Principle Of Modulation Research Articles

Low-stiffness comfort shift characteristics of a permanent magnet two-speed transmission for low-speed EV

Jerk during shift in mechanical two-speed transmissions often have a serious impact on driving comfort. Within this paper, a proposed two-speed permanent magnet transmission is presented for low-speed electric vehicles, which utilizes magnetic non-contact transmission. This transmission is composed of a magnetic drive mechanism, a clutch, and a selectable one-way clutch. Then, a mathematical model is established for the magnetic-machine composite transmission based on the principles of magnetic field modulation and the concentrated parameter method. Additionally, a shift method that operates without power interruption is presented. Finally, the process of shifting is simulated for permanent magnet drive systems with varying magnetic coupling stiffness in a MATLAB/Simulink environment. The resulting torque calculations are compared with those obtained from the commercial software Maxwell. Simulation results indicate that the two-speed permanent magnet transmission does not experience power interruption during upshifting. Less jerk when shifting gears. Low magnetic coupling stiffness can reduce high-frequency vibration and enhance shift comfort. The findings from the torque calculations obtained through the proposed model align with those obtained from the commercial software Maxwell.

A review of terahertz metamaterial sensors and their applications

Terahertz (THz) waves possess unique characteristics such as high transmission, strong absorption, and low photon energy. THz metamaterial sensors, as label-free and rapid optical sensors, offer significant advantages in detection technology. These sensors enable high-sensitivity, efficient, non-destructive, and low-dose sensing due to the properties of THz waves, the sensitivity of metamaterial devices to changes in the surrounding dielectric environment and the characteristic fingerprint spectrum of biochemical molecules. THz metamaterial sensors hold great potential for applications in biomedicine, non-destructive testing, as well as the food and agricultural sectors. This paper provides a comprehensive review of various detection methods employed by THz metamaterial sensors, which consists of THz refractive index sensors, biometric fingerprint (characteristic absorption peak) sensors and biomass sensors. The study critically discusses different device structures and modulation principles used in these sensors, analyzing their respective strengths weaknesses and development trend. This review represents a broad introduction for beginners.

Management of post-traumatic ankle deformities in children.

The objective of this clinical appraisal was to assess the clinical-radiological results of ankle deformity correction secondary to physeal injury, utilizing the methods based on the age of the child, site & severity of the deformity, remaining growth potential, condition of the soft tissue envelop and integrity of neurovascular status. Fifteen subjects ≤ 16 years of age, with angular deformities of the ankle secondary to physeal injury, were included. Deformities secondary to infection and pathological fractures were excluded. Demographic data, type of injury, treatment method, and follow-up were recorded from the case files. Treatment categories included osteotomies for acute correction (> 10 years) and growth modulation (≤ 10 years). Male to female ratio was 7:8, with an average age of 11.8 ± 2.31 years (range 9-16 years). The right and left ratio was 7:8. Mean duration of follow-up was 1 year and 4 months. Gradual deformity correction was done in 2 cases utilizing the principle of growth modulation, while acute correction by osteotomy was done in 13 cases. The average pre-operative ankle deformity was 20.8 ± 3.11 degrees (Range -25 to 24 degrees). Radiological union was attained at a mean of 11 weeks (8-24). Nine patients achieved neutral ankle alignment. The mean residual varus was 2.3°, and the valgus was 4°. There was a statistically significant improvement of the AOFAS score by 17 points from a mean pre-operative score of 57 (44-84) to 74 (56-100) points at the final follow-up (p-value < 0.001). The average pre-operative shortening was 2.36 ± 0.21 cm, which was completely corrected in 9 individuals. Management of angular deformities around the ankle calls attention to correcting the resultant angular deformity and/or limb length disparity, utilizing acute or gradual correction. A successful outcome depends on early recognition and patient-specific treatment of paediatric ankle fracture patterns. Correlating the results of our study with the available literature, we feel that both acute or gradual correction for angular deformities around the ankle is a feasible solution as long as principles of deformity correction are adhered to. Techniques for salvaging and restoring the viability of injured physeal plate warrant additional research.

Anti-counterfeiting labels of photonic crystals with versatile structural colors.

Labels with structural color based on photonic crystals (PCs) have drawn significant attention due to their unique color emission, offering promising solutions for anti-counterfeiting applications. However, to meet the demands of future high-security applications, conventional structural color labels require further improvement. This study introduces a novel approach to fabricate highly encrypted anti-counterfeiting labels by combining close-packed and non-close-packed monolayers of nanoparticles (NPs) onto adhesive surfaces. The photonic crystals, arranged in specific geometric shapes, exhibit overt-covert characteristics. The hidden label is only revealed under specific external triggers, such as attaching or removing a transparent cover film. The principle of color modulation of the photonic crystal is elucidated, highlighting the role of packing density and refractive index matching. Additionally, the scalability and cost-effectiveness of the fabrication process in this study are expected to facilitate future commercialization. Various anti-counterfeiting applications, including water-responsive labels and multi-layer authentication, are demonstrated also, which enables higher security levels and versatility of this study.

Relationship between Slot-Pole Combination and Performance of Partitioned-Stator Field-Excitation Brushless Machines by Air-Gap Field Modulation Principle

Relationship between Slot-Pole Combination and Performance of Partitioned-Stator Field-Excitation Brushless Machines by Air-Gap Field Modulation Principle

Estimation of the Noise Immunity Characteristics of Telecommunication Network

The harmful impacts of various interference sources in the communication channel of data transmission systems and an increasing noise immunity in linear distortion conditions are important problems in the development of information transmission systems. To improve reliability and the data receiving accuracy, a mathematical model is developed, which allows to assessment of the survivability of telecommunication systems to interference at incoherent receiving. In this case is assumed that system impact the unintentional sources. The mathematical model considers the communication quality, spectral efficiency, coding method, and modulation principle used during the multimedia services. Presently, the development of the corporate multiservice communication networks is in conditions where the size of user and service traffic packets is rapidly increase. To ensure transmission reliability is promising of an implementation of the coherent modem. It will allow a decrease in the failures of such systems. To increase the transmission rate used coherent modem with noise-resistant characteristics. However, the communication quality in this case is decreased, due to more influence of the inter-symbol interference to the data quality receiving. The synthesis of optimal signals based on rectangular pulses with different shapes by the coherent modem for the data transmission system aims is solved by using of matching filter that has a pulse transient response. To obtain this the frequency limiter is used at the output of the channel digital demodulator. One of the ways to properly solve the problem noted above is by applying in the development of telecommunication multiservice networks the mathematical model with correction ability. This one can be developed based on the optimal signal-receiving theory.

Research on temperature compensation method for photoelectric sensors

In order to make the temperature error of fiber-optic current sensor (FGB) based on polarization modulation principle meet the requirements of engineering applications, the temperature error characteristics of FGB are analyzed theoretically, and the optimized BP neural network is used for the temperature compensation of FGB, which realizes the nonlinear temperature error correction of the sensor, and compares and analyzes the experimental results with those of other types of temperature compensation algorithms. The results show that the temperature compensation results based on the neural network algorithm are better than other compensation effects. Finally, the repeatability of the FGB was experimentally verified using its full temperature experiment, and the temperature errors of the FGB in the range of 20 ℃~ 100 ℃ were less than 0.5% after the correction of the neural network algorithm.

Electromagnetic Vibration Analysis of Transverse Flux Permanent Magnet Linear Submersible Motor for Oil Production

A transverse flux linear motor is a special type of linear motor with a high thrust force density, and it has broad application prospects in the field of linear direct-drive systems. In the process of oil production, the vibration of the linear motor poses a significant amount of harm to the system due to its special slender structure. This paper focuses on the electromagnetic vibration of a transverse flux permanent magnet linear submersible motor (TFPMLSM). Firstly, the no-load air gap flux density is calculated based on the field modulation principle. Secondly, the radial electromagnetic force (REF) of the TFPMLSM is calculated, and the finite element method (FEM) is used to analyze the time-space and spectral characteristics of the REF. Then, the influence of secondary eccentricity on the frequency spectrum of the REF is further concluded. Finally, the natural frequencies of each vibration mode are calculated using the modal superposition method and the influence of the REF on the motor vibration is obtained through magnetic-structural coupling analysis. The research results found that the motor does not cause resonance at low speeds, and the fundamental frequency of REF has the greatest impact on electromagnetic vibration.

Discrete space vector modulation and optimized switching sequence model predictive control for three-level voltage source inverters

This paper proposes a discrete space vector modulation and optimized switching sequence model predictive controller for three-level neutral-point-clamped inverters in grid-connected applications. The proposed strategy is based on cascaded model predictive control (MPC) for controlling the grid current while maintaining the capacitor voltage balanced without weighting factor. To enhance the closed-loop performance, the external MPC evaluates 19 basic and 138 virtual vectors (VV) of the proposed space vector method. The optimal control voltage is then selected using an extended deadbeat method to reduce the execution time of the proposed control algorithm. By using the discrete space vector modulation principle, the VV are synthesized based on switching sequence (SS) and are divided into negative and positive SSs considering their impact on the neutral point (NP) potential. The inner MPC evaluates both types of SSs and selects the one that keeps the capacitor voltage balanced. Various controllers are evaluated and compared against the proposed control strategy. The results show that the proposed strategy improves performance without weighting factor, while maintaining a total harmonic distortion of current to be less than 2%. Compared to the modulated MPC which provides the same fixed switching frequency, the proposed controller reduces the computational burden by over 50% while also providing better NP voltage balance accuracy.

Investigation of Cogging Torque in Permanent Magnet Homopolar Inductor Machines Based on Air‐Gap Field Modulation Principle

Cogging torque can affect the performance of permanent magnet (PM) homopolar inductor machines (HIMs). In order to find the reduction methods of the PM HIM cogging torque, it is necessary to investigate its production mechanism and analytical model. In this paper, the production mechanism of the PM HIM cogging torque is revealed from the perspective of air‐gap field modulation principle. It is found that the air‐gap permeance of PM HIMs can modulate their air‐gap magneto‐motive force (MMF) and then a large number of modulated air‐gap magnetic fields are generated. These magnetic fields with identical production condition but different rotation speeds or rotation directions can interact with each other, hence the production of the PM HIM cogging torque. By the combination of energy method and air‐gap field modulation principle, the cogging torque analytical model of PM HIMs is derived. Based on the obtained analytical model, the methods for reducing the PM HIM cogging torque are further analyzed. Finally, a 48‐slot/4‐pole (48S4P) PM HIM is designed and exampled. The air‐gap flux density of the 48S4P PM HIM is simulated by three‐dimensional (3‐D) finite element analysis (FEA). Based on the harmonic analysis for the simulated results, the correctness of the proposed cogging torque production mechanism is validated. In addition, a prototype of the 48S4P PM HIM is manufactured. The cogging torque in the prototype is obtained by the analytical model, 3‐D FEA and experiments, respectively. The simulation and measurement results verify the correctness of the cogging torque analytical model. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Recent Advances in Electromagnetic Interference Suppression

With the increasing popularity and complexity of electronic equipment, the problem of electromagnetic interference (EMI) has become increasingly prominent. Such interference can seriously affect the performance, reliability, and service life of the device and, in severe cases, may cause system failure or communication interruption. Existing EMI suppression techniques are widely used to address this issue, and this paper provides a comprehensive overview. Firstly, it introduces the impact and harm of EMI on us and then presents two forms of EMI, namely conducted EMI and radiated EMI, better to understand the sources and characteristics of these disturbances. Three different EMI filters, the advantages of soft switching compared to hard switching, the working principle of random modulation, and emerging trends in electromagnetic shielding are then analyzed and discussed. Finally, we comprehensively summarize the advantages and disadvantages of the above four methods and point out the possible limitations of each technique in practical applications. We also propose potential future research directions, which will help to overcome the shortcomings of existing technologies and promote the development of the field of EMI suppression.

Mode Predictive Direct Power Control Scheme with Fixed Operation Frequency for a Vienna Rectifier Based on Voltage‐Sensorless

Model predictive direct power control (MPDPC) is a suitable method for the highly nonlinear system of a three‐level Vienna rectifier. However, the traditional MPDPC suffers from irregular switching states, which can decrease current tracking accuracy and generate high current ripple and electromagnetic noise. Additionally, the use of sensors can increase system hardware costs and complexity. To enhance operational reliability and reduce the fault impact of AC voltage sensors, a double closed‐loop control strategy based on voltage‐sensorless MPDPC in the inner loop and sliding mode control (SMC) in the outer loop is proposed. First, the virtual flux model of the three‐phase Vienna rectifier is established in the two‐phase static coordinate system, and the second‐order low‐pass filter is used to improve the voltage observer to estimate the grid‐voltage. Meanwhile, an improved grid voltage observer based on the second‐order low‐pass filter is designed to improve the observation effect. Second, to solve the variable switching operation, current fluctuation and wide harmonic spectrum caused by the traditional MPDPC effectively, a double closed‐loop control strategy with constant switching frequency based on voltage‐sensorless MPDPC in the inner loop and SMC control in the outer loop is proposed. Based on the principle of SVPWM modulation, the modulation voltage of SVPWM is calculated directly, in order to verify the correctness of the theoretical analysis, extensive simulation and matching experimental is presented to verify the correctness of the theoretical analysis. © 2023 The Authors. IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Research on a Transverse-Dislocated Magnetic-Field Modulated Brushless Contra-Rotating Machine Adopting Different Core Material Combinations

This article proposes a transverse-dislocated magnetic-field modulated brushless contra-rotating machine (TDMFM-BCRM) with multiunit structure for the contra-rotating propulsion system. Compared with the existing contra-rotating machines, it has the advantages of equal and opposite torque at any time, no brushes and no slip rings. The improved three-dimensional (3D) magnetic-field modulation principle by considering multiunit structure of the TDMFM-BCRM is investigated. Then, due to the structural complexity of the TDMFM-BCRM, there are some challenges about its manufacturing. Therefore, the performance of the TDMFM-BCRM adopting different core material combinations including electrical steel (ES) and soft magnetic composite (SMC) material is investigated. Meanwhile, a prototype is manufactured and tested to validate the theoretical analysis, finally more manufacturing methods for the TDMFM-BCRM are comparatively studied.

FPGA-based pulsed laser with high modulation depth from Mach-Zehnder electro-optic modulator and its application

Mach-Zehnder electro-optic modulator as the essential component of high-speed modulation in the optical fiber communication and sensing system, its stability control of operating bias-point plays a key role in determining the transmission signal quality. Based on the output characteristic principle of Mach-Zehnder electro-optic modulator, researches on its bias-point drifting for causing the reduction mechanism of modulation depth and extinction ratio are analyzed. Switching its internal state machine from FPGA is proposed to automatically adjust the bias voltage in real time realizing the operating bias-point control of Mach-Zehnder electro-optic modulator, which is studied through the theoretical investigation. A pulsed laser with the temperature sensing system of fiber Bragg grating ring-down cavity based on FPGA is established experimentally to demonstrate its effectiveness. The experimental results show the modulation depth and the extinction ratio of pulsed laser are improved by 40.45% and 32.85 dB, respectively. Output characteristic curve of the sensing system is optimized, which includes the phenomenon of initial curve rise of ring-down signals and the distortion of ring-down waveform are eliminated. The good linearity, repeatability, stability and accuracy of sensing system are investigated at the continuous variation temperature from −30℃ to 30℃.

Threshold and surface potential-based sensitivity analysis of symmetrical double gate AlGaN/GaN MOS-HEMT including capacitance effects for label-free biosensing

This paper presents an analytical framework, based on the surface potential for a symmetrical double-gate AlGaN/GaN Metal oxide semiconductor high electron mobility transistor (DG-MOSHEMT) equipped with an embedded nanocavity tailored for biomedical sensing applications. The proposed model operates on the dielectric modulation principle and meticulously scrutinizes the device’s performance using critical sensing metrics such as threshold voltage shift (ΔVth), threshold voltage sensitivity (SVth), surface potential shift (ΔΨs,0), and surface potential sensitivity (SΨs,0). The model demonstrates remarkable sensitivity in detecting minute biomolecule variations, explicitly focusing on streptavidin, uricase, protein, and ChOx as the target biomolecules. Additionally, analytical equations based on surface potential are established to accurately determine gate charges (QG), gate-to-drain capacitance (CGD), and gate-to-source capacitance (CGS). The thorough investigation of biomolecule effects on gate capacitance holds paramount significance as it plays a vital and profound role in dictating device performance. Furthermore, variations in nanocavity length, AlGaN layer thickness, and oxide layer thickness are explored to understand their influence on ΔVth and SVth. The proposed model exhibits a remarkable improvement in both threshold voltage shift and sensitivity compared to the single MOS-HEMT. Notably, it demonstrates substantial enhancements of 2.06, 1.72, 1.49, and 1.5 times for the uricase, streptavidin, protein, and ChOx biomolecules, in terms of threshold voltage shift, and impressive improvements of 10.7%, 14.5%, 18.2%, and 50% for the same biomolecules, respectively, in terms of threshold voltage sensitivity, surpassing the previous findings. Uricase exhibited the most significant shift in surface potential (ΔΨs,0) among the analyzed biomolecules, with a value of 100 mV mm−1 and a sensitivity (SΨs,0) of 0.44. In contrast, ChOx showed a modest (ΔΨs,0) of 24 mV mm−1 with a relative sensitivity (SΨs,0) value of 0.108. Increasing nanocavity length and oxide layer thickness positively contribute to ΔVth and SVth. Moreover, while an increase in AlGaN layer thickness enhances ΔVth performance, its impact on SVth is minimal.

Polar electric field-modulated peroxymonosulfate selective activation for removal of organic contaminants via non-radical electron transfer process

Nonradical electron transfer process (ETP) in peroxomonosulfate (PMS) based advanced oxidation processes (AOPs) is regarded promising for selective degradation of organic contaminants in water, however, the subjective modulation strategy and the definitive mechanistic elucidation of ETP are still lacking. Herein, we proposed a heretofore unreported yet efficient ETP indution approach by construction of polar electrical field on biochar via nonmetallic elements co-doping. Physicochemical characterizations and density functional theory (DFT) calculations verified the electronegativity difference among boron, nitrogen, and sulfur elements bestowed robust local electric fields on biochar surface (BC-BNS), which effectively enhanced the adsorption complexation and charge transfer between biochar and PMS. Compared to the other single-doped or co-doped biochar, BC-BNS exhibited superior catalytic performance of PMS activation for degradation of atrazine (ATZ) (kobs=0.036 min−1), as well as various kinds of electron-rich organics. The remarkable catalytic degradation capacity was further verified in various aqueous matrices and background factors, representing the excellent selectivity. Analysis of contribution from reactive oxygen species and electrochemical testing together substantiated the role of polar electric fields in facilitating the modulation from singlet oxygen (1O2) to ETP as a prevailing mechanism. DFT calculations and apparent interactions revealed the dissociation of S-O bond was thermodynamically favored within this potent localized electric field, which further induced the cleavage of OO bond and ultimately promoted the dual electron transfer between ATZ and PMS. The superiority of BC-BNS/PMS system was further validated with the low ecotoxicity caused by enhanced dechlorination, the low energy consumption, and the long-term effectiveness. The novel modulation principle and atomic-level mechanism exploration gave suggestions for advancing ETP-dominated AOP to remove recalcitrant contaminants during water treatment and restoration.

Metamaterial-based acoustic enhanced sensing for gearbox weak fault feature diagnosis

In gear fault diagnosis of practical engineering, the gear fault signal is affected by external strong noise interference, the multipath superposition and interface loss of the internal fault excitation transmission, which leads to weak feature of incipient fault signals, making the gear fault diagnosis difficult. Inspired by the acoustic manipulation capabilities of acoustic metamaterials, this study proposes a method for weak gear fault feature diagnosis via gradient acoustic metamaterial (GAM), which utilises the acoustic rainbow capture and compression ability to reduce the difficulty of gear incipient fault diagnosis. According to the gear frequency modulation/amplitude modulation modulation principle, enhancement of fault feature frequencies can be achieved by collecting gear acoustic signals from the selected air gaps in GAM structure. In this study, the feasibility of GAM-based gear weak fault feature diagnosis is proved by experiments, which verify the multiscale feature denoising and frequency selective enhancement characteristics of GAM. The results show that the amplitude of the target signal is amplified more than eight times, the sideband component containing the fault signal is enhanced obviously, and the effect of denoising outside the target sideband is evident, making the fault feature can be easily identified from the weak fault signal after demodulation. By comparing with digital filtering in traditional signal processing, this method is more straightforward in extracting weak gear fault features. Additionally, this method adopts non-contact measurement method with micro-electroMechanical system (MEMS) microphone, which has advantages over acceleration sensors in overcoming the space limitation. All in all, the proposed method is effective and facilitates the identification of weak gear faults.

Unified small‐signal model for DC‐DC converters based on the three‐state switching cell operating in discontinuous conduction mode

SummaryUnified small‐signal modeling approaches are of paramount importance for the design of controllers and closed‐loop control systems in power electronic converters. In this sense, this work proposes the small‐signal analysis of non‐isolated dc‐dc converters employing the three‐state switching cell (3SSC) in discontinuous conduction mode (DCM). The modeling technique relies on the very same principles of the pulse width modulation (PWM) switch while not involving matrix operations, but only basic concepts related to electric circuits. Considering that the waveforms associated with the terminals of the 3SSC in DCM have a common behavior in all basic dc‐dc converters, it is possible to derive the small‐signal models for both operating regions of the 3SSC, that is, non‐overlapping mode (NOM) and overlapping mode (OM). Thus, one can effectively demonstrate that the same circuit can represent both modes, even though the coefficients that describe the models are calculated from distinct equations. The theoretical claims are validated in the frequency and time domains while comparing the model with the converter. The obtained results evidence that the unified model can accurately represent converters based on the 3SSC in DCM.

Research on the Vibration Characteristics of Pumped Storage Unit Stator Core Based on Fiber Optic Sensing

Stator core vibration (SCV) response of pumped storage units (PSU) can effectively reflect its operation status and provide reference for excitation winding inter-turn short circuit (ITSC) fault diagnosis. Considering that traditional piezoelectric acceleration sensors (PAS) are difficult to be installed on the stator core surface, this study proposes an online monitoring method based on fiber optic vibration sensing (FOVS). Firstly, this study derives the SCV response equations for the normal and ITSC states of the excitation winding, and obtains the vibration characteristic harmonics corresponding to each state. Secondly, a three-dimensional finite element simulation model of PSU with a generating capacity of 278 MVA is built, and the acceleration amplitude and characteristic frequency harmonics of the stator core are calculated to provide a reference for fiber optic vibration detection. Thirdly, this study focuses on the principle of modulation and demodulation of optical phase, builds an optical frequency-domain reflectometer (OFDR) - based FOVS system, and calibrates its sensitivity, amplitude and frequency characteristics as well as the lower detection limit. Finally, FOVS probes are installed on the surface of synchronous generator stator core to capture the vibration signals under different degrees of ITSC, and compared with the collected signals of PAS. The experimental results prove that the proposed method has obvious advantages in vibration monitoring in the low frequency band below 100 Hz.

Design and Analysis of Axial-Modular Flux-Switching Permanent Magnet Machine

This paper proposes a novel axial-modular-flux switching permanent magnet (AM-FSPM) machine, which contains two modular parts and integrated toroidal windings. After investigating the operation principle of the AM-FSPM machine, the modular PM field complementarity and integrated armature reaction field complementarity principles of two axial modular parts are revealed based on the field modulation theory. Then, a comprehensive comparison of the modulation principle between the AM-FSPM and conventional FSPM machines is conducted from perspectives of PM field, armature reaction field, cogging torque and electromagnetic torque production mechanism. It can be found that the modulation principle reveals the difference between the operation principles of two flux switching machines. In addition, the cogging torque reduction capability of AM-FSPM machine is investigated, which provides guidance on stator-slot and rotor-pole combinations in the design stage of industrial applications. Moreover, compared with conventional FSPM machines, the AM-FSPM machine exhibits high torque capability and flux weakening capability, meanwhile maintains high efficiency at high speed. Further, its characteristics are verified by the experiments.