Random Network-induced Delays Research Articles

Time-Varying Formation Predictive Control of Second-Order Networked Multi-Agent Systems With Three-Channel Random Communication Constraints

This paper presents a time-varying formation tracking control scheme for second-order networked multi-agent systems with random network-induced delays and packet losses. Three types of communication channels are considered: the feedback and forward channels of each agent as well as the channels between agents. To mitigate the adverse effects of the three-channel communication constraints, a novel distributed predictive control scheme is proposed by combining the networked predictive control approach and the time-delay system approach. Then, the stability condition for the resulting closed-loop time-delay system is derived via the Lyapunov theory, which is independent of the random communication constraints in the forward and feedback channels. Finally, comparative simulation results verify the superiority of the proposed scheme.

Self-adaptive multi-objective differential evolution algorithm with first front elitism for optimizing network usage in networked control systems

In networked control systems, by means of event-triggered transmission, it is possible to reduce the network usage, keeping the control system performance at satisfactory levels. There are several schemes for event-triggered transmission. In this study, we propose a multi-objective optimization problem to tune the event-triggered mechanisms. On solving the proposed problem by means of multi-objective evolutionary optimization, a set of efficient solutions is generated with different tradeoffs between control system performance and the number of transmissions. To solve the proposed problem, we also developed an improved multi-objective differential evolution algorithm that includes a self-adaptive mechanism, dynamic crowding distance operator, and novel elitism of the first front. The proposed method is applied to tune decentralized event-triggered mechanisms for a controller given a priori, considering random network-induced delays and packet loss. Two case studies are present ed, comparing the performance of eight different decentralized event-triggered schemes, analyzing the selection of the sampling period, and demonstrating the efficacy of the proposed tuning method.

Output feedback $H_\infty$ control of networked control systems based on two channel event-triggered mechanisms

In this paper, we study dynamical output feedback {$H_\infty$} control for networked control systems (NCSs) based on two channel event-triggered mechanisms, which are proposed on both sides of the sensor and the controller. The output feedback $H_\infty$ controller is constructed by taking random network-induced delays into consideration without data buffer units. The controlled plant and the output feedback controller are updated immediately by the sampled input and the sampled output, respectively. By using the approaches of time delay and interval decomposition, linear matrix inequality (LMI) based sufficient conditions are presented to guarantee that the closed-loop system satisfies $H_\infty$ performance. Finally, we provide numerical simulations to illustrate effectiveness of the proposed method.

Analysis and synthesis of networked control systems with random network-induced delays and sampling intervals

In this paper, the stability of and controller design for networked control systems (NCSs) with network-induced delays and random sampling intervals are investigated. Specifically, the network-induced delays and sampling intervals are assumed random following a joint probability density function. For stability analysis, the system is modeled in the discrete-time domain. In this context, both the moment stability and Lyapunov stability are considered, for which conditions guaranteeing stability are derived leveraging a vectorization technique. By introducing a new matrix decomposition method, the stabilization controller is designed so that the closed-loop system is stochastically stable in the presence of random sampling intervals and network-induced delays. Finally, a benchmark example is provided to validate the effectiveness of the proposed approach.

Robust controller design for marine electric propulsion system over controller area network

With the consistent tendency of electrification and intelligentization of marine systems in recent years, the electric propulsion system has been a prospective candidate for ships due to its potential in energy saving, environmental protection, high efficiency, and high reliability. However, time-varying delays of communication networks would be induced due to increasing information exchange requirement that caused by the increasing number of devices connecting to the communication networks as well as bandwidth limitation of marine network. Meanwhile, the propeller load is difficult to model due to the complexity of ship dynamics, which increases the uncertainty of marine electric propulsion system. Thus, robust control of the marine electric propulsion system is necessary and challenging. This paper presents a mixed H∞∕LQR robust controller design for marine electric propulsion system to address robust speed tracking problem under possible network-induced delays. The propeller dynamic model is built via open-water experimental data to reflect propeller load characteristics. Then, a delay-free model is established for the marine electric propulsion system by using system augmentation technique, with the random network-induced delay characterized by polytopic inclusions and Taylor series expansion. A mixed H∞∕LQR robust controller design is proposed for the marine electric propulsion system. Finally, based on a detailed controller area network model, the performance and effectiveness of the mixed H∞∕LQR robust controller are demonstrated by comparative simulation tests of a marine electric propulsion system with 4.088 MW permanent magnet synchronous motor (PMSM).

Observer-Based Incremental Predictive Control of Networked Multi-Agent Systems With Random Delays and Packet Dropouts

This brief addresses the cooperative output tracking control problem for a linear heterogeneous networked multi-agent system with random network-induced delays and packet dropouts in the feedback channel of each agent, which consists of one leader agent and multiple following agents. To compensate for adverse effects of those random communication constraints, an incremental networked predictive control scheme based on state observers is proposed. A necessary and sufficient condition is derived for the stability of the resulting closed-loop system, which is independent of random communication constraints. Experimental results on a networked multi-motor control test rig show the effectiveness and applicability of the proposed scheme, including a feature that zero steady-state output tracking errors can be achieved even for the case with plant-model mismatch.

The Research of Network-induced Delay Measurement Methods in Wireless Networked Control Systems based on Zigbee Network

The large and random network-induced delay in ZigBee wireless network seriously reduce the performance of wireless networked control systems (WiNCS) based on ZigBee network, due to unreliable communication, limited bandwidth, as well as high bit error rate of ZigBee network. Compared with other methods, such as converting time-varying network-induced delay into a fixed value, assuming network-induced delay under a certain statistical law, real-time measurement and compensation of random network-induced delay can effectively improve the performance of WiNCS. In order to obtain the network-induced delay of WiNCS based on ZigBee network on-line, this paper deeply analyzes the composition of delay, provides three delay measurement methods, clock synchronization method, confirm mechanism method and online estimation method, and designs a WiNCS network data transmission experimental platform. Then measurement precision of this measurement methods are analyzed by experiments that based on the experimental platform. The experiments show that, these measurement methods achieve very high measurement precision by taking compensation measures.

Fuzzy PID Controller Design for Uncertain Networked Control Systems Based on T–S Fuzzy Model with Random Delays

In this paper, the stochastic stabilization problem of uncertain networked control systems involving Takagi–Sugeno (T–S) fuzzy model, transmission delays and external disturbances is investigated, where the random network-induced delays are modeled as Markov chains. Firstly, by combining T–S fuzzy model with fuzzy PID controller, the uncertain networked control systems with random communication delays and external disturbances are modeled. Then, the uncertain networked control system is simplified through a mathematical method, and the stabilizing controller is derived for the uncertain networked control systems by using Lyapunov functional and linear matrix inequality. Finally, simulation results are presented to verify the effectiveness and availability of the developed results.

Input Design-Based Compensation Control for Networked Nonlinear Systems With Random Delays and Packet Dropouts

This brief investigates the data-based networked control problem of a class of nonlinear systems, where random network-induced delays and packet dropouts in the feedback and forward channels are considered simultaneously and further treated as random round-trip time (RTT) delays. The main contributions of this brief are as follows: 1) To actively compensate for RTT delays, a novel compensation control scheme is proposed based on the control input design, and thus, only one control command needs to be transmitted to the actuator through the network; 2) an explicit sufficient condition is derived to ensure the stability of the resulting closed-loop system as well as a zero steady-state output error for a constant reference input; and 3) numerical simulation and comparison with existing methods are carried out to show the effectiveness of the proposed method.

Design and performance analysis of networked predictive control systems based on input-output difference equation model

This paper is concerned with the design and performance analysis of networked control systems, where random network-induced delay, packet disorder, and packet dropout in the feedback and forward channels are considered simultaneously and further treated as the round-trip time (RTT) delay. To actively compensate for the RTT delay, a networked predictive control scheme is designed based on the input-output difference equation model. For time-varying reference signals, the resulting closed-loop system can achieve the same output tracking performance and closed-loop stability as the corresponding local control system. Specifically, for the step reference input, it can provide a zero steady-state output tracking error. The controller design problem is solved by using the augmented state-space model as well as the static output feedback strategy. In addition, the stability of the closed-loop system is also discussed for the plant subject to bounded disturbances and modelling errors. Finally, simulation and experimental results are given to demonstrate the effectiveness of the proposed method.

Mixed H 2/H ∞ control for a class of nonlinear networked control systems

In this paper, the mixed H 2/H ∞ control problem is investigated for a class of nonlinear discrete-time networked control systems with random network-induced delays, stochastic packet dropouts and probabilistic sensor faults. The packet dropouts process is modeled as a homogeneous Markov chains taking values in a finite state space. Network-induced delays occur in a random way with known upper bound. A set of stochastic variables are exploited to describe sensor faults with different probabilistic density functions. By using a delay-dependent Lyapunov functional, a mode-dependent mixed H 2/H ∞ controller is designed to guarantee both stochastic stability of the closed-loop system and the prescribed H2, H¥ control performances. Sufficient conditions for the existence of the mixed H 2/H ∞ controller are presented in terms of a series of LMIs. If these LMIs are feasible, then the modedependent mixed H 2/H ∞ controller can be obtained. A numerical example is given to demonstrate the effectiveness of the developed method.

A Combined Fault Tolerant and Predictive Control for Network-Based Industrial Processes

This paper investigates the tracking and optimization problems for a class of industrial processes by utilizing output feedback fault-tolerant control (FTC) and predictive compensation strategy. At device layer, the tracking problem for device layer subsystems which subject to random failures and random network-induced delays is investigated. These two different random processes are modeled as Markovian chains. Device layer controllers are designed to guarantee the tracking performance at $H_{\infty}$ disturbance attenuation level. At operation layer, a nonlinear model predictive control (NMPC) strategy is proposed to stabilize the upper operation layer system. Then by considering the effect of radial basis function (RBF) performance index and random packet dropout phenomena, a predictive compensator is designed to guarantee the input-to-state practical stability (ISpS) of the resulting system. In addition, networked flotation processes are considered in the simulation part, and the simulation results further demonstrate the effectiveness of the proposed method.

Robust Lateral Motion Control of Electric Ground Vehicles With Random Network-Induced Delays

This paper presents a lateral motion control strategy for four-wheel independently actuated (FWIA) electric ground vehicles that use the controller area network as a communication medium. The proposed controller design aims to guarantee vehicle stability while tracking the desired yaw rate, in spite of random network-induced delays that exist in both the feedback and forward channels. By modeling the random network-induced delays in both channels as two homogenous Markov chains, statistic information of these delays is incorporated in the mode-dependent tracking controller design. The control law consists of state feedback control and integral control. To fully compensate for the network-induced delays, a delay-free stochastic closed-loop system is first obtained in a discrete-time framework by using a system augmentation technique. Then, a robust linear quadratic regulator-based $\boldsymbol{H}_{\infty}$ controller is developed to achieve the tradeoff between the tracking error and the control input while also attenuating the effect of external disturbance. Considering the physical limitation of in-wheel motors, the eigenvalue positions of the state matrix are constrained in a predefined area to further balance the control inputs and transient responses by using pole placement. Finally, an iterative linear matrix inequality algorithm is adopted to obtain the delay-dependent feedback control gains. Simulation results based on a high-fidelity, CarSim, full-vehicle model show the effectiveness of the proposed lateral motion control approach.

Multiple event-triggered H2/H∞ filtering for hybrid wired–wireless networked systems with random network-induced delays

Unlike the widely existing H2/H∞ filtering methods under single (i.e., wired or wireless) network with single channel environment, there exist multiple event-generators and different network-induced delays in hybrid wired–wireless networks, which make H2/H∞ filtering analysis and design more complex. The main objective of this paper is to investigate multiple event-triggered H2/H∞ filtering for hybrid wired–wireless networked systems with random network-induced delays. For multi-sensor network communications, a multiple event-triggered mechanism is employed firstly, which can reduce communication burden of each channel. The different communication characters of hybrid wired–wireless networks are then described by two Markov chains, and a general filtering error dynamic system model with the event-triggered parameters and multi-channel network-induced delays of hybrid wired–wireless networks is presented. Furthermore, the designed filter enables the filtering error dynamic system to be stochastic stability and to achieve a prescribed performance, and the relationships between the stability criteria and the maximum network-induced delays of hybrid wired–wireless networks, the event-triggered parameters and the system performance parameter are established. Finally, simulation results confirm the effectiveness of the proposed method.

D-Stability Constraint for Discrete-time Networked Control Systems

The problem of modeling and D-stability analysis for discrete-time control systems in networked environments is researched. Firstly, a new modeling approach is proposed to describe the network behaviors into a unified framework such as random network-induced delays, packet dropout, and packet disorder etc. And the overall mathematic model of discrete-time networked control systems is derived with state feedback control strategy. Then with this model, the D-asymptotic stability condition, which is dependent on the upper bound of the equivalent network-induced delays, is presented in terms of spectra method. These can guarantee the performance in the presence of communication constraints. Finally, a simulation example is given to demonstrate the effectiveness and efficiency of the proposed theoretical results. Keywords: Discrete-time networked control systems, D-Stability, networked-induced delay, spectra analysis.

MixedH2/H∞control for a class of nonlinear discrete-time networked control systems with random delays and stochastic packet dropouts

The paper studies the problem of mixed H2/H∞ control for a class of nonlinear discrete-time networked control systems. By using the indicator function method, random network-induced delays and stochastic packet dropouts are taken into account in a unified framework in the designed mixed H2/H∞ controller. In the presences of random transmission delays, stochastic packet dropouts and all admissible disturbances, the resulting closed-loop system is stochastically stable in mean square and attains the prescribed H2 and H∞ performances. The designed mixed H2/H∞ controller can be obtained by solving a set of feasible linear matrix inequalities. Finally, a numerical example is provided to show the usefulness and effectiveness of the developed method. Copyright © 2014 John Wiley & Sons, Ltd.

Fault detection for a class of nonlinear networked control systems with Markov sensors assignment and random transmission delays

The paper investigates the fault detection problem for a class of nonlinear networked control systems with both communication constraints and random transmission delays. The access status of the sensors is governed by a stochastic event, which is modeled as a Markov chain taking matrix values in a certain set. The main task of this paper is to design a mode-dependent fault detection filter, such that for Markov sensors assignment, random network-induced delays and the unknown input signal, the error between the fault and the residual signal is minimized. And the resulting fault detection dynamics is formulated as an H∞ filtering problem of a Markov jump system. The linear matrix inequality-based sufficient conditions for the existence of the fault detection filter are obtained. Finally, two examples are given to show the effectiveness of the developed method.

Design of Networked Control System with Time-Delay and Packet Loss

For Networked Control System (NCS) with random network-induced delay and packet loss, an observer is designed to reconstruct the states using output values. A piece-wise time-delay strategy and the timestamp technique are used, improving the system performance. Depending on whether data dropout occurs or not, system is modeled as an Asynchronous Dynamical System (ADS), and theorem guaranteeing the system closed-loop stability is also given. Based on Lyapunov and Linear Matrix Inequality (LMI), controller gain and observer gain are solved and TrueTime toolbox is used to verify the effectiveness of the algorithm.

Adaptive Fuzzy Control for Multilateral Cooperative Teleoperation of Multiple Robotic Manipulators Under Random Network-Induced Delays

In this paper, an adaptive fuzzy control is investigated for multilateral teleoperation of two cooperating robotic manipulators that manipulate an object with constrained trajectory/force in the presence of dynamics uncertainties and random network-induced delays. First, the interconnected dynamics that consist of two master robots and cooperating slave robots are formulated. To consider multiple stochastic delays in communication channels, Markov processes are used to model these random network-induced delays. The interconnected dynamics of the teleoperation are divided into a local master/slave position/force subsystem and a stochastic-delayed motion synchronization subsystem. Then, an adaptive fuzzy control strategy, which is based on linear matrix inequalities (LMIs) that combine adaptive update techniques, is proposed to suppress the dynamics uncertainties, the external disturbances, and the multiple stochastic delays in communication channels. The control approach ensures that the defined synchronization errors converge to zero. The stochastic stability in mean square of the closed-loop system is proved using LMIs based on Lyapunov-Krasovskii functional synthesis. The proposed controls are validated using extensive simulation studies.

Sampled-Data Consensus for Nonlinear Multiagent Dynamical Systems via Reliable Control

The paper studies sampled-data consensus for nonlinear multiagent dynamical systems. A distributed linear reliable consensus protocol is designed, where probabilistic actuators with different failure rates and random network-induced delay are considered. Based on the input delay approach, a new distribution-based fault multiagent system model with random delay is proposed. By using the stochastic analysis technique and Kronecker product properties, some consensus conditions are derived in terms of linear matrix inequalities, and the solvability of derived conditions depends on not only the failure rate of the actuator but also on the probability of the delay. Finally, a numerical example is provided to demonstrate the effectiveness of the obtained theoretical results.