Sensors and Actuators A-physical最新文献

An arrayed ultrasonic wind measurement method based on the BNF-FLOC-MUSIC algorithm is proposed to address the issue of low measurement accuracy and poor noise suppression capabilities of current array wind measurement methods in impulse noise backgrounds. The proposed method utilizes an array structure consisting of one transmitting ultrasonic sensor and five receiving sensors. Continuous sampling is performed leveraging this structure, and the received array signals are processed using a bounded nonlinear function (BNF). Subsequently, the fractional lower-order covariance (FLOC) operations are applied to suppress impulse noise’s influence further. Finally, combining these steps with the Multiple Signal Classification (MUSIC) algorithm enables high-precision wind speed and direction measurement. The effectiveness and superiority of the method are examined through simulation experiments and actual measurement systems, and the errors of wind speed and wind direction angle in actual measurement are 1.2% and $2°$, respectively, which satisfy the design requirements of the ultrasonic anemometer.

WC/a-C composite coatings were deposited using unbalanced magnetron sputtering by adjusting the power of the WC target from 4 kW to 12 kW. The microstructure was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The results indicated the formation of a non-stoichiometric WC_x phase and an a-C phase in the WC/a-C. The WC/a-C coatings demonstrated stable electrochemical performance, characterized by a minimal amplitude of potential drift (0.01 mV) and current drift values ranging from 0.01 nA to 0.03 nA. That was attributed to the presence of amorphous carbon content (C_total/W_W-C: 0.59–1.14) within the coatings. However, the corrosion current densities (I_corr) significantly increased to 1.01×10⁻⁶ A/cm² at higher W content, while the polarization resistance (R_p) decreased to 4.4×10⁴ Ω respectively, indicating a reduction in corrosion resistance with the high WC_x phase. The WC/a-C dry electrodes exhibited stable ECG signals with well-defined PQRST waveforms, closely resembling the electrocardiograms obtained using commercial Ag/AgCl wet electrodes. The T/R ratio for WC/a-C electrodes (0.277–0.30) was found to be comparable to that of Ag/AgCl wet electrodes (0.297). These results demonstrate the suitability of dry WC/a-C electrodes for ECG applications.

Among all renewable energy sources, wind energy is a cost-effective alternative energy source. The majority of wind turbines are built in harsh environments due to their power generation characteristics, which is one of the prime reasons resulting in frequent failures of wind turbine. Among various failures, the vibration of wind turbine tower cannot be ignored because it is a precursor of the failure of the wind turbine. The electrical vibration sensors have the problems of power supply and electromagnetic interference for the condition assessment of wind turbine tower. A vibration sensor based on optical Fabry-Perot (F-P) interference principle with high sensitivity is designed, fabricated and characterized to further meet the requirements of vibration detection of wind turbine tower. The mechanical simulation model of the diaphragm and optical vibration platform is constructed to verify the sensing characteristic of the F-P optical fiber vibration sensor (OFVS). The experiment results indicate a resonant frequency of the F-P OFVS of 223 Hz, an output sensitivity of 122.22 mV/m·s⁻² at 10 Hz, and a horizontal output of less than 6 %. In addition, the designed F-P OFVS possesses the superiorities of compact structure, passive and excellent anti-electromagnetic interference, and has a wide application prospect in the vibration detection of the wind turbine tower.

We developed a new approach to the fabrication of MEMS substrates for MOS gas sensors. This full screen-printing process is based on the application of sacrificial material, which is solid at the near-room temperature of printing and turns to powder after the firing of the elements of the sensor. Therefore, this sacrificial material can be removed from under the suspended elements of the MEMS structure in ultrasonic bath. The glass-ceramic MEMS is a cantilever structure equipped with a Pt-based microheater made of Pt resistive material with sheet resistance of about 4 Ohm/square fabricated using core-shell technology. It is located at the end edge of the cantilever and is isolated from the contacts to the sensing layer by glass-ceramic insulation. Screen-printing provides cheap fabrication, robustness and low power (∼120 mW@450°C) of the sensing element. The functionality of the microhotplate was checked using ZnO nanomaterial deposited by microextruder, it demonstrated high response and selectivity of ZnO material to NO₂ (response 41.6 at 200°C for 10 ppm).

We propose and demonstrate an accurate method of measuring the effective refractive index of silicon-on-insulator waveguides. By conducting the combined analysis to the troughs’ wavelength in spectra of Mach–Zehnder interferometers on chip. The wavelength-dependent and temperature-dependent effective refractive index of the fabricated waveguides are measured experimentally, and obtained the thermo-optic coefficient of silicon-on-insulator waveguides is about 2×10⁻⁴ /℃ in the 1550 nm communication band. The maximum measurement error for effective and group refractive index respectively are 1.5×10⁻⁵ and 1.5×10⁻³ obtained by numerical simulation. And an improved method for taking value of the free spectral range was discussed to obtain a more accurate group refractive index. It proves a fast and lost-cost measurement way to evaluate key optical parameters of waveguide, which can indicate the quality of fabrication process and optimize photonic components.

Piezoelectric stick-slip actuators (PSSAs) utilize sliding friction between the mover and stator to convert and transmit motion. However, the phenomenon of backward displacement often hinders the output performance of PSSAs. This paper proposes a method to mitigate backward displacement and enhance output performance by modifying the overall flexibility of the actuator. The key idea of this approach is to propose a novel flexible hinge structure and apply it to PSSA. Numerical calculations and finite element analysis confirm that the flexibility and output performance of the PSSA are significantly improved. The method's feasibility is supported by comparing experiments. The experimental results show that under the same locking force, the optimal excitation frequency of perforated Elliptical Flexure Hinge (EFH) is significantly lower than the non-perforated EFH and the speed is increased over 53 %. Furthermore, the PSSA has a maximum load capacity of 190 g, which is 31.7 times its own weight (6 g). The proposed PSSA can provide valuable insights for its application in precision motion control systems in the foreseeable future.

The accuracy of speech recognition through an air-conducted microphone can be less accurate under a highly noisy environment or when the volume of the user’s voice is relatively low. One solution to this problem is the use of contact microphones. However, neither the microphone locations that provide optimal speech recognition accuracy for each user nor the mechanisms underlying these contact forces have been clarified. In this study, we experimentally investigated the effects of placement, contact force, user gender, and speech recognition platform on the accuracy of speech recognition with contact microphones placed on the surface of the head and neck. The experimental results indicated that the mechanism underlying the influence of each factor on speech recognition accuracy differs for speech acquired at the neck and head locations. In particular, the effect of the user’s gender was significant for the neck-acquired sound, but not the head-acquired sound. The results also revealed that the microphone contact force did not affect the recognition accuracy or user discomfort for the head-acquired sound. Moreover, the results of speech recognition experiments in a simulated noisy environment showed that bone-conducted sounds acquired on the head and neck surfaces were more robust than air-conducted sounds.

It is well known that ultra-wideband (UWB) is widely used in building indoor positioning systems (IPS) because of its unique advantages. However, compared with the line-of-sight environment (LOS), UWB localization on none-line-of-sight (NLOS) channels has certain limitations, which will reduce the UWB ranging accuracy and location reliability in indoor environment. In this paper, a neural network (NN)-enhanced UWB positioning method is proposed. It can improve positioning performance by using the received channel impulse response (CIR) and UWB raw ranging data to classify the channel conditions and predict the distance. By training CNN-LSTM and MLP neural networks, the proposed method can alleviate the deterioration of localization performance caused by NLOS. The experimental results showed that the average NLOS recognition accuracy of five different obstacles including wooden doors, concrete walls, metal shelves, human body and glass windows reaches up to 92.36 %. In addition, the average root mean square error (RMSE) between the predicted distance and the true distance was 0.3123 m. The indoor positioning test was carried out by weighted least squares (WLS) and the average positioning error under three trajectories was 0.1223 m, which improved the performance by 83.56 % compared with the original UWB positioning system, thus proving its ability to reduce positioning degradation.

Magnetic field vector information is crucial for many advanced applications, such as navigation and biomedical imaging. However, existing methods often lack high sensitivity or require complex setups. This study addresses these challenges by proposing a novel vector magnetometry method using a single-beam optically pumped magnetometer. A rotating radio-frequency field is innovatively utilized to excite atomic spin precession, enabling accurate measurement of the magnetic field direction based on scalar measurement. The method is tested through physical experiments with different magnetic field configurations to validate its performance. The experimental results demonstrate high accuracy, and achieve a magnetic field amplitude sensitivity of 800 fT/Hz${}^{1/2}$, an azimuth sensitivity of 100 $\mu$rad/Hz${}^{1/2}$, and a polar angle sensitivity of 13 $\mu$rad/Hz${}^{1/2}$. The proposed method facilitates sensor miniaturization and is suitable for applications in high magnetic field environments, such as geomagnetic field.