Fanglai Zhu

Synchronous switching observer for nonlinear switched systems with minimum dwell time constraint

Abstract This paper deals with the issue of state observability for a class of nonlinear switched systems under minimum dwell time (MDT) switching. First, multiple full-order switched observers are designed to estimate the states of nonlinear switched system under MDT switching, and the observer gains are derived from the feasible solutions of linear matrix inequality. Meanwhile, the condition where the minimum dwell time should satisfy is provided such that the observer error dynamic is exponentially asymptotically stable. Second, under the assumption, the output matrices of nonlinear switched system are with some special forms which can also be dealt by orthogonal procedure if they are not satisfied, multiple reduced-order switched observers are proposed by coordinate transformation approach such that the state estimation purpose is reached for original nonlinear switched systems. Third, the MDT condition that the switching signal should meet with is given such that both full-order and reduced-order switched observers can be simultaneously designed. Finally, the effectiveness of the proposed approaches is illustrated by a numerical example and longitudinal switched dynamics of an F-18 aircraft.

Simultaneous state and output disturbance estimations for a class of switched linear systems with unknown inputs

ABSTRACT The paper considers the issues of state estimation and output disturbance reconstruction for a class of switched linear systems with unknown inputs. A singular switched system is derived from the original switched system by taking the output disturbance as a part of a new extended state vector. For the constructed singular switched system, a robust sliding-mode switched observer which can not only estimate the states of original switched system but also reconstruct output disturbances is proposed, where the switching of the observer is synchronous with that of the switched system. A sufficient condition is provided to guarantee the existence of the switched observer by the feasibility of an optimisation problem with linear matrix inequality constraint, and the corresponding switching signal with average dwell time is designed such that the convergence of the estimation error system is proven to be exponential. Based on the state estimation of singular switched system, the methods of state estimation and output disturbance reconstruction of original switched system are proposed. Finally, the simulation results confirm the predicted performance of the proposed methods.

Robust impulsive reset observers of a class of switched nonlinear systems with unknown inputs

Abstract This paper is concerned with observer designs for a class of switched nonlinear systems with unknown inputs under average dwell time (ADT) switching. Firstly, for the unknown input (UI) elimination purpose, an output derivative-based method is considered. Then, in order to avoid using differentiator signals and meanwhile maintain a satisfactory estimation performance, a full-order impulsive reset switching observer is developed. The existence condition of such an observer is given via a Riccati equation. Besides, we also devote to the construction of the reduced-order observer. And furthermore, it is found that the condition under which a full-order observer exists also guarantees a reduced-order reset switching observer. Finally, a switched nonlinear electronic circuit system is used as the simulation example to verify the effectiveness of the obtained methods.

Observer-Based Synchronization of Chaotic Systems with Both Parameter Uncertainties and Channel Noise

This paper considers observer-based chaos synchronization and chaos-based secure communication problems for a class of uncertain chaotic systems with both parameter uncertainties and channel noise. First, by introducing an augmented vector, the original system is transformed into a new system which has no channel noise. Second, based on the concept of relative degree, an auxiliary drive signal vector is constructed so that the observer matching condition is satisfied. Third, a reduced-order observer is designed to estimate the states of the new augmented system. Then, a high-order high-gain sliding mode observer is considered to estimate the auxiliary drive signals and their derivatives exactly in a finite time. After this, the combination of the reduced-order observer and the high-order high-gain sliding mode observer is used as the receiver in the secure communication mechanism. And a kind of secure information recovery method is developed. Finally, a four-dimensional hyperchaos system is used as the simulation example to illustrate the effectiveness of the proposed methods.

Observer Design and Unknown Input Reconstruction for a Class of Switched Descriptor Systems

This correspondence paper is concerned with observer design problems for a class of unknown input switched descriptor systems under average dwell time switching signals. The switched descriptor system under consideration is first transformed into a general switched linear system, and then a switched reduced-order observer that can asymptotically estimate the system state without suffering the influence from the unknown inputs is developed. Besides, a high-order sliding mode observer is introduced to obtain the estimations of the output derivatives by using the system measured outputs. On the basis of estimations of the states and output derivatives, an unknown input reconstructing method is provided. Finally, two examples are presented to verify the effectiveness of the proposed approaches.