Principle Of Modulation Research Articles

DC-Field Excitation Variable Flux Reluctance Starter Generator With Modular Structure for Fault-Tolerant Capability Improvement

In this article, a variable flux reluctance machine (VFRM) with dc field excitation and modular structure is proposed and it exhibits controllable flux, simplified manufacture, better fault tolerant capability, and potentially reduced material consumption. Its operational theory is illustrated by using flux modulation principles, and the working harmonics considering the modular structure are analyzed. Besides, the winding factors of modular VFRM are derived considering the flux gap width. The parameters are optimized by two-dimensional finite element method to maximize the back electromotive force (back-EMF) and the ratio of phase self-inductance to mutual inductance. Moreover, the electromagnetic performance including open circuit air-gap flux distributions, open circuit air-gap flux densities, flux linkage, back-EMF, inductance of armature windings, output characteristics, loss, power factor, and efficiency-map are compared for 12s10r and 12s14r nonmodular and modular VFRM. Additionally, the fault including short circuit and open circuit fault are analyzed. Finally, a modular 12s14r VFRM prototype is manufactured and tested to validate the theoretical and finite-element analyses.

A Dual-Modulator Magnetic-Geared Machine for Tidal-Power Generation

In this article, a new dual-modulator magnetic-geared machine (DM-MGM) is proposed for tidal-power generation with the virtue of high-torque output at low speed. First, the requirement of the DM-MGM for tidal-power generation is derived. Then, the flux-modulation principle and flux-enhancing effect of the extra modulator of the proposed DM-MGM are elaborated. After that, a finite-element analysis and multi-objective genetic algorithm (FEA-GA) combined method is used to solve a multi-objective optimization problem for the DM-MGM design. The electromagnetic performances of the optimized DM-MGM with different pole-pair combinations are quantitatively compared by FEA. The results show the effectiveness of the proposed machine, which is suitable to be applied in the tidal-power-generation scenario.

Compact Medium Voltage DC/DC Converter Using Series-Connected Power Devices

Medium voltage (MV) DC/DC converters are key equipment for interconnection between DC power lines with different voltage levels in MVDC grids. The Input-series-output-parallel (ISOP) modular MV DC/DC converter is feasible to realize MV to low voltage (LV) conversion. However, a large number of LV modules in the converter may reduce the reliability and increase the complexity. This letter proposes a phase-shifted full-bridge MV DC/DC converter using series-connected power devices as switching modules. The converter is of low cost, simple structure, compact volume, and high reliability because these switching modules require only one external isolated driver circuit and very few components to achieve voltage sharing among series-connected power devices. The operation principle of the switching modules is analyzed, and the simulation and experimental results validate the feasibility of the converter design.

Analysis of Airgap Field Modulation Principle of Flux Guides

The flux guides are adopted in a number of electric machines, such as the synchronous reluctance machine (SynRM) and the brushless doubly fed reluctance machine (BDFRM). This article further develops a novel and unified theoretical approach for the category of machines with flux guides. Specifically, the magnetomotive force (MMF) modulation operator of variable flux guides is proposed based on the general airgap field modulation theory, to describe the modulation behavior on the source magnetizing MMF distribution in detail. Both machine topologies with flux guides, namely, the SynRM and BDFRM, are addressed in detail from the perspective of airgap field modulation mechanism. It is proven that, three kinds of harmonic components with pole pairs of $p_{f}$ and $(lN_{MB}\pm p_{f})$ correspond to $p_{f}$ pole-pair source magnetizing MMF and their relative amplitudes can be characterized by three magnetic field conversion factors. The magnetic field modulation effects of flux guides and simple salient poles are compared in terms of the torque production ability. In addition, electromagnetic performances such as airgap flux density, torque density, and inductance characteristics are correlated with their initial key topological parameters by certain analytical expressions and compared fairly between the SynRM and BDFRM. The agreement among the theoretical analysis and the two-dimensional (2-D) finite element analysis together with experimental test verifies the effectiveness of the proposed analysis.

A Stator-PM Resolver With Field Modulation Principle

The stator-PM variable reluctance (VR) resolver has been proposed as a new position sensor for a wide speed range. The high-frequency (HF) signal injection is only required to measure the rotor position at low-speeds. Alternatively, at higher speeds, without requiring the HF excitation, the position measurement can be achieved by the back-EMF generated by the stator-PM. This novel resolver has a simple rotor structure and the analog signals can be efficiently decoded at high-speeds. In the first proposed stator-PM VR resolver, the prototype must have even number of rotor salient poles. However, the resolvers with odd number of rotor poles are also useful in many scenarios. To complete the design scheme of this resolver category, this article practices a solution on the basis of the theory of field modulation. The design issue and solution are illustrated and addressed in this paper. The winding function approach is applied to analyze the signals. With the low-cost materials, the proposed resolver measurement system is prototyped.

Improvement of Model Predictive Current Control Sensing Strategy for a Developed Small Flux-Switching Permanent Magnet Motor.

This paper presents an improved control system for a small flux-switching permanent magnet motor (FSPM) to enhance its performance and torque sensing. The analytical magnetic circuit design was used to determine the related motor parameters, such as the air gap flux density, permeance coefficient (Pc), torque, winding turns, pole number, width, length, magnet geometry, and the current density of FSPM. The electromagnetic analysis of this motor was performed by software (ANSYS Maxwell) to optimize the motor performance. In this study, the performance of FSPM was investigated by the uniform design experimentation (UDE). For the control system, the model predictive current control (MPCC) is currently recognized as a high-performance control strategy, due to its quick response and simple principle. This model contained the nonlinear part of the system, to improve the torque ripple of FSPM. A modified MPCC strategy was proposed to improve the distortion of the current waveform and decrease the computational burden. The new modified control architecture was mainly composed of three parts, such as the estimation of electromotive force (EMF), current prediction, and optimal vector selection/vector duration. When the reference voltage vector was obtained, the three-phase duties were easily determined by the principle of space vector modulation (SVM). The results show the different strategy methods between the newly proposed modified MPCC and traditional proportional integral (PI) controller. In the control of FSPM, a modified MPCC strategy was able to achieve a better performance response and decrease the computational burden. At a low speed of 350 rpm, the proposed modified MPCC can achieve a better dynamic response. The nonlinear problem of the startup speed was also effectively resolved. The torque sensing performance of the simulation and the experimental test value were compared. The torque sensing performance of the simulation and the actual test value were also examined. In this study, the optimization focused not only on the motor design and fabrication, but also on an improved motor control strategy and torque sensing, in order to achieve the integrity of the FSPM system.

Space-Frequency Increment Index Modulation Approach for Fifth Generation and Beyond Wireless Communication Systems

Unlike the classical modulation, for instance, quadrature amplitude modulation (QAM) and others, where bits are transmitted via symbols particularly from modulation alphabets, in index modulation (IM), extra information bits can be conveyed via the indices of a particular transmit entities during the transmission process. Transmit antenna elements are example of transmit entities in multi-antenna systems which can be used to convey extra information bits. Recently, frequency diverse array (FDA), as a new type of transmit antenna array which differs from the traditional phased-array has been proposed in the literature. In FDA, the element indices has small frequency increment across them. In this paper, space-frequency increment IM is proposed. The proposed scheme utilizes the indices of the activated transmit FDA antennas and their respective corresponding frequency increments $\Delta f$ to convey additional information bits. The proposed scheme is inspired by the principle of quadrature spatial modulation (QSM) and no additional antenna activation is required. Compared with spatial modulation (SM) and QSM, it is shown that, the proposed scheme achieved higher spectral efficiency. Further, the average bit error rate (ABER), secrecy sum rate (SSR) and system capacity are derived and evaluated. Moreover, a low-complexity decoding algorithm is examined. Finally, via numerical results, the proposed scheme shows to be better than the comparative alternatives (QSM/SM), and may offer promising properties in various contexts.

Narrative Universals, Emotion, and Ethics

Some recent writers on ethics, prominently Jonathan Haidt, have seen emotion and narrative as central to moral judgment and behavior. However, much of this work is not clear about the precise nature of emotion and narrative or the relation of the two to each other and to ethics. Research in distinct narrative traditions — a form of comparative literary study — offers a possible solution. The author has argued that a number of prototype-based story structures recur across a broad range of genetically and areally distinct traditions. These structures derive from emotion systems and general principles of emotion modulation and involve ideals that are both hedonic and ethical. We may better understand the complex relations among narrative, emotion, and morality in terms of these story universals, their sources in emotion systems, and their associated ideals, which collectively predict a range of ethical responses to any given situation. In addition, even the usual ethical orientations of emotions and prototypes may be altered through the particularization of stories. In this way, emotional response and initial emplotment bias ethical response and evaluation, but the former do not simply determine the latter. The author illustrates these points by the sometimes surprising similarities relating European, Chinese, and Indian works.

Investigation of the Power Factor of Magnetic-Field Modulated Brushless Double-Rotor Machine

The magnetic-field modulated brushless double-rotor machine (MFM-BDRM), getting rid of brush and slip ring, is a preferable selection for the power splitting device in hybrid electric vehicles. In practical application, however, the MFM-BDRM is facing the challenge of low power factor owing to its special operating principle—the magnetic field modulation principle. Although some researchers dedicate themselves to improving the power factor of MFM-BDRM, the cause of low power factor in the MFM-BDRM is still not clear. This article will investigate the power factor problem of MFM-BDRM, systematically. First, the inductance feature of MFM-BDRM based on the magnetic field modulation principle is investigated. Second, the fundamental cause of the low power factor of MFM-BDRM is analyzed. Furthermore, three feasible attempts are made and investigated to improve the power factor of MFM-BDRM. Finally, a prototype of MFM-BDRM is manufactured, and parts of the analysis are verified by experiments.

Analytical Modeling of a Double-Rotor Multiwinding Machine for Hybrid Aircraft Propulsion

In this article, a new double-rotor multiwinding machine (DRMWM) that utilizes the flux modulation principle is proposed for propulsion system of hybrid electric aircrafts (HEAs). First, the operation principle of DRMWMs and the corresponding HEA propulsion configuration are introduced, where different operation modes of two rotors and three sets of windings of DRMWMs to cope with various flight tasks of HEAs are elucidated. Then, an improved subdomain method is utilized to solve the magnetic field distribution of DRMWMs with the consideration of saturation effect of soft-magnetic material (SMM). Finally, a prototype is manufactured to verify the effectiveness of the proposed improved subdomain method in predicting the electromagnetic performances of DRMWMs. The experiment shows that the DRMWM is a good candidate to be applied in HEA with different operation modes.

Non-linear Phased Array Imaging of Flaws Using a Dual and Tri Frequency Modulation Technique

Recently, there has been high interest in the capabilities of nonlinear ultrasound techniques for damage/defect detection as these techniques have been shown to be more sensitive than linear ultrasound techniques for certain types of damage. This paper presents a nonlinear ultrasound phased array modulation method based on the principles of frequency and amplitude modulation, for the detection and imaging of material defects/damage. The proposed method requires the use of standard ultrasound phased array systems, which use multiple transmitting and receiving elements. An adjusted dual frequency method and tri-frequency is employed, which focuses on the evaluation of harmonic sidebands. A pump signal at a frequency of f2 is used to initialise a ‘breathing/ringing’ crack scenario after which a second frequency at f1 is used to further excite the crack and improve the probability that harmonic sidebands are generated. The modulation method employs a subtraction method which is used to filter out the fundamental frequencies. The technique adds benefits in ensuring that equipment based nonlinearities produced by single frequency setups are eliminated, ensuring that only defect related nonlinearities are present. A closed fatigue crack was evaluated using multiple linear and nonlinear ultrasound phased array techniques with the suggested method showing clear benefits. Furthermore, it is shown that modulation techniques with more than two driving frequencies could further improve damage detection capabilities of phased array systems.

Dual-Drive Mach-Zehnder Modulator-Based Single Side-Band Modulation Direct Detection System Without Signal-to-Signal Beating Interference

Kramers-Kronig (KK) receiver based optical single sideband (SSB) direct detection (DD) systems have been extensively investigated to cope with signal-to-signal beating interference (SSBI) for long-reach optical interconnect and 400G ZR. In this paper, we analyze the principle of dual-drive Mach-Zehnder modulator (DDMZM)-based SSB modulation due to its low cost compared with IQ modulator. We find that SSBI does not exist in back-to-back (BTB) after square-law direct detection, and electrical dispersion compensation (EDC) cannot be realized at the transmitter due to the nonlinear modulation of DDMZM. In our proposed scheme, Cartesian to Polar conversion (CPC) is used to achieve the linear modulation of DDMZM, then pre-EDC is achievable. Signal construction operation is applied to generate a target signal avoiding SSBI in DDMZM-based SSB modulation with direct detection, thus KK algorithm is not necessary both in BTB and after fiber transmission with pre-EDC, and the computation complexity of the receiver can be effectively reduced. In the simulation results of 25 GHz SSB Discrete Fourier transform spread discrete multi-tone (DFT-S DMT), the BER of our proposed scheme and conventional DDMZM scheme with optical signal-to-noise ratio (OSNR) of 26 dB are 1.2 × 10−3 and 1.7 × 10−2, respectively, after 80 km standard single mode fiber (SSMF) transmission with pre-EDC. The simulation results show that our proposed scheme is better than conventional DDMZM scheme. Although it is still inferior to the conventional IQ scheme with KK algorithm, the computation complexity of CPC is much lower than KK algorithm as it saves the numbers of adders and multipliers by the factors of 119 and 62, respectively, and reduces the memory size by a factor of 4.3.

Torque Production Mechanism of Switched Reluctance Machines With Air-Gap Field Modulation Principle

The torque production mechanism of switched reluctance machines (SRMs) is investigated from the perspective of air-gap field modulation principle. The unipolar stator current excitations can be divided into DC and AC components and they induce the air-gap magneto-motive force (MMF) respectively. Meanwhile, thanks to the salient structure in SRMs, the air-gap MMFs induced by the two sources above can be modulated to obtain the synchronized air-gap fields for torque production. It is revealed that a multitude of field harmonics contribute to the torque together. The MMF-permeance model is built and the analytical deduction of the field modulation effect is provided, with which the orders of the field harmonics contributing to the torque output can be identified. Moreover, finite element method is employed to verify the predictions on various SRM topologies. Finally, aprototype machine is fabricated and measured for validation.

Miniaturized Optical Force Sensor for Minimally Invasive Surgery With Learning-Based Nonlinear Calibration

A simple and miniaturized optical tactile sensor for integrating with robotic and manual minimally invasive surgery graspers is proposed in this study. For better miniaturization, the sensing principle of constant-bending-radius light intensity modulation was replaced with a variable-bending-radius modulation principle, and the pertinent theoretical formulation was derived. Afterward, a finite element model of the sensor was optimized using response surface optimization technique. The optimized sensor design was 14.0 mm long, 1.8 mm wide and 4 mm high. Next, the sensor was prototyped using SLA 3D printing technique. Also, the sensor was calibrated using a rate-dependent learning-based support-vector-regression algorithm. Calibration was 96% linear with a goodness-of-fit of 93% and mean absolute error of 0.085±0.096 N. Furthermore, the sensor was tested under cyclic triangular compression with a 3 sec pause between loading and unloading as well as manual grasping. Mean absolute error of 0.12±0.08 N, the minimum force of 0.14 N, and repeatability of 0.07 N showed the acceptable performance of the proposed sensor for surgical applications. Moreover, the sensor showed the capability of working under combined dynamic and static loading conditions with low hysteresis, i.e., 0.057 N/cycle.

Overview of Flux-Modulation Machines Based on Flux-Modulation Principle: Topology, Theory, and Development Prospects

With the development of electrical machines, traditional machine theory can no longer explain the operation principles of some new type machines, such as vernier machine and stator PM machine. The principle of flux modulation (FM) provides an important direction for the development of machine theory. This article overviews the development of the FM machine regarding its principle and topology. According to the studies on the FM effect of different types of electrical machines, it can be found that the FM principle is universal in electrical machines. However, the studies on the FM principle are still limited to some specific machines at present, and it leads to the fragmentation of theory. A new general air-gap FM theory is introduced, and it can be expected to be the unified theory for electrical machines. To verify the correctness of the new theory, some electrical machines, including induction machine and nonsalient pole machine, are analyzed by the general air-gap FM theory. In addition, the design and engineering application of the FM machine and theory are analyzed. To verify the inherent unity of the electrical machine, the topology evolutions of the FM machine are also discussed. Based on the new general air-gap FM theory, the innovative methods of topology can be summarized, while the development prospects of the FM machine are subsequently discussed.

Research on the key technology of turbulence suppression for atmospheric optical laser communication based on OFDM

Based on the analysis of the two main problems of atmospheric channel in free space optics (FSO), aiming at the problem of laser atmospheric channel especially the problems of frequency selective fading and multipath effect in complex turbulent environment, the suppression method is proposed based on OFDM turbulence effect, the FSO-OFDM system is built, the baseband model of this system and the signal of multi-carrier modulation and demodulation method are studied. First of all, this article systematically analyzes the mechanism of turbulence effect of atmospheric channel, and discusses the model of plane wave laser communication system under the influence of atmospheric turbulence, the space optical communication system model of Gaussian beam of a logarithmic normal turbulent channel is established under the influence of atmospheric turbulence, the probability density function of light intensity is deduced, the methods for analyzing the effects of various atmospheric turbulence effects on system performance using the signal-to-noise ratio probability density function; the OFDM multi-carrier modulation scheme of FSO-OFDM system is designed, the baseband mode model of FSO-OFDM system is constructed, and the modulation and demodulation principle of its signal is studied using this model. Finally, FSO-OFDM system is realized by using MATLAB, and the FSO communication system under the multipath interference is simulated, experiments on bit error rate characteristics under different guard intervals are performed. It is confirmed that the FSO-OFDM system has a strong ability to resist multipath interference and frequency selective fading, as well as good bit error rate (BER) performance. It can effectively solve the problem of intersymbol interference and the reliable link, and has a very broad application prospect and using value.

A new type of structure of optical fiber pressure sensor based on polarization modulation

In this study, a new type of structure of optical fiber pressure sensor (OFPS) based on polarization modulation is proposed, which selects a high-birefringence fiber (HBF) as the sensing unit to measure the pressure in the fluid medium. The PM-1550-01 fiber produced by NTK Photonics Inc. is evaluated as the sample in our subject. Firstly, the regularities of birefringence variation on the PM-1550-01 followed by the external pressure load and the ambient temperature are analyzed by the finite element method (FEM). The results show that the pressure sensitivity is 2.05 × 10−6 RIU/MPa in the pressure range of 0–100 MPa, and the temperature sensitivity is 7.27 × 10−10 RIU/°C in the temperature range of 0–100 °C. Thus, the pressure-temperature cross-sensitivity is only 0.355 kPa/°C in theory. Secondly, the expression of the output light intensity of the introduced OFPS is deduced based on the principles of polarization interference and phase modulation. Combined with simulation results, the measurement ranges of the sensor can be set and adjusted by the length of the sensing unit. Finally, the proposed OFPS is fabricated and external pressure tests within the range of 0–50 MPa are completed. The results show that the pressure sensitivity is approximately 0.145 dB/MPa in the pressure range of 0–44 MPa. There is a fine consistency between the experimental data and simulation results. In addition, the proposed OFPS has many other advantages, such as small size, simple fabrication process and large measurement range, which make it appropriate to be applied in high-pressure measurement in hostile conditions, e.g., downhole and ocean-bottom.

Simulation and Performance Study of Quadrature Amplitude Modulation and Demodulation System

Both traditional frequency modulation and phase modulation digital modulation methods have low spectral utilization, poor multipath fading resistance, slow power spectrum attenuation, and severe out-of-band radiation. Quadrature Amplitude Modulation (QAM) is a digital modulation technique that combines phase and amplitude control. It not only achieves higher spectral efficiency, but also transmits higher rate data in a defined frequency band. In this paper, the basic principle, system structure and performance parameters of QAM modulation and demodulation are studied in depth to realize simulink simulation and performance analysis of QAM modulation and demodulation system. The basic theory and implementation method of analog signal digitization are analyzed in detail to realize simimlink of differential pulse code modulation. Based on the above theory, the analog source QAM transmission system is constructed, and simulink is used for modeling and simulation and performance verification.The simulation results show that the constructed QAM digital transmission system can achieve good transmission of analog signals.

Mechanisms of the Pharmacological Modulation of Obsessive-Compulsive and Cognitive Disorders in Cats Recognized by the Method of Normalizing FFT-Convertible Functions of Electrograms of the Frontal Cortex and Hippocampus

The pharmacological modulation and analysis of psychopathological processes in animals is a research method providing a possibility to study similar processes in humans. Methods and approaches based on the principles of the pharmacological modulation of systemic behaviour and normalization of FFT-transformed functions of the brain electrograms allow identification of the quantitative parameters of intracentral relations, cognitive functions and fundamental mechanisms for evaluating the effects of neuropsychoactive drugs in the whole brain in vivo.The work was carried out on cats with stereotactically implanted electrodes in the brain. Subtherapeutic doses of ketamine, amphetamine and nakom were used to model obsessive-compulsive disorders and cognitive changes. The pharmacological modulation of the animals’ behaviour was evaluated by the effect on the frontal brain and hippocampus. The activation of γ-rhythms (from 35 to 60 Hz) was considered as an improvement in cognitive functions. Ketamine exhibited a more pronounced depressing effect on the proreal gyrus, with its activating effects being close to amphetamine across the frequency ranges of 11–15 and 32–35 Hz. Ketamine had a pronounced activating effect on the gyrus suprasilvium anterior and the hippocampus. Ketamin and nakom demonstrated similar effects in the area of the proreal gyrus, most clearly manifested at frequencies of about 9–15 and 35–36 Hz. The action of nakom was characterized by the episodes of activation in a higher frequency range of 40–55 Hz as well. In the area of the gyrus suprasilvium anterior, the effects of nakom were similar to those of ketamine; however, these substances exhibited different effects in the range of 9–11 Hz. Compared to amphetamine, nakom showed no depressing episodes over the high-frequency range of 55–65 Hz. In the hippocampus, nakom demonstrated an activating effect exceeding that of ketamine by 100–150%. It was shown that neuroimaging of the normalized functions of electrograms during the pharmacological modulation of obsessive-compulsive and cognitive disorders reflects the most striking transformations in high-frequency brain rhythms, primarily related to the γ-range.Comparison of the results of pharmacomodulation with the pharmacodynamic and pharmacokinetic parameters of drugs when modelling psychopathologies in animals helps researchers in their search for approaches to modifying animal behaviour and extrapolating them to humans.

Design and modulation principles of molybdenum carbide-based materials for green hydrogen evolution

The green production of hydrogen from electrocatalytic water splitting is an important base and promising direction for the future of the large-scale application of hydrogen energy. The key of green hydrogen evolution depends on the development of low-cost and highly active electrocatalysts. Molybdenum carbides (MoxC), as a typical of earth-abundant transition-metal material, have accumulated great attention due to their low cost, earth abundance, electrical conductivity, similar d-band state to Pt, and regulated morphology/electronic structures. In this paper, recent researches focusing on MoxC for efficient HER in a wide pH range are summarized from respects of modulation of unique morphology, electronic structure, and electrode interface step by step. Briefly, modulation of morphology influence the apparent activity of catalyst, modulation of electronic structure of active sites by heteroatom doping and designing heterointerface boost intrinsic HER kinetics, and modulation of electrode interface via hybridization of MoxC structures with carbon materials can ensure the fast electron transfer and boost the activity. Besides the above methods discussed, perspective and challenges of designing MoxC as the substitute of Pt-based electrocatalyst for practical hydrogen generation in a wide pH range are pointed out.