Phase Synchronization Method Research Articles

An I/Q Phase Detection-Based Harmonic- Insensitive Phase Synchronization Method for Bidirectional Wireless Power Transfer System

An I/Q Phase Detection-Based Harmonic- Insensitive Phase Synchronization Method for Bidirectional Wireless Power Transfer System

Deep learning approach for detection of unfavorable driving state based on multiple phase synchronization between multi-channel EEG signals

In recent years, electroencephalogram (EEG) signals have gained significant popularity in the detection and recognition of drivers' unfavorable driving states (UDS) and related aspects. However, the methods that rely on traditional EEG features and evaluate different electrodes or brain regions separately have somewhat limited the further development of recognition effectiveness. To address this, this study analyzes the phase relationships between electrodes in EEG signals to reveal the functional networks and connectivity patterns within the brain. Three phase synchronization (PS) methods, namely phase locking value (PLV), corrected imaginary phase locking value (CIPLV), and weighted phase lag index (WPLI), are used to construct connectivity matrices and networks in six classic sub-rhythmic bands. Additionally, a 2D convolutional neural network (CNN) with fewer learning parameters is designed to automatically learn high-level abstractions and the most discriminative features, thereby avoiding the laborious and subjective process of manual feature extraction. The proposed method has been compared with traditional classification algorithms using a leave-one-out cross-validation strategy. The comparative results indicate that our proposed approach, which combines WPLI phase synchronization in the gamma1 sub-rhythmic band with a pyramid-structured CNN model, achieves significantly higher accuracy in recognizing drivers' UDS than other conventional methods through a one-way analysis of variance (ANOVA) followed by post hoc multiple comparisons with Tukey analysis. Furthermore, our proposed 2D-CNN model contains fewer parameters, making it more competitive for further practical applications in real-world driving scenarios.

Robust Parity-Time-Symmetric WPT System With Reduced Switching-Frequency and Improved Step-Down Conversion Ratio

In this paper, combining the phase synchronization method (PSM) and high harmonic operation (HHO), a novel parity-time(PT)-symmetric wireless power transfer (WPT) system with reduced switching frequency and improved step-down conversion ratio is proposed, where the power transferred to receiver side is carried by the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> th harmonic. We demonstrate that constant current (CC) and constant voltage (CV) independent of coupling coefficient and load resistance can also be obtained without wireless communication and additional dc-dc converters. Here, a new implementation of a negative resistor based on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> th harmonic operation is proposed, which is a necessary condition of a PT-based system. In contrast to the standard PT-based system with the same resonant frequency, the switching frequency is reduced to 1/n due to the use of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> th harmonic, thereby realizing low switching losses and high system efficiency. Besides, an inherently improved step-down conversion ratio can be obtained. A prototype with a 6 A charging current and a 36 V charging voltage is built to verify the feasibility of the proposed method.

Open-loop Phase Synchronization Method of Positive and Negative Sequences for Three-phase Asymmetric Grid

Open-loop Phase Synchronization Method of Positive and Negative Sequences for Three-phase Asymmetric Grid

Fast prediction method for multirotor global tonal noise based on acoustic modal analysis

With the popularity of multirotor aircraft, the aerodynamic noise it generates has an increasingly serious impact on the environment. A fast method for globally predicting the tonal noise is proposed in this study. The goal of this method is to predict the global aerodynamic noise at a small computational cost, then providing a fast model for online noise prediction and control. Firstly, the global noise model of a single rotor in acoustic modal domain is established by using the near-field acoustic holography method. Then, the global noise model of a rotor with different configurations is obtained by using the mapping relationship of acoustic modal coefficients. Subsequently, the global noise of multirotor is predicted based on the configuration information of rotors by using the wave superposition principle. To validate the performance of this method, the predicted global noises of single rotor and multi rotors were compared with other numerical methods. It is revealed that the acoustic modal analysis can accurately predict global noise at a small computational cost. Moreover, a parametric study was conducted to evaluate the effect of different configurations on the global noise. The mechanism of phase synchronization method was analyzed comprehensively at the same time. Lastly, experiments were carried out in the anechoic chamber to validate the method proposed. When the separation distance between rotor shafts is greater than 2.8 R, the aerodynamic interference between the rotors can be ignored and the method can be well applied globally. Otherwise, the aerodynamic interference result in predictions that do not match the experiments at higher elevation angles, e.g. 60°. Meanwhile, as the elevation angle decreases, the prediction error decreases rapidly.

Position-Independent Constant Current or Constant Voltage Wireless Electric Vehicles Charging System Without Dual-Side Communication and DC–DC Converter

In this article, a robust wireless power transfer (WPT) system considering a wide variation in load resistance and coupling coefficient is proposed for electric vehicles charging. Here, a new implementation of the parity-time (PT)-symmetric circuit using a phase synchronization method is presented, in which a power-adjustable negative resistor is constructed only by a single-stage inverter. Moreover, based on the PT-symmetric circuit, a control strategy that does not require dual-side communication and extra dc–dc converters is developed for battery charging. Theoretical analysis shows that constant current (CC) and constant voltage (CV) outputs independent of load and position can be achieved, and the charging mode can be switched automatically. A scaled-down prototype with an 8-A charging current and a 120-V charging voltage is built to verify the feasibility of the proposed method. Experimental results demonstrate that within the transfer distance of 10–25 cm, the CC/CV outputs can be maintained during the charging process.

Improving the signal-to-noise ratio of GM-APD coherent lidar system based on phase synchronization method

Geiger mode avalanche photodiode (GM-APD) coherent lidar is a new coherent detection system for obtaining multidimensional information. The system can increase the detection sensitivity to the level of a single photon, which is the main technical direction of long-distance laser detection. The system noise of GM-APD follows a Gaussian distribution. Hence, the time-domain cumulative signal-to-noise ratio is much higher than that of the spectrum cumulative, but the jitter of the multipulse echo phase limits the system’s ability to accumulate time-domain signals. This paper proposes a phase synchronization method to solve the abovementioned problem. First, the system achieves multipulse phase consistency by introducing a clock stable and synchronized radio frequency source as well as a pulse signal externally triggered by an acousto-optic modulator. A theoretical model of the method is established. Second, the phase distribution of the system is monitored using a double-balanced detector, and the period of the system’s phase distribution is obtained, thereby verifying the abovementioned theoretical analysis. To verify the feasibility of the method, the GM-APD coherent lidar experimental system is used to detect the all-fiber system and targets. This work addresses the problem of the system being unable to perform time-domain accumulation because of the randomness of the system’s multipulse phase. This framework reduces the required time for the subsequent algorithm, yielding improved real-time performance.

Functional integration of mirror neuron system and sensorimotor cortex under virtual self-actions visual perception

Virtual reality (VR) technology, with the advantage of immersive visual experience, has been increasingly applied in the rehabilitation therapy of motor deficits. The functional integration of the mirror neuron system and the sensorimotor cortex under the visual perception of actions is one of the theoretical bases for the application of action observation in the neurorehabilitation of motor deficits. Whether the visual experience changes brought by VR technology can further promote this functional integration to be further confirmed. Using the exact low-resolution brain electromagnetic tomography (eLORETA) source localization method, we calculated and statistically tested the whole brain cortical voxel current density estimation under the Electroencephalogram (EEG) signals collected during action observation under the first-person and third-person perspectives in the VR scene for twenty healthy adults. Furthermore, the functional connectivity between the mirror neuron system and the sensorimotor cortex was analyzed using the lagged phase synchronization method. Under the first-person perspective in the VR scene, the current density changes of the core cortices of the mirror neuron system lead to a larger average event-related potential, more significant suppression in the α1 and α2 frequency bands of EEG signals, and a significant enhancement of functional connectivity between the core cortices of the mirror neuron system and the sensorimotor cortex. These findings indicate that compared with the traditional action observation, the visual reappearance of self-actions in the VR scene further stimulates the activity of the core cortices of the mirror neuron system, and promotes the functional integration of the core cortices of the mirror neuron system and the sensorimotor cortex.

Compatibility aspects of the method of phase synchronization for decoupling linear second-order differential equations

&lt;p style='text-indent:20px;'&gt;The so-called method of phase synchronization has been advocated in a number of papers as a way of decoupling a system of linear second-order differential equations by a linear transformation of coordinates and velocities. This is a rather unusual approach because velocity-dependent transformations in general do not preserve the second-order character of differential equations. Moreover, at least in the case of linear transformations, such a velocity-dependent one defines by itself a second-order system, which need not have anything to do, in principle, with the given system or its reformulation. This aspect, and the related questions of compatibility it raises, seem to have been overlooked in the existing literature. The purpose of this paper is to clarify this issue and to suggest topics for further research in conjunction with the general theory of decoupling in a differential geometric context.&lt;/p&gt;

Nonlinear interdependence of electrograms as a tool to characterize propagation patterns in atrial fibrillation

Ablation of stable sources is a promising treatment to reverse the atrial fibrillation (AF) although its underlying mechanisms are still debated. Many attempts have been made to detect stable spiral waves as a target of ablation through univariate processing of intracardiac electrogram signals (EGM). Few researchers have addressed the bivariate assessment in AF, and the existing studies are mainly based on the phase-locking value (PLV). The present work introduces a scheme to assess the AF conduction patterns through the nonlinear interdependence index. Two and three-dimensional computational simulations of cardiac conduction are used to assess the proposed method in characterizing the dynamics of fibrillatory mechanisms such as rotors. In addition, a study with real signals acquired from an AF patient is shown as an example of a possible application in humans. In the simulated episodes, the nonlinear interdependence index characterizes the core of the stable rotors as a region having low interdependence values, surrounded by a high synchronization region. In episodes where multiple reentries coexist, the nonlinear interdependence maps highlight regions harboring the core of stable and transient rotors. Additionally, we found a positive correlation between PLV and nonlinear interdependence index in both real and virtual EGM. The proposed method based on nonlinear synchronization analysis renders relevant information about the fibrillatory dynamics and it is 7.8 times faster than PLV. Hence, the nonlinear interdependence index represents a potential alternative to phase synchronization methods for characterizing AF dynamics.

하이브리드 능동전력필터의 계통 연계 위상 추종 성능 개선을 위한 위상 동기화 기법의 선정

In this paper, to improve power system connection phase tracking performance of the hybrid active power filter, compared and analyzed the robust phase synchronization method even in power sources including disturbances such as frequency and phase angle variance. Among the SOGI-based methods used to obtain a stable input voltage, the DSOGI-PLL method that tracks the phase angle of the input voltage and the DSOGI-FLL method that tracks the frequency of the system are applied to the hybrid active power filter to compare and analyzed. As a result, the phase synchronization characteristics of DSOGI-FLL method is more robust than the DSOGI-PLL method, and the current compensation characteristics is also more accurate and faster. Therefore, it is judged that the DSOGI-FLL method needs to be selected to improve the power system phase tracking performance of the hybrid active power filter.

Noise attenuation of quadrotor using phase synchronization method

The annoying noise produced by the rotors of multi-rotor aircraft can bring severe disturbance to the residents. Hence, it is essential to reduce the noise level of multi-rotor aircraft for its further development. In this paper, an attempt is made that applying the phase synchronization method to the multi-rotor aircraft for noise reduction, and the feasibility and potential are explored by the means of simulations. Firstly, the aerodynamic noise prediction model is established by combining the free wake method and the Ffowcs Williams-Hawkings equation. On this basis, the multi-island genetic optimization algorithm is employed to obtain the optimal phase angles which can minimize the noise level at the objective positions. Then, the noise attenuation simulations of the quadrotor at a single observation and a finite region are studied with different advance ratios, and the noise attenuation mechanism is analyzed. Finally, the noise reduction benefits of the square quadrotor and the diamond quadrotor are compared. The simulation results show that, for the observation plane 5 m below the vehicle, through employing the phase synchronization method, the noise level of a single observation point can be reduced by up to 30 dB, and the noise level of the forward quarter can be reduced by up to 12 dB. Therefore, it can be confirmed that the phase synchronization method shows an excellent noise attenuation potential for quadrotor.

Nonlinear Phase Synchronization Analysis of EEG Signals in Amnesic Mild Cognitive Impairment with Type 2 Diabetes Mellitus

Studying the nonlinear synchronization of electroencephalogram (EEG) in type 2 diabetic mellitus (T2DM) to find the EEG characteristics related to cognitive impairment is beneficial to the early prevention and diagnosis of mild cognitive impairment. Correlation between probabilities of recurrence (CPR) is a nonlinear phase synchronization method based on recurrence and recurrence probability, which had shown its superiority in detecting epilepsy. In this study, CPR method was used for the first time to analyze the synchronization of eye-closed resting EEG signals with T2DM. The 27 participants were divided into amnesic mild cognitive impairment (aMCI) group (17 case) and control group (10 cases with age and education matched). The CPR values in two groups were statistically analyzed by Mann-Whitney U test, and the correlation between EEG synchronization and cognitive function was studied by Spearman’s correlation. The results showed that aMCI group had lower CPR values at each electrode pair than control group, and two groups had decreased CPR values with the increase of the spatial distance of the electrode pair in inter hemispheric. The CPR values were significantly different in frontal, parietal and temporal regions in intra hemispheric between two groups. The CPR values of C3-F7, F4-C4 and FP2-T6 were significantly positively correlated with the MOCA values. This study showed that the synchronization values of EEG signals obtained by the CPR method were significantly different between aMCI and control group, and they were the EEG characteristics associated with cognitive impairment in T2DM.

Current-Decomposition-Based Digital Phase Synchronization Method for BWPT System

Phase synchronization between the primary and secondary power converters is indispensable to achieve bidirectional wireless power transfer (BWPT). For sharing the phase information without any physical contact, traditionally, some wireless communication devices or auxiliary windings are proposed, yet with the disadvantages of low reliability and high cost caused by the electromagnetic interference and extra devices. This letter proposes a digital phase synchronization method for the BWPT system. Based on the active and reactive components of the ac current flowing into/out of the secondary high-frequency converter (HFC), the voltage phase of secondary HFC can be controlled to synchronize with that of primary HFC by adjusting the reactive current to be zero. The advantages of the proposed method are the fast response and high reliability for phase synchronization. A 1-kW prototype controlled by a field-programmable gate array is built to verify the proposed method. The experimental results prove that the system can quickly switch the power transmission direction in 2 ms with a maximum efficiency of 96.48% and can operate stably when the parameters perturbation occur. This letter is accompanied by an experimental video to prove the feasibility of the proposed method.

Absolutely Consistent Fiber-Optic Phase Synchronization Based On Fixed-Phase-Reference Optical Active Compensation

An absolutely consistent fiber-optic phase synchronization scheme based on fixed-phase-reference optical active compensation is proposed. By measuring the time interval of time pulse and the phase difference of frequency signal, and then using the optical delay line to compensate the phase change in real time according to a fixed phase reference, the phase period ambiguity and the phase-lock control initial randomness are eliminated, realizing a stable and repeatable fixed phase difference between different sites. Then the phase synchronization performances of stability and absolute consistence have been demonstrated through experiments in different scenarios. The phase difference fluctuation within 10000 s is only ±0.0006 rad, showing an ultra-high stability. Under the total of 5 different operations, including the signal source restart, system restart, adding 20 m additional fiber, adding 1 km additional fiber, and adding 2 km additional fiber, the maximum inconsistency of the mean phase difference is about 1% of one full cycle. The proposed and verified absolutely consistent phase synchronization method can well maintain the coherence in transferring frequency signal, having important application prospects in radar network and other time-frequency-phase synchronization-based coherent detection.

Evaluating phase synchronization methods in fMRI: A comparison study and new approaches

In recent years there has been growing interest in measuring time-varying functional connectivity between different brain regions using resting-state functional magnetic resonance imaging (rs-fMRI) data. One way to assess the relationship between signals from different brain regions is to measure their phase synchronization (PS) across time. There are several ways to perform such analyses, and we compare methods that utilize a PS metric together with a sliding window, referred to here as windowed phase synchronization (WPS), with those that directly measure the instantaneous phase synchronization (IPS). In particular, IPS has recently gained popularity as it offers single time-point resolution of time-resolved fMRI connectivity. In this paper, we discuss the underlying assumptions required for performing PS analyses and emphasize the importance of band-pass filtering the data to obtain valid results. Further, we contrast this approach with the use of Empirical Mode Decomposition (EMD) to achieve similar goals. We review various methods for evaluating PS and introduce a new approach within the IPS framework denoted the cosine of the relative phase (CRP). We contrast methods through a series of simulations and application to rs-fMRI data. Our results indicate that CRP outperforms other tested methods and overcomes issues related to undetected temporal transitions from positive to negative associations common in IPS analysis. Further, in contrast to phase coherence, CRP unfolds the distribution of PS measures, which benefits subsequent clustering of PS matrices into recurring brain states.

Cycle-Slip Detection and Correction for Carrier Phase Synchronization in Coded Systems

In this letter, we propose a cycle slip detection and correction method for carrier phase synchronization in coded systems operating at extremely low signal-to-noise ratios. In particular, the log-likelihood ratios output from the demodulator are employed by the detector to make a cycle slip decision. Characteristics of the proposed detector in terms of probabilities of both detection and false alarm are derived. Numerical results verify the approximated analytical expressions and show the improvement in bit error rate performance by employing the proposed method in the presence of cycle slips.

Dual-Side Phase-Shift Control of Wireless Power Transfer Implemented on Primary Side Based on Driving Windings

The isolated feature between primary and secondary sides in wireless power transfer requires dual-side communication, phase synchronization, and two controllers on both sides. The phase difference between dual-side ac voltages can be changed for output regulation or bidirectional power flow. Zero crossing detection of the secondary ac voltage or current is normally conducted for frequency locking and phase synchronization. However, it is inaccurate at light-load conditions for high-power applications due to a large sensing scale and much noise; also, it can generate undesired results with discontinuous or distorted waveforms having more than two zero crossing points in one cycle. To solve these issues, this letter proposes a dual-side phase-shift implementation method using driving windings to regulate the dual-side phase difference conducted only on the primary side. By controlling the phase difference between the primary-side power and driving windings, the phase difference between the dual-side power windings can be regulated. In this way, the dual-side regulation is independent from power transfer to get rid of the issues of the conventional phase synchronization method, and bidirectional power flow can be more easily realized.

Calibration-Based Phase Coherence of Incoherent and Quasi-Coherent 160-GHz MIMO Radars

Imaging radars are usually realized fully coherently. However, the distribution of one common radio frequency signal to all transmit and receive paths requires a high degree of hardware complexity. In order to reduce the hardware effort significantly, a novel phase synchronization method for incoherent and quasi-coherent frequency-modulated continuous-wave (FMCW) imaging radars with individual signal synthesis per channel is presented. The quasi-coherent setup uses one common oscillator for all frequency synthesizers. It is shown that in the case of the quasi-coherent system, only a phase difference between the calibration and the measurement has to be corrected to achieve coherence. In comparison, an incoherent system causes additional time, frequency, and FMCW ramp slope errors due to the different behavior of the oscillators. In order to achieve phase coherence and to correct the error sources, a calibration-based method using a defined signal path as part of the radar system is proposed. The imaging radar used for verification of the theory consists of individual single-channel radar monolithic microwave integrated circuits (MMICs) at 160 GHz; each MMIC fed by an individual frequency synthesizer. As shown by measurements, it is possible to achieve phase coherence for both system approaches and to perform angle estimation.

EEG intentions recognition in dynamic complex object control task by functional brain networks and regularized discriminant analysis

Most of the tasks involved in neurological rehabilitation are generally constrained. However the complexity of experimental paradigms with constraints for acquiring electroencephalography (EEG) are relatively low. In order to improve the level of arousal in the brain, we propose an energy-constrained dynamic and complex experimental paradigm. In this novel experimental paradigm, EEG signals collected under the novel paradigm have different motor intentions. In this study, we combine the phase synchronization method and common spatial pattern (CSP) to build functional brain networks of subjects. Based on this method, we investigate the correlation of the global and local features of the functional brain networks and use regularized discriminant analysis (RDA) to recognize features. The accuracy obtained by the proposed method for EEG intention recognition can reach 93.47% (p < 0.01). The results show that the proposed method can decode EEG intention with high recognition performance during the manipulation of complex objects, which lays a foundation for the study of neurological rehabilitation.