液体媒质非接触型压电超声马达机理研究

介绍了一种液体媒质非接触型压电超声马达;这种马达的定子与转子是不接触的,且转子处于液体媒质中,定子压电振动所产生的能量通过定、转子间的液体传递给转子,从而驱动转子旋转,是压电超声马达的一个新的研究领域,文章给出了液体媒质非接触型压电超声马达的结构及驱动电路,对其运行机理进行了分析,并对目前存在的问题及进一步的研究方向作了阐述。     

Sensorless position control of induction motors-an emergingtechnology

Concepts for the sensorless position control of induction motor drives rely on anisotropic properties of the machine rotor. Such anisotropies can be incorporated as periodic variations of magnetic saliencies in various ways. The built-in spatial anisotropy is detected by injecting a high-frequency flux wave into the stator. The resulting stator current harmonics contain frequency components that depend on the rotor position. Models of the rotor saliency serve to extract the rotor position signal using phase-locked loop techniques. A different approach makes use of the parasitic effects that originate from the discrete winding structure of a cage rotor. It has the merit of providing high spatial resolution for incremental positioning without sensor. The practical implementation of sensorless position identification and of a high-accuracy position control system are reported     

Winding distribution effects on induction motor rotor fault diagnosis

The sidebands around stator currents harmonics as a potential tool for supporting the diagnosis of rotor faults in induction motors are analyzed in this paper. The presence of broken bars introduces high frequency components in the machine currents spectrum in addition to the characteristic sidebands around the fundamental component. These additional components are due to the interaction between, rotor asymmetry and either the voltage harmonics, or winding distribution, or rotor slots. In particular, the components at frequencies near to fifth and seventh harmonics, produced by the interaction between the rotor faults and the harmonics of the spatial distribution of stator windings, are analyzed in this work. A multiple coupled circuit model of the induction motor is used to evaluate the sensitivity of these components for different stator winding configurations, load level, supply voltage conditions, and different number of broken bars. Simulation results showed that a particular analyzed component near to fifth harmonic depends mainly on fifth harmonic of winding distribution, which remains almost constant for most common distributions. Therefore, it is expected that this component should be found in most motors with broken bars. Finally, experimental laboratory results and two industrial cases that validate the analysis are presented.     

基于SU-8胶转子的非接触压电微马达

研制了一种非接触压电微马达，通过阻抗分析仪对定子进行扫频测试，确定其共振频率，并且详细介绍了SU-8胶转子制作的工艺流程。利用转速仪比较不同形状和尺寸的转子在调频和调压下的转速，从而确立压电微马达的最优转子。转子半径为6mm，叶片宽度为6mm的三叶片转子转速最高为3569r／min。转子的启动电压和最高电压分别为8V和24V。     

直升机卫星通信的前向链路设计

根据直升机的机身结构特性和卫星通信的传输特点,对直升机卫星通信前向链路的传输方案和数据帧结构进行了设计,提出一种用以检测旋翼遮挡的算法;为了提高信道的传输质量并降低误码率,对在有旋翼遮挡情况下的前向链路采用了分集接收的方法;创新性地提出了在不同遮挡情况下采用2种不同的分集接收方法,并通过仿真实验对这2种分集接收方法进行了比较和分析。     

Hybrid torque modeling of spherical actuators with cylindrical-shaped magnet poles

A ball-joint-like three-degree-of-freedom (3-DOF) spherical actuator which features a ball-shaped rotor with multiple permanent magnet (PM) poles and a spherical-shell-like stator with air-core coils is proposed to achieve omni-directional smooth motion in only one joint. Unlike previous study in which dihedral-shaped PMs are employed as the rotor poles, this paper utilizes cylindrical-shaped PMs to facilitate the fabrication and reduce the system cost significantly. Torque output of the spherical actuator is formulated with a hybrid method, i.e., using both analytical and experimental methodologies. Specifically, the analytical torque model of spherical actuator with dihedral-shaped PM poles is derived. Then a research prototype with cylindrical-shaped PM poles is developed, and a torque measurement testbed is built up to conduct experiment on the prototype. As the torque variation trend of actuators using two different types of PM poles with respect to the rotor orientation is similar, parameters in the analytical model are adjusted to fit with the experimental measurements. The resulting torque model can be employed for real-time motion control of the actuator. The cylindrical-shaped PM poles also reduce the inertial moment of the rotor by 60%, which is favorable for achieving better dynamic performance of the spherical actuator.     

基于增量二维主成分分析的非线性转子系统故障诊断方法

针对智能故障诊断实际应用中存在的故障样本难 以大量获取、面对新增故障类别需要 一个完整的再训练周期的实时性等问题,提出一种采用增量二维主成分分析(incremental t wo-dimensional principal component analysis,I2DPCA)对非线性裂纹转子系统进行故 障 诊断的方法。首先构建水平支撑的非线性裂纹转子系统模型及其动力学方程,分别探究不同 裂纹深度和质量偏心参数时系统振动响应的变化特征。其次将时域振动信号归一化为图像样 本,由I2DPCA算法提取具有高判别力的低维故障特征。在上述处理基础上,使用k-最近邻( k-nearest neighbor,KNN)分类算法进行识别率的计算。数值仿真及相关实验的研究结果 表 明,基于I2DPCA算法的故障诊断方法可以在高速区域及小样本情形下有效地区分不同故障状 况的信号,为裂纹转子系统的早期故障诊断提供了新的检测策略。     

共轴双旋翼直升机卫星通信小型化终端设计与验证

直升机卫星通信面临旋翼转动时卫星通信信号受旋翼遮挡带来的不同程度衰减的问题。共轴双旋翼直升机对卫星通信信号的遮挡特性相比传统单旋翼要更复杂,且国内研究相对较少。首先分析了共轴双旋翼对卫星通信信号的遮挡特性以及抗双旋翼遮挡卫星通信的关键技术,在此基础上设计了一种小型化的适应双旋翼遮挡的卫星通信机载终端,并在双旋翼遮挡模拟环境下完成了试验验证。结果表明其传输性能满足指标要求,对后续工程应用具有设计指导意义。     

A novel Variable-Reluctance Resolver proposal and its performance analysis under healthy and eccentric cases

A Variable-Reluctance resolver (VR-Resolver) with a novel structure is proposed in this paper as an absolute position sensor, where two possible structures are analyzed. The signals and excitation windings are located on the stator. Hence the slip rings are eliminated in the rotor. The rotor is considered by slot/teeth configuration so the rotor is shaped in a simple variable reluctance structure with a low sensitivity to the manufacturing tolerance. The excitation winding is wound in toroidal configuration that leads to having a smaller fill factor as well as turns can be considered for the windings. Maximum position error (MPE) is evaluated for the proposed resolvers in both healthy and eccentric cases. Therefore, the resolvers performance and their sensitivity to the eccentricity fault are evaluated. A flexible Magnetic Equivalent Circuit (MEC) with adjustable accuracy is used for modeling thanks to its capability and shorter processing time compared to the Finite-Element Method (FEM), where different cases are analyzed by a unique MEC model. Finally, comparison between the MEC and FEM-based results as well as experimental tests are presented to show effeteness of the proposed resolver as an accurate absolute position sensor for industries applications.     

光驱动马达技术中晶体转子厚度的优化分析

为了提高碳酸钙晶体转子的转动频率,采用了激光微束驱动单轴双折射晶体使其产生旋转的方法,并改进了光致旋转的实验系统。对给定实验参量下的碳酸钙晶体转子的转动频率与其厚度和激光有效功率的变化关系进行了理论分析,通过实验测得了不同厚度碳酸钙晶体转子的转动频率值,并对影响转子转动频率的主要因素进行了详细讨论。结果表明,碳酸钙晶体转子的转动频率与其厚度呈现余弦变化关系,当入射有效激光功率为10mW时,测得其最大转动频率值为8.9Hz,实验结果与理论模拟基本吻合。该结论为微观范围内生物活细胞的颗粒分类、微纳机械转子的性能研究等提供了技术保障。     

Fault identification in rotor/magnetic bearing systems using discrete time wavelet coefficients

A method of online fault identification in rotor/magnetic bearing systems is presented using wavelet analysis. A filter bank approach is taken to identify the discrete time wavelet coefficients of the rotor displacement signals. From artifacts present in the discrete time wavelet series associated with specific faults, it is shown that it is possible to identify both the onset time and the fault type. This method is demonstrated for simulations of a flexible rotor/active magnetic bearing assembly during auxiliary bearing contact and direct synchronous forcing for a range covering flexible critical speeds. Experimental validation was performed on a flexible rotor/active magnetic bearing facility undergoing sudden rotor unbalance, resulting in rotor orbits with and without auxiliary bearing contact. Artifacts associated with both the sudden mass loss and the rotor/bearing contact are identified.     

Closed-loop magnetic bearing and angular velocity control of a reaction sphere actuator

This article presents the first closed-loop magnetic bearing and angular velocity experimental results of a reaction sphere actuator for satellite attitude control. The proposed reaction sphere is a permanent magnet spherical actuator whose rotor is supported by magnetic bearing and can be torqued electronically about any desired axis. The spherical actuator is composed of an 8-pole permanent magnet spherical rotor and of a 20-pole stator with electromagnets. The electromechanical model of the reaction sphere is summarized together with procedures to estimate the rotor magnetic state, the back-EMF voltage, and the rotor angular velocity, which are all fundamental ingredients for controller design. Dynamic controllers are developed to levitate the rotor inside the stator (magnetic bearing) and to control the rotor angular velocity. The magnetic bearing is based on a state-space controller with reduced-order displacement velocity estimator whereas the angular velocity controller is a simple proportional controller with a dedicated angular velocity estimator. The developed control algorithms are experimentally validated using the developed laboratory prototype showing the ability of simultaneously levitating the rotor while rotating it about a given arbitrary axis.     

Accurate rotor position detection and sensorless control of SRM for super-high speed operation

Based on the general nonlinear magnetizing model (GNMM) from our previous research work, an improved method of detecting rotor position for sensorless control of SRMs in super-high speed operation has been developed. With minimum input data, the approximated GNMM is obtained and the rotor speed estimated. Then the rotor position is detected by the motion equation. To remove rotor position error, the proposed scheme updates the reference at critical points using the flux observation. Further, the GNMM is adaptively tuned based on the updated information. The improved rotor position detection method has been implemented by fully exploring the computation power of the modern DSP. Laboratory verification on different types of SRMs with sensorless control up to 20000 rpm is accomplished.     

A prototype magnetically levitated stepping motor using highTc bulk superconductors

A magnetically levitated stepping motor using high T_c superconductors has been newly developed. The levitated stepping motor consists of a cylindrical rotor with superconductors and a stator with eight electromagnets. The rotor measures 10 mm in diameter, 46 mm in length, and 18 g in mass. The superconductors of the rotor are field-cooled in liquid nitrogen. The levitated rotor is driven by an eight-phase excitation. The rotor spins as the excitation phases of the electromagnets shift one by one. The rotation angle by each step is 45°. The experimental result shows that the rotor speed is limited to about 400 rpm by axial displacements. During the rotation, the radial displacement of the rotor is less than 0.4 mm. Magnetic flux density in the superconductors is studied before and after continuous rotations. These show that there is a possibility that the levitated stepping motor will be realized     

Using an Artificial Neural Network as a Rotor Resistance Estimator in the Indirect Vector Control of an Induction Motor

This paper presents a rotor resistance estimator based on an artificial neural network (ANN) used in the indirect vector control (IVC) of an induction motor (IM). Attention is focused on the dynamic performance of ANN rotor estimator, which gives superior performance over the fuzzy logic based rotor estimator reported in technical literature. The simulation was done using a 1.5 HP induction motor. The same ANN rotor estimator was proved with other IM having different rated power. The use of the same ANN was possible because the scaling and descaling (normalization) of the input and output of ANN was property done for each motor. The ANN training was done offline using the Levenberg-Marquardt algorithm. The neuronal network is a three-layer network; the first layer has fourteen neurons (or nodes), the hidden layer has five neurons and the output layer has only one neuron because the unique output signal is the rotor resistance value.     

A comparison of external and internal methods of signal spectral analysis for broken rotor bars detection in induction motors

Like all mechanical devices, motors are subject to failures, which can sometimes lead to the shutting down of an entire industrial process. This paper looks at failure predictions in three-phase line-operated induction machines through spectral analysis or electric and electromagnetic signals. Fault characteristics frequencies generated in the estimated and the measured signal spectrum, as a result of mechanical abnormalities such as broken rotor bars, are analyzed. Spectral analyses of simple stator current, of the current's Park vector modulus, and or total and partial instantaneous electric powers are considered as external diagnosis. Internal methods of diagnosis are usually based on a mathematical model of the motor. This requires knowledge of the motor's electrical parameters, which are affected by a number of physical phenomena such as temperature variations, skin effects, core losses, and saturation. As internal diagnosis, we examine different approaches to the spectral analysis of electromagnetic torque computed by stator and rotor flux estimation. To this end, the open loop method, the Luenberger observer and the Kalman filter are employed. Finally, experimental results enable us to draw up a table of comparison of internal and external methods in the detection of rotor imperfections, using two criteria under different load levels.     

Magnetically levitated micro PM motors by two types of activemagnetic bearings

This paper describes magnetically levitated micro permanent magnet (PM) motors by two types of active magnetic bearings. The micro PM motors consist of a cylindrical rotor (φ2.0 mm×10 mm), a pair of electromagnets, a pair of photodiodes, and an analog PD controller. The motors are characterized by the small rotor levitated without any mechanical contacts and one-axis controlled active magnetic bearing. Horseshoe-shaped and cylindrical electromagnets are applied to the active magnetic bearing. The rotor successfully rotates, levitating in the center of the electromagnets. In this paper, dynamic characteristics of the two types of micro PM motors, such as relationships between rotation speed and driving current, rotation speed and time, and acceleration and driving current, are discussed. As a result, it is found that the magnetically levitated micro PM motors by two types of active magnetic bearings are very different from each other and very promising     

Online Stator and Rotor Resistance Estimation Scheme Using Artificial Neural Networks for Vector Controlled Speed Sensorless Induction Motor Drive

This paper presents a new method of online estimation for the stator and rotor resistances of the induction motor for speed sensorless indirect vector controlled drives, using artificial neural networks. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. For the stator resistance estimation, the error between the measured stator current and the estimated stator current using neural network is back propagated to adjust the weights of the neural network. The rotor speed is synthesized from the induction motor state equations. The performance of the stator and rotor resistance estimators and torque and flux responses of the drive, together with these estimators, are investigated with the help of simulations for variations in the stator and rotor resistances from their nominal values. Both resistances are estimated experimentally, using the proposed neural network in a vector controlled induction motor drive. Data on tracking performances of these estimators are presented. With this speed sensorless approach, the rotor resistance estimation was made insensitive to the stator resistance variations both in simulation and experiment. The accuracy of the estimated speed achieved experimentally, without the speed sensor clearly demonstrates the reliable and high-performance operation of the drive     

A state observer for the permanent-magnet synchronous motor

An identity state observer for the permanent-magnet synchronous motor is derived which reconstructs the electrical and mechanical states of the motor from current and voltage measurements. The observer operates in the rotor frame and estimates direct and quadrature stator currents, rotor velocity, and rotor position. Since the rotor position is estimated, the rotor reference frame is approximated using the latest rotor position estimate. The motor dynamics and the transformation into the estimated rotor frame are nonlinear, and thus the observer and observer error dynamics are nonlinear. Therefore, stability is analyzed using a linearized error model. Simulations including realistic measurement disturbances are used to investigate the global stability and accuracy of the observer     

Evaluations of a hybrid-type superconducting magnetic bearingsystem

This paper describes a hybrid-type superconducting magnetic bearing (SMB) system. The system is composed of a pair of SMBs and a pair of active magnetic bearings (AMBs). The hybrid-type SMB system does not need bias currents applied to the electromagnets for supporting the rotor, because the rotor mass is supported by the SMBs. The displacements of the rotor are suppressed by both the SMBs and the AMBs. The superconductors of the SMBs were field-cooled. Comparison of the impulse response of the rotor in the hybrid-type SMB system and that with only SMB's working highlights the good performance of the former. In order to investigate the usefulness of the hybrid-type SMB system, displacements of the rotating rotor and energy loss of the system are discussed