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A robust fault tolerant control (FTC) approach is addressed for a class of nonlinear systems with
time delay, actuator faults, and multiple disturbances. The first part of the multiple disturbances is supposed to be an
uncertain modeled disturbance and the second one represents a norm-bounded variable. First, a composite observer
is designed to estimate the uncertain modeled disturbance and actuator fault simultaneously. Then, an FTC strategy
consisting of disturbance observer based control (DOBC), fault accommodation, and a mixed

To reduce the influence of model uncertainties and system disturbances, there are several control approaches focusing on nonlinear systems with unknown disturbances (see the survey paper [

In order to increase the reliability and safety of practical engineering, the issues of fault diagnosis and fault tolerant control (FTC) have become an attractive topic and have been paid much attention in recent years (see [

In this paper, FTC problem is discussed for a class of time-delay systems with actuator fault and multiple disturbances. The first part of multiple disturbances is modeled disturbance formulated by an exogenous system and the second one is norm bounded uncertain variable. A composite observer is designed to estimate the modeled disturbance and time-varying fault. Then, an FTC scheme is addressed with disturbance rejection and attenuation performance by combining fault accommodation and DOBC with a robust

In this paper, we consider the following nonlinear system with time-varying faults, time-delay, and multiple disturbances simultaneously:

For a known matrix

The following assumptions are required so that the considered problem can be well-posed in this paper.

In practical engineering, the exogenous model (

In order to reject the modeled external disturbance, disturbance observer should be designed in this subsection. In this paper, we only consider the case of available states. The disturbance observer is formulated as

By defining

In the following subsection, we will construct a fault diagnosis observer with disturbance estimation so that the modeled disturbance can be rejected and fault can be diagnosed.

The following fault diagnosis observer is constructed to diagnose the time-varying actuator fault:

The fault estimation error system yields

In the next subsection, a composite fault tolerant controller should be determined for reconfiguring the systems with disturbance rejection and attenuation performance.

In this section, the object is to construct a control approach to guarantee that the system (

From Assumption

Then, it can be concluded that

Combing estimation error equations (

For constants

The

Compared with [

At this stage, the objective is to find

If for the parameter

Consider the following Lyapunov function:

It is verified that

In the absence of

From (

From the first, second, third, fourth, and seventh columns and rows of the left matrix in inequality (

Defining

It follows that (

Following the definition of the

In the presence of

Denote

It can be seen by using Schur complement formula that (

In this section, we consider the longitudinal dynamics of A4D aircraft at a flight condition of 15000 ft altitude and 0.9 Mach given in [

It is supposed that

The initial values of the states are supposed to be

For

When the disturbance observer is constructed based on (

Disturbances estimation error in disturbance observer.

Bias fault, its estimation, and error.

The responses of state variable.

Ramp fault, its estimation, and error.

In this paper, a robust antidisturbance fault tolerant control problem is investigated for nonlinear time delay systems with faults and multiple disturbances. There are the following features of the proposed algorithm compared with the previous results. First, the multiple disturbances and state time-delay are considered simultaneously in this paper. Second, an FTC scheme is addressed with disturbance rejection and attenuation performance by combining fault accommodation and DOBC with a mixed

This work is partially supported by the National Natural Science Foundation of China (Grant no. 61203195), Universities Natural Science Foundation of Jiangsu Province (Grant no. 12KJB510033), and China Postdoctoral Science Foundation (Grant no. 2013M530508).