Semi-global Output Feedback Stabilization Research Articles

Linear output-feedback-based semi-global stabilization for switched nonlinear time-delay systems

This paper focuses on the problem of semi-global output-feedback stabilization for a class of switched nonlinear time-delay systems in strict-feedback form. A switched state observer is first constructed, then switched linear output-feedback controllers for individual subsystems are designed. By skillfully constructing multiple Lyapunov–Krasovskii functionals and successfully solving several troublesome obstacles, such as time-varying delay and switching signals and nonlinearity in the design procedure, the switched linear output-feedback controllers designed can render the resulting closed-loop switched system semi-globally stabilizable under a class of switching signals with average dwell time. Furthermore, under some milder conditions on nonlinearities, the semi-global output-feedback stabilization problem for switched nonlinear time-delay systems is also studied. Simulation studies on two examples, which include a continuous stirred tank reactor, are carried out to demonstrate the effectiveness of the proposed approach.

Semi-global output feedback nonlinear stabilization of variable speed grid connected direct drive wind turbine generator systems

The goal of the present work is to achieve nonlinear semi-global output feedback stabilization of variable speed grid connected direct drive wind turbine generator DDWTG systems under wind energy conversion systems to provide the electricity demand for electrical networks. The study will address the sensorless control of variable speed wind energy generation systems, namely optimized rotor speed and direct-axis current control to determine the most appropriate structure and to improve both robustness and reliability of this kind of distributed generators. The proposed nonlinear observer is robust with respect to measurements error and perturbations of the sampling schedule. The simulation results of the case study support the presented main theorem that reflects the effect of measurement errors and the improvement with respect to global convergence properties. The novelty of the present study resides in taking into account the difficulties and control problem complexity that faced the nonlinear output feedback control undergo: (i) the proposed system nonlinearity and loss the observability of sensorless PMSG near the singularity point of the rotor speed; (ii) inaccessibility measurements for all system state variables; (iii) maximum power point tracking of optimum reference angular rotor speed; (IV) magnetizing and demagnetizing direct-axis current at standstill; (V) the proposed semi-global observer has dynamic high-gain design parameter DHGO. The simulation results of variable speed grid connected DDWTG, in general, confirm the main theorem developed under DHGO parameter and lead us to enlarge and prolongation the admissible sampling period using nonlinear Lyapunov stability control techniques.

SEMIGLOBAL OUTPUT-FEEDBACK STABILIZATION FOR A CLASS OF FEEDFORWARD NONLINEAR SYSTEMS

This paper considers the semiglobal output-feedback stabilization for a class of feedforward nonlinear systems.Notably,the systems under investigation possess unmeasurable states dependent growth including linear and higher-order parts,which incorporate and extend those in the existing many literature.Based on a linear lower-gain observer,a linear output feedback controller is constructed by outputfeedback domination approach,which is structurally simple and easy to implement.By appropriately choosing the design parameter,it can be guaranteed that the zero solution of resulting closed-loop system is locally exponentially stable,and by starting from the given compact set containing the origin,all the solutions of the closed-loop system converge to the origin.A numerical example is provided to illustrate the effectiveness of the theoretical results.

Semi-global output feedback stabilization for a class of nonlinear systems using homogeneous domination approach

This paper investigates the problem of semi-global stabilization by output feedback for a class of nonlinear systems using homogeneous domination approach. For each subsystem, we first design an output feedback stabilizer for the nominal system without the perturbing nonlinearities. Then, based on the ideas of the homogeneous systems theory and the adding a power integrator technique, a series of homogeneous output feedback stabilizers are constructed recursively for each subsystem and the closed-loop system is rendered semi-globally asymptotically stable. The efficiency of the output feedback stabilizers is demonstrated by a simulation example.

Semi-Global Output Feedback Stabilization for a Class of Uncertain Nonlinear Systems

This paper addresses the problem of semi-global stabilization by output feedback for a class of nonlinear systems whose output gains are unknown. For each subsystem, we first design a state compensator and use the compensator states to construct a control law to stabilize the nominal linear system without the perturbing nonlinearities. Then, combining the output feedback domination approach with block-backstepping scheme, a series of homogeneous output feedback controllers are constructed recursively for each subsystem and the closed-loop system is rendered semi-globally asymptotically stable.

Semiglobal Output Feedback Stabilization of a Generalized Class of MIMO Nonlinear Systems

This paper considers the problem of semiglobal stabilization by output feedback for a class of generalized multi-input and multi-output uncertain nonlinear systems. Due to the presence of mismatched uncertainties and the lack of triangularity condition, the systems under consideration are not uniformly completely observable. Combining the output feedback domination approach and block-backstepping scheme together, a series of linear output feedback controllers are constructed recursively for each subsystems and the closed-loop system is rendered semiglobally asymptotically stable.

Asymptotic Rejection of Disturbances in Non-Minimum Phase Nonlinear Systems

We address the problem of semi-global output-feedback stabilization for a class of nonlinear non-minimum phase systems subject to sinusoidal disturbances of known frequency, but unknown amplitude and phase. To this aim, we employ, within an internal model-based control scheme, an extension of a stabilization method recently introduced by Isidori. We regard this result as a first step towards a more complete theory of output regulation in the large for non-minimum phase systems.

Tools for Semiglobal Stabilization by Partial State and Output Feedback

We develop tools for uniform semiglobal stabilization by partial state and output feedback. We show, by means of examples, that these tools are useful for solving a variety of problems. One application is a general result on semiglobal output feedback stabilizability when global state feedback stabilizability is achievable by a control function that is uniformly completely observable. We provide more general results on semiglobal output feedback stabilization as well. Globally minimum phase input--output linearizable systems are considered as a special case. Throughout our discussion we demonstrate the usefulness of considering local convergence separate from boundedness of solutions. For the former we employ a sufficient small gain condition guaranteeing convergence. For the latter we rely on Lyapunov techniques.