Robust Residual Generator Design for Sensor Fault Detection in Twin Rotor Aerodynamic System

Abstract

The twin rotor aerodynamic system (TRAS) reflects the dynamics of vertical take-off rotor systems. Controlling such systems for reference tracking and stabilization is difficult due to the nonlinear nature of the system and the significant cross-coupling between the main and tail rotor inputs and outputs. The TRAS considers the coupling effect and gyroscopic disturbance torque as unwanted signals. For TRAS safe and reliable operation, proper control input is vital along with fast fault indication. This paper addresses the problem of a robust residual generator design to detect the output sensor fault in the linear model of TRAS subjected to \({l}_{2}\)-norm bounded disturbance. For fault detection (FD) purposes, a robust observer is proposed using a co-inner-outer factorization approach to maximize the sensitivity/robustness criterion. Observer-based residual generator design is formulated as H-/H∞ optimization problem and a solution is obtained by solving the Riccati equation. The factorization technique overcomes the computational cost and minimizes H∞ norm which guarantees observer stability and robust performance. Furthermore, a linear quadratic regulator-based state feedback controller is proposed to meet the system's desired transient response requirement. The controller and residual generator designs' effectiveness are validated through MATLAB simulations. Successful fault detection in the output sensor of TRAS depicts the good performance of the proposed observer.