Abstract
ABSTRACTIn this paper, in order to reduce the influence on quadrotor flight from different external disturbances, a novel nonlinear robust controller is designed and used in the quadrotor system. At first, a nonlinear dynamic model of the quadrotor is formulated mathematically. Then, a quadrotor flight controller is designed with the method of classical backstepping control (CBC) and the nonlinear system using this controller is proved to be asymptotically stabilized by the Lyapunov stability theory when there is no external disturbance. At last, a new nonlinear robust controller established by the introduction of both the saturation function and the integral of error into CBC is designed and named as saturation integral backstepping control (SIBC). The boundedness of the nonlinear system under external disturbances is verified by the uniformly ultimately bounded theorem of the nonvanishing perturbation. The numerical simulations of hovering and trajectory tracking are carried out using MATLAB/SIMULINK taking the external disturbances into consideration. In addition, a series of outdoor flight experiments were completed on the actual experimental equipments of quadrotor UAV under the time-varying disturbance from wind. According to the simulation and flight experiment results, the proposed SIBC strategy shows a superior robustness than CBC and integral backstepping control (IBC) strategy.
Highlights
As a new kind of small unmanned aerial vehicle (UAV), quadrotor aircraft has been widely concerned and used in military surveillance, rescue, disaster monitoring, photography and agricultural mapping due to its many advantages such as flight by high maneuverability and agility, hovering, vertical take-off and landing, etc. [1,2,3]
In order to solve the quadrotor UAV control problem, many new control methods have been proposed by researchers, for example, linear and adaptive proportional–integral–derivative (PID) control [7], fuzzy integral sliding mode control [8], feedback linearization control [9,10], integral predictive/ nonlinear H∞ control [6], adaptive dynamic feedbacklinearization control [11], sliding mode reconfigurable control [12], sliding mode control driven by sliding mode disturbance observer [13], linear matrix inequality (LMI) based robust quadrotor control [14], and robust adaptive attitude tracking control [15,16]
In order to illustrate the effectiveness of the proposed saturation integral backstepping control (SIBC) strategy, a series of trajectory tracking experiments of quadrotor UAV under the random disturbance from wind outdoors are presented
Summary
As a new kind of small unmanned aerial vehicle (UAV), quadrotor aircraft has been widely concerned and used in military surveillance, rescue, disaster monitoring, photography and agricultural mapping due to its many advantages such as flight by high maneuverability and agility, hovering, vertical take-off and landing, etc. [1,2,3]. A control strategy with excellent disturbance restraining capability is urgently required to achieve autonomous flight such as hovering, trajectory tracking, take-off and landing [6]. In order to reduce the influence of these disturbances to the quadrotor flight (such as hovering and trajectory tracking), a novel saturation integral backstepping control (SIBC) has been proposed by combining saturation function and integral of error with the CBC. Simulation and flight experiment results indicate that compared with CBC and integral backstepping control (IBC), SIBC strategy shows higher anti-disturbance capacity to the three disturbances in hovering and trajectory tracking respectively.
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