Time-varying Communication Delays Research Articles

A Nonlinear Control Design for Cooperative Adaptive Cruise Control with Time-Varying Communication Delay

Cooperative adaptive cruise control (CACC) is one of the main features of connected and autonomous vehicles (CAVs), which uses connectivity to improve the efficiency of adaptive cruise control (ACC). The addition of reliable communication systems to ACC reduces fuel consumption, maximizes road capacity, and ensures traffic safety. However, the performance, stability, and safety of CACC could be affected by the transmission of outdated data caused by communication delays. This paper proposes a Lyapunov-based nonlinear controller to mitigate the impact of time-varying delays in the communication channel of CACC. This paper uses Lyapunov–Krasovskii functionals in the stability analysis to ensure semi-global uniformly ultimately bounded tracking. The efficaciousness of the proposed CACC algorithm is demonstrated in simulation and through experimental implementation.

Distributed Consensus and Formation Control of Multi-AUV Systems under Actuator Faults and Switching Topology

This note presents the distributed consensus and formation control for a group of AUVs, comprising one leader and three followers arranged in a diamond formation. The study addresses significant control challenges, including external disturbances, noise, model uncertainties, actuator faults, stochastic switching topologies, time-varying communication delays, and positional information between agents. Stochastic switching topologies are assumed to follow a Markov chain. To effectively address these challenges and ensuring satisfactory performance levels, two control architectures have been formulated to facilitate the imposition of desired trajectories upon the system states. The initial architecture amalgamates sliding mode control methodology with adaptive algorithms, designed explicitly for tracking missions in the presence of fully functional actuators. In response to potential actuator failures, the second control architecture integrates passive fault-tolerant techniques, significantly enhancing system reliability under such circumstances as well as switching topology. The proposed framework demonstrates its effectiveness in managing the high nonlinearity and coupled dynamics of AUVs. Simulation results validate the efficacy of the developed strategy. It successfully establishes a desired consensus and formation among agents, reduces chattering phenomena, accurately tracks reference trajectories, handles disturbances and uncertainties within an unknown domain, and achieves finite-time convergence.

Distributed Voltage Control for Microgrids Against Time-Varying Communication Delay Interference

Distributed Voltage Control for Microgrids Against Time-Varying Communication Delay Interference

Communication topology for AUV formation consensus based on optimal cost control under time-varying communication and input delays

This study investigates the optimal communication topology for consensus in autonomous underwater vehicle (AUV) formations, considering both leader-following and leaderless scenarios. Initially, a second-order dynamic model of the AUV is established using the feedback linearization method. To address time-varying delays, a universal predictor-based consensus protocol is introduced, capable of operation with or without a designated leader. Subsequently, two global quadratic cost functions are formulated based on distinct consensus errors. Utilizing linear quadratic regulator (LQR) theory and matrix theory, the optimal communication topologies and associated gain matrices are deduced. Specifically, for leader-following AUV formations, the optimal communication topology is identified as an unevenly weighted star-shaped directed spanning tree. Conversely, for leaderless formations, the optimal topology adopts a complete digraph, which indicates high interaction requirements. To accommodate practical constraints, a suboptimal topology is devised, featuring a directed spanning tree. These findings offer a theoretical framework for selecting communication topologies in AUV formations, with numerical examples provided to validate the proposed approaches.

Robust H∞ control of heterogeneous connected vehicles platoon with random time-varying communication delay

As an essential component of intelligent transportation systems (ITS), connected cruise control (CCC) has attracted much attention due to its potential to improve vehicle safety and reduce traffic congestion. However, besides the disturbance acting on the head vehicle of the platoon, the time-varying communication delay in vehicle-to-vehicle (V2V) also seriously impacts the CCC system’s stability. In this paper, we investigate a robust control scheme utilizing the Lyapunov-Krasovskii functional stability theory and [Formula: see text] technique to ensure the stability of the CCC system consisting of the connected and automated vehicle (CAV) and connected human-driven vehicles (CHVs) under random time-varying communication delay. The effectiveness and advantage of the designed robust controller are verified by MATLAB/Simulink simulation and comparison with the existing result of the literature.

Containment control for second-order multi-agent systems with time-varying delays via variable-augmented-based free-weighting matrices

This paper investigates the containment control problem for multi-agent systems (MASs), where the time-varying communication delays are considered. The aim of this paper is to introduce new methods for the containment control research of MASs with time-varying delays. To obtain better results on maximum admissible upper bounds (MAUBs) of the delays to ensure the containment control, the variable-augmented-based free-weighting matrices (VABFWMs) method is introduced to avoid the higher-order terms of time-varying delays in estimating the derivative of the Lyapunov-Krasovskii functionals (LKFs). So our method no longer requires the quadratic function negative-determination lemma. In addition, by utilizing the proposed method, we design a containment controller to ensure that all followers are included into the convex hull formed by leaders. Finally, a numerical example is presented to illustrate the feasibility and superiority of our method.

Development of a novel model matching decentralized controller design algorithm and its experimental validation through load frequency controller implementation in restructured power system using TMS320F28379D controlCARD

A three-stage decentralized controller design algorithm is developed to achieve setpoint tracking and disturbance rejection in MIMO systems with communication time delay, and nonlinearities such as saturation and dead band. The first stage involves reference model formulation. The second stage comprises equating approximate generalized time moments/approximate generalized Markov parameters of closed-loop system model with reference model at certain expansion points in s-plane to obtain synthesis-like equation, concerning products of unknown controller numerator and denominator polynomials. This process yields simultaneous linear equations, whose solution provides the coefficients of the product polynomials. In the third stage, the controller parameters are extracted from the product polynomials using exact model matching. The proposed method is illustrated by designing load frequency controller in traditional and restructured power systems under scenarios like system parameter uncertainties, random load variation, and time-varying communication delays. Simulation studies reveal the efficacy of the proposed technique over existing techniques. Furthermore, the practical implementation feasibility of the decentralized controller designed for the restructured power system is validated using the TMS320F28379D controlCARD.

Nonfragile robust [formula omitted] containment control for multi-agent systems with a time-varying delay

Under a fixed directed graph, this paper is concerned with the distributed nonfragile robust H∞ containment control of linear multi-agent systems with model uncertainty subject to admissible external disturbances in the presence of communication delay. Compared with the situation where the controller only considers either nonfragility or time delay, a class of controller considering both nonfragility and time-varying communication delay is put forth while guaranteeing a prescribed H∞ performance level, under which all of the followers’ states merge into the convex hull created by those of the leaders. Specially, the nonfragile term is constructed to eliminate the inaccuracy and perturbation in the designing of the controller gain, where the additional tuning of parameters in the real control systems always occurs. Then, a four-term Lyapunov–Krasovskii functional is employed and analyzed, and a feasible methodology is designed to properly select the controller and observer gains depending on matrix transformation and solving linear matrix inequality. Finally, two simulation examples are used to demonstrate the viability of the proposed techniques.

Distributed Secondary Control for DC Microgrids With Time-Varying Communication Delays: A Networked Predictive Control Scheme

Distributed Secondary Control for DC Microgrids With Time-Varying Communication Delays: A Networked Predictive Control Scheme

Energy shaping-based consensus control in networked underactuated Euler–Lagrange systems with communication and input delays

This paper aims to solve the problems of energy shaping-based consensus control in networked underactuated Euler–Lagrange systems (NUELSs) in the presence of communication and input delays. By appropriately introducing the auxiliary sliding mode variable describing local communication interaction among agents and the corresponding adaptive velocity observer in energy-shaping framework, two decentralized time-varying consensus tracking schemes are proposed for NUELSs. The developed schemes systematically integrate the energy of three parts: the system model energy of actuated and underactuated components, the energy of the controller dynamics and the energy of the adaptive update law, as the total energy. Then this total energy formulates the resultant Lyapunov function that can fully guarantee the distributed time-varying consensus tracking of NUELSs having time-varying communication and input delays. Furthermore, simulation examples of multiple flexible-joint manipulator systems characterized by NUELSs demonstrate the potential advantages of the proposed consensus schemes in stability, adaptability, and robustness. The effects of communication and input delays on cooperative tracking performance are also numerically investigated for NUELSs.

Adaptive inter-area power oscillation damping from offshore wind farm and MMC-HVDC using deep reinforcement learning

The coordination of the offshore wind farm (OWF) and high-voltage direct current (HVDC) links to provide ancillary power oscillation damping (POD) services may become a mandatory requirement from the transmission system operators in the near future. However, the performances of the POD controllers (PODCs) are vulnerable to the power system uncertainties and random communication delays of the wide-area signals. To address these issues, this paper proposes the design of the coordinated PODCs by using the deep reinforcement learning (DRL) method. The DRL-based PODCs employ one of the state-of-the-art DRL algorithms, proximal policy optimization, which can learn to adapt to the system uncertainties and time-varying communication delays by interacting with the power system continuously. A detailed simulation model of an OWF connected to the IEEE-39 bus AC grid via the modular multilevel converter based HVDC link has been built as a simulation platform, and the efficacy of the proposed DRL-based PODCs has been validated across a broad spectrum of operating conditions, disturbances, and communication latency.

Neural network-based robust consensus tracking for uncertain networked Euler-Lagrange systems with time-varying delays and output constraints

This paper mainly focuses on the cooperative robust consensus tracking problem of uncertain networked Euler-Lagrange systems (NELSs) with time-varying delays and output constraints. By systematically integrating the neural network (NN) adaptive technique and the logarithmic type Barrier Lyapunov Function (BLF) in combination with the additional robust control law, two distributed robust consensus schemes for uncertain NELSs are proposed for two cases of time-varying communication and input delays respectively, which can fully guarantee to constrain the output consensus error within a safety region simultaneously. Furthermore, numerical simulation examples are provided to demonstrate the comparable potential advantages of the proposed robust control law over some existing algorithms, including adaptability, stability, and robustness, as well as delay effects.

Observer-Based Event-Triggered Consensus Control of Multi-Agent Systems With Time-Varying Communication Delays

Observer-Based Event-Triggered Consensus Control of Multi-Agent Systems With Time-Varying Communication Delays

Global Consensus-Based Formation Control of Nonholonomic Mobile Robots With Time-Varying Delays and Without Velocity Measurements

We propose a solution to the full consensus-based formation problem for torque-controlled nonholonomic mobile robots under time-varying communication delays and without velocity measurements. Under the assumptions of static and undirected communication topologies, and smooth and bounded delays, we propose a distributed smooth, time-varying control law which achieves the goal of acquiring a global formation pattern in a common consensus point for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">both</i> position and orientation. The controller is a combination of a simple Proportional-Plus-Damping scheme and a simple globally exponentially convergent velocity observer. Consensus is reached independently of all initial conditions. Realistic simulations in the Gazebo-ROS environment illustrate the effectiveness of the proposed algorithm and the robustness with respect to measurement noise, non-smooth delays and uncertain dynamics.

Coverage control for mobile sensor networks with unknown terrain roughness and nonuniform time-varying communication delays

Coverage control for mobile sensor networks with unknown terrain roughness and nonuniform time-varying communication delays

Three-Dimensional Cooperative Guidance Law Against Maneuvering Target with Time-Varying Communication Delays

Three-Dimensional Cooperative Guidance Law Against Maneuvering Target with Time-Varying Communication Delays

Distributed Coordination of Networked Manipulators: A Two-Layer Control Scheme

This article studies the coordination control problem of networked manipulators, where manipulators are actuated to cooperatively transport an unknown object along a prescribed trajectory. It is assumed that the accurate position and velocity information of the trajectory is known only to a subset of manipulators. A two-layer control scheme consisting of an estimation layer and a control layer is developed. At the estimation layer, prescribed-time distributed estimators are designed to estimate the position and velocity of the trajectory. The estimation errors are shown to converge to zero in pre-specified time. At the control layer, an event-driven distributed controller with a dynamic triggering mechanism is proposed, where nonuniform time-varying communication delays are considered. A distinctive feature of the proposed controller is that both control updates and communication occur at certain event instants, and thus control update burden and communication costs are reduced. Moreover, two adaptive time-varying control gains are designed so that the controller can be implemented without requiring any inequality condition or global information. Finally, a simulation platform based on MATLAB Robotics Toolbox is designed and implemented to verify the effectiveness and superiority of the proposed two-layer control scheme.

Membership-Function-Based Secondary Frequency Regulation for Distributed Energy Resources in Islanded Microgrids With Communication Delay Compensation

Secondary frequency control is one of the most effective measures to ensure the stable operation of islanded microgrids (MGs). Most research on secondary frequency regulation has only focused on realizing steady-state operation objectives, that is, frequency restoration and power sharing. However, improving the dynamic performance of secondary frequency control is of great importance, especially in synchronous distributed energy resources. These synchronous units can introduce undesired oscillation modes, which may cause the instability conditions of MGs. To improve the dynamic performance of islanded MGs, a membership-function (MF) -based control strategy is proposed. The proposed strategy can trade-off between transient frequency regulation and frequency error elimination using the MF values calculated by the time-stamped synchronized measurements of distribution-level phasor measurement units. Besides, considering the time-varying communication delays in secondary frequency control loops, an adaptive delay compensator is proposed. The weights of the proposed compensator are updated by real-time delay measurements to compensate for the phase lag of control signals. Therefore, the adverse effect of communication delays on secondary frequency control is weakened effectively. Numerical simulations on an IEEE 34-bus system and a typical 40-bus islanded MG system demonstrate the advantages of the proposed method in the secondary frequency regulation of islanded MGs.

Output synchronization of heterogeneous multi-agent systems based on the distributed continuous-discrete state observer

The output synchronization of heterogeneous multi-agent systems is investigated in this note based on the leader–follower architecture. We first propose a distributed continuous-discrete state observer for each follower to continuously estimate the state of the leader only utilizing the discrete samples. The local estimates of the observer are sampled and updated at the periodic sampling time, while the local samples are transmitted aperiodically between neighboring agents. Thus, it allows the asynchronous intermittent communication in the network with the interval time-varying communication delay. Then, the distributed controller is constructed based on the distributed observer to achieve exponential output synchronization. A numerical example is used to illustrate the validity of the theoretical results.

Consensus robustness of multi-agent systems against heterogeneous asymmetric input saturations and asynchronous time-varying communication delays

This paper investigates the combined effect of input saturations and communication delays on the multi-agent consensus over a switching topology of weak connectivity. The input saturations are in a general form such that the saturation level of each agent is asymmetric and those of distinct agents are heterogeneous. Besides, the communication delays are time-varying and those in different channels are asynchronous. Both continuous- and discrete-time multi-agent systems are studied. For both the multi-agent systems over a switching digraph of uniform joint strong connectivity, it is demonstrated that the conventional distributed protocols, despite the simultaneous existence of the input saturations and communication delays, still guarantee the consensus results. It turns out that the consensus results are of great robustness against arbitrary heterogeneous asymmetric input saturations and arbitrary bounded communication delays. Simulations are carried out to verify this finding.