Toroidal torques,generated by the resonant magnetic perturbation(RMP)and acting on the plasma column,are numerically systematically investigated for an ITER baseline scenario.The neoclassical toroidal viscosity(NTV),i...Toroidal torques,generated by the resonant magnetic perturbation(RMP)and acting on the plasma column,are numerically systematically investigated for an ITER baseline scenario.The neoclassical toroidal viscosity(NTV),in particular the resonant portion,is found to provide the dominant contribution to the total toroidal torque under the slow plasma flow regime in ITER.While the electromagnetic torque always opposes the plasma flow,the toroidal torque associated with the Reynolds stress enhances the plasma flow independent of the flow direction.A peculiar double-peak structure for the net NTV torque is robustly computed for ITER,as the toroidal rotation frequency is scanned near the zero value.This structure is found to be ultimately due to a non-monotonic behavior of the wave-particle resonance integral(over the particle pitch angle)in the superbanana plateau NTV regime in ITER.These findings are qualitatively insensitive to variations of a range of factors including the wall resistivity,the plasma pedestal flow and the assumed frequency of the rotating RMP field.展开更多
Clearance-fit(side-fit)spline joints are a key component in a permanent magnet synchronous motor(PMSM)in electric submersible pumping wells.The nonuniform spline clearance affects the output performance of a PMSM.A co...Clearance-fit(side-fit)spline joints are a key component in a permanent magnet synchronous motor(PMSM)in electric submersible pumping wells.The nonuniform spline clearance affects the output performance of a PMSM.A concept for energy conservation is optimized in this study to improve the modeling accuracy of electromagnetic torque.However,most existing computation models are one-way model with a magneto-mechanical simulation.In this study,a more accurate two-way coupling method is presented for simulating the electromagnetic and mechanical characteristics of PMSM.Additionally,importance should be attached to this two-way magneto-mechanical coupling methodology in an actual simulation.The coupled power,electrical and magnetic energy,and electromagnetic torque equations are solved iteratively until convergence for PMSMs with a segmented rotor and a non-segmented rotor.The optimal electromagnetic torque is obtained for different rotor configurations with the change of temperatures and rotational speeds.The results show that the output performance and electromagnetic torque of the PMSM are seriously affected by the effects of two-way magneto-mechanical coupling and nonuniform spline clearance.The proposed two-way coupling model gives more reasonable predictions than other one-way models do,because the power transfer between the electrical and magnetic energy can be modeled more accurately.The self-centralizing performance of clearance-fit splines and the sensitivity to the radial clearance magnitude lead to the reduction of the electromagnetic torque for the PMSM.Additionally,the electromagnetic torques decrease with the enhanced rotor temperatures and rotational speeds.The best rotor temperature and rotational speed are chosen through a comparison of the experimental results,and then the optimal electromagnetic torque is provided to ensure the output performance of the PMSM in electric submersible pumping wells.展开更多
In order to reach a compromise between fast response control and torques matching control in double turboshaft engines,research on nonlinear model predictive control for turboshaft engines based on double engines torq...In order to reach a compromise between fast response control and torques matching control in double turboshaft engines,research on nonlinear model predictive control for turboshaft engines based on double engines torques matching is conducted.Meanwhile,a Nonlinear Model Predictive Control(NMPC)method is proposed,which combines the control index of the power turbine speed with torques matching of double engines creatively.In addition to the control index,the difference of output torques between each engine is also incorporated in the objective function as a penalty term to ensure constant speed control and short torques matching time.Simulation results demonstrate that relative to unilateral torques matching,the settling time of the bidirectional matching method can be reduced by nearly 30.8%.Nevertheless,compared with the bidirectional torques matching method under the cascade PID controller,the NMPC method can decrease the overshoot of the power turbine speed by 65%and reduce the matching time by 15.5%synchronously.Besides fast response control of turboshaft engines,fast torques matching control of double engines is accomplished as well.展开更多
The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field,as well as the synchronous parasitic torques,radial magnetic forc...The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field,as well as the synchronous parasitic torques,radial magnetic forces have been discussed in great detail in the literature,but always separately,for a long time.However,systematization of the phenomenon still awaits.Therefore,it is worth summarizing the completeness of the phenomena in a single study–with a new approach at the same time-in order to reveal the relationships between them.The role of rotor slot number is emphasized much more than before.New formulas derived for both synchronous torques and radial magnetic forces are used for further investigation.It will be shown that both phenomena in subject must be treated together.Formulas will be provided to take into account attenuation.Design guide will be provided to avoid dangerous rotor slot numbers.It will be shown that the generation of synchronous torques and radial magnetic forces do not depend–in this new approach-on the slot combination,but on the rotor slot number itself.展开更多
Antiferromagnets offer considerable potential for electronic device applications. This article reviews recent demonstrations of spin manipulation in antiferromagnetic devices using applied electrical currents. Due to ...Antiferromagnets offer considerable potential for electronic device applications. This article reviews recent demonstrations of spin manipulation in antiferromagnetic devices using applied electrical currents. Due to spin–orbit coupling in environments with particular crystalline or structural symmetries, the electric current can induce an effective magnetic field with a sign that alternates on the lengthscale of the unit cell. The staggered effective field provides an efficient mechanism for switching antiferromagnetic domains and moving antiferromagnetic domain walls, with writing speeds in the terahertz regime.展开更多
Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientifi...Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientific progress and related applications in the development of information technology. In recent decades, the main motivation in spintronics has been efficiently controlling local magnetization using electron flow or voltage rather than controlling the electron flow using magnetization. Using spin-orbit coupling in a material can convert a charge current into a pure spin current(a flow of spin momenta without a charge flow) and generate a spin-orbit torque on the adjacent ferromagnets. The ability of spintronic devices to utilize spin-orbit torques to manipulate the magnetization has resulted in large-scale developments such as magnetic random-access memories and has boosted the spintronic research area. Here in, we review the theoretical and experimental results that have established this subfield of spintronics. We introduce the concept of a pure spin current and spin-orbit torques within the experimental framework, and we review transport-, magnetization-dynamics-, and opticalbased measurements and link then to both phenomenological and microscopic theories of the effect. The focus is on the related progress reported from Chinese universities and institutes, and we specifically highlight the contributions made by Chinese researchers.展开更多
Here we consider the attitude motion of a satellite, subjected to gravitational and aerodynamic torques in an elliptic orbit. The determination of orientation of equilibrium points has been discussed. It is found that...Here we consider the attitude motion of a satellite, subjected to gravitational and aerodynamic torques in an elliptic orbit. The determination of orientation of equilibrium points has been discussed. It is found that they coincide with those for the circular case as studied by Sarychev and others in the works [1]-[3] and besides we have aimed at the sufficient condition for stability in the sense of Lyapunov.展开更多
The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate ...The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate the articulated torques, which results in a large safety margin or a large number of calculations. To quickly obtain accurate articulated torques, an analysis method for the articulated torque is presented for an electrically driven heavy-duty six-legged robot. First, the rearmost leg that experiences the maximum normal contact force is confirmed when the robot transits a slope. Based on the ant-type and crab-type tripod gaits, the formulas of classical mechanics and MATLAB software are employed to theoretically analyze the relevant static torques of the joints. With the changes in the joint angles for the abductor joint, hip joint, and knee joint, variable tendency charts and extreme curves are obtained for the static articulated torques. Meanwhile, the maximum static articulated torques and the corresponding poses of the robot are also obtained. According to the poses of the robot under the maximum static articulated torques, ADAMS software is used to carry out a static simulation analysis. Based on the relevant simulation curves of the articulated torques, the maximum static articulated torques are acquired. A comparative analysis of the maximum static articulated torques shows that the theoretical calculation values are higher than the static simulation values, and the maximum error value is approximately 10%. The proposed method lays a foundation for quickly determining accurate articulated torques to develop heavy-duty six-legged robots.展开更多
Space robotics is regarded as one of the most impressing approaches for space debris removal missions. Due to the residual momentum of debris, it is essential to stabilize the base rapidly after capture. This paper pr...Space robotics is regarded as one of the most impressing approaches for space debris removal missions. Due to the residual momentum of debris, it is essential to stabilize the base rapidly after capture. This paper presents a novel control strategy for stabilization of a space robot in postcapture considering actuator failures and bounded torques. In the control strategy, the motion of the manipulator is not regarded as a disturbance to the base; in contrast, it is utilized to compensate for the limitation of the control torques by means of an inverse dynamical model of the system. Different scenarios where actuators are external mechanisms or momentum exchange devices have been carried out, and for actuator failures, both single-and two-actuator failures have been considered. Regarding to the performance of actuators, control torques are bounded. In cases that either single or two actuators have failed, the base can be stabilized kinematically when actuators are external mechanisms, but can only be stabilized dynamically when only momentum exchange devices are used. Finally, a space robot with a seven-degree-of-freedom manipulator in postcapture is studied to verify the validity and feasibility of the proposed control scheme. Simulation results show that the whole system can be stabilized rapidly.展开更多
The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field, as well as the related differential leakage, attenuation, asynch...The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field, as well as the related differential leakage, attenuation, asynchronous parasitic torques have been discussed in great detail in the literature, but always separately, for a long time. However, systematization of the phenomenon still awaits. Therefore, it is worth summarizing the completeness of the phenomena in a single study – with a new approach at the same time-in order to reveal the relationships between them. The role of rotor slot number is emphasized much more than before. An existing, commonly used, but still impractical basic figure has been modified to more clearly demonstrate the response of the rotor for the harmonics of the stator. The need to treat differential leakage, asynchronous parasitic torques and attenuation together will be demonstrated: new formula for asynchronous parasitic torque is derived;the long-used characteristic curves for differential leakage and attenuation used separately so far was merged into one, correct curve in order to provide a correct design guide for the engineers.展开更多
We determine the region in which the magnon-mediated spin torques exist.This region can be controlled by the spin waves.In terms of stability analysis of magnetization dynamics based on the spin-wave background,we obt...We determine the region in which the magnon-mediated spin torques exist.This region can be controlled by the spin waves.In terms of stability analysis of magnetization dynamics based on the spin-wave background,we obtain the instability conditions of spin waves.With these results,we find the relationship between unstable regions and the formation of Akhmediev breather,Kuznetsov-Ma breather and rogue waves.We establish the phase diagram of some novel magnetic excitaions.展开更多
The purpose of this study is to measure the forces and torques produced in the drilling process of a non-homogenous material （bone）. An automated 5 DoF CataLyst-5 robot is used during the drilling process and it is ...The purpose of this study is to measure the forces and torques produced in the drilling process of a non-homogenous material （bone）. An automated 5 DoF CataLyst-5 robot is used during the drilling process and it is integrated to a 6 DoF force-torque sensor. A force-torque controller which is built in the Matlab Simulink environment is employed to control the drilling process of the bone. Different feed rate is used during the experimental process of the bone drilling operation. The sensor is calibrated to measure the tri-axial direction of the resultant forces and torques. The profiles of the forces and torques obtained are non-linear due to the diversity of the bone density. The profiles generated also indicated fluctuation in the interface layers of the bone.展开更多
Spin-orbit torque(SOT)effect is considered as an efficient way to switch the magnetization and can inspire various high-performance spintronic devices.Recently,topological insulators(TIs)have gained extensive attentio...Spin-orbit torque(SOT)effect is considered as an efficient way to switch the magnetization and can inspire various high-performance spintronic devices.Recently,topological insulators(TIs)have gained extensive attention,as they are demonstrated to maintain a large effective spin Hall angle(θeff SH),even at room temperature.However,molecular beam epitaxy(MBE),as a precise deposition method,is required to guarantee favorable surface states of TIs,which hinders the prospect of TIs towards industrial application.In this paper,we demonstrate that Bi2Te3 films grown by magnetron sputtering can provide a notable SOT effect in the heterostructure with perpendicular magnetic anisotropy CoTb ferrimagnetic alloy.By harmonic Hall measurement,a high SOT efficiency(8.7±0.9 Oe/(10^9 A/m^2))and a largeθ^eff SH(3.3±0.3)are obtained at room temperature.Besides,we also observe an ultra-low critical switching current density(9.7×10^9 A/m^2).Moreover,the low-power characteristic of the sputtered Bi2Te3 film is investigated by drawing a comparison with different sputtered SOT sources.Our work may provide an alternative to leverage chalcogenides as a realistic and efficient SOT source in future spintronic devices.展开更多
Spin orbit torques(SOTs)in ferromagnet/heavy-metal heterostructures have provided great opportunities for efficient manipulation of spintronic devices.However,deterministically field-free switching of perpendicular ma...Spin orbit torques(SOTs)in ferromagnet/heavy-metal heterostructures have provided great opportunities for efficient manipulation of spintronic devices.However,deterministically field-free switching of perpendicular magnetization with SOTs is forbidden because of the global two-fold rotational symmetry in conventional heavy-metal such as Pt.Here,we engineer the interface of Pt/Ni heterostructures by inserting a monolayer MoTe_(2)with low crystal symmetry.It is demonstrated that the spin orbit efficiency,as well as the out-of-plane magnetic anisotropy and the Gilbert damping of Ni are enhanced,due to the effect of orbital hybridization and the increased spin scatting at the interface induced by MoTe_(2).Particularly,an out-of-plane damping-like torque is observed when the current is applied perpendicular to the mirror plane of the MoTe_(2)crystal,which is attributed to the interfacial inversion symmetry breaking of the system.Our work provides an effective route for engineering the SOT in Pt-based heterostructures,and offers potential opportunities for van der Waals interfaces in spintronic devices.展开更多
A research on the electrostatic torques in the electrostatically suspended gyroscope (ESG) that uses the mass-unbalance modulation (MUM) scheme (MUM-ESG) to sense the direction of the rotor's spinning axis is pres...A research on the electrostatic torques in the electrostatically suspended gyroscope (ESG) that uses the mass-unbalance modulation (MUM) scheme (MUM-ESG) to sense the direction of the rotor's spinning axis is presented here. Spherical harmonic functions are used to describe the asphericity of the rotor and the electrodes. Rotational matrix theory in quantum mechanics is utilized to transform the description of the rotor's asphericity from the rotor-fixed frame into the cavity-fixed frame. And the principle of the virtual displacement is applied to find out the electrostatic torques acting on the rotor. Analytical expressions of the electrostatic torques indicate that there are only three kinds of factors need to be considered when looking for the electrostatic torques in the MUM-ESG. The factors are the asphericity of the rotor, the eccentric rotation of the rotor, and the coupling between the rotor's translational displacement and asphericity. An intuitionistic explanation for the electrostatic torque that comes of the rotor's eccentric rotation is presented also. The effects of these conclusions should be tested and verified in the future experiments and applications.展开更多
BACKGROUND： Lower body strength is considered to be a critical component towards successful exercise performance in football players. The aim of this study was to describe the peak isokinetic torque of the knee in pr...BACKGROUND： Lower body strength is considered to be a critical component towards successful exercise performance in football players. The aim of this study was to describe the peak isokinetic torque of the knee in professional football players of different League divisions in Cyprus and assess bilateral and unilateral asymmetries of strength. METHODS： Four hundred and twenty-nine professional male football players participated in this study （Division 1, n = 245 and Division 2, n = 184）. The isokinetic muscle function of the knee was measured using the Humac Norm Testing and Rehabilitation system （CSMi Medical ＆ Solution, USA）. Measurements were collected at angle speeds of 60 °/sec and 300 °/sec, for 3 and 25- repetitions respectively. RESULTS： At both angle speeds, peak isokinetic torque of the knee joint was significantly higher in the right and left knees of players in Division 1 （D1） compared to those competing in Division 2 （D2）. At both testing speeds, peak flexor torque of the left hamstrings was significantly higher in players participating in Division 1 compared to those competing in Division 2. The right hamstrings yielded similar results, except at 60 °/sec, where no difference was found between the groups. CONCLUSION： This study provides valuable data regarding the forces produced by the lower body of football players participating in D1 and D2 in Cyprus, whilst also disclosing there to be no bilateral imbalances or abnormal H/Q ratios. The results of this study may provide pertinent information that can be used by the coaching staff for training and recruiting purposes.展开更多
The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies.Spin-orbit torque(SOT)has emerged as a leading candidate for high-speed,high-...The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies.Spin-orbit torque(SOT)has emerged as a leading candidate for high-speed,high-density magnetic random-access memory due to its ultrafast switching speed and low power consumption.This review systematically explores the generation and switching mechanisms of electron-mediated torques(including both conventional SOTs and orbital torques)and magnon-mediated torques.We discuss key materials that enable these effects:heavy metals,topological insulators,low-crystal-symmetry materials,non-collinear antiferromagnets,and altermagnets for conventional SOTs;3d,4d,and 5d transition metals for orbital torques;and antiferromagnetic insulator Ni O-and multiferroic Bi Fe O_(3)-based sandwich structures for magnon torques.We emphasize that although key components of SOT devices have been demonstrated,numerous promising materials and critical questions regarding their underlying mechanisms remain to be explored.Therefore,this field represents a dynamic and rapidly evolving frontier in spintronics,offering significant potential for advancing next-generation information storage and computational technologies.展开更多
We report on the development of a“two-field-scan”harmonic Hall voltage(HHV)analysis,which collects the second HHVas a function of a swept in-plane magnetic field at 45°and 0°relative to the excitation curr...We report on the development of a“two-field-scan”harmonic Hall voltage(HHV)analysis,which collects the second HHVas a function of a swept in-plane magnetic field at 45°and 0°relative to the excitation current,for the determination of the spin-orbit torques of transverse spins in magnetic heterostructures without significant perpendicular spins,longitudinal spins,and longitudinal/perpendicular Oersted fields.We demonstrate that this two-field-scan analysis is as accurate as the well-established but time-consuming angle-scan HHV analysis even in the presence of considerable thermoelectric effects but takes more than a factor of 7 less measurement time.We also show that the fit of the HHV data from a single field scan at 0°,which is commonly employed in the literature,is not reliable because the employment of too many free parameters in the fitting of the very slowly varying HHV signal allows erroneous conclusion about the spin-orbit torque efficiencies.展开更多
Ultrafast manipulation of the Néel vector in metallic antiferromagnets most commonly occurs by generation of spin-orbit(SOT)or spin-transfer(STT)torques.Here,we predict another possibility for antiferromagnetic d...Ultrafast manipulation of the Néel vector in metallic antiferromagnets most commonly occurs by generation of spin-orbit(SOT)or spin-transfer(STT)torques.Here,we predict another possibility for antiferromagnetic domain switching by using novel laser optical torques(LOTs).We present results of atomistic spin dynamics simulations from the application of LOTs for all-optical switching of the Néel vector in the antiferromagnet Mn_(2)Au.展开更多
Permanent-magnet(PM)machines are the important driving components of various mechanical equipment and industrial applications,such as robot joints,aerospace equipment,electric vehicles,actuators,wind generators and el...Permanent-magnet(PM)machines are the important driving components of various mechanical equipment and industrial applications,such as robot joints,aerospace equipment,electric vehicles,actuators,wind generators and electric traction systems.The PM machines are usually expected to have high torque/power density,low torque ripple,reduced rotor mass,a large constant power speed range or strong anti-magnetization capability to match different requirements of industrial applications.The structural topology of the electric machines,including stator/rotor arrangements and magnet patterns of rotor,is one major concern to improve their electromagnetic performance.However,systematic reviews of structural topology are seldom found in literature.Therefore,the objective of this paper is to summarize the stator/rotor arrangements and magnet patterns of the permanent-magnet brushless machines,in depth.Specifically,the stator/rotor arrangements of the PM machines including radial-flux,axialflux and emerging hybrid axial-radial flux configurations are presented,and pros and cons of these topologies are discussed regarding their electromagnetic performance.The magnet patterns including various surface-mounted and interior magnet patterns,such as parallel magnetization pole pattern,Halbach arrays,spoke-type designs and their variants are summarized,and the characteristics of those magnet patterns in terms of flux-focusing effect,magnetic self-shielding effect,torque ripple,reluctance torque,magnet utilization ratio,and anti-demagnetization capability are compared.This paper can provide guidance and suggestion for the structure selection and design of PM brushless machines for high-performance industrial applications.展开更多
基金funded by National Natural Science Foundation of China(NSFC)(Nos.12075053,11505021 and 11975068)by National Key R&D Program of China(No.2022YFE 03060002)+1 种基金by Fundamental Research Funds for the Central Universities(No.2232024G-10)supported by the U.S.DoE Office of Science(No.DE-FG02–95ER54309)。
文摘Toroidal torques,generated by the resonant magnetic perturbation(RMP)and acting on the plasma column,are numerically systematically investigated for an ITER baseline scenario.The neoclassical toroidal viscosity(NTV),in particular the resonant portion,is found to provide the dominant contribution to the total toroidal torque under the slow plasma flow regime in ITER.While the electromagnetic torque always opposes the plasma flow,the toroidal torque associated with the Reynolds stress enhances the plasma flow independent of the flow direction.A peculiar double-peak structure for the net NTV torque is robustly computed for ITER,as the toroidal rotation frequency is scanned near the zero value.This structure is found to be ultimately due to a non-monotonic behavior of the wave-particle resonance integral(over the particle pitch angle)in the superbanana plateau NTV regime in ITER.These findings are qualitatively insensitive to variations of a range of factors including the wall resistivity,the plasma pedestal flow and the assumed frequency of the rotating RMP field.
基金financially supported by National Natural Science Foundation of China(Grant Nos.52074161 and 52005281)Taishan Scholar Project of Shandong Province(Grant No.tsqn202211177)+2 种基金Shandong Provincial Plan for Introduction and Cultivation of Young Pioneers in Colleges and Universities(Grant No.2021-Qing Chuang-30613019)Natural Science Foundation of Shandong Province(Grant Nos.ZR2022ME173 and ZR2023QE011)Projects of CNOOC Research Institute Ltd.(Grant Nos.CCL2023RCPS0237RSN and CCL2023RCPS0319RSN)。
文摘Clearance-fit(side-fit)spline joints are a key component in a permanent magnet synchronous motor(PMSM)in electric submersible pumping wells.The nonuniform spline clearance affects the output performance of a PMSM.A concept for energy conservation is optimized in this study to improve the modeling accuracy of electromagnetic torque.However,most existing computation models are one-way model with a magneto-mechanical simulation.In this study,a more accurate two-way coupling method is presented for simulating the electromagnetic and mechanical characteristics of PMSM.Additionally,importance should be attached to this two-way magneto-mechanical coupling methodology in an actual simulation.The coupled power,electrical and magnetic energy,and electromagnetic torque equations are solved iteratively until convergence for PMSMs with a segmented rotor and a non-segmented rotor.The optimal electromagnetic torque is obtained for different rotor configurations with the change of temperatures and rotational speeds.The results show that the output performance and electromagnetic torque of the PMSM are seriously affected by the effects of two-way magneto-mechanical coupling and nonuniform spline clearance.The proposed two-way coupling model gives more reasonable predictions than other one-way models do,because the power transfer between the electrical and magnetic energy can be modeled more accurately.The self-centralizing performance of clearance-fit splines and the sensitivity to the radial clearance magnitude lead to the reduction of the electromagnetic torque for the PMSM.Additionally,the electromagnetic torques decrease with the enhanced rotor temperatures and rotational speeds.The best rotor temperature and rotational speed are chosen through a comparison of the experimental results,and then the optimal electromagnetic torque is provided to ensure the output performance of the PMSM in electric submersible pumping wells.
基金co-supported by the National Natural Science Foundation of China(No.51576096)Qing Lan and 333 Project and Research Funds for Central Universities(No.NF2018003).
文摘In order to reach a compromise between fast response control and torques matching control in double turboshaft engines,research on nonlinear model predictive control for turboshaft engines based on double engines torques matching is conducted.Meanwhile,a Nonlinear Model Predictive Control(NMPC)method is proposed,which combines the control index of the power turbine speed with torques matching of double engines creatively.In addition to the control index,the difference of output torques between each engine is also incorporated in the objective function as a penalty term to ensure constant speed control and short torques matching time.Simulation results demonstrate that relative to unilateral torques matching,the settling time of the bidirectional matching method can be reduced by nearly 30.8%.Nevertheless,compared with the bidirectional torques matching method under the cascade PID controller,the NMPC method can decrease the overshoot of the power turbine speed by 65%and reduce the matching time by 15.5%synchronously.Besides fast response control of turboshaft engines,fast torques matching control of double engines is accomplished as well.
文摘The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field,as well as the synchronous parasitic torques,radial magnetic forces have been discussed in great detail in the literature,but always separately,for a long time.However,systematization of the phenomenon still awaits.Therefore,it is worth summarizing the completeness of the phenomena in a single study–with a new approach at the same time-in order to reveal the relationships between them.The role of rotor slot number is emphasized much more than before.New formulas derived for both synchronous torques and radial magnetic forces are used for further investigation.It will be shown that both phenomena in subject must be treated together.Formulas will be provided to take into account attenuation.Design guide will be provided to avoid dangerous rotor slot numbers.It will be shown that the generation of synchronous torques and radial magnetic forces do not depend–in this new approach-on the slot combination,but on the rotor slot number itself.
基金Project supported by EPSRC(Grant No.EP/P019749/1)support from the Royal Society through a University Research Fellowship
文摘Antiferromagnets offer considerable potential for electronic device applications. This article reviews recent demonstrations of spin manipulation in antiferromagnetic devices using applied electrical currents. Due to spin–orbit coupling in environments with particular crystalline or structural symmetries, the electric current can induce an effective magnetic field with a sign that alternates on the lengthscale of the unit cell. The staggered effective field provides an efficient mechanism for switching antiferromagnetic domains and moving antiferromagnetic domain walls, with writing speeds in the terahertz regime.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674142,51771099,11429401,and 51471081)the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT-16R35)
文摘Spintronics is a new discipline focusing on the research and application of electronic spin properties. After the discovery of the giant magnetoresistance effect in 1988, spintronics has had a huge impact on scientific progress and related applications in the development of information technology. In recent decades, the main motivation in spintronics has been efficiently controlling local magnetization using electron flow or voltage rather than controlling the electron flow using magnetization. Using spin-orbit coupling in a material can convert a charge current into a pure spin current(a flow of spin momenta without a charge flow) and generate a spin-orbit torque on the adjacent ferromagnets. The ability of spintronic devices to utilize spin-orbit torques to manipulate the magnetization has resulted in large-scale developments such as magnetic random-access memories and has boosted the spintronic research area. Here in, we review the theoretical and experimental results that have established this subfield of spintronics. We introduce the concept of a pure spin current and spin-orbit torques within the experimental framework, and we review transport-, magnetization-dynamics-, and opticalbased measurements and link then to both phenomenological and microscopic theories of the effect. The focus is on the related progress reported from Chinese universities and institutes, and we specifically highlight the contributions made by Chinese researchers.
文摘Here we consider the attitude motion of a satellite, subjected to gravitational and aerodynamic torques in an elliptic orbit. The determination of orientation of equilibrium points has been discussed. It is found that they coincide with those for the circular case as studied by Sarychev and others in the works [1]-[3] and besides we have aimed at the sufficient condition for stability in the sense of Lyapunov.
基金supported by National Basic Research Program of China(973 Program, Grant No. 2013CB035502)International Science and Technology Cooperation Project with Russia (Grant No. 2010DFR70270)+2 种基金National Natural Science Foundation of China (Grant No. 51275106)"111" Project (Grant No. B07018)Key Laboratory Opening Funding of Aerospace Mechanism and Control, China (Grant No. HIT. KLOF.2010057)
文摘The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate the articulated torques, which results in a large safety margin or a large number of calculations. To quickly obtain accurate articulated torques, an analysis method for the articulated torque is presented for an electrically driven heavy-duty six-legged robot. First, the rearmost leg that experiences the maximum normal contact force is confirmed when the robot transits a slope. Based on the ant-type and crab-type tripod gaits, the formulas of classical mechanics and MATLAB software are employed to theoretically analyze the relevant static torques of the joints. With the changes in the joint angles for the abductor joint, hip joint, and knee joint, variable tendency charts and extreme curves are obtained for the static articulated torques. Meanwhile, the maximum static articulated torques and the corresponding poses of the robot are also obtained. According to the poses of the robot under the maximum static articulated torques, ADAMS software is used to carry out a static simulation analysis. Based on the relevant simulation curves of the articulated torques, the maximum static articulated torques are acquired. A comparative analysis of the maximum static articulated torques shows that the theoretical calculation values are higher than the static simulation values, and the maximum error value is approximately 10%. The proposed method lays a foundation for quickly determining accurate articulated torques to develop heavy-duty six-legged robots.
基金co-supported by the National Natural Science Foundation of China (Nos. 11402200 and 11502203)the China Scholarship Council (CSC)
文摘Space robotics is regarded as one of the most impressing approaches for space debris removal missions. Due to the residual momentum of debris, it is essential to stabilize the base rapidly after capture. This paper presents a novel control strategy for stabilization of a space robot in postcapture considering actuator failures and bounded torques. In the control strategy, the motion of the manipulator is not regarded as a disturbance to the base; in contrast, it is utilized to compensate for the limitation of the control torques by means of an inverse dynamical model of the system. Different scenarios where actuators are external mechanisms or momentum exchange devices have been carried out, and for actuator failures, both single-and two-actuator failures have been considered. Regarding to the performance of actuators, control torques are bounded. In cases that either single or two actuators have failed, the base can be stabilized kinematically when actuators are external mechanisms, but can only be stabilized dynamically when only momentum exchange devices are used. Finally, a space robot with a seven-degree-of-freedom manipulator in postcapture is studied to verify the validity and feasibility of the proposed control scheme. Simulation results show that the whole system can be stabilized rapidly.
文摘The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field, as well as the related differential leakage, attenuation, asynchronous parasitic torques have been discussed in great detail in the literature, but always separately, for a long time. However, systematization of the phenomenon still awaits. Therefore, it is worth summarizing the completeness of the phenomena in a single study – with a new approach at the same time-in order to reveal the relationships between them. The role of rotor slot number is emphasized much more than before. An existing, commonly used, but still impractical basic figure has been modified to more clearly demonstrate the response of the rotor for the harmonics of the stator. The need to treat differential leakage, asynchronous parasitic torques and attenuation together will be demonstrated: new formula for asynchronous parasitic torque is derived;the long-used characteristic curves for differential leakage and attenuation used separately so far was merged into one, correct curve in order to provide a correct design guide for the engineers.
基金supported by the National Natural Science Foundation of China(Grant No.61774001)the Natural Science Foundation of Hebei Province of China(Grant No.F2019202141)the Program of State Key Laboratory of Quantum Optics and Quantum Optics Devices,Shanxi University,China(Grant No.KF201906).
文摘We determine the region in which the magnon-mediated spin torques exist.This region can be controlled by the spin waves.In terms of stability analysis of magnetization dynamics based on the spin-wave background,we obtain the instability conditions of spin waves.With these results,we find the relationship between unstable regions and the formation of Akhmediev breather,Kuznetsov-Ma breather and rogue waves.We establish the phase diagram of some novel magnetic excitaions.
文摘The purpose of this study is to measure the forces and torques produced in the drilling process of a non-homogenous material （bone）. An automated 5 DoF CataLyst-5 robot is used during the drilling process and it is integrated to a 6 DoF force-torque sensor. A force-torque controller which is built in the Matlab Simulink environment is employed to control the drilling process of the bone. Different feed rate is used during the experimental process of the bone drilling operation. The sensor is calibrated to measure the tri-axial direction of the resultant forces and torques. The profiles of the forces and torques obtained are non-linear due to the diversity of the bone density. The profiles generated also indicated fluctuation in the interface layers of the bone.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61971024 and 51901008)Young Elite Scientist Sponsorship Program by CAST(Grant No.2017QNRC001)+2 种基金the International Mobility Project(Grant No.B16001)National Key Technology Program of China(Grant No.2017ZX01032101)P.K.A.acknowledges support by a grant from the National Science Foundation,Division of Electrical,Communications and Cyber Systems(NSF ECCS-1853879).
文摘Spin-orbit torque(SOT)effect is considered as an efficient way to switch the magnetization and can inspire various high-performance spintronic devices.Recently,topological insulators(TIs)have gained extensive attention,as they are demonstrated to maintain a large effective spin Hall angle(θeff SH),even at room temperature.However,molecular beam epitaxy(MBE),as a precise deposition method,is required to guarantee favorable surface states of TIs,which hinders the prospect of TIs towards industrial application.In this paper,we demonstrate that Bi2Te3 films grown by magnetron sputtering can provide a notable SOT effect in the heterostructure with perpendicular magnetic anisotropy CoTb ferrimagnetic alloy.By harmonic Hall measurement,a high SOT efficiency(8.7±0.9 Oe/(10^9 A/m^2))and a largeθ^eff SH(3.3±0.3)are obtained at room temperature.Besides,we also observe an ultra-low critical switching current density(9.7×10^9 A/m^2).Moreover,the low-power characteristic of the sputtered Bi2Te3 film is investigated by drawing a comparison with different sputtered SOT sources.Our work may provide an alternative to leverage chalcogenides as a realistic and efficient SOT source in future spintronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51732010,51802341,and 12004415)the China Postdoctoral Science Foundation(Grant Nos.2020M671592,2019M661965)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20200255).
文摘Spin orbit torques(SOTs)in ferromagnet/heavy-metal heterostructures have provided great opportunities for efficient manipulation of spintronic devices.However,deterministically field-free switching of perpendicular magnetization with SOTs is forbidden because of the global two-fold rotational symmetry in conventional heavy-metal such as Pt.Here,we engineer the interface of Pt/Ni heterostructures by inserting a monolayer MoTe_(2)with low crystal symmetry.It is demonstrated that the spin orbit efficiency,as well as the out-of-plane magnetic anisotropy and the Gilbert damping of Ni are enhanced,due to the effect of orbital hybridization and the increased spin scatting at the interface induced by MoTe_(2).Particularly,an out-of-plane damping-like torque is observed when the current is applied perpendicular to the mirror plane of the MoTe_(2)crystal,which is attributed to the interfacial inversion symmetry breaking of the system.Our work provides an effective route for engineering the SOT in Pt-based heterostructures,and offers potential opportunities for van der Waals interfaces in spintronic devices.
基金National Defense Pre-research Foundation of China(No.51409060104JW0307)
文摘A research on the electrostatic torques in the electrostatically suspended gyroscope (ESG) that uses the mass-unbalance modulation (MUM) scheme (MUM-ESG) to sense the direction of the rotor's spinning axis is presented here. Spherical harmonic functions are used to describe the asphericity of the rotor and the electrodes. Rotational matrix theory in quantum mechanics is utilized to transform the description of the rotor's asphericity from the rotor-fixed frame into the cavity-fixed frame. And the principle of the virtual displacement is applied to find out the electrostatic torques acting on the rotor. Analytical expressions of the electrostatic torques indicate that there are only three kinds of factors need to be considered when looking for the electrostatic torques in the MUM-ESG. The factors are the asphericity of the rotor, the eccentric rotation of the rotor, and the coupling between the rotor's translational displacement and asphericity. An intuitionistic explanation for the electrostatic torque that comes of the rotor's eccentric rotation is presented also. The effects of these conclusions should be tested and verified in the future experiments and applications.
文摘BACKGROUND： Lower body strength is considered to be a critical component towards successful exercise performance in football players. The aim of this study was to describe the peak isokinetic torque of the knee in professional football players of different League divisions in Cyprus and assess bilateral and unilateral asymmetries of strength. METHODS： Four hundred and twenty-nine professional male football players participated in this study （Division 1, n = 245 and Division 2, n = 184）. The isokinetic muscle function of the knee was measured using the Humac Norm Testing and Rehabilitation system （CSMi Medical ＆ Solution, USA）. Measurements were collected at angle speeds of 60 °/sec and 300 °/sec, for 3 and 25- repetitions respectively. RESULTS： At both angle speeds, peak isokinetic torque of the knee joint was significantly higher in the right and left knees of players in Division 1 （D1） compared to those competing in Division 2 （D2）. At both testing speeds, peak flexor torque of the left hamstrings was significantly higher in players participating in Division 1 compared to those competing in Division 2. The right hamstrings yielded similar results, except at 60 °/sec, where no difference was found between the groups. CONCLUSION： This study provides valuable data regarding the forces produced by the lower body of football players participating in D1 and D2 in Cyprus, whilst also disclosing there to be no bilateral imbalances or abnormal H/Q ratios. The results of this study may provide pertinent information that can be used by the coaching staff for training and recruiting purposes.
基金supported by the National Natural Science Foundation of China(Grant Nos.U24A6002,12174237(X.X.),52471253(F.W.),12404091(J.L.),52171183(Z.Q.))the support from the National Key Research and Development Program of China(Grant No.2022YFB3505301)+4 种基金the support from the Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province(Grant No.20240019)Central Government’s Special Fund for Local Science and Technology Development(Grant No.YDZJSX2024D058)the support from the Basic Research Plan of Shanxi Province(Grant No.202403021212016)the support from the Fundamental Research Program of Shanxi Province(Grant No.202403021222252)the Higher Education Science and Technology Innovation Plan Project of Shanxi(Grant No.2024L146)。
文摘The growing demand for artificial intelligence and complex computing has underscored the urgent need for advanced data storage technologies.Spin-orbit torque(SOT)has emerged as a leading candidate for high-speed,high-density magnetic random-access memory due to its ultrafast switching speed and low power consumption.This review systematically explores the generation and switching mechanisms of electron-mediated torques(including both conventional SOTs and orbital torques)and magnon-mediated torques.We discuss key materials that enable these effects:heavy metals,topological insulators,low-crystal-symmetry materials,non-collinear antiferromagnets,and altermagnets for conventional SOTs;3d,4d,and 5d transition metals for orbital torques;and antiferromagnetic insulator Ni O-and multiferroic Bi Fe O_(3)-based sandwich structures for magnon torques.We emphasize that although key components of SOT devices have been demonstrated,numerous promising materials and critical questions regarding their underlying mechanisms remain to be explored.Therefore,this field represents a dynamic and rapidly evolving frontier in spintronics,offering significant potential for advancing next-generation information storage and computational technologies.
基金supported partly by the Beijing Natural Science Foundation(Grant No.Z230006)the National Key Research and Development Program of China(Grant No.2022YFA1204004)+1 种基金the National Natural Science Foundation of China(Grant No.12274405)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB44000000)。
文摘We report on the development of a“two-field-scan”harmonic Hall voltage(HHV)analysis,which collects the second HHVas a function of a swept in-plane magnetic field at 45°and 0°relative to the excitation current,for the determination of the spin-orbit torques of transverse spins in magnetic heterostructures without significant perpendicular spins,longitudinal spins,and longitudinal/perpendicular Oersted fields.We demonstrate that this two-field-scan analysis is as accurate as the well-established but time-consuming angle-scan HHV analysis even in the presence of considerable thermoelectric effects but takes more than a factor of 7 less measurement time.We also show that the fit of the HHV data from a single field scan at 0°,which is commonly employed in the literature,is not reliable because the employment of too many free parameters in the fitting of the very slowly varying HHV signal allows erroneous conclusion about the spin-orbit torque efficiencies.
基金funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie International Training Network COMRAD(grant agreement No 861300)F.F.and Y.M.acknowledge the funding by the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)−TRR 173/2−268565370(project A11)+1 种基金Sino-German research project DISTOMAT(MO 1731/10-1)of the DFGsupported by DFG via CRC/TRR 227,project ID 328545488(Project MF).
文摘Ultrafast manipulation of the Néel vector in metallic antiferromagnets most commonly occurs by generation of spin-orbit(SOT)or spin-transfer(STT)torques.Here,we predict another possibility for antiferromagnetic domain switching by using novel laser optical torques(LOTs).We present results of atomistic spin dynamics simulations from the application of LOTs for all-optical switching of the Néel vector in the antiferromagnet Mn_(2)Au.
基金Supported by National Natural Science Foundation of China(NSFC)(Grant No.52130505)Zhejiang Provincial Natural Science Foundation of China(Grant No.LD24E050005)+1 种基金Ningbo Key Scientific and Technological Project of China(Grant No.2022Z040)Academic Excellence Foundation of BUAA for PhD Students.
文摘Permanent-magnet(PM)machines are the important driving components of various mechanical equipment and industrial applications,such as robot joints,aerospace equipment,electric vehicles,actuators,wind generators and electric traction systems.The PM machines are usually expected to have high torque/power density,low torque ripple,reduced rotor mass,a large constant power speed range or strong anti-magnetization capability to match different requirements of industrial applications.The structural topology of the electric machines,including stator/rotor arrangements and magnet patterns of rotor,is one major concern to improve their electromagnetic performance.However,systematic reviews of structural topology are seldom found in literature.Therefore,the objective of this paper is to summarize the stator/rotor arrangements and magnet patterns of the permanent-magnet brushless machines,in depth.Specifically,the stator/rotor arrangements of the PM machines including radial-flux,axialflux and emerging hybrid axial-radial flux configurations are presented,and pros and cons of these topologies are discussed regarding their electromagnetic performance.The magnet patterns including various surface-mounted and interior magnet patterns,such as parallel magnetization pole pattern,Halbach arrays,spoke-type designs and their variants are summarized,and the characteristics of those magnet patterns in terms of flux-focusing effect,magnetic self-shielding effect,torque ripple,reluctance torque,magnet utilization ratio,and anti-demagnetization capability are compared.This paper can provide guidance and suggestion for the structure selection and design of PM brushless machines for high-performance industrial applications.
