The residuals from EKFs are used by fault diagnosis algorithm to assign a conditional probability to each failure condition, and fault type can be diagnosed according to the probabilities. Then, EKF observers are introduced to estimate the state vector and to calculate residual sequences caused by different faulty actuators.

This paper is structured as follows: first, the structure and model of tilt-rotor UAV actuator are established.

The fault diagnosis algorithm of MMAE could assign a conditional probability to each faulty actuator according to the residual of EKF and diagnose the fault. The actuator deflections are added to the state vector and estimated using EKF. In this paper, an actuator fault detection and diagnosis (FDD) method based on the extended Kalman filter (EKF) and multiple-model adaptive estimation (MMAE) is proposed. Therefore, there is an urgent need of fault detection and diagnosis method for the actuators.

However, due to the limitation of weight and cost, small UAVs cannot be equipped with redundant actuators. As being the executor of the flight control, the actuator failure will directly affect the controllability of the tilt-rotor UAV, and it has high probability of causing fatal personal injury and financial loss. To the best of our knowledge, this work is the first study of the tiltrotor VTOL's fault-tolerance that exploits the configuration redundancy.Flight safety is of vital importance for tilt-rotor unmanned aerial vehicles (UAVs), which can take off and land vertically as well as cruise at high speed, especially in different kinds of complex environment. Extensive experiments are performed to validate that the system can maintain the controlled flight under different actuator failures. The proposed approach is lightweight and is implemented as an extension to an already existing flight control stack. Then, we analyze the feasible wrench space the vehicle can generate and design the dynamic control allocation so that the system can adapt to actuator failure, benefiting from the configuration redundancy. We discuss the design and model of a custom tiltrotor VTOL UAV, which is a combination of a fixed-wing aircraft and a quadrotor with tilting rotors, where the four propellers can be rotated individually. This work introduces tolerance to several types of actuator failures in a tiltrotor VTOL aircraft. However, a less explored area is the study of their potential fault tolerance due to their inherent redundancy, which allows them to sustain some degree of actuator failure. Prior work on these aircraft has addressed the aerodynamic performance, design, modeling, and control. Tiltrotor vertical take-off and landing (VTOL) unmanned aerial vehicles (UAVs) are a better choice than fixed-wing and multirotor aircraft for such applications. Providing both the vertical take-off and landing capabilities and the ability to fly long distances to aircraft opens the door to a wide range of new real-world aircraft applications while improving many existing applications.

Tilt rotor flight control system