Fault tolerant control of magnetic bearings with force invariance

A magnetic bearing even with multiple coil failure can produce the same decoupled magnetic forces as those before failure if the lemaining coil currents are properly redistributed This faulttolerant, force invariance control can be achieved with simply leplacing the distribution matrix with the appiopnate one shortly after coils fail, without modifying feedback control law The distribution gain matrix that satisfies the necessary constraint conditions of decoupling linearized magnetic foices is determined with the Lagrange Multiplier optimization method     

基于单电流检测的电动变桨系统容错控制

针对电动变桨系统中常见的电流传感器故障,提出一种基于单电流检测的电动变桨系统变论域模糊容错控制方法。当变桨系统发生单个或两个电流传感器故障时,该方法利用直流母线电流传感器对所缺失的电流信息进行重构,保证三相电流能在任意两个相邻采样周期内得到及时更新,确保闭环系统稳定,并通过自适应阈值故障判断法完成故障相电流传感器的切换及容错。针对调制法引起的重构信号误差及电动变桨系统的主要控制目标,将变论域模糊控制方法应用于速度环,以改善系统抗负载扰动能力,提高容错系统鲁棒性。结果表明,该容错控制方法使得变桨系统在传感器故障情况下,牺牲部分系统性能后依然具有较理想的控制特性,并且该方法的正确性也得到了验证。     

Measurement of small forces with superconducting magnetic bearings

Superconducting bearings promise superior performance in certain scientific and technological applications. One application is in an orbital equivalence principle experiment, where linear bearings of extreme smoothness and small friction are required     

基于ARM7的磁悬浮轴承数字控制系统设计

以ARM7TDMI-S CPU为内核的LPC2131微处理器为核心,设计了同极型四自由度径向主动磁悬浮轴承控制器硬件电路及控制软件,采用变速积分-抗积分饱和增量式数字PID实现了对系统转轴位置及线圈电流的双闭环控制。试验结果表明:磁悬浮轴承具有良好的控制精度及静态刚度,满足了磁悬浮轴承控制性能的初步要求。     

磁悬浮轴承结构与磁路分析

从受控自由度数、磁力产生方式、磁极结构形式、控制电流性质等方面对磁悬浮轴承进行了分类与比较.针对各种典型磁悬浮轴承给出了其结构与磁路示意图,并进行了定性分析与比较,最后分析了磁悬浮轴承结构与磁路方面研究与发展方向.     

驱动桥轴承故障振动诊断

消除干扰信号,提取并综合利用实测信号中各种本质特征是故障诊断的关键环节,通过提取轴承故障的周期性高频冲击信号的包络信号,有效地提高了信噪比;通过利用谱图中振动幅值、轴承故障激振（通过）频率、等间距谱线结构一系列综合特征,可对驱动桥轴承故障进行诊断。     

同极型和异极型磁轴承的磁场分布和功率损耗分析

采用有限元软件ANSYS详细分析了同级型和异极型2种结构磁悬浮轴承的磁场分布,给出了2种结构磁轴承的二维磁力线分布图和磁场分布图,并分析了同级型磁轴承二维磁场矢量分布和三维磁通密度矢量分布。详细计算了在不同频率下2种结构磁轴承的功率损耗,给出了功率损耗随交变电流频率变化拟合曲线。分析结果表明,同极型磁轴承磁力线分布在同一方向,全部平行于转子的轴线,因而耦合效应小,功率损耗小,在应用上具有更加明显的优越性。     

Levitation of passive magnetic bearings and systems

Passive magnetic bearings and their systems are studied with reference to their instability, which reduces their utilisation in technical applications, where the absence of friction and wear, that magnetism allows, would be very important. This study is based on the calculus of the forces acting on magnetic bearings and on their systems, and on the identification of areas of low instability.     

Modeling and performance evaluation of machining spindle with active magnetic bearings

Active magnetic bearings (AMBs) are increasingly employed in the machine tool industry to exploit their advantages over classical bearings such as high speed capability, rotation accuracy, high stiffness, and accurate displacement tracking capability. Furthermore, the possibility of on-line monitoring of the machining process (e.g., cutting force measurement, tool wear) makes AMB spindles very appealing to the High-Speed Machining (HSM) industry. Despite significant progress already reached in HSM technology, there remain numerous open challenges in modeling and control of magnetic bearings as applied to machining spindles. These include optimum control given AMB magnetic saturation levels, management of nonlinear effects, reduction of chatter, and rotor properties. This paper describes a five-degree-of-freedom, high-speed machining spindle supported on AMBs. The rotordynamic modeling and experimentally extracted transfer functions are presented and analyzed. The experimentally measured tool tip compliance is used to compare PID and mu-synthesis control schemes. The primary finding is that the achieved tool tip stiffness is substantially higher with the μ-synthesized controllers than with the best PID we were able to design.     

磁悬浮轴承数字控制器的设计

以数字信号处理器TMS320F2812和复杂可编程器件EPM7128为控制核心,设计了四自由度磁悬浮轴承系统的控制硬件电路。在CCS环境中用C语言编写了系统的程序,采用抗积分饱和的增量式积分分离PID系统控制算法实现系统的控制。针对实验室的四自由度轴承进行了悬浮试验,试验结果表明系统悬浮动态性能良好,达到了控制性能的要求。     

磁流体轴承的磁场与润滑特性分析研究

针对电机轴承高速化载荷高的需求以及磁流体轴承具有的自润滑密封、可靠性高、高速、低摩擦润滑等一系列优点,对磁流体轴承在不同条件下的性能开展了研究。首先从理论上推导了磁流体粘度的相关公式,通过采用Matlab软件在外加磁场的条件下,对磁流体的粘度进行了修正,并给出了磁流体轴承润滑的粘温、粘压特性。其次,采用有限元分析方法设计了外加磁场,并对轴承内部的磁场分布进行了分析。研究结果表明,在外加磁场的作用下,磁流体轴承润滑的粘度发生变化,同时,相较于传统普通轴承,磁流体轴承的承载能力得到提高,能在高温、高速的工况下工作。     

Fault tolerant synchronization of chaotic heavy symmetric gyroscope systems versus external disturbances via Lyapunov rule-based fuzzy control

In this paper, fault tolerant synchronization of chaotic gyroscope systems versus external disturbances via Lyapunov rule-based fuzzy control is investigated. Taking the general nature of faults in the slave system into account, a new synchronization scheme, namely, fault tolerant synchronization, is proposed, by which the synchronization can be achieved no matter whether the faults and disturbances occur or not. By making use of a slave observer and a Lyapunov rule-based fuzzy control, fault tolerant synchronization can be achieved. Two techniques are considered as control methods: classic Lyapunov-based control and Lyapunov rule-based fuzzy control. On the basis of Lyapunov stability theory and fuzzy rules, the nonlinear controller and some generic sufficient conditions for global asymptotic synchronization are obtained. The fuzzy rules are directly constructed subject to a common Lyapunov function such that the error dynamics of two identical chaotic motions of symmetric gyros satisfy stability in the Lyapunov sense. Two proposed methods are compared. The Lyapunov rule-based fuzzy control can compensate for the actuator faults and disturbances occurring in the slave system. Numerical simulation results demonstrate the validity and feasibility of the proposed method for fault tolerant synchronization.     

基于STL-1 DDCAE的轴承故障诊断研究

由于轴承原始振动数据标签信息不足,难以对其进行建模分析,针对这一问题,以美国辛辛那提大学IMS数据集为研究对象,提出了一种基于时序分解与一维深度卷积自编码网络(STL-1DDCAE)的无监督轴承故障诊断方法。首先,通过一维深度卷积自编码网络对轴承正常运行数据的非线性特征进行了挖掘,得到了健康样本的重构误差;然后,采用概率分布的方式拟合了健康样本重构误差信号,并计算了其正太分布参数;最后,利用时间序列分解(STL)方法分析了轴承的重构误差曲线,利用趋势项分量确定了轴承故障的发生时间。研究结果表明：该方法能够充分提取轴承故障特征,自适应地确定样本临界阈值,避免轴承异常状态的高误判率,准确识别3个轴承异常信号发生的时间戳为760、1 780、1 700,并能够根据异常检测时间点分别给轴承数据添加健康状态、内圈故障、外圈故障及滚动体故障的标签,实现数据标签化处理。     

鼓风机轴承故障的共振解调谱分析

简要介绍了风机的类型及应用,通过运用共振解调谱法对鼓风机轴承故障进行的故障诊断和技术分析,说明了共振解调谱法在风机滚动轴承故障诊断中的应用是行之有效的。     

Unbalance vibratory displacement compensation for active magnetic bearings

As the dynamic stiffness of radial magnetic bearings is not big enough,when the rotor spins at high speed,unbalance displacement vibration phenomenon will be produced.The most effective way for reducing the displacement vibration is to enhance the radial magnetic bearing stiffness through increasing the control currents,but the suitable control currents are not easy to be provided,especially,to be provided in real time.To implement real time unbalance displacement vibration compensation,through analyzing active magnetic bearings(AMB) mathematical model,the existence of radial displacement runout is demonstrated.To restrain the runout,a new control scheme-adaptive iterative learning control(AILC) is proposed in view of rotor frequency periodic uncertainties during the startup process.The previous error signal is added into AILC learning law to enhance the convergence speed,and an impacting factor influenced by the rotor rotating frequency is introduced as learning output coefficient to improve the rotor control effects.As a feed-forward compensation controller,AILC can provide one unknown and perfect compensatory signal to make the rotor rotate around its geometric axis through power amplifier and radial magnetic bearings.To improve AMB closed-loop control system robust stability,one kind of incomplete differential PID feedback controller is adopted.The correctness of the AILC algorithm is validated by the simulation of AMB mathematical model adding AILC compensation algorithm through MATLAB soft.And the compensation for fixed rotational frequency is implemented in the actual AMB system.The simulation and experiment results show that the compensation scheme based on AILC algorithm as feed-forward compensation and PID algorithm as close-loop control can realize AMB system displacement minimum compensation at one fixed frequency,and improve the stability of the control system.The proposed research provides a new adaptive iterative learning control algorithm and control strategy for AMB displacement minimum compensation,and provides some references for time-varied displacement minimum compensation.     

电磁轴承技术及其发展趋势

介绍了电磁轴承工作原理,探讨了一些热点问题,并分析了电磁轴承的发展现状及前景.     

滚动轴承故障诊断的神经网络方法

总结分析了轴承的故障形式及原因,给出了振动频率,阐述了Bp网络的结构及算法,并对实例建立BP神经网络。     

Identification of dynamic stiffness and damping in active magnetic bearings using transfer functions of electrical control system

The dynamic rotor behavior is significantly affected by the stiffness and damping characteristics of the bearings. Therefore, it is important to identify these bearing parameters. For active magnetic bearings (AMBs), these bearing parameters not only could be identified from rotor dynamic response, but also from electrical control system transfer function. Some identification works from rotor dynamic response have been reported, but identification from electrical control system transfer function is relatively few. In this paper, we deduced the equivalent stiffness and damping expressions with electrical control system transfer function for rotor AMBs and identified these values from electrical control system model. To evaluate the identified results, previous reported results from rotor dynamic response is employed for comparison. We found that for the stiffness, a complete and precise electrical control model will obtain relatively consistent values; however, for the damping, the accurate electrical control model is still not enough and the eddy current loss should be included.

     

Tuning of fault tolerant control design parameters

This paper presents two major contributions in the field of fault tolerant control. First, it gathers points of concern typical to most fault tolerant control applications and translates the chosen performance metrics into a set of six practical design specifications. Second, it proposes initialization and tuning procedures through which a particular fault tolerant control architecture not only can be set to comply with the required specifications, but also can be tuned online to compensate for a total of twelve properties, such as the noise rejection levels for fault detection and diagnosis signals. The proposed design is realized over a powerful architecture that combines the flexibility of adaptive critic designs with the long term memory and learning capabilities of a supervisor. This paper presents a practical design procedure to facilitate the applications of a fundamentally sound fault tolerant control architecture in real-world problems.