We are developing and implementing low complexity swarm algorithms to perform robust sensing using mobile agents. Our current implementations are primarily based on the following platforms.

1. VEX mobile robot

2. Hovercraft

The Navigation Principle

Radio beacons generated using packet transmissions via IEEE 802.15.4 / Zigbee based wireless nodes [Tmote] are used to guide the navigation path of the mobile swarm agents. Each mobile agent is fitted with two directional antennas in its left and right sides. These antennas are directly coupled to two separate Tmote nodes (Master and Slave nodes).

By comparing the received signal strength (RSSI) values in the master and slave nodes (via the left and right antennas respectively), the mobile agent can navigate towards an attractive beacon, or navigate away from a repel beacon. Details including the beacon type (attractive or repel) and Beacon ID are included in the data payload of the packet being transmitted by the wireless radios at the beacons. 

This principle is described in detail in the following publications:

· M. Scheutz, P. Schermerhorn, and P. Bauer, “The utility of heterogeneous swarms of simple UAVs with limited sensory capacity in detection and tracking tasks,” in Proceedings of the IEEE Swarm Intelligence Symposium, 2005, pp. 257– 264.[PDF]

However, this does not provide enough distinction between the RSSI values received over the left and right directions, for the successful navigation of the agent using the above principle.  Hence, we designed an approximately parabolic shaped directional antenna using an Aluminum sheet, and placed the Tmote nodes in its focal point. This apparatus is proven to give good directionality, and thus accurate and robust navigation of agents.