can be heated in the protection of silica gel layer and cool in the other status, i.e. flowing water. Then the propulsive performance of the biomimetic propulsor is evaluated through thrust measurement experiments. Note that higher undulating frequency does not mean stronger thrust force because the undulating amplitude descends along with the undulating frequency increase for this kind SMA propulsor. Further, the kinematics of the propulsor is analyzed and the corresponding equation of motion is obtained. At last, a three-dimensional numerical simulation on the biomimetic fin was conducted by CFD to investigate the interaction of the propulsor with surrounding water and the thrust production. The CFD results consist with the experimental results well, which verify the kinetic model and the numerical simlation.

Distributed parameter model and experimental validation of a compressive-mode energy harvester under harmonic excitations

This paper presents the modeling and parametric analysis of the recently proposed nonlinear compressive-mode energy harvester (HC-PEH) under harmonic excitation. Both theoretical and experimental investigations are performed in this study over a range of excitation frequencies. Specially, a distributed parameter electro-elastic model is analytically developed by means of the energy-based method and the extended Hamilton’s principle. An analytical formulation of bending and stretching forces are derived to gain insight on the source of nonlinearity. Furthermore, the analytical model is validated against with experimental data and a good agreement is achieved. Both numerical simulations and experiment illustrate that the harvester exhibits a hardening nonlinearity and hence a broad frequency bandwidth, multiple coexisting solutions and a large-amplitude voltage response. Using the derived model, a parametric study is carried out to examine the effect of various parameters on the harvester voltage response. ...

Nonlinear vibration analysis of the high-efficiency compressive-mode piezoelectric energy harvester

Power source is critical to achieve independent and autonomous operations of electronic mobile devices. The vibration-based energy harvesting is extensively studied recently, and recognized as a promising technology to realize inexhaustible power supply for small-scale electronics. Among various approaches, the piezoelectric energy harvesting has gained the most attention due to its high conversion efficiency and simple configurations. However, most of piezoelectric energy harvesters (PEHs) to date are based on bending-beam structures and can only generate limited power with a narrow working bandwidth. The insufficient electric output has greatly impeded their practical applications. In this paper, we present an innovative lead zirconate titanate (PZT) energy harvester, named high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH), to enhance the performance of energy harvesters. A theoretical model was developed analytically, and solved numerically to study the nonlinear characteristics of the HC-PEH. The results estimated by the developed model agree well with the experimental data from the fabricated prototype. The HC-PEH shows strong nonlinear responses, favorable working bandwidth and superior power output. Under a weak excitation of 0.3 g (g = 9.8 m/s2), a maximum power output 30 mW is generated at 22 Hz, which is about ten times better than current energy harvesters. The HC-PEH demonstrates the capability of generating enough power for most of wireless sensors.

Impedance matching circuit for synchronous switch harvesting on inductor interface

With the use of the technique named synchronous switch harvesting on inductor (SSHI), the piezoelectric energy harvesting efficiency can be greatly improved compared to the standard energy harvesting (SEH) interface. However, the SSHI output power is significantly influenced by its load voltage or load impedance. This paper presents a power conditioning circuit intending to maximize the amount of power extracted from the SSHI interface. The model of a buck-boost converter working in discontinuous current mode is constructed, with the converters behavior in good agreement with the SSHI optimization criteria. Experimental results validate that the conditioning circuit is able to optimize the SSHI interface output, and hence enhance the responses of the circuit for various load impedance.

Charge Redistribution in Flextensional Piezoelectric Energy Harvesters

Harvesting ambient wasted energy has been in recent years a prominent research endeavor, aimed at providing alternative energy sources for low-power electronic mobile devices. Among various solutions, piezoelectric energy harvesters have attracted major attention due to the scalability, high-efficiency and the universal presence of vibration sources. In this paper, we studied the charge redistribution phenomenon in piezoelectric energy harvesters employing flextensional structures numerically and experimentally. A finite element model was developed firstly to study the mechanical and electrical response of flextensional transducers. The simulation results were then validated by a corresponding experiment. The research reveals that energy is dissipated in the process that charge flows from the high potential region to the low potential region. The electrode shape has a significant effect on the efficiency, and therefore should be considered fully when designing new energy harvesters. This study also assists in the design of flextensional sensors and actuators.

Introducing hinge mechanisms to one compressive-mode piezoelectric energy harvester

In this paper, a hinge mechanism is introduced into one compressive-mode piezoelectric energy harvester to improve its performance. First, the concept of implementing hinge mechanisms is introduced on a high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH). Second, a numerical model based on the piezoelectric constitutive equation and the Duffing oscillator equations is formulated to obtain voltage responses, velocity responses, and the fundamental frequency and bandwidth. Then, a prototype is fabricated to validate the results of the model. Depending on the number of hinges applied to the HC-PEH, three cases are investigated: fully hinged, partially hinged, and clamped. In both numerical modeling and experimental studies, the HC-PEH prototypes in the three cases are exposed to frequency-sweep excitations to illustrate the dynamic and transduction behaviors. The results demonstrate that the overall performance in the hinged cases is improved significantly compared to that in the clamped case. The output voltage and output power are increased by 2–3 times and up to 5 times, respectively, and fundamental resonant frequency is lowered to below 20u2009Hz. Furthermore, it is shown that the operational bandwidth is widened by up to 37%.In this paper, a hinge mechanism is introduced into one compressive-mode piezoelectric energy harvester to improve its performance. First, the concept of implementing hinge mechanisms is introduced on a high-efficiency compressive-mode piezoelectric energy harvester (HC-PEH). Second, a numerical model based on the piezoelectric constitutive equation and the Duffing oscillator equations is formulated to obtain voltage responses, velocity responses, and the fundamental frequency and bandwidth. Then, a prototype is fabricated to validate the results of the model. Depending on the number of hinges applied to the HC-PEH, three cases are investigated: fully hinged, partially hinged, and clamped. In both numerical modeling and experimental studies, the HC-PEH prototypes in the three cases are exposed to frequency-sweep excitations to illustrate the dynamic and transduction behaviors. The results demonstrate that the overall performance in the hinged cases is improved significantly compared to that in the clamped...