Active and passive fault tolerant control allocation strategy for nonlinear systems

Abstract

This article introduced fault-tolerant control (FTC) schemes for over-actuated affine non-linear uncertain systems. The proposed methodologies incorporate two different control allocation (CA) units with high-level nonlinear adaptive sliding mode control (NLASMC) strategy. The first FTC strategy is active that utilizes an online CA unit to effectively manage the redundant actuators towards the chosen flight path in faulty conditions. On the other hand, the second FTC scheme is passive based on the idea of a fixed CA scheme and does not require control-input reconfiguration during the faulty condition. A robust NLASMC law is selected to enforce the state trajectories converges to the sliding manifold despite the uncertainty in the model dynamics and external disturbance effect. The proposed schemes are then applied to the nonlinear F16 aircraft detailed model equipped with thrust vectoring (TV) control. The nonlinear simulations on 6-degree-of-freedom (6-DOF) F16 aircraft are performed under the failure of the aileron, rudder, and elevator. It can be visualized that both schemes performed well, but online CA scheme can cope with more faults and failures combinations in comparison to fixed CA schemes. Furthermore, both FTC approaches performed well when compared to existing methods in the literature.