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BodyGuards: Escorting by Multiple Robots in Unknown Environment under Limited Communication

Zhuoli Tian, Yanze Bao, Meng Guo

Abstract

Multi-robot systems are increasingly deployed in high-risk missions such as reconnaissance, disaster response, and subterranean operations. Protecting a human operator while navigating unknown and adversarial environments remains a critical challenge, especially when the communication among the operator and robots is restricted. Unlike existing collaborative exploration methods that aim for complete coverage, this work focuses on task-oriented exploration to minimize the navigation time of the operator to reach its goal while ensuring safety under adversarial threats. A novel escorting framework BodyGuards, is proposed to explicitly integrate seamlessly collaborative exploration, inter-robot-operator communication and escorting. The framework consists of three core components: (I) a dynamic movement strategy for the operator that maintains a local map with risk zones for proactive path planning; (II) a dual-mode robotic strategy combining frontier based exploration with optimized return events to balance exploration, threat detection, and intermittent communication; and (III) multi-robot coordination protocols that jointly plan exploration and information sharing for efficient escorting. Extensive human-in-the-loop simulations and hardware experiments demonstrate that the method significantly reduces operator risk and mission time, outperforming baselines in adversarial and constrained environments.

BodyGuards: Escorting by Multiple Robots in Unknown Environment under Limited Communication

Abstract

Multi-robot systems are increasingly deployed in high-risk missions such as reconnaissance, disaster response, and subterranean operations. Protecting a human operator while navigating unknown and adversarial environments remains a critical challenge, especially when the communication among the operator and robots is restricted. Unlike existing collaborative exploration methods that aim for complete coverage, this work focuses on task-oriented exploration to minimize the navigation time of the operator to reach its goal while ensuring safety under adversarial threats. A novel escorting framework BodyGuards, is proposed to explicitly integrate seamlessly collaborative exploration, inter-robot-operator communication and escorting. The framework consists of three core components: (I) a dynamic movement strategy for the operator that maintains a local map with risk zones for proactive path planning; (II) a dual-mode robotic strategy combining frontier based exploration with optimized return events to balance exploration, threat detection, and intermittent communication; and (III) multi-robot coordination protocols that jointly plan exploration and information sharing for efficient escorting. Extensive human-in-the-loop simulations and hardware experiments demonstrate that the method significantly reduces operator risk and mission time, outperforming baselines in adversarial and constrained environments.
Paper Structure (29 sections, 16 equations, 11 figures, 1 table, 1 algorithm)

This paper contains 29 sections, 16 equations, 11 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. Related Work
  3. Our Method
  4. Problem Description
  5. Robots and Operator in Workspace
  6. Escorting Task with Adversarial Regions
  7. Problem Statement
  8. Proposed Solution
  9. Dynamic Motion Strategy for the Operator
  10. Potential Risk Zones
  11. Dynamic Update of Operator Map for Safety
  12. Choice of Temporary Goal
  13. Dual-mode Robot Strategy
  14. Frontier-based Exploration
  15. Optimization of Return Events
  16. ...and 14 more sections

Figures (11)

  • Figure 1: Top: Snapshots from hardware experiments showing 2 UGVs escorting the operator within unknown environment under communication constraints, where the robots switch between exploration and communication relay to minimize the operator travel time to destination while ensuring safety; Bottom: The task-oriented explored map and potential risk regions are provided to the operator as guidance.
  • Figure 2: Each robot and the operator is equipped with a communication module to exchange information with each other, and the signal strength changes as they move within the workspace.
  • Figure 3: Left: With potential adversaries within unknown space, the operator may have risks when reaching the frontiers; Right: when the proposed Potential Risk Zones (in blue) is enforced, the operator remains safe.
  • Figure 4: The operator dynamically refines its local map by excluding the potential risk zones $\mathcal{Z}_\texttt{h}(t)$ and the known risk regions $\mathcal{D}_\texttt{h}(t)$, and then selects a temporary goal $\widehat{p}_\texttt{g}(t)$ on the refined map to move towards.
  • Figure 5: Left: The proposed ring communication topology among multiple robots (filled circles) and the operator (filled star); Right: the communication events along the time axis.
  • ...and 6 more figures

Theorems & Definitions (3)

  • Definition 1: Risk Region
  • Definition 2: Potential Risk Zones
  • Definition 3: Estimated-Via-Distance