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Chinese Journal of Aeronautics 2013年第4期26卷 1017-1028页

作者： chen Xiaocen chen maoyin Department of Automation Tsinghua University Department of Electronic and Optical Engineering Ordnance Engineering College

Precise control of a magnetically suspended double-gimbal control moment gyroscope （MSDGCMG） is of vital importance and challenge to the attitude positioning of spacecraft owing to its multivariable, nonlinear and strong coupled properties. This paper proposes a novel linearization and decoupling method based on differential geometry theory and combines it with the internal model controller （IMC） to guarantee the system robustness to the external disturbance and parameter uncertainty. Furthermore, by introducing the dynamic compensation for the inner-gimbal rate-servo system and the magnetically suspended rotor （MSR） system only, we can eliminate the influence of the unmodeled dynamics to the decoupling control accuracy as well as save costs and inhibit noises effectively. The simulation results verify the nice decoupling and robustness performance of the system using the proposed method.

关键词： Differential geometry decoupling Dynamic compensation Internal model controller MSDGCMG Spacecraft control

Saliency detection and edge feature matching approach for crater extraction

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Journal of Systems Engineering and Electronics 2015年第6期26卷 1291-1300页

作者： An Liu Donghua Zhou Lixin chen maoyin chen Department of Automation Tsinghua University Beijing Institute of Special Electronic-mechanical Technology

Craters are salient terrain features on planetary surfaces, and provide useful information about the relative dating of geological unit of planets. In addition, they are ideal landmarks for spacecraft navigation. Due to low contrast and uneven illumination, automatic extraction of craters remains a challenging task. This paper presents a saliency detection method for crater edges and a feature matching algorithm based on edges informa- tion. The craters are extracted through saliency edges detection, edge extraction and selection, feature matching of the same crater edges and robust ellipse fitting. In the edges matching algorithm, a crater feature model is proposed by analyzing the relationship between highlight region edges and shadow region ones. Then, crater edges are paired through the effective matching algorithm. Experiments of real planetary images show that the proposed approach is robust to different lights and topographies, and the detection rate is larger than 90%.

关键词： crater automatic extraction visual saliency featurematching edge detection.

Remaining useful life prediction for multi-component systems with hidden dependencies

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Science China(Information Sciences) 2019年第2期62卷 57-72页

作者： Xiaopeng XI maoyin chen Donghua ZHOU Department of Automation Tsinghua University College of Electrical Engineering and Automation Shandong University of Science and Technology

How can we predict the remaining useful life(RUL) of a dynamic system subject to multiple dependent degradations? Is it possible to address the above problem when the degradation information is obtained indirectly? According to a new type of state space-based model, we mainly develop an online RUL prediction method for the above system. In this model, the dependencies among different degradations can be reflected in a diffusion coefficient matrix. Considering that some industrial systems like blast furnaces are usually equipped with multi-sensors, an efficient information fusion strategy also plays an important role in predicting the RUL. Based on multi-dimensional observations, the hidden degradation states are identified through the sequential Kalman filtering. Meanwhile, the unknown parameters in the model are updated iteratively by the expectation maximization(EM) algorithm. At last, the RUL distributions are simulated through the Monte Carlo method, in which three types of failure structures with regard to the degradations are considered. The effectiveness of the proposed method is fully verified by a numerical example as well as a case study about the blast furnace.

关键词： remaining useful life hidden dependencies state space model multi-source information fusion failure structure

Remaining useful life prediction for a nonlinear multi-degradation system with public noise

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Journal of Systems Engineering and Electronics 2018年第2期29卷 429-435页

作者： ZHANG Hanwen chen maoyin ZHOU Donghua Department of Automation Tsinghua University College of Electrical Engineering and Automation Shandong University of Science and Technology

To predict the remaining useful life(RUL) for a class of nonlinear multi-degradation systems, a method is presented. In the real industrial processes, systems are usually composed by several parts or components, and these parts or components are working in the same environment, thus the degradations of these parts or components will be influenced by common factors. To describe such a phenomenon in degradations, a multi-degradation model with public noise is proposed. To identify the degradation states and the unknown parameters, an iterative estimation method is proposed by using the Kalman filter and the expectation maximization(EM) algorithm. Next, with known thresholds,the RUL of each degradation can be predicted by using the first hitting time(FHT). In addition, the RUL of the whole system can be obtained by a Copula function. Finally, a practical case is used to demonstrate the method proposed.

关键词： remaining useful life(RUL) multi-degradation system public noise nonlinear degradation process

Single image haze removal via depth-based contrast stretching transform

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Science China(Information Sciences) 2015年第1期58卷 56-72页

作者： LIU Qian chen maoyin ZHOU DongHua Department of Automation Tsinghua National Laboratory for Information Science and TechnologyTsinghua University

Under the weather of haze, fog, or smoke, outdoor images show poor visibility and low *** contrast results in the difficulty for carrying out basic local feature(e.g., interest points and edges) detection algorithms, which are necessary procedures in some computer vision applications. Hence, increasing contrast of degraded images is very important since it is helpful in finding more distinct features from haze ***, few single image haze removal methods can simultaneously achieve clear visibility, sufficiently high contrast, and simplicity. In this paper, we propose an intuitive and effective method, called the depth-based contrast stretching transform(DCST), to simultaneously obtain clear visibility and enhance contrast of a single haze gray image. The DCST stretches the contrast of haze images based on the coarse depth layers of *** method is simple and almost real time and can be extended to color images. We analyze in detail that the image stretched by the DCST has a higher local contrast than the image recovered via the physical-based *** demonstrate that images stretched by the DCST have excellent visibility and contrast compared with a few existing algorithms. Compelling performance is also presented by comparing the proposed method with other representative methods in the application of local feature detection.

关键词： image dehazing image defogging image enhancement image restoration local features detection

A Feature Weighted Mixed Naive Bayes Model for Monitoring Anomalies in the Fan System of a Thermal Power Plant

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IEEE/CAA Journal of Automatica Sinica 2022年第4期9卷 719-727页

作者： Min Wang Li Sheng Donghua Zhou maoyin chen IEEE the Department of Automation Tsinghua University the College of Control Science and Engineering China University of Petroleum(East China) the College of Electrical Engineering and Automation Shandong University of Science and Technology

With the increasing intelligence and integration,a great number of two-valued variables(generally stored in the form of 0 or 1)often exist in large-scale industrial ***,these variables cannot be effectively handled by traditional monitoring methods such as linear discriminant analysis(LDA),principal component analysis(PCA)and partial least square(PLS)***,a mixed hidden naive Bayesian model(MHNBM)is developed for the first time to utilize both two-valued and continuous variables for abnormality *** the MHNBM is effective,it still has some shortcomings that need to be *** the MHNBM,the variables with greater correlation to other variables have greater weights,which can not guarantee greater weights are assigned to the more discriminating *** addition,the conditional P(x j|x j′,y=k)probability must be computed based on historical *** the training data is scarce,the conditional probability between continuous variables tends to be uniformly distributed,which affects the performance of *** a novel feature weighted mixed naive Bayes model(FWMNBM)is developed to overcome the above *** the FWMNBM,the variables that are more correlated to the class have greater weights,which makes the more discriminating variables contribute more to the *** the same time,FWMNBM does not have to calculate the conditional probability between variables,thus it is less restricted by the number of training data *** with the MHNBM,the FWMNBM has better performance,and its effectiveness is validated through numerical cases of a simulation example and a practical case of the Zhoushan thermal power plant(ZTPP),China.

关键词： Abnormality monitoring continuous variables feature weighted mixed naive Bayes model(FWMNBM) two-valued variables thermal power plant

Stochastic process-based degradation modeling and RUL prediction: from Brownian motion to fractional Brownian motion

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Science China(Information Sciences) 2021年第7期64卷 5-24页

作者： Hanwen ZHANG maoyin chen Jun SHANG Chunjie YANG Youxian SUN School of Automation and Electrical Engineering University of Science and Technology Beijing State Key Laboratory of Industrial Control Technology College of Control Science and EngineeringZhejiang University Department of Automation Tsinghua University School of Automation and Electrical Engineering Linyi University Department of Electrical and Computer Engineering University of Alberta

Brownian motion(BM) has been widely used for degradation modeling and remaining useful life(RUL) prediction, but it is essentially Markovian. This implies that the future state in a BM-based degradation process relies only on its current state, independent of the past states. However, some practical industrial devices such as Li-ion batteries, ball bearings, turbofans, and blast furnace walls show degradations with long-range dependence(LRD), where the future degradation states depend on both the current and past degradation states. This type of degradation naturally brings two interesting problems, that is, how to model the degradations and how to predict their RULs. Recently, in contrast to the work that uses only BM, fractional Brownian motion(FBM) is introduced to model practical degradations. The most important feature of the FBM-based degradation models is the ability to characterize the non-Markovian degradations with LRD. Although FBM is an extension of BM, it is neither a Markovian process nor a semimartingale. Therefore, how to obtain the first passage time of an FBM-based degradation process has become a challenging task. In this paper, a review of the transition of RUL prediction from BM to FBM is provided. The peculiarities of FBM when addressing the LRD inherent in some practical degradations are discussed. We first review the BM-based degradation models of the past few decades and then give details regarding the evolution of FBM-based research. Interestingly, the existing BM-based models scarcely consider the effect of LRD on the prediction of RULs. Two practical cases illustrate that the newly developed FBMbased models are more generalized and suitable for predicting RULs than the BM-based models, especially for degradations with LRD. Along with the direction of FBM-based RUL prediction, we also introduce some important and interesting problems that require further study.

关键词： remaining useful life degradation model Brownian motion fractional Brownian motion long-range dependence

Condition-based switching and replacement policies for a two-unit warm standby redundant system subject to non-instantaneous switchover

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Chinese Science Bulletin 2014年第33期59卷 4616-4624页

作者： Yunpeng Jiang maoyin chen Donghua Zhou Department of Automation Tsinghua National Laboratory for Information Science and Technology Tsinghua University

This study investigates condition-based switching and replacement policies for a two-unit warm standby redundant system subject to non-instantaneous switchover. The system consists of two identical units: one is operating unit, while the other is standby unit. Two units are under continuous monitoring and degradation described by Gamma processes. Both switching and replacement policies are based on the degradation level of the operating unit. The switching and replacement thresholds are decision variables decided by minimizing the long-run expected cost rate. We first setup the mathematical optimization model and then analyze the global optimal solution of replacement threshold, as well as the existence and uniqueness condition for the local optimal solution of switching threshold(STH). Finally, we find that the optimal replacement threshold is ‘‘the bigger the better'', but the optimal STH depends on some optimal conditions which can be easily computed. Numerical examples are provided to verify the policies, and the effects of noninstantaneous switchover and cost ratio on optimal STHs are numerically discussed.

关键词：操作单元冗余系统替换策略热备份切换瞬时基础数学优化模型

Event-triggered Consensus for Second-order Leaderless Multi-agent Systems

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Event-triggered Consensus for Second-order Leaderless Multi-...

Fault Detection Based on Distributed Redundant Sensors

第25届中国控制与决策会议

作者： Xu Zhang maoyin chen Department of Automation Tsinghua University

ISBN: (纸本)9781467355339

Future multi-agent systems will be equipped with embedded microprocessors with limited resources to gather information and update the control law of each agent. It has been shown that the event-triggered strategy is an effective way for designing control protocol of multi-agent systems. In this paper, we consider the consensus problem of a secondorder leaderless multi-agent systems where the control strategy is event-triggered. The controller of each agent updates when a certain function is triggered, which depends on the ratio of a defined measurement error with respect to the norm of a disagreement vector. For multi-agent systems with a connected topology, we give sufficient conditions to solve the event-triggered consensus problem in a centralised way. Finally, a numerical simulation is given to validate the proposed strategy.

关键词： Event-triggered Control Multi-agent System Consensus

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Fault Detection Based on Distributed Redundant Sensors