Frontier-Based Exploration for Multi-Robot Rendezvous in Communication-Restricted Unknown Environments

TL;DR

This paper adapts a standard frontier-based exploration technique to integrate exploration and rendezvous into a unified strategy, with a mechanism that allows robots to re-visit previously explored regions thus enhancing rendezvous opportunities.

Abstract

Multi-robot rendezvous and exploration are fundamental challenges in the domain of mobile robotic systems. This paper addresses multi-robot rendezvous within an initially unknown environment where communication is only possible after the rendezvous. Traditionally, exploration has been focused on rapidly mapping the environment, often leading to suboptimal rendezvous performance in later stages. We adapt a standard frontier-based exploration technique to integrate exploration and rendezvous into a unified strategy, with a mechanism that allows robots to re-visit previously explored regions thus enhancing rendezvous opportunities. We validate our approach in 3D realistic simulations using ROS, showcasing its effectiveness in achieving faster rendezvous times compared to exploration strategies.

Figures (6)

• Figure 1: Rendezvous paths of $3$ robots in an initially unknown, communication-restricted environment, using our method (Frontier-Based Rendezvous, FBR, left) and the classical frontier exploration strategy (Frontier-Based Exploration, FBE, right) in the map Ring, $3400 \text{m}^2$. Circles indicate starting positions, while crosses indicate the locations when a robot joins a cluster. When robots are in the same cluster, we indicate only the trajectory of the leader. Each robot has its own map and its own SLAM module; we use the full map of the environment for visualization purposes.
• Figure 2: The exploration trace, circled in blue, of the robot that followed the trajectory highlighted in dashed red.
• Figure 3: The oldest pose in the exploration trace is forgotten due to information decay (dashed black on the left). Frontiers in dashed red are created using our information decay method.
• Figure 4: (left) Cluster formation; (right) Two robots meet and share their exploration trace. The frontiers are numbered. The red robot's frontier (2) is deleted as it overlaps with the exploration trace of the blue robot.
• Figure 5: Rendezvous paths obtained with our method (FBR -- first row) and the baseline (FBE -- second row) in a series of environments.