Fault detection and isolation of malicious nodes in MIMO Multi-hop Control Networks

A MIMO Multi-hop Control Network (MCN) consists of a MIMO LTI system where the communication between sensors, actuators and computational units is supported by a (wireless) multi-hop communication network, and data flow is performed using scheduling and routing of sensing and actuation data. We provide necessary and sufficient conditions on the plant dynamics and on the communication protocol configuration such that the Fault Detection and Isolation (FDI) problem of failures and malicious attacks to communication nodes can be solved.Comment: 6 page

Feedback stabilization of dynamical systems with switched delays

We analyze a classification of two main families of controllers that are of interest when the feedback loop is subject to switching propagation delays due to routing via a wireless multi-hop communication network. We show that we can cast this problem as a subclass of classical switching systems, which is a non-trivial generalization of classical LTI systems with timevarying delays. We consider both cases where delay-dependent and delay independent controllers are used, and show that both can be modeled as switching systems with unconstrained switchings. We provide NP-hardness results for the stability verification problem, and propose a general methodology for approximate stability analysis with arbitrary precision. We finally give evidence that non-trivial design problems arise for which new algorithmic methods are needed

Optimal co-design of control, scheduling and routing in multi-hop control networks

A Multi-hop Control Network consists of a plant where the communication between sensors, actuators and computational units is supported by a (wireless) multi-hop communication network, and data flow is performed using scheduling and routing of sensing and actuation data. Given a SISO LTI plant, we will address the problem of co-designing a digital controller and the network parameters (scheduling and routing) in order to guarantee stability and maximize a performance metric on the transient response to a step input, with constraints on the control effort, on the output overshoot and on the bandwidth of the communication channel. We show that the above optimization problem is a polynomial optimization problem, which is generally NP-hard. We provide sufficient conditions on the network topology, scheduling and routing such that it is computationally feasible, namely such that it reduces to a convex optimization problem.Comment: 51st IEEE Conference on Decision and Control, 2012. Accepted for publication as regular pape

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

LPV Control Synthesis for Sensor Senescence in Feedback Control System

The senescence of system sensor(s) probably causing degenerate system behavior or systembreakdown. Motivated by that, this work considers the synthesis of a gain scheduling controlfor linear parameter varying (LPV) system via linear matrix inequalities (LMIs) techniquessuch that sensors senescence information incorporated in the design of the controller. That is,the degradation of sensor effectiveness due to senescence is modeled by the variation of sensormeasurements’ noise co-variance. The sensors’ senescence information is incorporated as apart of the scheduling parameters for the LPV controller. The synthesis control matrices via linearmatrix inequalities have been re-structured and re-formalized in a way that they incorporatethe sensors senescence information to synthesize a gain scheduling dynamic output feedback(GS - DOF) control. That is, the existing GS - DOF control design LMIs have been modifiedto include the noise co-variance matrix. The significant achievement is the control design conditionsdescription of GS - DOF control in a way that ensures the desired integrated H2&H1 performances in the presence of sensors senescence, where sensors’ senescence information isincorporated as a part of the scheduling parameters for the LPV controller. In addition, two setsof controllers have been synthesized and studied. The simulation expresses the benefits of theproposed controllers, and closed loop system H1 and H2 performances are also studied. Thesynthesized controller ensures the performance associate with a closed loop, the closed loopsystem stability, and the scheme of control is simple enough for real time implementations

Fault Tolerant Control Schemes for Wireless Networked Control Systems with an Integrated Scheduler

In recent years, the wireless networked control systems (W-NCSs) has gained increasing popularity in industrial processes. To guarantee the system control performance, fault tolerant control (FTC) strategies have been proposed especially to deal with the malfunction in sensors, actuators or other system components. For the real-time requirement in industrial systems, the FTC performances of W-NCSs not only depend on the developed control algorithms but also on the network protocols at the medium access control (MAC) layer. These protocols, in form of schedulers, determine the transmission orders of messages and play significant roles in the control performances of W-NCSs. Under these circumstances, it is challenging but promising to investigate FTC schemes for W-NCSs with an integrated scheduler. This thesis is devoted to the development of FTC strategies for W-NCSs with an integrated scheduler. In the first part of this thesis, the procedures of integrating a scheduler into W-NCSs are introduced. Due to the requirement for deterministic transmission behaviors via the wireless network, the time division multiple access (TDMA) mechanism is adopted in W-NCSs. The TDMA-based scheduler is taken as a dynamic system and formulated into a periodic system. After that, with the integration of the scheduler, the W-NCSs are modeled as discrete linear time periodic (LTP) systems. The second part of this thesis focuses on the developments of FTC schemes for the integrated LTP systems. Two types of faults, i.e., additive faults (AFs) and multiplicative faults (MFs), are considered in our work. Specifically, a group of fault tolerant controllers are constructed for the AFs case, and seek to ensure that the outputs of LTP systems satisfy a set of H_infty performance indices. On the other hand, a lifting technology and an adaptive observer are applied to handle the situation of MFs. Due to the distribution of W-NCSs and the limitation of communication bandwidth, theorems are presented to solve the structure-restriction problem in the gains of observers and controllers. Finally, the derived FTC approaches are verified on an advanced experimental WiNC (wireless networked control) platform. Following the structure-restricted gains, the FTC strategies are realized with shared and unshared information (i.e., residual signals and state estimates), respectively. The results indicate that the system with shared information has achieved better FTC performances. In den letzten Jahren, haben die drahtlos vernetzten Steuerungssystemen (W-NCSs) sich zunehmender Beliebtheit in industriellen Prozessen gewonnen. Um die Systemsteuerleistung zu gewährleisten, sind die fehlertoleranten Regelung (FTC) Strategien vorgeschlagen worden, um vor allem mit der Fehlfunktion in Sensoren, Aktoren oder andere Systemkomponenten umzugehen. Für die Echtzeitanforderung in industriellen Systemen, hängen die FTC-Leistungen der W-NCSs nicht nur von den entwickelten Regleralgorithmen sondern auch von den Netzwerkprotokollen auf dem Medium Access Control (MAC)-Layer ab. Diese Protokolle, in Form von Schedulers, bestimmen die Reihenfolge der Übertragung der Nachrichten und spielen eine bedeutende Rolle in den Steuerleistungen von W-NCSs. Unter diesen Umständen ist es herausfordernd aber vielversprechend um FTC Regelungen für W-NCSs mit einem integrierten Scheduler zu untersuchen. Diese Arbeit widmet sich auf die Entwicklung von FTC Strategien für W-NCSs mit einem integrierten Scheduler. Im ersten Teil der Arbeit werden die Verfahren der Integration einen Scheduler in W-NCSs eingeführt. Aufgrund der Anforderung deterministisches Übertragungsverhalten über das drahtlose Netzwerk zu gewährleisten, wird der Time-Division-Multiple-Access (TDMA) Mechanismus gewählt. Der TDMA-basierte Scheduler ist als ein dynamisches System betrachtet und als ein Periodisches system formuliert. Danach, mit der Integration des Schedulers, werden die W-NCSs als diskrete Linear Time Periodic (LTP)-Systeme modelliert. Der zweite Teil der Arbeit konzentriert sich auf die Entwicklung der FTC Regelungen für die integrierten LTP-Systeme. Zwei Arten von Fehlern, d.h., additive Fehlern (AFs) und multiplikativen Fehlern (MFs), sind in unserer Arbeit berücksichtigt. Für LTP-Systeme mit AFs wird ein Satz von fehlertoleranten Reglern entworfen, dass die Ausganggröße eine Reihe von H_infty-Leistungsindizes erfüllen werden. Auf der anderen Seite, werden ein Hebetechnik und eine adaptive Beobachter angewendet, um den Fall von MFs zu behandeln. Aufgrund der Verbreitung der W-NCSs und gleichzeitiger Begrenzung der Kommunikationsbandbreite werden Theoreme vorgestellt, um das Problem der Strukturbeschränkung in den Beobachter- bzw. Reglermatrizen zu lösen. Abschließend werden die hergeleiteten FTC-Ansätze auf einem fortgeschrittenen WiNC (drahtlos vernetzten Regelung) Plattform überprüft. Nach den Beobachter- bzw. Reglermatrizen sind die FTC-strategien mit vollständig geteilter oder nicht geteilter Informationen (d.h., Residuum Signale und Schätzungen der Zustandsgrößen) realisiert worden. Die Ergebnisse zeigen, dass das System mit vollständig geteilten Informationen bessere FTC-Leistungen erzielt hat