共查询到20条相似文献,搜索用时 10 毫秒
1.
Uhn Joo Na 《Journal of Mechanical Science and Technology》2006,20(5):643-651
The theory for a novel fault-tolerant 4-active-pole homopolar magnetic bearing is developed. If any one coil of the four coils
in the bearing actuator fail, the remaining three coil currents change via an optimal distribution matrix such that the same
opposing pole, C-core type, control fluxes as those of the un-failed bearing are produced. The hompolar magnetic bearing thus
provides unaltered magnetic forces without any loss of the bearing load capacity even if any one coil suddenly fails. Numerical
examples are provided to illustrate the novel fault-tolerant, 4-active pole homopolar magnetic bearings. 相似文献
2.
Chong-Won Lee Yeo-Kwon Yoon Ho-Seop Jeong 《Journal of Mechanical Science and Technology》1997,11(2):155-163
The tool axis misalignment, which causes machining inaccuracies in an active magnetic bearing (AMB)-spindle system, can be
compensated by tracking control of the rotor-spindle. The pseudo-derivative feedback (PDF) control scheme alone does not correct
the tool axis misalignment since the integral action results in the narrow bandwidth and large phase lag in the controlled
system. To improve the tracking performance, the feedback and feedforward controllers are combined with the existing proportional-derivative
controller, which stabilizes the inherently unstable AMB-spindle system dynamics. The theoretical and experimental results
show that proposed control scheme efficiently compensates the tool axis misalignment compared with the conventional PDF control
scheme. 相似文献
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在介绍径向四自由度磁轴承结构的基础上,建立了磁轴承多变量系统状态方程。基于自抗扰控制器原理,针对径向四自由度磁轴承系统,提出了多变量系统自抗扰解耦控制方案,构建了控制系统结构,并给出相关控制算法。根据实验样机参数,利用MATLAB软件环境,构建了解耦控制仿真系统,针对系统的阶跃响应、转子起浮等进行了仿真试验。研究结果表明:采用自抗扰控制策略设计的控制系统成功实现了多变量的解耦控制,具有精度高、响应速度快、超调量小等特点。 相似文献
5.
Levitation of passive magnetic bearings and systems 总被引:1,自引:0,他引:1
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. 相似文献
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In this paper, sliding mode control (SMC) is designed and applied to an elastic structure to suppress some of its vibration
modes. The system is an elastic beam clamped on one end and the designed controller uses only the deflection measurement of
the free end. The infinite dimensional mathematical model of the beam is reduced to an ordinary differential equation set
to represent the behavior of required modes. Since the states of the finite dimensional model are not physically measurable
quantities, an observer is designed to estimate these states by measuring the tip deflection of the beam. The performance
of the observer is important because the observed states are used in the SMC design. In this study, by using the output information,
an observer is designed and tested to estimate the states of the finite dimensional model of the beam. Then the designed SMC
is applied to the experimental beam system which gives satisfactory suppressed vibrations. 相似文献
9.
Model validation and controller design for vibration suppression of flexible rotor using AMB 总被引:1,自引:0,他引:1
Soo Jeon Hyeong-Joon Ahn Dong-Chul Han 《Journal of Mechanical Science and Technology》2002,16(12):1583-1593
This paper discusses the model validation and vibration suppression of an AMB flexible rotor via additional LQG controller.
The main difficulty in the vibration suppression of the flexible rotor using AMB is to realize a controller that can minimize
resonance without injuring the stabilized rigid modes. In order to solve this problem, simple scheme for system modeling and
controller design are developed. Firstly, the AMB flexible rotor is stabilized with a PID controller, which leads to a new
stable rotor-bearing system. Then, authors propose the model validation procedure using measured open-loop frequency responses
to obtain an accurate model of the AMB flexible rotor system. After that, LQG controller with modal weighting is designed
to suppress resonances of the stable rotor-bearing system. Due to the poor controllability and observability of flexible modes
compared to rigid ones, balancing of two Gramians is prerequisite for the fair LQG controller design. Simulation with step
disturbance and experimental results of unbalance response up to 10,000 rpm verified the effectiveness of the proposed scheme. 相似文献
10.
As the rolling bearings being the key part of rotary machine, its healthy condition is quite important for safety production. Fault diagnosis of rolling bearing has been research focus for the sake of improving the economic efficiency and guaranteeing the operation security. However, the collected signals are mixed with ambient noise during the operation of rotary machine, which brings great challenge to the exact diagnosis results. Using signals collected from multiple sensors can avoid the loss of local information and extract more helpful characteristics. Recurrent Neural Networks (RNN) is a type of artificial neural network which can deal with multiple time sequence data. The capacity of RNN has been proved outstanding for catching time relevance about time sequence data. This paper proposed a novel method for bearing fault diagnosis with RNN in the form of an autoencoder. In this approach, multiple vibration value of the rolling bearings of the next period are predicted from the previous period by means of Gated Recurrent Unit (GRU)-based denoising autoencoder. These GRU-based non-linear predictive denoising autoencoders (GRU-NP-DAEs) are trained with strong generalization ability for each different fault pattern. Then for the given input data, the reconstruction errors between the next period data and the output data generated by different GRU-NP-DAEs are used to detect anomalous conditions and classify fault type. Classic rotating machinery datasets have been employed to testify the effectiveness of the proposed diagnosis method and its preponderance over some state-of-the-art methods. The experiment results indicate that the proposed method achieves satisfactory performance with strong robustness and high classification accuracy. 相似文献
11.
This paper addresses the problem of developing an on-line diagnostic system for mechanical quality control of household appliances. The selection of a suitable measurement technique for feature extraction is discussed; the choice of a laser Doppler vibrometer technique and a laboratory measurement station for washing machines is presented. Vibration velocity and displacement are measured over a grid of points on the machine surface and data are stored in a database suitable for processing, both with good appliances and with defect ones with known defects. Features from the vibration velocity spectrum are used as the input to a likelihood classifier, which is shown to achieve very good classification scores. 相似文献
12.
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. 相似文献
13.
Fault classification based upon vibration measurements is an essential building block of a conditional based health usage monitoring system. Multiple sensors are incorporated to assure the redundancy and to achieve the desired reliability and accuracy. The shortcoming of using multiple sensors is the need to deal with a high dimensional feature set, a computationally expensive task in classification. It is vital to reduce the feature dimension via an effective feature extraction and feature selection algorithm. A simple wavelet based feature selection scheme is proposed herein, uniquely built by local discriminant bases and genetic optimization. This scheme overcomes the disadvantages faced by the existing feature selection methods by producing a generic feature set, reducing the dimensionality of features, and requiring no prior information of the problem domain. The proposed feature selection scheme is based upon the strategy of "divide and conquer" that significantly reduce the computation time without compromising the classification performance. The simulation results show the proposed feature selection scheme provides at least 65% reduction of the total number of features at no cost of the classification accuracy. 相似文献
14.
To drive the speed of spindle faster and faster, especially for micro-via-drilling, the gas bearing–spindle is a must. However, most investigations of the dynamic characteristics of the spindle system are limited to the ball bearing type of spindle. This work examines the dynamic instability of a rotating spindle system with various bearings to elucidate the difference between the ball and gas bearing–spindle systems. A round Euler–Bernoulli beam is used to approximate the spindle. The Hamilton principle is applied to derive the equation of motion for the spindle system, and the multiple scales perturbation method is employed to solve the instability solution of the system. The effects of bearing types and speeds of rotation on the dynamic characteristics and instability of a rotating spindle system are further studied. 相似文献
15.
This paper discusses an entire procedure for a robust controller design and its implementation of an AMB (active magnetic
bearing) spindle, which is part II of the papers presenting details of system modeling and robust control of an AMB spindle.
Since there are various uncertainties in an AMB system and reliability is the most important factor for applications, robust
control naturally gains attentions in this field. However, tight evaluations of various uncertainties based on experimental
data and appropriate performance weightings for an AMB spindle are still ongoing research topics. In addition, there are few
publications on experimental justification of a designed robust controller. In this paper, uncertainties for the AMB spindle
are classified and described based on the measurement and identification results of part I, and an appropriate performance
weighting scheme for the AMB spindle is developed. Then, a robust control is designed through the mixedμ synthesis based on the validated accurate nominal model of part I, and the robust controller is reduced considering its closed
loop performance. The reduced robust controller is implemented and confirmed with measurements of closed-loop responses. The
AMB spindle is operated up to 57,600 rpm and performance of the designed controller is compared with a benchmark PID controller
through experiments. Experiments show that the robust controller offers higher stiffness and more efficient control of rigid
modes than the benchmark PID controller. 相似文献
16.
《Measurement》2016
In this work, we present the design of a Fault-Tolerant Control (FTC) system, applied in the outlet temperature sensors and in the control valve (actuator) of a concentric double pipe counter-current flow heat exchanger. The FTC consists in a sensors Fault Detection and Isolation (FDI) system and an actuator FDI system. The sensors FDI system is based on analytical redundancy, in such a way that a bank of modified Kalman filters is developed in order to estimate the two outlet temperatures of the heat exchanger. To develop the modified Kalman filters a multi-linear models approach is used. So that, if a sensor fault is detected by the FDI system the measured temperature signal is replaced by the temperature estimation provided by the modified Kalman filter. Moreover, to detect an actuator fault a comparison between the control valve behaviors (the control valve voltage is used to estimate the water flow rate) and a predefined flow rate for each linear model is carried out. In order to keep the continuous operation of the heat exchanger even in fault presence a model-following control law is introduced, such that, when an actuator fault occurs, the FDI system detect the fault and immediately the model-following control makes the fault accommodation in order to compensate the actuator fault. The proposed scheme is presented with experimental data on-line. The successful tests are presented and discussed. 相似文献
17.
An H∞ method for the vibration control of an iron cantilever beam with axial velocity using the noncontact force by permanent magnets is proposed in the paper. The transverse vibration equation of the axially moving cantilever beam with a tip mass is derived by D'Alembert's principle and then updated by experiments. An experimental platform and a magnetic control system are introduced. The properties of the force between the magnet and the beam have been determined by theoretic analysis and tests. The H∞ control strategy for the suppression of the beam transverse vibration by initial deformation excitations is put forward. The control method can be used for the beam with constant length or varying length. Numerical simulation and actual experiments are implemented. The results show that the control method is effective and the simulations fit well with the experiments. 相似文献
18.
新型斯特林制冷机减振器 总被引:2,自引:0,他引:2
研究了微型斯特林制冷机的振动主动控制问题,设计了一种全新的减振器,即用直线电机推动一个弹簧振子系统,在控制系统的反馈控制下产生控制力,来抑制制冷机的振动,该方案的使用使制冷机的振动水平减小了一个数量级。 相似文献
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Jerzy T. Sawicki Eric H. Maslen Kenneth R. Bischof 《Journal of Mechanical Science and Technology》2007,21(6):847-850
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. 相似文献