Finite-time Formation Tracking Control Of Quadrotor Aircrafts

The quadrotor aircraft as one of the important branches in the field of UAV is widely applied in commercial,aerospace,military and scientific research fields in virtue of unique advantages of simple structure,compact fuselage,strong maneuverability.Compared with the limitations of single quadrotor in practical application,multiple quadrotors are adopted for forming formation to perform missions with coordination and cooperation which is the mainstream trend.Therefore,the formation tracking control technique of multiple quadrotors with high accuracy has gradually attracted the attentions of scholars both here and abroad’.Quadrotor aircraft is a complicated under-actuated system with the characters of strong coupling,nonlinear time-varying and static instability.Traditional control schemes which only depend on system model cannot meet the requirements of modern control performance.Therefore,the influential factors which contain external disturbances and model uncertainties are considered in the mathematic models.Meanwhile,the finite time disturbance observer and the control schemes with finite time convergence effect are applied in designing high precision and strong robust formation tracking control schemes.Firstly,a back-stepping sliding mode formation tracking control scheme based terminal sliding mode disturbance observer is adopted in this section for achieving trajectory tracking control effect of quadrotor formation.This method combines traditional back-stepping technique with finite time sliding mode technique,so that finite time convergence character and better control effects can be obtained.Meantime,the terminal sliding mode disturbance observer can effectively estimate disturbance term and compensate it in real time,thus the negative effects brought by disturbance term can be weaken further.The effect of finite time stability in the system can be proved in view of Lyapunov theory.The simulation experiments demonstrate the feasibility of proposed control scheme.Secondly,for the sake of improving steady state accuracy and attenuating chattering phenomenon,a nonsingular terminal sliding mode formation tracking control scheme based finite time extended state observer is adopted in this section.The controller is designed by constructing a nonsingular terminal sliding surface and combining with the super twisting reaching law,which can not only avoid singular problem,but also improve the steady-state accuracy of the system and suppress the chattering phenomenon effectively.Then,the finite time extended state observer is used for accurately observing external disturbances.The simulation experiments demonstrate the effectiveness of proposed control scheme.Finally,in order to further enhance the performance of finite time convergence,a composite finite time formation tracking control scheme based continuous finite time disturbance observer is put forward in this section.The whole system is firstly divided into position subsystem and attitude subsystem.A back-stepping control scheme based barrier Lyapunov function is adopted for position subsystem and a fast integral terminal sliding mode control scheme is applied in attitude subsystem.For one thing,finite time stable of the system can be realized based on proposed control scheme,and for another,faster convergence speed and stronger robust can also be obtained in virtue of the control scheme mentioned above.Meantime,the continuous finite time disturbance observer is embedded in the configuration of control system and anti-interference ability is enhanced effectively in the system.The high accuracy tracking control effect of quadrotor formation can be realized ultimately.The simulation experiments demonstrate the superiority of proposed control scheme.