Research Of Robust And Fault Tolerant Control System For A Quadrotor

Quadrotor aircraft is widely used in aerial photography,reconnaissance and other fields due to their good handling performance.However,developing the control system of such a typical underdriven,strongly coupled,and time-varying nonlinear system with operation lag is a challenging task.In order to stabilize the quadrotor aircraft during the disturbances and rotor failures,a passive fault-tolerant flight control system based on explicit model predictive control(EMPC)is proposed in this paper.This paper first summarizes the research status and development prospects of quadrotor aircraft.Secondly,the mechanical structure and flight principle of the quadrotor aircraft are analyzed,and the newton-euler equation method is used to establish the nonlinear mathematical model of the quadrotor aircraft,including attitude model,horizontal position model and height model.Then,the nonlinear model of quadrotor aircraft is decoupled into three linear submodels by small perturbation linearization method,which lays a foundation for the controller design.Meanwhile,the actuator fault model of quadrotor aircraft is analyzed and established.In terms of the study of optimal control problem of quadrotor aircraft under constrained conditions,this paper designs the robust control system of quadrotor aircraft based on model predictive control algorithm.Traditional predictive control needs online optimization,so it has a large amount of calculation.But the EMPC introduced in this paper will be offline optimization,and online control only needs to find the appropriate control area to obtain the control quantity by simple calculation.Therefore,the EMPC algorithm is very suitable for implementation in the embedded system.In this paper,the attitude controller,horizontal position controller and height controller are designed on the basis of three linear models established in the chapter 2.Compared with the traditional PID controller,the above three controllers based on EMPC have the advantages of fast response and small overshoot in simulation experiments.In order to ensure that the quadrotor aircraft can still keep stable flight when actuator failure occurs in real condition,this paper designs the fault-tolerant control system based on the robust control system designed in the chapter 3 and the time-delay control(TDC).The TDC is used to eliminate the influence of faults on the system through one-step state iteration.Simulation results show that the designed robust and fault-tolerant controller has good control performance in suppressing external disturbances and fault tolerant control of the actuator.Finally,Simulink and Gazebo joint simulation is used to prove the availability of the algorithm.