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In this paper, we propose and analyze an attack detection scheme for securing the physical layer of a networked control system (NCS) with a wireless sensor network against attacks where the adversary replaces the true observations with stationary false data. An independent and identically distributed watermarking signal is added to the optimal linear quadratic Gaussian (LQG) control inputs, and a cumulative sum (CUSUM) test is carried out using the joint distribution of the innovation signal and the watermarking signal for quickest attack detection. We derive the expressions of the supremum of the average detection delay (SADD) for a multi-input and multi-output (MIMO) system under the optimal and sub-optimal CUSUM tests. The SADD is asymptotically inversely proportional to the expected Kullback–Leibler divergence (KLD) under certain conditions. The expressions for the MIMO case are simplified for multi-input and single-output systems and explored further to distil design insights. We provide insights into the design of an optimal watermarking signal to maximize KLD for a given fixed increase in LQG control cost when there is no attack. Furthermore, we investigate how the attacker and the control system designer can accomplish their respective objectives by changing the relative power of the attack signal and the watermarking signal. Simulations and numerical studies are carried out to validate the theoretical results.

While the use of unmanned vehicles (UxVs) within the Department of Defense (DOD) is prevalent, the ability of the DOD to operate these vehicles as a cooperative networked control system (NCS) is not fully developed. A MATLAB simulation modeling a UxV NCS that jointly optimizes sensing and data communications utilities currently exists. However, this implementation is of low fidelity and is not readily extensible. This thesis advances the NCS model by converting the MATLAB simulation into Python with an object-oriented design. We further extend the Python NCS simulation into a truly distributed system, where each node executes in an independent Docker container and communicates with other nodes via reliable message communications. Our implementation results demonstrated that the object-oriented Python simulation incurs a performance penalty with respect to execution times but provides for greater extensibility without changes to existing functionality. Furthermore, Docker containers offer a lightweight solution for modeling a more realistic version of UxV simulations, thus increasing the NCS simulation's fidelity., Outstanding Thesis, Lieutenant Commander, United States Navy, Lieutenant, United States Navy, Approved for public release. Distribution is unlimited.

Adding a physical watermarking signal to the control input of a networked control system increases the detection probability of data deception attacks at the expense of increased control cost. This paper proposes a parsimonious policy to limit the average number of watermarking events when the attack is not present, which in turn reduces the control cost. We model the system as a stochastic optimal control problem and apply dynamic programming to minimize the average detection delay (ADD) for fixed upper bounds on false alarm rate (FAR) and an average number of watermarking events (ANW) before the attack. Under practical circumstances, the optimal solution results in a two threshold policy on the posterior probability of attack, derived from the Shiryaev statistics for sequential change detection and assuming the change point is a random variable. We derive asymptotically approximate analytical expressions of ADD and FAR, applying the non-linear renewal theory for non-independent and identically distributed data. The derived expressions reveal that ADD reduces with the increase in the Kullback-Leibler divergence (KLD) between the post-and pre-attack distributions of the test statistics. Therefore, we further design the optimal watermarking that maximizes the KLD for a fixed increase in the control cost. The relationship between the ANW and the increase in control cost is also derived. Simulation studies are performed to illustrate and validate the theoretical results.

As the number of cyber-physical systems rises, it becomes increasingly crucial to study Networked Control Systems (NCSs) combining control communication co-design. This nature of NCSs has led to task-specific approaches to research, creating a dearth of generalizable, repeatable, and scalable experimentation. Further, with the advent of edge computing solutions, it is of paramount importance to explore its relevance in such applications. In this work, we present CLEAVE, a novel, completely software-based framework for repeatable and scalable experimentation in edge native NCSs. Our approach is based on the emulation of physical plants communicating over a real network with software-based controllers. CLEAVE is designed and built for the edge, using Python3 and with full compatibility with industry-standard containerization solutions. Although designed for single-loop emulations, the flexibility afforded by the aforementioned characteristics allow our framework to be adapted to a multitude of complex scenarios. We validate CLEAVE using an initial implementation of an inverted pendulum NCS. Our results showcase the utility of the tool as a repeatable, extensible, and scalable solution to NCS performance evaluation and benchmarking on the Edge., Part of proceedings: ISBN 978-1-4503-9253-2QC 20220428

Networked control systems (NCS) are widely used in real world applications because of their advantages, such as remote operability and reduced installation costs. However, they are prone to various inaccuracies in execution like delays, packet dropouts, inaccurate sensing and quantization errors. To ensure safety of NCS, their models have to be verified under the consideration of aforementioned uncertainties. In this paper, we tackle the problem of verifying safety of models of NCS under uncertain sampling time, inaccurate output measurement or estimation, and unknown disturbance input. Unbounded-time safety verification requires approximation of reachable sets by invariants, whose computation involves set operations. For uncertain linear dynamics, two important set operations for invariant computation are linear transformation and Minkowski sum operations. Zonotopes have the advantage that linear transformation and Minkowski sum operations can be efficiently approximated. However, they can not encode directions of convergence of trajectories along complex eigenvectors, which is closely related to encoding invariants. Therefore, we extend zonotopes to the complex valued domain by a representation called complex zonotope, which can capture contraction along complex eigenvectors for determining invariants. We prove a related mathematical result that in case of accurate feedback sampling, a complex zonotope will represent an invariant for a stable NCS. In addition, we propose an algorithm to verify the general case based on complex zonotopes, when there is uncertainty in sampling time and in input. We demonstrate the efficiency of our algorithm on benchmark examples and compare it with a state-of-the-art verification tool.

In this paper, we study the robust stability of a networked control system (NCS) under the framework of infinite-dimensional discrete-time linear time-varying (LTV) systems. The NCS consists of a pair of uncertain plant and controller, as well as an uncertain bilateral communication channel in between. The uncertainties in the plant and controller are measured by the gap metric. The communication channel between the plant and controller is described by a cascade of two-port networks whose transmission matrices are subject to norm-bounded additive uncertainties. Such an uncertain two-port network can model distortions and interferences occurring during control and measurement signal transmissions. The causality of the LTV subsystems is characterized by using nest algebras. A necessary and sufficient condition for the robust stability of the NCS, with the causality of all system components explicitly considered, is established in the form of an arcsine inequality which generalizes a similar result for linear time-invariant NCSs. © 2021 Society for Industrial and Applied Mathematics

A networked control system (NCS) is a single system composed of multiple discrete agents, and is often modeled as a graph of nodes (agents) and connecting edges (communications links). NCS technology is increasingly important for control of autonomous vehicles (UxVs). Proper placement of the NCS elements is vital to mission effectiveness, but finding optimal NCS configurations is almost always computationally prohibitive. In this thesis, we explore using submodularity to solve this problem. This approach gives near-optimality guarantees while reducing the complexity of the problem, allowing solutions to be found in near real-time. A simple, novel distributed submodular approach to NCS control was developed, with simulation and analysis provided for an expeditionary warfare scenario., http://archive.org/details/distributedsubmo1094564926, Outstanding Thesis, Lieutenant, United States Navy, Approved for public release; distribution is unlimited.

Priority-based scheduling strategies are often used to resolve contentions in resource constrained control systems. Such scheduling strategies inevitably introduce time delays into controls and may degrade the performance of control systems. Considering the coupling between priority assignment and control, this paper presents a method to co-design priority assignments and control laws for each control system, which aims to minimize the overall performance degradation caused by contentions. The co-design problem is formulated as a mixed integer optimization problem with a very large search space, rendering difficulty in computing the optimal solution. To solve the problem, we develop a novel contention-resolving model predictive control method to dynamically assign priorities and compute an optimal control. The priority assignment can be determined using a sample-based approach without excessive demand on computing resources, and optimal controls can be computed iteratively following the order of the assigned priorities. We apply the proposed contention-resolving model predictive control to co-design scheduling and controls in networked control systems. We present simulation results to show the effectiveness of our proposed method. © 2020 Elsevier Ltd

© 2019 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.", [EN] In this paper, periodic event-triggered sampling and dual-rate control techniques are integrated in a wireless networked control system (WNCS), where time-varying network-induced delays and packet disorder are present. Compared to the conventional time-triggered sampling paradigm, the control solution is able to considerably reduce network utilization (number of transmissions), while retaining a satisfactory control performance. Stability for the proposed WNCS is ensured using linear matrix inequalities. Simulation results show the main benefits of the control approach, which are experimentally validated by means of an unmanned-aerial-vehicle-based test-bed platform.

In this paper, we propose a method to improve the networked UAV control system using event-triggered control and model predictive control (MPC). Although the UAV control over the network has many advantages, it involves a long-time delay and packet loss, which adversely affect real-time control performance. Delay compensation algorithms in the networked control system (NCS) have been proposed to address such issues, however, they do not consider the resource limit of the network so that the network congestion may occur. In that case, the packet loss and network delay issues can even be worsened. In this study, we propose a method to reduce the generation of less important control signals and to use the network more efficiently by using event-triggered control. Since the event-triggered control method is also influenced by the network delay, an event trigger function suitable for NCS is designed. We validated the effectiveness of networked UAV control system and event-triggered control by simulation., QC 20200115

In this paper, we introduce the method of two-way coding, a concept originating in communication theory characterizing coding schemes for two-way channels, into (networked) feedback control systems under injection attacks. We first show that the presence of two-way coding can distort the perspective of the attacker on the control system. In general, the distorted viewpoint on the attacker side as a consequence of two-way coding will facilitate detecting the attacks, or restricting what the attacker can do, or even correcting the attack effect. In the particular case of zero-dynamics attacks, if the attacks are to be designed according to the original plant, then they will be easily detected; while if the attacks are designed with respect to the equivalent plant as viewed by the attacker, then under the additional assumption that the plant is stabilizable by static output feedback, the attack effect may be corrected in steady state., Part of ISBN 978-1-4503-6285-6QC 20191011, CERCES

In this paper, we study the networked stabilization of a continuous-time multi-input system wherein the multiple control inputs are transmitted through a small number of shared channels with stochastic multiplicative uncertainties. Transmission scheduling over the shared channels needs to be performed so that at any time instant, each channel transmits only one control input. The main novelty of this work lies in the idea of scheduling/control co-design which suggests that the design of the transmission scheduling and the controller should be treated jointly rather than separately. By virtue of such a co-design, a sufficient condition is obtained for the channels' overall quality of service required for stabilization given in terms of twice of the topological entropy of the plant. A numerical example is provided to illustrate our result. (C) 2018 Elsevier Ltd. All rights reserved.

To obtain accurate trajectory tracking with robustness and faithful force feedback in a practical application, a sliding mode controller (SMC) combined with a compensation controller based on a nonlinear disturbance observer (DOB) is proposed. The DOB estimates the disturbances arising mainly from the uncertain dynamic model of a surgical manipulator, frictional forces and external interaction forces, and compensates for these disturbances in the control law. Accordingly, it alleviates the chattering problem caused by th

We consider the communication channel pricing and selection problem in a networked control system. To encompass the sequentialized nature of the decision-making process, we use game theory and formulate a Stackelberg game framework, where the server first determines the channel pricing strategy, and the clients then make channel selection decisions. Both single-server-single-client (SSSC) scenario and single-server-multi-client (SSMC) scenario are discussed. The existence of an optimal stationary and deterministic policy for the clients is proved. We show that for the SSSC scenario, the server's optimal pricing strategy in terms of maximizing revenue is to ensure that the client uses the good channel all the time. For the SSMC scenario, it is assumed that the channel price remains invariant. As a consequence, each client has an optimal policy with threshold structure. Some properties of the optimal policy pair for both scenarios are obtained. Simulation results confirm the structure and properties of both the server and clients' optimal strategies.

This study is concerned with the output-based resilient event-triggered control for networked control systems (NCSs) subject to denial of service (DoS) attacks, where 'resilient' is interpreted as that the NCSs can tolerate a larger time delay with a certain degree of performance degradation when there are DoS attacks. Otherwise, the NCSs run with $H-{\infty }$H∞ performance. In order to characterise DoS attacks, an additional positive term which implies the effects of DoS attacks is imposed on the pre-designed triggering condition. By considering the fact that only partial output measurements can be obtained, the output-based security performance analysis as well as an output feedback controller design under the proposed event-triggered strategy is conducted with Lyapunov-Krasovskii method and linear matrix inequalities technique. At last, the simulation results show that the designed controller is resilient to DoS attacks with less dependent on the transmission packets while sacrificing some control performance.

In this work, Periodic Event-Triggered Sampling (PETS) and dual-rate control techniques are integrated in a Wireless Networked Control System (WNCS), where time-varying network-induced delays and packet disorder are present. Compared to the conventional Time- Triggered Sampling (TTS) paradigm, the control solution is able to considerably reduce network utilization (number of transmissions), while retaining a satisfactory control performance. Stability for the proposed WNCS is assured using Linear Matrix Inequalities (LMIs). Simulation results show the main benefits of the control approach, which are experimentally validated by means of an Unmanned Aerial Vehicle (UAV) based test-bed platform.

This note studies the linear quadratic ( LQ) optimal control of continuous-time linear time-invariant systems with random gains imposed on the input channels. We start from the indefinite LQ problem, in which the cost weighting matrix can be indefinite. The definite LQ problem is discussed as a special case. The main novelty originates from the point of view that in networked control, designing the channels and controller jointly often leads to an easier problem and achieves better performance than designing them separately. Specifically, we formulate the LQ problem as a channel/controller co-design problem assuming that the channel capacities can be allocated among the input channels subject to an overall capacity constraint. Necessary and sufficient conditions are obtained for the well-posedness and the attainability of the indefinite LQ problem under a given channel capacity allocation satisfying the stabilization requirement. The optimal controller is given by a linear state feedback associated with the mean-square stabilizing solution of a modified algebraic Riccati equation., QC 20160825

This note studies the linear quadratic ( LQ) optimal control of continuous-time linear time-invariant systems with random gains imposed on the input channels. We start from the indefinite LQ problem, in which the cost weighting matrix can be indefinite. The definite LQ problem is discussed as a special case. The main novelty originates from the point of view that in networked control, designing the channels and controller jointly often leads to an easier problem and achieves better performance than designing them separately. Specifically, we formulate the LQ problem as a channel/controller co-design problem assuming that the channel capacities can be allocated among the input channels subject to an overall capacity constraint. Necessary and sufficient conditions are obtained for the well-posedness and the attainability of the indefinite LQ problem under a given channel capacity allocation satisfying the stabilization requirement. The optimal controller is given by a linear state feedback associated with the mean-square stabilizing solution of a modified algebraic Riccati equation.

Our society is witnessing an unprecedented, enduring, and pervasive aging process. With more and more people requiring walking assistance, the demand for gait physical therapy and rehabilitation has increased rapidly over the years. Current gait rehabilitation therapy relies on physical therapists to make evaluations and provide manual assistance, which is inaccurate and labor intensive. Introducing mechatronic techniques into gait rehabilitation can significantly improve the diagnosis and correction of gait abnormalities. This dissertation proposes a network-based gait rehabilitation system (NGRS) to achieve in-home rehabilitation, with physical therapists monitoring the rehabilitation training progress remotely.The NGRS includes two main components: a wireless human motion monitoring system for gait analysis and a robotic assistive device controlled wirelessly for active gait correction. The NGRS is clearly a cyber-physical system (CPS) since it involves sensors and actuation devices, communication networks, and computational resources for perception and control. A general design framework is proposed for the design of CPS and the NGRS is developed using this framework as an example. This dissertation is divided into two parts, with the first part handling motion perception and gait analysis, and the second part developing fundamental networked control approaches for the robotic assistive device.In the first part, design of the wireless human motion monitoring system is illustrated. The system includes a pair of wireless smart shoes embedded with barometric sensors for gait phase detection, and several wireless joint angle sensors for joint kinematic analysis. User interfaces are developed on both a laptop and an iPad to demonstrate processed sensory data as real-time visual feedback. It is shown that the sensory data make it more convenient and accurate to distinguish pathological gait from normal gait. Clinical effectiveness of visual feedback is verified with 2

Control systems which use a communication network as a communication medium are the focus of this thesis. These systems are widely recognized as Networked Control Systems (NCSs). In particular, we consider NCSs in which the corresponding network induces two communication issues. One of them is a packet dropout(s) while the other is scheduling. To mitigate the undesirable effects of packet dropouts and scheduling, such as instability or deteriorated performance, we use a protocol and controller co-design. More precisely, we use a Model Predictive Control (MPC) framework and the flexible nature of NCS architecture which allows for distributed computation. Considering a specific NCS architecture affected with packet dropouts and/or scheduling we focus on stability, robustness and controllability properties of the corresponding NCS. In particular, we begin by considering stability property of a NCS in which the corresponding network is located between the controller output and the plant input. The network is prone to packet dropouts and it induces scheduling of its communication resource. To address these communication constraints we employ a protocol and controller co-design and show stability, in particular, Uniform Global Asymptotic Stability (UGAS) of the corresponding NCS state. We use two approaches to establish this result. One approach consists of finding an appropriate Lyapunov function while the other approach uses a cascade idea. Following this is an investigation of the same NCS architecture with the difference that it is governed not with a standard MPC controller but an Economic MPC controller. Here we combine several recently established results for an Economic MPC in a way so that our result can be applied off the shelf to establish UGAS of the corresponding NCS state. We then proceed by considering robustness properties of the same NCS architecture. In particular, we consider the case where, additionally, the plant is affected with exogenous disturbance

[EN] In this work, a non-uniform multi-rate control strategy is applied to a kind of Networked Control System (NCS) where a wireless path tracking control for an Unmanned Ground Vehicle (UGV) is carried out. The main aims of the proposed strategy are to face time-varying network-induced delays and to avoid packet disorder. A Markov chain-driven NCS scenario will be considered, where different network load situations, and consequently, different probability density functions for the network delay are assumed. In order to assure mean-square stability for the considered NCS, a decay-rate based sufficient condition is enunciated in terms of probabilistic Linear Matrix Inequalities (LMIs). Simulation results show better control performance, and more accurate path tracking, for the scheduled (delay-dependent) controller than for the non-scheduled one (i.e. the nominal controller when delays appear). Finally, the control strategy is validated on an experimental test-bed.

Este trabajo presenta una técnica de diseño novedosa para la estimación y control distribuido de sistemas en red. Se considera un proceso discreto de gran escala controlado por una red de agentes que pueden recopilar información acerca de la evolución de la planta y aplicar las acciones de control para mejorar su comportamiento. El diseño propuesto es de especial interés cuando no se tiene observabilidad/controlabilidad local, de forma que es necesario utilizar la comunicación entre agentes para tener suficiente información dinámica del sistema.El objetivo global es diseñar un esquema de control y estimación distribuida, de forma que se obtengan estimaciones fiables por parte de los agentes así como un desempeño de control adecuado. El trabajo analiza dos esquemas diferentes de comunicación entre agentes, muestreo periódico y basado en eventos, proporcionando pruebas de estabilidad utilizando el criterio de Lyapunov y métodos de diseño en términos de desigualdades matriciales lineales LMIs (del inglés, Linear Matrix Inequalities). Se muestran resultados experimentales sobre un sistema de cuatro tanques para demostrar la eficacia de las metodologías propuestas., This paper's aim is to present a novel design technique for distributed control and estimation in networked systems. The proposed problem considers a large scale, discrete LTI process controlled by a network of agents that may both, collect information about the evolution of the plant, and apply control actions to drive its behavior. The problem makes full sense when local observability/controllability is not assumed and the communication between agents can be exploited to reach system-wide goals, including energy efficiency in these communications. The objective is to provide a fully distributed estimation&control scheme that stabilizes the plant while the upper bound of a given quadratic performance index is minimized. The paper analyzes two different sampling schemes, periodic and event-driven, providing stability proofs based on Lyapunov theory and design methods in terms of LMIs. Experimental results on a four couple tanks system are provided to show the performance of the proposed methodologies.

[EN] This paper's aim is to present a novel design technique for distributed control and estimation in networked systems. The proposed problem considers a large scale, discrete LTI process controlled by a network of agents that may both, collect information about the evolution of the plant, and apply control actions to drive its behavior. The problem makes full sense when local observability/controllability is not assumed and the communication between agents can be exploited to reach system-wide goals, including energy efficiency in these communications. The objective is to provide a fully distributed estimation&control scheme that stabilizes the plant while the upper bound of a given quadratic performance index is minimized.The paper analyzes two different sampling schemes, periodic and event-driven, providing stability proofs based on Lyapunov theory and design methods in terms of LMIs. Experimental results on a four couple tanks system are provided to show the performance of the proposed methodologies., [ES] Este trabajo presenta una técnica de diseño novedosa para la estimación y control distribuido de sistemas en red. Se considera un proceso discreto de gran escala controlado por una red de agentes que pueden recopilar información acerca de la evolución de la planta y aplicar las acciones de control para mejorar su comportamiento. El diseño propuesto es de especial interés cuando no se tiene observabilidad/controlabilidad local, de forma que es necesario utilizar la comunicación entre agentes para tener suficiente información dinámica del sistema. El objetivo global es diseñar un esquema de control y estimación distribuida, de forma que se obtengan estimaciones fiables por parte de los agentes así como un desempeño de control adecuado. El trabajo analiza dos esquemas diferentes de comunicación entre agentes, muestreo periódico y basado en eventos, proporcionando pruebas de estabilidad utilizando el criterio de Lyapunov y métodos de diseño en términos de desigualdades matriciales lineales LMIs (del inglés, Linear Matrix Inequalities). Se muestran resultados experimentales sobre un sistema de cuatro tanques para demostrar la eficacia de las metodologías propuestas.

In this paper, the networked control system (NCS) in continuous-time with sampled data is considered. The transmission channel is assumed to locate at the plant input, and introduce both logarithmic quantization and fading. The proper definition of channel capacity for such an NCS is presented. The capacity being greater than the topological entropy is found to be the necessary and sufficient condition for stabilizability for the single-input case. For the multi-input case, the sufficiency of the inequality is proved by means of channel resource allocation. © 2014 IEEE.

In this paper, the networked control system (NCS) in continuous-time with sampled data is considered. The transmission channel is assumed to locate at the plant input, and introduce both logarithmic quantization and fading. The proper definition of channel capacity for such an NCS is presented. The capacity being greater than the topological entropy is found to be the necessary and sufficient condition for stabilizability for the single-input case. For the multi-input case, the sufficiency of the inequality is proved by means of channel resource allocation. © 2014 IEEE.

This is an Accepted Manuscript of an article published by Taylor & Francis in International Journal of Systems Science on 2014, available online:http://www.tandfonline.com/10.1080/00207721.2013.844286, When a process ¿eld bus-decentralized peripherals (Pro¿bus-DP) network is used in an industrial environment, a deterministic behaviour is usually claimed. However, due to some concerns such as bandwidth limitations, lack of synchronisation among different clocks and existence of time-varying delays, a more complex problem must be faced. This problem implies the transmission of irregular and, even, random sequences of incomplete information. The main consequence of this issue is the appearance of different sampling periods at different network devices. In this paper, this aspect is checked by means of a detailed Pro¿bus-DP timescale study. In addition, in order to deal with the different periods, a delay-dependent dual-rate proportional-integral-derivative control is introduced. Stability for the proposed control system is analysed in terms of linear matrix inequalities

This paper presents an MPC based controller and network protocol co-design strategy for networked control systems with multiple controller-actuator links. These links are closed via unreliable data-like network which allows access to only one actuator node at each time instant. The concept of nonlinear gains is used to show that in the case of uniform boundedness of the number of consecutive packet dropouts, nonlinear gain ℓ2 stability can be ensured via appropriate choice of design parameters. Numerical simulations illustrate the potential of the proposed strategy.

In this paper, we study the problem of state feedback stabilization of a linear time-invariant (LTI) discrete-time multi-input system with imperfect input channels. Each input channel is modeled in three different ways. First it is modeled as an ideal transmission system together with an additive norm bounded uncertainty, introducing a multiplicative uncertainty to the plant. Then it is modeled as an ideal transmission system together with a feedback norm bounded uncertainty, introducing a relative uncertainty to the plant. Finally it is modeled as an additive white Gaussian noise channel. For each of these models, we properly define the capacity of each channel whose sum yields the total capacity of all input channels. We aim at finding the least total channel capacity for stabilization. Different from the single-input case that is available in the literature and boils down to a typical H-infinity or H-2 optimal control problem, the multi-input case involves allocation of the total capacity among the input channels in addition to the design of the feedback controller. The overall process of channel resource allocation and the controller design can be considered as a case of channel-controller co-design which gives rise to modified nonconvex optimization problems. Surprisingly, the modified nonconvex optimization problems, though appear more complicated, can be solved analytically. The main results of this paper can be summarized into a universal theorem: The state feedback stabilization can be accomplished by the channel-controller co-design, if and only if the total input channel capacity is greater than the topological entropy of the open-loop system.

In this paper, we study the stabilization of networked control systems with multirate sampling. The input channels are modeled in two different ways. First, each of them is modeled as the cascade of a downsampling circuit, an ideal transmission system together with an additive norm bounded uncertainty, and a discrete zero-order hold. Then each input channel is modeled as the cascade of a downsampling circuit, an ideal transmission system together with a feedback norm bounded uncertainty, and a discrete zero-order hold. For each channel model, different downsampling rates are allowed in different input channels. The minimum total channel capacity required for stabilization is investigated. The key idea of our approach is the channel resource allocation, i.e., given the total capacity of the communication network, we do have the freedom to allocate the capacities among different input channels. With this new idea, we successfully show that the multirate networked control system with each channel model can be stabilized by state feedback under an appropriate resource allocation, if and only if the total network capacity is greater than the topological entropy of the plant. We also apply the result to multirate quantized control systems. Both the commonly used logarithmic quantizer and the alternative logarithmic quantizer are considered. For each case, a sufficient condition for stabilization is obtained which involves a trade-off between the densities of time quantization and spatial quantization. (c) 2013 Elsevier Ltd. All rights reserved.

The gas turbine engine environment is particularly harsh with regards to temperature and vibration, and trends indicate that these conditions will continue to grow much more severe, especially in temperature. Conventional bulk epitaxial silicon-based electronics are used only in limited locations on engines today in support of instrumentation and production sensing and controls, and their use may be even more restricted by future operating conditions. This trend is moving in a direction contrary to on-going efforts to incorporate more intelligence into the engine, and to localize that intelligence as close as possible to the sensors, actuators and components to minimize the use of large wiring bundles. Current approaches allowing on-engine use of electronics typically involve some sort of thermal management technique, such as the use of liquid cooling loops, including nitrogen for instrumentation and fuel for controls, as well as convective air cooling by strategic placement of electronics. However, these passive cooling techniques are often inadequate to ensure necessary reliability and durability, and the active techniques are typically cumbersome and costly, and don t lend themselves to in-product applications. An alternative to addressing the environment in which the electronics are required to operate is addressing the robustness of the electronics themselves, in particular with regards to high temperature capability., Presented at the 58th International Instrumentation Symposium held in San Diego, CA on 4-7 June 2012. The original document contains color images. Prepared in cooperation with Pratt & Whitney, Honeywell, BAE Systems, Rolls-Royce, GE Aviation, Hamilton Sundstrand, and the Ohio Aerospace Institute.

Herein we present an algorithm for controlling LTI processes using an adaptive sampling interval where the controller at every sampling instant not only computes the new control command but also decides the time interval to the next sample. The approach relies on MPC where the cost function depends on the control performance as well as the cost for sampling. The paper presents a method for synthesizing such a predictive controller and gives explicit conditions for when it is stabilizing. Further it is shown that the optimization problem may be solved off-line and that the controller may be implemented as a lookup table of state feedback gains. The paper is concluded with a numerical example., QC 20130103

This paper addresses the mean square stabilization problem for discrete-time networked control systems over fading channels. We show that there exists a requirement on the network over which an unstable plant can be stabilized. In the case of state feedback, necessary and sufficient conditions on the network for mean square stabilizability are derived. Under a parallel transmission strategy and the assumption that the overall mean square capacity of the network is fixed and can be assigned among parallel input channels, a tight lower bound on the overall mean square capacity for mean square stabilizability is presented in terms of the Mahler measure of the plant. The minimal overall capacity for stabilizability is also provided under a serial transmission strategy. For the case of dynamic output feedback, a tight lower bound on the capacity requirement for stabilization of SISO plants is given in terms of the anti-stable poles, nonminimum phase zeros and relative degree of the plant. Sufficient and necessary conditions are further derived for triangularly decoupled MIMO plants. The effect of pre- and post-channel processing and channel feedback is also discussed, where the channel feedback is identified as a key component in eliminating the limitation on stabilization induced by the nonminimum phase zeros and high relative degree of the plant. Finally, the extension to the case with output fading channels and the application of the results to vehicle platooning are presented.

In this paper, the Linear Quadratic Gaussian (LQG) control of linear time invariant (LTI) systems with random input and output gains is studied. One main novelty of this work is that we study the problem under the framework of channel/controller co-design which allows the control designer to have the additional freedom to design the communication channels. With the channel/controller co-design, the optimal control problem studied is feasible if and only if the system is mean-square stabilizable and detectable. Moreover, we show that the separation principle partially holds under the TCP-like protocols. The optimal controller is an estimated state feedback, combining the optimal state feedback design and the optimal state estimation design. However, there exists certain asymmetry. The optimal state feedback gain does not depend on the estimator design, while the optimal estimator does depend on the optimal state feedback gain. © 2012 IEEE.

This paper studies the design and real-time implementation of an event-triggered controller for a nonlinear 3D tower crane where the communication between the controller and the actuators is performed over a low-power wireless network. A flexible Event-Generation Circuit (EGC) is proposed in order to implement event-driven controllers for Networked Control Systems. Furthermore, a detailed experimental analysis on the performance of the event-triggered controller and the influence of packet losses on the transmitted actuation messages are presented. The results show that the event-triggered controllers in networked control systems are able to maintain the same level of performance as compared to periodic controllers, while increasing the sensors/actuators lifetime by reducing network bandwidth utilization., QC 20120207

The final publication is available at Springer via http://dx.doi.org/10.1007/s12555-011-0621-5, This paper presents a Non-Uniform Predictor-Observer (NUPO) based control approach in order to deal with two of the main problems related to Networked Control Systems (NCS) or Sensor Networks (SN): time-varying delays and packet loss. In addition, if these delays are longer than the sampling period, the packet disordering phenomenon can appear. Due to these issues, a (scarce) nonuniform, delayed measurement signal could be received by the controller. But including the NUPO proposal in the control system, the delay will be compensated by the prediction stage, and the nonavailable data will be reconstructed by the observer stage. So, a delay-free, uniformly sampled controller design can be adopted. To ensure stability, the predictor must satisfy a feasibility problem based on a time-varying delay-dependent condition expressed in terms of Linear Matrix Inequalities (LMI). Some aspects like the relation between network delay and robustness/performance trade-off are empirically studied. A simulation example shows the benefits (robustness and control performance improvement) of the NUPO approach by comparison to another similar proposal. © ICROS, KIEE and Springer 2011.

n this paper, a methodology to design controllers able to cope with different load conditions on an Ethernet network is introduced. Load conditions induce time-varying delays between measurements and control. To face these variations an interpolated, delay-dependent gain scheduling law is used. The lack of synchronization is solved by adopting an event-based control approach. The dual-rate control action computation is carried out at a remote controller, whereas control actions and measurements are taken out locally at the controlled process site. Stability is proved in terms of probabilistic linear matrix inequalities. TrueTime simulations in an Ethernet case show the benefit of the proposal, which is later validated on an experimental test-bed Ethernet environment.

International audience, A helicopter-drone is presently in design phase in our laboratory, within the frame of a research project. The purpose of this drone is to serve as a benchmark and to be sufficiently open in order to test several control or diagnostic strategies, in a Networked Embedded Control Systems approach. The benchmark will comprise an embedded network on the drone itself, and a wireless network for communication with the ground station(s). A model of the drone is proposed in this paper. This model is composed of the model of the drone itself in Matlab-Simulink together with the model of the network in True-Time. Some results are proposed in the paper concerning the influence of network faults on the diagnostic.

International audience, The development of new technologies for automation, particularly the use of networks (notably wireless networks) and the generalisation of digital components, allows envisaging their use in several kinds of applications, with an induced low cost, particularly in embedded systems. When designing such digital-based systems, we must take care of the dependability level of these systems. Due to the complexity of these architectures, it is not trivial to evaluate this dependability level. The present paper proposes a modelling strategy in order to achieve this evaluation, with an application to a control loop.

International audience, The validation of network systems is mandatory to guarantee the dependability levels, that international standard impose in many safety-critical applications. Due to the complexity of networked control system architectures, it is not trivial to evaluate there dependability level. The present paper aims at bringing a contribution relative to this aspect. Since the medium is the most critical components, we focus our interest on analysing the effect of the transmission errors on the dependability parameter of an NCS. Transmission errors occur when perturbations attack the medium, and affect messages circulating on the medium. Our approach consists of modelling the functional behaviour of classical control system components, and both functional and dysfunctional behaviour of the network. Dependability parameters are evaluated by simulation.