Prescribed-time extended state observer and prescribed performance control of quadrotor UAVs against actuator faults

The detection and accommodation of actuator faults in control systems have received considerable attention. However, the existing fault-tolerant control techniques typically require complex and computationally intensive algorithms, and the settling time cannot be pre-assigned offline, which limits the practical applicability of these techniques. To address these problems, this paper proposes a prescribed-time fault-tolerant tracking control scheme for accommodating actuator failures in quadrotor unmanned aerial vehicles. First, a prescribed-time nominal controller is developed to precisely track the desired position in the absence of actuator faults. Subsequently, an extended state observer is developed to precisely estimate the uncertainties derived from actuator failures. Using the estimated values, a prescribed-time tracking control scheme is designed for the position subsystem, based on the prescribed performance control technique. In addition to having a simple structure, the proposed controller relaxes the limits that both the settling time and desired transient- and steady-state performances cannot be pre-assigned. Similarly, an observer-based prescribed-time tracking control scheme is established for the attitude subsystem under actuator failures. Numerical simulations are performed to validate the effectiveness and robustness of the proposed control method.