Tethered Multi-Robot System for Improved Path Planning and Exploration

This paper presents a tethered unmanned aerial vehicle (UAV) and unmanned ground vehicle (UGV) for improved path planning and exploration in the presence of tall objects. The aim was to develop a UGV capable of mapping, planning a path, and exploring in a cluttered, unseen environment. Due to the low height of most UGVs, a tethered UAV was added to enable it to look over obstacles and improve its navigation and exploration algorithms. Having a tethered system avoids having the UAV perform complex algorithms like path planning and mapping, with simple altitude controllers serving the purpose of an elevated view point for the rover. This allows for off the shelf UAVs to be used. This paper describes the entire system, from a custom-built UGV in the form of an RHex-style robot, to four point tether system, and the modifications made to an off-the-shelf UAV. Additionally, the software architecture, as well as the communication between the different systems was discussed in detail, particularly focusing on when the UAV should be deployed. The approach taken to integrate the UAV within the UGV was carefully designed to be platform independent allowing for more versatility in application. The platform was tested in an unknown environment with tall obstacles, herein the UGV was tested both with and without using the drone. The results showed an overall improvement in three key metrics, namely, reductions in both the time taken (−22%) and power consumption (-27%) required to locate and reach a set goal, and increased path-tracking accuracy (+38%).