Maximum Average Torque Research Articles

Design and Analysis of In-Wheel Double Stator Slotted Rotor BLDC Motor for Electric Bicycle Application

<p>This paper discusses about design and analysis of double stator slotted rotor (DSSR) BLDC motor for electric bicycle application. Usually single stator (SS) BLDC motor is used in an electric bicycle. This type of motor has low performance and need to be charged regularly. The objective of this research is to design and analysis DSSR motor that have high torque. At starts, design specification for the electric bicycle is calculated. Next, design process for DSSR is carried out by using the desired parameter. Lastly, analysis for double stator slotted rotor is simulated using FEM. Result for average back emf, average inductance, inner stator flux density, outer stator flux density, average torque and estimate torque constant is obtained. Result for average torque from FEM archieve the requirement of motor torque for DSSR design where the maximum average torque is 16.2 Nm. This research will give benefit to mankind and society in term of environment protection and energy consumption.</p>

Design of a novel dual flux modulation machine with consequent-pole spoke-array permanent magnets in both stator and rotor

In this paper, a novel dual flux modulation (DFM) machine with consequent-pole spoke-array permanent magnets (PMs) in both stator and rotor is proposed to achieve a larger torque density than regular flux modulation machines. The stator has two portions of PMs, one is set next to the stator slot with circumferential magnetization, and the other is inserted between the stator yoke and flux bridge with radial magnetization. The rotor has consequent-pole spoke-array PMs and alternative flux bridges. The proposed DFMPM machine can be regarded as the combination of the flux switching PM (FSPM) machine and vernier PM (VPM) machine. First, the structure and operational principle are introduced. Then, the proposed 12-stator-slot/10-rotor-tooth dual flux modulation permanent magnet (DFMPM) machine is compared with the FSPM machine and VPM machine in terms of flux lines distribution, back-electromotive force (EMF), cogging torque and average torque. Finally, the four proposed DFMPM machines are optimized for maximum average torque and minimum ripple torque considering the effects of split ratio, slot opening ratio, PM depth, PM angle and iron angle.

Flux Switching Permanent Magnet Motor using Segmented Outer Rotor Structure for Electric Scooter

Flux switching motor is a type of electric machine that locates both flux source and armature windings on the stator leaving its rotor a simple piece of iron. This machine was developed by combining the toothed stator structure of induction machine and the toothed rotor structure of switched reluctance machine together. Furthermore, it has three types of flux sources which include permanent magnet. Conventionally, the toothed kind of rotor has dominated machines rotor design and has been known for high manufacturing cost and iron loss, resulting to low performance. This calls for worry and the need to overcome it and also reduce the manufacturing cost while securing high torque. This paper presents flux switching permanent magnet motor employing segmented outer rotor for high torque capability. 2D-FEA using JMAG to investigate the motor characteristics in terms of flux linkage, Induce back-emf, cogging torque, maximum average torque and efficiency. Finally, preliminary results and comparison revealed that motors employing segmented rotor are capable of higher torque than conventional toothed rotor.

A New High-Efficiency Double-Stator Split-Pole Permanent-Magnet Vernier Machine with Flux-Focusing Topology

Permanent-magnet vernier machines (PMVMs) have attracted much attention for their high efficiency and output torque in low-speed application. However, the conventional PMVM suffers from the problems of low power factor and high cogging torque. In this paper, a double-stator flux-focusing split-pole permanent-magnet vernier machine (SP-PMVM) with low cogging torque and high power factor has been proposed. The split-pole topology in the vernier motor has been used mainly to modulate the magnetic flux in this paper, although the stator teeth are used for this purpose in some cases. The newly-proposed SP-PMVM topology is characterized by reduced flux leakage through using a flux-focusing topology and staggering approximately half of the pitch angularly between the inner stator and outer stator. Firstly, the vernier principle of the proposed SP-PMVM has been investigated by analytical methods. Secondly, a 12-slot-stator and 22-pole-pair-rotor SP-PMVM has been optimized with the goal of maximum average steady-state torque and the minimum cogging torque and ripple. Thirdly, the overall performance of the newly-proposed SP-PMVM has been analyzed as compared with the conventional PMVM. The results verify that the SP-PMVM can provide higher power factor, higher output torque and lower cogging torque than that of the conventional PMVM in low-speed application.

Contribution of Current Harmonics to Average Torque and Torque Ripple in Switched Reluctance Machines

This paper investigates the contribution of current harmonics to average torque and torque ripple in switched reluctance machines. In order to account for the magnetic saturation under different current amplitudes and waveforms, the self-inductances are obtained by finite element calculation using frozen permeability method and subsequently used in the analytical derivation of an instantaneous torque equation based on the Fourier series analyses. Five different current waveforms are also considered in order to identify the contribution of current harmonics. It is found that the average torque is mainly contributed by the dc, first, and second current harmonics. Meanwhile, the fourth and fifth current harmonics have high influence on the torque ripple but much lower contribution to the average torque. In addition, the optimization of current waveforms in terms of the maximum average torque under a given RMS current is also discussed. All analytical analyses are validated by direct nonlinear finite element and experimental results.

Multiresponse optimization to improve the torque behavior of an outer-rotor permanent-magnet machine using gray relational analysis based on the Taguchi method

The torque behavior of an outer-rotor surface-mounted permanent-magnet machine is improved by identifying seven pertinent design variables, including rotor height. The optimal design variables are revealed by analyzing 18 experiments determined by the Taguchi method for the minimum torque ripple, minimum total harmonic distortion of the induced voltage, and maximum average torque. In addition, the optimal design variables are obtained very quickly by using gray relational analysis based on the Taguchi method with the single response of the gray relational grade instead of multiple responses. A considerable amount of multiresponse improvement is achieved according to the results of the two optimizations. Performance improvements of 20.6%, 32.0%, and 24.5% are obtained for the average torque, the torque ripple, and the total harmonic distortion of the back-EMF, respectively.

페라이트 영구자석을 갖는 고속 매입형 영구자석 전동기의 특성해석 및 설계

We propose an interior permanent magnet syhchronous motor (IPMSM) with arc-shape ferrite permanent magnets (PMs) as a substitute for the rare-earth permanent magnet, and determine its optimal design through parametric study. First, we use 2D finite element analysis to analyze 4-poles and 6-slots initial model according to performance requirements and design parameters. The current angle of the maximum average torque considered in the analysis is different compared with the current angle of the minimum torque ripple. Thus, the parametric study for optimal rotor design is performed by varying the thickness and the offset radius of the PMs according to current angle. In particular, a narrow bridge is required in conventional IPMSM for reducing flux leakage; however, the increase in cogging torque in the analysis model saturates the narrow bridge (large offset radius). Therefore, we suggest an appropriate shape considering limiting conditions such as DC link voltage, average torque, torque ripple, and cogging torque taking into account performance requirements.

Micro-drilling of Ti–6Al–4V alloy: The effects of cooling/lubricating

This paper presents a series of experimental investigations of the effects of various machining conditions [dry, flooded, minimum quantity lubrication (MQL), and cryogenic] and cutting parameters (cutting speed and feed rate) on thrust force, torque, tool wear, burr formation, and surface roughness in micro-drilling of Ti–6Al–4V alloy. A set of uncoated carbide twist drills with a diameter of 700μm were used for making holes in the workpiece material. Both machining conditions and cutting parameters were found to influence the thrust force and torque. The thrust force and torque are higher in cryogenic cooling. It was found that the MQL condition produced the highest engagement torque amplitude in comparison to the other coolant–lubrication conditions. The maximum average torque value was obtained in the dry drilling process. There was no substantial effect of various coolant–lubrication conditions on burr height. However, it was observed that the burr height was at a minimum level in cryogenic drilling. Increasing feed rate and decreasing spindle speed increased the entry and exit burr height. The minimum surface roughness values were obtained in the flood cooling condition. In the dry drilling process, increased cutting speed resulted in reduced hardness on the subsurface of the drilled hole. This indicates that the surface and subsurface of the drilled hole were subject to softening in the dry micro-drilling process. The softening at the subsurface of drilled holes under different cooling and lubrication conditions is much smaller compared to the dry micro-drilling process.

Fundamental characteristics and first prototype of a novel claw pole type half-wave rectified variable field flux motor

Purpose– Recently, considerable attention has been attracted to the development of the new concept motor for EV or HEV. Wider torque and speed controllable operating range and high efficiency under driving area are needed for traction motor. The purpose of this paper is to realize the new concept variable field flux motor with claw pole rotor and brushless robust structure for high-speed range.Design/methodology/approach– In the previous paper, the authors proposed a half-wave rectified brushless variable field flux method with a diode inserted into the field winding. This paper presents a designing for a novel claw pole rotor type motor using the variable field flux method (CP-HVFM). The claw pole type rotor has simple and robust structure for high-speed operation. This paper describes a first prototype design result for CP-HVFM using 3D-FEM. And the authors report the torque and efficiency characteristic results using 3D-FEM.Findings– The authors have studied the designing for CP-HVFM using 3D-FEM. The designed prototype CP-HVFM reached a rated power of 2 kW or more at a rated speed 1,800 rpm under design restrictions of experimental equipment and initial specifications. In addition, the authors found the ratio of the tip and root embrace of the claw pole shape for maximum average torque and minimum torque ripple. Finally, the authors revealed an influence of the armature current on the torque and the efficiency characteristic results for the designed prototype CP-HVFM using 3D-FEM.Originality/value– The half-wave rectified brushless variable field flux method proved to be effective for the claw pole rotor type motor. And also the authors found the best claw pole shape for torque characteristic. This results are applied to another concept motor for EV or HEV.

Comparison of Partitioned Stator Switched Flux Permanent Magnet Machines Having Single- or Double-Layer Windings

A novel type of partitioned stator switched flux permanent magnet (PS-SFPM) machine with either single-layer or double-layer windings is developed in this paper. The proposed PS-SFPM machines have two stators, which separately accommodate the armature windings and the PMs, and between which is the rotor made of iron pieces, while the number of stator poles with PMs may be equal or half of that with armature windings. All the machines are optimized under fixed copper loss for maximum average torque by genetic algorithm. Their electromagnetic performances are compared, such as open-circuit flux-linkages and back-electromotive forces (EMFs), cogging torque, static torque waveforms, average torque against current, PM utilization ratio, and flux-weakening performances. The results show that due to more PM usage and higher open-circuit back-EMF, the PS-SFPM machines having the number of stator poles with PMs the same as that with armature windings exhibit higher average torque, irrespective of the winding topologies, either single-layer or double-layer windings. However, the single-layer winding PS-SFPM machines having the number of stator poles with PMs half of that with armature windings have the best PM usage and the highest ratio of average torque to PM volume, as well as good flux-weakening capability. A prototype machine is manufactured and tested to validate the analyses.

An experimental comparison of the relative benefits of work and torque assistance in ankle exoskeletons.

Techniques proposed for assisting locomotion with exoskeletons have often included a combination of active work input and passive torque support, but the physiological effects of different assistance techniques remain unclear. We performed an experiment to study the independent effects of net exoskeleton work and average exoskeleton torque on human locomotion. Subjects wore a unilateral ankle exoskeleton and walked on a treadmill at 1.25 m·s(-1) while net exoskeleton work rate was systematically varied from -0.054 to 0.25 J·kg(-1)·s(-1), with constant (0.12 N·m·kg(-1)) average exoskeleton torque, and while average exoskeleton torque was systematically varied from approximately zero to 0.18 N·m·kg(-1), with approximately zero net exoskeleton work. We measured metabolic rate, center-of-mass mechanics, joint mechanics, and muscle activity. Both techniques reduced effort-related measures at the assisted ankle, but this form of work input reduced metabolic cost (-17% with maximum net work input) while this form of torque support increased metabolic cost (+13% with maximum average torque). Disparate effects on metabolic rate seem to be due to cascading effects on whole body coordination, particularly related to assisted ankle muscle dynamics and the effects of trailing ankle behavior on leading leg mechanics during double support. It would be difficult to predict these results using simple walking models without muscles or musculoskeletal models that assume fixed kinematics or kinetics. Data from this experiment can be used to improve predictive models of human neuromuscular adaptation and guide the design of assistive devices.

토크 측정과 시차주사열량계를 이용한 수용성 고분자 화합물의 하이드레이트 저해 성능 평가

본 연구에서는 토크 측정과 고압 시차주사 열량계를 이용하여 pyrrolidone, caprolactam, acrylamide 계열 수용성 고분자들의 하이드레이트 저해 성능을 평가하였다. 실험 결과, 세 종류의 고분자가 모두 동역학적인 하이드레이트 생성억제제 효과를 나타내는 것으로 확인되었으며, 특히 0.5 wt% polyvinylcaprolactam (PVCap)의 경우 34.4분의 하이드레이트 유도 시간, 15.9 K의 subcooling 성능을 보이며 12.3 분, 6.0 K의 순수 물 시스템보다 월등한 저해 성능을 나타내었다. 0.5 wt% polyvinylpyrrolidone (PVP)의 경우 중간 정도의 저해 성능을 보였으며, polyacrylamide-co-acrylic acid partial sodium salt (PAM-co-AA)의 경우 각각 0.5 wt%와 5.0 wt%의 농도에서 미미한 하이드레이트 저해 성능을 보였다. 반면에 생성된 하이드레이트 입자의 성장속도와 생성 양에서는 PAM-co-AA가 PVCap과 더불어 가장 월등한 저해 효과를 나타내었다. 또 다른 주요 성능 평가 요소 중 하나인 토크 변화의 경우에는 PVCap이 평균 토크 6.4 N cm로 가장 좋은 성능을 보였으며, 0.5 wt%의 PAM-co-AA 시스템이 평균 7.2 N cm의 값으로 그 뒤를 이었다. 고압 시차주사 열량계를 이용한 수용성 고분자 물질의 저해 성능 평가 실험의 결과는 autoclave 실험의 결과와 유사하였다. PVCap을 첨가한 경우 하이드레이트가 생성되기까지의 유도시간이 가장 길어서 저해성능이 뛰어난 것을 확인하였다. In this work, hydrate inhibition performance of water-soluble polymers including pyrrolidone, caprolactam, acrylamide types were evaluated using torque measurement and high pressure differential scanning calorimeter (HP <TEX>${\mu}$</TEX>-DSC). The obtained experimental results suggest that the studied polymers represent the kinetic hydrate inhibition (KHI) performance. 0.5 wt% polyvinylcaprolactam (PVCap) solution shows the hydrate onset time of 34.4 min and subcooling temperature of 15.9 K, which is better KHI performance than that of pure water - hydrate onset time of 12.3 min and subcooling temperature of 6.0 K. 0.5 wt% polyvinylpyrrolidone (PVP) solution shows the hydrate onset time of 27.6 min and the subcooling temperature of 13.2 K while polyacrylamide-co-acrylic acid partial sodium salt (PAM-co-AA) solution shows less KHI performance than PVP solution at both 0.5 and 5.0 wt%. However, PAM-co-AA solution shows slow growth rate and low hydrate amount than PVCap. In addition to hydrate onset and growth condition, torque change with time was investigated as one of KHI evaluation methods. 0.5 wt% PVCap solution shows the lowest average torque of 6.4 N cm and 0.5 wt% PAM-co-AA solution shows the average torque of 7.2 N cm. For 0.5 wt% PVP solution, it increases 11.5 N cm and 5.0 wt% PAM-co-AA solution shows the maximum average torque of 13.4 N cm, which is similar to the average torque of pure water, 15.2 N cm. Judging from the experimental results obtained by both an autoclave and a HP <TEX>${\mu}$</TEX>-DSC, the PVCap solution shows the best performance among the KHIs in terms of delaying hydrate nucleation. From these results, it can be concluded that the torque change with time is useful to identify the flow ability of tested solution, and the further research on the inhibition of hydrate formation can be approached in various aspects using a HP <TEX>${\mu}$</TEX>-DSC.

Performance Analysis of Synchronous Reluctance Machines Having Nonoverlapping Concentrated Winding and Sinusoidal Bipolar With DC Bias Excitation

This paper describes the operation principle and analyzes the electromagnetic performance of synchronous reluctance (SynR) machines having the structure of switched reluctance machines but excited by an ac sinusoidal current with dc bias, i.e., salient-pole SynR with nonoverlapping concentrated windings and a dc bias excitation. Under such excitation, these machines become similar to permanent magnet (PM) counterparts. The dc bias, which is equivalent to the PM excitation, produces back electromotive force (EMF) in the ac coils as well as cogging torque. Thus, injecting the ac coils by sinusoidal currents results in output torque on the machine shaft. The produced back EMF and cogging torque, and torque ripple magnitudes and periods, as well as the optimal ac current angle and the ac/dc current density ratio, strongly depend on the winding connection configuration. The maximum average torque can be achieved when the ac/dc current density ratio is 2 and the symmetrical winding connection, which results in a lower torque ripple, is employed. A prototype machine is built and tested to confirm the analyses and conclusions.

Multi-Objective Differential Evolution Based PerformanceOptimisation for Switched Reluctance Motor Drives

The simple structure, low manufacturing cost, rugged behavior, high torque per unit volume, and wide torque-speed range make a switched reluctance motor (SRM) very attractive for industrial applications. However, these advantages are overshadowed by its inherent high torque ripple, acoustic noise, and difficulty to control. The controlled parameters in SRM drives can be selected as the turn-on angle, the turn-off angle, and the current reference. This paper investigates the problem of optimal control parameters considering the maximum average torque, minimum copper losses, and minimum torque ripple as the main objectives in SRM drives. The use of evolutionary algorithms (EAs) to solve problems with multiple objectives has attracted much attention recently. Differential evolution (DE) is an EA that was developed to handle optimization problems over continuous domains. A multiobjective DE (MODE) technique is introduced here to find the optimal firing angles under multiple operating conditions. The simulation results carried out on a 4-phase 8/6 pole SRM show that the proposed MODE can be a reliable alternative for generating optimal control in the multiobjective optimization of SRM drive systems.

Structure and motion analyses of the sails of Chinese Great Windmill

This study is to conduct analyses of the structure and operation of the sail of the Chinese Great Windmill based on the results of a reconstruction project of the vertical shaft type wind-power Chinese square-pallet chain-pumps during 2004–2006. According to the tests and analyses, the motion of the sail can be divided into three regions during a windmill cycle. Region I (the sail is positioned at the 1st limit position, ∅) and II (the sail is positioned at the 2nd limit position, λ) are both propelled but Region III is not. The hanging of the sail is an important aspect of installing (or starting) the Great Windmill. The length of the sheet and the point at which the end of the sheet is tied sets the sail at an optimal angle and are the deciding factors that generate greater work torque in the Great Windmill. If the sheet is tied on a crossing bar, when ∅ = 12.7 °, and λ = 116.3 °, it can obtain the maximum average torque (average torque factor = 2.263). If the sail is not constrained by the geometric relationship, the resulting maximum average torque (average torque factor = 2.271) can be derived using ∅ = 18.1 °, λ = 120.8 °.

Torque, myoeletric sygnal and heart rate responses during concentric and eccentric exercises in older men

The literature reports that the eccentric muscular action produces greater force and lower myoelectric activity than the concentric muscular action, while the heart rate (HR) responses are bigger during concentric contraction. To investigate the maximum average torque (MAT), surface electromyographic (SEMG) and the heart rate (HR) responses during different types of muscular contraction and angular velocities in older men. Twelve healthy men (61.7±1.6 years) performed concentric (C) and eccentric (E) isokinetic knee extension-flexion at 60º/s and 120º/s. SEMG activity was recorded from vastus lateralis muscle and normalized by Root Mean Square - RMS (µV) of maximal isometric knee extension at 60º. HR (beats/min) and was recorded at rest and throughout each contraction. The data were analyzed by the Friedman test for repeated measures with post hoc Dunn's test (p<0.05). The median values of MAT (N.m/kg) was smaller and the RMS (µV) was larger during concentric contraction (C60º/s=2.80 and 0.99; C120º/s=2.46 and 1.0) than eccentric (E60º/s=3.94 and 0.85; E120º/s=4.08 and 0.89), respectively. The HR variation was similar in the four conditions studied. The magnitude of MAT and RMS responses in older men were dependent of the nature of the muscular action and independent of the angular velocity, whereas HR response was not influenced by these factors.

Mechanical effects of third-order movement in self-ligated brackets by the measurement of torque expression

Axial rotation of orthodontic wire produces buccal or lingual root movement and is often referred to as third-order movement or "torque expression." The objective of this study was to quantify torque expression in 3 self-ligation bracket systems (Damon Q, Ormco, Orange, Calif; In-Ovation R, GAC, Bohemia, NY; and Speed, Strite Industries, Cambridge, Ontario, Canada) during loading and unloading. A stepper motor was used to rotate a wire in a fixed bracket slot from -15° to 63° in 3° increments, and then back to -15°. The bracket was mounted on top of a load cell that measured forces and moments in all directions. Damon's and In-Ovation's maximum average torque values at 63° were 105 and 113 Nmm, respectively. Many Speed brackets experienced premature loss of torque between 48° and 63°, and the average maximum was 82 Nmm at 54°. The torque plays for Damon, In-Ovation, and Speed were 11.3°, 11.9°, and 10.8°, respectively. Generally, In-Ovation expressed the most torque at a given angle of twist, followed by Damon and then Speed. However, there was no significant difference between brackets below 34 Nmm of torque. From a clinical perspective, the torque plays between brackets were virtually indistinguishable.

Multi-Objective Optimization Design of In-Wheel Switched Reluctance Motors in Electric Vehicles

The method of the optimization design with multi-objectives for switched reluctance motors (SRMs) in electric vehicles (EVs) is proposed in this paper. It is desired that electric motors for EVs have high torque, high efficiency, and high torque density. Thus, the developed optimization function is selected as the correct compromise between the maximum average torque, maximum average torque per copper loss, and maximum average torque per motor lamination volume, by using three weight factors and three base values. The stator and rotor pole arc angles are selected as the optimized variables. Furthermore, the authors also discuss the design requirements and some constraints on the optimization design. The results of the optimization design show that the proposed method meets the requirements of EVs on electric motors well. A prototype of the optimally designed in-wheel SRM for EVs has been manufactured. This paper provides a valuable method to implement the optimal design of SRMs for EVs.

Optimal Control Method of Motoring Operation for SRM Drives in Electric Vehicles

This paper presents three criteria for evaluating the motoring operations of switched reluctance motor (SRM) drives for electric vehicles (EVs). They imply motoring torque, copper loss, and torque ripple, respectively. The effects of the turn-off and turn-on angles on these criteria are investigated under hysteresis current control. To fulfill the best motoring operation, consequently, the multiobjective optimization function is developed by using three weight factors and three groups of base values: the correct balance between the maximum average torque, the maximum average torque per root mean square current, and the maximum torque smoothness factor. The study in this paper shows that the turn-off and the turn-on angles can be optimized to maximize the developed multiobjective function. In addition, the control method for the best motoring operation of SRM drives in EVs is proposed. In this method, two angular controllers are proposed to automatically tune the turn-off and turn-on angles to obtain high motoring torque, low copper loss, and low torque ripple. Simulations and experimental results have demonstrated the proposed optimal control method. Therefore, this paper offers a valuable and feasible approach for implementing the best motoring operation of SRM drives for EVs.

Variabilidade da freqüência cardíaca em repouso e resposta da freqüência cardíaca e do torque durante exercício isométrico máximo de flexão do joelho em dois voluntários: um com padrão de vida sedentário e outro ativo: relato de casos

The purpose of the present study was to investigate the heart rate variability (HRV) at rest and the magnitude of the heart rate response and the maximum average torque (MAT) during isometric exercise with maximum voluntary contraction (MVC) during knee flexion at 30°, 45° e 60° angles. One sedentary volunteer (26 years of age) and another active (22 years of age), were submitted to a isometric exercise test involving knee flexion with MVC, for 10 seconds period at sitting position on an electronic dynamometer, which provided data from MAT. The HRV was calculated from RMSM and RMSSD indexes of R-R intervals obtained for 6 minutes at rest in seat position. The variation of HR (AHR) was calculated by the difference between HR observed at 10s of maximum voluntary contraction and the average obtained during a period of 60s immediately before the beginning of exercise. The sedentary and active volunteers showed the following results: during rest: heart rate = 66 and 73 beats/ min; RMSM = 61 and 39 ms; RMSSD = 47 and 35 ms, respectively. During exercise: variation of heart rate (beats/min) at 30° (34 and 17), at 45° (33 and 21) and at 60° (31 and 16), respectively. These results suggest that, a) physical activity might change the autonomic modulation over the heart as well as the torque magnitude; b) The articular angle does not interferes at the vagal withdrawal in the beginning of the isometric exercise with maximum voluntary contraction, however it seems to influence the torque magnitude.