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Robust fault-tolerant flight path angle control

Dinesh D. Dhadekar (Defence Institute of Advanced Technology, Pune, India)
Ajay Misra (Defence Institute of Advanced Technology, Pune, India)
S.E. Talole (Research and Development Establishment (Engineers), Pune, India)

Aircraft Engineering and Aerospace Technology

ISSN: 0002-2667

Article publication date: 9 August 2021

Issue publication date: 6 September 2021




The purpose of the paper is to design a nonlinear dynamic inversion (NDI) based robust fault-tolerant control (FTC) for aircraft longitudinal dynamics subject to system nonlinearities, aerodynamic parametric variations, external wind disturbances and fault/failure in actuator.


An uncertainty and disturbance estimator (UDE) technique is used to provide estimate of total disturbance enabling its rejection and thereby achieving robustness to the proposed NDI controller. As needed in the NDI design, the successive derivatives of the output are obtained through an UDE robustified observer making the design implementable. Further, a control allocation scheme consigns control command from primary actuator to the secondary one in the event of fault/failure in the primary actuator.


The robustness is achieved against the perturbations mentioned above in the presence of actuator fault/failure.

Practical implications

Lyapunov analysis proves practical stability of the controller–observer structure. The efficacy and superiority of the proposed design has been demonstrated through Monte-Carlo simulation.


Unlike in many FTC designs, robustness is provided against system nonlinearities, aerodynamic parametric variations, external wind disturbances and sinusoidal input disturbance using a single control law which caters for fault-free, as well as faulty actuator scenario.



Dhadekar, D.D., Misra, A. and Talole, S.E. (2021), "Robust fault-tolerant flight path angle control", Aircraft Engineering and Aerospace Technology, Vol. 93 No. 7, pp. 1171-1182.



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