Frequency Modulation Approach Research Articles

An Energy Storage Assessment: Using Frequency Modulation Approach to Capture Optimal Coordination

To reduce the allocation of energy storage capacity in wind farms and improve economic benefits, this study is focused on the virtual synchronous generator (synchronverter) technology. A system accompanied by wind power, energy storage, a synchronous generator and load is presented in detail. A brief description of the virtual synchronous generator control strategy is given. The capacity allocation is based on different optimization goals and the optimal energy storage capacity configuration of the coordinated frequency modulation (FM) control strategy. The detail of the dual-loop control strategy is carried out by establishing the grid-connected transfer function model of the synchronverter energy storage and a theoretical model of life cycle cost is established. The optimal control strategy of coordinated FM for wind storage is implemented using MATLAB software. The simulation showed that the proposed strategy provided the energy storage capacity at high wind speed, which is configured to be 5.9% of the installed capacity of the wind turbine, marking a reduction of 26% compared with the 8% capacity required for independent support. In addition, the proposed method has improved the energy storage capacity configuration of the coordinated FM control strategy.

Switchable selective interactions in a Dicke model with a driven biased term.

In this work, we propose a method to investigate controllable qubit-resonator interactions in a Dicke model with driven biased term. The nonlinearity of the spectrum, which can be induced by qubit-resonator interactions, plays an important role in such controllable interactions. To gain insight into the mechanism of the nonlinearity, we perform a unitary transformation of the Hamiltonian. The results show that the nonlinearity of the transformed Hamiltonian depends on the qubit-resonator coupling strength. The general forms of the effective Hamiltonians are discussed in detail based on the frequency modulation approach. The dynamical evolution can be switched on and off by adjusting the modulation parameters. By utilizing such controllable interactions, we discuss the creation of Dicke states and the arbitrary superposition of Dicke states. We also consider the nonlinearity of the energy level for the limit of large qubit numbers. In the thermodynamics limit, the Kerr type nonlinearity is induced from "magnon"-resonator coupling, and the selective preparation of "magnon" Fock states can be studied under a "magnon" scenario.

Bidirectional Resonant Converter for DC Microgrid Applications

A bidirectional resonant converter is presented and verified in this paper for an electric vehicle battery charger/discharger system. The presented circuit can achieve forward and backward power operation, low switching losses on active devices, and wide output voltage operation. The circuit structure of the presented converter includes two resonant circuits on the primary and secondary sides of an isolated transformer. The frequency modulation approach is adopted to control the studied circuit. Owing to the resonant circuit characteristic, active devices for both forward (battery charge) and backward (battery discharge) power operation can be turned on at zero voltage switching. In order to implement a universal battery charger for different kinds of electric vehicle applications, the DC converter is demanded to have a wide output voltage range capability. The topology morphing between a full bridge resonant circuit and half bridge resonant circuit is selected to obtain high- and low-output voltage range operations so that the 200–500 V output voltage range is realized in the presented resonant converter. Compared to the conventional bidirectional converters, the proposed can be operated under a wide voltage range operation. In the end, a 1 kW laboratory prototype circuit is built, and experiments are provided to demonstrate the validity and performance of the presented bidirectional resonant converter.

Coordinated collision avoidance for multi‐vehicle systems based on collision time

Vehicles have irregular shapes and inter-vehicle coordination is not a trivial task. Based on the distributed-system framework, this paper studies multi-vehicle control and coordinated obstacle avoidance for multiple autonomous vehicles with irregular shapes. The goal is to reach target points without collisions. The proposed approaches are based on collision time, which is calculated using vehicles' irregular shapes. The approaches have two parts. The first part enables a number of vehicles to reach the target points. The second part enables collision avoidance, which includes inter-vehicle collisions and vehicle-to-obstacle collisions. Speed regulation approach is proposed to change the speeds, and frequency-modulation approach is proposed to update control commands at varying steps, and a combined approach is also proposed. Simulation examples are set to verify the effectiveness of the proposed approaches.

Implementation of different randomized PWM schemes using Atmega328p microcontroller for EMI reduction in boost converter

The randomized pulse width modulation techniques are used to reduce electromagnetic interference in power converters by spreading the harmonic energy. Thus, a wider spectrum with lower amplitudes is obtained. Based on the pulse width modulation signal parameters, three main randomized techniques are achieved: the random carrier frequency modulation, the random pulse width modulation and the random pulse position modulation. This paper presents a short review of the different implementation methods. Then, a detailed implementation of the three considered random techniques using Atmega328p microcontroller is detailed. Finally, an analysis of the experimental conducted electromagnetic noise taken from a boost converter is discussed. These results prove that the random carrier frequency modulation approach is completely better than other techniques in terms of electromagnetic noise reduction.

JLHS: A Joint Linear Frequency Modulation and Hyperbolic Frequency Modulation Approach for Speed Measurement

In the waveform design, the distance measurement and resolution are a pair of irreconcilable contradictions. Linear Frequency Modulation (LFM) can alleviate this contradiction. LFM is widely used in radar and sonar, however, its Doppler tolerance is not ideal. Hyperbolic Frequency Modulation (HFM) signal has a particularly strong tolerance towards Doppler frequency shift. When the unidirectionally modulated HFM signal is in distance measurement, the Doppler delay of the matched filtering output cannot be eliminated, and there is a ranging error. After matched filtering of the positive and negative frequency modulation (HFM+LFM) echo signal based on the same frequency band, the Doppler-induced delay is the same but opposite in direction, and the delay is closely related to the frequency, bandwidth, and pulse width of the transmitted signal. By using the inverse time delay difference of the positive and negative frequency modulation, the ranging error in the ranging of unidirectionally modulated LFM signal can be eliminated. In this paper, a Joint Linear frequency modulation and Hyperbolic frequency modulation approach for Speed measurement (JLHS) is proposed, which employs the same frequency band of positive and negative frequency modulation signals for speed measurement and ranging. Extensive simulation results show that the proposed approach can better estimate the speed and distance of moving targets, and it has reference value for engineering application.

A High-Voltage Generation Charge-Pump IC Using Input Voltage Modulated Regulation for Neural Implant Devices

This brief presents a high-voltage generation charge pump integrated circuit (IC) with a novel regulation scheme for neural stimulation applications. Instead of using a widely used pulse frequency modulation approach with a variable clock frequency for regulation, an input voltage modulated regulation with a low drop-out regulator at the input of the feedforward path is used to maintain the charge pump output voltage with varying load current between 10 μA to 1 mA. The proposed charge pump IC, implemented with 0.18-μm standard low-voltage CMOS process, reliably generates 12.8-V output voltage from a 2.8-V input and achieves more than 80% power efficiency at 1 mA load condition. The proposed IC occupies 0.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of core die area.

A Benchmark Dataset for SSVEP-Based Brain-Computer Interfaces.

This paper presents a benchmark steady-state visual evoked potential (SSVEP) dataset acquired with a 40-target brain- computer interface (BCI) speller. The dataset consists of 64-channel Electroencephalogram (EEG) data from 35 healthy subjects (8 experienced and 27 naïve) while they performed a cue-guided target selecting task. The virtual keyboard of the speller was composed of 40 visual flickers, which were coded using a joint frequency and phase modulation (JFPM) approach. The stimulation frequencies ranged from 8 Hz to 15.8 Hz with an interval of 0.2 Hz. The phase difference between two adjacent frequencies was . For each subject, the data included six blocks of 40 trials corresponding to all 40 flickers indicated by a visual cue in a random order. The stimulation duration in each trial was five seconds. The dataset can be used as a benchmark dataset to compare the methods for stimulus coding and target identification in SSVEP-based BCIs. Through offline simulation, the dataset can be used to design new system diagrams and evaluate their BCI performance without collecting any new data. The dataset also provides high-quality data for computational modeling of SSVEPs. The dataset is freely available fromhttp://bci.med.tsinghua.edu.cn/download.html.

Frequency modulation reveals the phasing of orbital eccentricity during Cretaceous Oceanic Anoxic Event II and the Eocene hyperthermals

Abstract Major advances in our understanding of paleoclimate change derive from a precise reconstruction of the periods, amplitudes and phases of the ‘Milankovitch cycles’ of precession, obliquity and eccentricity. While numerous quantitative approaches exist for the identification of these astronomical cycles in stratigraphic data, limitations in radioisotopic dating, and instability of the theoretical astronomical solutions beyond ∼50 Myr ago, can challenge identification of the phase relationships needed to constrain climate response and anchor floating astrochronologies. Here we demonstrate that interference patterns accompanying frequency modulation (FM) of short eccentricity provide a robust basis for identifying the phase of long eccentricity forcing in stratigraphic data. One- and two-dimensional models of sedimentary distortion of the astronomical signal are used to evaluate the veracity of the FM method, and indicate that pristine eccentricity FM can be readily distinguished in paleo-records. Apart from paleoclimatic implications, the FM approach provides a quantitative technique for testing and calibrating theoretical astronomical solutions, and for refining chronologies for the deep past. We present two case studies that use the FM approach to evaluate major carbon-cycle perturbations of the Eocene and Late Cretaceous. Interference patterns in the short-eccentricity band reveal that Eocene hyperthermals ETM2 (‘Elmo’), H2, I1 and ETM3 (X; ∼52–54 Myr ago) were associated with maxima in the 405-kyr cycle of orbital eccentricity. The same eccentricity configuration favored regional anoxic episodes in the Mediterranean during the Middle and Late Cenomanian (∼94.5–97 Myr ago). The initial phase of the global Oceanic Anoxic Event II (OAE II; ∼93.9–94.5 Myr ago) coincides with maximum and falling 405-kyr eccentricity, and the recovery phase occurs during minimum and rising 405-kyr eccentricity. On a Myr scale, the event overlaps with a node in eccentricity amplitudes. Both studies underscore the importance of seasonality in pacing major climatic perturbations during greenhouse times.

Large scale modulation of high frequency waves in periodic elastic composites

This paper addresses the modelling of large scale modulations of high frequency mechanical waves propagating in periodic elastic composite. By means of an asymptotic approach, we derive (i) the equations governing the large scale modulations, (ii) the specific features of the modulation propagation, and (iii) the domain of validity of the description. Using a multi-cell approach, the theory is implemented for 3D elastic composites with heterogeneous moduli and density. The physical parameters of the up-scaled description are determined from (mutli-)cell eigenmodes. This approach provides specific information on the physics of large scale modulations that are not directly accessible from the Bloch wave decomposition. In particular, the nature of the modulation is shown to differ significantly for simple or multiple degenerated eigenmodes. The theoretical formulation enables (i) to identify the frequency range for which wave motions are correlated over long distances, and (ii) simple calculations of high frequency wave field based on a two-step procedure separating the (multi-)cell scale and the large modulation scale. The links between the high frequency modulation approach and the usual low frequency homogenisation are discussed. Finally, an illustrating example is presented and the results and their applications are commented.

STN versus PPN‐DBS for alleviating freezing of gait: Toward a frequency modulation approach?

STN versus PPN‐DBS for alleviating freezing of gait: Toward a frequency modulation approach?

Hypersharp Resonant Capture of Neutrinos as a Laboratory Probe of the Planck Length

The 18.6 keV antineutrino (nue) line from the two-body decay of 3H in crystals can be emitted with a natural width because of motional averaging by lattice vibrations despite the very long lifetime of 3H and contrary to commonly held views of linewidths in such a case. It can be resonantly captured in 3He with geometrical cross section sigma approximately 10(-17) cm2. Using its hypersharp sensitivity DeltaE/E approximately 10(-29) and the method of "time-filtered" resonance, the basic energy width approximately 10(-24) eV expected of the 3H state can be measured to test if ultimate nuclear widths are limited by the Planck length rather than time-energy uncertainty.

Directional blood flow imaging in volumetric optical microangiography achieved by digital frequency modulation

An effective digital frequency modulation approach to achieve directional blood flow imaging within microcirculations in tissue beds in vivo for optical microangiography is presented. The method only requires the system to capture one three-dimensional data set within which the interferograms are modulated by a constant frequency modulation that gives one directional flow information. The result is that the imaging speed is doubled and the computational load is halved. The method is experimentally validated by a flow phantom and is tested for imaging of cerebral vascular blood perfusion in a live mouse with the cranium left intact.

A Method of Swell-Wave Parameter Extraction From HF Ocean Surface Radar Spectra

A new method for the extraction of swell-wave parameters from high-frequency (HF) radar spectra is presented. The method of extraction of the parameters, period, direction, and height, relies on a frequency-modulation approach that describes the hydrodynamic interaction of the swell waves with the resonant, shorter, Bragg waves. The analysis process minimizes the electromagnetic second-order interaction and a simulation model was used to validate the approach. This simplified method provides a fast means of examining swell conditions over large areas of the ocean surface. Data are acquired using a pair of coastal ocean surface radar (COSRAD) systems deployed at Tweed Heads, Qld., Australia. The radar covers a sweep (approximately 60deg) every 30 min with spatial resolution of the order of 3 km. A sample set of data from this deployment is used in a case study to show the extraction of swell direction and amplitude using these methods. The results support the use of the COSRAD HF radar for mapping swell in the near-shore zone

Frequency modulation spectroscopy in a particle-forming environment for the detection of SiH 2

Frequency modulation (FM) spectroscopy using a tunable ring-dye laser has been demonstrated on the SiH 2 reaction intermediate in a shock tube. The silylene radical is a critical species for the study of silane chemistry, the flame synthesis of materials, and the chemical vapor deposition of silicon. However, the detection of SiH 2 using laser absorption techniques is complicated by the presence of condensing particles that are present in the flow fields of interest. In the present application of FM spectroscopy, the modulation frequency is higher than normally employed, allowing one sideband to be well off the peak, despite the broad lineshape of the rQ 0,4(4) line in the A ˜ – X ˜ ( 0 , 2 , 0 ) – ( 0 , 0 , 0 ) band. A calibration method has been developed to directly obtain the absolute absorption for individual time histories, independent of normal drift in the FM signal level. In addition to increasing sensitivity, the FM approach has eliminated signal contributions from particle formation that could previously dominate the long-time profile. Due to a dramatic reduction of beam-steering effects, the temporal resolution near time zero has been increased. Silylene absorption traces were obtained from SiH 4 and Si 2H 6 mixtures highly diluted in argon and reflected-shock heated to temperatures between 1070 and 1610 K. Minimum detection sensitivities well below 0.05% absorption were demonstrated, corresponding to <0.1 ppm SiH 2. The results show that kinetic-rate and lineshape-model revisions are necessary to fit the data.

The Asymptotic Nature of the Properties of a Nonlinear Impulse System as the Frequency is Increased

It is shown that, with increase in the frequency, the properties of an impulse system with any form of modulation other than frequency modulation approach both the properties of a system with amplitude modulation the areas of instantaneous impulses in which are equal to the areas of the impulse of a real system and the properties of a continuous system obtained by replacing the impulse element with a continuous one that reflects the "useful" component of the impulses. It is shown that the Lyapunov function establishing the exponential stability of one of these systems establishes exponential stability of the other two systems and that the free processes in impulse systems get arbitrarily close to processes in a continuous system as T→0.

Classical frequency modulation and the Franck–Condon principle

A classical frequency-modulation principle is used to calculate the dipole spectrum of a two-freedom oscillator. Its two motions are assumed adiabatically separable; the frequency of motion along the fast coordinate is assumed to have a weak linear dependence on the slow coordinate. At high temperatures, the dipole spectrum of the fast motion, as found by this method, agrees quantitatively with a result based on evaluation of the Franck–Condon factors for the corresponding quantum-mechanical transition. It is suggested that the frequency-modulation approach might be especially useful in studying hydrogen-bond networks whose classical oscillations may be chaotic. Keywords: Franck–Condon factors, frequency modulation, hydrogen bonding.