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1. Dynamic Intermittent Suboptimal Control: Performance Quantification and Comparisons

   https://doi.org/10.23919/ChiCC.2018.8483352  

   Yang, Yongliang; Vamvoudakis, Kyriakos G.; Modares, Hamidreza; Ding, Dawei; Yin, Yixin; Wunsch, Donald C. (July 2018, 2018 37th Chinese Control Conference (CCC))

   This paper presents a novel intermittent suboptimal event-triggered controller design for continuous-time nonlinear systems. The stability of the equilibrium point of the closed-loop system, and the performances are analyzed and quantified theoretically. It is proven that the static and the dynamic event-triggered suboptimal controllers have a known degree of suboptimality compared to the conventional optimal control policy. In order to generate dynamic event-triggering framework, we introduce an internal dynamical system. Moreover, the Zeno behavior is excluded. Finally, a simulation example is conducted to show the effectiveness of the proposed intermittent mechanisms. 

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2. Dynamic intermittent Q ‐learning–based model‐free suboptimal co‐design of ‐stabilization

   https://doi.org/10.1002/rnc.4515  

   Yang, Yongliang; Vamvoudakis, Kyriakos G.; Ferraz, Henrique; Modares, Hamidreza (March 2019, International Journal of Robust and Nonlinear Control)

   Summary This paper proposes an intermittent model‐free learning algorithm for linear time‐invariant systems, where the control policy and transmission decisions are co‐designed simultaneously while also being subjected to worst‐case disturbances. The control policy is designed by introducing an internal dynamical system to further reduce the transmission rate and provide bandwidth flexibility in cyber‐physical systems. Moreover, aQ‐learning algorithm with two actors and a single critic structure is developed to learn the optimal parameters of aQ‐function. It is shown by using an impulsive system approach that the closed‐loop system has an asymptotically stable equilibrium and that no Zeno behavior occurs. Furthermore, a qualitative performance analysis of the model‐free dynamic intermittent framework is given and shows the degree of suboptimality concerning the optimal continuous updated controller. Finally, a numerical simulation of an unknown system is carried out to highlight the efficacy of the proposed framework. 

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3. Observer-based event-triggered boundary control of the one-phase Stefan problem

   https://doi.org/10.1080/00207179.2024.2313677  

   Rathnayake, Bhathiya; Diagne, Mamadou (December 2024, International Journal of Control)

   This paper presents an observer-based event-triggered boundary control strategy for the one-phase Stefan problem, utilising the position and velocity measurements of the moving interface. The design of the observer and controller is founded on the infinite-dimensional backstepping approach. To implement the continuous-time observer-based controller in an event-triggered framework, we propose a dynamic event triggering condition. This condition specifies the instances when the control input must be updated. Between events, the control input is maintained constant in a Zero-Order-Hold manner. We demonstrate that the dwell-time between successive triggering moments is uniformly bounded from below, thereby precluding Zeno behaviour. The proposed event-triggered boundary control strategy ensures the wellposedness of the closed-loop system and the satisfaction of certain model validity conditions. Additionally, the global exponential convergence of the closed-loop system to the setpoint is established using Lyapunov approach. A simulation example is provided to validate the theoretical findings. 

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4. Distributed Finite-Time Event-Triggered Frequency and Voltage Control of AC Microgrids

   https://doi.org/10.1109/TPWRS.2021.3110263  

   Choi, Jeewon; Habibi, Seyed Iman; Bidram, Ali (September 2021, IEEE Transactions on Power Systems)

   null (Ed.)

   This paper proposes a finite-time event-triggered secondary frequency and voltage control for islanded AC microgrids (MGs) in a distributed fashion. The proposed control strategy can effectively perform frequency restoration and voltage regulations, while sharing the active and reactive power among the distributed generators (DGs) based on their power ratings. The finite-time control enables a system to reach consensus in a finite period of time enhanced from the asymptotic convergence. The event-triggered communication is utilized to reduce the communication burden among the DG controllers by transmitting data among DGs if an event-triggering condition is satisfied. The performance of the proposed finite-time event-triggered frequency control is verified utilizing a hardware-in-the-loop experimental testbed which simulates an AC MG in Opal-RT. 

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5. Dynamic Intermittent Feedback Design for H∞ Containment Control on a Directed Graph

   https://doi.org/10.1109/TCYB.2019.2933736  

   Yang, Yongliang; Modares, Hamidreza; Vamvoudakis, Kyriakos G.; Yin, Yixin; Wunsch, Donald C. (October 2019, IEEE Transactions on Cybernetics)

   This article develops a novel distributed intermittent control framework with the ultimate goal of reducing the communication burden in containment control of multiagent systems communicating via a directed graph. Agents are assumed to be under disturbance and communicate on a directed graph. Both static and dynamic intermittent protocols are proposed. Intermittent H∞ containment control design is considered to attenuate the effect of the disturbance and the game algebraic Riccati equation (GARE) is employed to design the coupling and feedback gains for both static and dynamic intermittent feedback. A novel scheme is then used to unify continuous, static, and dynamic intermittent containment protocols. Finally, simulation results verify the efficacy of the proposed approach. 

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