Torque Coupling Research Articles

Synchronous Stability of Four Homodromy Vibrators in a Vibrating System with Double Resonant Types

This paper aims at studying the synchronous stability of four homodromy vibrators in subresonant and superresonant states. The motion differential equations are established firstly. The simplified form of analytical expressions is yielded, and the stability criterion of synchronous states satisfies Routh–Hurwitz criterion. The coupling dynamic characteristics of the system are analyzed in detail numerically, such as the maximum of coupling torque, coefficients of ability of synchronization and stability, and phase differences. Based on the ratio of operating frequencies to natural frequencies of the system, the resonant regions are divided into two areas: subresonant and superresonant. It is shown that the phase differences among four vibrators in the subresonant state are stabilized about zero, and exciting forces of four vibrators are positively superposed, while in the superresonant one, the phenomenon of the diversity of the nonlinear system occurs, i.e., two groups of synchronous and stable solutions of the phase differences (pi and pi/2) are found, and in this case, the exciting forces of four vibrators are counteracted, the rigid frame embodies no vibration, and the minimum of dynamic load transferring to foundation is realized. The correctness of theoretical results is verified by numerical characteristic analysis and simulations. This paper can provide a theoretical reference for designing a type of new high‐frequency vibrating mill.

Efficient piecewise-affine coupled-system feed-forward control of a nonlinear elastomer coupling

For a simplified elastic drive train with nonlinear coupling torque, this paper proposes an efficient model of the coupled system model in time-discrete form. It is obtained from piecewise-exact discretization of the continuous-time system model and allows precise, efficient feed-forward control in real time. The high model accuracy is validated in a hardware-in-the-loop setting on a laboratory test rig for elastomer couplings. The model-based control law allows safe operation of the test rig across the system’s resonance range.

Dynamic Characteristics of Magnetic Coupling in Horizontal Axis Wave Energy Device

Abstract To solve the dynamic response problems of magnetic coupling in the horizontal axis wave energy device, this has researched the dynamic characteristicsof magnetic coupling. The fitting formula about torque and angle of the magnetic coupling is obtained through experiments. The mathematical models of the magnetic coupling torque transmission are established. The steady state error of the magnetic coupling and the transfer function of the output angle are obtained. The analytical solution of the step response of the output angle in time domain is derived. The influence of the torsional rigidity, the damping coefficient and the driven rotor’s rotational inertia on dynamic characteristics of the magnetic coupling isanalyzed. According to the analysis results, the design rules of magnetic coupling are proposed.

Influence of controllable parameters on load sharing behavior of torque coupling gear set

The multi-motor torque coupling system couples the power of multiple motors by using torque coupling gear sets. The torque coupling gear set is a fixed-axis gear train consisting of multiple input pinions and one output gear. The load carrying capacity and service life of the gear set is affected by the load sharing behavior. A dynamic model of the multi-motor torque coupling system is established. Under the constant load, step load, and variable speed conditions, the influence of the pinion speed synchronization error and drive torque synchronization error on the load sharing behavior of the torque coupling gear set is studied. The results indicate that under these three conditions, the load sharing behavior gets worse with the increase of the pinion speed synchronization error or drive torque synchronization error; the pinion speed synchronization error has a more significant effect on the load sharing behavior. The two synchronization errors can be reduced by controlling multiple inputs of the gear set, and thus, the load sharing behavior can be improved.

Electromagnetic Torque Performance Analysis of a Parallel Hybrid Excitation Machine With Axial Paralleling of Permanent Magnet Part and Variable Reluctance Part

In this paper, the electromagnetic torque (EM) performance analysis of a parallel hybrid excitation machine (PHEM) is investigated. It is composed of a permanent magnet (PM) part and variable reluctance part. The flux paths of the two parts are independent and the armature windings are connected in series. PHEM is an axial parallel coupling of two different types of brushless machine. The mechanisms of EM torque for the two parts are quite different and many problems of torque coupling still remain unsolved. A 2-D EM-circuit coupling simulation model is built to analyze the torque characteristics and coupling relationships. The simulation results indicate that the PM part plays a main role in the output torque of PHEM. The large inductance ripple of variable reluctance part would cause large torque ripple in PHEM. The target machine is experimentally tested to verify the output torque characteristics. Furthermore, the torque-angle characteristics are studied with different field current and it shows that the best load angle could be around 110° to get maximum output torque and relatively smaller torque ripple.

Is Magnus effect relevant for proppant settling in narrow fractures?

Resolved Computational Fluid Dynamics-Discrete Element Method is an attractive approach for simulating multiphase flows of fluid-solid mixtures, as it includes a 4-way coupling. However, many of its modernimplementations neglect the torque coupling between the fractions. Here we augment the CFDEM®coupling toolkit to allow it to capture this interaction and use it to simulate sedimentation of spherical grains in two-dimensional narrow fractures, with and without grain rotation taken into account. While the rotational effects turns out to change the dynamics of individual grains, it does not affect the average settling velocity significantly.

Lower Extremity Motor Impairments in Ambulatory Chronic Hemiparetic Stroke: Evidence for Lower Extremity Weakness and Abnormal Muscle and Joint Torque Coupling Patterns

Although global movement abnormalities in the lower extremity poststroke have been studied, the expression of specific motor impairments such as weakness and abnormal muscle and joint torque coupling patterns have received less attention. We characterized changes in strength, muscle coactivation and associated joint torque couples in the paretic and nonparetic extremity of 15 participants with chronic poststroke hemiparesis (age 59.6 ± 15.2 years) compared with 8 age-matched controls. Participants performed isometric maximum torques in hip abduction, adduction, flexion and extension, knee flexion and extension, ankle dorsi- and plantarflexion and submaximal torques in hip extension and ankle plantarflexion. Surface electromyograms (EMGs) of 10 lower extremity muscles were measured. Relative weakness (paretic extremity compared with the nonparetic extremity) was measured in poststroke participants. Differences in EMGs and joint torques associated with maximum voluntary torques were tested using linear mixed effects models. Results indicate significant poststroke torque weakness in all degrees of freedom except hip extension and adduction, adductor coactivation during extensor tasks, in addition to synergistic muscle coactivation patterns. This was more pronounced in the paretic extremity compared with the nonparetic extremity and with controls. Results also indicated significant interjoint torque couples during maximum and submaximal hip extension in both extremities of poststroke participants and in controls only during maximal hip extension. Additionally, significant interjoint torque couples were identified only in the paretic extremity during ankle plantarflexion. A better understanding of these motor impairments is expected to lead to more effective interventions for poststroke gait and posture.

Precise Control for Gimbal System of Double Gimbal Control Moment Gyro Based on Cascade Extended State Observer

Coupling torque, nonlinear friction, and unmodeled dynamics are the main constraints that influence the angular speed precision of the gimbal systems in double gimbal control moment gyros (DGCMGs). This paper explores a novel angular speed tracking control method based on the cascade extended state observer (CESO). The coupling torque, nonlinear friction, and unmodeled dynamics are considered as the system's lumped disturbance, which is estimated by the designed CESO. By introducing a state feedback controller, the disturbances can be eliminated from the output channel of the system. Both simulation and experimental results confirmed the feasibility and effectiveness of the proposed method.

A Novel Model of Magnetic Eddy-current Coupling Based on the Magnetic Equivalent Circuit Method

Nowadays, magnetic eddy-current couplings have been widely used in medium and high power electric motors. During the development of initial or optimum design of magnetic eddy-current couplings, it has been more and more essential to build a model with accurate and time-saving features the magnetic equivalent circuit method (MEC) has been used in this paper to build the static magnetic circuit model while the Ampere theorem has been applied to develop the dynamic magnetic model. Finally, analytical expressions of coupling torque are obtained and validity of the novel model has been verified by three-dimension finiteelement simulation.

Spin-orbit torque in MgO/CoFeB/Ta/CoFeB/MgO symmetric structure with interlayer antiferromagnetic coupling

Spin current generated by spin Hall effect in the heavy metal would diffuse up and down to adjacent ferromagnetic layers and exert torque on their magnetization, called spin-orbit torque. Antiferromagnetically coupled trilayers, namely the so-called synthetic antiferromagnets (SAF), are usually employed to serve as the pinned layer of spintronic devices based on spin valves and magnetic tunnel junctions to reduce the stray field and/or increase the pinning field. Here we investigate the spin-orbit torque in MgO/CoFeB/Ta/CoFeB/MgO perpendicularly magnetized multilayer with interlayer antiferromagnetic coupling. It is found that the magnetization of two CoFeB layers can be switched between two antiparallel states simultaneously. This observation is replicated by the theoretical calculations by solving Stoner-Wohlfarth model and Landau-Lifshitz-Gilbert equation. Our findings combine spin-orbit torque and interlayer coupling, which might advance the magnetic memories with low stray field and low power consumption.

Dynamic coupling of ferromagnets via spin Hall magnetoresistance

The synchronized magnetization dynamics in ferromagnets on a nonmagnetic heavy metal caused by the spin Hall effect is investigated theoretically. The direct and inverse spin Hall effects near the ferromagnetic/nonmagnetic interface generate longitudinal and transverse electric currents. The phenomenon is known as the spin Hall magnetoresistance effect, whose magnitude depends on the magnetization direction in the ferromagnet due to the spin transfer effect. When another ferromagnet is placed onto the same nonmagnet, these currents are again converted to the spin current by the spin Hall effect and excite the spin torque to this additional ferromagnet, resulting in the excitation of the coupled motions of the magnetizations. The in-phase or antiphase synchronization of the magnetization oscillations, depending on the value of the Gilbert damping constant and the field-like torque strength, is found in the transverse geometry by solving the Landau-Lifshitz-Gilbert equation numerically. On the other hand, in addition to these synchronizations, the synchronization having a phase difference of a quarter of a period is also found in the longitudinal geometry. The analytical theory clarifying the relation among the current, frequency, and phase difference is also developed, where it is shown that the phase differences observed in the numerical simulations correspond to that giving the fixed points of the energy supplied by the coupling torque.

Magnetically controlled ferromagnetic swimmers

Microscopic swimming devices hold promise for radically new applications in lab-on-a-chip and microfluidic technology, diagnostics and drug delivery etc. In this paper, we demonstrate the experimental verification of a new class of autonomous ferromagnetic swimming devices, actuated and controlled solely by an oscillating magnetic field. These devices are based on a pair of interacting ferromagnetic particles of different size and different anisotropic properties joined by an elastic link and actuated by an external time-dependent magnetic field. The net motion is generated through a combination of dipolar interparticle gradient forces, time-dependent torque and hydrodynamic coupling. We investigate the dynamic performance of a prototype (3.6 mm) of the ferromagnetic swimmer in fluids of different viscosity as a function of the external field parameters (frequency and amplitude) and demonstrate stable propulsion over a wide range of Reynolds numbers. We show that the direction of swimming has a dependence on both the frequency and amplitude of the applied external magnetic field, resulting in robust control over the speed and direction of propulsion. This paves the way to fabricating microscale devices for a variety of technological applications requiring reliable actuation and high degree of control.

Active coupling suppression and real-time control system design and implementation for three-axis electronic flight motion simulator

Modelling of a three-axis electronic flight motion simulator with U-O-O structure is achieved in this paper, based on recursive Newton–Euler equations. To overcome the shortcomings of passive decoupling control methods, an active coupling torque suppression method is proposed using velocity internal feedback by analysing the influence of the coupling torque. Detailed control software and hardware implementation is given for the real-time control system. Experimental tests show the designed flight motion simulator system performs good dynamic and static performances.

Command Filter Backstepping Sliding Model Control for Lower-Limb Exoskeleton

A command filter adaptive fuzzy backstepping control strategy is proposed for lower-limb assisting exoskeleton. Firstly, the human-robot model is established by taking the human body as a passive part, and a coupling torque is introduced to describe the interaction between the exoskeleton and human leg. Then, Vicon motion capture system is employed to obtain the reference trajectory. For the purpose of obviating the “explosion of complexity” in conventional backstepping, a second-order command filter is introduced into the sliding mode control strategy. The fuzzy logic systems (FLSs) are also applied to handle with the chattering problem by estimating the uncertainties and disturbances. Furthermore, the stability of the closed-loop system is proved based on the Lyapunov theory. Finally, simulation results are presented to illustrate the effectiveness of the control strategy.

Time-resolved X-ray detected ferromagnetic resonance of spin currents

X-ray detected ferromagnetic resonance (XFMR) has recently emerged as a powerful synchrotron-radiation-based tool able to study the element-selective magnetization dynamics. Magnetic and chemical contrast in XFMR is obtained by X-ray magnetic circular dichroism (XMCD), while the phase difference between the magnetization precessions is monitored using stroboscopic probing. A unique property of time-resolved XFMR is the visualization of the magnetization precession for each individual layer in a magnetic device. Measurement of the amplitude and phase response of the magnetic layers gives a clear signature of spin-transfer torque (STT) coupling between ferromagnetic layers due to spin pumping.

Study on Torque Calculation for Hybrid Magnetic Coupling and Influencing Factor Analysis

Specific to a problem that the present transmission of magnetic coupling torque was subjected to restrictions of its own structure, a hybrid magnetic coupling was proposed. Then, finite element method was adopted to carry out numerical calculations for its three-dimensional magnetic field to obtain three-dimensional magnetic field distribution of radial and axial configurations. Major influencing factors of its torque, such as lengths of axial and radial air gaps, thicknesses of axial and radial permanent magnets, the number of slots in axial copper rotor, thickness of axial and radial copper rotor, etc., were analyzed. The relevant results indicated that in certain conditions of shapes, ten magnetic poles of the axial permanent magnet rotor, nine of the radial permanent magnet rotor and nine slots from the axial copper rotor were used. Correspondingly, the axial copper rotor had a thickness of 20 mm and it was 5 mm for the radial copper rotor. Moreover, the maximum torque could reach 190 N.m approximately. If lengths of axial and radial air gaps increased, the torque may go down otherwise. Within a certain scope, the torque rose in the first place and then fell with increases in the permanent magnet thickness of axial permanent magnetic rotor, the number of axial and radial magnetic poles, the number of slots in axial copper rotor, and the thickness of axial copper rotor. Additionally, the number of slots in the axial copper rotor could not be equivalent to that of magnetic poles in axial permanent magnetic rotor. However, as the permanent magnet thickness of radial permanent magnetic rotor rose, the torque went up as well.

Influence of motor control characteristics on load sharing behavior of torque coupling gear set

The influence of the control characteristics of a direct torque control (DTC) motor on the load sharing behavior of a torque coupling gear set is studied by establishing a dynamic model of a multi-motor torque coupling system. The effects of run-out errors of the pinions of the torque coupling gear set on the powertrain are analyzed under steady operating conditions. The difference in rotational speed among the pinions becomes apparent, and the load sharing behavior deteriorates when there are run-out errors. The relationship between the control characteristics and load sharing behavior is studied. The difference in rotational speed decreases and the load sharing behavior improves as proportional and integral gains of the speed controller increase.

The disturbance rejection of magnetically suspended inertially stabilized platform

In a magnetically suspended inertially stabilized platform, the yaw gimbal is suspended by the magnetic bearing, which can effectively isolate the external vibrations and disturbances. However, coupling torques and disturbance torques among gimbals still exist. Therefore, based on the cross feedback compensation, the output angles of gimbals are introduced as feedback variables, and the inverse coordinate transformation matrix is designed to compensate for the coupling torques. Furthermore, a disturbance observer is applied to inhibit the disturbance torque and simulations indicate that the disturbance observer can accurately estimate the disturbance torque. Consequently, the experimental results demonstrate that the cross feedback compensation can inhabit the coupling torques, and the disturbance observer greatly suppresses the external disturbance torques and improves the angular displacement precision of gimbals.

Current induced domain wall motion in antiferromagnetically coupled (Co70Fe30/Pd) multilayer nanowires

We investigate the current induced domain wall (DW) motion in the ultrathin CoFe/Pd multilayer based synthetically antiferromagnetic (SAF) structure nanowires by anomalous Hall effect measurement. The threshold current density (Jth) for the DW displacement decreases and the DW velocity (v) increases accordingly with the exchange coupling Jex between the top and bottom ferromagnetic CoFe/Pd multilayers. The lowest Jth = 9.3 × 1010 A/m2 and a maximum v = 150 m/s with J = 1.5 × 1012 A/m2 are achieved due to the exchange coupling torque (ECT) generated in the SAF structure. The strength of ECT is dependent on both of Jex and the strong spin-orbit torque mainly generated by Ta layer.

Effects of Prolonged Running-Induced Fatigue on the Periodicity of Shank-Foot Segment Coupling and Free Torque

Objective: The purpose of this study was to determine the periodicity of shank-foot segment coupling and free torque before and after fatigue induced by prolonged running. Method: Fifteen young healthy male participants with a rear-foot strike ran on instrumented dual-belt treadmills at 70% of their maximum oxygen uptake for 65 min. Kinematic and ground reaction force data were collected for 20 continuous strides at 5 and 65 min (considered the fatigued condition). The approximate entropy tool was applied to assess the periodicity of the shank internal-external rotation, foot inversion-eversion, shank-foot segment coupling, and free torque for the two running conditions. Results: The periodicity of all studied parameters, except foot inversion-eversion, decreased after 65 min of running (fatigued condition) for 80% of the participants in this study. Furthermore, 60% of the participants showed similarities in the change of periodicity pattern in shank internal-external rotation, coupling, and free torque. Conclusion: The findings indicated that the foot inversion-eversion motion may pose a higher risk of injury than the shank internal-external rotation, coupling, and free torque in the fatigued condition during prolonged running.