Flying in Narrow Spaces: Prioritizing Safety With Disturbance-Aware Control

Safe and autonomous flight of quadrotors in enclosed environments still remains formidable challenge due to the aerodynamic proximity effect and restricted free space. This letter develops an integrated planning and control architecture for disturbance-aware and safety control of quadrotors. By explicitly considering ground effect in both the controller and obstacle avoidance constraints, the proposed method can fully leverage the benefits brought by aerodynamic disturbance. Specifically, a Ground Effect Observer (GEO) is designed to estimate repulsive force based on the ground effect model. Subsequently, building upon the augmented quadrotor model, a Nonlinear Model Predictive Controller (NMPC) is developed to enhance tracking performance while conserving energy during flight. Moreover, aided by the Exponential Control Barrier Functions (ECBFs), the distance-based safety constraints can be mapped onto the constraints of control inputs. This facilitates the consideration of disturbance on safety constraints, allowing quadrotors to avoid obstacles promptly. Experimental evaluation employs two types of tunnels to assess the applicability of the proposed scheme. Comparative results show that the proposed scheme outperforms several popular methods in safety and reliability.