Stabilization of Networked Control Systems Under Clock Offsets and Quantization

Output feedback stabilization for Markov-based nonuniformly sampled-data networked control systems

The problem of stabilization of networked control systems (NCSs) with time-varying transmission delays is investigated. The time-varying delays lie in any two adjoining sampling instants of the plant. A technique is proposed for designing stabilizing controllers by converting NCSs with time-varying transmission delays into parameter uncertain systems with constant input delay, then the theory of robust stabilization of delay systems can be applied to solving this problem. Sufficient condition on stabilization of such NCSs is developed in terms of linear matrix inequality.

The stochastic stabilisation of networked control systems is investigated with a special focus on the lossy multi‐packet transmission in the wireless communication context. The resulting partially available system states due to multi‐packet transmission are firstly reconstructed at the controller, and the sufficient conditions for stochastic stability are then given for the closed‐loop system, which finally leads to a controller design method with explicit consideration of multi‐packet transmission. The proposed theoretical results are verified by both numerical and TrueTime‐based examples.

The problem of stabilization of networked control systems (NCSs) with data packet dropout is studied. Sufficient conditions are presented on the stability and stabilization of the NCSs with packet dropout. The novelty of this work lies in that NCSs with arbitrary but finite data packet dropout are modelled as switched linear systems, and this enables us to apply the result of switched systems to the analysis and synthesis of such NCSs. The admissible upper bound of the dropped packets can be determined by a set of linear matrix inequalities (LMIs) which guarantee the stability of the NCSs. Stabilizing controllers (via state feedback and static output feedback) can be constructed by solving a set of LMIs. Also, for an NCS with a convergence rate constraint, similar results are obtained. Examples are worked out to illustrate the effectiveness of the proposed method

The presence of a communication network in a control loop induces many imperfections such as varying transmission delays, varying sampling/transmission intervals, packet loss, communication constraints and quantization effects, which can degrade the control performance significantly and even lead to instability. Various techniques have been proposed in the literature for stability analysis and controller design for these so-called networked control systems. The aim of this chapter is to survey the main research lines in a comprehensive manner.

New stability criteria and stabilization methods on networked control systems (NCSs) with short time-varying delay (STVD) are proposed in this paper. An NCS with STVD is transformed into a time-varying discrete time system. And then, this discrete time system is converted into a equivalent time-invariant system with norm-bounded uncertainties by using robust control techniques. Using this method, the conservatism of the stability condition caused by STVD can be reduced. Based on that, a single norm-bounded uncertainty is replaced by N norm-bounded uncertainties to further reduce conservatism. Theoretical analysis shows that when N is increased, the stability condition becomes less conservative. For a fixed sampling period, the obtained stability conditions explicitly depend on the upper and lower bounds of the time delay. The existence condition and design method for the controllers are also presented. Finally, three numerical examples are provided to demonstrate the effectiveness of the proposed scheme.

This paper investigates the feedback stabilization problem for networked control systems (NCSs) with unknown disturbances, where sensors and actuators communicate with a remote controller over a multi-purpose network. A new control scheme, which relies on both information-theoretic and control-theoretic tools, is proposed to stabilize linear discrete-time plants. A sufficient condition for stabilization is derived. Simulation results show the validity of the proposed control scheme.

This paper studies the stabilization of Networked Control Systems (NCS) with communication constraints, variable delays and variable sampling intervals. The system sensor nodes are supposed to be distributed over a network. The scheduling of sensor information towards the controller is ruled by a quadratic protocol. This protocol first compares the weighted errors of the signals in individual nodes, where the error is the difference between the most recently activated signal at the sensor side and its current value, and then transmits the measurement from the node with the largest error. The closed-loop system has the form of a hybrid system with delays in the continuous dynamics and in the reset conditions. A new Lyapunov-Krasovskii method is developed for the partial exponential stability with respect to the x-variable of the delayed hybrid system. Polytopic uncertainties in the system model can be easily included in our analysis. The efficiency of the time-delay approach is illustrated on the cart-pendulum and the batch reactor benchmark problems. Our results improve the hybrid system-based ones and allow non-small network-induced delay.

A wireless networked control systems (NCS) is a control system whose feedback path is realized over a wireless communication network. The stability of such systems can be problematic given the random way in which wireless channels drop feedback messages. This paper establishes sufficient conditions for the almost sure stability of NCS under random dropouts. These conditions relate the burstiness in the dropout process to the nominal response of the controlled system. In particular, this means that the burstiness of the dropout process provides a convenient quality-of-service (QoS) constraint on the wireless channel that can be used to adaptively reconfigure the control system in a manner that guarantees the almost sure stability of the NCS. We also show how a probabilistic extension of the network calculus can be used to reconfigure multi-hop communication networks so this paper's sufficient stability condition is not violated.

A robust control approach to stabilization of networked control systems with time-varying delays

Attack-model-independent stabilization of networked control systems under a jump-like TOD scheduling protocol

A switched system approach is proposed to model networked control systems (NCSs) with communication constraints. This enables us to apply the rich theory of switched systems to analyzing such NCSs. Sufficient conditions are presented on the stabilization of NCSs. Stabilizing state/output feedback controllers can be constructed by using the feasible solutions of some linear matrix inequalities (LMIs). The merit of our proposed approach is that the behavior of the NCSs can be studied by considering switched system without augmenting the system. A simulation example is worked out to illustrate the effectiveness of the proposed approach.

Although there has been a lot of work about the synthesis and analysis of networked control systems (NCSs) with quantizers as well as NCSs with packet losses, most results are developed for the case of considering the quantizers and packet losses separately (either only concentrating on the data quantization or only focussing on the packet losses). In this paper, we address the synthesis approach of model predictive control (MPC) for NCSs subject to both data quantization and packet losses. This is motivated by the fact that it is common and natural in NCSs that the issues of the quantization and packet losses are coexisting. We firstly propose a novel model to describe the state and input quantization and the packet losses of the NCS in a unified framework. Further, from the new model, a MPC strategy is developed, which can guarantee the recursive feasibility. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.

This study addresses the stabilisation problem for networked control systems with random time delays. Depending on the prior knowledge, two kinds of time delays are considered. One is the Markov delay, and the other one is the arbitrary-bounded delay. By making full use of the most recent delay information, a novel controller with delay-dependent control gains is constructed, and the stability conditions of the closed-loop system with either Markov delays or arbitrary-bounded delays are derived. Cone complementarity linearisation approach is employed to design the stabilising controllers. Finally, simulation and experimental results are given to illustrate the effectiveness of the obtained results.

Network-Based Control under Round-Robin Scheduling and Quantization