Harmonic adaptive fault-tolerant control for incipient and multiple faults of high mobility fighter

This paper proposes a harmonic adaptive fault-tolerant control (FTC) designed to handle multiple disturbances and faults, including incipient faults, in high-mobility fighter aircraft. For an affine model with vector-engine tail-rudder inputs, a double-loop nominal nonlinear dynamic inversion (NDI) controller ensures stability under ideal conditions. Next, a simple adaptive sliding mode estimator accurately tracks disturbance amplitudes and transforms the nominal NDI into a robust adaptive control framework. A fault estimator equipped with additional adaptive laws identifies compound rudder faults-both incipient and time-varying-in the fuselage-vector engine system. Furthermore, a biologically inspired adaptive strategy, mimicking animal predation, allows the estimator to track incipient faults and suppress disturbances. Finally, the fault and disturbance estimators facilitate switching from nominal to hybrid adaptive FTC mode, enabling self-healing and stable flight. Lyapunov theory is used to prove the stability of the proposed system, and digital simulations confirm its effectiveness.