Enforcing Network Connectivity in Robot Team Missions

Abstract

The growing interest in robot teams for surveillance or rescue missions entails new technological challenges. Robots have to move to complete their tasks while maintaining communication among themselves and with their human operators, in many cases without the aid of a communication infrastructure. Guaranteeing connectivity enables robots to explicitly exchange information needed in collaborative task execution, and allows operators to monitor or manually control any robot at all times. Network paths should be multi-hop, so as not to unnecessarily restrict the team's range. In this work we contribute a complete system which integrates three research aspects, usually studied separately, to achieve these characteristics: a multi-robot cooperative motion control technique based on a virtual spring-damper model which prevents communication network splits, a task allocation algorithm that takes advantage of network link information in order to ensure autonomous mission completion, and a network layer which works over wireless 802.11 devices, capable of sustaining hard real-time traffic and changing topologies. Link quality among peers is the key metric used to cooperatively move the robots and maintain uninterrupted connectivity, and the basis for novel ideas presented in each subsystem. Simulations and experimental results with real robots are presented and discussed.KEY WORDS-cooperative navigation, link-quality-based communication, multi-robot task allocation, networked robot systems.

Dynamic Mission Planning for Communication Control in Multiple Unmanned Aircraft Teams

“…In this problem, the system consists of a multi-agent team with a set of objectives and similar to motion planning problems discussed in Sect. Authors in [42] discuss a task allocation based network control mechanism. A centralized task allocation planner initializes by dividing the team of robots into subset clusters.…”

“…Furthermore, agent roles are generally predefined and fixed during the mission. Several studies have investigated task allocation for communication control, but the methods presented had centralized architectures [42] and treated network requirements as a constraint to task allocation rather than assigning agents cooperatively to achieve better results [18]. In addition, many studies in the literature assume simplistic communication requirements and deterministic environments which break down in real world operations.…”

Multi-robot path planning with maintenance of generalized connectivity

“…For many practically relevant applications, one of the fundamental properties to be respected is graph connectivity. Connectivity is for example needed in order to let each robot communicate to a base station through multi-hops, or to ensure the convergence of several distributed computation and formation control methods [10] [11]. Graph theory provides a simple and accurate framework to describe the connectivity of a group of robots.…”

Robotic Router Formation in Realistic Communication Environments

“…While the Fiedler eigenvalue is one measure of graph connectivity, it is rather a high-level measure, i.e., it does not measure the communication reception quality. In [9], a spring-damper model is adopted to enforce the connectivity of a robotic operation, in an outdoor environment. A spring-damper model, on the other hand, still requires designing a function that translates the link quality to proper forces.…”