Статті в журналах: "Ripple force"

1

Zhang, Hanshen, and Kyriakos Komvopoulos. "Scale-dependent nanomechanical behavior and anisotropic friction of nanotextured silicon surfaces." Journal of Materials Research 24, no. 10 (October 2009): 3038–43. http://dx.doi.org/10.1557/jmr.2009.0384.

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Nanoscale surface texturing of silicon was accomplished by oblique Ar+ ion beam irradiation. Atomic force microscope (AFM) imaging showed that nanotexturing produced an anisotropic morphology consisting of ordered nanometer-sized ripples. Surface force microscope (SFM) measurements showed that the nanotextured surface exhibited scale-dependent nanomechanical behavior during indentation loading/unloading and anisotropic sliding friction, significantly different from those of the original (untextured) surface. AFM and SFM results showed a strong dependence of the nanoindentation response and friction coefficient on the tip radius and sliding direction relative to the ripple orientation. The observed experimental trends are interpreted in terms of the applied normal load, real contact area, interfacial adhesion force, tip-ripple interaction scale, and ripple orientation.

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2

Louf, Jean-François, Brian Chang, Javad Eshraghi, Austin Mituniewicz, Pavlos P. Vlachos, and Sunghwan Jung. "Cavity ripple dynamics after pinch-off." Journal of Fluid Mechanics 850 (July 6, 2018): 611–23. http://dx.doi.org/10.1017/jfm.2018.459.

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During water entry, a projectile can entrain an air cavity that trails behind it. Most previous studies focus on the formation and pinch-off dynamics of the air cavity, but only a few have investigated the long-term cavity dynamics after pinch-off. In this study, we examine the ripple formation following the pinch-off of an air cavity generated by a cone, with different cone angles and impact velocities. The amplitude and wavelength of these ripples are measured, and the force on the cone is experimentally determined. It was observed that the ripple amplitude and wavelength increase linearly with the cone impact velocity, which is predicted by our acoustic model of the compressible air cavity. In addition, the measured force exhibits distinct amplitudes and wavelengths. By measuring the length of the cavity, the resulting pressure variation was averaged inside the air cavity leading to a theoretical force amplitude, which matched our observations. We noted that the force wavelength also follows the same acoustic model, which agrees very well with the wavelength of the ripples.

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3

Sun, Chuanyu, Hang Yang, Shangke Han, Hongchang Ding, Jiaqing Li, and Ning Han. "Control System Design for 16/6/8 Double-Stator Bearingless Switched Reluctance Motor." Mathematical Problems in Engineering 2021 (August 30, 2021): 1–15. http://dx.doi.org/10.1155/2021/4727917.

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The 16/6/8 double-stator bearingless switched reluctance motor (DSBSRM) is used as the object of study in this paper. To solve the problem of torque and levitation force ripples in this motor, a control system direct force control (DFC) and direct instantaneous torque control (DITC) based on the torque sharing function (TSF) are proposed. With the strong nonlinearity and approximation capability of radial basis function neural networks, the torque and levitation force observer are designed. The observed torque and levitation forces are used as feedback for the internal loop control, which is combined with the external loop control to make a double closed-loop control. In order to further improve the output torque and system robustness and suppress the torque ripple in steady-state process, the motor winding method is optimized and a set of switching angles is added on the basis of TSF. The simulation results verify the effectiveness and superiority of the proposed control method. It effectively suppresses speed ripple and reduces torque and levitation force fluctuations and rotor radial displacement jitter.

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4

Ning, Jian Rong, Cheng Yuan Wang, Jia Kuan Xia, and Li Shen. "Current Compensation Control Strategy for Reduction Normal Force Ripple of PMLSM." Advanced Materials Research 433-440 (January 2012): 7275–80. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.7275.

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The ripple normal force of permanent magnet linear synchronous motor (PMLSM) can directly deteriorate the machining accuracy of ultra-precision CNC machine tool which use linear motor direct drive. First, the normal force of PMLSM was calculated using finite element method (FEM) .then, id current compensate lookup table was established by indexing iq current, gap and position of mover .In order to reduce the ripple of normal force and keep the thrust steady, PMLSM current compensation control system was realized by injecting the id current to counteract the normal force ripples using field oriented control (FOC) method. The effectiveness of this proposed method is verified by the simulation using Matlab according to the comparison between the compensation and no compensation cases.

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5

Lee, Y. J., T. S. Liu, Mao-Hsing Lin, and Kun-Feng Huang. "Investigation of Liquid Crystal Ripple Using Ericksen-Leslie Theory for Displays Subject to Tactile Force." Mathematical Problems in Engineering 2013 (2013): 1–11. http://dx.doi.org/10.1155/2013/932492.

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Liquid crystal display panels subjected to tactile force will show ripple propagation on screens. Tactile forces change tilt angles of liquid crystal molecules and alter optical transmission so as to generate ripple on screens. Based on the Ericksen-Leslie theory, this study investigates ripple propagation by dealing with tilt angles of liquid crystal molecules. Tactile force effects are taken into account to derive the molecule equation of motion for liquid crystals. Analytical results show that viscosity, tactile force, the thickness of cell gap, and Leslie viscosity coefficient lead to tilt angle variation. Tilt angle variations of PAA liquid crystal molecules are sensitive to tactile force magnitudes, while those of 5CB and MBBA with larger viscosity are not. Analytical derivation is validated by numerical results.

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6

Gauniyal, Rakhi, Prashant Chauhan, Priyanka Rawat, and Gunjan Purohit. "Effect of self-focused rippled laser beam on the excitation of ion acoustic wave in relativistic ponderomotive regime." Laser and Particle Beams 32, no. 4 (September 8, 2014): 557–68. http://dx.doi.org/10.1017/s0263034614000512.

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AbstractThis paper presents an investigation of self-focusing of intense Gaussian rippled laser beam in collisionless plasma by including the nonlinearity associated with the relativistic mass and the ponderomotive force and its effects on the excitation of ion acoustic wave. The growth of ripple, riding on an intense Gaussian laser beam in plasma and its coupling with ion acoustic wave has also been studied. Modified coupled equations for main laser beam, growth of laser ripple in plasma, rippled laser beam, beam width, and density perturbation associated with ion acoustic wave are derived using Wentzel-Kramers-Brillouin and paraxial ray approximation. These coupled equations are solved analytically and numerically to study the laser intensity in plasma and the variation of amplitude of the ion acoustic wave for various established laser and plasma parameters. From numerical computation, it is observed that both nonlinearities significantly affected the dynamics of the growth of laser ripple in plasma, propagation of rippled laser beam as well as ion acoustic wave in plasma at high laser power flux. The growth of laser ripple increase with increase in the intensity of laser beam and due to the contribution of growth rate, intensity profile of rippled laser beam and ion acoustic wave modified accordingly.

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7

Ullah, Noman, Abdul Basit, Faisal Khan, Wasiq Ullah, Mohsin Shahzad, and Atif Zahid. "Enhancing Capabilities of Double Sided Linear Flux Switching Permanent Magnet Machines." Energies 11, no. 10 (October 16, 2018): 2781. http://dx.doi.org/10.3390/en11102781.

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Double sided linear flux switching permanent magnet machines (DSLFSPMMs) exhibit high thrust force density, high efficiency, low cost and robust double salient secondary (stator) structures. The aforementioned unique features make DSLFSPMM suitable for long stroke applications. However, distorted flux linkage waveforms and high detent forces can exaggerate thrust force ripples and reduce their applicability in many areas. In order to enhance thrust force performance, reduce thrust force ripple ratio and total harmonic distortion (THD) of no-load flux linkages, two structure-based advancements are introduced in this work, i.e., asynchronous mover slot and stator tooth displacement technique (AMSSTDT) and the addition of an active permanent magnet end slot (APMES). Furthermore, single variable geometric optimization (SVGO) is carried out by the finite element method (FEM).

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8

Bogatov, Andrei, Vitali Podgursky, Taavi Raadik, Amarnath Reddy Kamjula, Thomas Hantschel, Menelaos Tsigkourakos, and Priit Kulu. "Investigation of Morphology Changes on Nanocrystalline Diamond Film Surfaces during Reciprocating Sliding against Si₃N₄ Balls." Key Engineering Materials 604 (March 2014): 126–29. http://dx.doi.org/10.4028/www.scientific.net/kem.604.126.

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This paper investigates the morphological modifications of the nanocrystalline diamond (NCD) film surface under reciprocating sliding test conditions. The surface morphology was characterized by atomic force microscopy (AFM). We observed longitudinal grooves and transverse ripples which were formed during the sliding tests on the NCD film surface. The primary goal of the study was to understand the influence of frequency, sliding distance and load variations on the formation of ripple patterns on the wear scars surface. The morphological alteration from continuous to broken ripple shapes was observed. Our study suggests that the geometrical shape of ripples is affected by the formation of the periodic array of grooves.

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9

Wang, K., Z. Q. Zhu, and Robert Nilssen. "Using Third Harmonic for Shape Optimization of Flux Density Distribution in Linear Permanent-Magnet Machine." Applied Mechanics and Materials 416-417 (September 2013): 359–65. http://dx.doi.org/10.4028/www.scientific.net/amm.416-417.359.

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This paper presents a sinusoidal permanent magnet (PM) shaping technique with third harmonic to improve the electromagnetic thrust force in linear slotless PM machines without sacrificing the thrust force ripple. Slotless PM linear machine possesses relatively low thrust force ripple due to the absence of cogging force, compared with slotted topology. However, thrust force ripple of the machine with rectangular PM shape still exists due to nonsinusoidal airgap flux density distribution produced by PMs. Sinusoidal shaping techniques can be used to reduce the thrust force ripple but the average thrust force is reduced as well. Therefore, a simple PM shaping technique with optimal 3rd harmonic is presented to improve the output thrust force but not to increase the thrust force ripple. The sinusoidal plus 3rd harmonic shaping technique is analytically demonstrated together conventional sinusoidal shaping method and verified with finite element method. The results show that the electromagnetic performance can be significantly improved.

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10

Peng, Rui, Yue Nan Zeng, Jian Tang, and Kang Ping Chen. "Force Ripple Suppression Research for Linear Motor Servo System Based on BP Neural Network." Applied Mechanics and Materials 654 (October 2014): 191–95. http://dx.doi.org/10.4028/www.scientific.net/amm.654.191.

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For the permanent magnet synchronous linear motor’s (PMSLM) force ripple, the mathematical model of detent force is established in this paper, and presents a suppression strategy based on neural network. By the designing of BP neural network force ripple observer, theoretical analysis shows can effectively restrain the force ripple. Simulation results show the correctness and validity of the suppression strategy.

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11

Akay, Ali, and Paul Lefley. "Torque Ripple Reduction Method in a Multiphase PM Machine for No-Fault and Open-Circuit Fault-Tolerant Conditions." Energies 14, no. 9 (May 2, 2021): 2615. http://dx.doi.org/10.3390/en14092615.

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This paper presents a method that has been developed to reduce the torque ripples under healthy and open-circuit fault-tolerant (OCFT) conditions for a multiphase permanent magnet (PM) machine. For smooth torque, both the phase current and the back electromotive force (back-EMF) should be purely sinusoidal. To improve the torque in a multiphase machine, higher-order current harmonics are injected, which are related to the harmonics in the back-EMF. For this reason, generally, multiphase machines are designed with higher-order back-EMF harmonics. However, these harmonics produce ripples in the torque. In light of this, a torque ripple cancellation method has been developed that first determines an additional current component from the harmonic content of the back-EMF and then injects these additional components to cancel the torque ripple. It has been found that this new torque ripple cancellation method works for both faultless and faulty conditions in a five-phase PM machine. The method has been validated using Finite Element Analysis, and the results are presented in this paper.

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12

Ganesh Sampath, V., R. Elavarasan, N. C. Lenin, and R. Arumugam. "Design and Experimental Verification of Linear Switched Reluctance Motor with Tapered Poles." Applied Mechanics and Materials 787 (August 2015): 878–82. http://dx.doi.org/10.4028/www.scientific.net/amm.787.878.

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Linear switched reluctance motors (LSRMs) are considered for numerous applications because of its inherent properties. The force ripple and hence acoustic noise and vibration make this machine failure in compete with the existing linear induction and linear synchronous machines. In this paper a new type of stator structure is proposed and experimented. The proposed structure provides less force ripple and vibration. Parameters like force ripple and vibration are predicted using finite element analysis (FEA). Experimental results are closely correlated with the predicted results.

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13

Wang, K., Z. Q. Zhu, G. Ombach, and W. Chlebosz. "Torque ripple and magnetic forces on teeth in IPM machines." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 33, no. 5 (August 26, 2014): 1487–501. http://dx.doi.org/10.1108/compel-09-2013-0298.

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Purpose – The purpose of this paper is to investigate torque ripple and magnetic force on the teeth in interior permanent magnet (IPM) machines over a wide range of speed operation for electrical power steering (EPS) applications. Design/methodology/approach – The flux-weakening capability of IPM machines has been analysed by finite element method considering the effect of cross-coupling between d- and q-axis current. The traditional method of analysing torque ripple is based on constant torque and flux-weakening region. However, the cross-coupling need to be considered when applying this technique to flux-weakening region. Meanwhile, the torque ripple with current amplitude and angle and with different speed in the flux-weakening region is also investigated. In addition, the magnetic force on the teeth due to the separated teeth with stator yoke is also investigated during the constant torque and flux-weakening region. Findings – The torque ripple and magnetic force on teeth in IPM machine are dependent on current and current angle. Both the lowest torque ripple and magnetic force on teeth exist over the whole torque-speed region. Research limitations/implications – The purely sinusoidal currents are applied in this analysis and the effects of harmonics in the current on torque ripple and magnetic force on teeth are not considered in this application. The 12-slot/10-pole IPM machine has been employed in this analysis, but this work can be continued to investigate different slot/pole number combinations. Originality/value – This paper has analysed the torque ripple and magnetic force on the teeth in IPM machines for EPS application over a wide range of operation speed, which are the main cause of vibration and acoustic noise. The variation of torque ripple with current amplitude and angle as well as speed in the flux-weakening region is also investigated. In addition, the magnetic force on the teeth is also investigated over the whole torque-speed region.

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14

Slepička, Petr, J. Heitz, Jakub Siegel, M. Špírková, and Václav Švorčík. "F₂-Laser Angle Nanomodification of PET." Materials Science Forum 567-568 (December 2007): 257–60. http://dx.doi.org/10.4028/www.scientific.net/msf.567-568.257.

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This work is focused on laser modification of polymers with different angles of incidence. Periodic surface structures generated by linearly polarized F2 laser light (157 nm) on polyethyleneterephthalate (PET) were studied. Atomic force microscopy was used to study the topological changes induced by the laser irradiation. The laser irradiation induces the formation of periodic ripple structures, the width of and the height being angle dependent. The periodic structures were formed with the laser fluence 4.70 mJ/cm2. The laser modified PET foils were coated with a 50 nm thick gold layer by sputtering. After Au deposition on the laser PET foils with ripple structure, the roughness of surface decreases in comparison to PET with ripples without Au coating.

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15

Purohit, Gunjan, Vinod Rawat, and Priyanka Rawat. "Generation of terahertz radiation from beating of two intense cosh-Gaussian laser beams in magnetized plasma." Laser and Particle Beams 37, no. 4 (October 14, 2019): 415–27. http://dx.doi.org/10.1017/s0263034619000685.

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AbstractAn analytical and numerical study has been carried out for the generation of terahertz (THz) radiation by beating of two intense cosh-Gaussian laser beams (decentered Gaussian beams) in the rippled density magnetized plasma under the relativistic–ponderomotive regime. In this process, both laser beams exert a relativistic–ponderomotive force on plasma electrons at the beat frequency and impart them an oscillatory velocity in the presence of a static magnetic field. Due to coupling between this nonlinear oscillatory velocity with density ripple, nonlinear current is generated that excites the THz radiation at the different frequency. Higher-order paraxial-ray approximation (non-paraxial theory) has been used in this study. The effects of the decentered parameter, magnetic field, and density ripple on the THz radiation generation in ripple density magnetized plasma have been investigated. Further, the effect of beating of laser beams on the THz field amplitude and the efficiency of THz radiation have been studied. The amplitude and efficiency of the emitted radiation are found to be highly sensitive to the decentered parameter, magnetic field, and density ripple. It has been found that the amplitude and efficiency of the generated THz radiation increase significantly with increasing the values of decentered parameter, magnetic field, and density ripple.

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16

Röhrig, Christof. "FORCE RIPPLE COMPENSATION OF LINEAR SYNCHRONOUS MOTORS." Asian Journal of Control 7, no. 1 (October 22, 2008): 1–11. http://dx.doi.org/10.1111/j.1934-6093.2005.tb00222.x.

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17

Senthilnathan, A., P. Palanivel, and K. Ramash Kumar. "Mathematical Modelling and Torque Ripple Waning in BLDC Motor Using Outgoing-Phase Current Discharge Hysteresis Controlled ANFIS Controller." Mathematical Problems in Engineering 2022 (June 25, 2022): 1–21. http://dx.doi.org/10.1155/2022/3971695.

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This study focused on approaches for reducing torque ripples in Permanent Magnet Brushless Direct current motors (PMBLDC) to provide sophisticated performance and reliable machine drives for both industrial and consumer applications. Torque ripples are caused by current ripple, nonsinusoidal Back Electromotive Force (EMF), and cogging torque at the Brushless Direct Current Motor (BLDCM) output. Acoustic emissions are produced when the torque ripple creates vibrations in the mechanical system, which interacts with the motor housing and reduces the life span of the motor. The BLDC’s uses are limited due to these acoustic emissions. Proportional-Integral (PI), Fuzzy Logic Control (FLC), and Adaptive Neuro-Fuzzy Inference System (ANFIS) speed controller approaches were used to construct and analyze the mathematical model of the BLDC motor in the MATLAB environment. The Adaptive Neurofuzzy Inference System (ANFIS) speed control system has solved the shortcomings of the PI and Fuzzy Logic Control (FLC) techniques. Because of FLC interpolation and flexibility, ANFIS is one of the finest trade-offs between neural and fuzzy systems, allowing for smooth control. Model compactness, a smaller training set, and faster convergence are all benefits of the ANFIS approach over traditional feedforward NN. In this research proposal, a simple control approach based on outgoing phase current discharge hysteresis control (OGCDHC) with minimal torque ripple is presented.

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18

Wu, Hong Xing, Qing Jie Sun, Ji Gui Zheng, and Shou Ming Zhou. "Torque Ripple Reduction of Switched Reluctance Motor by Optimizing Stator Pole Type." Applied Mechanics and Materials 494-495 (February 2014): 1395–400. http://dx.doi.org/10.4028/www.scientific.net/amm.494-495.1395.

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The torque ripple is the important restriction affecting the promotion and application of switched reluctance motor, the analytic expressions to calculate switched reluctance motors tangential force and radial force are derived in this paper, based on analyzing the cause of switched reluctance motor vibration and torque ripple. By improving the stator poles structure, the torque near the commutation points is compensated, which smooth the wave of air gap magnetic field to reduce torque ripple when the stators and the rotors salient poles coincide. In this paper, three structures that puts wedge angle on both sides of the stator poles is presented, and analysis of torque ripple is made. Studies shows that the right size of wedge angle can effectively inhibit the switched reluctance motor torque fluctuations.

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19

N C, Lenin, and Arumugam R. "Design and Experimental Verification of Linear Switched Reluctance Motor with Skewed Poles." International Journal of Power Electronics and Drive Systems (IJPEDS) 6, no. 1 (March 1, 2015): 18. http://dx.doi.org/10.11591/ijpeds.v6.i1.pp18-25.

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This paper presents the realization and design of a linear switched reluctance motor (LSRM) with a new stator structure. One of the setbacks in the LSRM family is the presence of high force ripple leads to vibration and acoustic noise. The proposed structure provides a smooth force profile with reduced force ripple. Finite element analysis (FEA) is used to predict the force and other relevant parameters.A frequency spectrum analysis of the force profile using the fast Fourier transform (FFT) is presented.The FEA and experimental results of this paper prove that LSRMs are one of the strong candidates for linear propulsion drives.

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20

Yao, Yihua, Yi Chen, Qinfen Lu, Xiaoyan Huang, and Yunyue Ye. "Analysis of thrust ripple harmonics on different electric loadings in PM linear synchronous machines with skewed PMs." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 35, no. 2 (March 7, 2016): 655–69. http://dx.doi.org/10.1108/compel-12-2015-0444.

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Purpose – Permanent magnet linear synchronous machines (PMLSMs) have large thrust ripple due to the longitudinal end effect caused by the finite length of the armature compared with rotary machines. The purpose of this paper is to analyze the influence of electric loading on thrust ripple performances based on a 12 slots/14 poles (12S/14P) PMLSM. Furthermore, the method of skewed PMs to reduce thrust ripple is investigated based on multi slices 2D finite element (FE) models. Design/methodology/approach – The thrust ripple of PMLSM under open-circuit condition results from the slotting and the longitudinal end effects. Therefore, periodical model has been designed to clarify the effect of the longitudinal end effect. Under on-load condition, the thrust ripple increases and exhibits an effective component of thrust force. To analyze the thrust ripple under on-load condition, frozen permeability (FP) technique is employed. In addition, the method of skewed PMs is analyzed in this paper to obtain more smooth thrust force performance. The effectiveness of skewing accounting for skew angles, step skew numbers and slot/pole number combinations was highlighted. Findings – The longitudinal end effect dominates the thrust ripple of PMLSM in both cases, i.e., open-circuit and on-load conditions. Under on-load condition, the second harmonic component of thrust ripple related to flux linkage harmonics increases significantly. Moreover, the effectiveness of skewed PMs is largely reduced with the increase of magnetic saturation. At last, a proper skew angle and step skew number are obtained for the conventional PMLSM with fractional-slot winding. Originality/value – By 60 electrical degrees and two or three step skewed PMs, the thrust ripple can be decreased to a tolerable limite for conventional PMLSM. The thrust ripple harmonics contributed by longitudinal end effect and flux linkage harmonics are analyzed, respectively, which is beneficial to exploring other techniques such as adding end auxiliary teeth to obtain lower thrust force pulsation.

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21

Tzouganakis, Panteleimon, Vasilios Gakos, Christos Kalligeros, Christos Papalexis, Antonios Tsolakis, and Vasilios Spitas. "Torque ripple investigation in coaxial magnetic gears." MATEC Web of Conferences 366 (2022): 01004. http://dx.doi.org/10.1051/matecconf/202236601004.

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Magnetic gears offer significant advantages such as low noise and vibration level, lower maintenance and higher reliability compared to mechanical gears and are suitable for many applications in the industry. The coaxial magnetic gear has been extensively discussed in the literature, since it achieves higher torque densities amongst other magnetic gear configurations. The magnetic field is generated by permanent magnets mounted on the two rotors and a modulator between them. The modulator consists of ferromagnetic segments that are typically encased in a resin in order to increase its stiffness without compromising the generated magnetic field. However, due to the development of radial forces, oscillations of the ferromagnetic segments occur, which lead to torque ripples that affect the operation of the coaxial magnetic gear drive in applications where accuracy is required. This work introduces a computationally lightweight analytical 2D model in order to determine the applied radial force on the ferromagnetic segments at each angle of rotation of the two rotors and henceforth calculate the displacement of these segments using FEA. In this way it is possible to assess the variation of the torque (ripple) versus the angle of rotation of the input or output shaft. A parametric investigation examining the influence of the ferromagnetic segment thickness on the resulting torque ripple of a specific drive was carried out illustrating the benefits of the analytical models developed herein.

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22

Li, Xinmin, Guokai Jiang, Wei Chen, Tingna Shi, Guozheng Zhang, and Qiang Geng. "Commutation Torque Ripple Suppression Strategy of Brushless DC Motor Considering Back Electromotive Force Variation." Energies 12, no. 10 (May 20, 2019): 1932. http://dx.doi.org/10.3390/en12101932.

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This paper presents a commutation torque ripple suppression strategy for brushless DC motor (BLDCM) in the high-speed region, which considers the back electromotive force (back-EMF) variation during the commutation process. In the paper, the influence of actual back-EMF variation on the torque and outgoing phase current during the commutation process is analyzed. A modified smooth torque mechanism is then reconstructed considering the back-EMF variation, based on which a novel torque ripple suppression strategy is further designed. Compared with the traditional strategy which controls the chopping duty cycle relatively smoothly in the commutation process, the proposed strategy dynamically regulates the chopping duty cycle, which makes it show a gradual decrease. This strategy can suppress the commutation torque ripple even in a long commutation process, and broaden the speed range of the commutation torque ripple reduction. Under the experimental conditions of this paper, the proposed strategy can effectively reduce the commutation torque ripple in the high-speed region, and avoid the outgoing phase current cannot be reduced to zero. The experimental results verify the correctness of the theoretical analysis and the feasibility of the proposed strategy.

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23

Nechaev, Dmitry I., Olga N. Milekhina, and Alexander Ya Supin. "Estimates of Ripple-Density Resolution Based on the Discrimination From Rippled and Nonrippled Reference Signals." Trends in Hearing 23 (January 2019): 233121651882443. http://dx.doi.org/10.1177/2331216518824435.

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Rippled-spectrum stimuli are used to evaluate the resolution of the spectro-temporal structure of sounds. Measurements of spectrum-pattern resolution imply the discrimination between the test and reference stimuli. Therefore, estimates of rippled-pattern resolution could depend on both the test stimulus and the reference stimulus type. In this study, the ripple-density resolution was measured using combinations of two test stimuli and two reference stimuli. The test stimuli were rippled-spectrum signals with constant phase or rippled-spectrum signals with ripple-phase reversals. The reference stimuli were rippled-spectrum signals with opposite ripple phase to the test or nonrippled signals. The spectra were centered at 2 kHz and had an equivalent rectangular bandwidth of 1 oct and a level of 70 dB sound pressure level. A three-alternative forced-choice procedure was combined with an adaptive procedure. With rippled reference stimuli, the mean ripple-density resolution limits were 8.9 ripples/oct (phase-reversals test stimulus) or 7.7 ripples/oct (constant-phase test stimulus). With nonrippled reference stimuli, the mean resolution limits were 26.1 ripples/oct (phase-reversals test stimulus) or 22.2 ripples/oct (constant-phase test stimulus). Different contributions of excitation-pattern and temporal-processing mechanisms are assumed for measurements with rippled and nonrippled reference stimuli: The excitation-pattern mechanism is more effective for the discrimination of rippled stimuli that differ in their ripple-phase patterns, whereas the temporal-processing mechanism is more effective for the discrimination of rippled and nonrippled stimuli.

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24

Chen, Xin, and Xiping Yu. "A Numerical Study on Oscillatory Flow-Induced Sediment Motion over Vortex Ripples." Journal of Physical Oceanography 45, no. 1 (January 2015): 228–46. http://dx.doi.org/10.1175/jpo-d-14-0031.1.

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AbstractA two-dimensional, two-phase flow model is applied to the study of sediment motion over vortex ripples under oscillatory flow conditions. The Reynolds-averaged continuity equations and momentum equations for both the fluid and sediment phases, which include the drag force, the added mass force, the lift force for interphase coupling, and the standard k–ε turbulence model as well as the Henze–Tchen particle turbulence model for closure, are numerically solved with a finite-volume method. The model is effective over the whole depth from the undisturbed sandy bed to the low concentration region above the ripples. Neither a reference concentration nor a pickup function is required over the ripple bed as in a conventional advection–diffusion model. There is also no need to identify the bed load and the suspended load. The study focuses on the effects of erodible ripples on the intrawave flow and sediment motion over the ripples. The computational results show reasonable agreement with the available laboratory data. It is demonstrated that the formation–ejection process of vortices and the trapping–lifting process of sediment over vortex ripples can be well described by the two-phase flow model. The numerical model can also accurately predict the vertical distribution of the mean sediment concentration.

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25

SONG, FENGQI, ZHENLIN LI, XUEFEI LI, LU ZHANG, MIN HAN, and GUANGHOU WANG. "ION SPUTTERING NANOSTRUCTURING CRYSTALLINE MgF2 SURFACE AND ITS ENERGY-DEPENDENT SURFACE ROUGHNESS." Modern Physics Letters B 19, no. 04 (February 28, 2005): 157–62. http://dx.doi.org/10.1142/s0217984905008207.

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The topography of crystalline MgF 2 surfaces eroded by low energy Ar + beam has been investigated by atomic force microscopy (AFM). Applying the optimal experimental parameters, regular nanoripples of 83 nm wavelength have been fabricated on the surface and the ripples direction is parallel to the ion beam. It is also found that both the surface roughness and the ripple direction are of obvious energy dependence, which we attribute to competing balance between kinetic roughening and ion-induced surface diffusion. We also explain why the roughness value of produced ripples reaches maximum at a rather medium energy point, instead of increasing with the ion energy.

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26

Nechaev, Dmitry I., Olga N. Milekhina, Marina S. Tomozova, and Alexander Y. Supin. "High Ripple-Density Resolution for Discriminating Between Rippled and Nonrippled Signals: Effect of Temporal Processing or Combination Products?" Trends in Hearing 25 (January 2021): 233121652110101. http://dx.doi.org/10.1177/23312165211010163.

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The goal of the study was to investigate the role of combination products in the higher ripple-density resolution estimates obtained by discrimination between a spectrally rippled and a nonrippled noise signal than that obtained by discrimination between two rippled signals. To attain this goal, a noise band was used to mask the frequency band of expected low-frequency combination products. A three-alternative forced-choice procedure with adaptive ripple-density variation was used. The mean background (unmasked) ripple-density resolution was 9.8 ripples/oct for rippled reference signals and 21.8 ripples/oct for nonrippled reference signals. Low-frequency maskers reduced the ripple-density resolution. For masker levels from −10 to 10 dB re. signal, the ripple-density resolution for nonrippled reference signals was approximately twice as high as that for rippled reference signals. At a masker level as high as 20 dB re. signal, the ripple-density resolution decreased in both discrimination tasks. This result leads to the conclusion that low-frequency combination products are not responsible for the task-dependent difference in ripple-density resolution estimates.

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27

Abdullah, Nurfaezah, Raja Nor Firdaus Raja Othman, Kasrul Abdul Karim, and Lim Seng Tat. "Analysis on EMF characteristics for torque ripple reduction in BLAC motor intended for HVLS fan application." International Journal of Power Electronics and Drive Systems (IJPEDS) 11, no. 4 (December 1, 2020): 2203. http://dx.doi.org/10.11591/ijpeds.v11.i4.pp2203-2211.

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This paper analyzes the harmonic characteristics of electromagnetic force (EMF) in Brushless Alternating Current (BLAC) motor for High Volume Low Speed (HVLS) fan application. Vibration and noise are one of the main crucial things in HVLS fan application. It comes from torque ripples which can be detected by harmonics of Electro Magnetic Force (EMF). Commonly, there are a few methods to eliminate the noise and vibrations issue, but most literatures only focus on small motor and not intended for HVLS fan application. Thus, the objective of this paper is to eliminate the harmonics content in EMF at early stage design. Through EMF harmonics the expected torque produced could be used to select proper slot-pole number in order to eliminate the noise and vibrations issue. In here, the analysis involves three different slot-pole numbers which are 18s/20p, 12s/10p and 9s/8p BLAC model, respectively. All models have similar volume of permanent magnet. The analysis is carried out using FLUX 2D Finite Element Analysis (FEA) for EMF computational and transient torque computation. Later, Fast Fourier Transform (FFT) analysis is used to calculate the harmonics of EMF. The analysis stage includes the EMF parameter analysis, harmonics and torque ripples analysis. It was found that 18s/20p has higher output torque with the lowest 5% torque ripple value. As a conclusion, this paper presents low torque ripple in point of view of the EMF characteristics in designing HVLS fan.

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28

Farong, Kou, Li Yangkang, Chen Chen, and Hong Feng. "Thrust Ripple Force Minimization and Efficiency Analysis of Electromagnetic Actuator on Active Suspension." Shock and Vibration 2020 (March 10, 2020): 1–13. http://dx.doi.org/10.1155/2020/2572534.

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A novel electromagnetic actuator for active suspension is designed on an in-wheel motor electric vehicle in this paper. Aiming at reducing thrust ripple force and improving stability of the actuator, a method of calculating the optimum slot width and optimizing edge radian of end tooth is proposed. Firstly, a finite element model (FEM) of the actuator is modeled, and the correctness of FEM is verified through comparisons of simulation results and analytical ones, including counterelectromotive force of coil winding and force characteristic test of the actuator. Based on the FEM, the influence of slot width on electromagnetic thrust and total harmonic distortion (THD) is analyzed, and the slot width is improved. The side effect of the actuator is considered. By improving the edge radian, the fluctuation of the cogging force and thrust ripple is reduced. In addition, output efficiency and energy feed efficiency of the actuator after reducing thrust ripple are studied. The results show the minimum THD is 4.2%, which is obtained at the slot width 4.3 mm, and thrust ripple is 36.5 N. When the edge radian is 60°, the thrust ripple decreases to only 15.7 N, which is reduced by 57.0%. The maximum output efficiency and energy feedback efficiency of the actuator are 87.5% and 27.1%, respectively. Finally, according to actuator characteristic tests of two working modes, it is concluded that the maximum energy feedback efficiency is 25.6%. The input current and current frequency should be gradually increased with the increase of suspension speed under active mode, and the maximum output efficiency is 80.2%. The test results are basically consistent with the FEM analysis values, which verify the correctness of the FEM analysis.

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29

Yan, Liang, Lei Zhang, Nan Yao, Zong Xia Jiao, I. Ming Chen, and Chin Yin Chen. "Design and Analysis of Tubular Linear Machines with Dual Halbach Arrays." Applied Mechanics and Materials 284-287 (January 2013): 667–71. http://dx.doi.org/10.4028/www.scientific.net/amm.284-287.667.

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Linear machines are widely employed in robotics, transportation and manufacturing industries because complex rotation-to-translation conversion mechanism is no longer required. This paper proposed a novel tubular linear machine with dual permanent magnet (PM) Halbach arrays to achieve high force output performance. Based on Lorentz force law, the magnetic force output and force ripple for three-phase winding linear machine is formulated in analytical way. By taking advantage of the analytical models, the force output is simulated with respect to the motion of the mover. Numerical result is then obtained to validate the analytical force models. In addition, based on the technology of non-dimensionalization, the mathematical force models are employed to analyze the influence among the structure parameters on the force output and force ripple for design purpose of the tubular linear machines. The study in this paper could contribute to the design analysis and optimization of electromagnetic linear machines with similar poles patterns.

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30

Chanda, Anupama, Joydip Sengupta, and Chacko Jacob. "Well-Ordered "Ripple-Shaped" Microstructures of Mn Thin Films on GaAs Substrates." Advanced Science, Engineering and Medicine 11, no. 11 (November 1, 2019): 1142–47. http://dx.doi.org/10.1166/asem.2019.2434.

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This study was aimed to investigate the thickness dependent morphological changes of Mn films deposited on GaAs substrates by thermal evaporation technique. Ni films were deposited under same conditions to perform comparative study of the morphological changes with respect to the Mn films. The scanning electron microscopy and atomic force microscopy studies revealed ripple-shaped structure of Mn film with good periodicity, while Ni film only exhibited small granules deposited throughout the surface. The influence of the thickness of the Mn film in producing the ripple structure was clearly observed. In addition, the annealing time was considered as the major parameter to control the ordering of the ripple structure. X-ray diffraction pattern indicated the formation of different phases of Ga-Mn and Mn-As due to diffusion of atoms during annealing. A model for the creation of stress-driven microstructure is proposed which indicates that Mn thin films grow on GaAs substrates in three stages: in the primary stage, the growth occurs via two-dimensional nucleation process; as the thickness increases, the stress is released by the film via creation of additional surface roughness which produce ripples; and finally an island-like growth occurs because of the non-uniform distribution of stress along the surface of the film.

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31

P S, Rekha, and Vijayakumar T. "Torque ripple and noise control of switched reluctance motor using an adaptive fuzzy PI control with the aid of AR algorithm." International Journal of Power Electronics and Drive Systems (IJPEDS) 12, no. 2 (June 1, 2021): 1239. http://dx.doi.org/10.11591/ijpeds.v12.i2.pp1239-1251.

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In recent days switched reluctance motor is widely used for numerous industrial applications due to its simple structure, minimum cost and maximum efficiency. Regardless of numerous exclusive benefits of the switched reluctance motor (SRM), acoustic noise of this motor is high and it is important to accomplish more analysis on the noise lessening, which is the primary goal of this paper. The major causes of acoustic noise in a SRM are torque ripple and radial magnetic force. Since radial magnetic force is highly influential by the design of motor, torque ripple control is analysed in this article for acoustic noise control. Torque ripple control of SRM is proposed using optimization in direct torque control (DTC) method. Nowadays, optimisation plays a crucial role in motor drives for enhanced control. In this paper, artificial raindrop algorithm is proposed in DTC of SRM to minimise torque ripple. Performance of proposed ARA based DTC of four-phase 8/6 SRM is analysed using Matlab and compared with the performance of fuzzy gain scheduling PI controller based DTC.

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32

Majumdar, Angshudeep, and Tapas Kumar Bhattacharya. "Source Independence of Force Ripple in Linear Induction Machines." IEEE Transactions on Industry Applications 56, no. 5 (September 2020): 4769–84. http://dx.doi.org/10.1109/tia.2020.3001511.

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33

Downey, Ryan J., Mark Tate, Hiroyuki Kawai, and Warren E. Dixon. "Comparing the force ripple during asynchronous and conventional stimulation." Muscle & Nerve 50, no. 4 (August 5, 2014): 549–55. http://dx.doi.org/10.1002/mus.24186.

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34

Varshney, Prateek, Vivek Sajal, K. P. Singh, Ravindra Kumar, and Navneet K. Sharma. "Strong terahertz radiation generation by beating of extra-ordinary mode lasers in a rippled density magnetized plasma." Laser and Particle Beams 31, no. 2 (June 2013): 337–44. http://dx.doi.org/10.1017/s0263034613000062.

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AbstractA scheme of terahertz radiation generation is proposed by beating of two extra-ordinary lasers having frequencies and wave numbers$\lpar {\rm \omega}_1\comma \; \vec k_1 \rpar $and$\lpar {\rm \omega}_2\comma \; \vec k_2 \rpar $, respectively in a magnetized plasma. Terahertz wave is resonantly excited at frequency$\lpar {\rm \omega}_1 - {\rm \omega}_2 \rpar $and wave number (k1 − k2 + q) with a wave number mismatch factorqwhich is introduced by the periodicity of plasma density ripples. In this process, the lasers exert a beat ponderomotive force on plasma electrons and impart them an oscillatory velocity with both transverse and longitudinal components in the presence of transverse static magnetic field. The oscillatory velocity couples with density ripples and produces a nonlinear current that resonantly excites the terahertz radiation. Effects of periodicity of density ripples and applied magnetic field are analyzed for strong THz radiation generation. The terahertz radiation generation efficiency is found to be directly proportional to the square of density ripple amplitude and rises with the magnetic field strength. With the optimization of these parameters, the efficiency ~10−3is achieved in the present scheme. The frequency and power of generated THz radiation can be better tuned with the help of parameters like density ripple amplitude, periodicity and applied magnetic field strength in the present scheme.

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35

PUROHIT, GUNJAN, H. D. PANDEY, and R. P. SHARMA. "Effect of cross focusing of two laser beams on the growth of laser ripple in plasma." Laser and Particle Beams 21, no. 4 (October 2003): 567–72. http://dx.doi.org/10.1017/s0263034603214154.

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This article presents an effect of cross focusing of two laser beams on the growth of a laser ripple in laser-produced plasmas. The mechanism of nonlinearity is assumed to be ponderomotive force, arising because of the Gaussian intensity distribution of the laser beams. The dynamical equation governing the laser ripple intensity has been set up and a numerical solution has been presented for typical laser plasma parameters. It is found that the change in the intensity of the second laser beam can affect the growth of the laser ripple significantly.

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36

Huh, K., S. Han, and B. Lee. "Non-linear adaptive control of a linear-motor-driven X—Y table via estimating friction and ripple forces." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 222, no. 6 (June 1, 2008): 911–18. http://dx.doi.org/10.1243/09544062jmes859.

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The linear motors are easily affected by load disturbance, ripple force, friction, and parameter variations because there is no mechanical transmission to reduce the effects of external disturbance. For high-speed/high-accuracy position control of a linear-motor-driven X—Y table, a non-linear adaptive controller including a cross-coupling algorithm is proposed in this paper. The non-linear effects such as friction and ripple force are estimated and compensated. The cross-coupling algorithm is adopted to reduce the contour error of the two-axial system. The performance of the proposed controller is evaluated through the computer simulations and experiments.

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37

Singh, Arvinder, and Tarsem Singh. "The effect of a static magnetic field on the growth of a rippled electromagnetic beam." Journal of Plasma Physics 43, no. 3 (June 1990): 465–74. http://dx.doi.org/10.1017/s0022377800014914.

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This paper presents an investigation of the growth of a radially symmetrical ripple, superimposed on a Gaussian electromagnetic beam in a collisionless magnetized plasma. On account of the non-uniform intensity distribution of the main beam, the d.c. component of the ponderomotive force becomes finite and leads to modification of the background density. There is feedback from the main beam to the ripple, which subsequently grows at the cost of the pump wave. The effect of the plasma and pump parameters is studied in detail. An interesting feature is that the ripple always grows, irrespective of the phase relationship of the main beam and the ripple. This is due to strong self-focusing of the main beam for the chosen set of parameters.

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38

Varshney, Prateek, Ajit Upadhayay, K. Madhubabu, Vivek Sajal, and J. A. Chakera. "Strong terahertz radiation generation by cosh-Gaussian laser beams in axially magnetized collisional plasma under non-relativistic ponderomotive regime." Laser and Particle Beams 36, no. 2 (June 2018): 236–45. http://dx.doi.org/10.1017/s0263034618000216.

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AbstractWe propose a scheme for terahertz (THz) radiation generation by non-linear mixing of two cosh-Gaussian laser beams in axially magnetized plasma with spatially periodic density ripple where electron-neutral collisions have been taken into account. The laser beams exert a non-linear ponderomotive force due to spatial non-uniformity in the intensity. The plasma electrons acquire non-linear oscillatory velocity under the influence of ponderomotive force. This oscillatory velocity couples with preformed density ripples (n′ = n0αeiαz) to generate a strong transient non-linear current that resonantly derives THz radiation of frequency ~ωh (upper hybrid frequency). Laser frequencies (ω1 and ω2) are chosen such that the beat frequency (ω) lies in the THz region. The periodicity of density ripple provides phase-matching conditions (ω = ω1 − ω2 and $\vec k = \vec k_1 - \vec k_2 + {\rm \vec \alpha} $) to transfer maximum momentum from laser to THz radiation. The axially applied external magnetic field can be utilized to enhance the non-linear coupling and control various parameters of generated THz wave. The effects of decentered parameters (b), collisional frequency (νen), and magnetic field strength (B0 = ωcm/e) are analyzed for strong THz radiation generation. Analytical results show that the amplitude of THz wave enhances with decentered parameters as well as with the magnitude of axially applied magnetic field. The THz amplitude is found to be highly sensitive to collision frequency.

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39

Zhang, Gan, Wenfei Yu, Wei Hua, Ruiwu Cao, Hongbo Qiu, and Aili Guo. "The Design and Optimization of an Interior, Permanent Magnet Synchronous Machine Applied in an Electric Traction Vehicle Requiring a Low Torque Ripple." Applied Sciences 9, no. 17 (September 3, 2019): 3634. http://dx.doi.org/10.3390/app9173634.

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An internal permanent magnet synchronous machine (IPMSM) was designed for heavy-load traction vehicles applied in port transportation. Based on finite element analysis (FEA), the rotor iron core topology was optimized with the most attention paid to cogging torque and torque ripple. The influences of the iron core on the air-gap magnetic flux density, the back electro-motive-force harmonic, the cogging torque and the torque ripple were investigated. The design scheme of minimizing cogging torque and output torque ripple was obtained. Focused on the relationship between the rotor parameters and the torque ripple, the relative sensitivity factor was proposed and analyzed. Finally, the torque ripple was reduced from 14.4% to 3.84%, after further optimization of the rotor design parameters. The reliability and stability of the IPMSM were also covered. Additionally, the experimental study of the prototype was carried out to verify the FEA results.

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40

Rosić, Marko, Branko Koprivica, and Miroslav Bjekić. "Smart DTC algorithm with automatic torque ripple adjustment." Journal of Electrical Engineering 73, no. 2 (April 1, 2022): 88–98. http://dx.doi.org/10.2478/jee-2022-0012.

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Abstract The paper presents a direct torque control method with possibilities of automatic algorithm modification in terms of torque ripple reduction. The algorithm is based on the conventional switching table with an arbitrary number of discretized voltage levels allowing higher space-voltage resolution and consequently lower torque ripple. The number of available voltage levels can be easily changed and subsequently torque ripple reduced without the need to modify the conventional switching table. Appropriate algorithm modifications leading to torque ripple reduction are automatized, making this kind of control method simple, effective, and suitable for upcoming smart drives in the rapidly growing industry 4.0. Selective back electromotive force compensation can also be part of automatization with the aim to improve the drive dynamics. Experimental validation presented in the paper confirms improvements in torque ripple reduction retaining the simple and time-effective control structure of the induction machine DTC drive.

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41

Mohammed, Jamal Abdul-Kareem, Farag Mahel Mohammed, and Raghda'a Ahmed A. Ali. "Design and Optimization of a Surface-Mounted Permanent-Magnet Linear Synchronous Motor with Maxwell ANSYS." Al-Khwarizmi Engineering Journal 15, no. 3 (August 21, 2019): 1–15. http://dx.doi.org/10.22153/kej.2019.01.005.

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Linear motor offers several features in many applications that require linear motion. Nevertheless, the presence of cogging force can deteriorate the thrust of a permanent magnet linear motor. Using several methodologies, a design of synchronous single sided linear iron-core motor was proposed. According to exact formulas with surface-mounted magnets and concentrated winding specification, which are relying on geometrical parameters. Two-dimensional performance analysis of the designed model and its multi-objective optimization were accomplished as a method to reduce the motor cogging force using MAXWELL ANSYS. The optimum model design results showed that the maximum force ripple was approximatrly reduced by 81.24%compared to the original model with a smaller ripple coefficient of 0.22. Likewise, the model was redesigned taking into consideration two cases; laminated core and solid core. It was found that the error between the analytical and numerical results of the output force did not exceed 0.0967%.

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42

Ruvinsky, K. D., F. I. Feldstein, and G. I. Freidman. "Numerical simulations of the quasi-stationary stage of ripple excitation by steep gravity–capillary waves." Journal of Fluid Mechanics 230 (September 1991): 339–53. http://dx.doi.org/10.1017/s0022112091000812.

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The dependence of the parameters of capillary–gravity ripples on the characteristics of the steep surface waves (in the range 4–20 cm) that excite them is found. For steep 4–6 cm waves calculations are performed on the basis of the improved first Stokes method. Qualitative coincidence of the theoretical results with the experimental data is shown. For 7–20 cm waves the results are obtained by the multiple-scale method where the large-scale motion and the driving force for the ripple are found by the improved first Stokes method. Qualitative agreement between theory and experiment in this wavelength range is achieved.

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43

Liu, Man Lan, Tian Da Yu, Shu Mei Cui, and David He. "Study on Electromagnetic Exciting Force Characteristics and Electromagnetic Noise of Permanent Magnet DC Motor." Applied Mechanics and Materials 128-129 (October 2011): 323–28. http://dx.doi.org/10.4028/www.scientific.net/amm.128-129.323.

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Electromagnetic exciting force is the key to generate electromagnetic noise. The characteristics of electromagnetic exciting force and the causing of electromagnetic noise were analyzed after the power was off for cooling fan Permanent Magnet DC (PMDC) motor. Time-stepping finite element method was selected to calculate its several parameters, such as air gap magnetic density harmonics generated by the stator and rotor, torque ripple and unbalanced magnetic pull at its different speed.Experiment on unloading vibration noise was carried out to confirm the validity of electromagnetic exciting force analysis. The results show: electromagnetic force amplitude keeps constant while the motor speed changing. Torque ripple decreases while the motor speed down. A kind of electromagnetic noise called howling noise produced by PMDC motor used in car cooling fan is mainly due to resonance. So the best way to eliminate this motor’s noise is to improve the order of electromagnetic waves and avoid the electromagnetic resonance.

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44

Woo, Jong-Hyeon, Sung-Won Seo, Tae-Kyoung Bang, and Jang-Young Choi. "Characteristic Analysis of Force Ripple Reduction in Linear Magnetic Gear." Transactions of The Korean Institute of Electrical Engineers 69, no. 2 (February 29, 2020): 258–64. http://dx.doi.org/10.5370/kiee.2020.69.2.258.

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45

Tang, Meiling, Yu Zou, Shengxian Zhuang, and Ka Wai Eric Cheng. "Force and Velocity Ripple Reduction of the New Linear Motor." IEEE Access 9 (2021): 156030–42. http://dx.doi.org/10.1109/access.2021.3123742.

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46

Lu, Qinfen, Yanxin Li, Yunyue Ye, J. T. Chen, and Z. Q. Zhu. "Novel linear switched-flux PM machine with 9/10 primary/secondary pole number combination." COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering 34, no. 6 (November 2, 2015): 1656–72. http://dx.doi.org/10.1108/compel-11-2014-0311.

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Purpose – Due to linear structure, linear switched flux permanent magnet machines (LSFPMMs) also may have odd pole primary, such as 9, 15, 21, etc., without unbalanced magnetic force in equivalent rotary machines. The paper aims to discuss these issues. Design/methodology/approach – In order to increase the thrust force density, the influence of some major design parameters, including split ratio, PM thickness, primary slot width and secondary pole width, are investigated by finite element analysis. For reducing the thrust force ripple under on-load condition, the end auxiliary teeth are adopted and their positions are also optimized. Findings – This novel 9/10 primary/secondary poles LSFPMM has high average thrust force and low thrust force ripple by optimization. The results demonstrate that the odd pole primary may be a good candidate for long-stroke linear direct drive application. Originality/value – A novel 9/10 primary/secondary poles linear switched flux permanent magnet machine is developed in this paper. The similar conclusions could be obtained for other LSFPMMs with odd pole primary.

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47

Xia, Jia Kuan, Ye Yuan, and Wei Huang. "Torque Ripple Reduction of Brushless DC Servo Motor Using Full EMF Feedback." Advanced Materials Research 383-390 (November 2011): 4878–83. http://dx.doi.org/10.4028/www.scientific.net/amr.383-390.4878.

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Torque ripple reduction of the brushless DC motor has been the main issue of the servo drives in which the speed fluctuation and the vibration should be minimized. Un-ideal back EMF (electromagnetic force) usually induces distinct torque ripple. A full EMF feedback strategy is presented in order to effectively reduce torque ripple. The relationship between the terminal voltage of auxiliary winding and the back EMF of brushless DC motor are investigated, and the back EMF can be measured on-line by using the auxiliary winding, the q-axis current for a constant torque to produce is calculated through coordinate transformation when d-axis current is zero, and the reference q-axis current is adjusted in real time by vector control in dq0 coordinate. The simulation results show that the proposed strategy can effectively minimize the torque ripple.

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48

Bharatiraja, C., Shyam Babu, V. Krishnakumar, P. Sanjeevikumar, and Nixon George. "Investigation of Slim Type BLDC Motor Drive with Torque Ripple Minimization using Abridged Space-Vector PWM Control Method." International Journal of Power Electronics and Drive Systems (IJPEDS) 8, no. 2 (June 1, 2017): 593. http://dx.doi.org/10.11591/ijpeds.v8.i2.pp593-600.

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Brushless DC (BLDC) motors are becoming an increasingly popular motor of choice for its unique characteristics. The BLDC motor drive is assumed to have trapezoidal back-electromotive force (EMF), rectangular phase currents and together produces the desired torque. However, practical back-EMF waveform might not be exactly trapezoidal because of current ripple, design considerations and manufacturing limitations. The adverse effect is the torque ripple generated due to the current ripple that causes mechanical vibration, acoustic noise and affects the accuracy of speed and position control which is not desirable in motor operation. In this paper an algorithm is developed to control and minimize the generated torque ripple using Space Vector Pulse Width Modulation (SVPWM) scheme. The efficiency improvement of slim type BLDC motor is confirmed using MATLAB environment and low cost TI Piccolo F28035 microcontroller (MC).

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49

Cetin, E., and F. Daldaban. "Reducing Torque Ripples of the Axial Flux PM Motors by Magnet Stepping and Shifting." Engineering, Technology & Applied Science Research 8, no. 1 (February 20, 2018): 2385–88. http://dx.doi.org/10.48084/etasr.1700.

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Higher efficiency on electric machines is the research goal of many studies. An example is the axial flux permanent magnet machines. These machines have some advantages like their watt/kg efficiency and torque density. This study aims to develop the performance characteristics of the axial flux permanent magnet machines. A new rotor magnet poles design in axial flux machines is suggested to mitigate the torque ripples. The method of stepping and shifting of the magnets is used. Two different designs are compared to verify the proposed approach. 3D finite element analysis is used for simulations. Torque ripple and back electromotive force waveforms are obtained from computer analysis. As a conclusion, the suggested method is found to be useable and mitigates the torque ripples. In addition to that, back EMF waveforms are turned to sinusoidal by the suggested design.

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50

Yang, Zebin, Lin Chen, Xiaodong Sun, Weiming Sun, and Dan Zhang. "A Bearingless Induction Motor Direct Torque Control and Suspension Force Control Based on Sliding Mode Variable Structure." Mathematical Problems in Engineering 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/2409179.

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Анотація:

Aiming at the problems of the large torque ripple and unstable suspension performance in traditional direct torque control (DTC) for a bearingless induction motor (BIM), a new method of DTC is proposed based on sliding mode variable structure (SMVS). The sliding mode switching surface of the torque and flux linkage controller are constructed by torque error and flux error, and the exponential reaching law is used to design the SMVS direct torque controller. On the basis of the radial suspension force mathematical model of the BIM, a radial suspension force closed-loop control method is proposed by utilizing the inverse system theory and SMVS. The simulation models of traditional DTC and the new DTC method based on SMVS of the BIM are set up in the MATLAB/Simulink toolbox. On this basis, the experiments are carried out. Simulation and experiment results showed that the stable suspension operation of the BIM can be achieved with small torque ripple and flux ripple. Besides, the dynamic response and suspension performance of the motor are improved by the proposed method.

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