Cooperative Transportation of Cable Suspended Payloads with MAVs Using Monocular Vision and Inertial Sensing

Micro Aerial Vehicles (MAVs) have the great potential to be deployed in commercial or health care services such as e-commerce package delivery, transportation of medicines, same-day food delivery, and other time-sensitive transportation tasks. A team of MAVs can cooperatively transport objects to overcome the physical limitations of a single vehicle, while concurrently increasing the system's resilience to vehicles' failures. In this letter, we address the state estimation, control and trajectory tracking problems of cooperative transportation of cable suspended rigid body payloads with MAVs using monocular vision and inertial sensing. The key contributions are (a) a distributed vision-based coordinated control of the cable-suspended rigid body payload on SE(3), (b) a distributed estimation approach that allows each agent to estimate its cable direction and velocity independently, and (c) a new cooperative estimation scheme that can infer the payload's full 6-DoF states. This is obtained by sharing the robots' local position estimates and their relative position with respect to their corresponding attachment points on the payload. It allows to infer the payload's 6-DoF state when it is not directly measurable by each vehicle. The proposed solution runs in real-time on board and is validated through experimental results with multiple quadrotors transporting a rigid body payload via cables.