Search Results (116)

The control of following motion under mesoscale gap flow fields has important applications. The flexible characteristics of the plant, wideband time-varying disturbances caused by the flow field, and requirements of high precision and low overshoot make achieving submicron level accuracy a significant challenge for traditional control methods. This study adopts the control concept of Disturbance Observer Control (DOBC) and uses H_∞ mixed-sensitivity shaping technology to design a Q-filter. Simultaneously, multiple control techniques, such as high-order reference trajectory planning, Proportional-Integral-Derivative (PID) control, low-pass filtering, notch filtering, lead lag correction, and disturbance rejection filtering, are applied to obtain a control system with a high open-loop gain, sufficient phase margin, and stable closed-loop system. Compared to traditional control methods, the new method can increase the open-loop gain by 15 times and the open-loop bandwidth by 8%. We even observed a 150-time increase of the open-loop gain at the peak frequency. Ultimately, the method achieves submicron level accuracy, making important advances in solving the control problem of semiconductor equipment. Full article

Eddy current testing (ECT) has become a widely adopted technique for non-destructive testing (NDT) due to its effectiveness in detecting surface and near-surface defects in conductive materials. However, traditional methods mainly focus on defect detection and face significant challenges in extracting geometric information such as defect size and shape, which is crucial for structural health monitoring (SHM) and remaining useful life (RUL) assessment. To address these challenges, this study proposes a defect reconstruction approach based on a complex-valued convolutional neural network (CV-CNN), which directly leverages both amplitude and phase information inherent in complex-valued impedance signals. The proposed framework employs convolution, pooling, and activation operations specifically designed within the complex-valued domain to facilitate the high-fidelity reconstruction of defect morphology as well as precise multi-class defect classification. Notably, this approach processes the complete complex-valued signal without relying on prior structural parameters or baseline data, thereby achieving substantial improvements in both defect visualization and classification performance. Moreover, when compared to a complex-valued fully convolutional neural network (CV-FCNN), CV-CNN demonstrates a superior average classification accuracy of 85%, significantly outperforming the CV-FCNN model. Experimental results on carbon steel specimens with standard electrical discharge machining (EDM) notches under multi-frequency excitation confirm these advantages. This contribution provides a promising solution in the field of NDT for intelligent and precise defect detection. Full article

This article presents a low-noise amplifier (LNA) with high image rejection ratio (IRR) operating in the 5G millimeter-wave band using a 65 nm CMOS process. The circuit adopts an inter-stage notch filtering structure composed of a transformer and a switched capacitor array to achieve image suppression and impedance matching with no die area overhead. By adjusting the values of the switch capacitor array, the transmission zeros are positioned in the stopband while the poles are placed in the passband, thereby realizing image rejection. Furthermore, the number and distribution of poles under the both real and complex impedance conditions are analyzed. Moreover, the quality factor (Q) of the zero is derived to establish the relationship between Q and the image rejection ratio, guiding the optimization of both gain and IRR of the circuit design. Measurement results demonstrate that the LNA exhibits a gain of 18 dB and a noise figure (NF) of 4.4 dB at 40 GHz, with a corresponding IRR of 53.4 dB when the intermediate frequency (IF) is 6 GHz. The circuit demonstrates a 3 dB bandwidth from 36.3 to 40.7 GHz, with an IRR greater than 42 dB across this frequency range. The power consumption is 25.4 mW from a 1 V supply, and the pad-excluded core area of the entire chip is 0.13 mm². Full article

Background: Occupational hearing loss (OHL) is a primary concern in industrial settings. In hospitals, the healthcare workers are also exposed to noise and chemical agents, the reported hearing loss in this occupation is underestimated. Hearing examination is routinely evaluated in the range of conventional frequencies, which may not detect hearing problems early. Therefore, this study aimed to reveal the hearing thresholds among medical personnel exposed to loud noise and/or chemical environments, estimating the prevalence of hearing loss using four different audiological methods. Methods: One hundred and thirty-one medical personnel were recruited from different units at the same hospital and grouped into noise, chemical, and mixed exposure categories. The hearing thresholds were assessed using four audiological methods, conventional audiometry (CA), extended high-frequency audiometry (EHFA), standard frequency distortion product otoacoustic emission (DPOAE), and ultra-high-frequency DPOAE. Statistical analyses were performed using R. Results: Ultra-high-frequency DPOAE and EHFA showed a higher prevalence of hearing loss than CA and DPOAE. Even CA usually demonstrated hearing threshold within normal limits, this study found a notch audiogram pattern indicating a decline in hearing loss over time at frequencies of 2, 3, and 4 kHz in each age group and a sign at a frequency of 6 kHz. Conclusions: Evidence of hearing loss can be identified with ultra-high-frequency DPOAE and EHFA, despite conventional audiometry indicating normal hearing thresholds. Full article

This paper evaluates the performance of strategies based on finite-control-set model predictive control (FCS-MPC) aimed at reducing or fixing the converter switching frequency or decreasing the spread of the harmonic spectrum in multilevel hybrid cascade converters (HCCs). These properties are desirable for medium- to high-voltage applications, where minimizing switching losses is crucial, as well as for applications employing passive filters, where resonance modes can be excited. The strategies evaluated are input restriction, notch filtering, period control, and PWM restriction. Key aspects considered in this work are (i) the evaluation of the steady-state and transient performance of FCS-MPC strategies proposed for two-level converters in a multilevel topology, and (ii) the evaluation of the computational cost associated with the implementation of these strategies on a multilevel converter with a high number of available inputs. As a typical application, the study is carried out employing a five-level HCC experimental prototype driving an induction motor through indirect vector control. To perform a fair comparison between the strategies, a control platform based on a cost-effective Zynq system on chip is proposed, which allows for achieving the hard timing constraints imposed by FCS-MPC strategies. The results show that the PWM restriction strategy achieves the best steady-state performance among the evaluated strategies, with an error 400 times smaller than that of the second-best strategy (input restriction), with an average switching frequency of 962.5 Hz, which differs from the desired average frequency by 3%, and a maximum difference in power distribution between modules of 0.8%. In addition, the system-on-chip hardware achieves a competitive execution time of 46 μs when the ARM Cortex solution is implemented and 20 μs when the ARM Cortex–FPGA solution is used instead, employing the 512 inputs available in the FCS-MPC algorithm. The studies, performed in steady-state and transient regimes, confirm (i) the feasibility of the evaluated algorithms in an HCC topology and (ii) the feasibility of the control platform for implementing high-computational-burden algorithms with a low sampling time. Full article

This paper proposes a detailed design study of resonating high-frequency notch filters driven by RF MEMS switches and their optimization for dual-band operation in the X-Band. Microstrip configurations will be considered for single and dual-band applications. An SPDT (single-pole-double-thru) switch composed of double-clamped ohmic microswitches has been introduced to connect triangular resonators with Sierpinski geometry, symmetrically placed with respect to a microstrip line to obtain a dual notch response. Close frequencies or spans as wide as 2 GHz can be obtained depending on the internal complexity and the edge side. The internal complexity has been modified to introduce the possibility of using the same edge size for the frequency tuning of an elementary cell, maintaining a fixed footprint, and allowing coupled structures to implement high-frequency filters of the same size and variable operational frequencies. Preliminary experimental results have been obtained as a confirmation of the predicted device functionality. Full article

This paper aims to investigate the effectiveness of cutting fluid during the high-speed face-turning of superalloy Inconel 718 using chamfered whisker-reinforced ceramic inserts. It addresses this topic by providing a comprehensive understanding of the machinability of Inconel 718 under both dry and wet conditions through analytical friction modeling and a detailed analysis of the chip formation process. Two new indexes, named the Area Function (AF) and the Shape Function (SF), were derived to assess the serration intensity of the chips. Particular attention was paid to the interaction between the cutting speed and the cutting fluid. The results showed that wet conditions promote uniform chip formation, more stable forces, a lower coefficient of friction, and the absence of notch wear. At low cutting speed (60 m/min) and dry machining results in high serration intensity (SF = 0.7) and segmentation frequency ($f_{seg}$ = 22.08 kHz) compared to the SF of 0.4 and $f_{seg}$ = 19.69 kHz in wet conditions. The segmentation frequency increases significantly with cutting speed, reaching 71.03 kHz and 63.32 kHz at a cutting speed of 225 m/min for dry and wet conditions, respectively. It was also found that the rate of increase in the tangential force was lower (20.49 N/s) when using cutting fluid at a high cutting speed (225 m/min) compared to dry conditions (27.37 N/s). Full article

This paper proposes an adaptive fuzzy controller based on a switching notch filter to address the rotor unbalance vibration control problem of an active magnetic bearing (AMB) high-speed motor system in the full rotational speed range. Aiming at the complex nonlinear and time-varying characteristics of the AMB rigid rotor system, this study designs an adaptive fuzzy controller (AFC) that obtains fuzzy quantities by blurring the rotor vibration information and vibration rate of change as the input signals and then obtains the fuzzy set through fuzzy reasoning and modifies the parameters of the initial fuzzy controller. The initial fuzzy controller parameters are modified through fuzzy reasoning to improve the control effect and ensure the stable suspension of the rotor during high-speed rotation. At the same time, in order to effectively suppress the vibration of the rotor in high-speed operation due to unbalance and other factors, this paper introduces an adapting notch filter (ANF) as a vibration control strategy on the basis of AFC, and the notch filter is able to monitor the rotor vibration signals and adaptively adjust the center frequency and bandwidth. Finally, the correctness and effectiveness of the adaptive fuzzy controller based on a switching notch filter (AFC-ANF) are verified via simulations and experiments. The simulation results demonstrate that compared to traditional PID control, the AFC reduces the response time by 0.11 s. Under constant-speed operating conditions, the AFC-ANF strategy decreases rotor vibration by 60%, while under variable-speed conditions, it reduces rotor vibration displacement by 40%, showcasing significant vibration suppression effectiveness. This research provides a novel solution for vibration control in magnetic bearing systems, offering both important theoretical significance and practical application value. Full article

Featured with optimal power consumption, active magnetic bearings (AMBs) have been extensively integrated into turbomachinery applications. For turbomachinery components, including the rotor and impeller, their connection is generally based on bolted joints, which would easily induce excessive interface contact. As a result, the pre-tightening torque can induce modal vibrations in the rotor upon levitation. Although a notch filter can be adopted to suppress the vibrations, it should be noted that the current reported notch filters are based on fixed center frequency, making it challenging to enable high effectiveness over a broad range of rotor speeds, particularly in cases where the gyroscopic effect is significant. Herein, a modal vibration suppression based on a varying-frequency notch filter is proposed, considering gyroscopic effect and interface contact. First, the rotor–AMB system was developed, taking into consideration the bolted-joint interface contact. This modeled the effect of the interface contact as a time-varying force in the positive feedback. Secondly, the relationship between vibration frequency and rotational speed was obtained, based on simulations. Lastly, a test rig was configured to validate the performance of the frequency-varying notch filter. The experimental data confirm that the filter is capable of attenuating the modal vibrations resulting from interface contact across all operational speeds. Full article

This paper proposes a three-stage op amp based on the SOI (silicon-on-insulator) process, which achieves a low offset voltage and temperature coefficient across a wide temperature range from −40 °C to 250 °C. It can be used in aerospace, oil and gas exploration, automotive electronics, nuclear industry, and in other fields where the ability of electronic devices to withstand high-temperature environments is strongly required. By utilizing a SC (Switched Capacitor) notch filter, the op amp achieves low input offset in a power-efficient manner. The circuit features a multi-path nested Miller compensation structure, consisting of a low-speed channel and a high-speed channel, which switch according to the input signal frequency. The input-stage operational amplifier is a fully differential, rail-to-rail design, utilizing tail current control to reduce the impact of common-mode voltage on the transconductance of the input stage. The two-stage operational amplifier uses both cascode and Miller compensation, minimizing the influence of the feedforward signal path and improving the amplifier’s response speed. The prototype op amp is fabricated in a 0.15 µm SOI process and draws 0.3 mA from a 5 V supply. The circuit occupies a chip area of 0.76 mm². The measured open-loop gain exceeds 140 dB, with a 3 dB bandwidth greater than 100 kHz. The amplifier demonstrates stable performance across a wide temperature range from −40 °C to 250 °C, and exhibits an excellent input offset of approximately 20 µV at room temperature and an offset voltage temperature coefficient of 0.7 μV/°C in the full temperature range. Full article

This paper explores the potential of phase change materials (PCM) for dynamically tuning the frequency response of a dumbbell u-slot defected ground structure (DGS)-based band stop filter. The DGSs are designed using co-planar waveguide (CPW) line structure on top of a barium strontium titanate (Ba_0.6Sr_0.4TiO₃) (BST) thin film. BST film is used as the high-dielectric material for the planar DGS. Lower insertion loss of less than −2 dB below the lower cutoff frequency, and enhanced band-rejection with notch depth of −39.64 dB at 27.75 GHz is achieved by cascading two-unit cells, compared to −12.26 dB rejection with a single-unit cell using BST thin film only. Further tunability is achieved by using a germanium telluride (GeTe) PCM layer. The electrical properties of PCM can be reversibly altered by transitioning between amorphous and crystalline phases. We demonstrate that incorporating a PCM layer into a DGS device allows for significant tuning of the resonance frequency: a shift in resonance frequency from 30.75 GHz to 33 GHz with a frequency shift of 2.25 GHz is achieved, i.e., 7.32% tuning is shown with a single DGS cell. Furthermore, by cascading two DGS cells with PCM, an even wider tuning range is achievable: a shift in resonance frequency from 27 GHz to 30.25 GHz with a frequency shift of 3.25 GHz is achieved, i.e., 12.04% tuning is shown by cascading two DGS cells. The results are validated through simulations and measurements, showcasing excellent agreement. Full article

Radio photonic technologies have emerged as a promising solution for addressing microwave frequency synthesis challenges in current and future communication and sensing systems. One particularly effective approach is the optoelectronic oscillator (OEO), a simple and cost-effective electro-optical system. The OEO can generate microwave signals with low phase noise and high oscillation frequencies, often outperforming traditional electrical methods. However, a notable disadvantage of the OEO compared to conventional signal generation methods is its significant frequency tuning step. This paper presents a novel approach for continuously controlling the output frequency of an optoelectronic oscillator (OEO) based on integrated photonics. This is achieved by tuning an integrated optical delay line within a feedback loop. The analytical model developed in this study calculates the OEO’s output frequency while accounting for nonlinear errors, enabling the consideration of various control schemes. Specifically, this study examines delay lines based on the Mach–Zehnder interferometer and microring resonators, which can be controlled by either the thermo-optic or electro-optic effect. To evaluate the model, we conducted numerical simulations using Ansys Lumerical software. The OEO that utilized an MRR-based electro-optical delay line demonstrated a tuning sensitivity of 174.5 MHz/V. The calculated frequency tuning sensitivity was as low as 6.98 kHz when utilizing the precision digital-to-analog converter with a minimum output voltage step of 40 μV. The proposed approach to controlling the frequency of the OEO can be implemented using discrete optical components; however, this approach restricts the minimum frequency tuning sensitivity. It provides an additional degree of freedom for frequency tuning within the OEO’s operating range, which is ultimately limited by the amplitude-frequency characteristic of the notch filter. Thus, the proposed approach opens up new opportunities for increasing the accuracy and flexibility in generating microwave signals, which can be significant for various communications and radio engineering applications. Full article

Railway traction motor bearings (RTMB) are critical components in high-speed trains (HST) that are particularly susceptible to failure due to the high stress and rotational frequency they experience. To address the challenge of high false-positive rates in existing monitoring systems, this paper introduces a novel sensorless monitoring scheme that leverages stator current to detect fault-related characteristics, eliminating the need for additional sensors. This approach employs a hybrid signal preprocessing algorithm that integrates adaptive notch filtering (ANF) with envelope spectrum analysis (ESA) to effectively sparse the stator current and extract relevant fault features. A deep belief network (DBN) is utilized for the classification of the health status of the RTMB. To validate the scheme’s feasibility and effectiveness, we conducted experiments on a 1:1 scale high-speed railway traction motor, demonstrating that mechanical defects in RTMB can be reliably indicated by changes in stator current. Based on the analysis of experimental results, it was concluded that the fault detection accuracy of RTMB based on stator current is at least 17.3% higher than that of the fault diagnosis methods based on vibration in diagnosing whether the system has a fault. Among them, the method proposed in this paper is the best in diagnosing the presence and type of faults, with an accuracy that is at least 8.9% higher than other methods. This study not only presents a new method for RTMB monitoring but also contributes to the field by offering a more accurate and efficient alternative to current practices. Full article

(AlCrNbSiTiMo)N high-entropy alloy films with different nitrogen contents were deposited on tungsten carbide substrates using a radio-frequency magnetron sputtering system. Two different types of targets were used in the sputtering process: a hot-pressing sintered AlCrNbSiTi target fabricated using a single powder containing multiple elements and a vacuum arc melting Mo target. The deposited films were denoted as R_N0, R_N33, R_N43, R_N50, and R_N56, where R_N indicates the nitrogen flow ratio relative to the total nitrogen and argon flow rate (R_N = (N₂/(N₂ + Ar)) × 100%). The as-sputtered films were vacuum annealed, with the resulting films denoted as HR_N0, HR_N33, HR_N43, HR_N50, and HR_N56, respectively. The effects of the nitrogen content on the composition, microstructure, mechanical properties, and tribological properties of the films, in both as-sputtered and annealed states, underwent thorough analysis. The R_N0 and R_N33 films displayed non-crystalline structures. However, with an increase in nitrogen content, the R_N43, R_N50, and R_N56 films transitioned to FCC structures. Among the as-deposited films, the R_N43 film exhibited the best mechanical and tribological properties. All of the annealed films, except for the HR_N0 film, displayed an FCC structure. In addition, they all formed an MoO₃ solid lubricating phase, which reduced the coefficient of friction and improved the anti-wear performance. The heat treatment HR_N43 film displayed the supreme hardness, H/E ratio, and adhesion strength. It also demonstrated excellent thermal stability and the best wear resistance. As a result, in milling tests on Inconel 718, the R_N43-coated tool demonstrated a significantly lower flank wear and notch wear, indicating an improved machining performance and extended tool life. Thus, the application of the R_N43 film in aerospace manufacturing can effectively reduce the tool replacement cost. Full article

Recently, the increasing concern for climate control has led to the widespread application of grid-connected inverter (GIC)-based renewable-energy systems. In addition, the increased usage of non-linear loads and electrification of the transport sector cause ineffective grid-frequency management and the introduction of harmonics. These grid conditions affect power quality and result in uncertainty and inaccuracy in monitoring and measurement. Incorrect measurement leads to overbilling/underbilling, ineffective demand and supply forecasts for the power system, and inefficient performance analysis. To address the outlined problem, a novel, three-phase frequency component extraction and power measurement method based on Digital Lock-in Amplifier (DLIA) and Digital Lock-in Amplifier–Frequency-Locked Loop (DLIA–FLL) is proposed to provide accurate measurements under the conditions of harmonics and frequency offset. A combined filter, with a lowpass filter and notch filter, is employed to improve computation speed for DLIA. A comparative study is performed to verify the effectiveness of the proposed power measurement approach, by comparing the proposed method to the windowed interpolated fast Fourier transform (WIFFT). The ZERA COM 3003 (a commercial high-accuracy power measurement instrument) is used as the reference instrument in the experiment. Full article