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Gyroscope Fault Diagnosis Using Fuzzy SVM to Unbalanced Samples

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Transactions of nanjing university of aeronautics and astronautics 2015年第1期32卷 16-21页

作者：罗秋凤张锐李勇杨忠清 UAV Research institute Nanjing University of Aeronautics and Astronautics Department of Automation Nanjing University of Aeronautics and Astronautics

A novel fuzzy support vector machine based on unbalanced samples(FSVM-US)is proposed to solve the high false positive rate problem since the gyroscope output is susceptible to unmanned aerial vehicle(UAV)airborne electromagnetic environment and the gyroscope abnormal signal sample is rather ***,the standard deviation of samples projection to normal vector for SVM classifier hyper plane is *** imbalance feature expression reflecting the hyper plane shift for the number imbalance between samples and the dispersion imbalance within samples is *** the same time,the denoising factor is designed as the exponential decay function based on the Euclidean distance between each sample and the class ***,the imbalance feature expression and denoising factor are configured into the membership *** sample has its own weight denoted the importance to the ***,the classification simulation experiments on the gyroscope fault diagnosis system are conducted and FSVM-US is compared with the standard SVM,FSVM,and the four typical class imbalance learning(CIL)*** results show that FSVM-US classifier accuracy is 12% higher than that of the standard ***,FSVM-US is superior to the four CIL methods in total ***,the FSVMUS noise tolerance is also 17% higher than that of the standard SVM.

关键词： fault diagnosis gyroscope fuzzy support vector machine(FSVM) unbalanced samples membership function

Match Point Solution for Robust Flutter Analysis in Constant-Mach Prediction

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Chinese Journal of aeronautics 2008年第2期21卷 105-114页

作者： Yun Haiwei Han Jinglong institute of Vibration Engineering Nanjing University of Aeronautics and Astronautics

This paper presents a method for robust flutter computation which uses flight altitude as the perturbation variable in order to obtain a match point solution. The air density and sound speed of standard atmosphere model are approximated as the polynomial function of altitude, such that the flight altitude becomes the single perturbation variable that describes the aeroelastic system. The uncertainties of generalized stiffness and damping are considered and the uncertain aeroelastic system can be formulated as linear fractional transformation （LFT） representation which is suitable for/.t analysis framework. Finally, the match point solutions of robust flutter margins can be computed with structured singular value （SSV） theory. The robust flutter analysis method provided in this paper is suitable for constant-Mach flight flutter test and provides valuable reference for flight envelope expansion.

关键词： robust flutter μ-analysis uncertainty perturbation flight flutter test

Synchronous measurement of tribocharge and force at the footpads of freely moving animals

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Friction 2018年第1期6卷 75-83页

作者： Yi SONG Zhouyi WANG Jun ZHOU Yang LI Zhendong DAI institute of Bio-inspired Structure and Surface Engineering Nanjing University of Aeronautics and Astronautics College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics College of astronautics Nanjing University of Aeronautics and Astronautics

Hypothesis on electrostatic attraction mechanisms involving the hairy adhesion of climbing animals has been a matter of controversy for several years. The detection of tribocharge and forces at attachment organs of animals is a practical method of clarifying the dispute with respect to electrostatic attraction in the attachment of animals. Nonetheless, the tribo-electrification is rarely examined in the contact-adhesion of animals(especially in their free and autonomous attachment) due to the lack of available devices. Therefore, the present study involves establishing a method and an apparatus that enables synchronous detection of tribocharge and contact forces to study tribo-electrification in the free locomotion of geckos. A type of a combined sensor unit that consists of a three-dimensional force transducer and a capacitor-based charge probe is used to measure contact forces and tribocharge with a magnitude corresponding to several nano-Coulombs at a footpad of geckos when they climb vertically upward on an acrylic oligomer substrate. The experimental results indicate that tribocharge at the footpads of geckos is related to contact forces and contact areas. The measured charge allows the expectation of an exact attraction with magnitude corresponding to dozens of newtons per square meter and provides a probability of examining tribo-electrification in animal attachment from a macro level.

关键词： tribocharge forces synchronous measurement animal free locomotion

Nonlinear Intelligent Flight Control for Quadrotor Unmanned Helicopter

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Transactions of nanjing university of aeronautics and astronautics 2015年第1期32卷 29-34页

作者：甄子洋浦黄忠陈琦王新华 College of Automation Engineering Nanjing University of Aeronautics and Astronautics UAV Research institute Nanjing University of Aeronautics and Astronautics

Quadrotor unmanned helicopter is a new popular research platform for unmanned aerial vehicle(UAV),thanks to its simple construction,vertical take-off and landing(VTOL)*** a nonlinear intelligent flight control system is developed for quadrotor unmanned helicopter,including trajectory control loop composed of co-controller and state estimator,and attitude control loop composed of brain emotional learning(BEL)intelligent *** intelligent controller based on mammalian middle brain is characterized as self-learning capability,model-free and *** results of a small quadrotor unmanned helicopter show that the BEL intelligent controller-based flight control system has faster dynamical responses with higher precision than the traditional controller-based system.

关键词： quadrotor unmanned helicopter flight control brain emotional learning(BEL) intelligent control

Flight Control System of Unmanned Aerial Vehicle

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Transactions of nanjing university of aeronautics and astronautics 2015年第1期32卷 1-8页

作者：浦黄忠甄子洋夏曼 UAV Research institute Nanjing University of Aeronautics and Astronautics College of Automation Engineering Nanjing University of Aeronautics and Astronautics

To date unmanned aerial system(UAS)technologies have attracted more and more attention from countries in the *** aerial vehicles(UAVs)play an important role in reconnaissance,surveillance,and target tracking within military and civil *** one briefly introduces the development of UAVs,and reviews its various subsystems including autopilot,ground station,mission planning and management subsystem,navigation system and so ***,an overview is provided for advanced design methods of UAVs control system,including the linear feedback control,adaptive and nonlinear control,and intelligent control ***,the future of UAVs flight control techniques is forecasted.

关键词： unmanned aerial vehicle(UAV) flight control optimal control adaptive control intelligent control

Observer-based backstepping longitudinal control for carrier-based UAV with actuator faults

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Journal of Systems Engineering and Electronics 2017年第2期28卷 322-337页

作者： Fengying Zheng Ziyang Zhen Huajun Gong College of astronautics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China College of Automation Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

The paper presents the longitudinal control for the carrier-based unmanned aerial vehicle (UAV) system with unmeasured states, actuator faults, control input constraints, and external disturbances. By combining output state observer, adaptive fuzzy control, and constraint backstepping technology, a robust fault tolerant control approach is proposed. An output state observer with fuzzy logic systems is developed to estimate unmeasured states, and command filters rather than differentiations of virtual control law are used to solve the computational complexity problem in traditional backstepping. Additionally, a robust term is introduced to offset the fuzzy adaptive estimation error and external disturbance, and an appropriate fault controller structure with matching conditions obtained from fault compensation is proposed. Based on the Lyapunov theory, the designed control program is illustrated to guarantee that all the closed-loop signals of the given system are bounded, and the output errors converge to a small neighborhood of zero. A carrier-based UAV nonlinear longitudinal model is employed to testify the feasibility and validity of the control scheme. The simulation results show that all the controllers can perform at a satisfactory level of reference tracking despite the existence of unknown aerodynamic parameters and actuator faults. © 2017 Beijing institute of Aerospace Information.

关键词： Actuators Aircraft control Backstepping Control system analysis Control theory Controllers Error compensation Fault tolerance Flight control systems Fuzzy control Fuzzy filters Fuzzy logic State estimation Three term control systems Unmanned aerial vehicles (UAV)

Mechanism of Carbon Nanotubes Aligning along Applied Electric Field

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Chinese Physics Letters 2008年第1期25卷 270-273页

作者：马少杰郭万林 institute of Nano Science Nanjing University of Aeronautics and Astronautics Nanjing 210016

The mechanism of single-walled carbon nanotubes （SWCNTs） aligning in the direction of external electric field is studied by quantum mechanics calculations. The rotational torque on the carbon nanotubes is proportional to the difference between the longitudinal and transverse polarizabilities and varies with the angle of SWCNTs to the external electric field. The longitudinal polarizability increases with second power of length, while the transverse polarizability increases linearly with length. A zigzag SWCNT has larger longitudinal and transverse polarizabilities than an armchair SWCNT with the same diameter and the discrepancy becomes larger for longer tubes.

关键词： STATIC POLARIZABILITY GROWTH

Effect of emitter layer doping concentration on the performance of a silicon thin film heterojunction solar cell

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Chinese Physics B 2013年第1期22卷 457-461页

作者：张磊沈鸿烈岳之浩江丰吴天如潘园园 College of Materials Science and Technology Nanjing University of Aeronautics and Astronautics Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of education nanjing university of aeronautics and astronautics

A novel type of n/i/i/p heterojunction solar cell with a-Si：H（15 nm）/a-Si：H（10 nm）/epitaxial c-Si（47 p.m）/epitaxial c-Si（3 um） structure is fabricated by using the layer transfer technique, and the emitter layer is deposited by hot wire chemical vapour deposition. The effect of the doping concentration of the emitter layer Sd （Sd=PH3/（PH3 ＋SiH4＋H2）） on the performance of the solar cell is studied by means of current density-voltage and external quantum efficiency. The results show that the conversion efficiency of the solar cell first increases to a maximum value and then decreases with Sd increasing from 0.1% to 0.4%. The best performance of the solar cell is obtained at Sd = 0.2% with an open circuit voltage of 534 mV, a short circuit current density of 23.35 mA/cm2, a fill factor of 63.3%, and a conversion efficiency of 7.9%.

关键词： layer transfer silicon thin film heterojunction solar cell hot wire chemical vapor deposition doping concentration

Influence of blade negative twist on aerodynamic performance of cycloidal propeller

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航空动力学报 2020年第3期35卷 620-632页

作者： ZENG Jianan ZHU Qinghua WANG Kun SHEN Suiyuan ZHU Zhenhua College of aeronautics Nanjing University of Aeronautics and AstronauticsNanjing 210016China

In order to improve the analysis accuracy of the influence of shape parameters on the aerodynamic performance of cycloidal propeller,a set of CFD methods suitable for the simulation of the cycloidal propeller flow field based on the dynamic overset mesh and Unsteady Reynolds time average method equation were *** characteristics of the spanwise lift distribution and surface pressure distribution in case of different negative twist were *** influence of the negative twist on the aerodynamic performance of cycloidal propeller was *** results showed that,the change of negative twist caused the change of azimuth for cycloidal propeller *** larger the absolute value of negative twist,the lower the figure of merit of the cycloidal propeller;the smaller the negative twist,the more gentle the instantaneous aerodynamic fluctuation;the influence mechanism of negative twist on the aerodynamic performance of cycloidal propeller was generated from changing the non-uniform distribution of the cycloidal propeller’s effective angle of attack.

关键词： cycloidal propeller figure of merit negative twist dynamic overset mesh dynamic stall