Globally stable automatic formation flight control in two dimensions

In this paper we address the problem of nonlinear formation flight control design using a leaderfollower configuration. The problem is to design a formation hold autopilot for the follower vehicle such that the relative positions between the leader and the follower are maintained close to their desired values. We first present a nonlinear control algorithm based on the dynamics of the relative positions between the two vehicles. Such a control law results in a locally stable system since the corresponding dynamic model has a singularity in the state space. We next propose a singularity-free formation control algorithm based on a new error formulation in the inertial frame. We prove global stability of the overall system, and demonstrate favorable properties of the proposed formation control algorithm through computer simulations.