基于场定向控制方式减小永磁直线同步电机推力波动

由于边端效应和齿槽效应,永磁直线同步电机在运行中存在推力波动问题。该文在有限元分析的基础上,利用傅里叶级数进行非线性分析,得到电机的磁阻力和位移的关系表达式,采用场定向控制的方法对电流环电流进行实时补偿,从而达到消除推力波动的目的。实验结果表明在对电流进行补偿后,推力波动和速度波动较小,基本稳定在给定值。

金属镜面上纳米光学天线阵列自发辐射增强与定向辐射

本文提出一种金属镜面上纳米光学天线阵列结构,天线采用金纳米立方体,单个点辐射源位于天线和金镜面之间的纳米间隙内.天线和金镜面之间的纳米间隙支持间隙表面等离激元,能够增强自发辐射速率;同时,周期排布的纳米天线支持表面晶格共振(surface lattice resonance,SLR),通过适当设计阵列周期,可实现沿垂直于基底方向的远场定向辐射.本文结合阵列扫描法(array scanning method,ASM)和全波严格数值方法,计算了辐射源的自发辐射速率.对于远场辐射强度角分布的计算,本文给出了互易定理方法的严格表述和证明过程,该证明过程不同于已有文献中的证明过程,对于无限大周期结构具有更严格的适用性,或者具有更低的计算量.本文提出的天线结构和设计方法可用于指导设计高速、高亮度、定向辐射光源.

提高场定向控制感应电动机传动装置可靠性的策略

虽然场定向控制感应电动机传动装置的设计已经达到了相当成熟的阶段，但是关于提高这种传动装置可靠性的阐述却比较少。本文提出一种新改进的感应电动机传动拓扑法和控制策略，应用这种方法，甚至在逆变器少一臂或电动机少一相的情况下，传动装置仍能连续地无妨障地运行。本文包括这种新控制方法和线路原理的全面分析与计算机仿真。

定向延迟组合激发正演照明方法及应用

基于波动方程照明分析原理和组合震源激发理论,对二维声波波场进行规则网格有限差分正演模拟,并给出组合震源照明度的计算方法,对于多个震源组合激发,通过改变相邻两个震源之间的激发时间,激发所产生的地震波场会沿着某一确定的方向传播,可以增强地下特定的区域的地质体的照明分析。模型试验结果表明,震源数目越多,激发的地震波最大能量指向越集中,改变震源之间的延迟时间,可以调整波场的传播方向,该方法对于分析简单的二维模型以及复杂的逆冲推覆构造模型和marmousi模型的照明能量分布均适用,对于指导炮点的设计有借鉴意义。

基于DSP的无速度传感器矢量控制系统

提出一种基于模糊神经网络的模型参考自适应电机转速辨识方法,将其与SVPWM调制技术控制的变频器系统结合起来,组成了一种基于DSP的感应电机无速度传感器矢量控制系统。具体介绍了其结构及软硬件的设计。实验及仿真结果表明,该系统动态性能好,能准确跟踪电机转速的变化。

一种大转矩外转子永磁轮毂电机驱动特性分析

提出一种大转矩外转子永磁轮毂电机,可用于纯电动机场摆渡车、机场大巴车、公交大巴车等。合理设计电机外转子的永磁磁极倾斜角,使电机相反电动势为只含有3次谐波的梯形波,线反电动势为正弦波,同时不降低电机的输出转矩。分析比较了采用不同矫顽力的磁钢对相反电动势的影响,兼顾转矩输出能力和电机调速范围后,选择了拥有合理矫顽力的永久磁钢。同时,搭建了基于Simplorer-Maxwell软件的场路联合仿真平台,比较、分析了基于正弦波磁场定向控制策略和基于方波控制策略的电机驱动特性。虽然两种方法都能实现转矩控制,但磁场定向控制策略的转矩波动更小。

Directional growth behavior of a(Al) dendrites during concentration-gradientcontrolled solidification process in static magnetic field

The large and small sized Cu（solid）/Al（liquid） couples were prepared to investigate the directional growth behavior of primary a（Al） phase during a concentration-gradient-controlled solidification process under various static magnetic fields（SMFs）.The results show that in the large couples,the α（Al） dendrites reveal a directional growth character whether without or with the SMF.However,the 12 T magnetic field induces regular growth,consistent deflection and the decrease of secondary arm spacing of the dendrites.In the small couples,the α（Al） dendrites still reveal a directional growth character to some extent with a SMF of ≤5 T.However,an 8.8 T SMF destroys the directional growth and induces severe random deflections of the dendrites.When the SMF increases to 12 T,the a（Al） dendrites become quite regular despite of the consistent deflection.The directional growth arises from the continuous long-range concentration gradient field built in the melt.The morphological modification is mainly related to the suppression of natural convections and the induction of thermoelectric magnetic convection by the SMF.

LOW COST IMPLEMENTATION OF SPEED SENSORLESS INDUCTION MOTOR CONTROL USING STATOR FLUX ORIENTATION

The control platform of the induction motor （IM） with low costs is developed by using DSP MC56F8013 with a good performance/price rtaio. The control algorithm for the speed sensorless IM is studied based on the stator flux orientation （SFO）. The algorithm structure is simple to be implemented and cannot be influenced by motor parameters, The improved stator flux estimation is used to compensate errors caused by the low pass filter （LPF）. A new speed regulator is designed to ensure the system working with the maximal torque in the transient state. The system simulation and the prototype experiment are made. Results show that the con- trol system has good dynamic and static performance.

Microscopic phase-field study on directional coarsening mechanism caused by interaction between precipitates in Ni-Al-V alloy

A microscopic phase-field model was used to investigate a directional coarsening mechanism caused by the anisotropic growth of long period stacking and different effects of phases on precipitation in Ni-Al-V alloy.The results show that DO22 mainly coarsens along its short axis,which may press the neighboring L12,leading to the interaction among atoms.Diffusion channels of Al are formed in the direction where the mismatch between γ＇ and γ reduces;the occupation probabilities are anisotropic in space;and direction coarsening of L12 occurs finally.With a rise of ageing temperature,phases appear later and DO22 is much later at a higher temperature,the average occupation probabilities of Al and V reduce,and Al changes more than V.

Effect of travelling magnetic field on interface morphology in directionally solidified Sn-Cd alloy

The diversity of interface morphologies is observed for directionally solidified Sn-0.65%Cd alloy under a travelling magnetic field （TMF） in the 4 mm-diameter sample. Under an upward TMF, planar and cellular interface morphologies transform alternately with increasing magnetic flux density （B≤10.3 mT）. The interface morphology transforms from shallow cellular to deep cellular morphology under a weak downward TMF （B=3.2 mT）. When the magnetic flux density increases further, both sides of the interface morphology appear to be slightly inconsistent, but they roughly tend to be planar under a strong downward TMF （BS10.3 mT）. The interface instability may be attributed to the flow driven by the TMF. Moreover, the shape of interface appears to be almost flat under an upward TMF, but deflective under a downward TMF.

学生学习方式和认知方式差异的研究

本文论述了学生表现在记忆、思维、感觉通道和场定向这四个大的方面不同的认知方式,进而提出并通过实验结果阐述了具有不同认知方式的学生会形成与其认知方式对应的学习方式,提出了教师实施“因材施教”这个总的教学原则的着眼点。

Mechanisms of Avian Magnetic Orientation

Among the most fascinating mysteries of life is the interaction between biological systems and the earth＇s magnetic field. Although earth＇s magnetism may have an under appreciated role in biological interpretations, it has been most extensively studied in the processes of avian orientation and migration. Many species of bird are known to have behavioral responses to the earth＇s and artificial magnetic fields. These responses may be mediated by a number of potential magneto-biochemical processes. The two most commonly investigated include a magnetosensitive magnetite rich region in the upper beak area and a photo/magnetoreception process in the eyes of various bird species. In addition to external magnetic stimuli, recent findings in visually restricted birds have described a hemispherically lateralized interpretation of this information within the brain. Even with these findings, a considerable amount of work is needed to clarify what information is processed and how it is used to create the bird＇s magnetic compass. This review focuses these recently published findings as a means to assess this intriguing phenomenon.

Double ESOs-based field-oriented control for PMSM drive system with current sensorless

A novel double extended state observers(ESOs)-based field-oriented control(FOC)strategy is developed for three-phase permanent magnet synchronous motor(PMSM)drive systems without any phase current sensor.In principle,two current sensors are essential parts of the drive system for implementation of the feedback to achieve high accuracy control.For this purpose,the double ESOs are created to provide feedback stator currents instead of actual current sensors.The first one of the double ESOs is designed to estimate the benchmark value of q-axis stator current,which is a primary premise;While the second is designed to estimate real-time stator currents of d-axis and q-axis simultaneously.The resultant double ESOs can rapidly and accurately give estimation of the actual currents of a-axis,b-axis and c-axis,and the synthesized double ESOs-based FOC strategy for PMSM drive system without any current sensors has satisfactory control performance and strong robustness.Numerical experiments validate the feasibility and effectiveness of the proposed scheme.

Comparative Study of the DTC-IM Speed Controller Based on Artificial Intelligence

Recently, artificial intelligence technique is increasingly receiving attention in solving complex and practical problem and they are widely applying in electrical machine domain. The authors consider also the direct torque control （DTC） as an alternative to conventional methods of control by pulse width modulation （PWM） and by Field oriented control （FOC）, so the application of the DTC based on artificial intelligence can show more advantages and simplified control algorithms with high performance. For this reason, the objectives of this paper can be divided into two parts, the first part is to apply neural networks and fuzzy logic techniques to the DTC control in the presence of a loop speed control comparing to the conventional regulators （as PI） to show the feasibility of these approaches, the second part is to further improve the performance of the neural network by using a neural-fuzzy regulator which combine the advantages of two techniques. Simulation results confirm the validity of the proposed techniques.

Design and Test of Motor Double Fed Speed Regulating System for Conveyer Belt

This paper introduces the design of doubly fed system for conveyor belt motor, the system adopts stator flux orientation vector control technology and AC-AC inverter motor speed and power factor control, and carried on the test in transmission field. This paper introduces in detail the structure and characteristic of DSP system, and gives a design scheme of Doubly Fed Speed Control System of motor based on this chip.

Avian orientation: multi-cue integration and calibration of compass systems

Migratory birds are known to use a number of different orientation cues to determine and maintain the direction of their movements. They are able to use at least three different sources of compass information, including solar, stellar and geomagnetic cues. However, little is known about how these cues are calibrated into uniform reference direction information, while the hierarchy of these cues remains controversial. In recent studies, researchers suggest that avian migrants calibrate their geomagnetic compass on sunset cues, whereas others fail to find such patterns and insist on the prevalence of the magnetic compass. We carefully reviewed the existing literature and suggest that the conflicting results reported by different authors are due to genuine variation among species and propose hypotheses to explain this variation.

Vector Control Scheme of Five-Phase Induction Machines under Open-Circuit Phase Faults

Multiphase induction machine is normally controlled using rotor field oriented vector control. Under phase（s） loss, the machine currents can be optimally controlled to satisfy certain optimization criteria. In this paper, a vector control scheme to a five-phase induction machine is introduced to ensure equal phase currents and minimum torque ripples under a phase open circuit. The controller idea can be extended to any number of phases with any number of open phases. The fundamental dq components of the stator voltage are obtained using only two PI controllers for the fundamental sequence plane, as in conventional vector control of three-phase machines. Based on steady state model, a simple expression is derived to estimate the required dq voltage components of other sequence planes to ensure equal stator phase currents and minimum torque ripple. A five-phase machine is simulated using MATLAB/Simulink to ensure controller validity.

Continuous on-line adaptation of the rotor time constant in FOC induction machine system

Rotor time constant is an important parameter for the indirect lleld oraentateO control of mauc- tion motor. Incorrect rotor tittle constant value will cause the flux observer generating a wrong angu- lar orientation of the rotor field. A new approach serves for rotor time constant on-line adaptation by setting the stator current to be zero for a short period. A smooth eorrector is designed to prevent ab- normal detection result from making adaptation. Impact of zero current duration on detection error and rotor speed is analyzed by experiments.

大庆油田M1井3D VSP成像方法与应用

3D VSP地震数据具有高分辨率和高信噪比的特点,常规的VSP成像方法在大庆油田资料的处理中一直未见到理想的效果.依据大庆油田VSP资料的特点,设计了3D VSP资料的处理流程,主要包括三分量波场逐点定向方法和Q补偿的子波反褶积等预处理方法,所设计的流程具有高分辨率、高保真性的特点.大庆油田M1井的实际资料处理结果显示,所形成的方法可将VSP资料的频带展宽约20 Hz,同时对地面地震也进行了反褶积处理,反褶积后,地面地震的分辨率得到有效提高,波组特征更加清楚.实际数据计算表明,所形成的方法具有很好的实用性,可实现地下介质的精细刻画,可在具有同类地质条件的研究区推广应用.