Intermittent Information-Driven Multi-Agent Area-Restricted Search

Abstract

The problem is a two-dimensional area-restricted search for a target using a coordinated team of autonomous mobile sensing platforms (agents). Sensing is characterised by a range-dependent probability of detection, with a non-zero probability of false alarms. The context is underwater surveillance using a swarm of amphibious drones equipped with active sonars. The paper develops an intermittent information-driven search strategy, which alternates between two phases: the fast and non-receptive displacement phase (called the ballistic phase) with a slow displacement and sensing phase (called the diffusive phase). The proposed multi-agent search strategy is carried out in a decentralised manner, which means that all computations (estimation and motion control) are done locally. Coordination of agents is achieved by exchanging the data with the neighbours only, in a manner which does not require global knowledge of the communication network topology.

Keywords: autonomous search; decentralised control; infotaxis; multi-agent system.

Figure 1

A team of 13 searching agents connected with different communication networks: (a) $R_{\max }=1.1d$; and (b) $R_{\max }=2d$. d is the smallest distance between the agents. Both communication graphs are connected.

Figure 2

Illustration of the evolution of the POM over time: (a) $k=0$; (b) $k=10$; and (c) $k=38$. The multi-agent formation graph is shown in Figure 1a.

Figure 2

Illustration of the evolution of the POM over time: (a) $k=0$; (b) $k=10$; and (c) $k=38$. The multi-agent formation graph is shown in Figure 1a.

Figure 3

An illustrative run with $S=5$ agents: (a) a top-down view of the search area and agents’ paths up to $k=375$; (b) the estimated POM of agent number 1 at $k=375$ (the shades of gray indicate the value of probability); (c) entropy $H_k$ as a function of time; and (d) cardinality of the set ${\mathcal{E}}_k$ as a function of time.

Figure 4

Multi-agent formations (and their initial communication graphs) used in Monte Carlo simulations. The minimum distance $d=5$, $R_{\max }=1.4 d$.

Figure 5

Search time duration as a function of the size of formation S: the mean (red squares) and the [5,95] percentile limits.