Robust adaptive fault detection and diagnosis observer design for a class of nonlinear systems with uncertainty and unknown time-varying internal delay

Fault estimation for nonlinear uncertain time‐delay systems based on unknown input observer

“…But in many studies, presented in the fault detection and identification filed, the delay phenomenon is not considered for nonlinear and systems ( [10][11][12][13][14][15][16][17]. Furthermore, in the few articles that have considered the delay, there are other limiting conditions such as: the linearity of the system, the occurrence of only one fault (either the sensor fault or the actuator fault), the absence of disturbances in the output or state, and the failure to consider uncertainties in the model and a particular location of time delay such as delay located only in the linear part or only in the nonlinear part, specific class of nonlinear time-delay systems [22,23,42,43]. However, in the proposed paper, a method for robust FDI is presented despite sensor and actuator faults, output and state disturbances, time delay in the linear and nonlinear parts, and uncertainty in the model, which shows the innovation and superiority of the proposed method compared to similar researches in this field.…”

Observer for Nonlinear Systems with Time-Varying Delays: Application to a Two-Degrees-of-Freedom Helicopter

“…An extended state observer for continuous and discrete systems is proposed in [15], considering that the input and the states are time-delayed. For nonlinear systems, different approaches have been presented to reconstruct the state vector of the system, making the error converge to zero if there are no uncertainties in the system or to a region close to the origin; some works on these systems are presented in [6,16,17].…”