Torque Transmission Capability Research Articles

Study on the Speed Control and Heat Dissipation Performance of Cone-tube Permanent Magnet Governor

The speed regulation range, output torque, and heat dissipation performance are important performance indicators of permanent magnet speed regulators. Enhancing the speed regulation range and output torque, and reducing the heat generation power are of significant importance for expanding the application range of permanent magnet speed regulators. To address the issues of a single adjustment process, insufficient heat dissipation space, and inadequate torque transmission capability of the traditional straight-barrel permanent magnet speed regulator, a cone-barrel permanent magnet speed regulator with a magnetic rotor assembly structure was designed through the analysis of the structure and transmission characteristics of the traditional straight-barrel permanent magnet speed regulator. Using the ANSYS Maxwell finite element analysis software, the output torque characteristics of the cone-barrel structure were studied. Considering the effect of eddy current heating, a conjugate heat transfer model for the permanent magnet speed regulator was developed, and the heat dissipation performance of the cone-barrel structure was explored through ANSYS Fluent simulation analysis. The results indicate that compared to the traditional straight-barrel permanent magnet speed regulator, the cone-barrel regulator can provide greater output torque when fully coupled; at maximum power consumption, the air velocity over the surface of the cone-barrel permanent magnet speed regulator conductor is higher, resulting in better heat dissipation and thus a lower operating temperature.

Analytical and Experimental Investigation to Resolve Surface Related Fatigue Failure in Helical Gears

With the improvement of metallurgical process and tools it became possible to modify the material property of the steel to a desired possible level where its torque transmission capability can be enhanced. Case hardening and surface grinding is one such method which is used to leverage the surface durability and core strength of gears. With the enhancement in the torque transmission capability the load per unit area of face width also increased causing huge surface pressure. They are subjected to various conditions of load, speed, temperature, and ambient conditions. Micropitting is one such surface related failure which starts on tooth flank in terms of surface texture change. This may further grow in magnitude and result in catastrophic failure. This research work is performed to compare the results of analytical and experimental investigation for the possible micropitting initiative zone. Analytical approach is carried out by using the KISSsys model and the experimental work is carried out by using a dynamometer test rig to apply the load on the gearbox shaft for a defined load cycle. It was clearly visible that the micropitting has initiated below the pitch line of pinion. Tooth profile is later modified with lead and crown modification. After the application of this modification the tooth profile related failure was not visible for similar load testing cycle.

Harnessing elastic energy to overcome singularity issues in four-bar mechanisms with a crank link

The ability to convert reciprocating, i.e., alternating, actuation into rotary motion using linkages is hindered fundamentally by their poor torque transmission capability around kinematic singularity configurations. Here, we harness the elastic potential energy of a linear spring attached to the coupler link of four-bar mechanisms to manipulate force transmission around the kinematic singularities. We developed a theoretical model to explore the parameter space for proper force transmission in slider-crank and rocker-crank four-bar kinematics. Finally, we verified the proposed model and methodology by building and testing a macro-scale prototype of a slider-crank mechanism. We expect this approach to enable the development of small-scale rotary engines and robotic devices with closed kinematic chains dealing with serial kinematic singularities, such as linkages and parallel manipulators.

On the Design of Cylindrical Magnetorheological Clutches

Magnetorheological fluids (MRFs) exhibit variable mechanical properties in response to magnetic stimuli. Thanks to their rapid and reversible viscosity changes, MRFs can be utilized in a variety of applications including torque transmission devices such as clutches. In this work, the geometrical design of cylindrical MR clutches is investigated with the aim of optimizing the torque transmission capability. Effects of design parameters such as radius, gap size, effective length, and MRF volume are investigated in the presence of variable magnetic field. Magneto-mechanical behavior of some MR fluids with different particle content are investigated by means of two different constitutive models to simulate the clutch performance in a range of geometrical parameters. It is shown that the transmitted torque increases nonlinearly by inner radius of the clutch, for example, in the studied range, 150% higher torque is achieved for only 40% larger radius. The clutch’s gap size does not much affect the torque, however, since it significantly affects the required volume of MRF, a lower gap size is favorable. The torque is also calculated for constant volumes of the MRFs. At a certain volume, although a higher radius translates to a shorter length, it is still favorable. For example, a 40% increase in the design radius, almost doubles the transmitted torque for both the studied MRFs. Moreover, a clutch filled by an MRF with higher particle content can transmit higher torques. It is also concluded that increasing the clutch’s radii is an easier way to improve the mean torque while altering the applied magnetic field is a better way to adjust the range of achievable torques. The simulations also demonstrate the importance of an accurate and reliable constitutive model in the design of MR devices. It is shown that Bingham model is not reliable at high magnetic fields as it underestimates the transmitted torque though calibrated at each field intensity. However, the employed nonlinear model provides more reliable results by only being calibrated at an arbitrary field.

Modification of the Tooth Geometry of a Polymer GEAR with a Straight Tooth Line to Adjust the Torque Transmission Capability in One Direction Only

This paper describes a methodology for modifying a tooth for the ability to transmit torque in one direction only. It presents two methods (analytical and numerical) of tooth mass reduction while maintaining functional features of the whole transmission. The results of the above mentioned methodology are presented on the example of a mass-produced transmission.

A study of factors affecting torque transmission in permanent magnet-based magnetorheological fluid clutch

In this article, the study of several factors affecting the torque transmission capability of a permanent magnet-based, drum-type magnetorheological fluid (MRF) clutch is presented. These factors are: number of magnetic poles in the magnet assembly, material of the clutch, MRF layer thickness, and relative rotational velocity between the input and output stages of the clutch. For this purpose, a special single-MRF layer clutch was designed and fabricated, one which allows the convenient assembly and disassembly to reduce preparation time for testing. The average transmitted torque of this clutch under several combinations of the aforementioned factors was recorded and analyzed. Additionally, several magnetostatic simulations of the clutch were carried out, and both the magnetic flux density and transmittable torque calculated from the results of these simulation were compared against experimental measurements. It was found that magnet assemblies with lower number of magnetic poles resulted in higher torque outputs, however, the effectiveness of the utilized torque variation mechanism was reduced due to magnetic saturation of the components of the clutch. The material of the clutch was found to have a significant effect at low relative rotational velocities, resulting in a nonlinear relationship between transmitted torque and relative angular velocity. This nonlinear effect was more significant when aluminum was used in the components which interact directly with the MR fluid whereas the use of ferromagnetic components reduced this effect. Finally, the thickness of the MRF layer was found to have a significant effect on the transmitted torque of the MRF clutch, although not according to what magnetostatic simulations predict.

Lubrication performance of magnetorheological fluid in shear mode magnetorheological clutch with and without groove

In this work, the lubrication performance of magnetorheological fluid-filled parallel discs of shear mode magnetorheological clutch is investigated. A magnetorheological fluid contains magnetic particles responsible for the yield strength and hence torque transmission capability in the magnetorheological clutch. The wear damages of magnetic particles of a magnetorheological fluid and magnetorheological clutch discs are examined by scanning electron microscopy and optical microscopy. Energy-dispersive X-ray spectroscopy is used to investigate the variation in chemical composition before and after the experimental test. A test rig is developed to test the torque transmission for a fabricated magnetorheological clutch with a grooved and non-grooved disc. The grooves' impact on both magnetorheological clutch discs' wear and magnetorheological fluid is investigated. It has been observed that the minimum wear damage occurs in the magnetic particles and the disc surface for the circular grooved magnetorheological clutch disc surface than the non-grooved disc surface. An effect of surface texture on the temperature distribution of the magnetorheological clutch is studied through simulation. Simulation results show that the groove's presence on the disc surface can improve the magnetorheological clutch's heat transfer. Hence, the grooved texture improves the lubrication performance and durability of both magnetorheological fluid and magnetorheological clutch.

Analysis of Spoke-Type Brushless Dual-Electrical-Port Dual-Mechanical-Port Machine With Decoupled Windings

Brushless dual-electrical-port dual-mecha-nical-port (BLDD) machine has become a good candidate to replace the traditional mechanical continuously variable transmission owing to its high compactness, reliability, and torque transmission capability. However, the mutual coupling between two sets of windings fed by different frequency currents leads to strong interference during both health and fault conditions, whereas the coupling effect is difficult to be reduced in the regular BLDD machine due to its operation principle. This paper presents a systematic analysis on a novel spoke-type BLDD (STBLDD) machine, aiming to eliminate coupling of windings. Using the winding function theory, the decoupling principle is analyzed in detail, and corresponding slot/pole combinations are derived. Through finite-element analysis, parameter influences on the performance of this STBLDD machine are then studied. A prototype and test bed have been designed and manufactured, and the experimental results verify the analysis results.

A New Structure for the Magnetic Gear

In this paper, a new structure for increasing the magnetic gear torque is proposed, which has high torque density and high mechanical properties. The permanent magnets (PMs) of the outer rotor are spoked and magnetized along the tangential direction. The PMs of inner rotor are the surface-mount type and magnetized in the radial direction. The PMs are fixed in the inner and outer rotors’ iron yoke that the aim is to keep the PMs from falling off during the rotation. In order to reduce the amount of iron, it is considered to slot on the outer rotor. The two-dimensional finite element method is used for simulating the proposed model. The magnetic field and electromagnetic torque of the magnetic gear are calculated. Compared with the conventional magnetic gear, the results show that the torque transmission capability of the proposed magnetic gear can be substantially improved.

Development of a Passive Magnetorheological Fluid Clutch With Field-Blocking Mechanism

This paper introduces a new torque variation mechanism for a magnetorheological fluid (MRF) clutch which uses permanent magnets. Previous prototypes of this clutch changed the position of the permanent magnets in and out of the clutch to vary the transmitted torque. The new design uses a field-blocking mechanism, a steel cylinder which covers the magnets, to vary the transmitted torque. The steel cylinder moves in and out the clutch, covering the magnets, and thus alter the intensity of the magnetic field the MRF experiences. Magnetostatic simulations of the magnetic field behavior inside the clutch and fluid dynamic simulations were carried out with the objective of finding the torque transmission capability. A mathematical model was also used for this purpose, where the magnetostatic simulation results were used to estimate the transmitted torque at several clutch configurations. Finally, several experimental measurements were carried out to determine the real behavior of the clutch and compare and verify the simulations and mathematical model results.

A Brushless Dual-Mechanical-Port Dual-Electrical-Port Machine With Spoke Array Magnets in Flux Modulator

Brushless dual-mechanical-port dual-electrical-port (BLDD) permanent magnet (PM) machines have been gaining more and more attentions in recent years, with the merits of two decoupled rotors and contactless torque transmission. However, existing BLDD machines tend to suffer from low torque density due to low working flux density. In this paper, a BLDD machine with spoke array PMs in flux modular is proposed, which improves the torque density significantly. The structure and operation principle of the proposed machine is introduced. Detailed performance comparison between three different BLDD machine topologies, i.e., surface-mounted PM BLDD machine, flux-bidirectional modulation BLDD machine, and the proposed BLDD machine, is presented through finite-element analysis. The analyzing results show that although the modulated magnetic field coupled with the modulation winding is slightly reduced, the torque transmission capability of the regular winding in the proposed BLDD machine is significantly enhanced when compared with that of its two counterparts.

A Coaxial Magnetic Gear With Consequent-Pole Rotors

In this paper, a novel coaxial magnetic gear (MG) is proposed, in which both permanent magnet and consequent poles are employed on the inner and outer rotors. The MG is expected with improved torque transmission capability by increasing the effective magnetic flux and offering additional reluctance torque. Air-gap field distribution and torque–angle characteristic of this MG are analyzed and compared with the conventional MG, which adopts dual surface-mounted permanent magnet rotors. To maximize the torque density, several key design parameters are investigated using finite-element method. Analysis results indicate that the proposed MG with ferrite magnets can largely improve the pull-out torque. In addition, end effect and power losses with different rotor structures are analyzed. Performance of two optimized MGs is then validated with test. Also, the MG cost effectiveness with different magnet materials is presented.

Parallel-path power flows in magnetic-geared permanent magnet machines with sandwiched armature stator

Due to the large torque density of magnetic gears(MGs), magnetic-geared permanent magnet machines(MGPMs) have become promising competitors in the family of direct-drive machines. According to the deployment of armature stators, MGPMs can be generally classified into three types, viz., MGPM with inner armature stator(MGPM-IAS), MGPM with outer armature stator(MGPM-OAS), and MGPM with sandwiched armature stator(MGPM-SAS). Our investigation finds out that the MGPM-SAS can achieve parallel-path power flows better than the MGPM-OAS, while the MGPM-IAS is with serial power flow paths. Therefore, the torque capability of MGPM-IAS is limited by the torque transmission capability of its integrated MG. However, the MGPM-SAS has the possibility to offer even higher output torque than its integrated MG. This paper focuses on the MGPM-SAS. And three typical MGPMs and their power flow paths are introduced; the interaction of electromagnetic fields in MGPM-SAS is analyzed; simulation calculation and experimental verification are conducted to demonstrate the validity of the theoretical analysis.

Design and analysis of a direct-drive wind power generator with ultra-high torque density

In order to get rid of the nuisances caused by mechanical gearboxes, generators with low rated speed, which can be directly connected to wind turbines, are attracting increasing attention. The purpose of this paper is to propose a new direct-drive wind power generator (DWPG), which can offer ultra-high torque density. First, magnetic gear (MG) is integrated to achieve non-contact torque transmission and speed variation. Second, armature windings are engaged to achieve electromechanical energy conversion. Interior permanent magnet (PM) design on the inner rotor is adopted to boost the torque transmission capability of the integrated MG. Nevertheless, due to lack of back iron on the stator, the proposed generator does not exhibit prominent salient feature, which usually exists in traditional interior PM (IPM) machines. This makes it with good controllability and high power factor as the surface-mounted permanent magnet machines. The performance is analyzed using finite element method. Investigation on the magnetic field harmonics demonstrates that the permanent-magnetic torque offered by the MG can work together with the electromagnetic torque offered by the armature windings to balance the driving torque captured by the wind turbine. This allows the proposed generator having the potential to offer even higher torque density than its integrated MG.

DESIGN AND ANALYSIS OF A NEW AXIAL-FIELD MAGNETIC VARIABLE GEAR USING POLE-CHANGING PERMANENT MAGNETS

This paper presents a new non-rare-earth axial-field magnetic variable gear (MVG). By real-time changing the numbers of permanent magnet (PM) pole-pairs in the input and output rotors, the gear ratio becomes controllable. The key is to propose a new stationary ring integrated with magnetizing windings in such a way that various PM pieces can be independently magnetized to form different pole-pair numbers. After introducing the unique features of the non-rare-earth PM material aluminum-nickel-cobalt (AlNiCo), the proposed topology and design principle are discussed. By using finite element analysis, the electromagnetic performances of the proposed MVG under different gear ratios are analyzed. In particular, the corresponding torque transmission capability is assessed, and the influence caused by the introduction of the magnetizing windings is discussed. Hence, the validity of the proposed MVG can be verified.

Magnetic Gears for High Torque Applications

An analytical model for the prediction of the magnetic field distributions in the airgaps and permanent magnets of large radial-field magnetic gears equipped with radially and Halbach magnetized (HM) permanent magnets is presented. The model is compared to 2-D finite element analysis and has been employed for the design optimization of a large magnetic gear. It is shown that adopting a discrete HM distribution results in significant improvements in torque transmission capability and substantial reduction in active mass.

Simulation and Test Study of Multidisc Magneto-Rheological Fluid Clutch

A Magneto-rheological Fluid Clutch (MRC for short) which has a novel and simple structure is designed; the research on the magnetic field distribution is based on the finite element simulation software which is named Ansoft; In order to test the work performance, the electronic torsion testing machine is used for the torque transmission capability and controllability test. The experimental results reveal that the MRC could meet the torque transmission demand of high power machine and response quickly and reliably.

Compliant Cardan Universal Joint

In this study, a compliant version of the Cardan universal joint is introduced. The original design consists of two identical parts assembled at right angle with respect to each other. The single piece part can be produced from planar materials; thus, it has the advantage of easiness in manufacturing. Dimensions of the mechanism are devised in order to satisfy the Cardan joint theory and to avoid an undesired contact between the identical parts. As a design example, a mechanism is dimensioned. The resultant stresses at flexural hinges of this sample are determined via finite element analysis method and torque transmission capability of this mechanism is determined. Further, this sample is manufactured and operated under a considerable output loading. Therefore, robustness of the compliant Cardan joint is verified with this prototype. As well, it is verified that the results of experiments are consistent with the theoretical approaches.

A Variable Speed Magnetic Gear Box Using Contra-Rotating Input Shafts

This paper presents analytical, simulation, and practical analyses of a variable speed magnetic gearbox (MG) that uses contra-rotating (CR) input shafts. The CR turbine comprises two sets of rotors one behind the other: one rotor rotates in a clockwise direction while the other rotor rotates in an anticlockwise direction. Our magnetic gear magnetically combines the two CR input shafts into a single variable speed output shaft, and consists of three rotating parts: two contra-rotating low-speed input shafts and a single high-speed output shaft. Theoretical analysis is presented to show how to control the speed of the output shaft via control of the speeds of the two input shafts. This analysis is then supported by simulation and experimentation. The paper discusses the MG torque transmission capability by presenting pull-out torque test results and efficiency information when being driven through the different load torque shafts. The effective ratio of the MG is explained in terms of its torque curve result. A prototype gearbox was built, having been designed with an electromagnetic finite-element software package, and evaluated using a practical test rig.

Comparative Study Between Mechanical and Magnetic Planetary Gears

The paper deals with the possibility of replacing a mechanical planetary gear system by a magnetic planetary gearbox. The magnetic planetary gearbox has many advantages such as contact-free, no gear lubrication, high-speed-reduction ratio and high durability. Firstly, the principle of operation, design equations and Willis relation for the magnetic and the mechanical planetary gears are given. A comparative study between the two systems in terms of torque transmission capabilities is presented.