Active Hybrid Fault Tolerant Flight Control of an UAV under Control Surface Damage

Abstract

Control surface or actuator faults or failures in any flight lead to system-induced loss of control in-flight (LOCI) and the result can be fatal. In this paper, to prevent these accidents, an active fault-tolerant flight control (FTFC) is proposed. The system consists of the nonlinear control technique, state-dependent Riccati equation (SDRE) and a linear controller technique. In this paper, control surface damage is studied. To prevent LOC-I, a Reconfiguration Mechanism (RM) sends signals in real-time to the SDRE controller to slow down or accelerate the control surface movement, reconfigures controller with respect to damage or changes to Linear Quadratic Regulator/tracking (LQR/LQT) control due to uncontrollability and unobservability problem. Comparative figures are given to illustrate the effectiveness of the hybrid (SDRE/LQR-LQT+PID) controller architecture.