An unknown input observer based approach to fault detection for linear multi-agent systems

openThis thesis deals with the problem of fault detection and isolation (FDI) in multi-agent systems (MAS) with linear dynamics. After a brief introduction of MAS, the relative problems and applications, the problem of FDI is introduced. A model in which two kinds of faults (one on the actuator and one on the sensor) is presented, and an unknown input observers (UIO) technique is used in order to generate the residual signal that is necessary to detect the presence of a fault. Subsequently, the consensus problem is solved simultaneously with the FDI problem. The thesis investigates both the scenario in which the connection topology among the agents is directed and when it is undirected. Finally, some simulations with MATLAB are performed in order to shown the effectiveness of the proposed approach

Adaptive sliding mode observation in a network of dynamical systems

This paper considers the problem of reconstructing state information in all the nodes of a complex network of dynamical systems. The individual nodes comprise a known linear part and unknown but bounded uncertainties in certain channels of the system. A supervisory adaptive sliding mode observer configuration is proposed for estimating the states. A linear matrix inequality (LMI) approach is suggested to synthesise the gains of the sliding mode observer. Although deployed centrally to estimate all the states of the complex network, the design process depends only on the dynamics of an individual node of the network. The methodology is demonstrated by considering a network of Chua oscillators

Analysis, filtering, and control for Takagi-Sugeno fuzzy models in networked systems

Copyright © 2015 Sunjie Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.The fuzzy logic theory has been proven to be effective in dealing with various nonlinear systems and has a great success in industry applications. Among different kinds of models for fuzzy systems, the so-called Takagi-Sugeno (T-S) fuzzy model has been quite popular due to its convenient and simple dynamic structure as well as its capability of approximating any smooth nonlinear function to any specified accuracy within any compact set. In terms of such a model, the performance analysis and the design of controllers and filters play important roles in the research of fuzzy systems. In this paper, we aim to survey some recent advances on the T-S fuzzy control and filtering problems with various network-induced phenomena. The network-induced phenomena under consideration mainly include communication delays, packet dropouts, signal quantization, and randomly occurring uncertainties (ROUs). With such network-induced phenomena, the developments on T-S fuzzy control and filtering issues are reviewed in detail. In addition, some latest results on this topic are highlighted. In the end, conclusions are drawn and some possible future research directions are pointed out.This work was supported in part by the National Natural Science Foundation of China under Grants 61134009, 61329301, 11301118 and 61174136, the Natural Science Foundation of Jiangsu Province of China under Grant BK20130017, the Fundamental Research Funds for the Central Universities of China under Grant CUSF-DH-D-2013061, the Royal Society of the U.K., and the Alexander von Humboldt Foundation of Germany

Hierarchical-Structure-Based Fault Estimation and Fault-Tolerant Control for Multiagent Systems

This paper proposes a hierarchical-structure-based fault estimation and fault-tolerant control design with bidirectional interactions for nonlinear multiagent systems with actuator faults. The hierarchical structure consists of distributed multiagent system hierarchy, undirected topology hierarchy, decentralized fault estimation hierarchy, and distributed fault-tolerant control hierarchy. The states and faults of the system are estimated simultaneously by merging the unknown input observer in a decentralized fashion. The distributed-constant-gain-based and node-based fault-tolerant control schemes are developed to guarantee the asymptotic stability and H-infinity performance of multiagent systems, respectively, based on the estimated information in the fault estimation hierarchy and the relative output information from neighbors. Two simulation cases validate the efficiency of the proposed hierarchical structure control algorithm

On the Control of Microgrids Against Cyber-Attacks: A Review of Methods and Applications

Nowadays, the use of renewable generations, energy storage systems (ESSs) and microgrids (MGs) has been developed due to better controllability of distributed energy resources (DERs) as well as their cost-effective and emission-aware operation. The development of MGs as well as the use of hierarchical control has led to data transmission in the communication platform. As a result, the expansion of communication infrastructure has made MGs as cyber-physical systems (CPSs) vulnerable to cyber-attacks (CAs). Accordingly, prevention, detection and isolation of CAs during proper control of MGs is essential. In this paper, a comprehensive review on the control strategies of microgrids against CAs and its defense mechanisms has been done. The general structure of the paper is as follows: firstly, MGs operational conditions, i.e., the secure or insecure mode of the physical and cyber layers are investigated and the appropriate control to return to a safer mode are presented. Then, the common MGs communication system is described which is generally used for multi-agent systems (MASs). Also, classification of CAs in MGs has been reviewed. Afterwards, a comprehensive survey of available researches in the field of prevention, detection and isolation of CA and MG control against CA are summarized. Finally, future trends in this context are clarified

Robusni adaptivni observer temeljen na algoritmu za kooperaciju mobilnih robota s više kotača

Wheeled mobile robots (WMRs) are of great importance. Therefore, it is necessary to make sure that they are not defected. But, in case of failures, the diagnosis task is very important to predict then solve the problem. The most useful techniques in diagnosis are observers which are based on the observability of the monitored system that is not usually ensured by WMR. Thus, to overcome this drawback, an intelligent cooperative diagnosis algorithm is proposed and tested for a group of mobile robots. The diagnosis algorithm is based on robust adaptive unknown input observer applied on unobservable robot. The local non-observability of each robot is solved by cooperative communication. The idea consists on considering all WMRs as a Large Scale System (LSS) even these robots may have not common task. Then, the LSS is decomposed into subsystems that everyone refers to each robot communicating with its neighbors. Next, a design of cooperative interconnected systems is studied to reassure the new condition of observability. Besides, Fast Adaptive Fault Estimation (FAFE) algorithm is proposed to improve the performances of the fault estimation. Finally, to illustrate the efficiency of the proposed algorithm, a model of three-wheel omnidirectional mobile robot is presented.Mobilni roboti na kotačima od velike su važnosti. Stoga, nužno je osigurati da ne odlutaju. U slučaju kvara važna je dijagnoza kako bi se predvidio i onda riješio problem. Najkorisnije dijagnostičke tehnike su observeri koji se zasnivaju na osmotrivosti nadgledanih sustava koja kod mobilnih robota na kotačima najčešće nije osigurana. Stoga, kako bi se nadišao ovaj problem, koristi se inteligentan algoritam za kooperativnu dijagnozu i testira se na grupi mobilnih robota. Dijagnostički algoritam zasniva se na robusnom adaptivnom observeru s nepoznatim ulazom koji je primijenjen na neosmotrivom robotu. Lokalna neosmotrivost svakog robota riješena je koopreativnom komunikacijom. Ideja je da se svi mobilni roboti promatraju kao sustav velikih razmjera iako roboti nemaju isti zadatak. Sustav velikih razmjera se tada rastavlja na podsutave tako da se svaki odnosi na jednog robota koji komunicira sa svojim susjedima. Zatim se proučava dizajn kooperativnih povezanih sustava kako bi se osigurali uvjeti za osmotrivost. Dodatno, predlaže se korištenje brze adaptivne estimacije pogreške kako bi se poboljšala estimacije pogreške. Konačno, prikazan je model višesmjernog mobilnog robota na tri kotača kako bi se ilustrirala učinkovitost predloženog algoritma