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Convergence speed of consensus problems over undirected scale-free networks

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Chinese Physics B 2010年第12期19卷 135-143页

作者：孙巍窦丽华 School of automation Beijing Institute of Technology

Scale-free networks and consensus behaviour among multiple agents have both attracted much attention. To investigate the consensus speed over scale-free networks is the major topic of the present work. A novel method is developed to construct scale-free networks due to their remarkable power-law degree distributions, while preserving the diversity of network topologies. The time cost or iterations for networks to reach a certain level of consensus is discussed, considering the influence from power-law parameters. They are both demonstrated to be reversed power-law functions of the algebraic connectivity, which is viewed as a measurement on convergence speed of the consensus behaviour. The attempts of tuning power-law parameters may speed up the consensus procedure, but it could also make the network less robust over time delay at the same time. Large scale of simulations are supportive to the conclusions.

关键词： scale-free networks consensus power-law distribution

Accurate Evaluation of Free-form Surface Profile Error Based on Quasi Particle Swarm Optimization Algorithm and Surface Subdivision

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Chinese Journal of Mechanical Engineering 2013年第2期26卷 406-413页

作者： WEN Xiulan ZHAO Yibing WANG Dongxia ZHU Xiaochun XUE Xiaoqiang automation Department Nanjing Institute of Technology

Although significant progress has been made in precision machining of free-form surfaces recently, inspection of such surfaces remains a difficult problem. In order to solve the problem that no specific standards for the verification of free-form surface profile are available, the profile parameters of free-form surface are proposed by referring to ISO standards regarding form tolerances and considering its complexity and non-rotational symmetry. Non-uniform rational basis spline（NURBS） for describing free-form surface is formulated. Crucial issues in surface inspection and profile error verification are localization between the design coordinate system（DCS） and measurement coordinate system（MCS） for searching the closest points on the design model corresponding to measured points. A quasi particle swarm optimization（QPSO） is proposed to search the transformation parameters to implement localization between DCS and MCS. Surface subdivide method which does the searching in a recursively reduced range of the parameters u and v of the NURBS design model is developed to find the closest points. In order to verify the effectiveness of the proposed methods, the design model is generated by NURBS and the measurement data of simulation example are generated by transforming the design model to arbitrary position and orientation, and the parts are machined based on the design model and are measured on CMM. The profile errors of simulation example and actual parts are calculated by the proposed method. The results verify that the evaluation precision of freeform surface profile error by the proposed method is higher 10%-22% than that by CMM software. The proposed method deals with the hard problem that it has a lower precision in profile error evaluation of free-form surface.

关键词： profile error evaluation free-form surface quasi particle swarm optimization surface subdivision

Deep Auto-encoded Clustering Algorithm for Community Detection in Complex Networks

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Chinese Journal of Electronics 2019年第3期28卷 489-496页

作者： WANG Feifan ZHANG Baihai CHAI Senchun School of automation Beijing Institute of Technology

The prevalence of deep learning has inspired innovations in numerous research fields including community detection, a cornerstone in the advancement of complex networks. We propose a novel community detection algorithm called the Deep auto-encoded clustering algorithm(DAC), in which unsupervised and sparse single autoencoders are trained and piled up one after another to embed key community information in a lowerdimensional representation, such that it can be handled easier by clustering strategies. Extensive comparison tests undertaken on synthetic and real world networks reveal two advantages of the proposed algorithm: on the one hand, DAC shows higher precision than the kmeans community detection method benefiting from the integration of sparsity constraints. On the other hand,DAC runs much faster than the spectral community detection algorithm based on the circumvention of the time-consuming eigenvalue decomposition procedure.

关键词： Deep learning Community detection Autoencoder Complex networks

Fixed-time attitude tracking control for spacecraft based on a fixed-time extended state observer

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Science China(Information Sciences) 2021年第11期64卷 154-170页

作者： Lijun ZHANG Yuanqing XIA Ganghui SHEN Bing CUI School of automation Beijing Institute of Technology

This paper deals with the problem of fixed-time attitude tracking control for spacecraft subject to model uncertainties and external disturbances. Firstly, by using a fixed-time extended state observer(Fx TESO), the synthetic uncertainties generated by external disturbances and model deviations can be estimated and compensated accordingly. We propose a novel Fx TESO aimed to improve previous *** with the existing extended state observer(ESO), the proposed Fx TESO provides faster convergence and higher accuracy. Then, we design a fixed-time adaptive attitude tracking controller based on the strategy combining the Fx TESO and fast non-singular terminal sliding mode control(FNTSMC), such that a desired attitude can be achieved accurately, which does not only allow providing fast and accurate responses,and acceptable chattering suppression, but also avoid singularity. Finally, the numerical simulation results are discussed to verify the efficiency and merits of the proposed control strategy.

关键词： spacecraft fixed time attitude tracking FxTESO FNTSMC

Hierarchical particle filter tracking algorithm based on multi-feature fusion

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Journal of Systems Engineering and Electronics 2016年第1期27卷 51-62页

作者： Minggang Gan Yulong Cheng Yanan Wang Jie Chen School of automation Beijing Institute of Technology

A hierarchical particle filter（HPF） framework based on multi-feature fusion is *** proposed HPF effectively uses different feature information to avoid the tracking failure based on the single feature in a complicated *** this approach,the Harris algorithm is introduced to detect the corner points of the object,and the corner matching algorithm based on singular value decomposition is used to compute the firstorder weights and make particles centralize in the high likelihood *** the local binary pattern（LBP） operator is used to build the observation model of the target based on the color and texture features,by which the second-order weights of particles and the accurate location of the target can be ***,a backstepping controller is proposed to complete the whole tracking *** and experiments are carried out,and the results show that the HPF algorithm with the backstepping controller achieves stable and accurate tracking with good robustness in complex environments.

关键词： particle filter corner matching multi-feature fusion local binary patterns(LBP) backstepping.

Multi-rate sensor fusion-based adaptive discrete finite-time synergetic control for flexible-joint mechanical systems

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Chinese Physics B 2013年第10期22卷 197-205页

作者：薛广月任雪梅夏元清 School of automation Beijing Institute of Technology

This paper proposes an adaptive discrete finite-time synergetic control （ADFTSC） scheme based on a multi-rate sensor fusion estimator for flexible-joint mechanical systems in the presence of unmeasured states and dynamic uncertainties. Multi-rate sensors are employed to observe the system states which cannot be directly obtained by encoders due to the existence of joint flexibilities. By using an extended Kalman filter （EKF）, the finite-time synergetic controller is designed based on a sensor fusion estimator which estimates states and parameters of the mechanical system with multi-rate measurements. The proposed controller can guarantee the finite-time convergence of tracking errors by the theoretical derivation. Simulation and experimental studies are included to validate the effectiveness of the proposed approach.

关键词： adaptive finite-time synergetic control multi-rate sensor fusion mechanical systems

Bandwidth Based Stability Analysis of Active Disturbance Rejection Control for Nonlinear Uncertain Systems

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Journal of Systems Science & Complexity 2018年第6期31卷 1449-1468页

作者： ZHANG Dongyang WU Qinghe YAO Xiaolan School of automation Beijing Institute of Technology

This paper focuses on the stability analysis of the active disturbance rejection control (ADRC)for a class of uncertain *** overcome the difficulty of defining a reasonable Lyapunov function and setting limitations of system parameters,the converse Lyapunov theorem and the disturbance theory are *** paper proves that the estimation error of the extended state observer (ESO)and the tracking error of the closed-loop system using ADRC are uniformly ultimately bounded and monotonously diminishing with the increase of their respective bandwidth,so that the stability of the ADRC system could be *** order to further illustrate the relationship between the stability range and bandwidths,it analyzes quantitatively the performance of ESO and ADRC based on the root locus and the step ***,an example based on a typical control system is carried out,and simulation results verify the theoretical analysis proved in this paper.

关键词： Active disturbance rejection control (ADRC) bandwidth converse Lyapunov theorem disturbance theory nonlinear uncertain systems stability

Novel Stability Criteria for Sampled-Data Systems With Variable Sampling Periods

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IEEE/CAA Journal of Automatica Sinica 2020年第1期7卷 257-262页

作者： Hanyong Shao Jianrong Zhao Dan Zhang institute of automation Qufu Normal University

This paper is concerned with a novel Lyapunovlike functional approach to the stability of sampled-data systems with variable sampling periods. The Lyapunov-like functional has four striking characters compared to usual ones. First, it is time-dependent. Second, it may be discontinuous. Third, not every term of it is required to be positive definite. Fourth, the Lyapunov functional includes not only the state and the sampled state but also the integral of the state. By using a recently reported inequality to estimate the derivative of this Lyapunov functional, a sampled-interval-dependent stability criterion with reduced conservatism is obtained. The stability criterion is further extended to sampled-data systems with polytopic uncertainties. Finally, three examples are given to illustrate the reduced conservatism of the stability criteria.

关键词： Lyapunov functional sampled-data systems sampling-interval-dependent stability

Parameter Tuning Method for Dither Compensation of a Pneumatic Proportional Valve with Friction

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Chinese Journal of Mechanical Engineering 2016年第3期29卷 607-614页

作者： WANG Tao SONG Yang HUANG Leisheng FAN Wei School of automation Beijing Institute of Technology

In the practical application of pneumatic control devices, the nonlinearity of a pneumatic control valve become the main factor affecting the control effect, which comes mainly from the dynamic friction force. The dynamic friction inside the valve may cause hysteresis and a dead zone. In this paper, a dither compensation mechanism is proposed to reduce negative effects on the basis of analyzing the mechanism of friction force. The specific dither signal（using a sinusoidal signal） was superimposed on the control signal of the valve. Based on the relationship between the parameters of the dither signal and the inherent characteristics of the proportional servo valve, a parameter tuning method was proposed, which uses a displacement sensor to measure the maximum static friction inside the valve. According to the experimental results, the proper amplitude ranges are determined for different pressures. In order to get the optimal parameters of the dither signal, some dither compensation experiments have been carried out on different signal amplitude and gas pressure conditions. Optimal parameters are determined under two kinds of pressure conditions. Using tuning parameters the valve spool displacement experiment has been taken. From the experiment results, hysteresis of the proportional servo valve is significantly reduced. And through simulation and experiments, the cut-off frequency of the proportional valve has also been widened. Therefore after adding the dither signal, the static and dynamic characteristics of the proportional valve are both improved to a certain degree. This research proposes a parameter tuning method of dither signal, and the validity of the method is verified experimentally.

关键词： proportional valve hysteresis dither compensation parameter tuning method