In recent years,the rapid development of large-scale satellite constellations has challenged the mass production capabilities of satellite manufacturers.Assembly is the last and critical phase of satellite production....In recent years,the rapid development of large-scale satellite constellations has challenged the mass production capabilities of satellite manufacturers.Assembly is the last and critical phase of satellite production.Achieving satellite mass assembly is the key to realizing satellite mass production.To this end,satellite manufacturers are working to construct the satellite mass assembly shop-floor(SMAS)to enable moving assembly.However,there is still a lack of a modularized manufacturing system oriented to flexible production for SMAS,as well as disturbance detection methods and production-logistics synchronization methods to deal with various disturbances.Therefore,this paper proposes a digital twin-based production-logistics synchronization system(DT-PLSS)for SMAS.The framework of DT-PLSS is introduced first.In this framework,DT-PLSS can achieve modular construction,as well as distributed management and control.Based on the proposed framework,the construction methods of resource level digital twin(DT),workstation level DT,and shop-floor level DT in SMAS are discussed.The DT-based disturbance detection method for SMAS is presented,aiming to detect or predict di erent types of disturbances and to analyze the e ect of disturbances.Then,a DT enhanced production-logistics synchronization mechanism for SMAS is proposed.With this mechanism,the logistics distribution in the dynamic shop-floor environment and production-logistics synchronization under various disturbances can be realized.Finally,a case study in a real SMAS verifies the feasibility and e ectiveness of the proposed system and methods.This research proposes a practical framework and system which could realize disturbance detection,logistics distribution,and the production-logistics synchronization in complex SMAS scenario e ectively.展开更多
We propose a physical model of estimating noise and asymmetry brought by high isolation Bi-directional erbiumdoped fiber amplifiers(Bi-EDFAs),no spontaneous lasing even with high gain,in longdistance fiber-optic time ...We propose a physical model of estimating noise and asymmetry brought by high isolation Bi-directional erbiumdoped fiber amplifiers(Bi-EDFAs),no spontaneous lasing even with high gain,in longdistance fiber-optic time and frequency(T/F)synchronization system.It is found that the Rayleigh scattering noise can be suppressed due to the high isolation design,but the amplified spontaneous emission(ASE)noise generated by the high isolation Bi-EDFA and the bidirectional asymmetry of the transmission link caused by the high isolation Bi-EDFA will deteriorate the stability of the system.The calculated results show that under the influence of ASE noise,the frequency instability of a 1200 km system composed of 15 high isolation Bi-EDFAs is 1.773×10^(-13)/1 s.And the instability caused by asymmetry is 2.6064×10^(-16)/30000–35000 s if the total asymmetric length of the bidirectional link length is 30 m.The intensity noises originating from the laser and detector,the transfer delay fluctuations caused by the variation in ambient temperature and the jitter in laser output wavelength are also studied.The experiment composed of three high isolation Bi-EDFAs is done to confirm the theoretical analysis.In summary,the paper shows that the short-term instability of the T/F synchronization system composed of high isolation Bi-EDFAs is limited by the accumulation of ASE noise of amplifiers and the laser frequency drift,while the long-term instability is limited by the periodic variation in ambient temperature and the asymmetry of the amplifiers.The research results are useful for pointing out the direction to improve the stability of the fiber-optic T/F synchronization system.展开更多
The distributed time-keeping and synchronization system （DTSS） underwent an upgrade for EAST during the last shutdown. The upgraded DTSS, designed based on PXI bus and reconfigurable I/O devices, synchronizes all ot...The distributed time-keeping and synchronization system （DTSS） underwent an upgrade for EAST during the last shutdown. The upgraded DTSS, designed based on PXI bus and reconfigurable I/O devices, synchronizes all other sub-systems by using a reference clock and trigger. It can produce a uniform clock up to 80 MHz, provide a delayed trigger from 1 ms to 6872 s in 1 ms steps with 10 ns accuracy, and acquire the outputs of itself for self-inspection. The new DTSS was successfully applied in the 2012 spring EAST campaign, and has proven to be stable and reliable, giving an effective performance. The system structure and software development will be illustrated in detail in this paper.展开更多
Based on a generalized chaos synchronization system and a discrete Sinai map, a non-symmetric true color （RGB） digital image secure communication scheme is proposed. The scheme first changes an ordinary RGB digital ...Based on a generalized chaos synchronization system and a discrete Sinai map, a non-symmetric true color （RGB） digital image secure communication scheme is proposed. The scheme first changes an ordinary RGB digital image with 8 bits into unrecognizable disorder codes and then transforms the disorder codes into an RGB digital image with 16 bits for transmitting. A receiver uses a non-symmetric key to verify the authentication of the received data origin, and decrypts the ciphertext. The scheme can encrypt and decz：Fpt most formatted digital RGB images recognized by computers, and recover the plaintext almost without any errors. The scheme is suitable to be applied in network image communications. The analysis of the key space, sensitivity of key parameters, and correlation of encrypted images imply that this scheme has sound security.展开更多
OFDM (the orthogonal frequency division multiplexing) and its variety DMT (the discrete multitone) as delegates of the multicarrier modulation technology have given a big impact on the conventional data communication...OFDM (the orthogonal frequency division multiplexing) and its variety DMT (the discrete multitone) as delegates of the multicarrier modulation technology have given a big impact on the conventional data communication applications. Based on the theoretic a analysis of the OFDM technology, the impact of phase noise that introduced by the bit and symbol timing mechanism is discussed. Then a pilot correction and the cyclic prefix protection method are put forwarded to deal with the problem. These methods have been used in our experimental OFDM cable modem system to cope with the impulse noise and narrow band interference in the HFC (hybrid fiber and coax) upstream channel.展开更多
The intelligent substation realizes the digitization of information in the whole substation and thus time synchronization system becomes more and more important. This paper introduces time synchronization technology o...The intelligent substation realizes the digitization of information in the whole substation and thus time synchronization system becomes more and more important. This paper introduces time synchronization technology of intelligent substation and puts forward the principles for designing intelligent substation time synchronization system. According to some relay protection malfunction examples caused by time synchronization system fault, analyze the influence of time synchronization system fault to relay protection and correspondingly put forward some improving measures.展开更多
As the rapid development of Wireless Communications and the popularity of the Intelligent Terminal, data synchronization has been a social focus, meanwhile, user terminal devices are increasingly diversified, traditio...As the rapid development of Wireless Communications and the popularity of the Intelligent Terminal, data synchronization has been a social focus, meanwhile, user terminal devices are increasingly diversified, traditional synchronization technology based C/S mode has such deficiencies as insufficient amount of transmitting data and bad Real-time efficiency. It has become increasingly unable to meet the needs of future development. In this paper, we proposed and designed a new method and system by separating control with transmission to synchronize data to ensure Real-time data and improve efficiency.展开更多
White Rabbit(WR)is a multi-laboratory,multi-company collaboration for the development of an Ethernet based network ensuring sub-nanosecond synchronization and deterministic data transfer.WR technology is a combination...White Rabbit(WR)is a multi-laboratory,multi-company collaboration for the development of an Ethernet based network ensuring sub-nanosecond synchronization and deterministic data transfer.WR technology is a combination of PTP(Precision time protocol)using Synchronous Ethernet and Digital Dual-Mixer Time Difference(DDMTD)phase detection.A WR link is formed by master and slave,each WR Master and WR Slave has some constant transmission and reception delays(ΔTXM,ΔRXM,ΔTXS,ΔRXS)presented in Fig.1.Additional reception delay is also caused on both sides by aligning the recovered clock signal to the inter-symbol boundaries of the data stream.This is called the bit-slide value and is marked in Fig.1 asεM andεS.Packets transmitted in fiber are affected with propagation latencies in both directions(εMS,εSM)so the round-trip delay(delayMM)is defined as the sum of all delay factors described above。展开更多
Projective synchronization problems of a drive system and a particular response network were investigated,where the drive system is an arbitrary system with n+1 dimensions;it may be a linear or nonlinear system,and ev...Projective synchronization problems of a drive system and a particular response network were investigated,where the drive system is an arbitrary system with n+1 dimensions;it may be a linear or nonlinear system,and even a chaotic or hyperchaotic system,the response network is complex system coupled by N nodes,and every node is showed by the approximately linear part of the drive system.Only controlling any one node of the response network by designed controller can achieve the projective synchronization.Some numerical examples were employed to verify the effectiveness and correctness of the designed controller.展开更多
This study investigates the influence of seismic activities on the optical synchronization system of the European X-ray Free-Electron Laser.We analyze the controller input/output data of phase-locked loops in length-s...This study investigates the influence of seismic activities on the optical synchronization system of the European X-ray Free-Electron Laser.We analyze the controller input/output data of phase-locked loops in length-stabilized links,focusing on the response to earthquakes,ocean-generated microseism and civilization noise.By comparing the controller data with external data,we were able to identify disturbances and their effects on the control signals.Our results show that seismic events influence the stability of the phase-locked loops.Even earthquakes that are approximately 5000 km away cause remarkable fluctuations in the in-loop control signals.Ocean-generated microseism in particular has an enormous influence on the in-loop control signals due to its constant presence.The optical synchronization system is so highly sensitive that it can even identify vibrations caused by civilization,such as road traffic or major events like concerts or sport events.The phase-locked loops manage to eliminate more than 99%of the existing interference.展开更多
While laser surface texturing(LST)is a promising manufacturing technique for surface functionalization,simultaneously realizing high precision and high efficiency in the LST of complex curved surface is challenging,du...While laser surface texturing(LST)is a promising manufacturing technique for surface functionalization,simultaneously realizing high precision and high efficiency in the LST of complex curved surface is challenging,due to continuously varied geometries of laser-matter incidence.In the present work,we propose a novel manufacturing system of 7-axis on-the-fly LST for complex curved surface,based on the integrated synchronization of 5-axis linkage motion platform with 2-axis galvanometer.Specifically,the algorithm for decomposing spatial texture trajectory on curved surface into low-frequency and high-frequency parts is established,based on which the kinematic model of synchronized 7-axis system is developed to derive the motion of each axis in both 5-axis linkage motion platform and 2-axis galvanometer simultaneously.Subsequently,the synchronized 7-axis LST system is experimentally realized,including the setup of mechanical stages integrated with optical path,the configuration of numerical control unit,and the development of processing software.Finally,case study of 7-axis on-the-fly LST of freeform aluminum surface is performed,and the advantages in terms of processing efficiency and texturing accuracy over 5-axis linkage LST are demonstrated.The correlation of reduced following errors between mechanical stages with the promoted performance of curved surface texturing by the 7-axis on-the-fly LST is further analyzed.Current work provides a feasible solution for establishing the manufacturing system for high performance LST of complex curved surface.展开更多
The development of precise time synchronization technology is key to the effective application of time-frequency standards.It will significantly promote the application of precise time-frequency standards in the areas...The development of precise time synchronization technology is key to the effective application of time-frequency standards.It will significantly promote the application of precise time-frequency standards in the areas such as Positioning,Navigation,and Timing,lunar navigation,and cutting-edge fundamental physics research.This study presents an improved carrier-phase-based method for time synchronization,which was demonstrated through both laboratory and satellite-ground experiments via the China Space Station(CSS)-ground synchronization system.Initial laboratory experiments confirmed the system’s stability,achieving picosecond-level accuracy,highlighting the robustness of the method in controlled environments.Then,preliminary satellite-to-ground synchronization experiments were conducted using the CSS and ground stations,validating the effectiveness of the carrier-phase-based method.The time synchronization accuracy reached the picosecond-level,significantly surpassing traditional pseudocode techniques,which typically achieve sub-nanosecond level accuracy.Additionally,the Allan Deviation results indicated an improvement in stability by about an order of magnitude compared to traditional pseudocode-based methods.This demonstrates that the carrier-phase-based method can effectively mitigate common sources of system errors and enhance time synchronization capabilities.Therefore,this method can provide an effective technical reference for future applications requiring higher precision in time synchronization.展开更多
To analyze the influence of time synchronization error,phase synchronization error,frequency synchronization error,internal delay of the transceiver system,and range error and angle error between the unit radars on th...To analyze the influence of time synchronization error,phase synchronization error,frequency synchronization error,internal delay of the transceiver system,and range error and angle error between the unit radars on the target detection performance,firstly,a spatial detection model of distributed high-frequency surface wave radar(distributed-HFSWR)is established in this paper.In this model,a method for accurate extraction of direct wave spectrum based on curve fitting is proposed to obtain accurate system internal delay and frequency synchronization error under complex electromagnetic environment background and low signal to noise ratio(SNR),and to compensate for the shift of range and Doppler frequency caused by time-frequency synchronization error.The direct wave component is extracted from the spectrum,the range estimation error and Doppler estimation error are reduced by the method of curve fitting,and the fitting accuracy of the parameters is improved.Then,the influence of frequency synchronization error on target range and radial Doppler velocity is quantitatively analyzed.The relationship between frequency synchronization error and radial Doppler velocity shift and range shift is given.Finally,the system synchronization parameters of the trial distributed-HFSWR are obtained by the proposed spectrum extraction method based on curve fitting,the experimental data is compensated to correct the shift of the target,and finally the correct target parameter information is obtained.Simulations and experimental results demonstrate the superiority and correctness of the proposed method,theoretical derivation and detection model proposed in this paper.展开更多
The FitzHugh–Nagumo neuron circuit integrates a piezoelectric ceramic to form a piezoelectric sensing neuron,which can capture external sound signals and simulate the auditory neuron system.Two piezoelectric sensing ...The FitzHugh–Nagumo neuron circuit integrates a piezoelectric ceramic to form a piezoelectric sensing neuron,which can capture external sound signals and simulate the auditory neuron system.Two piezoelectric sensing neurons are coupled by a parallel circuit consisting of a Josephson junction and a linear resistor,and a binaural auditory system is established.Considering the non-singleness of external sound sources,the high–low frequency signal is used as the input signal to study the firing mode transition and synchronization of this system.It is found that the angular frequency of the high–low frequency signal is a key factor in determining whether the dynamic behaviors of two coupled neurons are synchronous.When they are in synchronization at a specific angular frequency,the changes in physical parameters of the input signal and the coupling strength between them will not destroy their synchronization.In addition,the firing mode of two coupled auditory neurons in synchronization is affected by the characteristic parameters of the high–low frequency signal rather than the coupling strength.The asynchronous dynamic behavior and variations in firing modes will harm the auditory system.These findings could help determine the causes of hearing loss and devise functional assistive devices for patients.展开更多
Synchronization of fractional-order chaotic systems is receiving significant attention in the literature due to its applications in a variety of fields,including cryptography,optics,and secure communications.In this p...Synchronization of fractional-order chaotic systems is receiving significant attention in the literature due to its applications in a variety of fields,including cryptography,optics,and secure communications.In this paper,a three-dimensional fractional-order chaotic Lorenz model of chemical reactions is discussed.Some basic dynamical properties,such as stability of equilibria,Lyapunov exponents,bifurcation diagrams,Poincarémap,and sensitivity to initial conditions,are studied.By adopting the Adomian decomposition algorithm(ADM),the numerical solution of the fractional-order system is obtained.It is found that the lowest derivative order in which the proposed system exhibits chaos is q=0.694 by applying ADM.The result has been validated by the existence of one positive Lyapunov exponent and by employing some phase diagrams.In addition,the richer dynamics of the system are confirmed by using powerful tools in nonlinear dynamic analysis,such as the 0-1 test and C_(0)complexity.Moreover,modified projective synchronization has been implemented based on the stability theory of fractional-order systems.This paper presents the application of the modified projective synchronization in secure communication,where the information signal can be transmitted and recovered successfully through the channel.MATLAB simulations are provided to show the validity of the constructed secure communication scheme.展开更多
The mechanical horizontal platform(MHP)system exhibits a rich chaotic behavior.The chaotic MHP system has applications in the earthquake and offshore industries.This article proposes a robust adaptive continuous contr...The mechanical horizontal platform(MHP)system exhibits a rich chaotic behavior.The chaotic MHP system has applications in the earthquake and offshore industries.This article proposes a robust adaptive continuous control(RACC)algorithm.It investigates the control and synchronization of chaos in the uncertain MHP system with time-delay in the presence of unknown state-dependent and time-dependent disturbances.The closed-loop system contains most of the nonlinear terms that enhance the complexity of the dynamical system;it improves the efficiency of the closed-loop.The proposed RACC approach(a)accomplishes faster convergence of the perturbed state variables(synchronization errors)to the desired steady-state,(b)eradicates the effect of unknown state-dependent and time-dependent disturbances,and(c)suppresses undesirable chattering in the feedback control inputs.This paper describes a detailed closed-loop stability analysis based on the Lyapunov-Krasovskii functional theory and Lyapunov stability technique.It provides parameter adaptation laws that confirm the convergence of the uncertain parameters to some constant values.The computer simulation results endorse the theoretical findings and provide a comparative performance.展开更多
Dear Editor,This letter proposes a deep synchronization control(DSC) method to synchronize grid-forming converters with power grids. The method involves constructing a novel controller for grid-forming converters base...Dear Editor,This letter proposes a deep synchronization control(DSC) method to synchronize grid-forming converters with power grids. The method involves constructing a novel controller for grid-forming converters based on the stable deep dynamics model. To enhance the performance of the controller, the dynamics model is optimized within the deep reinforcement learning(DRL) framework. Simulation results verify that the proposed method can reduce frequency deviation and improve active power responses.展开更多
This paper propose a comprehensive data-driven prediction framework based on machine learning methods to investigate the lag synchronization phenomenon in coupled chaotic systems,particularly in cases where accurate m...This paper propose a comprehensive data-driven prediction framework based on machine learning methods to investigate the lag synchronization phenomenon in coupled chaotic systems,particularly in cases where accurate mathematical models are challenging to establish or where system equations remain unknown.The Long Short-Term Memory(LSTM)neural network is trained using time series acquired from the desynchronization system states,subsequently predicting the lag synchronization transition.In the experiments,we focus on the Lorenz system with time-varying delayed coupling,studying the effects of coupling coefficients and time delays on lag synchronization,respectively.The results indicate that with appropriate training,the machine learning model can adeptly predict the lag synchronization occurrence and transition.This study not only enhances our comprehension of complex network synchronization behaviors but also underscores the potential and practical applications of machine learning in exploring nonlinear dynamic systems.展开更多
This article briefly reviews the topic of complex network synchronization,with its graph-theoretic criterion,showing that the homogeneous and symmetrical network structures are essential for optimal synchronization.Fu...This article briefly reviews the topic of complex network synchronization,with its graph-theoretic criterion,showing that the homogeneous and symmetrical network structures are essential for optimal synchronization.Furthermore,it briefly reviews the notion of higher-order network topologies and shows their promising potential in application to evaluating the optimality of network synchronizability.展开更多
Recently,large-scale trapped ion systems have been realized in experiments for quantum simulation and quantum computation.They are the simplest systems for dynamical stability and parametric resonance.In this model,th...Recently,large-scale trapped ion systems have been realized in experiments for quantum simulation and quantum computation.They are the simplest systems for dynamical stability and parametric resonance.In this model,the Mathieu equation plays the most fundamental role for us to understand the stability and instability of a single ion.In this work,we investigate the dynamics of trapped ions with the Coulomb interaction based on the Hamiltonian equation.We show that the many-body interaction will not influence the phase diagram for instability.Then,the dynamics of this model in the large damping limit will also be analytically calculated using few trapped ions.Furthermore,we find that in the presence of modulation,synchronization dynamics can be observed,showing an exchange of velocities between distant ions on the left side and on the right side of the trap.These dynamics resemble that of the exchange of velocities in Newton's cradle for the collision of balls at the same time.These dynamics are independent of their initial conditions and the number of ions.As a unique feature of the interacting Mathieu equation,we hope this behavior,which leads to a quasi-periodic solution,can be measured in current experimental systems.Finally,we have also discussed the effect of anharmonic trapping potential,showing the desynchronization during the collision process.It is hoped that the dynamics in this many-body Mathieu equation with damping may find applications in quantum simulations.This model may also find interesting applications in dynamics systems as a pure mathematical problem,which may be beyond the results in the Floquet theorem.展开更多
基金Supported by National Natural Science Foundation of China(Grant Nos.52275471,52120105008)New Cornerstone Science Foundation through the Xplorer Prize。
文摘In recent years,the rapid development of large-scale satellite constellations has challenged the mass production capabilities of satellite manufacturers.Assembly is the last and critical phase of satellite production.Achieving satellite mass assembly is the key to realizing satellite mass production.To this end,satellite manufacturers are working to construct the satellite mass assembly shop-floor(SMAS)to enable moving assembly.However,there is still a lack of a modularized manufacturing system oriented to flexible production for SMAS,as well as disturbance detection methods and production-logistics synchronization methods to deal with various disturbances.Therefore,this paper proposes a digital twin-based production-logistics synchronization system(DT-PLSS)for SMAS.The framework of DT-PLSS is introduced first.In this framework,DT-PLSS can achieve modular construction,as well as distributed management and control.Based on the proposed framework,the construction methods of resource level digital twin(DT),workstation level DT,and shop-floor level DT in SMAS are discussed.The DT-based disturbance detection method for SMAS is presented,aiming to detect or predict di erent types of disturbances and to analyze the e ect of disturbances.Then,a DT enhanced production-logistics synchronization mechanism for SMAS is proposed.With this mechanism,the logistics distribution in the dynamic shop-floor environment and production-logistics synchronization under various disturbances can be realized.Finally,a case study in a real SMAS verifies the feasibility and e ectiveness of the proposed system and methods.This research proposes a practical framework and system which could realize disturbance detection,logistics distribution,and the production-logistics synchronization in complex SMAS scenario e ectively.
基金the National Natural Science Foundation of China(Grant Nos.61701040,61771062,and 61871044)the Youth Program of the National Natural Science Foundation of China(Grant No.61901046)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant Nos.2019XD-A18and 2019PTB-004)the Youth Research and Innovation Program of BUPT(Grant No.2017RC13)。
文摘We propose a physical model of estimating noise and asymmetry brought by high isolation Bi-directional erbiumdoped fiber amplifiers(Bi-EDFAs),no spontaneous lasing even with high gain,in longdistance fiber-optic time and frequency(T/F)synchronization system.It is found that the Rayleigh scattering noise can be suppressed due to the high isolation design,but the amplified spontaneous emission(ASE)noise generated by the high isolation Bi-EDFA and the bidirectional asymmetry of the transmission link caused by the high isolation Bi-EDFA will deteriorate the stability of the system.The calculated results show that under the influence of ASE noise,the frequency instability of a 1200 km system composed of 15 high isolation Bi-EDFAs is 1.773×10^(-13)/1 s.And the instability caused by asymmetry is 2.6064×10^(-16)/30000–35000 s if the total asymmetric length of the bidirectional link length is 30 m.The intensity noises originating from the laser and detector,the transfer delay fluctuations caused by the variation in ambient temperature and the jitter in laser output wavelength are also studied.The experiment composed of three high isolation Bi-EDFAs is done to confirm the theoretical analysis.In summary,the paper shows that the short-term instability of the T/F synchronization system composed of high isolation Bi-EDFAs is limited by the accumulation of ASE noise of amplifiers and the laser frequency drift,while the long-term instability is limited by the periodic variation in ambient temperature and the asymmetry of the amplifiers.The research results are useful for pointing out the direction to improve the stability of the fiber-optic T/F synchronization system.
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2012GB105000)
文摘The distributed time-keeping and synchronization system （DTSS） underwent an upgrade for EAST during the last shutdown. The upgraded DTSS, designed based on PXI bus and reconfigurable I/O devices, synchronizes all other sub-systems by using a reference clock and trigger. It can produce a uniform clock up to 80 MHz, provide a delayed trigger from 1 ms to 6872 s in 1 ms steps with 10 ns accuracy, and acquire the outputs of itself for self-inspection. The new DTSS was successfully applied in the 2012 spring EAST campaign, and has proven to be stable and reliable, giving an effective performance. The system structure and software development will be illustrated in detail in this paper.
基金the National Natural Science Foundation of China under，the Foundation for University Key Teachers，高等学校博士学科点专项科研项目，教育部科学技术研究项目
文摘Based on a generalized chaos synchronization system and a discrete Sinai map, a non-symmetric true color （RGB） digital image secure communication scheme is proposed. The scheme first changes an ordinary RGB digital image with 8 bits into unrecognizable disorder codes and then transforms the disorder codes into an RGB digital image with 16 bits for transmitting. A receiver uses a non-symmetric key to verify the authentication of the received data origin, and decrypts the ciphertext. The scheme can encrypt and decz：Fpt most formatted digital RGB images recognized by computers, and recover the plaintext almost without any errors. The scheme is suitable to be applied in network image communications. The analysis of the key space, sensitivity of key parameters, and correlation of encrypted images imply that this scheme has sound security.
文摘OFDM (the orthogonal frequency division multiplexing) and its variety DMT (the discrete multitone) as delegates of the multicarrier modulation technology have given a big impact on the conventional data communication applications. Based on the theoretic a analysis of the OFDM technology, the impact of phase noise that introduced by the bit and symbol timing mechanism is discussed. Then a pilot correction and the cyclic prefix protection method are put forwarded to deal with the problem. These methods have been used in our experimental OFDM cable modem system to cope with the impulse noise and narrow band interference in the HFC (hybrid fiber and coax) upstream channel.
文摘The intelligent substation realizes the digitization of information in the whole substation and thus time synchronization system becomes more and more important. This paper introduces time synchronization technology of intelligent substation and puts forward the principles for designing intelligent substation time synchronization system. According to some relay protection malfunction examples caused by time synchronization system fault, analyze the influence of time synchronization system fault to relay protection and correspondingly put forward some improving measures.
文摘As the rapid development of Wireless Communications and the popularity of the Intelligent Terminal, data synchronization has been a social focus, meanwhile, user terminal devices are increasingly diversified, traditional synchronization technology based C/S mode has such deficiencies as insufficient amount of transmitting data and bad Real-time efficiency. It has become increasingly unable to meet the needs of future development. In this paper, we proposed and designed a new method and system by separating control with transmission to synchronize data to ensure Real-time data and improve efficiency.
文摘White Rabbit(WR)is a multi-laboratory,multi-company collaboration for the development of an Ethernet based network ensuring sub-nanosecond synchronization and deterministic data transfer.WR technology is a combination of PTP(Precision time protocol)using Synchronous Ethernet and Digital Dual-Mixer Time Difference(DDMTD)phase detection.A WR link is formed by master and slave,each WR Master and WR Slave has some constant transmission and reception delays(ΔTXM,ΔRXM,ΔTXS,ΔRXS)presented in Fig.1.Additional reception delay is also caused on both sides by aligning the recovered clock signal to the inter-symbol boundaries of the data stream.This is called the bit-slide value and is marked in Fig.1 asεM andεS.Packets transmitted in fiber are affected with propagation latencies in both directions(εMS,εSM)so the round-trip delay(delayMM)is defined as the sum of all delay factors described above。
基金Supported by the National Natural Science Foundation of China (11161027)。
文摘Projective synchronization problems of a drive system and a particular response network were investigated,where the drive system is an arbitrary system with n+1 dimensions;it may be a linear or nonlinear system,and even a chaotic or hyperchaotic system,the response network is complex system coupled by N nodes,and every node is showed by the approximately linear part of the drive system.Only controlling any one node of the response network by designed controller can achieve the projective synchronization.Some numerical examples were employed to verify the effectiveness and correctness of the designed controller.
基金support by DASHH(Data Science in Hamburg-Helmholtz Graduate School for the Structure of Matter)with grant No.HIDSS-0002。
文摘This study investigates the influence of seismic activities on the optical synchronization system of the European X-ray Free-Electron Laser.We analyze the controller input/output data of phase-locked loops in length-stabilized links,focusing on the response to earthquakes,ocean-generated microseism and civilization noise.By comparing the controller data with external data,we were able to identify disturbances and their effects on the control signals.Our results show that seismic events influence the stability of the phase-locked loops.Even earthquakes that are approximately 5000 km away cause remarkable fluctuations in the in-loop control signals.Ocean-generated microseism in particular has an enormous influence on the in-loop control signals due to its constant presence.The optical synchronization system is so highly sensitive that it can even identify vibrations caused by civilization,such as road traffic or major events like concerts or sport events.The phase-locked loops manage to eliminate more than 99%of the existing interference.
基金the support by the Harbin Manufacturing Science and Technology Innovation Talent Project(No.2023CXRCGD035)the Open Research Foundation of State Key Laboratory of Digital Manufacturing Equipment and Technology in Huazhong University of Science and Technology,China(No.IMETKF2023012).
文摘While laser surface texturing(LST)is a promising manufacturing technique for surface functionalization,simultaneously realizing high precision and high efficiency in the LST of complex curved surface is challenging,due to continuously varied geometries of laser-matter incidence.In the present work,we propose a novel manufacturing system of 7-axis on-the-fly LST for complex curved surface,based on the integrated synchronization of 5-axis linkage motion platform with 2-axis galvanometer.Specifically,the algorithm for decomposing spatial texture trajectory on curved surface into low-frequency and high-frequency parts is established,based on which the kinematic model of synchronized 7-axis system is developed to derive the motion of each axis in both 5-axis linkage motion platform and 2-axis galvanometer simultaneously.Subsequently,the synchronized 7-axis LST system is experimentally realized,including the setup of mechanical stages integrated with optical path,the configuration of numerical control unit,and the development of processing software.Finally,case study of 7-axis on-the-fly LST of freeform aluminum surface is performed,and the advantages in terms of processing efficiency and texturing accuracy over 5-axis linkage LST are demonstrated.The correlation of reduced following errors between mechanical stages with the promoted performance of curved surface texturing by the 7-axis on-the-fly LST is further analyzed.Current work provides a feasible solution for establishing the manufacturing system for high performance LST of complex curved surface.
基金funded by National Key Research and Development Program(NO.2023YFB3906500)Space Application System of China Manned Space Programthe National Nature Science Foundation of China(Grant NO.42030105 and NO.12273045).
文摘The development of precise time synchronization technology is key to the effective application of time-frequency standards.It will significantly promote the application of precise time-frequency standards in the areas such as Positioning,Navigation,and Timing,lunar navigation,and cutting-edge fundamental physics research.This study presents an improved carrier-phase-based method for time synchronization,which was demonstrated through both laboratory and satellite-ground experiments via the China Space Station(CSS)-ground synchronization system.Initial laboratory experiments confirmed the system’s stability,achieving picosecond-level accuracy,highlighting the robustness of the method in controlled environments.Then,preliminary satellite-to-ground synchronization experiments were conducted using the CSS and ground stations,validating the effectiveness of the carrier-phase-based method.The time synchronization accuracy reached the picosecond-level,significantly surpassing traditional pseudocode techniques,which typically achieve sub-nanosecond level accuracy.Additionally,the Allan Deviation results indicated an improvement in stability by about an order of magnitude compared to traditional pseudocode-based methods.This demonstrates that the carrier-phase-based method can effectively mitigate common sources of system errors and enhance time synchronization capabilities.Therefore,this method can provide an effective technical reference for future applications requiring higher precision in time synchronization.
基金supported by the National Natural Science Foundation of China(61701140).
文摘To analyze the influence of time synchronization error,phase synchronization error,frequency synchronization error,internal delay of the transceiver system,and range error and angle error between the unit radars on the target detection performance,firstly,a spatial detection model of distributed high-frequency surface wave radar(distributed-HFSWR)is established in this paper.In this model,a method for accurate extraction of direct wave spectrum based on curve fitting is proposed to obtain accurate system internal delay and frequency synchronization error under complex electromagnetic environment background and low signal to noise ratio(SNR),and to compensate for the shift of range and Doppler frequency caused by time-frequency synchronization error.The direct wave component is extracted from the spectrum,the range estimation error and Doppler estimation error are reduced by the method of curve fitting,and the fitting accuracy of the parameters is improved.Then,the influence of frequency synchronization error on target range and radial Doppler velocity is quantitatively analyzed.The relationship between frequency synchronization error and radial Doppler velocity shift and range shift is given.Finally,the system synchronization parameters of the trial distributed-HFSWR are obtained by the proposed spectrum extraction method based on curve fitting,the experimental data is compensated to correct the shift of the target,and finally the correct target parameter information is obtained.Simulations and experimental results demonstrate the superiority and correctness of the proposed method,theoretical derivation and detection model proposed in this paper.
基金Project supported by the National Natural Science Foundation of China(Grant No.11605014)。
文摘The FitzHugh–Nagumo neuron circuit integrates a piezoelectric ceramic to form a piezoelectric sensing neuron,which can capture external sound signals and simulate the auditory neuron system.Two piezoelectric sensing neurons are coupled by a parallel circuit consisting of a Josephson junction and a linear resistor,and a binaural auditory system is established.Considering the non-singleness of external sound sources,the high–low frequency signal is used as the input signal to study the firing mode transition and synchronization of this system.It is found that the angular frequency of the high–low frequency signal is a key factor in determining whether the dynamic behaviors of two coupled neurons are synchronous.When they are in synchronization at a specific angular frequency,the changes in physical parameters of the input signal and the coupling strength between them will not destroy their synchronization.In addition,the firing mode of two coupled auditory neurons in synchronization is affected by the characteristic parameters of the high–low frequency signal rather than the coupling strength.The asynchronous dynamic behavior and variations in firing modes will harm the auditory system.These findings could help determine the causes of hearing loss and devise functional assistive devices for patients.
文摘Synchronization of fractional-order chaotic systems is receiving significant attention in the literature due to its applications in a variety of fields,including cryptography,optics,and secure communications.In this paper,a three-dimensional fractional-order chaotic Lorenz model of chemical reactions is discussed.Some basic dynamical properties,such as stability of equilibria,Lyapunov exponents,bifurcation diagrams,Poincarémap,and sensitivity to initial conditions,are studied.By adopting the Adomian decomposition algorithm(ADM),the numerical solution of the fractional-order system is obtained.It is found that the lowest derivative order in which the proposed system exhibits chaos is q=0.694 by applying ADM.The result has been validated by the existence of one positive Lyapunov exponent and by employing some phase diagrams.In addition,the richer dynamics of the system are confirmed by using powerful tools in nonlinear dynamic analysis,such as the 0-1 test and C_(0)complexity.Moreover,modified projective synchronization has been implemented based on the stability theory of fractional-order systems.This paper presents the application of the modified projective synchronization in secure communication,where the information signal can be transmitted and recovered successfully through the channel.MATLAB simulations are provided to show the validity of the constructed secure communication scheme.
文摘The mechanical horizontal platform(MHP)system exhibits a rich chaotic behavior.The chaotic MHP system has applications in the earthquake and offshore industries.This article proposes a robust adaptive continuous control(RACC)algorithm.It investigates the control and synchronization of chaos in the uncertain MHP system with time-delay in the presence of unknown state-dependent and time-dependent disturbances.The closed-loop system contains most of the nonlinear terms that enhance the complexity of the dynamical system;it improves the efficiency of the closed-loop.The proposed RACC approach(a)accomplishes faster convergence of the perturbed state variables(synchronization errors)to the desired steady-state,(b)eradicates the effect of unknown state-dependent and time-dependent disturbances,and(c)suppresses undesirable chattering in the feedback control inputs.This paper describes a detailed closed-loop stability analysis based on the Lyapunov-Krasovskii functional theory and Lyapunov stability technique.It provides parameter adaptation laws that confirm the convergence of the uncertain parameters to some constant values.The computer simulation results endorse the theoretical findings and provide a comparative performance.
基金supported in part by the National Natural Science Foundation of China(62033005,62273270)the Natural Science Foundation of Shaanxi Province(2023JC-XJ17)
文摘Dear Editor,This letter proposes a deep synchronization control(DSC) method to synchronize grid-forming converters with power grids. The method involves constructing a novel controller for grid-forming converters based on the stable deep dynamics model. To enhance the performance of the controller, the dynamics model is optimized within the deep reinforcement learning(DRL) framework. Simulation results verify that the proposed method can reduce frequency deviation and improve active power responses.
基金supported by the National Natural Science Foundation of China(No.52174184)。
文摘This paper propose a comprehensive data-driven prediction framework based on machine learning methods to investigate the lag synchronization phenomenon in coupled chaotic systems,particularly in cases where accurate mathematical models are challenging to establish or where system equations remain unknown.The Long Short-Term Memory(LSTM)neural network is trained using time series acquired from the desynchronization system states,subsequently predicting the lag synchronization transition.In the experiments,we focus on the Lorenz system with time-varying delayed coupling,studying the effects of coupling coefficients and time delays on lag synchronization,respectively.The results indicate that with appropriate training,the machine learning model can adeptly predict the lag synchronization occurrence and transition.This study not only enhances our comprehension of complex network synchronization behaviors but also underscores the potential and practical applications of machine learning in exploring nonlinear dynamic systems.
基金Hong Kong Research Grants Council under the GRF(9043664).
文摘This article briefly reviews the topic of complex network synchronization,with its graph-theoretic criterion,showing that the homogeneous and symmetrical network structures are essential for optimal synchronization.Furthermore,it briefly reviews the notion of higher-order network topologies and shows their promising potential in application to evaluating the optimality of network synchronizability.
基金supported by the Innovation Program for Quantum Science and Technology(Grant Nos.2021ZD0301200,2021ZD0303200,and 2021ZD0301500)the Alliance of International Science Organizations(ANSO)。
文摘Recently,large-scale trapped ion systems have been realized in experiments for quantum simulation and quantum computation.They are the simplest systems for dynamical stability and parametric resonance.In this model,the Mathieu equation plays the most fundamental role for us to understand the stability and instability of a single ion.In this work,we investigate the dynamics of trapped ions with the Coulomb interaction based on the Hamiltonian equation.We show that the many-body interaction will not influence the phase diagram for instability.Then,the dynamics of this model in the large damping limit will also be analytically calculated using few trapped ions.Furthermore,we find that in the presence of modulation,synchronization dynamics can be observed,showing an exchange of velocities between distant ions on the left side and on the right side of the trap.These dynamics resemble that of the exchange of velocities in Newton's cradle for the collision of balls at the same time.These dynamics are independent of their initial conditions and the number of ions.As a unique feature of the interacting Mathieu equation,we hope this behavior,which leads to a quasi-periodic solution,can be measured in current experimental systems.Finally,we have also discussed the effect of anharmonic trapping potential,showing the desynchronization during the collision process.It is hoped that the dynamics in this many-body Mathieu equation with damping may find applications in quantum simulations.This model may also find interesting applications in dynamics systems as a pure mathematical problem,which may be beyond the results in the Floquet theorem.
