Xing-Gang Yan

Brief paper: Nonlinear robust fault reconstruction and estimation using a sliding mode observer

This paper considers fault detection and estimation issues for a class of nonlinear systems with uncertainty, using an equivalent output error injection approach. A particular design of sliding mode observer is presented for which the parameters can be obtained using LMI techniques. A fault estimation approach is presented to estimate the fault and the estimation error is dependent on the bounds on the uncertainty. For a special class of uncertainty, a fault reconstruction scheme is presented where the reconstructed signal can approximate the fault signal to any accuracy. The proposed fault estimation/reconstruction signals are only based on the available plant input/ouput information and can be calculated on-line. Finally, a simulation study on a robotic arm system is presented to show the effectiveness of the scheme.

Dynamic Sliding Mode Control for a Class of Systems with Mismatched Uncertainty

In this paper, a robust stabilization problem for a class of uncertain systems is studied using sliding mode techniques. Matched and mismatched uncertainties are both considered. By employing the sliding surface proposed by Edwards and Spurgeon in [Int J Control 1995; 62(5): 1129–1144], the stability of the sliding mode is shown first. Then, an asymptotic observer is established to estimate the system state variable based on a constrained Lyapunov equation, and a variable structure controller is proposed to stabilize the system by exploiting the estimated state and system output. The two major limitations in [IEEE Trans Autom Control 1996; 41(11): 1691–1693] are eliminated. Finally, a simulation study based on a simplified model of the HIRM aircraft system is used to illustrate the effectiveness of the results.

Decentralised robust sliding mode control for a class of nonlinear interconnected systems by static output feedback

In this paper, a class of nonlinear interconnected systems with nonlinear nominal subsystems is considered. Matched and mismatched uncertainties are both dealt with. Based on sliding mode techniques, a decentralised robust control scheme, using only output information, is presented to stabilise the system locally, but under certain circumstances, global results can be obtained. The approach allows a more general structure for the interconnections and uncertainty bounds than other literature in this area. The conservatism in the results is reduced by fully using system output information and the uncertainty bounds. A numerical example is used to demonstrate the efficacy of the method.

Adaptive Sliding-Mode-Observer-Based Fault Reconstruction for Nonlinear Systems With Parametric Uncertainties

In this paper, a class of nonlinear systems with uncertain parameters is considered. A novel adaptive law is designed to identify unknown parameters under the assumption that the time derivative of some of the outputs is measurable. Then, a sliding-mode observer is proposed to estimate the system state variables. By using the inherent features of sliding-mode observers, a fault-reconstruction scheme is proposed which can be implemented online. The proposed reconstruction signal can approximate the fault signal to any required accuracy even in the presence of uncertain parameters. A simulation example for a magnetic-levitation system is given to illustrate the feasibility and effectiveness of the proposed scheme.

Robust decentralized actuator fault detection and estimation for large-scale systems using a sliding mode observer

In this paper, robust decentralized actuator fault detection and estimation is considered for a class of non-linear large-scale systems. A sliding mode observer is proposed together with an appropriate coordinate transformation to find the sliding mode dynamics. Then, based on the features of the observer, a decentralized fault estimation strategy is proposed using an equivalent output error injection, and a decentralized reconstruction scheme follows by further exploiting the structure of the uncertainty which is allowed to have non-linear bounds. The estimation and reconstruction signals only depend on the available measured information and thus the proposed strategy can work on-line. The theoretical results which have been obtained are applied to an automated highway system. Simulation shows the feasibility and effectiveness of the proposed scheme.

Decentralized output feedback robust stabilization for a class of nonlinear interconnected systems with similarity

In this paper, the problem of decentralized output feedback stabilization for a class of nonlinear uncertain interconnected systems with similar subsystems is considered, and a type of controller with holographic structure is developed. It is shown that both the analyses of systems and the design of controllers are simplified by a similar structure. Finally, an example is presented to illustrate the results given in this paper and an estimation of the associated stabilized domain. Simulation shows that our method is very effective.

On the Solvability of the Constrained Lyapunov Problem

This paper considers system theoretic conditions for the solvability of the so-called constrained Lyapunov problem for non-square systems. These problems commonly appear in the control systems literature. Both a static output feedback problem and an observer problem are considered. The basis for the work described here is a new canonical form which simplifies the analysis and deals with the equality constraint in a simple way

Brief paper: Sliding mode control for time-varying delayed systems based on a reduced-order observer

In this paper, a stabilisation problem for a class of nonlinear systems is considered, where both the nonlinear term and the nonlinear uncertainty are mismatched and subject to time-varying delay. Under the assumption that the delay is known, a reduced-order observer is designed using an appropriate transformation. A sliding surface is proposed in an augmented space formed by the system outputs and the estimated states. The sliding mode dynamics are derived using an equivalent control approach, and the Lyapunov-Razumikhin approach is exploited to analyse the stability of the sliding motion. Then, a sliding mode control law is developed such that the system can be driven to the sliding surface in finite time. A simulation example shows the effectiveness of the proposed approach.

Technical Communique: Decentralized Output Feedback Robust Control for Nonlinear Large-scale Systems

In this note, the problem of decentralized output feedback robust stabilization is studied for time-varying nonlinear large-scale systems, in which general interconnection and fully nonlinear nominal subsystems are both considered. The uncertainties dealt with in this note may be not only matched but also unmatched, and they may appear not only in interconnection but also in isolated subsystem. Then, a kind of continuous decentralized output feedback control to stabilize the system is proposed. Finally, simulation shows the effectiveness of our result.

State and Parameter Estimation for Nonlinear Delay Systems Using Sliding Mode Techniques

In this technical note, a class of time varying delay nonlinear systems is considered where both parametric uncertainty and structural uncertainty are involved. The uncertain parameters are embedded in the system nonlinearly. The bound on the structural uncertainty takes nonlinear form and is time delayed. A sliding mode observer is proposed to estimate the system state and an adaptive law is proposed to estimate the unknown parameters simultaneously. Using the Lyapunov-Razuminkhin approach, sufficient conditions are developed such that the error system is uniformly ultimately bounded. A simulation on a bioreactor system shows the effectiveness of the approach.