Sampled-data Output Feedback Research Articles

Sampled-Data Output Feedback Leader-Following Scaled Consensus for Uncertain Nonlinear Multiagent Systems With Communication Delays and Noises

Communication delays and noises are common in practical problems. When they exist in the nonlinear multiagent system, this article addresses the leader-following scaled consensus problem. In the concerned system, nonlinearities can contain uncertainty and essential time-varying characteristic, and the output information is only available at sampling instants. In this article, we propose a class of time-varying gains to design the delay-dependent observer and control protocol, where a newly defined variable is used to cope with unknown noises. Under the output feedback control protocol, followers can asymptotically track the leader by assigned ratios. Different from existing works, the sampling period, communication delays, and noises are not restricted to a fixed upper bound. Two simulation examples are eventually presented to show the effectiveness of the proposed control protocol. Some future works can extend to general nonlinear systems with communication noises, and different time-varying delays.

Global tracking stabilisation via sampled-data output feedback for nonlinear systems with unknown measurement sensitivity

In engineering practice, sensors commonly have limited sensitivity errors, which are allowed in the design process. This paper uses a sampled-data output feedback control method so that the problem of global tracking stabilisation of a class of nonlinear systems with unknown measurement sensitivity can be solved. A sampled-data output feedback control law and a sampled-data observer are constructed with the help of output feedback domination method. By choosing the domination gain and sampling period in place, the resultant control law can globally stabilise the system even under the influence of unknown measurement sensitivity.

Practical Finite-Time Sampled-Data Output Feedback Stabilization for a Class of Upper-Triangular Nonlinear Systems With Input Delay

Practical Finite-Time Sampled-Data Output Feedback Stabilization for a Class of Upper-Triangular Nonlinear Systems With Input Delay

Predictor-Based Global Sampled-Data Output Feedback Stabilization for Nonlinear Uncertain Systems Subject to Delayed Output

In this article, we address the problem of global sampled-data output feedback stabilization for a class of nonlinear uncertain systems with delayed output using the continuous-discrete method. Thanks to the prediction technique and feedback domination method, a novel coupled design method of predictor-based continuous-discrete observer and linear controller is proposed when only delayed sampled-data output is accessible. The proposed predictor-based observer can effectively estimate the unknown state by compensating the influences of sampling and output delay. The main advantage of the proposed control method is that the full state information and accurate model nonlinearities do not need to be known any more. The global exponential stability of the overall hybrid control system can be ensured when there hold some sufficient conditions with respect to the maximum allowable sampling period and output delay.

Symplectic discrete-time Krasovskii passivity-based control for output consensus*

In this paper, we design a sampled-data distributed output feedback controller to achieve output consensus for linear continuous-time port-Hamiltonian systems in presence of unknown disturbances. The key idea is borrowed from Krasovskii passivity-based output consensus control for continuous-time dynamics. To conceptualise this rationale to sampled control systems, we deal with a discrete-time system arising from a symplectic discretization of a continuous-time linear port-Hamiltonian system, such as the implicit midpoint method. As a preliminary step, we introduce the concept of Krasovskii passivity for discrete-time systems and further show that a discretized linear port-Hamiltonian system is Krasovskii passive in the discrete-time sense. Then, based on the discrete-time version of Krasovskii passivity, we develop a sampled-data output feedback controller to achieve output consensus. The proposed sampled-data controller can be understood as a symplectic discretization of the continuous-time output consensus controller. Finally, we illustrate the effectiveness of the main result by achieving current sharing in a DC power network.

On the Finite-Time Stabilization for a Class of Interconnected Switched Nonlinear Systems via Sampled-Data Output Feedback Control

This article investigates the problem of finite-time stabilization for a class of interconnected switched nonlinear systems (ISNS) via sampled-data output feedback control. First, for each subsystem, the state observers and sampled-data output feedback controllers are constructed. Second, with a selected design parameter and a suitable sampling period, the finite-time stabilization is proved based on the homogeneous theory and related inequalities for the discussed ISNS. Finally, the effectiveness of the presented control method is verified with a numerical example and a practical example.

Sampled-Data Stabilization of Stochastic Interconnected Cyber-Physical Systems Under DoS Attacks

Cyber-physical systems (CPSs) can be accessed and controlled remotely, which increases their application prospects; however, these characteristics also make them more vulnerable to cyberattacks. In addition, an increasing number of resource-saving sampled-data control methods have attracted attention in the field of research. How to ensure the stability of the system that is attacked by cyberattacks and to reduce further the communication resources is a challenge. In this article, we study the security control problem of stochastic interconnected CPSs under two-channel denial-of-service attacks based on sampled-data output-feedback. First, the state observer and controller are designed with only the system output of the sampling points in the nonattack intervals. Next, the time intervals related to stable and unstable dynamics are distinguished. By analyzing the Lyapunov function in the intervals classified as previously mentioned respectively, the relationship between the sampling period and attack characteristics is derived to ensure that the system is globally mean-square uniformly ultimately bounded. The simulation results are presented to substantiate the analysis.

Membership-Function-Dependent Control Design of Interval Type-2 Sampled-Data Fuzzy-Model-Based Output-Feedback Tracking Control System

This article focuses on the stability analysis and control design of an interval type-2 sampled-data fuzzy-model-based output-feedback (IT2SDFMBOF) tracking control system, which is formed by the interval type-2 (IT2) Takagi–Sugeno (T–S) fuzzy model, the stable reference model, and the interval type-2 sampled-data output-feedback (IT2SDOF) fuzzy controller. The design goal is to establish a proper IT2SDOF fuzzy controller that is able to drive the states of the nonlinear plant subject to uncertainties to track those of the stable reference model, and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_\infty$</tex-math></inline-formula> performance index is adopted to optimize the tracking control performance. To improve the robustness of the IT2SDOF fuzzy controller against uncertainties of the nonlinear plant, IT2 fuzzy sets are utilized. Considering that the tracking control system is sampled-data (SD) type, a two-sided looped-functional-based approach exploiting the information on the interval from time <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$t_k$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$t$</tex-math></inline-formula> and the interval from time <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$t$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$t_{k+1}$</tex-math></inline-formula> is applied to enhance the stability analysis. The imperfect premise matching (IPM) concept permits the number of rules and the premise membership functions of the IT2 T-S fuzzy model and the IT2SDOF fuzzy controller to be different, which can be employed to promote the design flexibility. The tracking control system with the SD type and IPM design will cause the membership grades between the IT2 T-S fuzzy model and the IT2SDOF fuzzy controller to be mismatched. In addition, the membership-function-dependent stability analysis approach that can introduce the boundary information of membership functions into the stability analysis is used to relax the stability conditions. The relaxed stability conditions subject to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$H_\infty$</tex-math></inline-formula> performance building on the Lyapunov stability theory are developed in terms of linear matrix inequalities. Simulation results demonstrate the effectiveness of the proposed IT2SDFMBOF tracking control system.

Sampled-Data Semi-Global Robust Output Regulation for a Class of Nonlinear Systems

This paper investigates the semi-global robust output regulation problem for a class of uncertain nonlinear systems via a sampled-data output feedback control law. What makes the results interesting is that the nonlinearities of the proposed system do not have to satisfy linear growth condition and the uncertain parameters of our system are allowed to belong to some arbitrarily large prescribed compact subset. Two cases are considered. The first case is that the exogenous signal is constant. The second case is that the exogenous signal is time-varying and bounded. For the first case, the authors solve the problem exactly in the sense that the tracking error approaches zero asymptotically. For the second case, the authors solve the problem practically in the sense that the steady-state tracking error can be made arbitrarily small. Finally, an example is given to illustrate the effectiveness of our approach.

Nonlinear lateral motion stability control method for electric vehicle based on the combination of dual extended state observer and domination approach via sampled-data output feedback

This paper studies lateral motion stability control method for an electric vehicle (EV) with uncertain disturbances. Aiming to suppress the influence of uncertain disturbances, a novel method based on the combination of dual extended state observer (dESO) and domination approach is proposed. The proposed method enables the designed controller just to adopt a smaller scaling gain than the classic domination method, which is more practical for the controller in engineering. Firstly, a dESO is proposed to estimate the uncertain disturbances of the system. Also, a sampled-data output feedback domination approach is designed to dominate the disturbances by using a scaling gain. Then, the sampled-data output feedback control law is constructed based on the dESO and domination approach called dESOD. Furthermore, the stability analysis is presented to show that the proposed sampled-data controller can guarantee the closed-loop system globally asymptotically stable. Finally, the simulations and experiment results show the effectiveness of the proposed method.

New results and examples in semiglobal asymptotic stabilization of nonaffine systems by sampled-data output feedback

For a class of SISO non-affine systems, we address the problem of how semiglobal asymptotic stabilization (SGAS) can be achieved by n-dimensional sampled-data output feedback. The new result of this paper gives a partial answer to the open question in the recent work Lin (2020), where (2n−1)-dimensional output feedback controllers were designed based on the dynamic extension method.

Exponential stabilisation for nonlinear PDE systems via sampled-data static output feedback control

ABSTRACT This paper focuses on the problem of exponential stabilisation for nonlinear partial differential equation (PDE) systems by designing sampled-data static output feedback controller. First, the nonlinear PDE systems are reconstructed by Takagi-Sugeno (T-S) fuzzy model. Subsequently, the closed-loop systems are obtained by introducing sampled-data static output feedback fuzzy controller. Then, stability conditions of the closed-loop system are obtained based on Lyapunov function approach, which can guarantee that the considered systems are exponential stabilisation and satisfy dissipative performance. Finally, the effectiveness of the developed method is demonstrated by a simulation study.

Sampled-data output feedback control for a class of high-order switched nonlinear systems

In this paper, we design new sampled-data output feedback controllers to globally stabilise a class of high-order switched nonlinear systems in finite time under arbitrary switching. The switching signals exist in both the system powers and the nonlinear terms. First, we adopt the common Lyapunov function method to design a continuous-time output feedback controller. Then, the emulation method is used to construct the sampled-data output feedback controllers with a sampling period. Based on the homogeneity theory, Hölder inequality and Gronwall–Bellman inequality, the relationships between the sampling states (controllers) and the current states (controllers) are revealed. In the meantime, we obtain the sampling period for the sampled-data output feedback controllers to guarantee the global stabilisation of the closed-loop systems in finite time. Finally, a numerical example and a practical example are given to prove the efficiency of the proposed control method.

Global Decentralized Control of $p$-Normal Large-Scale Nonlinear Systems Based on Sampled-Data Output Feedback

This article considers the global decentralized sampled-data output feedback control problem for large-scale nonlinear systems in the p-normal form. To estimate unavailable states, a sampled-data observer is designed. Under suitable scaling gains and an allowable sampling period, a decentralized sampled-data control law is presented to ensure the globally asymptotically stability of the corresponding closed-loop system. Finally, simulation examples are provided to verify the validity of the designed strategy.

Filtered adaptive constrained sampled-data output feedback control for uncertain multivariable nonlinear systems

This paper synthesises a constrained sampled-data output feedback controller for uncertain multivariable nonlinear systems in the presence of various constraints, using the filtered adaptive control architecture. Nonlinear uncertainties are estimated online by solving the error dynamics between the output predictor and the real system with the neglection of unknowns, the yielded adaptive parameters are piecewise constant. In the proposed control scheme, the nonlinear uncertainties are compensated for within the bandwidth of low-pass filters, while the trade-off between tracking and constraints violation avoidance is formulated as a numerical constrained optimisation problem which is solved periodically. Priority is given to constraints violation avoidance at the cost of deteriorated tracking performance. System transformations are performed to find the sufficient conditions that can guarantee the stability of the closed-loop system with the sampled-data controller, where both the states and control inputs are held constant over the sampling period.

Sampled-data stabilization of a class of nonlinear differential algebraic systems via partial-state and output feedback

In this paper, the problem of sampled-data stabilization for a class of nonlinear differential-algebraic systems is considered by using partial-state and output feedback. First, based on the output feedback domination approach, a systematic design procedure for sampled-data output feedback controller is proposed without using the states of the algebraic subsystem. It is shown that the proposed sampled-data controller can ensure the whole closed-loop nonlinear differential-algebraic system is asymptotically stable by choosing appropriate scaling gains and sampling period. In addition, due to the domination nature of the proposed method, the obtained results can be extended to more general class of nonlinear differential-algebraic systems easily. Finally, simulation examples are provided to illustrate the effectiveness of the proposed control method.

When Is a Nonlinear System Semiglobally Asymptotically Stabilizable by Digital Feedback?

For multi-input–multi-output (MIMO) nonlinear systems, we prove that while global asymptotic stabilizability may not ensure semiglobal asymptotic stabilizability (SGAS) by sampled-data state feedback, global asymptotic plus local exponential stabilizability (GALES) does imply the existence of an SGAS sampled-data state feedback controller. Based on this result, we further prove the main contribution of this article: GALES and uniform observability imply SGAS by sampled-data output feedback, which is indeed a hybrid version of the “separation principle” for nonlinear systems. The development of the “digital separation principle” is made possible by employing a subtle Lyapunov argument that makes the estimation of domains of attraction and semiglobal asymptotic analysis relatively intuitive and simple, without involving intricate Lyapunov functions and the corresponding level sets. Results on SGAS by sampled-data feedback for representative classes of nonlinear systems are also given as illustrations.

Sampled-data output feedback controllers for nonlinear systems with time-varying measurement and control delays

Abstract In this paper, we propose sampled-data output feedback controllers for nonlinear systems with time-varying measurement and input delays. A state prediction is generated by chains of saturated high-gain observers with switching error-correction terms and the state prediction is used to stabilize the system with saturated controls. The observers reconstruct the unmeasurable states at different delayed time-instants, which partition the maximal variation interval of the time-varying delays. The density of these delayed time instant depend both on the magnitude of the delays and the growth rate of the nonlinearities. Our sampled-data feedback controllers are obtained as zero-order discretizations of continuous time controllers.

Networked Output Feedback Control for a Class of Uncertain Nonlinear Time-Delay Systems

This paper studies the global stabilization problem for a class of uncertain time-delay nonlinear systems by designing a sampled-data output feedback controller via network. Under a lower triangular linear growth condition, when only the output is measurable, a sampled-data output feedback network controller, whose observer and control law are both linear, is constructed to solve the stabilization problem. Using a feedback domination design approach which substantially differs from the separation principle, we explicitly construct a Lyapunov–Krasovskill functional to prove the global asymptotic stability with the help of inductive proof method. The control law is discrete-time and linear, hence simulation examples be easily implemented with computers to show the effectiveness of our proposed method.

Global sampled-data output feedback stabilization for a class of switched stochastic nonlinear systems with quantized input and unknown output gain

This paper aims at addressing the sampled-data output feedback control problem for a class of uncertain switched stochastic nonlinear systems, whose control input is quantized by a logarithmic quantizer and the output gain cannot be precisely known. We design a compensator with the quantized information. With the help of the feedback domination approach and the backstepping design method, a sampled-data output feedback controller is constructed with appropriate design parameters and a maximum sampling period to guarantee the global exponential stability in mean square of the closed-loop system under arbitrary switching. Finally, a numerical example is given to illustrate the effectiveness of the proposed scheme.