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1.
Fault detection and diagnosis are important issues in process engineering. Hence, a considerable interest exists in this field now from industrial practitioners as well as academic researchers, as opposed to 30 years ago. The literature on process fault diagnosis, ranging from analytical methods to artificial intelligence and statistical approaches, is largely widespread. In this paper, the modeling of the real process is known, and the state-space representation is used. The properties of the Finite Memory Observer (FMO) are studied from a global point of view for the class of linear time-varying (LTV) systems with stochastic noises. The FMO performances are framed by the study of their properties, and that of their influences on diagnosis results. Fundamentally, the generation of residuals is an essential procedure in diagnosis. So, the determination of the optimal window length of the observer is resolved, and the generation of residuals for diagnosis completed. In the first part, the design of the observer and the residual generation are shown. The second part is devoted to the study of the sensitivity and robustness of the observer and of residuals generated from the observer. 相似文献
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This paper studies output feedback control of hydraulic actuators with modified continuous LuGre model based friction compensation and model uncertainty compensation. An output feedback adaptive robust controller is constructed which combines the adaptive control part and the robust control part seamlessly. The adaptive part is constructed to handle the parametric uncertainties existed in the model. The residuals coming from parameter adaption and the unmodeled dynamics are taken into consideration by the robust part. Since only the position signal is available, the velocity, pressure, and internal friction states are obtained by observation or estimation. The errors coming from observation and estimation are also dealt with the robust part. Furthermore, the convergence of the closed-loop controller–observer scheme is achieved by the Lyapunov method in the presence of parametric uncertainties only. Extensive comparative experiments performed on a hydraulic actuator demonstrate the effectiveness of the proposed controller–observer scheme. 相似文献
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Parameter fault detection and estimation of a class of nonlinear systems using observers 总被引：1，自引：0，他引：1
The focus of this paper is on the detection and estimation of parameter faults in nonlinear systems with nonlinear fault distribution functions. The novelty of this contribution is that it handles the nonlinear fault distribution function; since such a fault distribution function depends not only on the inputs and outputs of the system but also on unmeasured states, it causes additional complexity in fault estimation. The proposed detection and estimation tool is based on the adaptive observer technique. Under the Lipschitz condition, a fault detection observer and adaptive diagnosis observer are proposed. Then, relaxation of the Lipschitz requirement is proposed and the necessary modification to the diagnostic tool is presented. Finally, the example of a one-wheel model with lumped friction is presented to illustrate the applicability of the proposed diagnosis method. 相似文献
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文章基于风险投资的"认证监督假说"和"道德风险假说",利用我国创业板上市公司2010—2014年的数据,实证检验风险投资对上市公司内部控制缺陷的作用是"抑制"还是"放纵",结果发现:(1)风险投资能"抑制"被投资企业内部控制缺陷,且随着风险投资持股比例的增加,其"抑制"作用更加显著;(2)采用分组检验的办法,发现在风险投资持股比例高的样本中,其对内部控制缺陷有显著的"抑制"作用,在风险投资持股比例低的样本中,风险投资对于内部控制具有不显著的"放纵"作用;(3)文章还发现股权集中度越高,会削弱风险投资对于内部控制缺陷的"抑制"作用;(4)不同背景风险投资对内部控制缺陷的作用不同,政府背景和企业背景风险投资对企业内部控制缺陷具有"抑制"作用,其中企业背景风险投资的"抑制"作用显著,而独资背景的风险投资对内部控制缺陷具有不显著的"放纵"作用。 相似文献
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Modeling uncertainties including parameter uncertainty and unmodeled dynamics hinder the development of high-performance tracking controller for hydraulic servo system. The observation for the unknown state is another issue worthy of attention. In this paper, a new seamless observer-controller scheme for hydraulic servo system is proposed with partial feedback. The position signal and the pressure signal are firstly used to build an extended structure estimation system for the unknown state. The advantage of this estimation system is that the state observer provides an extended structure for the parameter adaptation compared to other state observers. Thus the parameter uncertainty can be handled. An adaptive robust controller is synthesized in this paper which includes the adaptive part and the robust part. The adaptive part is used to eliminate the parameter uncertainty. Then the residuals coming from the parameter adaption and the errors coming from the state observation are taken into consideration in the robust part. Moreover, the unmodeled dynamics is also handled by the robust part. Theoretical analysis proves that a prescribed transient performance and the final tracking accuracy can be guaranteed by the proposed observer-controller scheme in the presence of both parameter uncertainty and unmodeled dynamics. Furthermore, the convergence of the closed-loop controller-observer system is achieved with the parametric uncertainty existed only. Extensive comparative experiments performed on a hydraulic actuator demonstrate the effectiveness of the proposed observer-controller scheme. 相似文献
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《Journal of The Franklin Institute》2022,359(10):5056-5077
In this paper, the problem of distributed fault detection and isolation (FDI) is investigated for a class of linear discrete-time stochastic multi-agent systems (MASs) with additive Gaussian white noises. By using the information received from the generalized neighbor agents, a set of residual generators are designed for one agent based on the minimal-order observers. After dividing the MAS into several first-order components, the residuals are designed to be robust to the faults in some designated components and sensitive to the faults in all the other components. Combining with FDI strategies, multiple concurrent faults in the generalized neighbor agents can be detected and isolated simultaneously. In addition, a necessary condition is established for the observer to have the minimum order. By means of the statistical method, a set of hypothesis tests are derived to detect and isolate the faults. Finally, a simulation example is presented to show the feasibility and effectiveness of the proposed methods. 相似文献
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Confirmatory composite analysis (CCA) is a structural equation modeling (SEM) technique that specifies and assesses composite models. In a composite model, the construct emerges as a linear combination of observed variables. CCA was invented by Jörg Henseler and Theo K. Dijkstra in 2014, was subsequently fully elaborated by Schuberth et al. (2018), and was then introduced into business research by Henseler and Schuberth (2020b). Inspired by Hair et al. (2020), a recent article in the International Journal of Information Management (Motamarri et al., 2020) used the same term ‘confirmatory composite analysis’ as a technique for confirming measurement quality in partial least squares structural equation modeling (PLS-SEM) specifically. However, the original CCA (Henseler et al., 2014; Schuberth et al., 2018) and the Hair et al. (2020) technique are very different methods, used for entirely different purposes and objectives. So as to not confuse researchers, we advocate that the later-published Hair et al. (2020) method of confirming measurement quality in PLS-SEM be termed ‘method of confirming measurement quality’ (MCMQ) or ‘partial least squares confirmatory composite analysis’ (PLS-CCA). We write this research note to clarify the differences between CCA and PLS-CCA. 相似文献
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本文以2007-2014年中国上市公司为样本，基于中国融资融券制度的自然实验环境，采用双重差分模型检验股票卖空机制对企业研发投资的影响。结果发现，在融资融券制度实施前后的观测期内，允许卖空股票的上市公司，其研发投资水平的增长显著低于不允许卖空的上市公司，这表明股票卖空机制抑制了中国企业的研发投资；同时我们发现，股票卖空交易对企业研发投资的抑制效应在治理机制不完善的上市公司更加显著；进一步的研究发现，股票卖空机制是通过提高企业被收购的威胁，促使企业采取真实的盈余管理等作用渠道抑制了企业的研发投资；最后，我们也检验了卖空机制对研发投资效率的影响，发现允许卖空的上市公司更可能出现研发投资不足。 相似文献
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Liguo Qin Xiao He Rui Yan Ruiliang Deng Donghua Zhou 《Journal of The Franklin Institute》2019,356(2):791-818
In the paper, a distributed sensor fault detection and isolation scheme is presented for a network of second-order integrators. A new distributed control law is developed to achieve formation of the system. By using the integration information of distributed formation errors, the control law improves the robustness of the formation. A distributed observer is then designed in each vehicle based on the closed-loop dynamic model of the vehicle. Each vehicle updates the states of the distributed observer by employing the measurements of itself and the transmitted state estimations from its neighbors. Based on the distributed observer, a distributed fault detection observer and a distributed fault isolation observer are designed. The presented distributed fault detection observer in each vehicle is able to be sensitive to the faults of all vehicles in the system. By using the distributed fault isolation observers, each vehicle is able to be sensitive to the faults of itself, its neighbors and its neighbors’ neighbors and to be robust to the faults of other vehicles. Although the fault isolation of the proposed scheme is simple, computation loads of the scheme are lower than the current ones since only the model of the individual vehicle is used. Finally, the effectiveness of the control law and the fault diagnosis scheme is demonstrated by simulations and real-time experiments carried out based on a formation of three quadrotors. 相似文献
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In this paper, a robust actuator fault diagnosis scheme is investigated for satellite attitude control systems subject to model uncertainties, space disturbance torques and gyro drifts. A nonlinear unknown input observer is designed to detect the occurrence of any actuator fault. Subsequently, a bank of adaptive unknown input observers activated by the detection results are designed to isolate which actuator is faulty and then estimate of the fault parameter. Fault isolation is achieved based on the well known generalized observer strategy. The simulation on a closed-loop satellite control system with time-varying or constant actuator faults in the form of additive and multiplicative unknown dynamics demonstrates the effectiveness of the proposed robust fault diagnosis strategy. 相似文献
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Focusing suspended particles in a fluid into a single file is often necessary prior to continuous-flow detection, analysis, and separation. Electrokinetic particle focusing has been demonstrated in constricted microchannels by the use of the constriction-induced dielectrophoresis. However, previous studies on this subject have been limited to Newtonian fluids only. We report in this paper an experimental investigation of the viscoelastic effects on electrokinetic particle focusing in non-Newtonian polyethylene oxide solutions through a constricted microchannel. The width of the focused particle stream is found NOT to decrease with the increase in DC electric field, which is different from that in Newtonian fluids. Moreover, particle aggregations are observed at relatively high electric fields to first form inside the constriction. They can then either move forward and exit the constriction in an explosive mode or roll back to the constriction entrance for further accumulations. These unexpected phenomena are distinct from the findings in our earlier paper [Lu et al., Biomicrofluidics 8, 021802 (2014)], where particles are observed to oscillate inside the constriction and not to pass through until a chain of sufficient length is formed. They are speculated to be a consequence of the fluid viscoelasticity effects. 相似文献
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《Journal of The Franklin Institute》2022,359(10):5036-5055
This paper presents a novel framework towards a time-varying observer design for nonlinear electro-hydraulic actuators. The key idea of this paper is to employ a positive-increasing function associated with the observer objective to improve the estimation performance. An extended state observer is designed to estimate the full state variables and the uncertainties without any knowledge about the upper bounds of the uncertainties and their derivatives. First, without loss of generality, the system model is divided into three parts, and the extended state observers are designed for each part, independently. Then, the time-varying gains of each observer are designed to make the observation errors uniformly bounded. Finally, the simulated performance of the presented framework is compared with two valid approaches including high-order sliding mode and high-gain extended state observers. 相似文献
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Qingyu Su Shuqi Li Yanchao Gao Xin Huang Jian Li 《Journal of The Franklin Institute》2021,358(7):4013-4027
This paper mainly focuses on the problems of attack detection and reconstruction of cyber physical systems (CPS) under dynamic load altering attacks (D-LAA). Taking the smart grid as an example, firstly, the power system subjected to the attack is modeled as a power CPS through system characteristics to provide conditions for attack detection. On this basis, we assume that two vulnerable loads are attacked simultaneously to investigate the impact of the attack on the system. Secondly, a robust sliding mode observer is designed to implement attack reconstruction with the residual signal generated by the observer. After that, an attack detection logic is applied to complete the attack detection by comparing the threshold with the residual. Finally, a three generators and six buses power system is given as an example to verify the feasibility of attack detection and reconstruction by using the real-time simulation platform built by StarSim and MT respectively. The simulation results are given in this paper. 相似文献
15.
Yun Feng Yaonan Wang Jun-Wei Wang Han-Xiong Li 《Journal of The Franklin Institute》2021,358(2):1656-1672
Detection and estimation of abnormalities for distributed parameter system (DPS) have wide applications in industry, e.g., battery thermal fault diagnosis, quality monitoring of hot-rolled strip laminar cooling process. In this paper, the abnormal spatio-temporal (S-T) source detection and estimation problem for a linear unstable DPS is first studied. The proposed methodology consists of two steps: first, an abnormality detection filter (ADF) which generates a residual signal for abnormality detection in the time domain is constructed using pointwise measurement; Then, an adaptive Luenberger-type PDE observer including an adaptive estimation algorithm is designed and triggered only when an alarm raises from the ADF. Theoretic analysis based on the spatial domain decomposition approach is presented to show the convergence of the estimation errors. Finally, an illustrative example is presented to show the performance of the proposed method. 相似文献
16.
The present paper is the Supplement 2 to the Flora of Xizang, based upon
a collection in 1980 by Mr. W. L. Chen et al. from Mêdog, the south-eastern part of
Xizang. In the paper 11 new species are desribed and 10 new-record species are repor-
ted. All the type specimens are kept in the Herbarium of the Institure of Botany,
Academia Sinica (PE). 相似文献
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Shixiang Sun Xinjiang Wei Huifeng Zhang Hamid Reza Karimi Jian Han 《Journal of The Franklin Institute》2018,355(12):4897-4915
In this paper, a composite fault tolerant control (CFTC) with disturbance observer scheme is considered for a class of stochastic systems with faults and multiple disturbances. The disturbances are divided into two parts. One represents the stochastic disturbance with partial known information which is formulated by an exogenous system. The other is independent Wiener process. A stochastic disturbance observer is designed to estimate exogenous disturbance. To make the first type of disturbance can be rejected and the fault can be diagnosed, a composite fault diagnosis observer with disturbance observer is constructed. Furthermore, a composite fault-tolerant controller is proposed to compensate disturbances and faults. Finally, simulation examples are given to demonstrate the feasibility and effectiveness of the proposed scheme. 相似文献
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This paper mainly investigates the fault detection problem for nonlinear multi-agent systems with actuator faults. For fault detection, a fixed-time observer is proposed by employing auxiliary variable received from neighbor agents. Then, with the aid of the observer, a residual vector is introduced by the auxiliary variable to detect the faults occurring on any followers, and each observer can estimate the whole state of followers. Moreover, the convergence time is dependent on the parameters of the designed observer and independent of initial condition of system state. Finally, the theoretical result is verified by a simulation example. 相似文献
19.
Jason S.-H. Tsai Chao-Lung Wei Shu-Mei Guo Leang S. Shieh Ce R. Liu 《Journal of The Franklin Institute》2008,345(5):508-535
An evolutionary programming-based adaptive observer is presented in this paper to improve the performance of state estimation of nonlinear time-varying sampled-data systems. Also, this paper presents a novel state-space adaptive tracker together with the proposed observer and estimation schemes for nonlinear time-varying sampled-data systems having actuator failures. For the class of slowly varying nonlinear time-varying systems, the proposed methodology is able to achieve the desired fault detection and performance recovery for the originally well-designed systems, as long as the controller having the high-gain property. For practical implementation, we utilize the advantages of digital redesign methodology to convert a well-designed high-gain analog controller/observer into its corresponding low-gain digital controller/observer. Illustrative examples are given to demonstrate the effectiveness of the proposed method. The developed digitally redesigned adaptive tracker with the proposed observer and estimator is suitable for implementation by using microprocessors. 相似文献
20.
Mfanafikile Don Mhlongo 《Journal of The Franklin Institute》2009,346(8):830-839
This paper looks at the sensitivity of thickness to variation of friction. The models of friction used are: the classic Amontons-Coulomb; a nonlinear pressure-dependent model proposed by Wriggers, vu Van and Stein; and a velocity-dependent model proposed by Molinari, Estrin and Mercier. They are coded in FORTRAN for use with finite element program ABAQUS. The contact problem is then formulated in the total Lagrangian formulation for contact between an elastic-plastic body and rigid tools. The variational (weak) form of the formulation is given and this is discretized by finite element method. To test and compare the models, one common metal forming processes is simulated: deep drawing of a square-cup. The sensitivity graphs showing each of the three friction models together is given at the end. One other conclusion although not major part of this work is that Amonton-Coulomb is not the best model suited for contact conditions in metal forming processes, because Wriggers et al. model and Molinari et al. model provide better results for modelling bends and corners. 相似文献