Search Results (867)

To address the torque ripple and speed fluctuation issues in high-frequency square-wave injection-based sensorless control of interior permanent magnet synchronous motors (IPMSM) caused by low-order stator current harmonics (primarily the fifth and seventh), this paper proposes a harmonic voltage compensation strategy based on a sixth-order quasi-proportional resonant (QPR) controller, which effectively suppresses these specific harmonic disturbances. The proposed method, building upon conventional high-frequency square-wave injection, introduces a harmonic current extraction technique based on multiple synchronous reference frame transformations to separate the fifth and seventh harmonic components accurately; then, according to the established harmonic voltage compensation equation, generates targeted compensation voltage commands; finally, further precisely suppresses the corresponding harmonic currents through a sixth-order QPR controller connected in parallel with the current proportional-integral (PI) controller. This paper comprehensively establishes the mathematical models for harmonic extraction and voltage compensation, and conducts a detailed analysis of the parameter design of the sixth-order QPR controller. Simulation results demonstrate that the proposed strategy can significantly suppress stator current distortion, effectively reduce torque and speed ripples, and substantially improve rotor position estimation accuracy, thereby verifying the superiority of the novel harmonic-suppression-based sensorless control strategy. Full article

This paper proposes a small-signal model of a DC–DC parallel resonant converter operating in continuous conduction mode based on asymmetric pulse-width modulation (APWM) under light-load conditions. The parallel resonant converter enables soft switching and no-load control over a wide load range because the resonant capacitor is connected in parallel with the load. However, the resonant energy required for soft switching is already sufficient, and the current flowing through the resonant tank is independent of the load magnitude; therefore, as the load decreases, the energy that is not delivered to the load and instead circulates meaninglessly inside the resonant tank increases. This results in conduction loss and reduced efficiency. To address this issue, APWM with a fixed switching frequency is required, which reduces circulating energy and improves efficiency under light-load conditions. Precise small-signal modeling is required to optimize the APWM controller. Unlike PFM or PSFB, APWM includes not only sine components but also DC and cosine components in the control signal due to its asymmetric switching characteristics, and this study proposes a small-signal model that can relatively accurately reflect these multi-harmonic characteristics. The proposed model is derived based on the Extended Describing Function (EDF) concept, and the derived transfer function is useful for systematically analyzing the dynamic characteristics of the APWM-based parallel resonant converter. In addition, it provides information that can systematically analyze the dynamic characteristics of various APWM-based resonant converters and control signals that reflect various harmonic characteristics, and it can be widely applied to future control design and analysis studies. The validity of the model is verified through MATLAB (R2025b) and PLECS (4.7.5) switching-model simulations and experimental results, confirming its high accuracy and practicality. Full article

Recent advancements in neuroimaging and genetics have generated a rapid proliferation of primary studies in these fields, leading to the development and application of meta-analytic methods, which have contributed substantially to our understanding of psychiatric and neurological disorders. The current narrative review discusses four such innovations and applications in meta-analytic techniques and how they have advanced our understanding of clinical conditions: (1) multilevel kernel density analysis (MKDA) of functional magnetic resonance imaging (fMRI) studies, (2) meta-analyses of positron emission tomography (PET) imaging of neuroinflammation, (3) Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA) Consortium neuroimaging protocols, and (4) meta-genome-wide association studies (Meta-GWASs) and polygenic risk scores (PRSs). These meta-analytic methods have contributed substantially to our understanding of psychiatric and neurological disorders by refining robust neural models, identifying transdiagnostic and disease-specific biomarkers of inflammation, uncovering numerous genetic risk variants with improved prediction models, and underscoring the polygenic and pleiotropic architecture of these conditions. Future research should continue to develop techniques for harmonizing multimodal data analysis, pursue both biomarker- and mechanism-driven approaches to discovery, and leverage biological discoveries to advance development of precision treatments and diagnostic frameworks. Full article

This paper presents a physics-informed, tacholess pipeline for smartphone-grade Noise, Vibration, and Harshness (NVH) diagnosis in electric vehicle powertrains. A configurable generator synthesizes labeled signals with order components (1×/2×/3×), AM/FM modulation, sub-harmonics, impact-driven ring-down near resonance, and realistic white/pink/ambient noise at phone bandwidths. A ridge-guided harmonic comb recenters orders without a tachometer and splits tonal from residual content. Interpretable features—order-invariant ratios ($E_{2\times }/E_{1\times }$, ${\mathrm{S}\mathrm{B}}_1$/$E_{1\times }$, $E_{0.5\times }/E_{1\times }$) and residual descriptors (band-power, kurtosis, cepstrum/WPT)—feed light-compute models. A reproducible benchmark stresses SNR (−5…+10 dB), RPM profiles (ramp/steps/cycles), and simulated domain shift; parameter-to-feature analyses (with Sobol sensitivity and a delta-method identifiability proxy) quantify measurability under phone constraints. Across a five-fold CV, tacholess order tracking increases tonal SNR by ≥+6 dB and yields macro-F1 ≈ 0.86 with Random Forest, while ordinal severity achieves QWK ≈ 0.81 (ECE ≈ 0.06) and regression attains MAE ≈ 0.12 (R² ≈ 0.78). All code, datasets, figures, and tables regenerate from fixed seeds with one-command builds; a data card and a sim-to-real guide are included. The result is an open, low-compute standard that couples reproducibility with physics-aligned interpretability, providing a practical baseline for EV NVH diagnostics with smartphones and a common ground for future field validation. Full article

This paper proposes a single-phase AC-AC solid-state transformer (SST) that eliminates bulky energy storage components. The proposed matrix-type structure comprises a line-frequency (LF) rectifier, a half-bridge (HB) LLC resonant converter, a buck–boost converter, and an LF inverter. The HB LLC resonant converter not only achieves high efficiency at unity voltage gain but also provides high-frequency (HF) isolation as a DC transformer (DCX). Meanwhile, the buck–boost converter ensures precise voltage regulation. The replacement of traditional DC-link electrolytic capacitors with small film capacitors effectively suppresses the second-harmonic power ripple, leading to a significant improvement in both power density and operational reliability. Experimental results from a 1 kW prototype demonstrate high-quality sinusoidal input and output, a wide range of zero-voltage switching (ZVS) operations, and stable output voltage control. Full article

The large-scale integration of renewable energy grid-connected converters into the grid has given rise to many broadband oscillation accidents, primarily due to impedance mismatching with the grid. Consequently, accurate measurement of both the grid-connected converter and the grid impedance is a prerequisite for system stability assessment. However, conventional impedance measurement methods are constrained by the breakdown voltage of semiconductor switches, thus rendering them unsuitable for high-voltage, high-capacity applications. This paper aims to enable impedance measurement in large-capacity, high-voltage applications by presenting a newly developed method that overcomes the voltage limitations of conventional approaches. First, a cascaded H-bridge (CHB) topology is adopted to fulfill the impedance measurement requirements in large-capacity, high-voltage renewable energy station applications. Subsequently, a quasi-proportional-resonant (PR) controlled perturbation injection strategy is proposed to achieve rapid current injection across the 10–1000 Hz frequency range. Finally, the effectiveness and accuracy of the proposed impedance measurement method in capturing harmonic impedance are demonstrated through a hardware-in-the-loop (HIL) experiment conducted on an RTDS platform. Full article

As the primary interface for integrating renewable energy sources such as wind and solar power into the grid, inverters are prone to inducing sub-/super-synchronous or medium-to-high-frequency oscillations during grid-connected operation under weak grid conditions. Optimizing the control structure of a single wind turbine inverter struggles to address multi-mode resonance issues comprehensively. Therefore, a cooperative control strategy for parallel-coupled inverters is proposed. First, a frequency-domain impedance reconstruction method for parallel wind turbines is proposed based on the phase-neutralizing characteristics and damping variation patterns of parallel-coupled impedances. Second, the damping characteristics of inverters are enhanced through the design of an additional damping controller, while the phase-frequency characteristics of wind turbines are improved using active damping based on notch filters. Finally, simulation models based on 2.5 MW permanent magnet synchronous generator (PMSG) units validate the effectiveness of the control strategy. Research results demonstrate that this cooperative control strategy effectively suppresses sub-/super-synchronous and medium-to-high-frequency oscillations: In the 0~300 Hz key oscillation band, the amplitude suppression rate of oscillating current reaches ≥60%, the total harmonic distortion (THD) of the 5th harmonic at the grid connection point decreases from 4.465% to 3.518%. Full article

Organizations increasingly rely on Agile software development to navigate the complexities of digital transformation. Agile emphasizes flexibility, empowerment, and emergent design, yet large-scale initiatives often extend beyond single teams to include multiple subsidiaries, business units, and regulatory stakeholders. In such contexts, team-level mechanisms such as retrospectives, backlog refinement, and planning events may prove insufficient to achieve alignment across diverse perspectives, organizational boundaries, and compliance requirements. To address this limitation, this paper introduces a complementary framework and a supporting software tool that enable systematic cross-stakeholder alignment. Rather than replacing Agile practices, the framework enhances them by capturing heterogeneous stakeholder views, surfacing tacit knowledge, and systematically reconciling differences into a shared alignment artifact. The methodology combines individual Functional Resonance Analysis Method (FRAM)-based process modeling, iterative harmonization, and an evidence-supported selection mechanism driven by quantifiable performance indicators, all operationalized through a prototype tool. The approach was evaluated in a real industrial case study within the regulated gaming sector, involving practitioners from both a parent company and a subsidiary. The results show that the methodology effectively revealed misalignments among stakeholders’ respective views of the development process, supported structured negotiation to reconcile these differences, and produced a consolidated process model that improved transparency and alignment across organizational boundaries. The study demonstrates the practical viability of the methodology and its value as a complementary mechanism that strengthens Agile ways of working in complex, multi-stakeholder environments. Full article

This study develops an analytical framework for investigating in-plane nonlinear subharmonic resonance in fixed–fixed circular arches under a vertical base-excitation, a phenomenon not adequately addressed in previous research. Based on Hamilton’s principle, the governing partial differential equation for in-plane nonlinear motion is first derived. The tangential displacement is then expressed as a modal superposition, and the system is reduced to a set of second-order ordinary differential equations via the Galerkin method. Using the method of multiple scales, the nonlinear 1/2-subharmonic resonance is solved, yielding closed-form, steady-state amplitude–phase relations and corresponding stability conditions. Validation against finite element simulations and Runge–Kutta analyses confirms the accuracy of the proposed approach. Dimensionless fundamental frequencies match finite element results exactly, with discrepancies in critical base-excitation below 2.5%. A close agreement is observed in both the amplitude–frequency and force–response curves with numerical predictions and Bolotin’s method, accurately capturing the characteristic hardening nonlinearity and three distinct dynamic regions spanning negligible vibration, stable resonance, and instability. Parametric studies further reveal key trends. Larger included angles intensify the vibration amplitude and promote saddle-node bifurcation, while narrowing stable operating regions. Higher slenderness ratios enhance structural flexibility and nonlinearity, shifting resonant peaks toward higher frequencies. Increased damping suppresses the response amplitude and raises the thresholds for vibration initiation and bifurcation. Full article

Within a power hardware-in-the-loop (PHIL) controller design automation (CDA) framework for voltage feedback grid-forming inverters, a scaled-down inverter system is developed for time-domain response solving. This hardware-based approach effectively addresses the conflicting demands of accuracy, computational efficiency, and modeling cost that are commonly encountered in simulation-based methods. Conventional synchronous sampling in digitally controlled pulse-width modulation (PWM) inverters introduces severe low-frequency distortion and significant ripple components in the step response, leading to non-decaying oscillations that compromise the extraction of settling time and steady-state error. By analyzing the sideband aliasing mechanism in capacitor-voltage sampling and associated harmonic-cancellation conditions, aliasing-free sampling is achieved using 90° phase-shifted anti-aliasing filters combined with synchronous sampling. Although Fast Fourier Transform (FFT) filtering offers the highest fidelity, it suffers from window-boundary distortions and is unsuitable for online use; therefore, four practical filtering schemes are evaluated against the FFT benchmark, among which oversampling with moving-average filtering (MAF) retains dynamics closest to the FFT result while avoiding its distortions. An objective function incorporating step-response metrics is constructed to optimize single-variable active damping and multiple resonant controllers, mitigating severe overshoot encountered in conventional integral-based approaches. Experimental results verify the aliasing mechanism and the effectiveness of the proposed CDA method. Full article

Piezoelectric wind energy harvesters can collect a small amount of energy from wind without the need for rotary equipment. In practice, such harvesters can be excited concurrently by wind-induced and base vibrations. In this study, combined wind and base excitation is investigated, with a focus on random base vibrations and the effect of the bandwidth of band-limited random excitation, thereby filling the research gap between results obtained with wide-band random excitation and those with harmonic excitation. Since flow-induced vibrations can produce several phenomena, in this research, galloping and vortex-induced vibration (VIV) harvesters are considered due to their structural similarity and the ease with which a galloping harvester can be converted into a VIV harvester (and vice versa). Both numerical and experimental results are presented. First, the mathematical models are given; then, experimental tests validate the models and provide an insight into the phenomena; finally, numerical simulations extend the dissertation by providing a more in-depth analysis of the behavior of such harvesters. The results show that above the critical wind velocity, galloping harvesters are not affected by the amplitude and bandwidth of random base excitation. In contrast, VIV harvesters in the lock-in condition are affected by random base excitation, especially if the vibration amplitude is large and if its spectrum is concentrated in a narrow band centered about the resonance. Full article

This study presents the design, modeling, and experimental validation of a frequency-tuned mechanical sensor (MS) integrating a fiber bragg grating (FBG) for the detection of leak-induced vibrations in pressurized steel pipelines. Unlike conventional bonded FBGs—which directly follow the local wall deformation—the proposed MS consists of a base-fiber-mass transducer geometrically tuned so that its natural frequencies coincide with the dominant vibration modes of the pipe in the 5–7 kHz range. A combined framework of finite element analysis (FEA), computational fluid dynamics (CFD), and laboratory measurements was developed to assess the coupling between the pipe and the sensor. Results show that the MS behaves as a selective mechanical amplifier, enhancing strain sensitivity and signal-to-noise ratio (SNR) by up to 15 dB compared to a directly bonded FBG. The workflow integrates modal tuning, an equivalent harmonic excitation derived from CFD-based pressure fields, and frequency–response validation, leading to a mechanically optimized FBG transducer capable of discriminating high-frequency leak signatures. The excellent agreement between the simulation and experiment confirms that geometric resonance coupling provides an effective route to amplify leak-induced strain, offering a compact, scalable, and high-sensitivity solution for vibration-based leak detection in industrial pipelines. Full article

This study proposes a practical and systematic methodology for identifying and characterizing magnetically induced noise in Column Electric Power Steering (CEPS) systems through vehicle-level testing. A coil sensor mounted on the Electric Power Steering (EPS) motor was employed to capture induced voltage signals during steering maneuvers, providing a real-time tachometric reference for order-tracking analysis. In-vehicle acoustic measurements conducted with a binaural headset revealed dominant magnetic harmonics—most notably the 24th order associated with rotor–stator interaction—and their higher-order components. To validate these observations under controlled conditions, complementary experiments were performed in a semi-anechoic chamber. Additionally, structural dynamic properties were evaluated through impact testing to distinguish electromagnetic excitations from mechanical resonances. The proposed methodology demonstrates a cost-effective and accurate approach for assessing the Noise, Vibration, and Harshness (NVH) characteristics of EPS systems, facilitating design optimization and noise mitigation without the need for extensive instrumentation or full-vehicle prototype testing. Full article

If unplanned off-grid events occur in microgrids, stable operation is disrupted. In particular, dynamic unbalanced loads, power pulse, and voltage changes also lead to system instability. To overcome these issues, this paper develops a smooth droop control strategy for multi-functional inverters. By introducing a QPR (quasi-proportional resonant) controller, the load voltage regulator is designed to compensate for the harmonic and unbalanced voltages of microgrids. Compared with traditional strategies, the proposed multi-functional inverter can reduce voltage pulses by more than 60%, and the off-grid voltage THD (total harmonic distortion) is decreased from 7% to less than 3%. At the same time, dynamic unbalanced loads and non-linear dynamic loads are both considered, and the derived strategy achieves smoother grid-connected and off-grid switching. In grid-connected mode (the microgrid connects to the distribution network at the PCC), the peak voltages and overshoots across transitions are definitely decreased, and continuous monitoring shows that the grid’s current THD stays steadily below 3%. This meets compatibility requirements, avoids harmonic interference on distribution networks, and follows the core principle of IEC TS 62898-1:2023. The simulation and experimental results verify the effectiveness of the proposed multi-function inverter control strategy for grid-connected inverters. Full article

To address the vibration issues in bearingless interior permanent magnet synchronous motors (BIPMSMs) caused by rotor mass unbalance and inverter dead-time (DT) effects during operation, a vibration suppression strategy based on a Proportional–Integral–Resonant (PIR) controller is proposed. Firstly, the mathematical model of the BIPMSM is established, and the principle of suspension force generation is analyzed. Secondly, the mechanism underlying rotor vibration is theoretically investigated. Thirdly, a PIR controller is designed by connecting a modified Proportional–Resonant (PR) controller in parallel with a Proportional–Integral (PI) controller. The proposed controller combines the ideal PR controller’s characteristic of achieving infinite gain at the resonant frequency, enabling zero steady-state error tracking for sinusoidal signals at the resonant frequency. Finally, a vibration suppression system based on the PIR controller is constructed, and simulation experiments are conducted for verification. The simulation results show that the PIR controller effectively reduces both rotor mass unbalance vibration and DT vibration in the BIPMSM, while also suppressing current harmonics during the motor’s operation. Full article