Junyong Zhai

Finite-time stabilization for a class of stochastic nonlinear systems via output feedback.

This paper investigates the problem of global finite-time stabilization in probability for a class of stochastic nonlinear systems. The drift and diffusion terms satisfy lower-triangular or upper-triangular homogeneous growth conditions. By adding one power integrator technique, an output feedback controller is first designed for the nominal system without perturbing nonlinearities. Based on homogeneous domination approach and stochastic finite-time stability theorem, it is proved that the solution of the closed-loop system will converge to the origin in finite time and stay at the origin thereafter with probability one. Two simulation examples are presented to illustrate the effectiveness of the proposed design procedure.

Global adaptive output feedback control for a class of nonlinear time-delay systems

This paper addresses the problem of global output feedback control for a class of nonlinear time-delay systems. The nonlinearities are dominated by a triangular form satisfying linear growth condition in the unmeasurable states with an unknown growth rate. With a change of coordinates, a linear-like controller is constructed, which avoids the repeated derivatives of the nonlinearities depending on the observer states and the dynamic gain in backstepping approach and therefore, simplifies the design procedure. Using the idea of universal control, we explicitly construct a universal-type adaptive output feedback controller which globally regulates all the states of the nonlinear time-delay systems.

Global finite-time output feedback stabilisation for a class of uncertain nontriangular nonlinear systems

This article addresses the problem of global finite-time output feedback stabilisation for a class of nonlinear systems in nontriangular form with an unknown output function. Since the output function is not precisely known, traditional observers based on the output is not implementable. We first design a state observer and use the observer states to construct a controller to globally stabilise the nominal system without the perturbing nonlinearities. Then, we apply the homogeneous domination approach to design a scaled homogeneous observer and controller with an appropriate choice of gain to render the nonlinear system globally finite-time stable.

Global output feedback control for a class of high-order feedforward nonlinear systems with input delay

This paper investigates the problem of output feedback stabilization for a class of high-order feedforward nonlinear systems with time-varying input delay. First, a scaling gain is introduced into the system under a set of coordinate transformations. Then, the authors construct an observer and controller to make the nominal system globally asymptotically stable. Based on homogeneous domination approach and Lyapunov-Krasovskii functional, it is shown that the closed-loop system can be rendered globally asymptotically stable by the scaling gain. Finally, two simulation examples are provided to illustrate the effectiveness of the proposed scheme.

Universal adaptive regulation for a class of nonlinear systems with unknown time delays and output function via output feedback

Abstract This paper investigates the adaptive output feedback control problem for a class of nonlinear systems with unknown time delays and output function. The system satisfies linear growth condition with an unknown growth rate. First of all, based on a dynamic gain scaling technique, we present a new dynamic high-gain observer without requiring precise information of the output function. Then, by employing the idea of universal control and the backstepping method, a universal adaptive output feedback control law is designed to globally regulate all the states of the system. A simulation example is presented to illustrate the effectiveness of the proposed design scheme.

Finite-Time Output Feedback Stabilization for Stochastic High-Order Nonlinear Systems

This paper investigates the problem of global finite-time output feedback stabilization in probability for a class of stochastic high-order nonlinear systems. The drift and diffusion terms satisfy the homogeneous growth conditions. Based on the stochastic Lyapunov theorem and the adding one power integrator technique, a homogeneous observer and controller are constructed for the nominal system. Then, a scaling gain is introduced into the homogenous observer and controller to render the closed-loop system to be globally finite-time stable in probability. Two examples are given to illustrate the effectiveness of the proposed design scheme.

Finite-time state-feedback control for a class of stochastic high-order nonlinear systems

This paper discusses the problem of global finite-time stabilization in probability for a class of stochastic high-order nonlinear systems whose drift and diffusion terms satisfy lower-triangular growth conditions. By adopting adding one power integrator technique and constructing twice continuous differential Lyapunov functions, a continuous state-feedback controller is recursively designed. Based on stochastic finite-time stability theorem, it is proved that the solution of the closed-loop system is finite-time stable in probability. Several simulation examples are given to illustrate the effectiveness of the proposed design procedure.

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.

Disturbance observer-based robust control for trajectory tracking of wheeled mobile robots

This paper proposes an adaptive controller for the trajectory tracking of a nonholonomic wheeled mobile robot with nonholonomic constraints in the presence of external disturbances and unknown parameters. A new scheme is proposed to design an adaptive virtual velocity controller and torque control law. Meanwhile, a disturbance observer is applied to estimate the lumped disturbance to achieve the feedforward compensation. Simulation results demonstrate the effectiveness of the proposed control scheme.

Global practical tracking for a class of uncertain nonlinear systems via sampled-data control

This paper investigates the problem of global practical tracking via sampled-data output feedback for a class of uncertain nonlinear systems whose output functions are not precisely known. To solve the problem, we first construct a new sampled-data compensator and then use the backstepping and output feedback domination approach to design a linear sampled-data controller. An explicit formula for the sampling period is computed to regulate the tracking error under the proposed controller with appropriate gains. A practical example is given to illustrate the effectiveness of the proposed scheme.