Papers by Keyword: Resonant Frequency

Abstract: The effectiveness of power generation of the piezoelectric energy harvester (PEH) depends on the coupling between its resonant frequency and the oscillation frequency of the vibration source. The resonant frequency of a PEH is determined by its structural design, and therefore, to improve piezoelectric energy harvester performance, the piezoelectric energy harvester must be optimally designed to achieve the resonant frequency that matches the excitation frequency of the vibration source. This paper presents the design and detailed calculation of the piezoelectric energy harvester in the form of a bimorph piezoelectric circular diaphragm (PCD) structure by finite element analysis (FEA) using the software package ANSYS. Based on analyses and calculations, the optimal structure of the piezoelectric circular diaphragm energy harvester is proposed to meet the specified resonant frequency response matching the vibration source frequency. Detailed calculations of the PEH were performed with an excitation frequency of 100 Hz. With an optimal load resistor of 10.1 kΩ, an output power of 0.287 W was generated at 100 Hz (equal to the resonant frequency of the PEH) under an amplitude of harmonic excitation of 0.1mm. In addition, the research results can be used to fabricate piezoelectric circular diaphragm energy harvester operating at a resonant frequency suitable for the available vibrations.

Abstract: The resonant frequency and Q factor of the SiC microcantilever were theoretically analyzed and calculated based on the stereotyped basic theories of the cantilever beam, and the relationship between the vibration mode and structure geometries was also simulated. Modal analysis by means of finite element method was performed on millimeter-, micron-and nanoscale microcantilevers, and the results showed that the smaller the microstructure was, the higher the resonant frequency can be obtained. The Q factor can be extracted from hamonic spectra after modal analysis, and the amplitude of Q factor was about 10⁵. This paper shows that SiC epitaxial layers have great potential in microcantilevers.

Abstract: Sensors had gained importance in all fields of science and technology and development of real time small devices with high sensitivity for in situ measurements at low cost has gained momentum. Micromachined cantilever provides a solution to this hunt. MEMS cantilever are the simplest of all the other mechanical structures and hence is considered for the ease of fabrication. Here a chemical CO₂ sensor is considered with the metal oxide layer as receptor to adsorb the CO₂ molecules leading to an increase in mass and microcantilever as the transducer part converting the change in mass to change in natural frequency. The sensitive SnO₂ layer increases the mass and hence decreases the resonant frequency. The inherent natural frequency of the cantilever is altered by the sensitive coating on top of the beam and the residual stresses present on the structure. In this paper, we investigate the SiO₂ cantilever with SnO₂ deposited on the top surface. Initially the microcantilever is analytically modelled and then is fabricated and characterized experimentally. Finally the error % is analysed between the analytical model and experimental results.

Abstract: The artificial basilar membrane has been developed to mimic the mechanical performance of the basilar membrane in the cochlea. The artificial basilar membrane consists of an array of microbridgeresonators that are mechanically sensitive to the perceived audible frequency range between 20 Hz to 20 kHz. In this work, the finite element (FE) model of the microbridge resonators have been designed in Comsol Multiphysics 4.3 to work close to the audible frequency range. The lumped element (LE) model of the microbridge resonators have been calculated and compared to the simulated FE model. The microbridge resonators array with 0.5 μm thickness, 20 μm width and length varying from 275 μm up to 7700 μm have been designed using two different materials, i.e., platinum (Pt) and aluminium (Al). The microbridge resonators have been found to mimic closely the tonotopicorganisation characteristics of the basilar membrane. From the FE and LE models of the Pt and Almicrobridge resonators, Pt has been found to be a better material than Alfor the artificial basilar membrane design. For the same geometrical dimensions, the Ptmicrobridge resonatorsoperate within the audible frequency range while the Almicrobridge resonatorsoperate approximately 43%-53% above the audible frequency range.

Abstract: This research proposes an improved tunable piezoelectric harvester structure which is constructed by a cantilever base beam and piezoelectric elements working in d33 mode. Our previous work on tunable piezoelectric harvester structure showed a frequency variation ratio of 3.17% with piezoelectric elements working in d31mode coupling. In this work, by changing the working mode of the piezoelectric elements from d31 to d33 mode, the frequency variation ratio was shown to be much higher. Theoretical analysis of the improved structure was investigated and verified with simulations. The results showed that the d33 mode coupling surpasses the d31 mode coupling with a frequency variation ratio of 29.74%.

Abstract: The effects of atmospheric particulates were more prominent in recent years, so accurate monitoring of particulate matter was a problem needed to resolve. In the existing particulate monitoring instrument based on the principle of Tapered Element Oscillating Microbalance method (TEOM),the particle concentration detection system was tapered quartz tube simple harmonic oscillator. Due to the oscillator relying mainly on analog circuit closed-loop self-excitation oscillator to drive, loop resonance frequency, oscillation stability and Q value was greatly influenced by the oscillator physical characteristics and the interference of mechanical structure and circuit design parameters. And oscillation frequency must be read by the digital circuit frequency detection system, then figured out the corresponding quality. In this paper, we studied a kind of composite oscillator tube which can overcome the lack of stability in the existing technology and reduce the impact of coexistence at the same time of digital circuit and analog circuit. And oscillator frequency step precision raised almost an order of magnitude compared with the national standard detection accuracy of 10ug.

Abstract: A silicon resonant micro-cantilever biosensor was introduced to detect biomacromolecular based on the relationship between the cantilever resonant frequency and the cantilever equivalent mass. A closed-loop self-excitation system was designed to acquire the resonant frequency of micro-cantilever. Two groups of resonant micro-cantilever sensors with different resonant frequencies of 18.192 kHz and 17.688 kHz respectively were tested. The result showed that the detection system can automatically search the resonant frequency of micro-cantilever and locked quickly. To demonstrate the feasibility of this approach, human immunoglobulin G(IgG) as model target biomacromolecular was employed, different concentration of IgG was detected by the resonant micro-cantilever sensors, the mass effect of micro-cantilever was adept and the micro-cantilever was drive by closed-loop circuit. The linearity of micro-cantilever biosensor was very well and the experimental result of sensitivity of micro-cantilever biosensor was about 6.6×10⁶. All the results showed that sensitivity of the presented immunoassay significantly increased by one-order of magnitude and offered great application promises in providing a sensitive, specific, and potent method for real-time detection of biological detection.

Abstract: The ambient energy harvesting based on piezoelectric has become an important subject in recent research publications. A new rectangular-loop piezoelectric energy harvester(RLPEH) is proposed. The characteristic is analyzed by the finite element analysis (FEA) which includes the static analysis, modal analysis and harmonic response analysis. The analysis results show that the RLPEH could reduce the resonant frequency and improve the output voltage. The three order resonant frequency is 18.6Hz, 40.8Hz and 85.4Hz. The output voltage is 42V under 3m/s2 of acceleration and the effective bandwidth is 18.7Hz with output voltage above 10V.

Abstract: The traditional elastic theory believes that there exists normal stress in pure bending body (PBB) and shear stress in pure torsion body (PTB). However, the author proved that there is no normal stress but ‘Bent Point Moment’ (BPM) in PBB. And it also concluded that there is no shear stress but ‘Shear Point Moment’ (SPM) in PTB. This article overturns the preliminary theorems of the Elasticity Theory, which believes that the value of the moment (Bending moment & Torsion moment) on a unit area converges to zero. Just as the completely different natural frequencies of the forced vibration can lead to completely different resonant conditions. Besides, this theory has also been validated in the Damage Mechanics National Key Laboratory of Tsinghua University. Therefore, it is significant to avoid destruction produced by resonance.

Abstract: Air core transformer is an essential part of mass spectrometer. Test coil is often used to measure its resonant frequency with the advantages of easy installation and high sensitivity. However, the influence of test coil while it is installed close to the working coils on the transformer is not studied before. To reveal the influence of test coil and determine the right position to install, two experiments using test coil and opened probe respectively for the measurement are conducted. Since the opened probe has little load effect on the original transformer impedance system, it can be used to validate the influence of test coil. By comparing the two experimental results, we find that the right position to install the test coil is on the further side of the primary coil to the secondary coil. This work allows us to integrate the test coil with the air core transformer to monitor the resonant frequency in real-time.