Average Torque Research Articles

Fully Integrated Multilevel Power Converter for SRM Drive With Charging Capabilities (G2V) for Electric Vehicle Application

This article presents a fully integrated multilevel power converter topology (IML-PCT) with integrated battery charging capability for a switched reluctance motor (SRM) drive. The battery charger is integrated within the IML-PCT, which eliminates the requirement of any additional module for charging purposes. The proposed IML-PCT applies higher energization and de-energization voltages during the driving mode, which leads to an enhanced constant torque region for SRM drive. For the battery charging mode, the proposed IML-PCT exhibits the characteristics of an onboard charger (OBC) capable of charging the battery energy storage system directly via a standard ac outlet. The OBC functionality is realized by reconfiguring the proposed IML-PCT into an interleaved bridgeless boost power factor correction circuit (IBB-PFCC). The charging inductors for IBB-PFCC are realized by reutilizing/reconfiguring all the windings of the four-phase SRM. Also, with the proposed IBB-PFCC configuration, the charging current in the windings leads to an average zero torque production. Thus, the rotor is kept stationary during battery charging mode without any external braking mechanism. Detailed simulation and experimental studies on a 1.1-kW laboratory prototype four-phase SRM demonstrate ac level-1 (120 V/240 V) charging performance of the proposed IML-PCT.

Design and Analysis of an Asymmetric Spoke and Delta-Shape Interior Permanent Magnet Synchronous Machine

This paper proposes a design of an asymmetric spoke and delta-shape interior permanent magnet (AIPM-P) synchronous machine for electric vehicles that use the magnetic-field-shifting (MFS) technique to improve the average torque and reduce torque ripples. The asymmetry of the AIPM-P is due to the asymmetric rotor structure, asymmetric permanent magnet (PM) placement, and asymmetric flux barriers (AFB). Due to this asymmetry, the MFS is utilized, which decreases the current angle difference between the peak PM torque ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{PM}$ </tex-math></inline-formula> ) and reluctance torque ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T_{r}$ </tex-math></inline-formula> ) components. In the delta-shape, the bar magnet helps reduce the d-axis inductance, which helps in increasing the reluctance torque, ultimately increasing synthetic torque. Furthermore, the combination of delta-shape and spoke shape PM makes the novel hybrid layer structure that improves the average torque. The proposed AIPM-P is then compared with the conventional designs in the literature having the same stator and rotor radius, with a 4-pole and 24-slot combination. The open circuit, on-load characteristics, efficiency, copper, and iron loss maps of the proposed and conventional designs are investigated and compared. Compared to the conventional designs, the proposed AIPM-P synchronous machine has high efficiency and a good torque profile, which is suitable for EV applications.

Determining the Control Objectives of a Switched Reluctance Machine for Performance Improvement in Generating Mode

This paper presents a methodology to determine the control objectives of conduction angle control in generating mode of operation in a switched reluctance machine. First, the performance in motoring mode of control is compared with generating mode for different operating points. Then, the key optimization objectives are established to improve a switched reluctancemachine's performanceingenerating mode. A multi-objective optimizer is used to select the conduction angles. The proposed generating-specific objectives are maximizing source current per torque and minimizing torque ripple. These objectives are then compared with the motoring-specific objectives, such as maximizing average torque and minimizing torque ripple for a wide speed range. Finally, the proposed generating objectives have been validated experimentally using a three-phase 12/8 SRM.

Desempenho de um motor diesel utilizando diferentes misturas de biodiesel e configurações de injeção

ABSTRACT Diesel cycle engines are widely used in a wide range of agricultural activities. Recently, with the increasing use of biodiesel mixed with petroleum diesel and the introduction of pollutant emission regulations for agricultural and road machinery, there has been a growing migration from mechanical to electronic fuel injection systems. In this experiment, the primary aim was to verify the behavior of a diesel engine, electronically managed, with controlled variation of the fuel feeding system parameters (injection time and volume injected). A four-cylinder agricultural tractor with a turbocharged engine and a common rail electronic fuel injection system was used. Tests with diesel B10 and blends of 20 and 30% biodiesel were carried out, all with 10 ppm of sulfur and the injection system electronically reprogrammed. The tests were performed under full engine load from 1,300 to 2,000 rpm. The torque, power and fuel consumption were evaluated. Advancing the injection point increased the power and decreased the specific fuel consumption for all fuels. The greater amount of injected fuel provided average power gain of up to 14.96% and average torque gain of 15.50%.

The investigation of isokinetic knee strength and muscle balance of taekwondo and wrestling athletes

Taekwondo and wrestling are two different Olympic combat sports that need lower extremity strength in different ways. During the training process that lasts for many years, the harmony in the leg muscles may be dissimilar. This study aims to determine (1) the knee extension and flexion strength values of elite taekwondo and wrestling athletes with similar physical and demographic characteristics and (2) the muscle balances formed after long-term taekwondo and wrestling training. This study was conducted with the voluntary participation of 20 elite taekwondo and wrestling athletes (age: 20.4±1.27 years; experience: 10.6±1.98 years; height 176.65±5.86 cm; weight 72.96±6, 96 kg; BMI 23.35±1.47 kg/m2). Following the determination of the demographic and physical characteristics of the athletes, their isokinetic knee strengths were examined at an angular velocity of 600/s and compared between taekwondo and wrestling. Accordingly, the differences between the extension relative and average peak torque strengths of the athletes were significant in favour of the taekwondo players in the extension strength. On the other hand, the hamstring/quadriceps strength ratios of the taekwondo athletes were lower (p0.05). The study results showed that taekwondo players have higher extension strength. In the observed groups, it was determined that the muscular asymmetry occurred at different levels because of the adaptation specific to the sport type. Taekwondo trainings allows more balanced hamstring/quadriceps muscle harmony than wrestling. It is recommended to develop training programs in which the flexor muscles are trained against muscular imbalances in wrestling.

FEA Based Design of Outer Rotor BLDC Motor for Battery Electric Vehicle

Due to enormous advantages, BLDC motors have been identified for the design in various applications. With its good power density, this motor is being used by the automobile industry. The paper aims to design the motor for the battery electric vehicle. The major challenge of the BLDC motor is to reduce torque ripples which appear because of high cogging torque. Torque ripple results in acoustic noise and vibrations in the battery electric vehicle which badly affects the performance of the vehicle. The cogging torque and efficiency are characterized by a parametric technique with varying pole embrace factor and magnetic thickness. The selection of optimum values of rotor pole embrace factor and magnetic thickness has a significant role in the reduction of cogging torque. The Ansys Maxwell tool helps in the optimum designing of the motor by mitigating the torque ripples and thus increasing the average torque. The proposed model has 5.7% better efficiency in comparison to the base model and has a small number of torque ripples.

Modified Synchronous Reluctance Motor for Electric Vehicle Applications

This research article explores a comparative investigation on synchronous reluctance motor (SyRM) for electrified transportation system. The SyRM has salient features like absence of magnet, singly excited but it shrinks its application due to high torque ripple aspects. The novelty of the proposed work is the rib and flux barrier of the rotor in SyRM are modified in order to achieve low torque ripple without affecting the average torque of the motor. Analysis in the electromagnetic domain infers to enhance the sustainability and reliability of the transportation system. So, it results in the reduction of torque ripple, leads to minimize the acoustic noise. This article delivers the geometric optimization to achieve SyRM with low torque ripple. The finite elemental analysis infers the torque ripple, losses and unbalanced magnetic force for SyRM. The notched and round barrier type SyRM with one-layer results acts as superior motor among different layers and geometries. The experimental arrangement is carried out in real time vehicle and the results are obtained for different loading conditions and validated with FEA findings.

Methods for Reducing Cogging Force in Permanent Magnet Machines: A Review

Permanent magnet (PM) machines inevitably suffer from cogging force, which does not contribute to the average output torque (force) but contributes as a type of torque (force) ripple. This paper provides an overview of the cogging force reduction methods for different types of PM machines. First, a systematic and comprehensive categorization of different kinds of cogging force reduction methods is given according to the reduction principle. Then, the cogging force reduction methods for different types of PM machines are analyzed and discussed based on the categorization. Finally, according to the versatility and feasibility of the cogging force reduction methods, practical methods are recommended for different types of PM machines. The categorization, analyses, and recommendations presented in the paper are useful for the design of different types of PM machines with the requirement of cogging force reduction or output torque (force) ripple suppression.

Design and biomechanical analysis of a self-force source power-assisted knee orthotics actuated by liquid spring

A micro silicone oil liquid spring was designed and manufactured in this article. The performance of the liquid spring was studied by simulation analysis and mechanical test. A self-force source power-assisted knee orthosis was designed based on the liquid spring. This power-assisted knee orthosis can convert the kinetic energy of knee flexion into the elastic potential energy of liquid spring for storage, and release elastic potential energy to generate assisted torque which drives the knee joint for extension. The results showed that the average maximum reset force of the liquid spring was 1 240 N, and the average maximum assisted torque for the knee joint was 29.8 N·m. A musculoskeletal multibody dynamic model was used to analyze the biomechanical effect of the knee orthosis on the joint during knee bending (90°knee flexion). The results showed that the power-assisted knee orthosis could effectively reduce the biomechanical load of the knee joint for the user with a body weight of 80 kg. The maximum forces of the femoral-tibial joint force, patellar-femoral joint force, and quadriceps-ligament force were reduced by 24.5%, 23.8%, and 21.2%, respectively. The power-assisted knee orthosis designed in this article provides sufficient assisted torque for the knee joint. It lays a foundation for the subsequent commercial application due to its small size and lightweight.

Performance evaluation of a new modular split‐tooth permanent magnet‐assisted switched reluctance motor

AbstractThis study elaborates upon a new modular split‐tooth permanent magnet‐assisted switched reluctance motor (MSTPM‐SRM). In the proposed topology, the stator comprises six modular E‐cores in which the middle poles are split into two teeth. Two permanent magnets (PMs) are placed between each module's middle and side poles. Primarily, the proposed topology is introduced. Next, the principle of operation of the proposed topology are elucidated, and the magnetic equivalent circuit analysis is adopted in order to validate the operational basics. It is proved that the embedded PMs significantly increase the air‐gap's flux density and adjusts the poles' flux density. The flux density distributions, static, and steady‐state characteristics of the proposed MSTPM‐SRM motor and its PMless counterpart are extracted by utilising 2‐D finite element analysis. It is illustrated that the average torque of the proposed MSTPM‐SRM is dramatically increased compared to its PMless counterpart, especially at high excitation currents. Furthermore, the cogging torque analysis is done and it is shown that the proposed structure has approximately zero cogging torque. Finally, a prototyping version of the proposed motor is fabricated, and the experimental results are elicited. It is shown that the experimental results endorse the simulation results.

Design Optimization of a New Hybrid Excitation Drive Motor for New Energy Vehicles

In this paper, a new hybrid excitation drive motor (HEDM) was proposed to solve the problem of an uncontrollable magnetic field of a permanent magnet motor. The rotor part of the motor was composed of a combined magnetic pole permanent magnet rotor and a brushless electric claw rotor, in which the combined magnetic pole permanent magnet rotor has a parallel magnetic circuit structure. According to the characteristics of the parallel rotor structure, the equivalent magnetic circuit model was established, and the no-load leakage flux coefficient of the claw pole rotor was calculated. The Taguchi method was used for objective optimization of the permanent magnet rotor structure. The distortion rate of no-load back electromotive force (EMF) was taken as the first optimization goal; the cogging torque and the average torque were taken as the second optimization goal; and the torque fluctuation coefficient was a constraint condition. The optimal parameter matching under the mixed horizontal matrix was obtained. The parameters of the claw pole were optimized by using the method of uniform variables, and the dimension parameters of the motor were obtained. Finite element analysis and prototype tests were carried out for the optimized motor structure. The rationality and feasibility of the new HEDM as a vehicle motor were verified, which provided a possibility for the application of the new energy vehicle drive motor field.

FEATURES OF THE FIELD WEAKENING MODE IN А SWITCHED RELUCTANCE MACHINE

The magnetic field weakening mode of electric machines is used in modern drives to extend the drive operational speed range when the power supply voltage is limited. In conventional electric drives, a real or fictitious flux control loop, established in a vector control system by using coordinate and phase transformations of corresponding variables, is used for attenuating the motor magnetic flux. Switched reluctance machines have certain design advantages over conventional electric machines; they feature high reliability and wide control possibilities. However, to realize these possibilities, appropriate control outputs should be generated, the choice of which depends on the operational speed range. Another peculiarity of these machines is that there is no separate magnetic flux stabilization or control circuit. The article considers the specific features pertinent to the switched reluctance machine operation in various speed ranges for adequately taking them into account in control algorithms. The studies were carried out using the electric drive simulation model in the MATLAB Simulink environment. It is shown that during the electric drive operation at its limit mechanical characteristic in the low-speed zone under the speed variation conditions, the phase flux linkage average value can be considered almost unchanged. However, control of the average torque carried out by changing the current limitation level is performed at the magnetic flux weakening background. It has been determined that during operation in a high-speed zone at invariable phase switching positions with the speed growing in a natural manner (i.e., without applying control actions), there is an excessive decrease in the flux linkage average value, which leads to a dramatic drop in the phase average torque. This drop can be compensated by progressively shifting the phase engagement position in the leading direction.

Cogging Torque Minimization of Surface-Mounted Permanent Magnet Synchronous Motor Based on RSM and NSGA-II

A high-end permanent magnet (PM) synchronous motor’s cogging torque is a significant performance measure (PMSM). During the running of the motor, excessive cogging torque will amplify noise and vibration. Therefore, the cogging torque must be taken into account while optimizing the design of motors with precise motion control. In this research, we proposed a local optimization-seeking approach (RSM+NSGA-II-LR) based on Response Surface Methodology (RSM) and Non-Dominated Sorting Genetic Algorithm-II (NSGA-II), which reduced the cogging torque of a permanent magnet synchronous motor (SPMSM). To reduce the complexity of optimization and increase its efficiency, the sensitivity analysis method was utilized to identify the structural parameters that had a significant impact on the torque performance. Second, RSM was utilized to fit the functional relationship between the structural parameters and each optimization objective, and NSGA-II was integrated to provide the Pareto solution for each optimization objective. The solution with a greater average torque than the initial motor and the lowest cogging torque was chosen, and a new finite element model (FEM) was created. On the basis of the sensitivity analysis, the structural factors that had the highest influence on the cogging torque were selected, and the RSM is utilized for local optimization to lower the cogging torque as much as feasible. The numerical results demonstrated that the optimization strategy presented in this study effectively reduced the cogging torque of the motor without diminishing the motor’s average torque or increasing its torque ripple.

Evaluation of Objective Functions for the Optimal Design of an Assistive Robot.

The number of individuals with upper or lower extremities dysfunction (ULED) has considerably increased in the past few decades, resulting in a high economic burden for their families and society. Individuals with ULEDs require assistive robots to fulfill all their activities of daily living (ADLs). However, a theory for the optimal design of assistive robots that reduces energy consumption while increasing the workspace is unavailable. Thus, this research presents an algorithm for the optimal link length selection of an assistive robot mounted on a wheelchair to minimize the torque demands of each joint while increasing the workspace coverage. For this purpose, this research developed a workspace to satisfy a list of 18 ADLs. Then, three torque indices from the literature were considered as performance measures to minimize; the three torque measures are the quadratic average torque (QAT), the weighted root square mean (WRMS), and the absolute sum of torques (AST). The proposed algorithm evaluates any of the three torque measures within the workspace, given the robot dimensions. This proposed algorithm acts as an objective function, which is optimized using a genetic algorithm for each torque measure. The results show that all tree torque measures are suitable criteria for assistance robot optimization. However, each torque measures yield different optimal results; in the case of the QAT optimization, it produces the least workspace with the minimum overall torques of all the joints. Contrarily, the WRMS and AST optimization yield similar results generating the maximum workspace coverage but with a greater overall torque of all joints. Thus, the selection between the three methods depends on the designer's criteria. Based on the results, the presented methodology is a reliable tool for the optimal dimensioning of assistive robots.

Average torque distribution strategy for low speed operation of three-phase SRM with low-resolution rotor position sensor

An average torque distribution (ATD) strategy for low-speed operation of three-phase switched reluctance motor (SRM) with hall-effect rotor position sensor, as well as a calibration method for the sensor, are proposed. The sensor can only detect unaligned and aligned positions of all phases, and these positions evenly divides an electrical cycle into six position sectors. These positions are fully utilized by shaping a phase current as a four-step waveform and controlling motor average torque in each sector. In commutation sectors, a motor average torque reference is distributed into two phase average torque references. The distribution is optimized offline to minimize torque ripple and copper losses based on the phase torque characteristics. Compared with the torque control schemes using square-wave current references, the proposal can greatly reduce torque ripple without or with only a small penalty on copper losses. Based on difference among the aligned position detection errors of the hall-effect sensor, a calibration procedure for the sensor is developed. This procedure can ensure the absolute value of the average of these errors less than the maximum difference among these errors without high-resolution position signal as reference. Experimental results demonstrate effectiveness of the proposed ATD strategy and the calibration.

Fatigue-induced changes in hamstrings’ active muscle stiffness: effect of contraction type and implications for strain injuries

PurposeHamstring strain injuries may occur due to differential fatigue and compromised mechanical properties among the hamstring muscles. We examined (1) the effect of fatigue on hamstrings active muscle stiffness, and (2) whether contraction type affects active muscle stiffness changes during a submaximal fatiguing task.MethodsNine healthy males completed 99 submaximal knee flexions in isometric (ISO), concentric (CON), and eccentric (ECC) conditions. We measured the knee flexor maximal voluntary torque (MVT) (pre/post), shear wave velocity (SWV) during contraction and transverse relaxation times (T2) (pre/post) in biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM) muscles.ResultsMVT decreased substantially after all conditions (− 18.4 to − 33.6%). The average relative torque sustained during the task was lower in CON than ISO and ECC, but absolute torque was similar. SWV interindividual responses were highly variable across muscles and contraction types. On average, BFlh SWV tended to increase in ISO (0.4 m/s, 4.5%, p = 0.064) but decreased in ECC condition (− 0.8 m/s, − 7.7%, p < 0.01). ST SWV decreased in CON (− 1.1 m/s, − 9.0%, p < 0.01), while it remained unchanged in ISO and ECC. SM SWV decreased in CON (− 0.8 m/s, − 8.1%, p < 0.01), but it was unaffected in ISO and variable in ECC.ConclusionFatigue has a differential effect on the mechanical properties of the constituent hamstring muscles, as measured with shear wave elastography, depending upon contraction type. We found preliminary evidence that BFlh is more fatigued than ST or SM during eccentric contractions, which may explain its susceptibility to strain injuries.

Reproducibility of isokinetic measures of the knee and ankle muscle strength in community-dwelling older adults without and with Alzheimer’s disease

BackgroundTo interpret changes of muscle strength in older adults with Alzheimer’s disease (AD), determining the reliability of outcome measures is necessary. Therefore, the purpose of the present study was to investigate the relative and absolute intra-rater reliability of concentric isokinetic measures of the knee and ankle muscle strength in community-dwelling older adults without and with AD in the mild and moderate stages.MethodsA methodological study was conducted. The participants were submitted to two isokinetic evaluations with an interval of three to seven days. The evaluations consisted of knee extension and flexion at 60°/s (five repetitions) and 180°/s (15 repetitions) and plantar flexion and dorsiflexion of the ankle at 30°/s (five repetitions). The measures of interest were peak torque, average peak torque and total work. The intraclass correlation coefficient two-way mixed model of a single-measure (ICC3,1), standard error of measurement (SEM) and minimal detectable change at the 95% confidence interval (MDC95) were calculated. The ICC3,1 was interpreted based on Munro’s classification. Standard error of measurement and MDC95 were analyzed in absolute and relative values (percentage of error [SEM%] and change [MDC95%]).ResultsA total of 62 older adults were included and allocated to the three groups: mild-AD (n = 22, 79.9 years, 15 female and seven male), moderate-AD (n = 20, 81.6 years, 15 female and five male) and without-AD (n = 20, 74.3 years, 10 female and seven male). The ICCs3,1 of the measures of knee were high/very high in the three groups (0.71–0.98). The ICCs3,1 of the measures of ankle were high/very high in the mild-AD group (0.78–0.92), moderate/high/very high in the moderate-AD group (0.63–0.93) and high/very high in the group without-AD (0.84–0.97). The measurements of knee extensors at 60°/s, knee extensors (peak torque and total work), with the exception of peak torque in the mild-AD group, and flexors (average peak torque) at 180°/s, and ankle dorsiflexors at 30°/s had the lowest of SEM% and MDC95% in the three groups.ConclusionConcentric isokinetic measures are reliable for the assessment of knee and ankle muscle strength in community-dwelling older adults without and with AD in the mild and moderate stages.

Design of high power density double‐stator permanent magnet synchronous motor

AbstractCompared with the traditional permanent magnet synchronous motor (PMSM), the double‐stator permanent magnet synchronous motor (DS‐PMSM) can utilise the internal space adequately and has high power density. In this study, the design method of this kind of motor will be researched. Different rotor magnetic circuit topologies are analysed while keeping the outer diameter of outer stator unchanged, and the rotor magnetic circuit topologies with higher power density are selected. Furthermore, the effects of pole‐arc coefficient and stator split ratio on the power density of the motor are analysed, so a high power density DS‐PMSM can be designed. On this basis, a kind of magnetic pole structure with unequal pole‐arc coefficient is proposed to solve the problem of large torque ripple in DS‐PMSM. Finally, the DS‐PMSM is investigated by the FEA, compared with the traditional single stator PMSM, the average torque of the DS‐PMSM is increased by 62.2%, and the torque ripple is only 3.2%.

Optimization of Torque Performance of Permanent Magnet Synchronous Motor Based on the Taguchi Method

In order to improve the driving capability of the permanent magnet synchronous motor (PMSM), this paper optimizes the stator slot and rotor optimization variables of PMSM with the average torque and torque ripple as the optimization objectives. Firstly, the sensitivity analysis is used to find out the optimization variables which have a greater influence on the optimization objective from the initial selection of optimization variables. Secondly, the Taguchi method and Finite element method (FEM) are used to derive the best combination of optimization variables. Finally, the initial and optimized FEM model is built. The results showed that the average torque of the motor was improved by 27.27% and the torque ripple is reduced by 46.99% after the optimization is done.

Investigation of Optimal Split Ratio of 6-Slot/2-pole High Speed Permanent Magnet Motor with Toroidal Winding

Split ratio, i.e. the ratio of stator inner diameter to outer diameter, has a closed relationship with electromagnetic performance of permanent magnet (PM) motors. In this paper, the toroidal windings with short end-winding axial length are employed in the 6-slot/2-pole (6s/2p) PM motor for high speed applications. The split ratio is optimized together with the ratio of inner slot to outer slot area, i.e. slot ratio, considering stator total loss (stator iron loss and copper loss). In addition, the influence of maximum stator iron flux density and tooth-tip on the optimal split ratio, slot ratio, and average torque is investigated. The analytical predictions show that when the slot ratio is 0.5, the maximum torque can be achieved, and the optimal split ratio increases with the decrease of slot ratio, as confirmed by the finite element (FE) analyses. Finally, some of predicted results are verified by the measured results of 6s/2p prototype motor with 0.5 slot ratio.