Flight Control Reconfiguration in Oscillatory Failure Case Scenarios

Abstract

A fault detection system together with a flight control reconfiguration algorithm is proposed to tackle the problem of oscillatory failure case scenarios in hydraulically actuated flight control loops. The fault detection system employs a set of residual filters designed using a model-based approach via command-input decoupling and free assignment of the filter dynamics via dynamic inversion. As underlying design model, an optimized, multi-model hydraulic actuator approximation covering the actuator dynamics together with stochastically distributed, uncertain parameters is derived. A flight control reconfiguration algorithm is presented which smoothly transitions the control law from its normal configuration to the alternate law after detection of a fault. The performance of the transition is analyzed using advanced linear time-varying analysis methods based on an extension of the well-known Bounded Real Lemma. The achieved detection and reconfiguration performance is verified via non-linear simulations.