Experiments on Collaborative Transport of Cable-suspended Payload with Quadrotor UAVs

The use of drones to transport cargo is an important application of unmanned aerial vehicles. Given the limited payload capacity of a typical small drone, the notion of utilizing multiple drones to transport heavy payloads presents a promising alternative. This article describes an easy to deploy system of multiple drones with a cable-suspended payload to enable flight testing of guidance, navigation, and control strategies for such systems in realistic operating conditions, outside of a laboratory. A unique aspect of our system is the use of Ethernet cables to ensure fast and reliable communications between vehicles. Deploying the system with a basic leader- follower guidance strategy and the PX4 flight stack for low-level control of each vehicle, we demonstrate collaborative payload transport through an extensive experimental campaign. We are able to autonomously transport payloads up to 2kg with two vehicles and up to 3kg with three off-the-shelf, 1kg vehicles. The paper also presents a brief discussion of failure cases and points to worthwhile directions for further research on this topic.