Large Torque Research Articles

A Novel Step Current Excitation Control Method to Reduce the Torque Ripple of Outer-Rotor Switched Reluctance Motors

Featured in low-speed and high-torque operation, outer-rotor switched reluctance motors (OSRMs) have the potential to be widely deployed in low-speed commuter and logistics vehicle applications. In this paper, a five-phase OSRM and the control method featuring torque ripple reduction has been proposed, which can be applied as the wheel hub motor in the electric vehicles. The simulation was carried out to analyze the OSRM operation. The electromagnetic characteristics of single-phase and two-phase hybrid excitation mode, as well as step current excitation mode, were compared and analyzed. To solve the problem of the large torque ripple of OSRMs under traditional excitation modes, the torque ripple suppression method based on step current excitation was also studied. The experiment design, including motor start-up control, speed control, and torque ripple reduction, are presented to verify the system torque ripple mitigation method.

Research on Speed Regulation performance of switched reluctance Motor based on nonlinear active disturbance rejection

Abstract The state has vigorously advocated new energy electric vehicles in recent years. Compared with other motors, switched reluctance motor has the advantages of superior speed regulation performance, low production cost and strong controllability. However, due to its double salient structure, it is easy to produce magnetic circuit saturation, and its control is non-linear, which is easy to lead to large torque ripple and strong noise. To solve this problem, a control strategy combining active disturbance rejection control and direct torque is proposed to suppress torque ripple. A simulation model is built and calculated with simulation software. At the same time, it is compared with PI control and fuzzy PID control under direct torque control. Finally, the simulation experiment is carried out on a 6 / 4 motor. The simulation results also show that the direct torque control strategy based on active disturbance rejection control technology can effectively control the torque and speed of switched reluctance motor.

Efficient orbital torque in polycrystalline ferromagnetic−metal/Ru/Al2O3 stacks: Theory and experiment

Recently emergent current-induced orbital torque is considered more effective for magnetization switching than the well-established spin-orbit torque. However, long-range orbital transport in polycrystalline films and the theory on orbital transport in polycrystalline heterostructures remain elusive. Here we report a large torque effect in $\mathrm{CoFeB}/\mathrm{Ru}/{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ polycrystalline stacks. The unfilled $d$-shell and small spin-orbit coupling in Ru provide an ideal platform for orbital generation and transport. The orbital current from the $\mathrm{Ru}/\mathrm{A}{\mathrm{l}}_{2}{\mathrm{O}}_{3}$ interface can go through a thick Ru layer, with a peak value at 7-nm-thick Ru, and then induces a strong torque effect in CoFeB. The torque efficiency increases unprecedentedly with increasing CoFeB layer thickness, leveling off at $\ensuremath{\sim}0.3$ for 12-nm-thick CoFeB. Theoretical analysis shows that the orbital transport in polycrystalline materials exhibits a unique random precession behavior, leading to a more efficient orbital transport than that in single crystals. Besides the fundamental significance, our findings advance the development of practical orbital torque devices.

Mechanical Analysis of DS in Horizontal Directional Drilling

In recent years, trenchless horizontal directional drilling (HDD) technology has developed rapidly towards the direction of large pipe diameter and long span. During construction, the buckling deformation and large drag torque of the drillstring (DS) are the key problems restricting the development of the HDD technology. In order to understand the buckling deformation law of the DS in horizontal directional drilling engineering, as well as the transfer and the distribution of the drag torque, and the relationship between the buckling deformation and drag torque, the dynamic model of the DS system in drilling engineering is applied to HDD engineering. The dynamics model of HDD at a long distance (5200 m) is established and calculated. The research indicates (1) when the buckling deformation of the DS is small, priority should be given to reducing the friction and torsion at the bending position; (2) excessive inlet thrust is the main reason for the buckling deformation of the DS, and the smaller the hole diameter, the more serious the buckling deformation; (3) severe buckling deformation of the DS will lead to an increase in the frictional resistance at the deformed part, and even local self-locking, resulting in the inability to continue to increase the weight on bit (WOB). The research results preliminarily reveal the relationship between DS buckling deformation and drag torque in ultra-long distance HDD engineering and point out the phenomenon law of drag torque and buckling deformation, which has reference value for the development of HDD technology.

Fuzzy-based estimation of reference flux, reference torque and sector rotation for performance improvement of DTC-IM drive

In this study, the fuzzy-based reference flux estimator (RFE), reference torque estimator (RTE) and sector rotation strategy called fuzzy logic estimator are proposed to direct torque control of induction motor (DTC-IM) drive for performance improvement. The basic DTC-IM drive with conventional RFE, RTE and sector division causes large torque ripple, variable switching frequency and uneven voltage vector contribution in stator flux. The torque and speed responses of the proposed system are investigated with load variations. The simulation results of the proposed DTC-IM drive are compared with the basic DTC-IM drive. The assessment of the proposed system shows improved performance. A hardware is developed using Xilinx Spartan-6XC6SLX45-Field Programmable Gate Array (FPGA) Kit for experimental verification of the results. Moreover, sinusoidal pulse width modulation and space vector pulse width modulation techniques are applied to reduce the torque ripples. The performance of the drive is investigated for various speed ranges. The comparison of the simulated and experimental results proves that the proposed fuzzy-based DTC-IM drive provides better performance than the basic DTC-IM drive.

Analysis of electromagnetic performance of differential multi-stage coaxial magnetic gears with large gear ratio and high torque density applied to high-power wind turbines

Magnetic gear is a non-contact transmission mechanism, which overcomes the drawback of mechanical gear transmission. Although the series multi-stage magnetic gear can provide a large gear ratio compared to the single-stage magnetic gear, the lower torque density of the series multi-stage magnetic gear limits its use in high-power wind turbines. According to the magnetic gear field modulation mechanism and the differential transmission method, a differential multi-stage coaxial magnetic gear transmission device is proposed, which can achieve transmission with a large gear ratio and large torque density. Based on the differential multi-stage coaxial magnetic gear structure and its working principle, the finite element method is used to simulate the electromagnetic performance of the multi-stage coaxial magnetic gear. Futhermore, the electromagnetic performance of the two stages of the proposed magnetic gear are compared. The results show that there is a significant difference between the the electromagnetic performance of the first stage and that of the second stage. The torque ripple of the first stage is more dramatic than that of the second stage. The torque ripple amplietude of the inner rotor of the first stage is 5.08‰ larger than that of the second stage. The torque ripple amplietude of the outer rotor of the first stage is 4.591‰ larger than that of the second stage.

Gyrotactic cluster formation of bottom-heavy squirmers

Squirmers that are bottom-heavy experience a torque that aligns them along the vertical so that they swim upwards. In a suspension of many squirmers, they also interact hydrodynamically via flow fields that are initiated by their swimming motion and by gravity. Swimming under the combined action of flow field vorticity and gravitational torque is called gyrotaxis. Using the method of multi-particle collision dynamics, we perform hydrodynamic simulations of a many-squirmer system floating above the bottom surface. Due to gyrotaxis they exhibit pronounced cluster formation with increasing gravitational torque. The clusters are more volatile at low values but compactify to smaller clusters at larger torques. The mean distance between clusters is mainly controlled by the gravitational torque and not the global density. Furthermore, we observe that neutral squirmers form clusters more easily, whereas pullers require larger gravitational torques due to their additional force-dipole flow fields. We do not observe clustering for pusher squirmers. Adding a rotlet dipole to the squirmer flow field induces swirling clusters. At high gravitational strengths, the hydrodynamic interactions with the no-slip boundary create an additional vertical alignment for neutral squirmers, which also supports cluster formation.

Influence of Rotor Eccentricity On Electromagnetic Performance of 2-pole/3-slot PM Motors

This paper investigates the influence of static and dynamic rotor eccentricities on electromagnetic performance, including air-gap flux density, back electromotive force (EMF), electromagnetic torque, cogging torque, and unbalanced magnetic force (UMF), of a 2-pole/3-slot permanent magnet (PM) motor considering eccentricity ratio, eccentricity angle, and rotor initial angle. Both finite element analyses and experiments show that in a 2-pole/3-slot PM motor, the static rotor eccentricity leads to unbalanced magnitudes and phase angles of fundamental back-EMFs of three phases but does not change the harmonic contents, while the dynamic rotor eccentricity will not cause unbalance in three phase back-EMFs but affects the harmonic contents of back-EMFs and their phase angles, which causes asymmetric positive and negative half-periods and corresponding even harmonics of phase back-EMF waveform. In addition, both static and dynamic rotor eccentricities have negligible influence on the average torque, but result in large torque ripple, cogging torque, and UMF.

Design and Analysis of Asymmetric Rotor Pole Type Bearingless Switched Reluctance Motor

Bearingless switched reluctance motor (BSRM) not only combines the merits of bearingless motor (BM) and switched reluctance motor (SRM), but also decreases the vibration and acoustic noise of SRM, so it could be a strong candidate for high-speed driving fields. Under the circumstances, a 12/14 BSRM with hybrid stator pole has been proposed due to its high output torque density and excellent decoupling characteristics between torque and suspension force. However, this motor has torque dead-zone, which leads to problems of self-start at some rotor positions and large torque ripple during normal operation. To solve the existing problems in the 12/14 type, an asymmetric rotor pole type BSRM is proposed. The structure and design process of the proposed motor is presented in detail. The characteristics of the proposed motor is analyzed and compared with that of the 12/14 type. Furthermore, prototype of the proposed structure is designed, manufactured and experimented. Finally, simulation and test results are illustrated and analyzed to prove the validity of the proposed structure.

Performance Analysis of Permanent Magnet Vernier Motor with Surface and Halbach Magnets

Background: Surface permanent magnet motors (SPMVM) and dual permanent magnet motors (DPMVM) have broad prospects in direct drive systems, but some problems occur with large magnetic leakage, large torque ripple and large amount of permanent magnets (PMs). Objective: In order to reduce the torque ripple and magnetic flux leakage of SPMVM and DPMVM, and improve the torque density, a dual permanent magnet vernier machine with Halbach PM array (DHPMVM) is proposed. Method: By air gap permeance method, flux density analysis of three kinds of motors was analyzed, and the main harmonics of SPMVM and DHPMVM are investigated with structure parameters. Electromagnetic characteristics of three motors such as no-load back, electromotive force (EMF), torque, and inductance are compared and analyzed by finite element method (FEM). Results: The study found that under the same size, winding distribution, electrical load and speed conditions, DHPMVM uses Halbach PM array and consequent pole structures to reduce magnetic flux leakage and torque ripple, increase torque density, PM utilization and torque per unit PM volume. Compared with SPMVM and DPMVM, the DHPMVM proposed in this paper has better electromagnetic performance. Conclusion: The DHPMVM topology is the better choice in terms of torque density, torque ripple, and magnet usage among the investigated topologies.

Attitude control of spin-type space membrane structures using electromagnetic force in earth orbit

This research proposes a novel attitude control method for a membrane structure that uses electromagnetic torque while in Earth orbit. A spin-type membrane structure with a satellite’s body at its center is lightweight and highly compactible, enabling the realization of systems that require a large surface area. The attitude control of such a structure poses an issue because of a relatively large angular momentum of the membrane, requiring a large torque to shorten attitude control duration. Moreover, application of this torque to both the body and membrane is desired to prevent vibration on the membrane. A typical method using reaction wheels and thrusters applies a relatively large torque only to the body, which requires propellant consumption. Another method using solar radiation pressure applies torque only to the membrane, resulting in a weak torque. Thus, conventional methods cannot achieve a sufficiently large torque applied to both the body and membrane without extraneous propellant consumption. In the proposed magnetic attitude control method, the electric current flowing along the edge of the membrane and the magnetic torquers in the body interact with the Earth’s geomagnetic field and generate a large, controllable electromagnetic torque applied to both the body and membrane, which enables a large torque without consuming propellant. This research evaluates the performance of the proposed method in terms of the attitude maneuverability and vibration of the membrane using numerical simulations. Specifically, this research investigates the effects of the electric current, spin rate, and orbit inclination, which are related to the strength and direction of the electromagnetic torque. A dynamics model of the numerical simulations is derived from the multi-particle method. The numerical simulations reveal that the proposed method induces a larger torque compared with that by solar radiation pressure, improving maneuverability. This maneuverability is related to the electric current intensity and the orbit inclination. The vibration caused on the membrane during the attitude control is small; the maximum amplitude is only 3.1% of the membrane size. This amplitude decreases as spin rate increases because of geometric stiffness. Based on the results, this research concludes that the proposed method is technically feasible and contributes to the actualization of a large membrane structure.

Nonlinear antidamping spin-orbit torque originating from intraband transport on the warped surface of a topological insulator

Motivated by recent experiments observing a large antidamping spin-orbit torque (SOT) on the surface of a three-dimensional topological insulator, we investigate the origin of the current-induced SOT beyond linear-response theory. We find that a strong antidamping SOT arises from intraband transitions in non-linear response, and does not require interband transitions as is the case in linear transport mechanisms. The joint effect of warping and an in-plane magnetization generates a non-linear antidamping SOT which can exceed the intrinsic one by several orders of magnitude, depending on warping parameter and the position of Fermi energy, and exhibits a complex dependence on the azimuthal angle of the magnetization. This nonlinear SOT provides an alternative explanation of the observed giant SOT in recent experiments.

Development and application of high-power advanced exploration drilling rig for coal mining TBM

With the continuous popularization and application of TBM equipment and technology in the field of coal mine, aiming at the problems of small torque and small propulsion of existing TBM advanced exploration drilling rigs for coal mine, which is difficult to drill long borehole, and lack of special high-power drilling equipment to match with it, a high-power drilling rig for coal mine TBM is developed. This paper introduces the structure of the drilling rig, analyzes the structure and principle of the luffing mechanism and the rotary table protection device, also the strength of the key parts. Through the application in Guineng Group Heilaga Juxin coal mine shows that this equipment has large torque and propulsion, the hydraulic system and operation mode meet the requirements of long-distance separate layout in TBM. The drilling rig has good stability and high efficiency, and can meet the various needs of long drilling for advanced exploration, which promotes the application of TBM equipment and technology in the field of coal mine.

A Surgical Robotic System for Long-Bone Fracture Alignment: Prototyping and Cadaver Study

In this paper, we design, develop, and validate a surgical robotic system, entitled Robossis, to assist long-bone fracture reduction, i.e., alignment, surgeries. Unlike traditional long-bone fracture surgeries, Robossis enables the surgeon to precisely align the fractured bone in the presence of large traction forces and torques. The proposed surgical system includes a novel 3-armed robot, a bone-gripping mechanism, and a master controller. The 6-DOF 3-armed wide-open parallel robot has a unique architecture, which facilitates positioning the bone inside the robot, providing a large workspace for surgical maneuvers. Kinematic analysis shows that the symmetric 3-armed mechanism provides a significant advantage over the Gough-Stewart platform, i.e., 15 times larger rotational workspace, which is a vital advantage for fracture alignment. Theoretical and experimental testing are performed to demonstrate Robossis performance, including high accuracy and force insertion capabilities. A successful cadaver test was performed using a Robossis prototype, which shows that guided by intraoperative X-ray imaging, Robossis is able to manipulate bone in all translational and rotational directions while encountering the muscle payload surrounding the femur. Robossis is designed to balance accuracy, payload, and workspace, and its innovative design presents major advantages over the existing robot designs for the reduction of long-bone fractures.

Fault Detection of the Harmonic Reducer Based on CNN-LSTM With a Novel Denoising Algorithm

The harmonic reducer is a key component of the industrial robot. Its reliability has significant influence on the consecutive operation of the industrial robot. However, its failure rate is high due to the complicated internal structure and long-term working conditions of large load and high torque. To identify the fault type of the harmonic reducer under different working conditions, this article proposes the joint wavelet regional correlation threshold denoising (WRCTD) algorithm and convolutional neural network-long short term memory (CNN-LSTM) fault detection method. Firstly, the WRCTD algorithm utilizes the regional correlation of the wavelet decomposition coefficients and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\sigma $ </tex-math></inline-formula> criterion to suppress noise in the raw sensor data. Then, the CNN-LSTM model could mine hidden features of the processed sensor data to identify fault correctly. To evaluate the proposed method, the vibration signals of the harmonic reducer under different working conditions are collected by establishing a test rig. Comparative experimental results show that the proposed WRCTD algorithm can significantly improve the accuracy of the fault detection method. The specific values for the CNN-LSTM method and the LSTM method are 9.5% and 12.2%, respectively. In addition, the proposed CNN-LSTM method has better performance than traditional methods. It achieves the fault detection over 94.0%, which is 1.5%, 2.0%, 2.0%, 1.9%, and, 1.9% higher than the highest accuracy values of CNN, LSTM, and SVM methods in five experiments.

Study on the Design of Six-Phase Surface Inset Permanent Magnet Synchronous Generator and Motor Considering the Power Factor and Torque Ripple

In this article, a design of six-phase surface inset permanent magnet synchronous machine (SIPMSM) with the open slots is performed considering the power factor and torque ripple. Because of the reluctance torque component by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> -axis core thickness of rotor, an SIPMSM has the high torque density but the large torque ripple. To overcome the large torque ripple, there are various design methods. In case of SIPMSM with the open slots, the tapering of shoe and the notch of stator and rotor cannot apply the tapering that is applied to magnet, but the torque density and power factor decrease because the linkage flux by the permanent magnet reduces. Therefore, the thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> -axis core and tapering magnet has the tradeoff between the performance and the torque ripple. In this article, the characteristic according to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> -axis core thickness and tapering magnet is analyzed based on a finite element analysis (FEA). Furthermore, the optimal design is proposed using the performance map based on the tapering of magnet and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> -axis thickness of core. For the design of a basic model, pole–slot combinations are compared with the torque of SIPMSM according to the current phase angle. Considering the performance, the basic SIPMSM is selected for the optimal design. Based on the basic SIPMSM, the optimal design is performed based on the optimal design parameters considering the power factor and torque ripple.

Dynamical clustering interrupts motility-induced phase separation in chiral active Brownian particles.

One of the most intriguing phenomena in active matter has been the gas-liquid-like motility-induced phase separation (MIPS) observed in repulsive active particles. However, experimentally, no particle can be a perfect sphere, and the asymmetric shape, mass distribution, or catalysis coating can induce an active torque on the particle, which makes it a chiral active particle. Here, using computer simulations and dynamic mean-field theory, we demonstrate that the large enough torque of circle active Brownian particles in two dimensions generates a dynamical clustering state interrupting the conventional MIPS. Multiple clusters arise from the combination of the conventional MIPS cohesion, and the circulating current caused disintegration. The nonvanishing current in non-equilibrium steady states microscopically originates from the motility "relieved" by automatic rotation, which breaks the detailed balance at the continuum level. This suggests that no equilibrium-like phase separation theory can be constructed for chiral active colloids even with tiny active torque, in which no visible collective motion exists. This mechanism also sheds light on the understanding of dynamic clusters observed in a variety of active matter systems.

Experimental study on the effect of column lateral friction torque on seismic performance of IMS structure middle joints

The design of prestressed friction joints of integral prestressed prefabricated frame structure system (IMS) has a direct impact on the internal force distribution and deformation of the structure. To study the seismic performance of the IMS structure under low cyclic reciprocating load, quasi-static tests were carried out, and two spatial two-way prestressed frame beam slab column middle joints were designed. The effects of friction torque produced by lateral prestress on the ultimate bearing capacity, stiffness degradation, energy dissipation performance, and self-centering of joints are compared and analyzed. The test results show that the specimen SCJ2 with large column lateral friction torque is better than the specimen SCJ1 in initial stiffness, bearing capacity, and energy dissipation, but the self-centering ability and damage control are slightly poor; The column lateral friction torque is about 31.64% of the cracking moment of joint SCJ1, 7.51% of the ultimate moment, 43.58% of the cracking moment of joint SCJ2, and 10.99% of the ultimate moment, the column lateral friction torque has a great impact on the crack resistance and bearing capacity of the joint, which can not be ignored in the design. At the same time, to verify the safety of the prestressed friction joint of the IMS system and evaluate the friction and shear performance of the joint after a large earthquake, the residual shear capacity of the joint is tested on the specimens after the quasi-static test. The test results show that IMS prestressed friction joints can still ensure good shear performance and have sufficient reserve of post-earthquake shear capacity.

Predictive Direct Torque Control Application-Specific Integrated Circuit With a Fuzzy Proportional–Integral–Derivative Controller and a New Round-Off Algorithm

This study developed a predictive direct torque control (PDTC) application-specific integrated circuit (ASIC) with a fuzzy proportional.integral.derivative (PID) controller and a new round-off calculation circuit for improving the ripple response of a hysteresis controller when sampling and calculating delay times in an induction motor drive. The proposed PDTC ASIC not only calculates the stator’s magnetic flux and torque by detecting three-phase currents, three-phase voltages, and rotor speed but also eliminates large ripples in the torque and flux by using the fuzzy PID controller. Furthermore, the proposed round-off algorithm reduces the calculation error of the composite flux. A fuzzy voltage vector switching table is proposed not only to speed up the calculating speed but also to resolve the instability generated by its large torque and flux ripples. The Verilog hardware description language was used to implement the hardware architecture, and the aforementioned ASIC was fabricated using the 0.18-μm 1P6M CMOS process of the TSMC by employing the cell-based design method. The predictive calculations, fuzzy PID controller, fuzzy voltage vector switching table, and round-off calculation algorithm improved not only the ripple issue faced in traditional direct torque control but also the control stability and robustness. The measurement results indicate that the proposed PDTC ASIC has an operating frequency, a sampling rate, and a dead time of 50 MHz, 100 kS/s, and 100 ns, respectively, at a supply voltage of 1.8 V. The power consumption and chip area of this ASIC are 1.0027 mW and 1.169 × 1.168 mm2, respectively. The main advantages of the proposed PDTC ASIC are its low power consumption, small chip area, robustness, and convenience.

Dynamic behavior of oligomers formed by “十” shaped self-propelling agents

In recent years, active matter has attracted tremendous research interest. Active matter displays many phenomena, such as super-diffusion, huge fluctuation and collective motion. The shape of active agent plays a critical role in the self-assembly of active matter. Understanding the oligomers’ dynamics of active agents is the first step to study the self-assembly of massive agents. Here, we design a self-properlling particle with the “十” shape using the Hexbug robot and investigate the dynamics of oligomers composed of these particles. To track the position of particles, the top of the particles is marked by black cards with white dots in the center. We find that these particles can agglomerate together to form stable oligomers consisting of two, three, or four particles. We study the dynamics by analyzing the trajectory, mean-square displacement, angular velocity, angular velocity distribution and the curvature distribution. We find that the dynamics can be divided into two types. One is the combination of eccentric rotation with small circular radius and irregular translation, which occurs in the system with the zero resultant force and nonzero torque. The other is the eccentric rotation with a large circular radius, which appears in the system in which both the resultant force and torque are not zero. In addition, we find that the translational dynamics of oligomers displays a super diffusion on a short time scale, influenced by the confirguration of oligomers. Further, the larger torque and the smaller moment of inertia result in the bigger angle speed of oligomers. Moreover, we investigate the curvature distribution of the trimer and find that the faster the angle speed of the trimer, the bigger its curvature is.