Cooperative transportation using small quadrotors using monocular vision and inertial sensing

Micro aerial vehicles have the potential to assist humans in tasks such as manipulation and transportation for construction and humanitarian missions, beyond simply acquiring data and building maps. In this letter, we address the state estimation, control, and trajectory planning in cooperative transportation of structures, which are either too heavy or too big to be carried by small microvehicles. Specifically, we consider small quadrotors, each equipped only with a single camera and inertial measurement unit as a sensor. The key contributions are 1) a new approach to coordinated control, which allows independent control of each vehicle while guaranteeing the system's stability and 2) a new cooperative localization scheme that allows each vehicle to benefit from measurements acquired by other vehicles. The latter relies on the vehicles exploiting the inherent rigid structure information to infer additional constraints between the vehicles' poses allowing us to formulate the pose estimation problem as an optimization problem on the Lie group SE(3). The proposed approach is validated through experimental results with multiple quadrotors grasping and transporting a rigid structure.