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Real-time Feed-forward Force Compensation for Active Magnetic Bearings System Based on H∞ Controller

Chinese Journal of Mechanical Engineering 2011年第1期24卷 58-66页

作者： GAO Hui xu longxiang College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

There are two kinds of unbalance vibrations—force vibration and displacement vibration due to the existence of unbalance excitation in active magnetic bearings（AMB） system. And two unbalance compensation methods—closed-loop feedback and open loop feed-forward are presented to reduce the force vibration. The transfer function order of the control system directly influencing the system stability will be increased when the closed-loop method is adopted, which makes the real-time compensation not easily achieved. While the open loop method would not increase the primary transfer function order, it provides conditions for real-time compensation. But the real-time compensation signals are not easy to be obtained in the open loop method. To implement real-time force compensation, a new method is proposed to reduce the force vibration caused by the rotor unbalance on the basis of AMB active control. The method realizes real-time and on-line force auto-compensation based on H∞ controller and one novel feed-forward compensation controller, which makes the rotor rotate around its inertia axis. The time-variable feed-forward compensatory signal is provided by a modified adaptive variable step-size least mean square（VSLMS） algorithm. And the relevant least mean square（LMS） algorithm parameters are used to solve the H∞ controller weighting functions. The simulation of the new method to compensate some frequency-variable and sinusoidal signals is completed by MATLAB programming, and real-time compensation is implemented in the actual AMB experimental system. The simulation and experiment results show that the compensation scheme can improve the robust stability and the anti-interference ability of the whole AMB system by using H∞ controller to achieve close-loop control, and then real-time force unbalance compensation is implemented. The proposed research provides a new control strategy containing real-time algorithm and H∞ controller for the force compensation of AMB system. And

关键词： active magnetic bearings H∞ robust controller sensitivity and complementary sensitivity VSLMS algorithm feed-forward compensation

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Dynamic Responses of Rotor Drops onto Double-decker Catcher Bearing

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Chinese Journal of Mechanical Engineering 2013年第1期26卷 104-113页

作者： ZHU Yili JIN Chaowu xu longxiang College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics

In an active magnetic bearing （AMB） system, the catcher bearings （CBs） are indispensable to protect the rotor and stator in case the magnetic bearings fail. Most of the former researches associated with CBs are mainly focused on the dynamic responses of the rotor drops onto traditional single-decker catcher bearings （SDCBs）. But because of the lower limited speed of SDCB, it cannot withstand the ultra high speed rotation after rotor drop. In this paper, based on the analysis of the disadvantages of SDCBs, a new type of double-decker catcher bearings （DDCBs） is proposed to enhance the CB work performance in AMB system. In order to obtain thc accurate rotor movements before AMB failure, the dynamic characteristics of AMB are theoretically derived. Detailed simulation models containing rigid rotor model, contact model between rotor and inner race, DDCB force model as well as heating model after rotor drop are established. Then, using those established models the dynamic responses of rotor drops onto DDCBs and SDCBs are respectively simulated. The rotor orbits, contact forces, spin speeds of various parts and heat energies after AMB failure are mainly analyzed. The simulation results show that DDCBs can effectively improve the CBs limit rotational speed and reduce the following vibrations, impacts and heating. Finally, rotor drop experiments choosing different types of CBs are carried out on the established AMB test bench. Rotor orbits, inner race temperatures as well as the rotating speeds of both inner race and intermediate races after rotor drop are synchronously measured. The experiment results verify the advantages of DDCB and the correctness of theoretical analysis. The studies provide certain theoretical and experimental references for the application of DDCBs in AMB system.

关键词： active magnetic bearing dynamic stiffness rotor drop double-decker catcher bearing single-decker catcher bearing,heating

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Unbalance Vibratory Displacement Compensation for Active Magnetic Bearings

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Chinese Journal of Mechanical Engineering 2013年第1期26卷 95-103页

作者： GAO Hui xu longxiang ZHU Yili College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics

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 （A1LC） 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/3 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 tmknown 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/earning cont

关键词： active magnetic bearings unbalance displacement compensation mathematical model adaptive iterative learning control

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HIGH TEMPERATURE DISPLACEMENT SENSOR

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Chinese Journal of Mechanical Engineering 2005年第3期18卷 449-452页

作者： xu longxiang Zhang Jinyu Schweitzer Gerhard College of Mechanical and Electric Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China College of Mechanical Engineering Harbin Instrtute of Technology Harbin 150001 China Institute of Robotics Swiss Federal Institute of Technology Zurich Switzerland

A high temperature displacement sensor based on the principle of eddy-current is investigated. A new temperature compensation technique by using eddy-current effect is presented to satisfy the special requirement at high temperature up to 550℃. The experiment shows that the temperature compensation technique leads to good temperature stability for the sensors. The variation of the sensitivity as well as the temperature drift of the sensor with temperature compensation technique is only about 7.4% and 90-350 mV at 550 ℃ compared with that at room temperature, and that of the sensor without temperature compensation technique is about 31.2% and 2-3 V at 550 ℃ compared with that at room temperature. A new dynamic calibration method for the eddy-current displacement sensor is presented, which is very easy to be realized especially in high frequency and at high temperatures. The high temperature displacement sensors developed are successfully used at temperature up to 550 ℃ in a magnetic bearing system for more than 100 h.

关键词： Displacement sensor Eddy current sensor Compensation of temperature High temperature

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LaNets:Hybrid Lagrange Neural Networks for Solving Partial Differential Equations

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Computer Modeling in Engineering & Sciences 2023年第1期134卷 657-672页

作者： Ying Li longxiang xu Fangjun Mei Shihui Ying School of Computer Engineering and Science Shanghai UniversityShanghai200444China School of Science Shanghai UniversityShanghai200444China

We propose new hybrid Lagrange neural networks called LaNets to predict the numerical solutions of partial differential *** is,we embed Lagrange interpolation and small sample learning into deep neural network ***,we first perform Lagrange interpolation in front of the deep feedforward neural *** Lagrange basis function has a neat structure and a strong expression ability,which is suitable to be a preprocessing tool for pre-fitting and feature ***,we introduce small sample learning into training,which is beneficial to guide themodel to be corrected *** advantages of the theoretical support of traditional numerical method and the efficient allocation of modern machine learning,LaNets achieve higher predictive accuracy compared to the *** stability and accuracy of the proposed algorithmare demonstrated through a series of classical numerical examples,including one-dimensional Burgers equation,onedimensional carburizing diffusion equations,two-dimensional Helmholtz equation and two-dimensional Burgers *** results validate the robustness,effectiveness and flexibility of the proposed algorithm.

关键词： Hybrid Lagrange neural networks interpolation polynomials deep learning numerical simulation partial differential equations

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Improvement of valley splitting and valley injection efficiency for graphene/ferromagnet heterostructure

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Chinese Physics B 2020年第7期29卷 199-203页

作者： longxiang xu Wengang Lu Chen Hu Qixun Guo Shuai Shang Xiulan xu Guanghua Yu Yu Yan Lihua Wang Jiao Teng Department of Materials Physics and Chemistry University of Science and Technology BeijingBeijing100083China Institute of Physics Chinese Academy of SciencesBeijing 100190China Beijing Key Laboratory for Nanomaterials and Nanodevices Beijing 100190China Center for the Physics of Materials and Department of Physics McGill UniversityMontrealQuebec H3A 2T8Canada Corrosion and Protection Center Key Laboratory for Environmental Fracture(MOE)University of Science and Technology BeijingBeijing 100083China Institute of Microstructure and Property of Advanced Materials Beijing Key Laboratory of Microstructure and Property of Advanced MaterialsBeijing University of TechnologyBeijing 100124China

The valley splitting has been realized in the graphene/Ni heterostructure with the splitting value of 14 meV,and the obtained valley injecting efficiency from the heterostructure into graphene was 6.18%[***.B 92115404(2015)].In this paper,we report a way to improve the valley splitting and the valley injecting efficiency of the graphene/Ni heterostruc*** intercalating an Au monolayer between the graphene and the Ni,the split can be increased up to 50 ***,the valley injecting efficiency is not improved because the splitted valley area of graphene moves away from the Fermi ***,we mend the deviation by covering a monolayer of Cu on the *** a result,the valley injecting efficiency of the Cu/graphene/Au/Ni heterostructure reaches 10%,which is more than 60%improvement compared to the simple graphene/Ni *** we theoretically design a valley-injection device based on the Cu/graphene/Au/Ni heterostructure and demonstrate that the valley injection can be easily switched solely by changing the magnetization direction of Ni,which can be used to generate and control the valley-polarized current.

关键词： valleytronics two-dimensional materials valley-polarized transport

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主动磁悬浮轴承系统拍振现象分析

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机械工程学报 2011年第13期47卷 104-112页

作者：高辉徐龙祥南京航空航天大学机电学院南京210016

振动分析是研究主动磁悬浮轴承(Active magnetic bearings,AMB)系统的一个重要部分,但是目前结合控制器以及动态不平衡响应建立的系统数学模型相对较少。通过对高速主动磁悬浮轴承转子系统受力分析,参考所使用的不完全微分PID控制器的... 详细信息

振动分析是研究主动磁悬浮轴承(Active magnetic bearings,AMB)系统的一个重要部分,但是目前结合控制器以及动态不平衡响应建立的系统数学模型相对较少。通过对高速主动磁悬浮轴承转子系统受力分析,参考所使用的不完全微分PID控制器的频率特性对AMB广义动刚度的影响以及对转子动态不平衡激励响应的影响,建立径向子系统的力学振动方程。通过此振动方程的解,得出AMB系统存在的振动形式。一种是由于系统固有频率存在而产生的自由振动,另一种是由于不平衡响应存在而产生的简谐振动,并解释当两种振动频率相近时系统所产生的拍振现象。通过调节控制电流主动控制作用,可以改变磁悬浮轴承广义动刚度,进而改变系统固有频率,最终起到减弱拍振现象作用。仿真和试验能够验证拍振现象以及改变主动控制作用后的减振效果。此力学模型可为AMB系统不平衡振动补偿算法研究提供仿真平台。

关键词：主动磁悬浮轴承电磁力线性化动态不平衡响应转子动力学广义动刚度拍振

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磁悬浮轴承开关功率放大器等效数学模型

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电工技术学报 2010年第4期25卷 53-58,64页

作者：王军徐龙祥南京航空航天大学机电学院南京210016

磁悬浮轴承功率放大器是开关型系统,需要从理论上准确地分析开关功率放大器实际特性以指导电路的设计。在三电平脉宽调制功率放大器输出负载电流原理的基础上,运用傅里叶级数理论分析建立了磁悬浮轴承开关功率放大器闭环系统的数学模型... 详细信息

磁悬浮轴承功率放大器是开关型系统,需要从理论上准确地分析开关功率放大器实际特性以指导电路的设计。在三电平脉宽调制功率放大器输出负载电流原理的基础上,运用傅里叶级数理论分析建立了磁悬浮轴承开关功率放大器闭环系统的数学模型并推导出输出负载电流的数学解析式。对该数学模型及数学解析式进行仿真研究,并将仿真结果与Orcad电路软件仿真结果及实验结果相比较,三种结果基本吻合,表明研究的数学模型及解析式是可行有效的。设计的磁悬浮轴承三电平功率放大器使高速磁悬浮电动机在60000r/min的转速下稳定运行。

关键词：磁悬浮轴承数学模型开关功率放大器三电平

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软开关技术在磁悬浮轴承功率放大器中的应用

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电工技术学报 2009年第6期24卷 85-90页

作者：王军徐龙祥南京航空航天大学机电学院南京210016

传统的磁悬浮轴承功率放大器在硬开关工作状态时存在开关损耗和纹波干扰严重等问题,为有效克服这些缺点,采用了一种新的用于磁悬浮轴承的谐振直流环节三电平功率放大器电路。基于三电平控制方法,在传统的开关功率放大器的直流环节增加... 详细信息

传统的磁悬浮轴承功率放大器在硬开关工作状态时存在开关损耗和纹波干扰严重等问题,为有效克服这些缺点,采用了一种新的用于磁悬浮轴承的谐振直流环节三电平功率放大器电路。基于三电平控制方法,在传统的开关功率放大器的直流环节增加辅助谐振电路,实现了电路中所有的开关器件均在零电压开关(ZVS)或零电流开关(ZCS)的条件下工作。文中详细分析了软开关三电平功率放大器各个工作模态的工作原理,给出了相应的电路工作方程。对提出的软开关三电平功率放大器进行仿真与样机试验研究,结果表明软开关三电平功率放大器同样具有输出电流纹波小的优点,开关损耗和纹波电流干扰有效减小,验证了电路是可行、有效的。

关键词：磁悬浮轴承软开关功率放大器三电平并联谐振

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Effect of Au contacts on spin-orbit splitting and bandgap of graphene/Ni（111） surface

Effect of Au contacts on spin-orbit splitting and bandgap of...

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2016中国功能新材料学术论坛

作者： longxiang xu ChenHu Wengang Lu Jiao Teng Department of Materials Physics and Chemistry University of Science and Technology Beijing Institute of Physics Chinese Academy of Sciences

＜正＞The effect of theAu deposition and the Au intercalation on the electronic structure of the graphene/Ni（111）surface by density functional theory was *** has shown that Au greatly influence the band gap,the spin orbit splitting and the valley splitting,which largely depend on the distance of the Au-graphene interface and the position of Au atom,either on the top site or the hollow *** grapheneπbands almost preserve the Dirac cone of the free-standing graphene despite little P-doping

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