  The movement of cooperative robots in a densely cluttered environment may not
be possible if the formation type is invariant. Hence, we investigate a new
method for time-varying formation control for a group of heterogeneous
autonomous vehicles, which may include Unmanned Ground Vehicles (UGV) and
Unmanned Aerial Vehicles (UAV). We have extended a Negative-Imaginary (NI)
consensus control approach to switch the formation shape of the robots whilst
only using the relative distance between agents and between agents and
obstacles. All agents can automatically create a new safe formation to overcome
obstacles based on a novel geometric method, then restore the prototype
formation once the obstacles are cleared. Furthermore, we improve the position
consensus at sharp corners by achieving yaw consensus between robots.
Simulation and experimental results are then analyzed to validate the
feasibility of our proposed approach.
