A cooperative obstacle avoidance control scheme for multi-quadrotor UAV formation: a hierarchical control approach

In this work, a hierarchical distributed control scheme is proposed to address the cooperative formation and obstacle avoidance problem faced during the application of multi-quadrotor unmanned aerial vehicle (UAV) systems. The distributed control design is decoupled into a two-layer structure consisting of an upper layer for reference signal generation and a lower layer for tracking control. In the upper layer, an adaptive repulsive gain mechanism is introduced into the repulsive force. Based on the adaptive artificial potential field (AAPF) method, an obstacle avoidance trajectory is generated for the virtual leader and it is incorporated into a distributed reference signal generator, which subsequently produces the required reference signals for UAV formation obstacle avoidance. In the lower layer, tracking controllers integrated with an extended state observer (ESO) are designed for multi-quadrotor UAVs. Lyapunov-based stability analysis demonstrates the exponential convergence of the upper-layer error signals and the boundedness of the lower-layer error signals. Finally, the experimental results validate the effectiveness of the proposed control scheme.