Influence of PWM Modes on Commutation Torque Ripples in Sensorless Brushless DC Motor Control System

This paper introduces four PWM modes used in the sensorless brushless DC motor control system, analyzes their different influences on the commutation torque ripple in detail, and selects the best PWM mode in four given types to reduce commutation torque ripple of Brushless OC(BLDC) motors. Simulation and experimental results show that the selection is correct and practical.

A New Method for Reducing Commutation Torque Ripples in BLDC Motors

A new compensation method and an algorithm for compensating for the commutation torque ripples of the trapezoidal EMF brushless DC motor are put forward. Simulation and experimental results show that this method is correct and practical.

Influence of Skewing Design for Reduction of Force Ripples in DSL-SynRM using 3D FEA

Double Sided Linear Synchronous Reluctance Motors(DSL-SynRM)are being increasingly used in high force density applications.The force ripples are one of the major issue in machine which is due to nonlinear nature of current in the machines.This paper focuses on the reduction of force ripples for increasing the force density of the motor.In order to reduce the force ripples,DSL-SynRM with a skewed translator is proposed.The proposed structure is designed and developed by using computational magnetic tools.This concept is effective for reduction of the force ripples and improves the force density of the machine.The proposed design has been reduced the percentage of force ripples by 21.62%,improved the force density by 10.32 N/mm³and efficiency by 0.89%.

Fabrication of large-scale ripples on fluorine-doped tin oxide films by femtosecond laser irradiation

The large-scale uniform self-organized ripples are fabricated on fluorine-doped tin oxide （FTO） coated glass by femtosecond laser. They can be smoothly linked in a horizontal line with the moving of XYZ stage by setting its velocity and the repetition rate of the laser. The ripple-to-ripple linking can also be realized through line-by-line scanning on a vertical level. The mechanism analysis shows that the seeding effect plays a key role in the linking of ripples.

Molecular dynamics study of temperature-dependent ripples in monolayer and bilayer graphene on 6H-SiC surfaces

Using classical molecular dynamics and a simulated annealing technique, we show that microscopic corrugations occur in monolayer and bilayer graphene on 6H-SiC substrates. From an analysis of the atomic configurations, two types of microscopic corrugations are identified, namely periodic ripples at room temperature and random ripples at high temperature. Two different kinds of ripple morphologies, each with a periodic structure, occur in the monolayer graphene due to the existence of a coincidence lattice between graphene and the SiC terminated surface （Si- or C-terminated surface）. The effect of temperature on microscopic ripple morphology is shown through analysing the roughness of the graphene. A temperature-dependent multiple bonding conjugation is also shown by the broad distribution of the carbon-carbon bond length and the bond angle in the rippled graphene on the SiC surface. These results provide atomic-level information about the rippled graphene layers or~ the two polar faces of the 6H-SiC substrate, which is useful not only for a better understanding of the stability and structural properties of graphene, but also for the study of the electronic properties of graphene-based devices.

A New Switching Scheme for Z-source Inverter to Minimize Ripples in the Z-source Elements

This paper presents a modification in pulse width modulation （PWM） scheme with unequal shoot-through distribution for the Z-source inverter （ZSI） which can minimize ripples in the current through the Z-source inductors as well as the voltage across the Z-source capacitors. For the same system parameters, the proposed control technique provides better voltage boost across the Z-source capacitor, DC-link, and also the AC output voltage than the traditional PWM. The ripples in the Z-network elements are found to be reduced by 75 % in the proposed modulation scheme with optimum harmonic profile in the AC output. Since the Zqnetwork requirement will be based on the ripple profile of the elements, the Z-network requirements can be greatly reduced. The effectiveness of the proposed modulation scheme has been simulated in Matlab/Simulink software and the results are validated by the experiment in the laboratory.

A Wave Modulation Model of Ripples over Long Surface Waves

A study is presented on the modulation of ripples induced by a long surface wave (LW) and a new theoretical modula-tion model is proposed. In this model, the wind surface stress modulation is related to the modulation of ripple spectrum. The model results show that in the case of LW propagating in the wind direction with the wave age parameter of LW increasing, the area with enhanced shear stress shifts from the region near the LW crest on the upwind slope to the LW trough. With a smaller wave age parameter of LW, the ripple modulation has the maximum on the upwind slope in the vicinity of LW crest, while with a larger parameter the enhancement of ripple spectrum does not occur in that region. At low winds the amplitude of ripple modulation transfer function (MTF) is larger in the gravity wave range, while at moderate or high winds it changes little in the range from short gravity waves to capillary waves.

Single Phase Induction Motor Drive with Restrained Speed and Torque Ripples Using Neural Network Predictive Controller

In industrial drives, electric motors are extensively utilized to impart motion control and induction motors are the most familiar drive at present due to its extensive performance characteristic similar with that of DC drives. Precise control of drives is the main attribute in industries to optimize the performance and to increase its production rate. In motion control, the major considerations are the torque and speed ripples. Design of controllers has become increasingly complex to such systems for better management of energy and raw materials to attain optimal performance. Meager parameter appraisal results are unsuitable, leading to unstable operation. The rapid intensification of digital computer revolutionizes to practice precise control and allows implementation of advanced control strategy to extremely multifaceted systems. To solve complex control problems, model predictive control is an authoritative scheme, which exploits an explicit model of the process to be controlled. This paper presents a predictive control strategy by a neural network predictive controller based single phase induction motor drive to minimize the speed and torque ripples. The proposed method exhibits better performance than the conventional controller and validity of the proposed method is verified by the simulation results using MATLAB software.

Numerical study of alpha particle loss with toroidal field ripple based on CFETR steady-state scenario

Effects of plasma equilibrium parameters on the alpha particle loss with the toroidal field ripple based on the CFETR steady-state scenario have been numerically investigated by the orbit-following code GYCAVA. It is found that alpha particle losses decrease and loss regions become narrower with the plasma current increasing or with the magnetic field decreasing. It is because the ripple stochastic transport and the ripple well loss of alpha particle are reduced with the safety factor decreasing. Decrease of the plasma density and temperature can reduce alpha particle losses due to enhancement of the slowing-down effect. The direction of the toroidal magnetic field can significantly affect heat loads induced by lost alpha particle. The vertical asymmetry of heat loads induced by the clockwise and counter-clockwise toroidal magnetic fields are due to the fact that the ripple distribution is asymmetric about the mid-plane, which can be explained by the typical orbits of alpha particle. The maximal heat load of alpha particle for the clockwise toroidal magnetic field is much smaller than that for the counter-clockwise one.

卡尔曼滤波器在海马场电位ripple节律分析中的应用

利用自适应自回归(adaptive autoregressive,AAR)模型和卡尔曼滤波器算法,分析小鼠海马CA1区场电位ripple高频振荡的时频特性.研究发现,与传统的基于短时傅立叶变换的实时频谱分析方法相比,利用AAR模型以及卡尔曼滤波器算法的参数化方法在对ripple高频振荡信号进行实时频谱分析时,具有更高的时域和频域分辨率.因此,基于卡尔曼滤波器得到的ripple能量变化,可更为准确、实时地反映ripple高频振荡的发生与变化过程.

Ripple与SWIFT比较分析研究

近年来,随着互联网技术的发展,Ripple1作为一种去中心化的支付清算系统,凭借其诸多优势逐步在国内外支付市场推广应用,并对以SWIFT为代表的国际主流支付系统产生影响。目前,我国的金融机构主要通过SWIFT实施跨境支付清算,但Ripple已开始在中国拓展业务。建议加强对Ripple的运行机制、商业模式等问题的研究,规范其在国内的应用。

互联网金融中的RIPPLE:原理、模式与挑战

RIPPLE是互联网金融在国际支付领域的一种新模式,是一种为在全球范围内进行转账和支付而设计的关于金融交易的互联网协议。RIPPLE表现出明显的去中心化、平台化特征,在国际支付中具有实时性、近乎零成本、覆盖范围更广等优势,因此可能对现在主流的SWIFT体系构成冲击。当然,RIPPLE协议要在未来成为主流的国际支付和清算方式,还面临着诸多困难,其中存在的安全风险也不容忽视,与之相适应的监管措施需要及早建立。

从Ripple看区块链技术对跨境支付模式的变革与创新

以Ripple为代表的区块链跨境支付能降低现有支付清算模式下高昂的时间成本和资金成本,对我国金融机构的跨境支付带来了巨大的机遇和挑战。本文在比较分析我国现有的跨境支付的主要模式和Ripple基于区块链技术的跨境支付模式基础上,指出了区块链跨境支付的优势和创新效应,并对我国的区块链跨境支付的变革与创新提出了相应的建议。

Ripple区块链技术在国际贸易支付中的应用分析

Ripple区块链技术在现代社会的发展进程中,有着非常强大的去中心化系统,而这项系统的合理运用也极大程度上改善了我国现阶段面临的比较严重的国际结算信任以及工作效率问题。文章通过对Ripple区块链技术的详细阐述,更进一步增强了对国际贸易支付的有效管理与应用。基于此,文章从我国跨境支付的市场模式、区块链的金融交易运作原理、Ripple区块链在国际贸易中面临的挑战、Ripple区块链在国际贸易支付中的应用分析等层面开展更为详细的研究与分析。

基于Ripple的区块链技术在支付领域的应用

区块链技术是通过去中心化和去信任的方式,由集体共同维护一个可靠数据库的技术,众多知名机构均认为区块链技术有望革新现有的支付体系。本文介绍了区块链技术及其特征,并结合Ripple网络技术,探讨了区块链技术在支付领域的应用及其发展所遇到的问题。

Ripple机制构架、运作模式及监管思考

Ripple网络是世界上第一个"去中心化"的开放式支付清算网络,实现了资金点对点之间的转移,颠覆了传统中心交易对手的支付清算模式。本文对Ripple的内在机制构架、市场运作模式、潜在的风险点进行了研究,并在此基础之上,提出了相关政策监管建议。

基于Ripple共识机制的分布式作战资源分配方法研究

为确保分布式联合作战指挥条件下,战场空间、电磁频谱等作战资源在各作战行动间分配的一致性,避免产生作战资源运用上的冲突矛盾,基于区块链技术架构中的Ripple共识机制提出分布式作战资源分配方法。提出区分末端节点、协商节点和审核节点等3类功能节点的作战资源分配作业架构,设计“汇总作战资源使用申请、表决作战资源分配提案、调节作战资源使用冲突、确认作战资源分配结果”等4步作战资源分配流程。案例分析表明,在任意一对协商节点的UNL重复率大于或等于41%,且确认阈值不低于各节点UNL节点数量0.8倍时,能够确保各指挥节点协商得到一致性的作战资源分配结果。

Pre-Compression Volume on Flow Ripple Reduction of a Piston Pump

Axial piston pump with pre-compression volume（PCV） has lower flow ripple in large scale of operating condition than the traditional one. However, there is lack of precise simulation model of the axial piston pump with PCV, so the parameters of PCV are difticult to be determined. A finite element simulation model for piston pump with PCV is built by considering the piston movement, the fluid characteristic（including fluid compressibility and viscosity） and the leakage flow rate. Then a test of the pump flow ripple called the secondary source method is implemented to validate the simulation model. Thirdly, by comparing results among the simulation results, test results and results from other publications at the same operating condition, the simulation model is validated and used in optimizing the axial piston pump with PCV. According to the pump flow ripples obtained by the simulation model with different PCV parameters, the flow ripple is the smallest when the PCV angle is 13~, the PCV volume is 1.3 ~ I0-4 m3 at such operating condition that the pump suction pressure is 2 MPa, the pump delivery pressure 15 MPa, the pump speed 1 000 r/min, the swash plate angle 13~. At the same time, the flow ripple can be reduced when the pump suction pressure is 2 MPa, the pump delivery pressure is 5 MPa,15 MPa, 22 MPa, pump speed is 400 r/min, 1 000 r/rain, 1 500 r/rain, the swash plate angle is ll~, 13~, 15~ and 17~, respectively. The finite element simulation model proposed provides a method for optimizing the PCV structure and guiding for designing a quieter axial piston pump.

Flow Ripple of Axial Piston Pump with Computational Fluid Dynamic Simulation Using Compressible Hydraulic Oil

The flow ripple, which is the source of noise in an axial piston pump, is widely studied today with the computational fluid dynamic（CFD） technology development. In the traditional CFD modeling, the fluid compressibility, which strongly influences the accuracy of the flow ripple simulation results, is often neglected. So a compressible sub-model was added with user defined function（UDF） in the CFD model to predict the flow ripple. At the same time, a test rig of flow ripple was built to study the validity of simulation. The flow ripple of pump was tested with different working parameters, including the rotation speed and the working pressure. The comparisons with experimental results show that the validity of the CFD model with compressible hydraulic oil is acceptable in analyzing the flow tipple characteristics. In this paper, the improved CFD model increases the accuracy of flow ripple rate to about one-magnitude order. Therefore, the compressible model of hydraulic oil is necessary in the flow ripple investigation of CFD simulation. The compressibility of hydraulic oil has significant effect on flow ripple, and the compression ripple takes about 88% of the total flow ripple of pump. Leakage ripple has the lowest proportion of about 4%, and geometrical ripple leakage ripple takes the remnant 8%. Besides, the influence of working parameters was investigated through the CFD simulations and experimental measurements. Comparison results show that the amplitude of flow ripple grows with the increasing of rotation speed and working pressure, and the flow ripple rate is independent of the rotation speed. However, flow ripple rate of piston pump grows with the increasing of working pressure, because the leakage ripple will increase with the pressure growing. The investigation on flow ripple of an axial piston pump using compressible hydraulic oil provides a more validity simulation model for the CFD analyzing and is beneficial to further understanding of the flow ripple characteristics in an axial piston pump.

Impact of Typical Steady-state Conditions and Transient Conditions on Flow Ripple and Its Test Accuracy for Axial Piston Pump

The current research about the flow ripple of axial piston pump mainly focuses on the effect of the structure of parts on the flow ripple. Therein, the structure of parts are usually designed and optimized at rated working conditions. However, the pump usually has to work in large-scale and time-variant working conditions. Therefore, the flow ripple characteristics of pump and analysis for its test accuracy with respect to variant steady-state conditions and transient conditions in a wide range of operating parameters are focused in this paper. First, a simulation model has been constructed, which takes the kinematics of oil film within friction pairs into account for higher accuracy. Afterwards, a test bed which adopts Secondary Source Method is built to verify the model. The simulation and tests results show that the angular position of the piston, corresponding to the position where the peak flow ripple is produced, varies with the different pressure. The pulsating amplitude and pulsation rate of flow ripple increase with the rise of pressure and the variation rate of pressure. For the pump working at a constant speed, the flow pulsation rate decreases dramatically with the increasing speed when the speed is less than 27.78% of the maximum speed, subsequently presents a small decrease tendency with the speed further increasing. With the rise of the variation rate of speed, the pulsating amplitude and pulsation rate of flow ripple increase. As the swash plate angle augments, the pulsating amplitude of flow ripple increases, nevertheless the flow pulsation rate decreases. In contrast with the effect of the variation of pressure, the test accuracy of flow ripple is more sensitive to the variation of speed. It makes the test accuracy above 96.20% available for the pulsating amplitude of pressure deviating within a range of ~6% from the mean pressure. However, with a variation of speed deviating within a range of ±2% from the mean speed, the attainable test accuracy of flow ripple is above 93.07%. The model constructed in this research proposes a method to determine the flow ripple characteristics of pump and its attainable test accuracy under the large-scale and time-variant working conditions. Meanwhile, a discussion about the variation of flow ripple and its obtainable test accuracy with the conditions of the pump working in wide operating ranges is given as well.