A Survey on Multi-Robot Coordination in Electromagnetic Adversarial Environment: Challenges and Techniques

Abstract

Wireless communications and networking are playing an important role in coordination and cooperation of multi-robot systems (MRS). However, it is challenging to keep a reliable and stable wireless connection in practical applications. Especially, robots acting in electromagnetic adversarial (EA) environments may encounter more serious situations including scarce spectrum, active interference, adversarial competition, etc. In this survey, we firstly analyze the challenges faced by MRS in EA environments, and provide a categorization according to the ''sense-decide-act'' robot control procedure. Secondly, enabling techniques for each challenge are introduced. Finally, typical robotics software architectures are introduced, as frameworks for efficient arrangement of the above mentioned enabling techniques.

Robotic Ad-hoc Networks Connectivity Maintenance based on RF Signal Strength Mapping

“…The ith robot's motion starts at the initial location ( 𝑥 0,𝑙 (𝑖) , 𝑦 0,𝑙 (𝑖) ) and increased by a step size of 𝜟 𝒚 along with the y-direction is defined in Equation ( 1). Besides, the first robot started at ( 𝑥 0,𝑙 (1) = 𝑙𝛥 𝑥 , 𝑦 0,𝑙 (1) = 0 ) for the trajectory, lth. Then, the second robot location is expressed in 𝑥 0,𝑙 (2) = 𝑥 0,𝑙 (1) + 𝑑, and 𝑦 0,𝑙 (2) =, 𝑦 0,𝑙 (1) .…”

“…Besides, the first robot started at ( 𝑥 0,𝑙 (1) = 𝑙𝛥 𝑥 , 𝑦 0,𝑙 (1) = 0 ) for the trajectory, lth. Then, the second robot location is expressed in 𝑥 0,𝑙 (2) = 𝑥 0,𝑙 (1) + 𝑑, and 𝑦 0,𝑙 (2) =, 𝑦 0,𝑙 (1) . The robots have the exact coordinates in the y-axis, and they are a d distance in the x-axis.…”

“…𝑆 𝑖 (𝑗) (𝑡) = 𝑓 (𝑥 0,𝑙 (1) , 𝑦 0,𝑙 (1) , 𝑥 𝑡,𝑙 (1) , 𝑦 𝑡,𝑙 (1) , 𝑥 0,𝑙 (2) , 𝑦 0,𝑙 (2) , 𝑥 𝑡,𝑙 (2) , 𝑦 𝑡,𝑙 (2) ϕ𝑗) (2) This is the SS measurement on the trajectory, lth, in the RF obstacle of type j existence at time t. The 𝑆 𝑖 (𝑗) (𝑡) function represents the robot's start location (𝑥 0,𝑙 (𝑖) , 𝑦 0,𝑙 (𝑖) ), time t robot's location ( 𝑥 𝑡 (𝑖) , 𝑦 𝑡 (𝑖) ) and the special characteristics of the obstacle ϕj. The index of trajectory l is l = 1,..., L (j) for each obstacle of type j. L (j) is the trajectory's number in the existence of type j obstacle.…”

“…∂𝑆 𝑙 (𝑗) (𝑡) The SS gradient is calculated following the of Fig. 16, the initial position at time t for robot one and robot two are (𝑥 𝑡 (1) , 𝑦 𝑡 (1) ) and 𝑥 𝑡 (2) , 𝑦 𝑡 (2) ). As explained in the method below, we assumed that one robot is moving while the other stays still to compute the gradient.…”

“…The majority of Communication networks, especially wireless networks, are deployed in territories with different interference sources (Different obstacles), affecting the communication signals and creating no Line Of Sight (LOS) among communication devices, so they can not identify each other. However, the Frezonet zone where the signal propagates should be free of interferences sources such as conducting and conducting obstacles of different types to an actual LOS [1,2]. One problem of the RF communications in disasters such as crumpled buildings is many signal interference sources that cause no LOS and disrupt the communication signal.…”