Performances of bearingless and sensorless induction motor drive based on mutual inductances and rotor displacements estimation

A self-sensing bearingless motor is considered as an effective solution to reduce cost and shorten a shaft length. In this paper, a novel estimation method of a rotor displacement is proposed. The method is based on the detection of currents induced by mutual inductances, which vary as a function of the rotor displacements. A high-frequency carrier voltage is superimposed on a motor main terminal voltage. The induced carrier-frequency current component is distinguished from the suspension-winding current. The carrier signal is selected high enough to suspension-current components. However, the carrier current is disturbed in transient conditions. The disturbed current results in a vibration of the estimated rotor displacements. A suspension-current estimator is proposed to reduce this vibration and to obtain the difference between the detected current and the estimated current. As a result, the disturbance vibration is significantly reduced. It is shown that a successful magnetic suspension is realized with the proposed method.     

Bispectral and trispectral features for machine condition diagnosis

The application of bispectral and trispectral analysis in condition monitoring is discussed. Higher-order spectral analysis of machine vibrations for the provision of diagnostic features is investigated. Experimental work is based on vibration data collected from a small test rig subjected to bearing faults. The direct use of the entire bispectrum or trispectrum to provide diagnostic features is investigated using a variety of classification algorithms including neural networks, and this is compared with simpler power spectral and statistical feature extraction algorithms. A more detailed investigation of the higher-order spectral structure of the signals is then undertaken. This provides features which can be estimated more easily in practice and could provide diagnostic information about the machines     

Online Diagnosis of Induction Motors Using MCSA

In this paper, an online induction motor diagnosis system using motor current signature analysis (MCSA) with advanced signal-and-data-processing algorithms is proposed. MCSA is a method for motor diagnosis with stator-current signals. The proposed system diagnoses induction motors having four types of faults such as breakage of rotor bars and end rings, short-circuit of stator windings, bearing cracks, and air-gap eccentricity. Although MCSA is one of the most powerful online methods for diagnosing motor faults, it has some shortcomings, which degrade performance and accuracy of a motor-diagnosis system. Therefore, advanced signal-and-data-processing algorithms are proposed. They are composed of an optimal-slip-estimation algorithm, a proper-sample-selection algorithm, and a frequency auto search algorithm for achieving MCSA efficiently. The proposed system is able to ascertain four kinds of motor faults and diagnose the fault status of an induction motor. Experimental results obtained on 3.7-kW and 30-kW three-phase squirrel-cage induction motors and voltage-source inverters with a vector-control technique are discussed     

Vibration control of flexible rotors using a passive magnetic device working on the principle of electromagnetic shunt damping

Excessive rotor vibration can propagate the micro-cracks and hence the premature failure of the rotor system. A passive magnetic device working on the principle of electromagnetic shunt damping (EMSD) is proposed to passively control the rotor vibrations. Although, these EMSD-based damping systems are quite common in the literature, however, there is not even a single article available in the literature, showing the application of such a device passively controlling the rotor vibrations from a distance. Due to the flow of flux between the rotor, stator, and air gap, the modeling procedure for such an EMSD-based system changes completely and is not available in the literature. Due to rotor movement, there is a variation in the magnetic flux provided by the permanent magnets placed in the device. Due to electromagnetic interactions, electric currents are induced in the windings provided in the device. When these currents are allowed to pass through electrical resistance, damping forces are generated. In this way, vibration energy is converted into heat energy. In this research, it is observed that the damping effect is maximum for an optimal value of electrical resistance. The effect of several turns in the windings and permanent magnet thickness is also investigated in terms of the production of damping forces. The efficiency of the device is mathematically proved through simulations. Further, experimental results verify the effectiveness of the proposed device.     

Design and control of a disk-type integrated motor-bearing system

A disk-type integrated motor-bearing system having axial magnetic flux is newly invented and its design, analysis, and control methods are presented. Sinusoidal motoring currents to four symmetrically placed winding groups produce a torque, whereas control currents of the same magnitude but opposite signs added to the opposite winding groups create radial forces. The control currents are intended to break force symmetry, resulting in unbalanced radial forces. The system employs two stators not only to effectively remove the rotational frequency modulation effect in the radial control forces, but also to reduce the torque ripple. It is shown that the prototype integrated motor-bearing system built in the laboratory succeeds in stable radial direction control and operation of the rotor     

Influence of the motor load inertia and torque in the fault diagnosis of rotors in induction machines

During the last decades, non-invasive techniques have been proposed to carry out the fault diagnosis in electric machines. When these techniques are employed in the fault detection of the induction machine's rotors, they exhibit a strong dependence on factors such as the motor load inertia or the opposed torque. In order to develop automatic diagnostic systems or the diagnosis assistance over the rotor state, such as expert systems or knowledge based systems, it is necessary to have available further information to weigh up the influence of these factors. This work presents a study done, based on induction motor's mathematical models, about the incidence of the motor inertia and the opposed torque in some non-invasive fault detection technique employed more frequently. The model takes into account in an independent way each of the rotor bars and then allows to represent different faulty situations. These techniques with non-invasive features do not require sensors directly over the motor and thus allow a diagnosis even on-line when the machine is running. Particularly the study of the following techniques was approached: power spectral analysis, torque spectral analysis, stator current spectral analysis and Park's current vector behaviour. Therefore the diagnostic may be based in the measurement of motor's external variables such as applied voltages and stator currents.     

热超声倒装键合换能系统 多模态振动与有限元分析

研究了热超声倒装键合设备的核心执行机构——换能系统的动力学特性.利用激光多谱勒测振仪测试系统末端各方向的振动速度,发现系统以轴向振动为主,但受到其他非轴向振动的干扰.非轴向振动对芯片造成芯片倾斜、键合强度降低等负面影响.采用有限元方法对换能系统建模,仿真计算发现换能系统振动是各方向振动的耦合结果,且工作模态附近存在多种干扰模态.最后分析了系统多模态产生的根源并提出抑制方法.     

A novel bearingless interior permanent magnet slice motor driven blood pump

A 2-pole bearingless interior permanent magnet (IPM) motor with slice rotor configuration is presented in this paper. A novel IPM rotor is designed considering direct and indirect operational specifications such as force constant, torque constant, axial/radial stiffness and cogging torque. Cogging torque and its resulting vibrations affect motor and levitation operation significantly. Hence, various rotor configurations are simulated using the finite element method to develop a topology that minimizes these phenomena. The final topology is tested for closed-loop levitation and speed control. The motor is also tested for its intended application as a blood pump. A mock circulatory loop is developed to measure the performance of the pump. The simulation results, experimental control system performance and pump performance results are shown and explained in the paper.     

Design and control of active magnetic bearing system with Lorentz force-type axial actuator

As the size of five-axes active magnetic bearing (AMB) system gets smaller, the space limitation for installation of axial magnetic bearing unit and the eddy current induced braking of radial magnetic bearing unit become a stringent design concern. In this paper, a new type of compact, high-performance five-axes AMB with solid cores and rotor is proposed, which consists of four permanent magnets, four U-shaped cores and 16 control coils. It features that the radial and axial magnetic bearing units are integrated for compact design and that the homo-polar type configuration of poles with optimized pitch length is adopted to minimize the eddy current induced braking force. The proposed homo-polar AMB system is levitated by the Lorentz-type axial as well as Maxwell-type radial forces. Based on the magnetic flux distribution analysis, the control algorithm is designed to account for the coupled effect between the radial and axial control fluxes. Experiments are also carried out with a prototype AMB system to validate the new design concept.     

MUSIC算法提取海洋表面径向流方位的信号预处理

阐述从高频地波雷达海洋回波反演海洋表面流中,使用MUSIC算法提取径向流方位必须的信号预处理.海洋回波首先经线性调频中断连续波(FMICW)波形解调,分成不同距离元海洋回波.在各通道独立接收的海洋回波谱分析的基础上,针对每一距离元进行通道幅度的软件校准.接着从每一距离元合成的海洋回波多普勒功率谱中,分离包含海洋表面流信息的一阶谱区,再依据“局部噪声阈值扣除法”确定其中的可用信号.最终由MUSIC算法提取每一可用信号(其频偏对应径向流速)的多个存在方位,从而获得海洋表面径向流场的完整信息.本文阐述预处理使用的各种算法、效果及实测信号的部分处理结果.     

反射式光纤在高速旋转叶片振动测量中的应用

采用基于反射式光纤工作原理的新型光纤束式叶尖定时传感器,研制了涡轮机高速旋转叶片振动监测系统,能够高效地收集叶尖定时信号,配合后续的光电转换、数据采集和数据分析,实现了高速旋转叶片的实时振动检测.在现场高速模拟转子的实时监测实验中,该系统的工作性能良好,得到的结果与同时进行监测的应变片实验结果基本一致,分析的异步振动阶次和频率也基本符合,为发动机的在线监测奠定了基础.     

A General Approach for the Transient Detection of Slip-Dependent Fault Components Based on the Discrete Wavelet Transform

In this paper, a general methodology based on the application of discrete wavelet transform (DWT) to the diagnosis of the cage motor condition using transient stator currents is exposed. The approach is based on the identification of characteristic patterns introduced by fault components in the wavelet signals obtained from the DWT of transient stator currents. These patterns enable a reliable detection of the corresponding fault as well as a clear interpretation of the physical phenomenon taking place in the machine. The proposed approach is applied to the detection of rotor asymmetries in two alternative ways, i.e., by using the startup current and by using the current during plugging stopping. Mixed eccentricities are also detected by means of the transient-based methodology. This paper shows how the evolution of other non-fault-related components such as the principal slot harmonic (PSH) can be extracted with the proposed technique. A compilation of experimental cases regarding the application of the methodology to the previous cases is presented. Guidelines for the easy application of the methodology by any user are also provided under a didactic perspective.      

A theoretical model for analyzing the dynamic behavior of a misaligned rotor with active magnetic bearings

The dynamic response of a misaligned rotor, mounted in two identical active magnetic bearings (AMBs) was numerically investigated in this work. Three simplified models of current biased radial active magnetic bearings were presented, where four, six and eight electromagnets were powered by the bias current i₀ and respective control current. The magnetic forces acting on the rotor, the coil currents and the displacement of the rotor were obtained through an electromagnetic theory. The AMBs’ dynamics support parameters were modelled by linearised direct cross axes stiffness and damping coefficients. These are strongly dependent on the air gap between the stator and the shaft. A spatial model of a misaligned rotor with two degrees of freedom was presented. The motion equations were established for the rotor bearing system and simulated with Newmark method. Simulations results were carried out to survey the dynamic behavior of spatial misaligned rotor mounted in AMBs. The angular misalignment was such that the 2× and 4× running speed components are predominant. Their magnitudes varied with the number of magnets in the bearing and with the air gap between the stator and the shaft.     

基于相位敏感光时域反射计的音频激励信号解调与复现

解调复现外部振动信号在实际工程监测应用中具有广阔的应用前景。基于相位敏感光时域反射计(Φ-OTDR)的DAS可以探测分布式单模光纤的振动信号,其集传感和光纤于一体且还原原始信号时无需参考信号,适用于工程应用。本文设计演示了一种基于 Φ-OTDR的直接监测的简易且低成本的音频振动信号的解调与复现系统。在实验装置中使用聚苯乙烯板作为声音在空气中传输的增敏材料。将正弦干扰声音、人声及音乐三种激励源通过扬声器对待测光纤播放,证明本系统能在10 km的传输距离中复现频率丰富的外部振动信号,且具有4 m的空间分辨率,该系统适用于长距离监测下的外部振动的解调复现。     

Pulse motor with high-temperature superconducting levitation

A simple but stable noncontact high T_c superconducting levitation system with a vertical shaft has been presented. The system consists of a superconductor and permanent magnets. In the system, only a high T_c superconductor supports the lower end of the shaft, and the other end is supported by two ordinary permanent magnets. Since the restoring force is small with respect to the radial direction, the system becomes unstable when the force acts in the radial direction, so it is difficult to drive the shaft by electromagnetic forces when using motors. A driving system using electromagnets has been presented, in which the balanced forces act on two opposite sides of the disc-type rotor in the axial direction. Since the system has no unbalanced force from an analytical point of view, the rotor will be able to rotate without control. In the system, however, since there is eccentricity between the center of rotation and the magnetic center, vibrations are generated. This study also presents an optimal control method for the vibrations. To validate the proposed system and the control method experimental tests have been carried out     

高压真空断路器智能在线监测系统的研制

设计一种基于DSP和LabVIEW的高压真空断路器智能在线监测系统。传感器与下位机构成系统现场监测模块,安装于断路器本体。下位机硬件平台以TMS320F2812型DSP为核心实现断路器行程、分合闸电流和振动等信号的采集和处理,并通过CAN总线将数据传送至上位机（采用LabVIEW软件）,从而实现数据的存储和显示。     

基于稀疏分量分析的振动信号源识别方法

振动传感器接收的信号往往包含不同部件的振动信号和环境噪声,为了从少量振动传感器的接收信号中识别信号源数和各频率分量,提出了一种基于稀疏分量分析的欠定盲源分离方法。该方法首先对混合信号进行时频变换,通过主成分分析提取各个时频点邻域的局部主成分,筛选出单源域特征数据。然后利用余弦距离改进聚类验证技术与模糊聚类算法,对振动源个数进行识别、对聚类参数进行更新,获得信号源数和混合矩阵估计。最后用一系列最小二乘法从混合信号对应的时频点中抽取出源信号。通过仿真实验和实测数据实验验证了本文方法的有效性和稳健性,相比经典时频比方法得到了更稳健、更精确的分离结果,这有助于对机械振动源进行识别和定量评估,以方便后续进行机械状态监测和减振降噪处理。      

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.     

High Frequency Resolution Techniques for Rotor Fault Detection of Induction Machines

Motor current signature analysis (MCSA) is the reference method for the diagnosis of medium–large machines in industrial applications. However, MCSA is still an open research topic, as some signatures may be created by different phenomena, wherein it may become sensitive to load and inertia variations, and with respect to an oscillating load torque, although suitable data normalization can be applied. Recently, the topic of diagnostic techniques for drives and low to medium size machines is becoming attractive, as the procedure can be embedded in the drive at no additional thanks to a dedicated firmware, provided that a suitable computational cost is available. In this paper, statistical time-domain techniques are used to track grid frequency and machine slip. In this way, either a lower computational cost or a higher accuracy than traditional discrete Fourier transform techniques can be obtained. Then, the knowledge of both grid frequency and machine slip is used to tune the parameters of the zoom fast Fourier transform algorithm that either increases the frequency resolution, keeping constant the computational cost, or reduces the computational cost, keeping constant the frequency resolution. The proposed technique is validated for rotor faults.