Robust Control for Bidirectional Thrust Quadrotors under Instantaneously Drastic Disturbances

Quadrotors may crash and cause severe accidents under instantaneously drastic disturbances. To mitigate the effect of such disturbances, these critical issues should be considered: efficient disturbance observation and compensation, full attitude controllability, and instant output power generation of the quadrotor. In this paper, to keep the quadrotor stable even under suddenly drastic disturbances, a novel control framework is presented to by integrating the advantages of active disturbance rejection control (ADRC) as well as geometric control for a quadrotor with bidirectional thrust capabilities. Moreover, to strengthen the adaptability under significant disturbances, a novel switching strategy is introduced into the control framework by virtue of the quadrotor’s bidirectional thrust capabilities. The ADRC scheme is performed when the disturbances are within a range; alternatively, if the disturbances surpass the preset range and the desired control is beyond the ultimate output of the quadrotor, the quadrotor compliantly responds by executing a 180^circ flip reverse flight to handle such drastic disturbances. Numerical and real-world experiments demonstrate that the proposed robust control strategy has superior performance adapts to instantaneously drastic disturbances.