Cooperative Transportation of UAVs Without Inter-UAV Communication
This work addresses the problem of enabling UAVs to transport payloads cooperatively in dynamic environments without communication, which is incremental as it builds on leader-follower systems but adds communication-free operation and real-time adaptability.
The paper tackles cooperative transportation of UAVs without inter-UAV communication, developing a leader-follower system with real-time trajectory modification and force estimation via UKFs, achieving asymptotic tracking in simulations and real-world experiments with errors affected by airflow disturbances.
A leader-follower system is developed for cooperative transportation. To the best of our knowledge, this is the first work that inter-UAV communication is not required and the reference trajectory of the payload can be modified in real time, so that it can be applied to a dynamically changing environment. To track the modified reference trajectory in real time under the communication-free condition, the leader-follower system is considered as a nonholonomic system in which a controller is developed for the leader to achieve asymptotic tracking of the payload. To eliminate the need to install force sensors, UKFs (unscented Kalman filters) are developed to estimate the forces applied by the leader and follower. Stability analysis is conducted to prove the tracking error of the closed-loop system. Simulation results demonstrate the good performance of the tracking controller. The experiments show the controllers of the leader and the follower can work in the real world, but the tracking errors were affected by the disturbance of airflow in a restricted space.