Due to the limitations of GPS in areas where line of sight to the sky is obstructed the development of a GPS-free algorithm for relative formation
control is an asset to collaborative vehicles. This paper presents a novel approach based on the Received Signal Strength Indication (RSSI) measurement between broadcast and receive nodes to calculate distance and using the data transfer capability to allow each vehicle to develop a table of relative positions. These relative positions are used to create a potential
field that results in an absolute minimum at the vehicles desired position. All vehicles are numbered sequentially. The numbering defines the order in which they will broadcast their data, as well as their position along the perimeter. This thesis looks at two control methods for achieving a formation. The first is the circular motion method that puts perimeter nodes in an orbit around around the perimeter center. The second is a gradient descent method that calculates the gradient of the potential field. Both methods achieve a formation when all perimeter nodes are at their absolute minimums in the potential field. Tests were conducted to analyze RSSI measurements using the 802.15.4 protocol, and a mathematical simulation was conducted for each control algorithm.
