An autonomous swarm of micro flying robots with range-based relative localization

Accurate relative localization is an important requirement for a swarm of robots, especially when performing a cooperative task. This paper presents an autonomous multi-robot relative positioning technique. An Extended Kalman filter (EKF) uses onboard sensing of velocity, yaw rate, and height as inputs, and then estimates the relative position of other robots by fusing these quantities with ranging measurements obtained from onboard ultra wide-band (UWB). Specifically, innovations involve fast-ranging communication (333Hz for 2 robots), an automatic initialization procedure, proofs and demonstrations of consistent estimation convergence under control commands such as formation flight. Simulations concisely show the high precision, efficiency, and stability of the proposed localization method. Real-world experiments are conducted on a team of 5 Crazyflie2 quadrotors, demonstrating autonomous formation flight and coordinated flight through a window. All results indicate the effectiveness of the proposed relative positioning method for multi-robot systems. Video and code can be found at \textnormal{\url{https://shushuai3.github.io/autonomous-swarm/}}