Finite time observer based incremental nonlinear fault-tolerant flight control

Abstract

This paper investigates incremental nonlinear control approaches for aircraft attitude control considering external disturbances, nonlinear model uncertainties, actuator faults and measurement errors of angular accelerations and control inputs. The incremental model for incremental nonlinear control law design is reformulated and a novel finite time disturbance observer (FTESO) based incremental backstepping (IBKS) control strategy is proposed to further improve the robustness and fault accommodation capability of the standard IBKS controller. The advanced disturbance observer is adopted to actively estimate and compensate the synthetic uncertainties of the reformulated incremental model while retaining the advantage of the standard IBKS controller that not requiring the exact knowledge of aircraft dynamics. The state variables of the closed-loop system are proved to be semi-globally uniformly ultimately bounded (SGUUB). The effectiveness of the FTESO based IBKS controller is validated by aircraft command tracking simulation studies in the presence of sudden system disturbance, actuator faults and measurement errors of angular accelerations. In addition, the control framework of the FTESO based IBKS controller can also be utilized to improve other incremental nonlinear controllers with proper disturbance observers.