Small UAVs are susceptible to the external disturbance, especially the wind field disturbance in the atmosphere environment. As a result, UAV’s states including attitude, speed, and position are usually unable to track the desired control commands. In this paper, different types of wind fields which easily affect the UAV are summarized; furthermore, the mechanism of their wind fields affecting the UAV is first strictly analyzed. Next, a novel “reject external disturbance” flight mode for UAV is put forward to offset the trajectory deviation caused by side wind, which makes use of the wind speed information obtained by airspeed and ground speed of UAV. In order to implement the “reject external disturbance” flight mode, the Lyapunov stability theory-based variable model reference adaptive control (VMRAC) system is proposed, and it could also deal with the adverse effects of wind shear and turbulence on UAV flight. Finally, simulation results show that the proposed strategy can significantly improve the trajectory following quality of the UAV under wind disturbance.
In the future civilian UAV market, low-altitude low-speed small UAV will obtain a dominant position. In order to achieve small UAV accurate navigation, researchers have devoted lots of efforts on disturbance-model-reference controllers to reject the external wind disturbance. As we all know, accurate modeling helps the efficiency of controller’s parameters. However, almost all the design processes of disturbance-model-reference controllers are based on speed triangle theory which fails to adequately explain the effect of external wind field disturbances on UAV. First, conservation of energy and momentum theory is used to prove that the traditional speed triangle theory is unreasonable to analyze the influence of external wind field on UAV. Then, a more accurate method based on the conservation of energy and momentum theory is proposed to correctly illustrate the effect of wind disturbance on UAV. Finally, two external wind disturbance UAV flight simulation platforms based on speed triangle theory and conservation of energy and momentum theory are implemented separately, showing the big difference between these two types of methods about presenting effect of external wind field on UAV.
In this article, a new and novel robust hybrid control algorithm is designed for tuning the parameters of unmanned aerial vehicle (UAV). The quadrotor type UAV mathematical model is taken to observe the effectiveness of our designed robust hybrid control algorithm. The robust hybrid control algorithm consists of H∞ based regulation, pole-placement and tracking (RST) controller along with mixed sensitivity function is applied to control the complete model of UAV. The selected rotor craft is under-actuated, nonlinear and multivariable behavior in nature along with six degrees of freedom (DOF). Due to all these aforementioned issues its stabilization is quite difficult as compared to fully actuated systems. For the tuning of nonlinear parameters of the UAV, we designed, robust hybrid control algorithm is used. Moreover, the performance of the designed controller is compared with robust controller. The validity and effectiveness of the designed controllers are simulated in MATLAB and Simulink, in which the designed controller shows better steady state behavior, robustness and converges quickly in specific amount of time as compared to robust controller.
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