Torque Coupling Research Articles

Dynamic characteristics and friction torque design method for bogies with friction coupling independently rotating wheelsets

ABSTRACT Friction coupling independently rotating wheelsets have advantages of both rigid wheelsets and independently rotating wheelsets. These wheelsets have self-steering ability on straight lines and large curves. They can also reduce the wear of wheels. The analytical relationship between the friction torque and the lateral displacement of wheelsets was deduced in this study based on motion characteristics of the ideal constraints, including a single wheelset and a friction coupling bogie. Further, the method involving the friction coupling torque with the goal of lateral displacement was presented, and the linear and nonlinear dynamic verification models were established. A linear relationship was found between the friction torque and the lateral displacement of a single wheelset through theoretical analysis and simulation model. When passing a large curve, the front and rear wheelsets in a friction coupling bogie had three states: slip-slip, slip-stick and stick-stick. The proposed method determined the friction torque and accurately controlled the lateral displacement of wheelsets. The dynamic performance of friction coupling bogies was between the performance of a rigid wheelset and that of independently rotating wheelsets, thus effectively relieving the wear of wheel flange.

Control of double gimbal control moment gyro systems using the backstepping control method and a nonlinear disturbance observer

To cancel the negative effects of the friction torques, unmodeled dynamics, and coupling torques, affecting the gimbal precision of a double gimbal control moment gyro (DGCMG) system, this paper proposes a new control architecture to handle these exogenous/endogenous disturbances and to control the two gimbals of the system. It combines a backstepping controller with a nonlinear disturbance observer, which preserve the advantages of the two entities. Firstly, the state space equations of the DGCMG system are established with the friction torques considered exogenous disturbances and unmodeled dynamics regarded as endogenous disturbances. Secondly, a nonlinear observer is used for the estimation of the disturbances. Thirdly, using the observer estimation errors, a backstepping controller is designed to enhance the robustness of the control system, to handle the channel interferences, and to solve the mismatched problem without decoupling between the inner/outer gimbal channels. The obtained control architecture is software implemented and validated; the results show that the proposed control approach not only enhances the robustness in relation to the exogenous/endogenous disturbances, but also improves the angular velocity precision of the two gimbals of the DGCMG system.

Optimization design and performance comparison of different powertrains of electric vehicles

In order to improve the economy of electric vehicles, three dual-motor coupling powertrains are proposed: dual-motor multi-mode coupling powertrain (DMMCP), dual-motor torque coupling powertrain (DMTCP), dual-motor speed coupling powertrain (DMSCP). Among them, DMMCP has two coupling modes of speed and torque, DMTCP can only realize torque coupling, DMSCP can only realize speed coupling. In order to evaluate their performance, they are compared with the traditional single-motor one-speed transmission powertrain (SMOSP) and single-motor two-speed transmission powertrain (SMTSP). The performance of a powertrain is not only related to its topology, but also greatly influenced by the selection of structural parameters. So this paper proposes a method of parameter optimization and optimal performance evaluation, which can obtain the optimal structural parameters while evaluating the performance of a powertrain. The results show that the dual-motor coupling powertrains are better than the traditional single-motor powertrains in the economic performance, and have a broad application prospect.

Coupling synchronization principle of two pairs counter-rotating unbalanced rotors in the different resonant conditions

The present work investigates the coupling synchronization principle and stability in a vibrating system with two pairs counter-rotating unbalanced rotors (also called exciters). Based on Lagrange equations, the dimensionless coupling differential equations of motion of the system are deduced. The synchronization criterion of two pairs exciters stems from the averaging method, it satisfies the fact that the absolute value of dimensionless residual torque difference between arbitrary two driving motors is less than or equal to the maximum of their dimensionless coupling torques. The stability criterion of the synchronous states complies with Routh-Hurwitz principle. The coupling dynamic characteristics of the system are numerically analyzed in detail, including synchronization and stability ability, maximum of the coupling torque and phase relationship, etc. Some simulation results applying the Runge-Kutta algorithm are performed, it is shown that the motion states of the system can be classified into two types: sub-resonant state and super-resonant state. Generally in engineering, the ideal working points should be selected in sub-resonance region, in this case the expended energy can be saved relatively by 1/5–1/3, which is less than that in super-resonance region under the precondition of the same vibration amplitude value.

An Integrated Decoupling Device for Azimuth Control of a Balloon-Borne Gondola

Controlling and maintaining the orientation of the balloon-borne gondola for high-altitude flight is a prerequisite for ensuring the pointing control of observation instruments. When the balloon-borne gondola is flying in the stratosphere of the atmosphere, the existing external interferences will be converted into the coupling moment to the azimuth control system. Meanwhile, those uncertain factors and the frictional nonlinearity of the control system will also cause a certain magnitude of coupling moment. The existence of such coupling moment largely impacts on the accuracy and stability of the orientation control for the angular momentum exchange devices of the balloon-borne gondola. To address such an issue, this paper proposes and implements a novel type of integrated decoupler device. With this decoupler adopted, the aziDmuth control system could sense the existence of coupling torque and azimuth fluctuations quickly and suppress the influences of external interference, uncertain factors, and system structure nonlinearity on the azimuth control effectively, thereby improving the control accuracy of the azimuth control system. Both simulations and experiments are conducted to verify the effectiveness of the proposed device. The results show that the integration of the decoupler and the controller of the azimuth control system provide the azimuth control of the balloon-borne gondola with high accuracy and stability. Such a decoupler device design has a broad potential and could not only be used for balloon-borne gondola control but also could be applied onto other control systems using angular momentum exchange devices as actuators.

Current driven chiral domain wall motions in synthetic antiferromagnets with Co/Rh/Co

Spin–orbit torque that originates from spin Hall effect and Dzyaloshinskii–Moriya interaction (DMI) can efficiently move chiral magnetic domain walls in perpendicularly magnetized wires. It has been shown that antiferromagnetically coupled composite domain walls across a ruthenium layer can be driven even faster by exchange coupling torque that is proportional to exchange coupling strength. Here, we report a current-driven motion of composite chiral domain walls in synthetic antiferromagnets with a rhodium spacer layer. It is found that the domain walls in the wire with a rhodium layer do not move as fast as that with a ruthenium layer although the exchange coupling in Co|Rh|Co is stronger than Co|Ru|Co, which is due to the formation of a large DMI at the Rh|Co interface. The Dzyaloshinskii–Moriya interaction at the Co/Rh interface has the same sign and comparable strength to the Pt|Co interface, thus negating the exchange coupling torque. The spin Hall effect from rhodium is found to be as small as ruthenium. Our findings show that rhodium can be used to tailor the DMI strengths in the current-driven motion of chiral domain walls in various magnetic nanostructures.

A Method for Quantifying Trunk Motor Control During Reaching in Individuals Post Hemiparetic Stroke.

After a hemiparetic stroke, the contralesional upper limb is left with significant motor impairments including: weakness, spasticity, and abnormal joint torque patterns resulting in the flexion synergy (i.e. abnormal coupling between shoulder abduction and elbow/wrist and finger flexion). These impairments, and in particular the flexion synergy, limit ability to reach to the full extent of their limb workspace. Motor control of the trunk is also altered post stroke, with compromised ability to stabilize the trunk and excessive trunk movement during reaching, abnormal isometric torque coupling patterns in the transverse and sagittal planes and weakness. These motor impairments in both trunk and arm limit their ability to perform activities of daily living. While the effect of stroke on reaching has been studied extensively, less is known about the impact of deficits in trunk motor control on reaching ability and the impact of the flexion synergy on trunk postural control. Methods for investigating altered trunk control, specifically during a reach when concurrent loads that elicit the flexion synergy are imposed on the limb and trunk, are limited. Specifically, trunk deficits have yet to be studied in the context of the flexion synergy whereby loads imposed on the arm to elicit shoulder abduction have a negative impact on reaching and potentially on trunk posture. In order to address this gap, we developed a system that integrates a robotic device to simulate varied reaching environments, surface electromyography to measure primary trunk and arm muscle activity, and a two-camera motion capture system that uses reflective markers to measure trunk and arm movement. Feasibility and usability of the system was established during evaluation of reaching ability with varying levels of shoulder abduction loads while the trunk is either restrained or unrestrained in two participants with stroke and a healthy control.Clinical Relevance- The system presented here is capable of monitoring changes in trunk postural control after a hemiparetic stroke during a reaching task as a first step in furthering our understanding of changes in trunk motor control during reaching with the goal of developing more targeted and effective interventions for stroke rehabilitation.

Spin–Orbit Torque and Dipole Coupling for Nanomagnetic Array Programmability

Computational architectures that rely on an array of dipole-coupled nanomagnetic elements require an energy-efficient method of programming individual elements within the array. As a low-energy, selective method of controlling magnetization, spin-orbit torque (SOT) represents a promising solution. Here, a finite-difference micromagnetic model is used to characterize the dipole coupling between adjacent CoFeB nanodisks and to determine the critical SOT current required to switch these disks. Additionally, a phase plot showing disk dimensions at which both vortex and single-domain in-plane magnetic states are stable is produced. A dipole-coupled array's response to dynamic application of SOT current is also simulated. The results show that the rate of applying SOT current to one element in the array strongly influences the stable states of adjacent elements and that the SOT current amplitude required for this influence is an order of magnitude lower than the previously determined critical switching current. This indicates that SOT current dynamics play a significant role in the behavior of a dipole-coupled array. Finally, an architecture to achieve programmability in nanomagnetic computational platforms with SOT is presented.

Review on multi‐power sources dynamic coordinated control of hybrid electric vehicle during driving mode transition process

Aiming at the problem of torque coordinated control between motor with high-frequency response and engine with low-frequency response of hybrid electric vehicle (HEV) during mode transition process, the mechanism of its coordinated control problem is deeply explored, and the essence of dynamic coordinated control strategy (DCCS) through torque coupling analysis is also revealed, namely, motor torque compensation control. Then a series of domestic and international researches on multi-power sources coordinated control are systematically summarized from the establishment of electromechanical transmission (EMT) system model, mode switching process analysis, engine-clutch-motor coordinated control strategy based on torque estimation and speed feedback tracking, as well as the controller robustness analysis under system parameter perturbation and external disturbance. Finally, the key issues on the rapidity, adaptability, and experiment of torque coordination control which need to be solved in the subsequent researches are pointed out clearly.

Representation, generation, and optimization methodology of hybrid electric vehicle powertrain architectures

Since the first commercial application of hybrid electric vehicle (HEV) powertrains, power-split architectures have been a major option for construction of HEV powertrains. Are power-split HEV powertrains the best solution to all design-objective settings, or will other design schemes arise that better fit the design requirements? To generalize the system optimization to different types of HEV powertrains, representation and generation methods for generic architectures of HEV powertrain are developed, which completely clarify the available design domain of the HEV powertrain architecture. Then, an integrated multi-objective optimization that simultaneously optimizes the architecture, component parameters, and control strategy is engineered to obtain the Pareto optimal design schemes of HEV powertrains in various situations of trade-off between acceleration capacity and fuel economy. The results suggest that the power-split HEV powertrain is superior in fuel economy and the HEV powertrain adopting the architecture with torque coupling among the engine and motor/generators (1-1 type) is superior in acceleration capacity. However, the achievable optimal fuel economies of power-split and 1-1 type HEV powertrains are almost the same, whereas the trade-off ranges of power-split HEV powertrains are narrower than those of the 1-1 type architecture HEV powertrains. Conceptually, the results reflect that when design methods are restricted to a specific subspace of the design domain, due to the limited consideration of variation in HEV powertrain architectures, the theoretical optimality of the design is not guaranteed. Practically, 1-1 type architecture can be more adaptive to different trade-offs among design objectives. For variations in design objectives, the appropriate HEV powertrain can be constructed by modifying in component parameters of the 1-1 No. 5 architecture HEV powertrain rather than reconstruction of the powertrain with architectural modifications.

Torque and rotational speed sensor based on resistance and capacitive grating for rotational shaft of mechanical systems

Torque and rotational speed are important parameters to characterize the power of rotating parts for mechanical systems, so a rotational shaft’s torque and rotational speed sensing method and real-time signal processing are key technologies for mechanized equipment, such as vehicles, ships, etc. Hence an advanced torque and speed sensing technology and a data processing technology are very important for improving the performance of mechanical equipment. However, the power transmission device’s rotational shaft has a compact structure and narrow space, so it is difficult to install a signal transmission and power supply device of a sensor on the rotational shaft. To solve these difficult problems, this paper proposes a rotational shaft torque and rotational speed measurement method coupling resistance and capacitance. This method uses two resistance strain gauges and a capacitive grating, and the capacitive grating transmits signals in a non-contact coupling manner. The sensor on the rotational shaft needs no power supply and the signals are transmitted to a measurement circuit from a stationary sleeve, so this method essentially solves the difficult problems in signal transmission and power supply. Simulation and measurement experiments show that the resistance strain gauges obtain information and the capacitive grating sensor transfers information. The method coupling resistance and capacitance for realizing information sensing is feasible, which is suitable for measuring the torque and rotational speed of the rotational shaft of mechanical equipment in spite of the compact structure and narrow space.

Analysis of coupled motion constraints and coupling errors for a six-axis magnetic levitation stage

This paper presents the coupled motion constraints and coupling errors analysis of a magnetic levitation stage, which are two aspects of the coupling characteristics of magnetic levitation stage caused by force coupling. Aiming at the motion constraint coupling problem, this paper proposes a motion constrain method based on the force distribution matrix of the magnetic levitation stage. By this method, the motion constraint intervals without input saturation for single-degree-of-freedom motion, in-plane motion, and out-of-plane motion of magnetic levitation stage are established. When used for motion control, these constraints can provide the motion constraint specifications for the magnetic levitation stage, avoid the input saturation problem caused by the actuation force coupling, and provide a theoretical basis for magnetic levitation stage trajectory planning. Aiming at reducing the coupling error, this paper proposes a strategy to evaluate the coupling degree of the magnetic levitation stage actuation force by the condition number of the actuation force transfer matrix and the singular value of the force and torque error matrix. On this basis, the force and torque coupling errors caused by the translational and rotational movements of the magnetic levitation stage are studied, and the mechanism and characteristics of the coupling error between the interaction of translational and rotational movements are revealed. Based on the obtained results, the decoupling algorithm of the magnetic levitation stage is designed. Experimental results of the normalized step response demonstrate that the linearity of the magnetic levitation stage will be destroyed by the current saturation, and coupling error can also be introduced. Therefore, it is necessary to study the motion constrain strategy to provide comprehensive criteria for the trajectory planning and controller design. Experimental results of six-axis coupling error analysis show that the coupling error of x- and y-axes translational movement is reduced by 69.34% and 69.60%, respectively. This method provides a theoretical basis for the decoupling of the magnetic levitation stage and reducing the coupling error.

Haptic-Guided Teleoperation of a 7-DoF Collaborative Robot Arm With an Identical Twin Master.

In this article, we describe two techniques to enable haptic-guided teleoperation using 7-DoF cobot arms as master and slave devices. A shortcoming of using cobots as master-slave systems is the lack of force feedback at the master side. However, recent developments in cobot technologies have brought in affordable, flexible, and safe torque-controlled robot arms, which can be programmed to generate force feedback to mimic the operation of a haptic device. In this article, we use two Franka Emika Panda robot arms as a twin master-slave system to enable haptic-guided teleoperation. We propose a two layer mechanism to implement force feedback due to 1) object interactions in the slave workspace, and 2) virtual forces, e.g. those that can repel from static obstacles in the remote environment or provide task-related guidance forces. We present two different approaches for force rendering and conduct an experimental study to evaluate the performance and usability of these approaches in comparison to teleoperation without haptic guidance. Our results indicate that the proposed joint torque coupling method for rendering task forces improves energy requirements during haptic guided telemanipulation, providing realistic force feedback by accurately matching the slave torque readings at the master side.

Gimbal torque and coupling torque of six degrees of freedom magnetically suspended yaw gimbal

When the three-axis intertially stabilized platform (ISP) realizes the fast response of yaw gimbal, coupling torques among three gimbals cause negative influence on the attitude stabilization precision of yaw gimbal which supports the imaging payloads. Therefore, the gimbal torque of six degrees of freedom (DOFs) yaw gimbal with the magnetic suspension system is used to compensate coupling toques acting on it in this article. The dynamics models of yaw gimbal and three-axis ISP are developed, and then coupling torques among three gimbals are analyzed, it varies with motion states of the base plate. Moreover, the characteristics about gimbal torque generated by the magnetic suspension system are studied, it can accurately track the control input of magnetic suspension system. Finally, experimental results indicate that the gimbal torque of magnetic suspension system can effectively compensate coupling torques acting on the yaw gimbal, so the attitude stabilization precision of yaw gimbal is improved.

Spin transfer torque and exchange coupling in Josephson junctions with ferromagnetic superconductor reservoirs

In this paper, the spin transfer torque (STT) and the exchange coupling of the Josephson junctions containing the interesting cases of diffusive/ballistic-triplet/singlet ferromagnetic superconductor (FS) materials are investigated. First, the diffusive FS1/Fc/FS2 structures with Fc being a junction consisting of ferromagnetic and normal metal parts as well as insulating barriers are investigated. Secondly, the ballistic Josephson junction containing the triplet chiral p/wave FS reservoirs is studied. Using the Nazarov quantum circuit theory for the diffusive structures, it is found that the antiparallel/parallel or vice versa parallel/antiparallel transition of the favorable exchange coupling takes place due to the appearance of the only out-of-plane STT. Furthermore, the analyze of the phase difference interval in which an interlayer length-induced antiparallel/parallel transition can be occurred, is performed. Afterward, the mentioned ballistic structure is dealt with solving the 16 16 Bogoliubov–de-Gennes equation. It is found that although the exchange fields of the FS are laid in the z and y direction, the STT interestingly exists in all three directions of x, y and z. This exciting finding suggests that the favorable equilibrium configuration concerning the least exchange coupling occurs in the relative exchange field direction different from 0 or .

Comments on the stability of the synchronous states of three vibrators in a vibrating system with two rigid frames

This paper focuses on the stability of three homodromy vibrators in a vibrating system with two rigid frames (RFs). The motion differential equations of the system are established. Using the average method yields the average coupling torque balanced equations of three vibrators, and the simplified analytical expressions for synchronization and stability criterions of the system were derived. The coupling dynamic characteristics were numerically analyzed, including frequency-amplitude response, stable phase differences, synchronization and stability ability, and phase relationships. The simulations to verify the validity of theoretical results were carried out. It is shown that the stable states of the system are classified into three types, thereof the stability of phase differences among vibrators is similar in sub-resonant and super-resonant states, which results in no vibration of the system. While in near sub-resonant state the system reflects strong useful positive superposition vibration with energy saving, which is exactly the desire in engineering design.

Analysis of the Results of Stabiolmetric Tests with a Stepwise Input Action in the Context of the Mechanics of Controlled Systems

Abstract—Problems of optimal control were analyzed for a human motion model for stabilometric tests where the posture changes under a stepwise input action. The presence of a prominent “swing” and an “overshoot” are characteristic of the center-of-pressure trajectories recorded in the test. A one-dimensional inverted pendulum model was used in the study. The solution of the optimal control for the inverted pendulum motion controlled by coupling torque was put in correspondence with the test results. The problems of optimal speed-of-response control and linear–quadratic regulator were considered. The solution of these optimum problems was compared with the stabilometric test results. A modified algorithm was proposed for stabilometric data processing. This motion was shown to reach a stable motor pattern. The swing and overshoot were found to correspond to the acceleration and deceleration stages, respectively.

Electromagnetic Hysteresis Based Dynamics Model of an Electromagnetically Controlled Torque Coupling

This paper proposes a novel computationally efficient, easy-to-implement electromagnetic hysteresis based dynamics model of a kind of intelligent electromagnetic torque controlled coupling (EMTC), which, with drag torque under consideration, first models the electromagnetic hysteresis existing in the primary clutch with the classical Preisach model, and then models the transferred torques in the three friction elements of the center coupling in the slipping and locked modes, respectively. The performance of the model is verified by simulation and experiment jointly, which lays the basis for the development of advanced control algorithm.

Reassessment of electromagnetic core-mantle coupling and its implications to the Earth's decadal polar motion

The observed Earth's polar motion on decadal time scales has long been conjectured to be excited by the exchange of equatorial angular momentum between the solid mantle and the fluid outer core, via the mechanism of electromagnetic (EM) core-mantle coupling. However, past estimations of the EM coupling torque from surface geomagnetic observations is too weak to account for the observed decadal polar motion. Our recent estimations from numerical geodynamo simulations have shown the opposite. In this paper, we re-examine in detail the EM coupling mechanism and the properties of the magnetic field in the electrically conducting lower mantle (characterized by a thin D″-layer at the base of the mantle). Our simulations find that the toroidal field in the D″-layer from the induction and convection of the toroidal field in the outer core could be potentially much stronger than that from the advection of the poloidal field in the outer core. The former, however, cannot be inferred from geomagnetic observations at the Earth's surface, and is missing in previous EM torque estimated from geomagnetic observations. Our deduction suggests further that this field could make the actual EM coupling torque sufficiently strong, at approximately 5 × 1019 Nm, to excite, and hence explain, the decadal polar motion to magnitude of approximately 10 mas.

A Method to Quantify Multi-Degree-of-Freedom Lower Limb Isometric Joint Torques in Children with Hemiplegia.

Pediatric hemiplegia, caused by a unilateral brain injury during childhood, can lead to motor deficits such as weakness and abnormal joint torque coupling patterns which may result in a loss of independent joint control. It is hypothesized that these motor impairments are present in the paretic lower extremity, especially at the hip joint where extension may be abnormally coupled with adduction. Previous studies investigating lower extremity isometric joint torques in children with spastic cerebral palsy used tools that limited data collection to one degree of freedom, making it impossible to quantify these coupling patterns. We describe the adaptation of a multi-joint lower extremity isometric torque measurement device to allow for quantification of weakness and abnormal joint torque coupling patterns at the hip in the pediatric population. We also present preliminary data in three children without hemiplegia to highlight how the presence of atypical femoral bony geometry, often observed in childhood hemiplegia, can be accounted for in the Jacobian transformations and affect joint torque measurements at the hip.