Improved Intermediate Estimator-Based Fault Tolerant Control for HFVs With Heterogeneous Actuators

This study proposes a compound fault-tolerant control for re-entry hypersonic flight vehicles (HFVs) equipped with heterogeneous actuators in the presence of unknown disturbances, sensor faults, and aerodynamic surface constraints. The pitch rate sensor faults and external disturbances are estimated by an improved intermediate estimator (IIE), and then can update a sliding mode controller (SMC). Through a quadratic programming method to optimize the virtual control torque calculated by the adaptive law and super-twisting reaching law, the aerodynamic surfaces (AS) can achieve optimal deflections under rudder limits. Employing a fuzzy optimization algorithm with Aquila Optimizer (AO), reaction control systems (RCS) can compensate for the insufficient control torque produced by AS owing to the low dynamic pressure in the re-entry phase of HFVs. Comparative simulation results demonstrate that the proposed scheme can restore the accurate track of the desired attitude. Note to Practitioners—Compared to the conventional flight vehicles, the HFVs have some salient characteristics such as high nonlinearity, strong coupling, and complex uncertainty, which bring great challenges to their flight controller designs. Among these challenges, the sensor faults and external disturbances may trigger inaccurate attitude tracking of the HFVs and the aerodynamic surface constraints would let the actuators cannot produce enough supporting control torque. To address these problems, this study introduces a compound fault-tolerant control strategy designed for re-entry HFVs with heterogeneous actuators. An intermediate estimator is designed to handle the pitch sensor faults and external disturbances simultaneously, where the estimation information is compensated in a sliding mode controller updated by adaptive law and super-twisting reaching law. By separately designing the control allocation scheme to distribute torque to the heterogeneous actuators, RCS can offset the negative effect where AS cannot provide the sufficient control torque because of the low dynamic pressure in the re-entry phase. The simulation results show that the proposed scheme achieves satisfactory attitude accuracy.