Article
Automation & Control Systems
Kexue Zhang, Bahman Gharesifard, Elena Braverman
Summary: This article studies the event-triggered control problem of general nonlinear systems with time delay and proposes a novel event-triggering scheme that guarantees the global asymptotic stability, uniform boundedness, and/or global attractiveness of the resulting closed-loop systems. Sufficient conditions for excluding Zeno behavior are derived, and two illustrative examples are provided to demonstrate the theoretical results.
IEEE TRANSACTIONS ON AUTOMATIC CONTROL
(2022)
Article
Automation & Control Systems
Ramasamy Subramaniyam, Young Hoon Joo
Summary: This manuscript presents a method for stabilizing discrete-time Takagi-Sugeno (T-S) fuzzy systems with additive time-varying delay components. By constructing a fuzzy Lyapunov-Krasovskii functional (LKF) with membership functions, the stability criteria for the systems with additive time-varying delays are established. The extended version of Wirtinger's inequality is used to bound the forward differences of the LKF. A fuzzy controller is designed to ensure the H-infinity performance of the closed-loop system formulated in terms of linear matrix inequalities (LMIs). Numerical simulations are conducted to validate the theoretical findings.
INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL
(2023)
Article
Multidisciplinary Sciences
Ziheng Zhang, Zhongtao Liu, Na Liu, Weikai He, Fuchun Yang
Summary: This paper focuses on the adaptive tracking control problem for nonlinear systems, incorporating virtual control coefficients that consist of known and unknown items. Known items are utilized directly for controller design, while an auxiliary system is introduced to handle unknown items, ensuring the practical boundedness of signals in the closed-loop system.
SCIENTIFIC REPORTS
(2023)
Article
Automation & Control Systems
Zhengqiang Zhang, Bin Xu, Cheng Tan, Shuzhi Sam Ge
Summary: This article addresses the adaptive state feedback stabilization for delayed uncertain systems with external disturbance. A new Lyapunov-Krasovskii functional is introduced to present a memoryless control strategy for stabilizing nonlinear time-delay systems through a newly defined control gain function. The main contribution lies in the construction of control gain function, which ensures the asymptotic stability of the closed delayed nonlinear system. Simulation examples are provided to demonstrate the effectiveness of the proposed method.
IEEE TRANSACTIONS ON SYSTEMS MAN CYBERNETICS-SYSTEMS
(2022)
Article
Mathematics, Applied
Gongfei Song, Zimeng Zhang, Yanan Zhu, Tao Li
Summary: This work investigates the discrete-time state feedback control problem for neutral stochastic delay systems with highly nonlinear coefficients. Conventional methods are not applicable due to the presence of highly nonlinear terms, neutral term, and discrete time observation values. A more general Lyapunov function is constructed to prove the stability of the designed controller, and different stability conditions of the corresponding systems are presented. A numerical case is provided to validate the proposed theoretical results.
APPLIED MATHEMATICS AND COMPUTATION
(2022)
Article
Computer Science, Information Systems
Kun Wang, Xiaoping Liu, Yuanwei Jing
Summary: The paper presents a novel finite-time command filtered backstepping approach to address the issue of state constraints in nonlinear systems, ensuring finite-time convergence of tracking errors while reducing computational complexity. The proposed method also guarantees that state variables are restricted in compact bounding sets, and is applied to TCP/AQM network systems to ensure practical boundedness of signals in the closed-loop system. Finally, the effectiveness of the control strategy is validated through a TCP network simulation example.
INFORMATION SCIENCES
(2021)
Article
Automation & Control Systems
Wenjie Li, Zhengqiang Zhang, Shuzhi Sam Ge
Summary: In this article, the output-feedback control problem for a class of nonlinear time-delay systems is studied. Novel Lyapunov-Krasovkii functionals with control gains are proposed for designing a delay-independent controller. The effectiveness of the control scheme is illustrated through simulation results.
IEEE TRANSACTIONS ON SYSTEMS MAN CYBERNETICS-SYSTEMS
(2022)
Article
Automation & Control Systems
Xiao Liang, Peng Zhang, Yongchun Fang, He Lin, Wei He
Summary: This study proposes a novel nonlinear antiswing controller for aerial transportation systems with consideration of double-pendulum swing effects, aiming to improve control performance. Experimental results demonstrate that the proposed control scheme exhibits better transient response compared to traditional methods.
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
(2021)
Article
Automation & Control Systems
Wenjie Li, Zhengqiang Zhang, Shuzhi Sam Ge
Summary: This article addresses the problem of output feedback control design for a class of strict-feedback nonlinear systems with unknown state time-varying delays. Two output feedback control schemes based on full-order and reduced-order observers are considered. Novel memoryless control strategies are developed using Lyapunov-Krasovskii functionals with static gain. The work ensures boundedness of all the signals in the closed-loop system and asymptotic stability of the system. Finally, two simulation examples illustrate the effectiveness of the proposed control schemes.
IEEE TRANSACTIONS ON SYSTEMS MAN CYBERNETICS-SYSTEMS
(2023)
Article
Robotics
Amir Zakerimanesh, Mojtaba Sharifi, Farzad Hashemzadeh, Mahdi Tavakoli
Summary: This letter introduces a novel controller for joint position tracking in bilateral teleoperation systems with time-varying communication delays and bounded actuation. The controller addresses the trade-off between settling time of synchronization and magnitude of time-delay by using capped joint-velocity. Through analytical study, the controller's parameters are set to ensure the closed-loop dynamics' asymptotic stability, which is validated through numerical simulations and experimental evaluations.
IEEE ROBOTICS AND AUTOMATION LETTERS
(2021)
Article
Automation & Control Systems
Peng-Ju Ning, Chang -Chun Hua, Kuo Li, Hao Li
Summary: This paper addresses the problem of prescribed-time control for a class of nonlinear uncertain time-delay systems. It presents the definition of prescribed-time stability for nonlinear time-delay systems and discusses the necessary conditions for achieving finite-time stabilization. A prescribed-time Lyapunov stability theorem is proposed using a prescribed-time adjustment function and Lyapunov-Krasovskii (L-K) functional method. The stability of the resulting closed-loop system is proved, and different scenarios for uncertain time-delay systems are discussed. A continuous controller is designed for a first-order fully actuated system, and the impact of different prescribed-time adjustment functions on the controller is studied. A simulation example is provided to demonstrate the effectiveness of the theoretical results.
Article
Engineering, Mechanical
Jianfeng Wang, Ping Zhang, Yan Wang, Zhicheng Ji
Summary: This paper investigates the problem of adaptive optimal tracking control for full-state constrained strict-feedback nonlinear systems with input delay. A novel control approach is developed by combining the backstepping design technique and adaptive dynamic programming (ADP) theory. The approach utilizes Pade approximation to handle input delay and barrier Lyapunov functions for state constraints. Neural networks are employed to approximate unknown functions. An adaptive backstepping feedforward controller is developed to convert the tracking task into an equivalent regulation problem. A critic network is constructed within the ADP framework to obtain the optimal control. The resulting controller consists of feedforward and feedback parts, while ensuring that all signals are uniformly ultimately bounded in the closed-loop system.
NONLINEAR DYNAMICS
(2023)
Article
Automation & Control Systems
Jing Xu, Leonid M. Fridman, Emilia Fridman, Yugang Niu
Summary: This paper introduces an output-feedback Lyapunov redesign approach for uncertain systems with delayed measurements, which combines state estimation and robust control into a unified framework. By constructing a static state estimator and sliding variable, as well as using Lyapunov redesign approach, the system trajectory can be maintained in the predefined vicinity of origin despite approximation errors and disturbances.
INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL
(2021)
Article
Mathematics, Applied
Wenping Cao, Quanxin Zhu
Summary: This paper studies the input-to-state stability of a class of stochastic delay differential equations with delay impulses. Different types of stability conditions are established by considering the cases where the continuous stochastic delay system is stable and unstable, using the average dwell time and vector Lyapunov function method. The validity of the results is verified through two examples.
APPLIED MATHEMATICS AND COMPUTATION
(2022)
Article
Automation & Control Systems
Alessandro Borri, Pierdomenico Pepe
Summary: This article presents a method for event-triggered stabilization of nonlinear time-delay systems, utilizing control Lyapunov-Razumikhin functions and a spline-based approximation of functional state feedback to achieve a finite-memory controller, ensuring positive minimal interevent time while avoiding continuous-state monitoring. Application examples demonstrate the potential of this approach.
IEEE TRANSACTIONS ON AUTOMATIC CONTROL
(2021)
Article
Automation & Control Systems
Yang Zheng, Aivar Sootla, Antonis Papachristodoulou
Summary: This article introduces a new notion of block factor-width-two matrices and builds a new hierarchy of inner and outer approximations of the cone of positive semidefinite matrices. This improves the inner-approximation of the PSD cone. In the context of SOS optimization, this leads to a block extension of the scaled diagonally dominant sum-of-squares polynomials. Numerical experiments confirm the theoretical findings.
IEEE TRANSACTIONS ON AUTOMATIC CONTROL
(2023)
Article
Automation & Control Systems
Jared Miller, Yang Zheng, Mario Sznaier, Antonis Papachristodoulou
Summary: This paper presents a concept of decomposed structured subsets to approximate an SDP with structured subsets after an equivalent conversion. The lower/upper bounds found by approximation after conversion become tighter than the bounds obtained by approximating the original SDP directly.
Article
Automation & Control Systems
Giorgio Valmorbida, Antonis Papachristodoulou
Summary: This article presents strategies for the state-feedback control law design of nonlinear control laws with saturating inputs. The input constraints are handled by considering a generalized local sector inequality, allowing the study of nonsymmetric saturation bounds. A numerical formulation based on solving Lyapunov inequalities with sum-of-squares programming is presented for polynomial systems.
IEEE TRANSACTIONS ON AUTOMATIC CONTROL
(2022)
Article
Automation & Control Systems
Han Shu, Xuan Zhang, Na Li, Antonis Papachristodoulou
Summary: This article presents a control reconfiguration approach to improve the performance of two classes of dynamical systems. The approach involves a three-step procedure of reverse-engineering, forward-engineering, and comparing dynamics to redesign and improve the given system. Internet congestion control and distributed proportional-integral control are used as applications to showcase the effectiveness of the proposed approach.
IEEE TRANSACTIONS ON AUTOMATIC CONTROL
(2022)
Article
Biochemical Research Methods
Boon Lim, Yutong Yin, Hua Ye, Zhanfeng Cui, Antonis Papachristodoulou, Wei E. Huang
Summary: Advances in synthetic biology have enabled the reprogramming of bacteria to specifically target tumors and release anticancer drugs in a controlled manner. SimCells, chromosome-free bacteria controlled by gene circuits, have been engineered to display antibodies on their surface and effectively bind and induce death of cancer cells expressing specific biomarkers. These findings highlight the potential of SimCells for targeted cancer therapy and the application of synthetic biology in medicine.
ACS SYNTHETIC BIOLOGY
(2022)
Article
Automation & Control Systems
Han Wang, Kostas Margellos, Antonis Papachristodoulou
Summary: This paper introduces a novel Time-Triggered Dimension Reduction Algorithm (TTDRA) for solving the task assignment problem. The algorithm accelerates computational speed by convexifying the constraints and cost function. Numerical simulations verify the optimality and computational efficiency of the algorithm.
EUROPEAN JOURNAL OF CONTROL
(2022)
Article
Automation & Control Systems
Licio Romao, Kostas Margellos, Antonis Papachristodoulou
Summary: In this study, we propose a removal scheme with a less conservative bound on constraint violation probability. By extending the number of discarded scenarios, we improve the theoretical properties of the sampling-and-discarding scheme. Our results show that our feasibility guarantees outperform the standard approach, but also highlight the inherent property of introducing additional conservatism when the number of discarded scenarios is not an integer multiple of the decision space dimension.
Review
Biotechnology & Applied Microbiology
Miroslav Gasparek, Harrison Steel, Antonis Papachristodoulou
Summary: Living organisms produce a variety of metabolites that are of interest to the pharmaceutical industry due to their potential medicinal properties. Co-culturing producer species with specific inducer microbes is an effective method to activate silent gene clusters and produce secondary metabolites. However, the mechanisms and means of induction in co-cultures are not well understood, which limits the diversity and yield of valuable compounds. This review summarizes the known physiological mechanisms of secondary metabolite production in inducer-producer consortia and discusses approaches to optimize their discovery and production.
BIOTECHNOLOGY ADVANCES
(2023)
Article
Automation & Control Systems
Licio Romao, Antonis Papachristodoulou, Kostas Margellos
Summary: We revisit the sampling and discarding approach used for quantifying the probability of constraint violation in convex scenario programs. We propose a removal scheme that consists of a cascade of optimization problems, which leads to less conservative bounds for the probability of constraint violation compared to existing methods. We also provide evidence of the tightness of the proposed bound by characterizing a class of optimization problems that achieve the given upper bound. The improved performance of the proposed methodology is illustrated through an example involving a resource sharing linear program.
IEEE TRANSACTIONS ON AUTOMATIC CONTROL
(2023)
Proceedings Paper
Automation & Control Systems
Han Wang, Kostas Margellos, Antonis Papachristodoulou
Summary: This paper introduces the application of the control barrier function approach in the synthesis of safe controllers and proposes a method to explicitly synthesize a safe control law for nonlinear control-affine systems with limited control ability. By transforming the online quadratic programming problem into an offline parameterized optimization problem, considering states as parameters, a piece-wise Lipschitz continuous function as an explicit safe controller can be obtained.
2022 IEEE 61ST CONFERENCE ON DECISION AND CONTROL (CDC)
(2022)
Proceedings Paper
Automation & Control Systems
Matthew Newton, Antonis Papachristodoulou
Summary: Neural networks have become increasingly popular in control feedback systems, but providing robustness guarantees is challenging. Current research focuses on addressing the sensitivity to adversarial inputs through computing outer-approximations of reachable sets and using a sparse polynomial optimization framework with Positivstellensatz. Our method shows tighter bounds and reasonable computational time compared to similar methods, and it can handle non-linear polynomial dynamics.
2022 IEEE 61ST CONFERENCE ON DECISION AND CONTROL (CDC)
(2022)
Proceedings Paper
Automation & Control Systems
Matthew Newton, Antonis Papachristodoulou
Summary: This paper presents a method using a Sum of Squares programming framework to directly compute the stability of non-linear systems with neural network controllers. By proposing higher order candidate Lyapunov functions and constraint multipliers, the method is able to better capture the non-linear dynamics of the system and the neural network.
2022 IEEE 61ST CONFERENCE ON DECISION AND CONTROL (CDC)
(2022)
Article
Automation & Control Systems
Emmanouil Alexis, Luca Cardelli, Antonis Papachristodoulou
Summary: Here, a highly tunable PID bio-controller is introduced and its performance is compared to PI regulation using numerical simulations.
IEEE CONTROL SYSTEMS LETTERS
(2022)
Article
Multidisciplinary Sciences
Aivar Sootla, Nicolas Delalez, Emmanouil Alexis, Arthur Norman, Harrison Steel, George H. Wadhams, Antonis Papachristodoulou
Summary: We present a new design framework, called 'dichotomous feedback', for implementing negative feedback regulation in synthetic biology. This approach utilizes the existing fluxes in the process to be controlled and takes advantage of the process's architecture to design the control law. This mechanism of signal sequestration is commonly found in biological systems and is potentially easier to achieve compared to other methods. By linking the strength of signal sequestration to the process output, our feedback regulation mechanism shapes the signal response, reduces noise, and improves system robustness.
JOURNAL OF THE ROYAL SOCIETY INTERFACE
(2022)
Article
Microbiology
Carolin C. M. Schulte, Vinoy K. Ramachandran, Antonis Papachristodoulou, Philip S. Poole
Summary: This study reconstructed a genome-scale metabolic model for Rhizobium leguminosarum and integrated various experimental data sets to investigate the metabolic characteristics of rhizosphere bacteria, undifferentiated bacteria inside root nodules, and nitrogen-fixing bacteroids. These findings provide a framework for future experimental studies and help advance efforts to engineer novel symbioses with cereal crops for sustainable agriculture.