Medium Access Constraint Research Articles

Finite-Frequency Fault Detection Filter Design for Networked Nonlinear Systems With Medium Access Constraints

Finite-Frequency Fault Detection Filter Design for Networked Nonlinear Systems With Medium Access Constraints

Eavesdropping Strategies for Remote State Estimation Under Communication Constraints

This paper studies the confidentiality issue of wireless sensor networks under communication constraints from the perspective of an eavesdropper. The considered communication constraints include both medium access constraint and bandwidth limitation. Specifically, the former results in only one sink node gaining access to the shared network at each time step, while the latter requires data to be quantized by a probabilistic quantizer before being transmitted. The task of the eavesdropper is to develop eavesdropping strategies for the constrained network to infer the state of the system as accurately as possible. Since the data is generally unreadable to unauthorized third parties in terms of secure transmission, an eavesdropper with limited power must decide which sink nodes’ data needs to be decrypted. By analyzing the impact of different decryption strategies on the eavesdropping performance, a deciphering scheduling is proposed, which minimizes the expected estimation error without exceeding the energy budget. Besides, a recursive reset algorithm is put forward based on the properties of the probabilistic quantizer, which reflects that an eavesdropper can infer whether its own estimate is accurate enough from the decoded data. Moreover, a sufficient condition is established in which the eavesdropping performance is improved under the proposed algorithm. A numerical example is provided to demonstrate the validity of the developed approaches.

Reliable state estimation for neural networks with TOD protocol and mixed compensation

This paper considers the reliable state estimation issue for discrete-time neural networks with the try-once-discard (TOD) scheduling protocol and mixed compensation strategy. For the phenomenon of medium access constraint, the measurement transmitted from sensors to the estimator is subjected to the TOD scheduling protocol. The mixed compensation is proposed to flexibly compensate those missing measurements caused by the TOD protocol. By using a novel polytopic uncertain model, a reliable state estimator is designed, where the gain matrix is determined by two vertex matrices. Then sufficient conditions are established, which ensure the error system meets the stochastic stability and the l2-l∞ performance. Finally, an illustrative example shows the validity of the proposed reliable state estimator.

Robust predictive Control for Networked Control Systems with Access Constraints

Based on the rolling horizon optimization strategy, the networked robust predictive control with medium access constraints and packet loss is studied. Firstly, considering the influence of network factors such as medium access constraints and packet loss, Markov jump rule and Bernoulli independent and identically distributed process are used to transform the network problem into the robust problem of networked control system. According to the established Markov jump system model and stability analysis, a robust predictive controller for networked control systems is designed by using linear matrix inequality (LMI) method, which makes the system asymptotically stable. Finally, a numerical example is given to verify the effectiveness of the proposed control method.Networked control system; medium access constraints; packet loss; robust predictive controller.

Compensated methods for networked control system with packet drops based on compressed sensing

Due to unreliable and bandwidth-limited characteristics of communication link in networked control systems, the real-time compensated methods for single-output systems and multioutput systems are proposed in this paper based on the compressed sensing (CS) theory and sliding window technique, by which the estimates of dropping data packets in the feedback channel are obtained and the performance degradation induced by packet drops is reduced. Specifically, in order to reduce the cumulative error caused by the algorithm, the compensated estimates for single-output systems are corrected via the regularization term; considering the process of single-packet transmission, a new sequential CS framework of sensor data streams is introduced to effectively compensate the dropping packet on single-channel of multi-output systems; in presence of the medium access constraints on multi-channel, the communication sequence for scheduling is coupled to the algorithm and the estimates of the multiple sensors for multi-output systems are obtained via the regularization term. Simulation results illustrate that the proposed methods perform well and receive satisfactory performance.

Generalized Model Reference Scheduling and Control Co-Design with Guaranteed Performance

In this paper, a generalized model-reference scheduling (GMRS) scheme is proposed for a networked control system (NCS) with guaranteed performance control and medium access constraint (MAC). The GMRS presented reduces conservatism to some extent, and its performance is improved by adjusting the weighted gain. In addition, two cases of uncertainty existing in the system matrix and control matrix are considered. For the first case, a co-design of guaranteed performance control and the GMRS is studied for the NCS with and without zero-order hold mechanism. For the second case, the uncertainty induced from time delay is considered in the guaranteed performance control and the GMRS co-design. Finally, illustrative examples are given to demonstrate the effectiveness of the proposed co-design schemes.

Dynamic Output Feedback Control of Networked Systems With Medium Access Constraints

This paper is concerned with the dynamic output feedback control issue for a class of networked control systems with medium access constraints, network-induced delays and packet dropouts. It is assumed that the medium access constraints at both sides of the controller obey the Markov distribution, the upper bound of the network-induced delays is less than one sampling period, and the packet dropouts of networked channels can be described by i.i.d Bernoulli distribution processes. Then, the networked control systems are modelled as a class of asynchronous dynamic systems. According to Lyapunov stability theory and switching system theory, the dynamic output feedback controller is designed to guarantee the exponential stability of networked systems with the given decay rate. Finally, an illustrative example is provided to demonstrate the effectiveness of the proposed method.

Neural network-based fault detection for nonlinear networked systems with uncertain medium access constraint: Application to motor systems

The fault detection for a class of continuous-time nonlinear networked control systems with medium access constraint is concerned in this paper, where the occurring probability of transition from one sensor to another is allowed to be partially unknown and uncertain. First of all, a Markovian system approach is adopted to describe the access process of sensors, in which only one sensor is allowed to access the communication channel. A robust filter based residual generator is proposed to generate the residual signal such that it can be used to indicate whether the fault has occurred or not. The nonlinear term is approximated by a neural network, and the Lyapunov–Krasovskii functional is introduced to analyze the fault detection system, three sufficient conditions for the stochastic stability of fault detection error system are given, and the fault detection filter gains are calculated via solving some matrix inequalities. In the simulation, a second-order DC motor system is used to validate of the main results, which shows the effectiveness of the fault detector design.

Model-dependent Scheduling and H-infinity Control Co-design for Networked Control Systems

In this paper, a novel model-dependent scheduling scheme is proposed for the networked control systems with time-delay, disturbance, and medium access constraints. The scheduler calculates the error between the ideal dynamic and the real system, and selects the states that make the stability of the system better to access the network. In addition, two kinds of representative time-delays in the networked control systems, constant time-delay and random time-delay, are considered. A robust H-infinity and switched-system-based co-design strategy is introduced to deal with the disturbance in the system, and the system uncertainty introduced by the random time-delay as well. Finally, illustrative examples are given to demonstrate the effectivity of the proposed scheduling method and the co-design scheme.

H∞ Control with Multiple Packets Compensation Scheme for T-S Fuzzy Systems Subject to Cyber Attacks

This paper is concerned with the H∞ controller design problem for a class of network-based nonlinear systems (NCSs) represented by the Takagi-Sugeno (T-S) fuzzy model. A multiple packets compensation scheme is developed which uses all the data stored in a finite memory buffer to compensate the negative effects of packet dropouts. This model contains the medium access constraint problem as a special case. The time-multiplexing mechanism may be used for such a case so that there are multiple packets arrive at the receiver side. By taking the stochastic cyber attacks into account, the desired controller in terms of linear matrix inequalities (LMIs) is designed by using fuzzy-rule-dependent Lyapunov method. The sufficient condition is obtained which makes the closed-loop system be asymptotically mean-square stable and achieve the prescribed H∞ disturbance-rejection-attenuation level. Finally, a mass-spring-damping system is given to show the effectiveness of the algorithm.

Dynamic Network Access Scheduling and Stabilization of TPCS Networked Control System

The Networked Control Systems (NCS) is a significant arena in the current complex technical scenario. NCS provides the user a wide range of scope in mitigation of its underlying issues in order to benefit the versatility of the network. Two Inverted Pendulums Coupled by a Spring (TPCS) system is one of the finest platforms to study NCS and its issues. The objective considered here is to stabilize both the pendulums at desired vertical position while the “Medium Access Constraint” of NCS is addressed. The proposed Dynamic Medium Access Scheduling strategy aims at analyzing the issue so that it can be applied in practical scenarios. In this paper (i) TPCS is modelled as a switched system (ii) Dynamic Medium Access Scheduling protocols are discussed, selected and applied to TPCS and (iii) the best of the two: Weighted Fastest Decay and Guaranteed Dwell-Time methods to give a design solution is summarized. This is aided with computer simulations and the results show that the scheduling polices are effective in controlling TPCS-NCS.

Control of a group of systems whose communication channels are assigned by a semi-Markov process

ABSTRACTThis technical note is concerned with the problem of medium access constraint for a group of networked systems. The scheduling of each subsystem is defined by a stochastic protocol, which can be modelled by a semi-Makov chain with a time-varying transition probability matrix. The resulting closed-loop nonlinear systems are a semi-Markovian jump system with delay. Sufficient conditions for exponential mean-square stability of the resulting closed-loop systems are derived via a Lyapunov–Krasovskii method. Based on the stability criterion, the controller gain of each subsystem is designed. A simulation example is used to demonstrate the effectiveness of proposed method.

Control of NCSs with energy efficient channel assignment and power allocation

Abstract This paper investigates the simultaneous stabilization of a collection of battery-powered networked control systems (NCSs) with medium access constraint and communication energy limitation. Each time the channels can only accommodate a limited number of systems for communication and the successful packet arrival rate at the controller depends on the power used by the sensor. Then in order to satisfy the medium access constraint, reduce the communication energy cost and stabilize the collection of NCSs, one needs to decide when to schedule which plant to communicate by which channel and by which power level. Based on the average dwell time technique, sufficient conditions for the exponential mean square stability of a single plant are given at first. Then, based on the stability conditions, a period scheduling policy is proposed to assign the channel accessing sequence and power level such that all the plants are simultaneously stabilized. Finally, a new framework for channel assignment, power allocation and controller design is constructed, which can guarantee a desired decay rate for each system and a minimal energy consumption for the group of systems. The effectiveness of the methodology is demonstrated with numerical simulations.

A Dwell Time Switching Approach to Channel Assignment for Stabilization of NCSs With Medium Access Constraint

A Dwell Time Switching Approach to Channel Assignment for Stabilization of NCSs With Medium Access Constraint

Minimum Data Rate for Exponential Stability of Networked Control Systems with Medium Access Constraints

In this paper, we investigate the minimum data rate problem to guarantee the stability of the networked control systems (NCSs) suffered to the medium access constraints in the digital communication channel. Under the effect of medium access constraints, the data rate of each communication node switches between its pre-set value and zero according to the medium access status assigned by the scheduler. In order to guarantee the exponential stability, a new analysis approach combined with the average dwell time technique and entropy theory is established for the unstable scalar systems and vector systems to obtain the sufficient and necessary conditions for each subsystem. The obtained minimum data rate are related to the intrinsic entropy rate of the system and the duty factor allocated by the scheduler. An numerical example is given to illustrate the effectiveness of the designed minimum data rate for the NCSs which composed by a collection of subsystems.

Event‐triggered fault‐tolerant control and scheduling codesign for nonlinear networked control systems with medium‐access constraint and packet disordering

SummaryThis paper studies an event‐triggered communication, scheduling, and fault‐tolerant control codesign method for nonlinear networked control systems with medium‐access constraint, delay, and packet disordering using an adaptive approximation method and adaptive technique. By considering nonlinear dynamics and controller reconfiguration, a novel event‐triggering scheme with an adjustable triggering condition and adaptive triggering thresholds is proposed. The stochastic event‐driven actuator scheduling is investigated without the assumption that the controller can access the current modes of the actuators. By considering the Markovian delay and focusing on the transmitter node, a new packet reordering approach is used to cope with packet disordering. This paper proposes an active fault‐tolerant control method, in which the nominal controller is redesigned for the postfault plant by using the fault information provided by an estimator. It is proven that the estimation error of the estimator is uniformly bounded, the reconfigurable controller and event‐trigger ensure the boundedness in probability of the state tracking error before and after the fault occurrence in the presence of medium‐access constraint, delay, and packet disordering while reducing communication load. The effectiveness of the proposed method is demonstrated in the numerical example.

Robust Fuzzy-Model-Based Filtering for Nonlinear Cyber-Physical Systems With Multiple Stochastic Incomplete Measurements

This paper is concerned with the state estimation problem for a class of nonlinear cyber-physical systems (CPSs) where the nonlinear dynamical physical process is approximated by a Takagi–Sugeno fuzzy model. The physical plant is measured by a set of wireless sensors and the sensors communicate with the remote estimator via a communication channel. In the considered CPS, the randomly occurring sensor saturation, signal quantization, packet dropouts as well as the medium access constraint are studied in a unified framework. We develop a sufficient condition such that the filtering error system is asymptotically stable in the mean-square sense and also with a prescribed $\boldsymbol {H_\infty }$ performance level. The filter gain parameters are determined by solving a convex optimization problem. Finally, the simulation study on the networked truck-trailer system is presented to show the effectiveness of the proposed estimator design.

Analysis and synthesis of networked control systems: A survey of recent advances and challenges

A networked control system (NCS) is a control system which involves a communication network. In NCSs, the continuous-time measurement is usually sampled and quantized before transmission. Then, the measurement is transmitted to the remote controller via the communication channel, during which the signal may be delayed, lost or even sometimes not allowed for transmission due to the communication or energy constraints. In recent years, the modeling, analysis and synthesis of networked control systems (NCSs) have received great attention, which leads to a large number of publications. This paper attempts to present an overview of recent advances and unify them in a framework of network-induced issues such as signal sampling, data quantization, communication delay, packet dropouts, medium access constraints, channel fading and power constraint, and present respective solution approaches to each of these issues. We draw some conclusions and highlight future research directions in end.

Transmission power allocation of NCSs with Markov channel assignment

This paper investigates networked control systems (NCSs) where the sensors communicate with the remote controller via a wireless fading channel. Each time the channel can accommodate just one sensor for communication and the access to the channel of the sensors is driven by a random event. When a sensor is triggered to send its measurement, it can choose to use a high power or a low power to save energy. The power level of the sensor determines the probability of successful packet reception at the controller. This paper aims to find an appropriate transmission power allocation method for the sensors jointly with a system controller so that the NCS is stabilized with a given energy budget. By introducing a Markov chain model for the medium-access constraint and modeling the packet dropout as a Bernoulli process, we derive a new model and stability conditions for the NCSs, which are given in terms of the transition probabilities of the Markov chain and different packet reception rates. An interesting power scheduling policy is obtained and two kinds of controller design schemes are given depending on whether the medium-access status of the sensors is acknowledged to the controller or not. The results are then extended to the case of large-scale systems and an optimal co-design methodology which can stabilize the whole set of systems with largest stability margin is proposed. The effectiveness of the presented method is demonstrated by numerical simulations.

Optimal [formula omitted] filtering for periodic linear stochastic systems with multiplicative white noise perturbations and sampled measurements

This paper addresses the problem of optimal H2 filtering for a class of continuous-time periodic stochastic systems with periodic sampled measurements. The class of admissible filters consist of deterministic continuous-time periodic systems with finite jumps. The optimal solution of the considered optimization problem is obtained by integrating a suitable generalized continuous-time Riccati equation with finite jumps. To illustrate the proposed filtering strategy, we consider a problem of field monitoring where sensors are distributed on a rectangular region in order to estimate the state of a diffusion process. We consider that the sensors and the filter communicate over a communication channel and we assume that the communication channel induces some communication constraints. More specifically, we consider a medium access constraint under which the shared network can only accommodate a limited number of simultaneous communications between components.