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In this paper, the problem of adaptive fixed-time 6 degree-of-freedom (DOF) tracking control for spacecraft non-cooperative rendezvous in presence of the parameter uncertainties and external disturbances is investigated. Firstly, a new multilayer fixed-time sliding mode surface (MFSMS) is designed, and the setting time of the proposed surface can be estimated without the knowledge of the initial conditions...
This paper considers the control problem for a class of nonlinear uncertain systems with output delay. The methods of the predictive active disturbance rejection control (ADRC) are employed to achieve desired performance against external disturbance, unknown nonlinear dynamics and output delay. The comparison between two typical predictive ADRCs, i.e., Predictor Observer based ADRC and Smith Predictor...
In this paper, the problem of robust H∞ tracking control for 6 DOF spacecraft formation flying in the presence of parameter uncertainties, external disturbances and input saturation is addressed. Firstly, a robust H∞ controller constructed by the solution of the Hamilton-Jacobi-Inequality(HJI) is proposed. It is proved that the coupled 6 DOF tracking error system is stable and robust in respect to...
This paper considers the control problem for a class of sensor delay systems with nonlinear unknown dynamics and external disturbances. The extended state predictor observer (ESPO) based active disturbance rejection control (ADRC) is first proposed to timely estimate and compensate for the "total disturbance" under sensor delay. The timedomain stability of the closed-loop system is rigorously...
In this paper, the problem on robust H∞ control for 6-DOF spacecraft formation flying in the presence of parameter uncertainties and external disturbances is addressed. Firstly, the model of coupled translation and rotation motion of spacecraft formation is established. Subsequently, a robust H∞ controller is proposed, which is constructed by the solution to the Hamilton-Jacobi-Inequality (HJI). It...
This paper studies the ability of ADRC for systems with unobservable and unmatched uncertainty. First the definition of observability for a class of uncertain nonlinear systems is given and an observability condition is proposed. Then the paper discusses how to transform the unobservable and unmatched uncertainty into the total disturbance, which is both observable and matched, so that the ability...
Active disturbance rejection control (ADRC), as proposed by Prof. Jingqing Han, reduces first the plant dynamics to its canonical form, normally in the form of cascade integrators, for which the standard controller can be employed to meet the design specifications. This paper concerns with the selection of the canonical form for non-minimum phase systems. In particular, it is shown that, by employing...
The paper considers the tracking problem for a class of uncertain linear time invariant (LTI) systems with both uncertain parameters and external disturbances. The active disturbance rejection tracking controller is designed and the resulting closed-loop system׳s characteristics are comprehensively studied. In the time-domain, it is proven that the output of closed-loop system can approach its ideal...
An overview of the active disturbance rejection control (ADRC) is presented in this talk. Ever since ADRC was proposed by Jingqing Han in 1990s[1]1, it has become quite an attractive methodology to applied researchers, even though rigorous theoretical justification was lagging behind for quite some time. The fact that ADRC possesses certain uniqueness in concepts, simplicity in engineering implementation,...
A novel sub-optimal control algorithm based on fuzzy logic system (FLS) to design continuous sliding mode control (CSMC) for uncertain nonlinear systems is presented. By means of combining a fuzzy logic system into sliding mode control, continuous sliding mode control (SMC) can be designed on the derivative of the control signal. The realization of the controller is easier and more convenient than...
The capabilities of extended state observer (ESO) for estimating uncertainties is discussed in this paper. The scope of the disturbances that can be observed by LESO with bounded observing errors is given. The observing errors for several typical disturbances-constant disturbance, sine disturbance, ramp disturbance, and square wave disturbance are further analyzed. It is demonstrated that ESO can...
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