Swarm Navigation with TelosB Motes

The concept introduced below provides a highly effective swarm navigation scheme that is of low complexity, robust, and highly scalable. Rather than using a few highly complex and expensive swarm agents to complete a mission, the group at Easysen believe in the advantages of large ultra-low complexity swarms that solve problems reliably through emergent behavior.

EasySen is a start-up company who in conjunction with the University of Notre Dame’s Mobile Sensing Systems (MOSES) Lab, has developed an autonomous sensor swarm that uses TelosB nodes for navigation of swarm agents. The principle is based on Zigbee radio beacon induced potential fields and provides an ultra low cost and complexity solution to mobile sensing for land, sea, and air vehicles. Stereo TelosB receivers and stereo sensor suites (EasySen SBT80 / SBT30-EDU) allow for rather elaborate task execution.

The group at EasySen proposed the use of radio frequency beacons to generate (switched) potential fields for navigation of large numbers of swarm agents. The idea is to use attractive beacons as waypoints and local attractors. Repelling beacons on each agent and waypoint are used to control the density of agents and avoid collisions.  If a certain sequence of waypoints defines a navigation path, then the attractive beacons need to be distinguishable and need to be visited in a certain sequence. (This is easily implemented in form of a finite state machine in each sensor swarm agent.) Repelling beacons are local and do not need to be distinguishable.  Individual sensor swarm agents are equipped with a side-looking stereo receiver with opposite directions of highest sensitivity. A simple difference between the left and the right Receive Signal Strength Intensity (RSSI) allows the agent to detect in which half space (relative to the center length axis of the vehicle) a beacon is located. One can then navigate towards a beacon by always moving towards the receiver side that has produced the stronger RSSI reading. For repelling beacons, one always moves towards the direction of the smaller RSSI signal.

The applications of this paradigm are many and range from environmental clean-up such as oil spill removal to surveillance and protection tasks. A ground vehicle swarm that performs a simple detection task is shown in the video below:

The company also produces readily usable plug-in surveillance sensor suites for the TelosB wireless 802.15.4 platform:

• The Wi-Eye, an ultra-sensitive sensor board that is capable of detecting the IR signature of moving vehicles from as far as hundreds of feet away.
• The SBT80 is an 8-modality sensing platform, ideal for sensor fusion applications.

Both sensor suites (the Wi-Eye and the SBT80) are prime candidates for perimeter security, traffic monitoring, tracking, and occupancy detection tasks, just to name a few. In addition, EasySen also offers SBT30-EDU, a low-price educational prototyping board that interfaces to external signal sources.  Click here for more information on the TelosB Mote platform.