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To guarantee the collision avoidance of the quadrotor unmanned aerial vehicles (QUAVs) with limited network resources and external disturbances in a complex environment, a distributed event-triggered (ET) collision avoidance formation controller is proposed in this article. To improve the robustness of the QUAVs, the parameter adaptive method (PAM) is used to tackle the influence of the external disturbance. The virtual tube (VT) is designed individually for each QUAV to avoid the collision between the QUAVs. As long as the distances between the VTs are greater than the minimum safe distance for the QUAVs, and no QUAV exceeds the boundary of the corresponding VT, the collision will not occur. Furthermore, to restrict the QUAV in the corresponding VT, the fuzzy artificial potential field with coefficients adjusted by predicting the future position of the QUAV by using both the relative position and velocity, is established and distributed around the boundary of the VT. Thus, the QUAVs are restricted to the VT and the collisions are avoided. Then, the distributed ET collision avoidance formation controller is designed by the VT and the PAM. A dynamic ET mechanism is presented to release the network load, the triggered frequency being heavily related to the distance between the position of the QUAV and the boundary of the VT. Furthermore, the closed-loop system boundedness has been certified by the Lyapunov theory. Finally, comparative flight experiments are performed to verify the effectiveness and the superiority of the proposed controller.

In this paper, a distributed Event-Triggered (ET) collision avoidance coordinated control for Quadrotor Unmanned Aerial Vehicles (QUAVs) is proposed based on Virtual Tubes (VTs) with flexible boundaries in the presence of unknown external disturbances. Firstly, VTs are constructed for each QUAV, and the QUAV is restricted into the corresponding VT by the artificial potential field, which is distributed around the boundary of the VT. Thus, the collisions between QUAVs are avoided. Besides, the boundaries of the VTs are flexible by the modification signals, which are generated by the self-regulating auxiliary systems, to make the repulsive force smaller and give more buffer space for QUAVs without collision. Then, a novel ET mechanism is designed by introducing the concept of prediction to the traditional fixed threshold ET mechanism. Furthermore, a disturbance observer is proposed to deal with the adverse effects of the unknown external disturbance. On this basis, a distributed ET collision avoidance coordinated controller is proposed. Then, the proposed controller is quantized by the hysteresis uniform quantizer and then sent to the actuator only at the ET instants. The boundedness of the closed-loop signals is verified by the Lyapunov method. Finally, simulation and experimental results are performed to demonstrate the superiority of the proposed control method.