Adaptive Formation Control for Rovers Traveling over Unknown Terrains

A novel adaptive formation-control strategy for a group of rovers navigating over unknown terrain is presented. A leader-follower formation control architecture is employed. Direct adaptive control laws and a formation speed adaptation strategy are developed that 1) bring the rovers into a prescribed formation from arbitrary in-plane locations and 2) enable the group to navigate over unknown and changing terrain, while staying in formation in the presence of actuator saturation. On-line estimates of generic friction parameters account for terrain' surface variations. The leader specifies a reference motion for the entire fleet, including both straight-line and turning maneuvers. In saturation events, the formation speed is reduced based on the maximum sustainable speed of the slowest saturated rover using internal fleet communication, allowing the formation error to stay bounded and small. A formal proof for asymptotic stability of the formation system under nonsaturated conditions is given. A simulation example is presented that demonstrates formation initialization, formation-keeping, and formationswitching in both actuator saturation and nonsaturation circumstances.