High Specific Torque Research Articles

Anodized Aluminum Foil Winding Axial Flux Machine for Direct-Drive Robotic Applications

There is a need for higher specific torque electric actuators in novel direct-drive robotic applications. Since the specific torque is inherently limited by material properties, designers have to look at novel materials to push the specific torque limit further. In this article, anodised aluminium foil is considered as an alternative to enamelled copper wire in a yokeless and segmented armature axial flux machine. This machine topology has a high specific torque and is particularly suited for an anodised aluminium foil winding. The DC resistance, thermal properties and eventually the specific torque of a prototype test case machine are compared for both winding materials. A 3D thermal finite element model is used to analyse the influence of the thermal interface between winding body and housing, and the influence of the cooling performance on the specific torque. To conclude, anodised aluminium foil winding offers a higher specific torque in direct-drive yokeless and segmented armature axial flux actuators where the winding body thermal resistance is dominant in the thermal path from heat source to heat sink. It is experimentally shown that for the prototype machine, the torque per kg active stator mass increases 13% through the use of anodised aluminium foil.

Pole shape design of ring winding axial flux permanent magnet used in a direct‐drive electric boat for cost‐efficient cogging torque alleviation

AbstractThe recently introduced Ring Winding Axial Flux Permanent magnet Motor (RW‐AFPM) is inspired by the yokeless structure of Yokeless and Segmented Armature (YASA) AFPMs and the partitioned‐phases configuration of transverse flux motors. Its potential application for rim‐driven electric ships propulsion has been examined in the previous studies and, here, it will be studied for ultra‐light direct‐drive electric boats. Owing to their specific structural features, the relatively large cogging torque of RW‐AFPMs seems to be a significant challenge for such applications. On the other hand, as investigated in previous studies, cogging torque reduction methods, such as conventional skewing, seem unsuitable for this type of machine. Thus, this paper will address the cogging torque issue via a comprehensive pole shape analysis. The results will be useful for all kinds of partitioned‐phases topologies that have high specific torque capability but suffer from large cogging effects. All analyses are performed via 3D‐FE models, the accuracy of which is pre‐verified through experiments.

Высокоэффективный электропривод с системой технического зрения для тягового применения в тяжелых гусеничных машинах

A new type of electric motor as a traction drive DET400 based on a field regulated reluctance machine (FRRM) provides high energy efficiency and high specific torque. A comparison is made between FRRM and various types of traction electric drives. The issues of designing the FRRM are considered, the geometric parameters of the electric machine are optimized to achieve the maximum specific indicators. To expand the functionality and ensure operational safety, it is proposed to introduce computer vision into the electronic control system. As a result, the FRRM is designed for traction applications based on the real requirements of a Russian-made crawler tractor.

Combined Optimal Torque Feedforward and Modal Current Feedback Control for Low Inductance PM Motors

Small sized electric motors providing high specific torque and power are required for many mobile applications. Air gap windings technology allows to create innovative lightweight and high-power electric motors that show low phase inductances. Low inductance leads to a small motor time constant, which enables fast current and torque control, but requires a high switching frequency and short sampling time to keep current ripples and losses in an acceptable range. This paper proposes an optimal torque feedforward control method, minimizing either torque ripples or motor losses, combined with a very robust and computation-efficient modal current feedback control. Compared to well-known control methods based on the Clarke-Park Transformations, the proposed strategy reduces torque ripples and motor losses significantly and offers a very fast implementation on standard microcontrollers with high robustness, e.g., against measurement errors of rotor angle. To verify the accuracy of the proposed control method, an experimental setup was used including a wheel hub motor built with a slotless air gap winding of low inductance, a standard microcontroller and GaN (Gallium Nitride) Power Devices allowing for high PWM switching frequencies. The proposed control method was validated first by correlation of simulation and experimental results and second by comparison to conventional field-oriented control.

Assessing the Impact of Lubricant and Fuel Composition on LSPI and Emissions in a Turbocharged Gasoline Direct Injection Engine

<div class="section abstract"><div class="htmlview paragraph">Downsized turbocharged gasoline direct injection (TGDI) engines with high specific power and torque can enable reduced fuel consumption in passenger vehicles while maintaining or even improving on the performance of larger naturally aspirated engines. However, high specific torque levels, especially at low speeds, can lead to abnormal combustion phenomena such as knock or Low-Speed Pre-Ignition (LSPI). LSPI, in particular, can limit further downsizing due to resulting and potentially damaging mega-knock events. Herein, we characterize the impacts of lubricant and fuel composition on LSPI frequency in a TGDI engine while specifically exploring the correlation between fuel composition, particulate emissions, and LSPI events. Our research shows that: (1) oil composition has a strong impact on LSPI frequency and that LSPI frequency can be reduced through a carefully focused approach to lubricant formulation. In addition, (2) we observed significant improvement potential in Brake Mean Effective Pressure (BMEP) achievable with zero LSPI events using both experimental and market-representative lubricant formulations. Finally, (3) fuels blended with high polyaromatic content were shown to increase LSPI frequency significantly; these fuels also caused a significant increase in particulate mass (PM) and particulate number (PN) emissions. In this paper, we discuss the above results along with the development and use of a high-fidelity test method to measure LSPI under steady-state test conditions.</div></div>

Design and Experimental Investigation of BLDC Motor for Aircraft Electromechanical Actuator

Among the electric motors used in the aircraft industry, brushless direct-current (BLDC) ones have the highest power density and efficiency. This paper presents the BLDC motor design and electromagnetic analysis for use in direct-drive aircraft electromechanical actuator. An experimental BLDC motor prototype has been made to test the output. Finite-element analysis (FEA) has been applied to finalize and investigate the characteristics of the BLDC motor design. Then, FEA output has been compared to experimental results in order to validate the latter. The high specific torque has been attained by the 12-slot, 8-pole configuration. Segmenting the rotor magnetic pole has reduced loss to eddy currents in permanent magnets, while double-layer concentric winding has reduced loss to copper and more effective dissipated heat. The BLDC motor presented herein has short response time and high rotor rotational angle precision thanks to the high torque to rotor moment-of-inertia ratio. For evaluating BLDC motor performance assessment, experiments have been run stand-alone, i.e. with no integration in a gearless EMA. Rotational speed vs torque, as well as the holding torque vs phase current at a given BLDC motor rotor position fit well the FEA output at a maximum difference of 10%. Post-test residual magnetization readings of the permanent magnets proved the BLDC motor operable.

Performance assessment tool based on loadability concepts

In order to choose electric machines for transport applications, i.e. automotive, aerospace, railway and naval, a tool that can make quick tradeoffs of high specific torque electric motors has been developed. The level of the different technologies involved in an electrical machine can be quantified using the loadability concepts developed by experienced designers. After recalling these concepts, magnetic, electric and thermal balances are used to calculate the main sizes of an electric motor according to some targets. Specific power or specific torque can then be quickly assessed. The proposed approach is validated by applying the tool to some known high torque industrial motors.

Chained Iron Microparticles for Directionally Controlled Actuation of Soft Robots.

Magnetic field-directed self-assembly of magnetic particles in chains is useful for developing directionally responsive materials for applications in soft robotics. Using materials with greater complexity allows advanced functions, while still using simple device architectures. Elastomer films containing chained magnetic microparticles were prepared through solvent casting and formed into magnetically actuated lifters, accordions, valves, and pumps. Chaining both enhances actuation and imparts a directional response. Cantilevers used as lifters were able to lift up to 50 times the mass of the polymer film. We introduce the "specific torque", the torque per field per mass of magnetic particles, as a figure of merit for assessing and comparing the performance of lifters and related devices. Devices in this work generated specific torques of 68 Nm/kgT, which is significantly higher than in previously reported actuators. Applying magnetic fields to folded accordion structures caused extension and compression, depending on the accordion's orientation. In peristaltic pumps comprised of composite tubes containing embedded chains, magnetic fields caused a section of the tube to pinch closed where the field was applied. These results will facilitate both the further development of soft robots based on chained magnetic particles and efforts to engineer materials with higher specific torque.

REDUCER RESONANT ELECTRIC STEERING

The general requirements to a reducer of the resonant electric steering drive (RESD) taking into account its specifics the most important of which are high efficiency in both directions, a high specific torque and large gear number in small volume are stated. The short review of literature on a subject is carried out, the main types of the modern mechanical transmissions are given, the analysis of suitability of each of them for application in the resonant steering drive is carried out and the most suitable – wave transmission with the intermediate bodies of rolling is selected. The principle of action of this mechanical transmission is considered and the concept of the steering drive in overall dimensions of a support assembly of a aerodynamic rudder which in the best way is suitable for RESD on the basis of this transmission is discussed. Results of calculation of mass and overall dimensions of a reducer, its specific indexes and an assessment of an achievable technical level of RESD on the basis of the selected transmission are given.

Plant-based torsional actuator with memory

A bundle of a few loblolly pine (Pinus taeda) cells are moisture-activated torsional actuators that twist multiple revolutions per cm length in direct proportion to moisture content. The bundles generate 10 N m kg−1 specific torque during both twisting and untwisting, which is higher than an electric motor. Additionally, the bundles exhibit a moisture-activated, shape memory twist effect. Over 70% of the twist in a wetted bundle can be locked-in by drying under constraint and then released by rewetting the bundle. Our results indicate that hemicelluloses dominate the shape fixity mechanism and lignin is primarily responsible for remembering the bundle’s original form. The bundles demonstrate proof of a high specific torque actuator with large angles of rotation and shape memory twist capabilities that can be used in microactuators, sensors, and energy harvesters.

Axial Flux Segmented SRM With a Higher Number of Rotor Segments for Electric Vehicles

Motors for in-wheel electric vehicle application should have high specific torque. In addition, these motors should be rugged, insensitive to vibration, and temperature variation. Therefore, segmented rotor switched reluctance motor (SSRM) could be an attractive alternative to permanent magnet-based motors, which are being used for this application. A limitation of SSRM is that it requires full pitch winding for its operation. Since, in-wheel motors have high diameter to axial length (D/L) ratio, SSRM of these dimensions would be bulky and has high copper loss due to full pitch winding. Hence, in this paper, a novel SSRM with nonoverlapping winding is proposed. This motor is an axial flux SSRM (AFSSRM) with toroidal winding arrangement. It has single-stator, dual-rotor configuration with 12 stator poles and 16 rotor segments on each rotor disc. Design procedure for AFSSRM is developed and a flowchart describing the design algorithm is presented. A finite element method-based simulation is carried out to verify the performance of the proposed AFSSRM. In order to validate the performance of the motor, a prototype is fabricated and experimental results are presented.

A High-Torque-Density Permanent-Magnet Free Motor for in-Wheel Electric Vehicle Application

A motor for in-wheel electric vehicle (EV) requires high efficiency and specific torque. In view of this, permanent-magnet brushless dc (PM BLDC) motor is most commonly employed for this application. However, due to the increasing cost of PMs, machines that do not use PMs are attracting interest. Switched reluctance motor (SRM), with its simple and robust construction, along with fault tolerant operation, is a viable option for in-wheel EV application. However, the SRM has low specific torque as compared with BLDC. Therefore, design improvements are required to make SRM a viable alternative to BLDC motor. In this paper, a new 12/26 pole SRM with high specific torque is proposed for in-wheel EV application. This machine has segmented-rotor-type construction. Also, concentrated-winding arrangement is used, ensuring low end-winding volume and copper loss. The developed machine also has high efficiency. In order to verify the design, the prototype of the machine is fabricated, and experimental results are presented.

Direct-Drive Contactless Wind Generator with Concentrated Winding

A clear trend has emerged in the field of wind power industry concerning the creation of low-, medium-, and even high-power direct-drive wind turbines without the use of gearboxes. Such generators are usually multipolar and mostly excited from permanent magnets. In the low-speed performance, multipolarity means a higher specific torque and reliability as well as lower operating costs, which in the case of high-speed generators is hindered by gearboxes. Multipolarity with a high specific torque can be achieved mainly through the use of permanent magnets of high-energy materials (such as NdFeB) and through design solutions for the armature winding. The authors compare two most common types of wind generator's armature windings: the distributed one, which contains a coil embracing several teeth, and the concentrated armature winding - with one coil for one stator tooth. The comparison (along with the experience in developing the wind turbines) shows that the con-centrated winding version has a number of advantages, the main of them being the multipolarity. This means that the generator with a concentrated winding can be more acceptable for the direct-drive wind turbines, is easier to make and simpler to operate. Another very important advantage of concentrated windings shown in this work

Micro-Scale Modeling of Carbon-Fiber Reinforced Thermoplastic Materials

Thin-walled textile-reinforced composite parts possess excellent properties, including lightweight, high specific strength, internal torque and moment resistance which offer opportunities for applications in mass transit and ground transportation. In particular, the composite material is widely used in aerospace and aircraft structure. In order to estimate accurately the parameters of the constitutive law of woven fabric composite, it is recommended to canvass multi-scale modeling approaches: meso, micro and macro. In the present investigation, based on the experimental results established by carrying out observations by Scanning electron microscope (SEM), we developed a micro-scale FEM model of carbon-fiber reinforced thermoplastic using a commercial software ABAQUS. From the SEM cartography, one identified two types of representative volume elementary (RVE): periodic and random distribution of micro-fibers in the yarn. Referring to homogenization method and by applying the limits conditions to the RVE, we have extracted the coefficients of the rigidity matrix of the studied composites. In the last part of this work, we compare the results obtained by random and periodic RVE model of carbon/PPS and we compute the relative error assuming that random model gives the right value.

Design, manufacture and analysis of a thermoplastic composite frame structure for mass transit

Thin-walled composite sub-elements possess excellent properties, including high specific strength, lightweight, internal torque and moment resistance which offer opportunities for applications in mass transit and ground transportation. In the present work, an open section thin-walled thermoplastic composite frame segment (sub-element) of a mass transit bus was designed, analyzed and manufactured to replace a conventional metal-based design. Three cross-section configurations, rectangular, V-shape and rounded C-shape, were considered, and different lamina stacking sequences, (0/90) 6 , [±45/(0/90) 2 ] s , and [±45/(0/90)] 3 were compared. Carbon fiber/polyphenylene sulphide (carbon/PPS) was the material choice, and single diaphragm forming (SDF) process was adopted to manufacture the frame segment. In-plane compression testing was conducted on the manufactured carbon/PPS composite frame to validate the finite element analysis results. A successful design concept to manufacture strategy of the open thin-walled carbon/PPS thermoplastic composite frame segment was demonstrated.

Design and control of a novel spherical permanent magnet actuator with three degrees of freedom

The paper describes the design and control of a new version of a spherical permanent magnet actuator, which is capable of three degrees of freedom and a high specific torque. Based on an analytical magnetic field distribution, the torque vector and back-emf are derived in closed forms. An optimal design procedure is proposed to achieve maximum output torque or maximum acceleration for a given payload. The control of the actuator, whose dynamics are similar to those of robotic manipulators, is facilitated by the establishment of a complete actuation system model and the application of the computed torque control law. The validity of the analysis and design techniques, and the effectiveness of the control strategy, are confirmed by measurements.

Different torque meets specific compounding requirements

Co-rotating twin screw extruders from Maris feature a number of technological innovations. Maris' two production lines — TM-HT and TM-MW — have the same screw geometry but they have different specific torque. This means for the same screw speed, the TM-HT can offer an increase in productivity. The company explains that the gearbox on the TM-HT extruders has been designed to give high specific torque and fast screw rotation. The maximum screw rotation speed is 1300 rpm (650–1300 rpm) and specific torque is 21 Nm/cm 3. The specific torque offered by the TM-MW is 18 Nm/cm 3. This is a short news story only. Visit www.addcomp.com for the latest additives and compounding industry news

Vernier hybrid machines

The vernier hybrid machine is a member of the family of variable-reluctance permanent-magnet machines. It develops high specific torque by means of a magnetic gearing effect but it suffers from low power factor. The construction of the machine is simple. Analytical formulae are derived for specific torque and power factor. The formulae may be used to find a suitable compromise between the desire for high specific torque and for good power factor. Static torque tests taken from a small laboratory machine are in satisfactory agreement with theory.

Optimal design of permanent magnet brushless AC machines for electric vehicle applications

Permanent magnet brushless ac machines are ideally suited for traction applications, since they are energy efficient and have a high specific torque and a high peak to continuous torque capability. Further, they can be field-weakened to facilitate constant power operation over an extended speed range without compromising the VA rating of the drive. However, they must be design optimised with due regard to their duty cycle, their thermal management, the volt-ampere constraint of the drive and any space envelope constraints. A design methodology which accommodates these aspects into the electromagnetic design synthesis process has been developed and employed to design a traction machine for a small urban vehicle.

Power Electronic Interface Devoted to Starter/Alternator Systems for Automotive Applications

This paper deals with the analysis and selection of a suitable configuration of the poiver electronic interface devoted to a starter/alternator (S/A) system for automotive applications. On the basis of the application requirements (i.e. the electrical demands in both motoring and generating mode of operation of the S/A) different configurations of the power electronic system are compared by means of both power sizing and cost estimations. Axial-flux permanent-magnet (APPAO machine is selected for the proposed S/A system on the basis of distinguishing characteristics of this machine topology as high specific torque and suitable shape to work as a flywheel. The results of the study indicate that a suitable regulation of the d.c.-link voltage is necessary to dramatically reduce the power size of the electronic components installed on board a vehicle.