High-gain Sliding Mode Observer Research Articles

A novel fault reconstruction and estimation approach for a class of systems subject to actuator and sensor faults under relaxed assumptions

In this paper, we propose a new fault reconstruction and estimation (FRE) scheme for a class of nonlinear systems subject to both actuator and sensor faults, under relaxed assumptions. Indeed, in our approach, we assume that the total number of actuator and sensor faults is greater than the number of outputs, we consider a more relaxed rank matching condition and we relax the classical minimum phase assumption, which enlarges considerably the class of systems and applications for which our approach may be addressed compared to existing methods in the literature. After augmenting the system by the dynamics of filtered outputs, we generate auxiliary outputs until the observer matching condition with respect to actuator faults vector becomes satisfied. Next, a new high gain sliding mode observer is designed for the system of auxiliary outputs to estimate both auxiliary states and sensor faults. The estimates of auxiliary outputs and sensor faults are then used by an unknown input observer (UIO) whose the objective is to reconstruct the states of the considered nonlinear system. Finally, we show that we can reconstruct the actuator faults by exploiting the dynamics of auxiliary outputs and using the estimates of system states and sensor faults. Theoretical results are established based on Lyapunov analysis and sliding modes theory. Numerical simulations are applied to a single link robot system and a steer-by-wire vehicle under disturbances and noise to validate theoretical results and to illustrate the good performances of the proposed fault reconstruction and estimation scheme.

Mixed Kalman-Fuzzy Sliding Mode State Observer in Disturbance Rejection Control of a Vibrating Smart Structure

In the controllers that are synthesized on a nominal model of a nonlinear plant, the parametric matched uncertainties and nonlinear/unmodelled dynamics of the high order nature can significantly affect the performance of the closed-loop system. On this note, owing to the robust characteristic of the sliding mode observer against modelling perturbations, measurement noise, and unknown disturbances and due to the non-fragile behaviour of the Kalman filter against process noise, a mixed Kalman sliding mode state-observer is proposed and later enhanced by the addition of an intelligent fuzzy agent. In light of the proposed technique, the chattering phenomena and the conservative boundary neighboring layer of the high gain sliding mode observer are addressed. Then, a robust active disturbance rejection controller is developed by using the static feedback of the estimated states using a~direct Lyapunov quadratic stability theorem. The reduced order plant for control design purposes is subjected to some simulated square-integrable disturbances and is assumed to have mismatched uncertainties in the system matrices. Finally, the robust performance of the closed-loop scheme with respect to the mentioned perturbation signals and modelling imperfections is tested by implementing the control system on a mechanical vibrating smart cantilever beam.

Associated observer-based synchronization for uncertain chaotic systems subject to channel noise and chaos-based secure communication

This paper attempts to discuss the issues of chaotic synchronization and chaos-based secure communication for uncertain chaotic systems subject to channel noise. An augmented drive system used to deal with channel noise is constructed by introducing a new auxiliary drive variable. Then, an augmented auxiliary drive signal is constructed in order to breakthrough the observer rank condition. Based on a kind of nonsingular transformation for the state and output of augmented auxiliary drive system, a reduced-order observer is designed to asymptotically estimate the states of the augmented auxiliary drive system, and a high-gain sliding-mode observer is considered to estimate the augmented auxiliary drive signal and its derivative. An information signal recovery method that can not only recover the information signal but also reconstruct both uncertain parameter disturbance and channel noise is developed. Finally, a numerical simulation example is given to evaluate the performance of the proposed scheme.

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.

Sliding-mode observers for nonlinear systems with unknown inputs and measurement noise

This paper deals with the design of observers for Lipschitz nonlinear systems with not only unknown inputs but also measurement noise when the observer matching condition is not satisfied. First, an augmented vector is introduced to construct an augmented system, and an auxiliary output vector is constructed such that the observer matching condition is satisfied and then a high-gain sliding mode observer is considered to get the exact estimates of both the auxiliary outputs and their derivatives in a finite time. Second, for nonlinear system with both unknown inputs and measurement noise, an adaptive robust sliding mode observer is developed to asymptotically estimate the system’s states, and then an unknown input and measurement noise reconstruction method is proposed. Finally, a numerical simulation example is given to illustrate the effectiveness of the proposed methods.

Fault detection and isolation design for uncertain nonlinear systems based on full-order, reduced-order and high-order high-gain sliding-mode observers

This paper considers the observer-based fault detection and isolation design problems when the observer matching condition is not satisfied. Based on the relative degree concept, an auxiliary output vector that may satisfy the observer matching condition is constructed. Since the auxiliary output vector contains unknown information, we use a high-order high-gain sliding-mode observer to exactly estimate not only the auxiliary outputs, but also their derivatives in a finite time. Then, an adaptive robust full-order observer is developed to serve as an actuator fault detection observer. For the actuator fault reconstruction purpose, a reduced-order observer is proposed to estimate the system states even if there are some actuator faults and an actuator fault reconstruction method is provided to reach the fault isolation purpose. A numerical simulation example is used to illustrate the effectiveness of the proposed methods.

The Combination of High-Gain Sliding Mode Observers Used as Receivers in Secure Communication

This paper considers chaos synchronization and chaos-based secure communication problems based on high-gain sliding mode unknown input observers when the observer matching condition is not satisfied to the drive signal. An auxiliary drive signal vector which satisfies the observer matching condition is introduced and an adaptive and robust observer is developed by using the auxiliary drive signal directly to not only estimate the states but also adjust adaptively the unknown parameters and the Lipschitz constants of the nonlinear terms. A high-gain sliding mode observer is considered to exactly estimate both the auxiliary drive signals and their derivatives in a finite time only based on the original drive signal. The combination of the adaptive and robust observer and the high-gain sliding mode observer becomes the receiver in chaos-based secure communication discussion. A kind of information signal recovering method is developed based on both the state synchronization and exact estimates of the derivatives of the auxiliary drive signals. Finally, a numerical simulation example is given to illustrate the effectiveness of the proposed methods.