Guarding a Translating Line with an Attached Defender

TL;DR

This paper analyzes a differential game where a defender attached to a moving target aims to intercept an attacker, deriving strategies and barriers that determine winning regions, with simulations validating the theoretical findings.

Contribution

It introduces a novel target-guarding game with an attached defender, deriving equilibrium strategies and the barrier surface for the first time.

Findings

Derived equilibrium strategies for the defender and attacker.

Identified the barrier surface separating winning regions.

Validated theoretical results with simulations.

Abstract

In this paper we consider a Target-guarding differential game where the Defender must protect a linearly moving line segment by intercepting the Attacker who tries to reach it. In contrast to common Target-guarding problems, we assume that the Defender is attached to the Target and moves along with it. This assumption affects the Defender's maximum speed depending on its heading direction. A zero-sum differential game of degree for the Attacker-winning scenario is studied, where the payoff is defined to be the distance between the two agents at the time of reaching the Target. We derive the equilibrium strategies and the Value function by leveraging the solution for the infinite-length Target scenario. The zero-level set of this Value function provides the barrier surface that divides the state space into Defender-winning and Attacker-winning regions. We present simulation results at the end to demonstrate the theoretical results.