Continuous Output Feedback Controller Research Articles

Fault-Tolerant Control for Quadrotor Based on Fixed-Time ESO

Focusing on the actuator fault of the quadrotor unmanned aerial vehicle (QUAV), an active fault-tolerant control scheme based on fixed-time linear active disturbance rejection control is proposed. Firstly, in order to simplify the complex dynamic model, the virtual control quantity is introduced to decouple the flight control system of the QUAV. Secondly, the fixed-time extended state observer (ESO) is utilized to estimate and compensate the internal uncertainty, external disturbance and actuator fault of the QUAV in fixed time. Thirdly, a continuous output feedback controller based on fixed-time ESO is designed to keep the stability of the flight control system with actuator fault and external disturbance. Finally, the closed-loop stability of the flight control system is demonstrated by Lyapunov function. The numerical simulation is carried and the results also verify the effectiveness of the proposed control scheme.

Global stabilization via output feedback for a class of uncertainty nonlinear systems with time-varying delay and zero dynamics

This paper proposes a new control strategy to deal with three different types of uncertainties for a class of time-varying delay nonlinear systems. Quite different from related celebrated works, the considered systems allow the existence of parameter uncertainties in the output function and nonlinearities, dynamic uncertainties of the unmeasurable state, and continuous external disturbances, which invokes the motivation of the paper. The objective is to construct a continuous output feedback controller by utilizing a new restructured integral function and the double-domination method. The novelty control design is the capability of tackling zero-dynamic and unknown output function simultaneously, thereby guaranteeing the state convergence of the closed-loop system. Finally, the proposed scheme is applied to a practical example and a numerical one simultaneously to demonstrate the effectiveness and the superiority.

Global stabilization of a class of nonlinear systems with polynomial nonlinearities by output feedback

This article deals with the problem of global stabilization by output feedback for a class of nonlinear systems with high-order and low-order nonlinearities. By generalizing a reduced-dimensional design method, adding a power integrator technique and choosing an appropriate Lyapunov function, a continuous output feedback controller is constructed. A simulation example is given to verify the effectiveness of the proposed scheme.

Output feedback control for aircraft at high angle of attack based upon fixed-time extended state observer

This paper presents a novel fixed-time extended state observer (FXTESO)-based fixed-time output feedback control scheme for aircraft with thrust vector at high angle of attack. In order to enhance the robustness of the closed-loop control system, a FXTESO is designed to estimate and compensate model uncertainties, external disturbance and the strong coupling among different channels. Furthermore, theoretical analysis shows that the convergence time of FXTESO is independent of initial estimation errors. For the double integrator systems obtained by FXTESO feedback linearization, a continuous output feedback control is utilized to obtain expected performance and fixed-time stability. The stability analysis for the closed-loop aircraft control system is conducted by Lyapunov theory. The daisy chain method is adopted to realize the control allocation. Finally, several numerical simulations are provided to demonstrate the effectiveness and robustness of the proposed methodology.

A Continuous Finite-Time Output Feedback Control Scheme and Its Application in Quadrotor UAVs

A continuous output feedback control scheme is presented for double integrator systems subject to non-vanishing perturbation. In the method, no explicit state observer or disturbance observer is designed. The geometric homogeneity technique and Lyapunov stability theory are utilized to ensure the global finite-time stability of the closed-loop system. The extension of the algorithm to multi-input multi-output is developed, and its application in quadrotor unmanned aerial vehicles is investigated. Finally, the numerical simulation results are provided to validate the efficiency of the proposed method.

A fixed-time output feedback control scheme for double integrator systems

A continuous output feedback control scheme rendering the closed-loop double integrator system globally stable in finite-time is presented. In particular, the convergence time is independent of initial conditions. The bi-limit homogeneous technique is used for controller and observer designs with fixed-time convergence. Then, a continuous output feedback control law is proposed for nominal double-integrator system and its perturbed version. The homogeneity and Lyapunov techniques are used to ensure the fixed-time stability of the closed-loop system under output feedback control framework. Finally, the efficiency of the proposed algorithms is illustrated by numerical simulations.

Robust output feedback attitude tracking control for rigid-flexible coupling spacecraft

This paper investigates the robust attitude tracking control problem for a rigid-flexible coupling spacecraft. First, the dynamic model for a rigid-flexible coupling spacecraft is established based on the first-order approximation method to fully reveal the coupling effect between rigid movement and flexible displacement when the spacecraft is in rapid maneuver. In the condition that flexible vibration measurements are not available, an robust output feedback controller which is independent of model is presented using Lyapunov method with considering state-independent disturbances. To resolve the chattering problem caused by the discontinuous sign function, a modified continuous output feedback controller is proposed by introducing functions with continuous property. Rigorous proof is achieved showing that the proposed control law ensures asymptotic stability and guarantees the attitude of a rigid-flexible spacecraft to track a time-varying reference attitude based on angle and angular velocity measurements only. Finally, simulations are carried out to verify the simplicity and effectiveness of the proposed control scheme.

Global output feedback stabilisation of high-order nonlinear systems with multiple time-varying delays

This paper investigates the problem of global output feedback stabilisation for a class of high-order nonlinear systems with multiple time-varying delays. By using backstepping recursive technique and the homogeneous domination approach, a continuous output feedback controller is successfully designed, and the global asymptotic stability of the resulting closed-loop system is proven with the help of an appropriate Lyapunov– Krasovskii functional. Two simulation examples are given to illustrate the effectiveness of the proposed approach.

Nonsmooth output feedback stabilization of a class of genuinely nonlinear systems in the plane

In this note, we address the problem of output feedback stabilization for a class of planar systems that are inherently nonlinear in the sense that the linearized system at the origin is neither controllable nor observable. Moreover, the uncontrollable modes contain eigenvalues on the right-half plane. By the well-known necessary condition, such planar systems cannot be stabilized, even locally by any smooth output feedback, and hence must be dealt with by nonsmooth output feedback. The main contribution of this work is the development of a non-Lipschitz continuous output feedback design method that leads to a solution to the problem. The proposed output feedback control scheme is not based on the separation principle but rather, relies on the design of a reduced-order nonlinear observer from an earlier paper with an appropriate twist, and the tool of adding a power integrator. A non-Lipschitz continuous output feedback controller is explicitly constructed, achieving global stabilization of the planar systems without imposing the high-order growth conditions required in a previous paper.