Chuanlin Zhang

Robust Control for PWM-Based DC–DC Buck Power Converters With Uncertainty Via Sampled-Data Output Feedback

This paper investigates the sampled-data output feedback control problem for dc-dc buck power converters taking consideration of components uncertainties. A reduced-order observer and a robust output feedback controller, both in the sampled-data form, have been explicitly constructed with strong robustness in the presence of uncertain parameters. A delicate stability analysis process is presented to show that, by carefully selecting the design gains and the tunable sampling period, the output voltage of the hybrid closed-loop dc-dc buck converter system will globally asymptotically tend to the desired value even though the separation principle is out of reach and the controller is only switched at the sampling points. The proposed controller consists of a set of linear difference equations which will lead to direct and easier digital implementation. Numerical simulations and experimental results are shown to illustrate the performance of the proposed control scheme.

Global smooth stabilization of a class of feedforward systems under the framework of generalized homogeneity with monotone degrees

Abstract In this paper, based on the concept of generalized homogeneity with monotone degrees (HWMD), we develop a new design procedure to explicitly construct global stabilizers for a class of feedforward systems. The proposed controller design strategy has several new features. First, a series of positive constant gains instead of function gains are employed for a simpler controller construction. Second, the flexibility of HWMD provides a general framework to unify several existing results. Third, it is now possible to design continuously differentiable stabilizers for some feedforward systems, for which only continuous stabilizers were previously designed. Moreover, for feedforward systems with decreasing powers, the proposed approach will enable us to design a locally linear saturation control law which is easier to be implemented in practical applications.

Global decentralised stabilisation for a class of uncertain large-scale feedforward nonlinear systems

In this paper, the problem of global decentralised stabilisation for a class of uncertain large-scale feedforward nonlinear systems is investigated. The system under consideration is allowed to contain unknown non-Lipschitz continuous nonlinear terms. The design of the global decentralised controllers takes a two steps procedure. First of all, based on the adding a power integrator technique and the homogeneous domination approach a local homogeneous decentralised controller is proposed for each subsystem of the large-scale feedforward nonlinear system. Then, we integrate a series of nested saturation functions with the homogeneous decentralised controllers and adjust the saturation levels to ensure globally asymptotic stability of the closed-loop system. Simulation studies are conducted to illustrate the effectiveness of the proposed control method.

Global decentralized control of interconnected nonlinear systems by sampled-data output feedback

This paper studies the problem of global decentralized control for a class of large-scale interconnected uncertain systems using sampled-data output feedback. First, a sampled-data high-gain observer is constructed separately for each subsystem, and an explicit formula of the control law is designed by utilizing the output feedback domination approach. It is shown that by carefully selecting the observer gains and the sampling period, the closed-loop system can be rendered globally asymptotically stable only using decentralized output feedback controller in the discrete-time form.

Global stabilisation for a class of uncertain non-linear systems: a novel non-recursive design framework

AbstractIn this paper, a novel global non-recursive stabilisation design framework is addressed for a class of inherent non-linear systems with the presence of system uncertainties and external nonvanishing disturbances. By virtue of the facility that the weighted homogeneity brings into the system synthesis procedure, a non-recursive design method is proposed to yield a globally effectiveness robust controller with its expression following a quasi-linear manner. By proceeding with a rigorous non-recursive stability analysis framework, which covers both global asymptotical and finite-time convergence cases, the common recursively treated derivative items in backstepping-based methods are totally avoided. Inspired by the homogeneous domination technique, a scaling gain performed as a bandwidth factor is introduced into the original system and hence the robustness of the controlled system can be adjusted to meet the practical performance requirements. A numerical example and its control performance simulati...

Semi-global sampled-data output feedback disturbance rejection control for a class of uncertain nonlinear systems

ABSTRACT This paper investigates the semi-global output feedback disturbance rejection control problem for a class of uncertain nonlinear systems with additive disturbances using linear sampled-data control. Aiming to reject the adverse effects caused by the uncertainties and unknown nonlinear perturbations which may not satisfy the strict feedback or feedforward structure, a new generalised discrete-time extended state observer is proposed to estimate the disturbance at sampling points. An output feedback disturbance rejection control law is then constructed in a sampled-data form which facilitates digital implementations. By selecting adequate control gains and a sufficiently small sampling period to restrain the state growth under a zero-order-hold input, the semi-global asymptotic stability of the hybrid closed-loop system and the disturbance rejection ability are proved. Both numerical example and an application of a single-link robot arm system demonstrate the feasibility and efficacy of the proposed method.

Global decentralised stabilisation for a class of uncertain large-scale high-order upper-triangular nonlinear systems

ABSTRACT This paper considers the global decentralised stabilisation problem for a class of uncertain large-scale high-order upper-triangular nonlinear systems. First, a local linear decentralised controller is recursively constructed based on the generalised homogeneous system theory and the adding a power integrator method. Second, aiming for global stabilisation, a series of nested saturation functions are integrated with the proposed local linear decentralised controller. Then, it is proved that the obtained decentralised saturated controller will render the whole closed-loop system globally asymptotically stable. Due to the flexibility of the generalised homogeneous method, the proposed control approach not only weakens the existing restrictions imposed on the interconnected nonlinearities, but also can be applied to a more general class of upper-triangular nonlinear systems. Furthermore, two simulations examples are conducted to show the effectiveness of the proposed control scheme.

Finite-Time Output Feedback Control for PWM-Based DC–DC Buck Power Converters of Current Sensorless Mode

This paper investigates the finite-time output feedback control problem for dc–dc buck switched power converters of the current sensorless mode. A finite-time state-feedback controller is first built by using a recursive design method, and then a novel reduced-order observer, rather than the conventional full-order observer, is derived to estimate the unmeasurable state of the dc–dc buck system with a finite-time convergence rate. The output feedback control law built by combining the state-feedback control law and the measured system state from the observer is proved to be effective with an explicit stability analysis. Compared with the asymptotic stability control method, not only a faster convergence rate around the equilibrium is obtained but also a better suppression ability against resistance, inductance, and input voltage variation can be achieved for the closed-loop system. Moreover, the sensorless control strategy will be more reliable and cost reducible than its state-feedback control counter-case. Simulations and experimental comparison results verify the effectiveness of the proposed control method.

A homogeneous active disturbance attenuation methodology for a perturbed chain of power integrators

Abstract The problem of global active disturbance attenuation control for a class of perturbed chain of power integrators is investigated in this paper. A homogeneous design method is developed by integrating the homogeneous system theory with a nonlinear disturbance observation/compensation procedure. With a novel recursive design approach, the mismatched disturbances are compensated in a step-by-step way while the nominal system can be feedback controlled by nested virtual controllers. A rigorous homogeneous stability analysis assures the effectiveness of the proposed strategy. A numerical simulation and an application to an under-actuated mechanical system affirm the control performances.

Global decentralized stabilization for a class of large-scale feedforward nonlinear systems

This paper considers the problem of global decentralized stabilization for a class of large-scale feedforward nonlinear systems. First, by using generalized homogeneous systems theory, a local linear decentralized control law is recursively constructed. Second, a series of nested saturation functions are integrated with the proposed local linear control law to render the whole closed-loop large-scale system global asymptotical stability. Due to the flexibility of the generalized homogeneous systems theory, the proposed approach not only weakens the existing restrictions imposed on the interconnected nonlinearities, but also can be applied to more general classes of large-scale feedforward nonlinear systems. Numerical example shows that the effectiveness of the proposed control scheme.