Research On Fault Tolerant Control Of Quadrotor Aircraft Based On Predictive Control

The quadrotor aircraft is a kind of multirotor aircraft with simple structure,easy maneuverability,autonomous hovering and capabilities of vertical take-off and landing.It is widely used in military and civilian fields.However,due to the characteristics of the quadrotor system,such as strong coupling and mathematical model uncertainty,the quadroror is extremely sensitive to external disturbances and prone to failure.Therefore,the fault-tolerant control problem of the quadrotor has become a research hotspot in recent years.In this thesis,the fault-tolerant control method is studied for the single quadrotor system and the quadrotor formation system with multiple actuator faults.Based on the model predictive control,three different fault-tolerant control algorithms are proposed and designed.The main contents and innovations of this thesis are as follows:Firstly,the structure and flight principle of the quadrotor are described.The mathematical model of the quadrotor is analyzed and established.According to it,the spatial position equation and three attitude angle equations are obtained.In addition,the system composition and experimental process of the quadrotor fault-tolerant control experimental simulation platform are briefly introduced.Secondly,an improved predictive fault-tolerant control method based on sliding mode observer is proposed for the single quadrotor system with partial loss of effectiveness faults of actuators and uncertainty of model parameters.The observation model is constructed and a discrete sliding mode observer with good robustness is designed to estimate multi-actuator faults.An augmented state model with embedded integrator is established,and an improved predictive control algorithm is designed,which makes the quadrotor system still stable and has good control performance under the actuators faults.The effectiveness of the proposed fault-tolerant control method is verified by experimental simulation.Thirdly,a min-max robust predictive fault-tolerant control method based on linear matrix inequality is proposed for the quadrotor time-delay uncertain system with partial loss of effectiveness faults of actuators and input and output constraints.The polytopic method is used to describe the uncertainty of the system,and the augmented model with output error is established.The min-max robust predictive fault-tolerant control algorithm is designed.Input and output constraints are added to the optimization problem of the performance index.The scale factor of the fault model and time-delay memory control are added to the state feedback control.The optimal control law is obtained to ensure the stability of the system by using Lyapunov stability theory and linear matrix inequality method to transform the "min-max" optimization problem into the target minimization problem.Simulation experiments verify the rationality and feasibility of the method.Finally,a distributed predictive fault-tolerant control method is proposed for quadrotor formation system,considering the actual collision avoidance requirements,state and input constraints,and actuator faults.The objective cost function and prediction model are designed for each quadrotor respectively,and the rolling optimization is implemented synchronously.Considering the state information exchange between quadrotors,the collision avoidance problem is transformed into the constraint of each quadrotor.At the same time,considering the actuator faults,state and input constraints,the terminal components are improved to ensure the fault-tolerant stability of the entire formation system.The effectiveness of the method is demonstrated by comparative simulation experiments.