Research On Fault-tolerant Control Method Of Tiltable Six-rotor Unmanned Aerial Vehicle

The multi-rotor Unmanned Aerial Vehicles(multi-rotor UAVs)have simple structures and flexible control,and have been widely used in various industries.It can be equipped with relevant operating equipment for aerial photography,exploration,rescue,inspection and other tasks.With the development of related technologies and the upgrading of industries,the application scenarios of UAV are also constantly upgrading,and the requirements for autonomy and intelligence are also increasing.Performing tasks in complex scenarios needs to face strong uncertainties,and the probability of UAV failures will increase during the process of real-time interaction with the outside world.Therefore,in order to improve the reliability of multi-rotor UAVs during flight,it is of great significance to study fault diagnosis and fault-tolerant control.As the actuators at the bottom of the control command,the power units may cause the UAV to crash out of control once a failure occurs.Based on this,this paper takes the six-rotor UAV as the research object and studies the fault-tolerant control problem after the complete failure of a single rotor.After a fault occurs,the system model of the UAV will change,so it is necessary to obtain fault information in real time to adjust the control system.At the same time,the power loss of the rotor will affect the control distribution.If the moment cannot be balanced,the controllability will be lost.Aiming at this problem,this paper proposes a fault-tolerant control method for tiltable rotors.On the basis of the conventional PPNNPN six-rotor UAV,one of the rotors is designed as a tiltable structure.When flying without failure,the UAV maintains a conventional shape.Invariably,the tiltable rotor can be tilted at different angles after the complete failure of any other single rotor,and the moment balance is promoted through slight changes to the structure.Combining the characteristics of the PPNNPN configuration,the fault-tolerant control after the complete failure of any single rotor is finally realized.The main tasks of the full text are as follows:(1)The background and research significance of the topic are introduced,and the research and development status of multi-rotor UAV,fault diagnosis and fault-tolerant control are analyzed.(2)The configuration of the tiltable six-rotor UAV is designed,and the dynamics and kinematics models are established by using the Newton-Euler equation in combination with its flight principle,and the composition and function mode of the control distribution matrix are analyzed.(3)The fault diagnosis module is designed based on interactive multi-model algorithm.Through the establishment of the fault model set,the interactive filtering of each model is carried out in combination with the input and output of the control system,and the probability estimation of each model is obtained according to the real state of the system,and finally the position of the failed rotor is determined.(4)Analysis is conducted on the controllability of the six-rotor UAV following complete failure of a single rotor.An attainable moment set is constructed using linear programming method to quantify the controllability,and the optimal tilt angle is determined.Considering the characteristics of model changes and uncertainties after failure,an active disturbance rejection controller is designed for three-axis attitude and altitude control channels.Combined with the mathematical model of the tiltable six-rotor UAV,fault diagnosis algorithm,optimal tilt angle design and the basic control law,a complete fault-tolerant control scheme is developed.Finally,the fault-tolerant control method proposed in this paper is compared and analyzed through numerical simulation verification and physical flight experiments.