A wide-angle wave control method of reducing torque ripple for brushless DC motor

In order to deal with torque pulsation problem caused by traditional control method for brushless DC （BLDC） motor and to achieve high precision and good stability, a novel control strategy is proposed. Compared with the traditional control scheme, by using phase voltage as a control objective and making waveform of phase current approximately quasi-sinusoidal, torque ripple of BLDC motor is reduced from the original 14% to 3.4%, while toque is increased by 3.8%. Furthermore, by detecting zero-crossings of back electromotive force （BEMF） with non-conducting phases, sensorless control is realized. The new control strategy is simple. It can minimize torque ripple, increase torque, and realize sensorless control for BLDC motor. Simulation and experiments show good performance of BLDC motor by using the new control method.

Research on Torque-Angle Characteristic of Large Gap Magnetic Drive System

The principle and design method of the large gap magnetic drive system is studied in this work. The calculation model of the torque-angle characteristic in the large gap magnetic drive system driven by traveling wave magnetic field is established. The calculation model is computed by using MATLAB software, and the pattern of the system’s torque-angle characteristic is obtained by analyzing study results. These results indicate that: torque-angle characteristic and the driving torque of the system can be adjusted by changing the electric current of coil, the magnetization of permanent magnetic gear, the inner diameter of permanent magnetic gear, the coupling distance between electromagnet and permanent magnetic gear, the outer diameter of permanent magnetic gear, and the axial length of permanent magnetic gear.

Evaluation of Nasal and Temporal Anterior Chamber Angle with Four Different Techniques

Background: Anterior chamber angle (ACA) can be measured by many different techniques. In order for a technique to be a part of the routine eye examination, it has to be quick and easy in good agreement with gonioscopy both nasally and temporally. Aim: To investigate variation in ACA measurement between gonioscopy, van Herick technique, anterior segment optical coherence tomography (AS-OCT) and Sirius Scheimpflug-Camera both nasally and temporally. Method: The ACA of 50 eyes of 25 healthy subjects was measured with gonioscopy, van Herick technique, AS-OCT and Sirius Scheimpflug-Camera. The angle was measured both nasally and temporally. Results: No statistically significant difference could be found between gonioscopy, van Herick technique and AS-OCT either nasally or temporally. The Sirius Scheimpflug-Camera on the other hand showed statistically significant difference to gonioscopy (p < 0.0001) both nasally (p = 0.03, p = 0.001, p < 0.0001) and temporally (p = 0.0002, p = 0.001, p Conclusion: This study showed good agreement between three of the four techniques. ACA measurements obtained by the Sirius Scheimpflug-Camera should therefore not be considered interchangeable with those obtained by the remaining three methods.

An Improved DITC Control Method Based on Turn-on Angle Optimization

Switched reluctance motor(SRM)usually adopts Direct Instantaneous Torque Control(DITC)to suppress torque ripple.However,due to the fixed turn-on angle and the control mode of the two-phase exchange region,the conventional DITC control method has low adaptability in different working conditions,which will lead to large torque ripple.For this problem,an improved DITC control method based on turn-on angle optimization is proposed in this paper.Firstly,the improved BP neural network is used to construct a nonlinear torque model,so that the torque can be accurately fed back in real time.Secondly,the turn-on angle optimization algorithm based on improved GRNN neural network is established,so that the turn-on angle can be adjusted adaptively online.Then,according to the magnitude of inductance change rate,the two-phase exchange region is divided into two regions,and the phase with larger inductance change rate and current is selected to provide torque in the sub-regions.Finally,taking a 3-phase 6/20 SRM as example,simulation and experimental verification are carried out to verify the effectiveness of this method.

Detection of tracheal branching with computerized tomography:The relationship between the angles and age-gender

BACKGROUND The data obtained on the anatomical knowledge of the tracheobronchial system can be used for diagnosis,treatment and interventional interventions in areas such as anesthesia,thoracic surgery,pulmonary physiology.AIM To determine the tracheobronchial branching angles in pediatric and adult populations by using the multislice computed tomography(CT)and minimum intensity projection(MinIP)technique,which is a non-invasive method.METHODS Our study was carried out retrospectively.Patients who underwent contrast and non-contrast CT examination,whose anatomically and pathophysiologically good tracheobronchial system and lung parenchyma images were obtained,were included in the study.Measurements were made in the coronal plane of the lung parenchyma.In the coronal plane,right main bronchus-left main bronchus angle,right upper lobe bronchus-intermedius bronchus angle,right middle lobe bronchus-right lower lobe bronchus angle,left upper lobe bronchus-left lower lobe bronchus angle were measured.RESULTS The study population consisted of 1511 patients,753 pediatric(mean age:13.4±4.3;range:1-18 years)and 758 adults(mean age:54.3±17.3;range:19-94 years).In our study,tracheal bifurcation angle was found to be 73.3°±13.7°(59.6°-87°)in the whole population.In the pediatric group,the right-left main coronal level was found to be higher in boys compared to girls(74.6°±12.9°vs 71.2°±13.9°,P=0.001).In the adult group,the right-left main coronal level was found to be lower in males compared to females(71.9°±12.9°vs 75.8°±14.7°,P<0.001).CONCLUSIONS Our study,with the number of 1511 patients,is the first study in the literature with the largest number of patient populations including pediatric and adult demographic data,measuring the angle values of the tracheobronchial system using multislice CT and MinIP technique.Study data will not only be a guide during invasive procedures,but it can also guide studies to be done with imaging methods.

STRATEGY AND IMPLEMENTATION FOR HIGH-SPEED TORQUE ENHANCEMENT OF BRUSHLESS DC MOTOR

Serious commutation lag occurs when a Brushless DC Motor(BLDCM) operates at high speeds,and this leads to torque decline with ripple.In this paper,an advanced conduction control scheme is proposed which can accelerate the commutation and enhance the torque production remarkably.Besides,an on line adjusting algorithm based on the Golden Section Method is adopted to search the optimal advanced conduction angle.Simulation and experimental results verify the feasibility and effectivity of the scheme proposed.

导板与直丝弓矫治器相结合治疗AngleⅡ类低角型错

目的:探讨平面导板或斜面导板在直丝弓矫治技术治疗AngleⅡ低角型错中的应用。方法:选取AngleⅡ低角型错畸形患者20例为研究对象,采用上颌平面导板或斜面导板与直丝弓矫治技术相结合的治疗方法,比较治疗前后X线头影测量的变化。结果:矢状方向上,下颌骨位置前移,SNB、ANB、L6-Ptm明显改善;垂直方向上,MP-SN、MP-FH、L6-MP明显增加,差异均有统计学意义(P<0.05)。结论:AngleⅡ低角型错畸形治疗中,采用上颌平面导板或斜面导板与直丝弓矫治技术相结合的治疗方法,可获得满意的面部下1/3外形,有利合关系纠正,并缩短矫治疗程。

Analytical calculation of electromagnetic, torque for surface mounted permanent magnet brushless motors

With the air gap magnetic field distribution of surface mounted permanent magnet （PM） motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis （FEA）. In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.

Frequency domain polarization weighted ESPRIT method for bearing angle

The signal to noise ratio （SNR） of seismic waves is usually very low after long distance transmission. For this condition, to improve the bearing estimation capability in the low SNR, a frequency domain polarization weighted ESPRIT method using a single vector device is proposed. The frequency domain polari- zation parameters extracted from the signals are used to design the weighted function which is applied to the received signals. The bearing angle and the target frequency are estimated through ESPRIT using the weighted signals. The simulation and experiment results show that the presented method can obtain accurate estimation values under the low SNR with little prior information.

Application of Different Image Processing Techniques on Aster and ETM+ Images for Exploration of Hydrothermal Alteration Associated with Copper Mineralizations Mapping Kehdolan Area (Eastern Azarbaijan Province-Iran)

The Kehdolan area is located at 20 kilometers to the?south-east of Dozdozan Town (Eastern Azarbaijan Province). According to structural geology, volconic rocks are situated in Alborz-Azarbyjan zone, and faults?are?observed?in?the?same direction to this system with SE-NW trend. The results show that kaolinite alteration trend with Argilic and propylitic veins?is the?same direction with SW-NE faults in this area. Therefore, these faults with these trends can be considered as the mineralization control for determination of the alterations. Different image processing techniques,?such as false color composite?(FCC), band ratios, color ratio composite?(CRC), principal component?analysis?(PCA), Crosta technique, supervised spectral angle mapping?(SAM), are used for?identification of the alteration zones associated with copper mineralization. In this project ASTER?data are process and spectral analysis to fit for recognizing intensity and kind of argillic, propylitic,?philic, and ETM+ data?which?are process and to fit for iron oxide and relation to metal mineralization of the area. For recognizing different alterations of the study area, some chemical and mineralogical analysis data from the samples showed that ASTER data and ETM+ data were?capable of hydrothermal alteration mapping with copper mineralization.?Copper mineralization in the region is in agreement with argillic alteration. SW-NE trending faults controlled the mineralization process.

Direct Torque and Adaptive Flux Sensorless Control of Novel Transverse Flux Permanent Magnet Motors

横向磁通永磁电机在开环无刷直流驱动模式下不可避免存在转矩脉动,但可以通过采用直接转矩控制加以改善。首先分析无刷直流驱动中＂花瓣＂状定子磁链轨迹的形成机理,然后针对传统转矩和磁链双闭环直接转矩控制中的定子磁链给定难的问题,提出了无位置传感器磁链自适应直接转矩控制方案。该方案仅利用定子磁链位置和转矩滞环比较器决定电压矢量,并配合换相补偿以修正定、转子磁链夹角与最佳提前换相角之间的偏差以兼顾高转矩电流比和低转矩脉动。仿真和实验结果证实了该方案的有效性和可行性。

Mathematical Model of Drag Torque with Surface Tension in Single-Plate Wet Clutch

Reduction of drag torque in disengaged wet clutches is essential for transmission research because it is one of the potentials of e ciency improvement. Aeration of oil film between two closely rotating plates promotes the decrease of drag torque at high speed region. The e ects of surface tension and static contact angles during aeration are nonnegligible showed by test results. The traditional lubrication model does not adequately predict the experimental results with di erent surface tension and contact angles during aeration. Hence, in this present paper, contact angles between Aluminum and Teflon materials were firstly measured, and the drag torques under two di erent contact angles were examined experimentally. An improved lubrication model of drag torque based on Navier–Stokes equations at the gas-liquid interface was built. The lubrication boundary condition was modified to introduce the e ects of surface tension and contact angle. The model shows that the e ects at the beginning of aeration of oil film are significant. These e ects almost occur at stationary plate due to low Reynolds number and Weber number. The model shows that an increase in the surface tension promotes aeration, but does not a ect the peak drag torque. Increasing contact angle also promotes the aeration, and accelerates the decrease of drag torque. The larger contact angle is, the smaller the peak drag torque will be. A computational fluid dynamics(CFD) model based on volume of fluid(VOF) method was presented to validate the interface shape when aeration occurs. The model prediction has a good agreement with experimental observations for Aluminum plates and Teflon plates. The modified lubrication model of drag torque gives a convenient description of the e ects of surface tension and contact angel, and lays down a frame to understand the beginning of aeration.

Control of Hall angle of Skyrmion driven by electric current

Skyrmions are very promising for applications in spintronics and magnetic memory.It is desired to manipulate and operate a single skyrmion.Here we report on the thermal effect on the motion of current-driven magnetic Skyrmions in magnetic metal.The results show that the magnon current induced by the thermal gradient acts on Skyrmions via magnonic spin-transfer torque,an effect of the transverse and longitudinal Skyrmions drift velocities,thus leading to the effective manipulation of the Hall angle through the ratio of thermal gradient to electric current density,which can be used as a Skyrmion valve.

Performance Assessment of a Calm Flapping Wind Turbine with Small Attack Angle

The objective of this research is mainly focused on environment-friendly and moderately slow flapping wind turbine which can easily operate in or near urban areas or rooftops owing to scale merit with low-frequency turbine noise, installation cost, avian mortality rate and safety consideration etc. The authors are focusing on lift based (LB) slow flapping wind turbine operated within a small attack angle amplitude whereas the previous research treated a lift and drag based (LDB) flapping turbine. Here, a unique trajectory for the wing motion was yet designed by using the Chebyshev dyad linkage mechanism as well as the previous report. The wind energy transferred to the mechanical rotation, adopting a single symmetric wing NACA0012. To obtain a smooth flapping motion for the blade, we optimize all fundamental parameters with our simulation model for optimum performance of the turbine. Both static and dynamic analysis has been conducted to confirm the feasibility of the present design. In addition, wind turbine performance was studied for a suitable range of free stream wind velocities. This report confirms that the developed flapping wind turbine can drive at slow speed with suitable energy extraction rate at different wind velocities. Moreover, we made a simple comparative study of the outcomes obtained from our previous lift and drag based flapping wind turbine with present one, i.e., lift based flapping turbine.

舌侧活动翼不同翼拉伸长度内收下前牙的生物力学特征

背景:舌侧活动翼矫治技术是一种新型舌侧矫治技术,不同翼的拉伸长度影响前牙转矩控制效果,目前尚无相关的生物力学研究。目的:探讨舌侧活动翼矫治技术内收下前牙时牙列的位移趋势以及不同翼拉伸长度对下颌前牙生物力学效应的影响。方法:利用锥形束CT采集患者下颌骨以及下牙列数据信息,通过Mimics软件进行三维重建,建立舌侧活动翼内收下前牙的三维有限元模型。在ANSYS软件中分别分析工况A(2 mm拉伸长度)、工况B(2.5 mm拉伸长度)、工况C(3 mm拉伸长度)和工况D(3.5 mm拉伸长度)时下颌前牙的初始位移。结果与结论:①下牙列初始位移趋势:中切牙舌向倾斜移动伴有压低,侧切牙、尖牙轻度舌侧移动伴近中舌向扭转,第二前磨牙远中倾斜并伴有明显舌倾,第一磨牙整体表现为近中倾斜并伴有近中牙冠外翻。因此在下颌拔牙内收病例中,对第二前磨牙的舌向移动应给予重视,临床中可以通过相应的技术予以抵消。②前牙各方向位移趋势:从工况A到工况D,矢状方向:中切牙冠根位移差值由-11.891μm变为-5.7574μm,表示中切牙由倾斜移动向整体移动转变;侧切牙冠根位移差值由-11.8281μm变为-6.71145μm,尖牙冠根位移差值由-7.5723μm变为-4.6955μm,表示侧切牙及尖牙的倾斜移动也在向整体移动转变。垂直方向:从工况A到工况D,切牙的压低量逐渐增大,尖牙的压低量逐渐减小。结果表明,翼的拉伸长度会影响前牙的倾斜移动趋势;随着翼的不断拉伸,下前牙的转矩控制效果越好。

基于改进型转矩分配函数的开关磁阻电机转矩与峰值电流优化研究

开关磁阻电机(SRM)使用传统的转矩分配函数控制时由于转矩分配函数的开关角度恒定,使其在换相阶段出现较为明显的转矩脉动和较高的峰值电流现象。针对这一现象,提出实时调节开关角度的指数型转矩分配函数的控制方法来降低转矩脉动与相峰值电流。与传统的转矩分配控制进行比较分析,所提算法能够在不同电机转速下抑制转矩脉动和降低SRM定子绕组换相峰值电流,在中低速情况下,实时优化转矩分配函数开关角与重叠角,提高了SRM的运行效率。以一台2.2 kW的12/8开关磁阻电机作为控制对象,建立控制系统仿真模型,通过仿真和实验验证了所提算法的有效性。

基于高速摄像法的气液段塞流特性参数测量

在气-液两相段塞流中,液膜段的湿壁分数和弹头倾角是研究气弹段持液率和气弹特性的关键.文章基于光学成像技术设计了高速摄像法的视觉传感器测试系统,实现了气液两相段塞流气弹特性参数测量.基于图像分析技术,优化边缘检测算子,精确定位边缘位置,高质量提取了轮廓分布,将机器学习模型作为预测多相流特征参数的一种新方法,对气弹弹头倾角进行数据建模研究,分析了适用于分层平滑流、波浪和环状流的表观粗糙表面(modified apparent rough surface,MARS)模型以及段塞流气弹区和液膜区流动状态机理,在MARS模型基础上进行了参数优化,使其适用于段塞流液膜处的湿壁分数和持液率求解.结果表明:通过数据拟合的多项式模型弹头倾角α的模型预测结果的平均绝对百分比误差(MAPE)为8.87%,94.6%预测结果处于相对误差±20%的范围内.通过修正MARS模型提出的水平管段塞流液膜处湿壁分数预测结果的MAPE为9.42%,96.1%预测结果处于相对误差±20%的范围内.液膜持液率预测模型结果的MAPE约为8.04%,93.4%预测结果处于相对误差±20%的范围内.

周向错角开关磁阻电机及其直接瞬时转矩控制

传统开关磁阻电机由于其双凸极定、转子铁心结构以及开关型供电方式会造成强转矩脉动。针对此问题,提出了一种新型低转矩脉动周向错角开关磁阻电机。结合电机结构介绍了其运行机理,并对绕组的电感特性和转矩出力进行了分析。该电机采用内-外双定子结构,转子上同时设置内凸极和外凸极,且内、外定子铁心之间以及转子内、外凸极之间在周向上均相互错开一定的角度。内定子极上绕有辅助绕组,可以在主绕组换相期间提供辅助转矩以补偿转矩跌落,从而降低转矩脉动。利用场路耦合联合仿真,分别构建了传统开关磁阻电机与周向错角开关磁阻电机的直接瞬时转矩控制系统,对比两者在匀速运行工况下的转矩脉动情况,结果表明相较于传统开关磁阻电机,周向错角开关磁阻电机的转矩脉动更小,具有良好的转矩脉动抑制效果。

高压大排量径向柱塞泵定子运动规律分析

为改善高压大排量径向柱塞泵定子-滑靴副摩擦状况,实现泵的精确变量,提出定子圆周方向非固定安装结构。通过滑靴柱塞组件力学特性分析,建立单个滑靴滑动摩擦力矩和11个滑靴摩擦合力矩,求解得到定子角速度变化曲线。结果表明,定子在滑靴滑动摩擦力矩作用下能够运动,且排油区滑靴摩擦力矩大于吸油区滑靴摩擦力矩。径向柱塞泵正常工作后,定子角速度稳定在89.5~90.6 rad/s,呈周期变化,对定子运动起阻碍作用的滑靴个数为4、5交替变换。为高压大排量径向柱塞泵滑靴副设计、提高泵的性能提供一定参考。

基于伤椎高度、Cobb角评估棘突与椎板外缘定位椎弓根技术治疗胸腰椎骨折的疗效

目的通过伤椎高度、Cobb角评估棘突与椎板外缘定位椎弓根技术研究治疗胸腰椎骨折的疗效。方法选择2017年9月至2020年9月在衡水市第四人民医院收治的胸腰椎骨折患者116例,其中男性61例,女性55例;年龄38~71岁,平均年龄48.59岁;骨折节段,L137例,L223例,L1121例,L1235例。按照数字表法将患者分为观察组58例和对照组58例,两组患者均行椎弓根技术治疗。对照组患者给予上关节突外缘垂直线与横突平分线交点(Magerl法)定位椎弓根钉。观察组患者给予棘突与椎板外缘定位椎弓根钉。对比两组患者的Oswestry功能障碍指数(ODI)、伤椎矢状面Cobb角及伤椎前缘高度压缩率、骨代谢、骨愈合、炎症反应、肿胀及疼痛程度。结果两组患者术前、术后1周、术后1年的ODI比较,差异无统计学意义(P>0.05)。术前、术后1周两组患者的伤椎矢状面Cobb角比较,差异无统计学意义(P>0.05)。术后1年观察组伤椎矢状面Cobb角低于对照组[(9.8±2.9)°vs(13.5±3.0)°。P<0.05]。术前、术后1周两组患者的伤椎前缘高度压缩率比较,差异无统计学意义(P>0.05)。术后1年对照组伤椎前缘高度压缩率高于观察组[(14.2±3.4)%vs(8.6±2.2)%。P<0.05]。观察组患者的血清碱性磷酸酶(ALP)、Ⅰ型前胶原羧基端前肽(PICP)及骨钙素(BGP)指标均高于对照组[(219.23±6.34)μg/L vs(182.54±5.17)μg/L、(112.72±2.18)μg/L vs(93.67±2.69)μg/L、(7.52±0.36)μg/L vs(4.21±0.14)μg/L。P<0.05]。观察组可溶性细胞间黏附分子-1(sLCAM-1)、胰岛素样生长因子-1(IGF-1)指标均高于对照组[(107.58±4.25)μg/L vs(92.12±4.19)μg/L、(296.57±8.04)μg/L vs(237.28±7.82)μg/L。P<0.05]。观察组患者肿瘤坏死因子-α(TNF-α)、白细胞介素-6(IL-6)及白细胞介素-1(IL-1)指标均低于对照组[(1.20±0.27)μg/L vs(1.52±0.51)μg/L、(1.06±0.14)μg/L vs(1.35±0.28)μg/L、(0.98±0.27)μg/L vs(1.19±0.42)μg/L。P<0.05]。第1天、第5天、第10天、第15天、第20天两组患者的肿胀程度及疼痛评分均逐渐降低,除第1天观察组肿胀程度高于对照组外[(3.88±0.54)分vs(3.31±0.43)分。P<0.05],其他不同时间对照组疼痛评分及肿胀程度高于观察组(P<0.05)。结论棘突与椎板外缘定位椎弓根技术治疗胸腰椎骨折可降低患者的伤椎高度、Cobb角,提高骨代谢,降低炎症反应、肿胀及疼痛程度,促进骨愈合,临床疗效显著。