Shiqiao Gao

Vibration piezoelectric energy harvester with multi-beam

This work presents a novel vibration piezoelectric energy harvester, which is a micro piezoelectric cantilever with multi-beam. The characteristics of the PZT (Pb(Zr0.53Ti0.47)O3) thin film were measured; XRD (X-ray diffraction) pattern and AFM (Atomic Force Microscope) image of the PZT thin film were measured, and show that the PZT (Pb(Zr0.53Ti0.47)O3) thin film is highly (110) crystal oriented; the leakage current is maintained in nA magnitude, the residual polarisation Pr is 37.037 μC/cm2, the coercive field voltage Ec is 27.083 kV/cm, and the piezoelectric constant d33 is 28 pC/N. In order to test the dynamic performance of the energy harvester, a new measuring system was set up. The maximum output voltage of the single beam of the multi-beam can achieve 80.78 mV under an acceleration of 1 g at 260 Hz of frequency; the maximum output voltage of the single beam of the multi-beam is almost 20 mV at 1400 Hz frequency.

Acoustic metamaterials with coupled local resonators for broadband vibration suppression

This paper investigates a modified acoustic metamaterial system with local resonators coupled through linear springs. The proposed acoustic metamaterial system can provide three band gaps for broadband vibration suppression. First, the band structure of the modified acoustic metamaterial is calculated by using Bloch’s theorem under the assumption of infinite lattice. The existence of three band gaps is confirmed in the band structure. Effects of mass and spring parameters on the band gap behaviour of the modified metamaterial are investigated through a dimensionless parametric study. Based on the parametric study, optimal dimensionless parameters are proposed to achieve maximal total band gap width in the low frequency range. Subsequently, a more realistic finite lattice model is established. The transmittances of the conventional and modified metamaterial systems are compared. The three band gaps predicted from transmittances and broadband vibration suppression behaviour are consistent with the predictio...

A utility piezoelectric energy harvester with low frequency and high-output voltage: Theoretical model, experimental verification and energy storage

In this paper, a utility piezoelectric energy harvester with low frequency and high-output voltage is presented. Firstly, the harvester’s three theoretical models are presented, namely the static model, the quasi static model and the dynamic vibration model. By analyzing the influence of the mass ratio of the mass block to the beam on output characteristics of the harvester, we compare the quasi static model and the dynamic vibration model and then define their applicable ranges. Secondly, simulation and experiments are done to verify the models, using the harvester with PZT-5H piezoelectric material, which are proved to be consistent with each other. The experimental results show that the output open-circuit voltage and the output power can reach up to 86.36V and 27.5mW respectively. The experiments are conducted when this harvester system is excited by the first modal frequency (58.90Hz) with the acceleration 10m/s2. In this low frequency vibration case, it is easy to capture the energy in the daily env...

Modeling and Analysis of an Up-conversion Electret Electrostatic Energy Harvester

In order to reduce the environmental sensitive frequency of electret-based vibration electrostatic energy harvester (E-VEH), an up-conversion structure is designed. This harvester is a double cantilever structure includes a low frequency beam and high frequency beam. Electret is bounded to the high frequency beam, the low frequency beam vibrates excited by environment, and impacts the high frequency beam. The model of this structure is established and analyzed firstly. Then a prototype is made and tested. According to the measurement result, this kind of structure can convert part of the vibration energy within the vibration frequency between 1Hz and 70Hz into electrical energy under the action of the excitation load with the amplitude is 8m/s. This indicates that the up-conversion structure can validly reduce the sense frequency of E-VEH, and can expand the harvester work bands. Introduction With the rapid development of MEMS, COMS sensors and data processing, the times of internet of things is coming. As an important part of internet of things, wireless sensor networks are rapidly growing. At present, chemical batteries are used for suppling power to wireless sensor networks. However, it hampers the development of wireless sensor networks because chemical batteries have maintenance, environmental and size issues. In recent years, it is concerned and studied how to harvest environment energy and convert it into electric power [1-3]. The vibration harvester has been paid more attention because vibration happens in anywhere and anytime. For vibration harvester, three mechanisms have been proposed: piezoelectric, electromagnetic and electrostatic Compared with piezoelectric and electromagnetic energy harvesters, electrostatic systems have advantages of compatibility with MEMS processes and small size. Electret-based vibration energy harvesters (E-VEHs) can be divided into two types, in-plane and out-of-plane. Compared with the in-plan E-VEHs, Out-of-plane E-VEHs have lower production costs because the device structure and process are relatively simple. Driven by the merit of low production costs, more and more researchers have focused on out-of-plane E-VEHs and attempted to improve their performance. When designing structure of out-of-plane E-VEHs, cantilever or double-end fixed beam is commonly employed. The size of these harvesters is usually small as their employers are always small. Therefor the natural frequency of most harvester structures is relatively high, always at the level of KHz. However, in natural environment, vibration frequency is always at the level of Hz. In order to increasing the harvest efficiency, it is an important point to decrease the structure natural frequency. In this paper, an up-conversion structure is introduced to reduce the environmental sensitive frequency of the E-VEHs. The model of this structure is established, and its characteristics are analyzed. By test, this up-conversion structure can effectively decrease the sensitive frequency of cantilever E-VEHS. Work Mechanism of E-VEHs The core of E-VEHs is a kind of dielectric function material called electret which can keep space charge or dipole charge for a long time. With the space electret method promotion, more and more space charge electret, as shown in Fig.1 (a), has been used, especially for vibration energy harvester. 93 Copyright

Real-time numerical calculation for penetration depth of projectiles into concrete targets

ABSTRACT Based on the acceleration data measured by penetration experiments with ogive-nose projectiles into semi-infinite concrete targets, a fuzzy method which can calculate the real-time penetration depth was developed. In the proposed method, the whole process of penetration was divided into three stages according to the instantaneous velocity, and each stage was described by different models. By judging the calculation error, threshold velocities between stages were automatically determined. Meanwhile, the striking velocity of the penetration process was calculated using the acceleration in whole trajectory. The calculated values by model are in reasonably good agreement with the measured data from experiments.

Fabrication and characterization of a piezoelectric energy harvester with clamped-clamped beams

This work presents a piezoelectric energy harvester with clamped-clamped beams, and it is fabricated with MEMS process. When excited by sinusoidal vibration, the energy harvester has a sharp jumping down phenomenon and the measured frequency responses of the clamped-clamped beams structure show a larger bandwidth which is about 56Hz, more efficient than that with cantilever beams. When the exciting acceleration ac is 12m/s2, the energy harvester achieves to a maximum open-circuit voltage of 94mV on one beam. The load voltage is proportional to the load resistance, and it increased with the increase of load resistance. Connected four beams in series, the output power reaches the maximum value of 730 nW and the optimal load is 15KΩ to one beam.

Theoretical modeling, simulation and experimental study of hybrid piezoelectric and electromagnetic energy harvester

In this paper, performances of vibration energy harvester combined piezoelectric (PE) and electromagnetic (EM) mechanism are studied by theoretical analysis, simulation and experimental test. For the designed harvester, electromechanical coupling modeling is established, and expressions of vibration response, output voltage, current and power are derived. Then, performances of the harvester are simulated and tested; moreover, the power charging rechargeable battery is realized through designed energy storage circuit. By the results, it’s found that compared with piezoelectric-only and electromagnetic-only energy harvester, the hybrid energy harvester can enhance the output power and harvesting efficiency; furthermore, at the harmonic excitation, output power of harvester linearly increases with acceleration amplitude increasing; while it enhances with acceleration spectral density increasing at the random excitation. In addition, the bigger coupling strength, the bigger output power is, and there is the optimal load resistance to make the harvester output the maximal power.In this paper, performances of vibration energy harvester combined piezoelectric (PE) and electromagnetic (EM) mechanism are studied by theoretical analysis, simulation and experimental test. For the designed harvester, electromechanical coupling modeling is established, and expressions of vibration response, output voltage, current and power are derived. Then, performances of the harvester are simulated and tested; moreover, the power charging rechargeable battery is realized through designed energy storage circuit. By the results, it’s found that compared with piezoelectric-only and electromagnetic-only energy harvester, the hybrid energy harvester can enhance the output power and harvesting efficiency; furthermore, at the harmonic excitation, output power of harvester linearly increases with acceleration amplitude increasing; while it enhances with acceleration spectral density increasing at the random excitation. In addition, the bigger coupling strength, the bigger output power is, and there is the o...

The micro mechanical environment on the comb capacitive micro-machined gyroscope

With the in-depth researches on MEMS sensors, a lot of mechanical problems are encountered inevitably. Especially for the comb capacitive micro-machined gyroscope, a typical MEMS inertia sensor, the speciality of its structure and micro size determines the characteristics of the mechanical environment. With the reduction of structural size, the ratio of surface force and body force has increased clearly. Comparing with the roles of body force, the roles of surface force in MEMS sensors become more and more important. The micro forces, such as electrostatic force, Van de Waals force, capillary force and air-damping force were analyzed, and the action extent of these micro forces were obtained.