Aperiodically Intermittent Adaptive Event-triggered Control for Linear Multi-agent Systems

Yunlong Zhang,Guoguang Wen,Ahmed Rahmani,Xiaoqin Zhai 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.1

This paper investigates the aperiodically intermittent adaptive event-triggered control strategy for general linear multi-agent systems. The aperiodically intermittent adaptive event-triggered control inherits the respective advantages of aperiodically intermittent control strategy, event-triggered control strategy and adaptive control strategy, which improves communication efficiency, reduces control update frequency and is closer to the practical situations. Firstly, to reach leader-following consensus and save more control resources, a distributed aperiodically intermittent event-triggered scheme is devised, in which the transmission channels among agents only open if the local event-trigger condition is satisfied in predefined time intervals. Then, in order to get rid of continuous inter-agent communication for monitoring the triggering condition, a more general triggering mechanism is presented, in which discrete-time combinational measurement is adopted instead of using continuous-time tracking error directly. Next, to overcome the unexpected large feedback gains in real applications and appropriately tune the feedback gains, the aperiodically intermittent adaptive event-triggered controller is further devised. With aid of the matrix theory, stability theory of switching systems and Lyapunov function, some sufficient criteria are deduced. Moreover, the analyses of excluding the Zeno behavior are included, and explicit positive lower bounds between any two consecutive time intervals are rigorously guaranteed. Finally, the effectiveness for the designed control strategies is validated by simulations.

Event‑triggered adaptive backstepping control for plug‑and‑play parallel converter systems

Chujia Guo,Zhe Kou,Weifeng Liu 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.11

Parallel converter systems are becoming increasingly popular in renewable energy systems as interface converters due to high ride-through capability, low power rate requirement of each submodule, high flexibility, and easy extension with the plug-and-play (PnP) mode. Nevertheless, the number of modules dramatically increase with the growing power requirement, and the communication burden poses one of the main challenges, which will cause unbalanced power sharing and aggravate circulating current. Therefore, a hierarchical event-triggered adaptive backstepping control approach is proposed in this paper. A novel event-triggered mechanism, which includes three event levels to acquire event-triggered signals of submodule PnP, communication packet loss, and undesirable output error, is established. The additional communication approach and control law recalculation are only executed upon detection of event-triggered signals. In addition, an adaptive backstepping control algorithm with a control reference calculation method is designed and embedded in the event-triggered mechanism to ensure the control performance. Finally, the proposed event-triggered adaptive backstepping control method is experimentally demonstrated by a hardware-in-loop experimental platform.

A Distributed Adaptive Mixed Self-/Event-triggered Formation Control Approach for Multiple Stratospheric Airships with Relative State Constraints and Input Delay

Yifei Zhang,Ming Zhu,Tian Chen,Zewei Zheng 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.1

This paper investigates the distributed formation control problem of multiple stratospheric airships in three-dimensional space with several practical problems, such as relative state constraints, input delay, input saturation and disturbances. An adaptive mixed self-/event-triggered formation control scheme is proposed by combining backstepping control, an adaptation technique and a mixed self-/event-triggered control mechanism. First, a novel relative-error-constraint virtual control law is designed based on the barrier Lyapunov function, which is processed into the desired velocity and angular velocity as the input of the next-step designed controller. Then, an adaptive controller is designed based on a designed adaptive law that is utilized to eliminate the influence of external disturbances, input saturation and input delay. In addition, a mixed self-/event-triggered mechanism is designed in the whole system, involving a self-triggered mechanism in the virtual control law and an event-triggered mechanism in the adaptive controller. All signals in the closed-loop system are proven to be semiglobal, uniform and ultimately bounded, and Zeno behavior is proven to be excluded. Finally, the effectiveness of the proposed method is verified through simulations.

Dynamic Control Approach for Network Systems under Event-triggered Communication with Dual Triggers

Yuchao Guo,Cheng Song,Yuan Fan 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.11

This work studies the event-triggered control problem for networked control systems. The plant is controlled directly by a dynamic local controller, which receives the reference control signal from the remote controller. The measurement signal of the plant and the reference control signal of the remote controller have their separate event triggers, and thus the remote controller and the local controller can decide when to transmit signals on their own. It is proved that with the proposed control approach and the dual event triggers, the closed loop system is globally asymptotically stable, which has been illustrated by simulation results.

Finite-time Sliding Mode Fault-tolerant Control for Networked Control Systems With Intermittent Fault Under Event-triggered Scheme

Xinyu Guan,Yanyan Hu,Zengwang Jin,Kaixiang Peng 제어·로봇·시스템학회 2023 International Journal of Control, Automation, and Vol.21 No.10

This paper is focused on the finite-time sliding mode fault-tolerant control problem for a class of discrete networked control systems with intermittent fault and time-varying delay under the event-triggered scheme. The intermittent fault is described as a randomly occurring fault obeying a Bernoulli distribution. The event-triggered mechanism is introduced to determine the transmission of signal, which can conserve communication resources and reduce network burdens. By means of the sliding mode observer method, a linear sliding mode function is constructed by employing the estimated state and fault information. Based on Lyapunov stability theory, sufficient criteria are derived, which can ensure the closed-loop system is finite-time bounded with pre-specified H∞ performance requirement satisfied. Then, the event-triggered observer-based sliding mode fault-tolerant controller is established to force the system state trajectories onto a pre-set sliding mode region. Afterward, the solvability of the non-convex problem is studied by testifying the feasibility of a minimization problem. Finally, a practice simulation result is provided to illustrate the effectiveness of the proposed theoretical results.

Event-triggered Networked H∞ Output Tracking Control Based on Dynamic Compensation Controller

Jinjie Huang,Xiaozhen Pan,Xianzhi Hao 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.10

In this paper, the event-triggered H∞ output tracking problem is investigated for networked control systems. In order to reduce the output tracking error as well as to improve network resource utilization, we propose anidea of dynamic compensation controller with the discrete-time event-triggered mechanism, that is, the integral termof tracking error and the state of the reference system are introduced to form states of the augmented system. We firstexamine the dynamic compensation idea by the H∞ output tracking control problem for linear time-invariant (LTI)systems. Then, we model the closed-loop event-triggered networked control system as a time-delay augmented linear system. By constructing a Lyapunov-Krasovskii functional with the delay fractioning technique, the stabilityconditions with lower conservatism are derived in the form of the linear matrix inequalities (LMIs). Furthermore,a method is proposed to design the H∞ dynamic compensation controllers and the discrete-time event-triggeredmechanisms. Finally, the satellite tracking control problem is used as an example to show that the dynamical compensation idea is effective in reducing the tracking error and that the proposed method in this paper can achievebetter performance than that in the existing literature

Event-triggered decentralized adaptive fault-tolerant control of uncertain interconnected nonlinear systems with actuator failures

Choi, Yun Ho,Yoo, Sung Jin Elsevier 2018 ISA transactions Vol.77 No.-

<P><B>Abstract</B></P> <P>This paper investigates the event-triggered decentralized adaptive tracking problem of a class of uncertain interconnected nonlinear systems with unexpected actuator failures. It is assumed that local control signals are transmitted to local actuators with time-varying faults whenever predefined conditions for triggering events are satisfied. Compared with the existing control-input-based event-triggering strategy for adaptive control of uncertain nonlinear systems, the aim of this paper is to propose a tracking-error-based event-triggering strategy in the decentralized adaptive fault-tolerant tracking framework. The proposed approach can relax drastic changes in control inputs caused by actuator faults in the existing triggering strategy. The stability of the proposed event-triggering control system is analyzed in the Lyapunov sense. Finally, simulation comparisons of the proposed and existing approaches are provided to show the effectiveness of the proposed theoretical result in the presence of actuator faults.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new decentralized event-triggering strategy is firstly considered for the fault-tolerant tracking. </LI> <LI> Undesirable large changes of the triggering inputs caused after the occurrence of the actuator faults can be reduced by using the proposed methodology. </LI> <LI> The stability of the proposed system is analyzed in the Lyapunov sense. </LI> </UL> </P>

Event-triggered Output Feedback Resilient Control for NCSs under Deception Attacks

Lisai Gao,Fuqiang Li,Jingqi Fu 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.9

This paper studies event-triggered output feedback resilient control for networked control systems (NCSs) under stochastic deception attacks following a Bernoulli distribution. Unlike continuous event-triggered mechanism (ETM) requiring dedicated hardware and complex Zeno-avoidance computation, an output-based discrete ETM is firstly introduced, which overcomes limits of continuous ETM and relaxes state-available constraint. Secondly, a novel time-delay system model is established, which makes it possible to study effects of the ETM, stochastic attacks and network-induced delays in a unified framework. Thirdly, less-conservative asymptotic stability criteria with desired H∞ index are obtained, which derive quantitative relationships among the ETM, stochastic attacks, network delays, plant and resilient controller. Further, sufficient conditions to co-deign the ETM and resilient controller are presented. Finally, examples confirm effectiveness of the proposed method.

Adaptive Event-triggered Control for Stochastic Nonlinear Multi-agent Systems with Unknown Control Directions

Jiaang Zhang,Chang-E Ren,Quanxin Fu 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.9

This paper focuses on the adaptive event-triggered consensus control problem for a class of stochastic nonlinear multi-agent systems with unknown nonlinear control directions and external disturbances. The heterogeneous nonlinear dynamics and non-identical unknown control directions are discussed for different agents. The application of the event-triggered mechanism can effectively decrease the update frequency of the controller, and unknown nonlinear dynamics are solved by using fuzzy logic systems. Under the action of the designed distributed controller, all signals of this stochastic multi-agent systems can reach semi-globally uniformly ultimately bounded (SGUUB) in mean square. Furthermore, Zeno behavior can be ruled out by the existence of positive inter-event intervals. Finally, a simulation example is presented to verify the feasibility of the algorithm.

Dynamic Event-triggered Approximate Optimal Control Strategy for Nonlinear Systems

Songsong Cheng,Mingjian Zhu,Yuhui Fu,Xiaohan Fang,Yuan Fan 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.5

This work proposes a novel dynamic event-triggered approximate optimal control strategy for nonlinear continuous-time systems. By employing the dynamic event-triggered control scheme, the purposes of maintaining system stability, approximatly minimizing the cost function, and saving communication as well as computation resources can be achieved simultaneously. Firstly, to obtain the solution of the optimal control problem, we propose the Hamiltonian-Jacobian-Bellman (HJB) equation. A critic network is involved to approximate the optimal discounted cost function. A weight matrix update scheme using gradient descent method is designed to realize the weight calculation of the neural network. Secondly, a dynamic event-triggered condition has been presented to derive a near optimal event-triggered controller, which is more efficient in resource utilization than that of existing results. By using the Lyapunov method, it is proven that the states in the closed-loop system are uniformly ultimately bounded. Finally, numerical results and some comparison with the static ETM and time-triggered systems have been provided to illustrate the effectiveness of the proposed dynamic event-triggered mechanisms (ETM).