This reprint focuses on state-of-the-art vibration sensing and energy harvesting technologies. The 11 chapters can be divided into three aspects: (i) new materials for vibration energy harvesting ...applications, (ii) design and fabrication of vibration energy harvesters (VEHs), and (iii) system-level integration and testing of VEHs.
This reprint focuses on state-of-the-art vibration sensing and energy harvesting technologies. The 11 chapters can be divided into three aspects: (i) new materials for vibration energy harvesting ...applications, (ii) design and fabrication of vibration energy harvesters (VEHs), and (iii) system-level integration and testing of VEHs.
This paper presents the design, fabrication, and characterization of a MEMS actuator with large static deflection as a waveguide-mounted variable millimeter-wave phase shifter. The actuator is ...composed of a pair of interdigitated microplates actuated by vertical comb-drives and suspended by SU-8 torsional springs. The SU-8 spring possesses a thin metallization top layer and a reverse-T-shaped cross-section enabling low torsional stiffness and high in-plane stability. A maximum mechanical deflection of 10.3° is obtained under a dc actuation voltage of 35 V. The dynamic characterization of the device shows that the resonance frequency of the torsional mode is well separated from the other three bending modes, confirming the designed low torsional stiffness and high in-plane stability. The torsional viscoelastic creeping is measured as a function of time at different loads and shows a maximum of 0.5° for an applied voltage of 27.5 V. A high operation cycle test is conducted and the metalized SU-8 spring withstands 800 million cycles without showing fatigue. RF measurements show that a variable mechanical deflection angle between 0° and 8.2° results in a variable transmission phase shift up to 58.0°. The measured insertion loss is always below 5.1 dB at 98 GHz, corresponding to a figure of merit of 11.5°/dB.
A new honeycomb production process was proposed with both filter cake (from hydrothermal treatment of metatitanic acid) and industrial titanium dioxide as Ti sources. The strength of the obtained ...pilot product was comparable with the current industrial honeycomb product from only filter cake, but its denitration (DeNOx) efficiency was elevated up to 15 percentage points. Multiple characterizations revealed the filter cake and industrial titanium dioxide to be composed of primary particles and secondary particles, respectively, and the introduced secondary particles from industrial titanium dioxide resulted in increased specific surface area and pore size/volume, facilitating the exposure of more active sites with improved activity. Moreover, a positive correlation property was found between the honeycomb strength and crystallinity for the samples from different titanium sources. The filter cake with rich hydroxyl groups and weak crystallinity could be fused more easily among these primary particles to have a higher strength than industrial titanium dioxide, and the primary particle of the filter cake could fill the pile pore of industrial titanium dioxide and act as a solid phase binder to acquire good strength for the honeycomb using both the filter cake and titanium dioxide as Ti sources. The improved honeycomb product with good activity and strength may have more widespread application for the purification of low temperature flue gas in industry.
A second-order bandpass filter (BPF) with continuously variable centre frequency tuning is presented in this article. Evanescent-mode cavity resonators with variable capacitive loadings are used as ...tuning elements. Tuning is achieved by means of micro-electromechanical-systems (MEMS)-actuated highly conductive rigid fingers that feature an out-of-plane deflection. For an applied DC bias voltage between 0 and 27.3 V the centre frequency of the BPF is tuned from 67.4 to 63.2 GHz (4.2 GHz). For this frequency band, the fractional bandwidth (FBW) varies between 8.3 and 3.4% and the in-band insertion loss between 1.45 and 5 dB.
•A sensor array comprising four gas sensors has been utilized to detect 11 types of mixtures of NO2 and CO, whose concentration varies from 0 to 50ppm. The range of mixed gas concentration is wide ...enough, and the theoretical LOD could reach dozens of ppb levels.•Features were extracted by principal component analysis (PCA), and then C-means clustering and back propagation neural network (BPNN) were employed to identify gases. Also, we have verified the optimized effect of genetic algorithm (GA) for BPNN. Through transforming response curves into gray image, CNN could be used to directly recognize various gases.•To investigate which feature of input sample is most influential to BPNN model, a random variable substitution method has been proposed.•Experiments for sensing 6 kinds of CO and NO2 mixtures under 4 different relatively humidity (25%, 33%, 50%, 75%) have been implemented to evaluate the effect of environmental humidity on our sensor array. The results demonstrated our method could eliminate the effects of humidity.•Even though this work stressed on the identification of mixtures of NO2 and CO, the approach presented here is generic, and could in principle, be extended to other relevant gas species.
In this work, a sensor array comprised four sensors has been employed to detect 11 types of mixtures of nitrogen dioxide (NO2) and carbon monoxide (CO), with concentration varying from 0 to 50 ppm. To reduce the effect of sensor noise and ensure high recognition accuracy, average resistance over a period of time was introduced. Then, 12 features including response value, response time and recovery time were extracted from each sample. After that, C-means clustering and back propagation neural network (BPNN) were performed to identify various gases, with classification accuracy of 94.55 % and 100 %, respectively. Genetic algorithm (GA) was also employed to further improve BPNN’s performance. Moreover, a random variable substitution method has been introduced to study which feature of the input sample influence the BPNN model most. Through gray processing, dynamic curves have been transformed into gray images, from which convolutional neural network (CNN) was introduced to automatically extract high-level features, and an identification accuracy of 100 % has been realized. Finally, experiments for sensing gas mixtures of CO and NO2 under various humidity levels have been done to test the impact of humidity on the sensor array. The results demonstrated the proposed method could eliminate the effects of humidity.
A Self-Powered Vibration Sensor With Wide Bandwidth Li, Yunjia; Wang, Yuzhu; Cao, Qi ...
IEEE transactions on industrial electronics (1982),
2020-Jan., 2020-1-00, 20200101, Volume:
67, Issue:
1
Journal Article
Peer reviewed
A self-powered vibration sensor based on electromagnetic induction is presented in this paper. The vibration sensor is implemented with stacked flexible coils and polymeric springs. The stacked ...flexible coil enables large output signal, while long and flexible springs enable high sensitivity and wide linear range of the sensor. At resonance, the sensor has a sensitivity of 1.83 V/g and a maximum resolution of 0.002 g. In the high-frequency range, where the sensor output is frequency-independent (100-3000 Hz), the sensor has a sensitivity of 66.5 mV/g, a maximum resolution of 0.05 g, and a measurement range up to 8.5 g.
The position sensorless permanent magnet synchronous motor (PMSM), with its simple structure, is applied in the aerospace field with high reliability requirements. To drive PMSM safely, the ...three‐phase current measured from the driver needs to be isolated for the closed‐loop control. And then, the accuracy current measurement is crucial for achieving optimal motor performance. In the paper, current transformer (CT) with centre taps is employed to isolate and measure the high‐frequency current of the inverter switch. Additionally, an algorithm is proposed to reconstruct the switch current into the low‐frequency phase current. Subsequently, the measuring method and the algorithm are applied to an inverter platform, which drives a 100W PMSM. Finally, the reconstructed phase current waveform is compared with the measured phase current waveform, and the experimental results show that the above method is effective and feasible.
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