A Generic Formation Controller and State Observer for Multiple Unmanned Systems

In this paper, we present a novel decentralized controller to drive multiple unmanned aerial vehicles (UAVs) into a symmetric formation of regular polygon shape surrounding a mobile target. The proposed controller works for time-varying information exchange topologies among agents and preserves a network connectivity while steering UAVs into a formation. The proposed nonlinear controller is highly generalized and offers flexibility in achieving the control objective due to the freedom of choosing controller parameters from a range of values. By the virtue of additional tuning parameters, i.e. fractional powers on proportional and derivative difference terms, the nonlinear controller procures a family of UAV trajectories satisfying the same control objective. An appropriate adjustment of the parameters facilitates in generating smooth UAV trajectories without causing abrupt position jumps. The convergence of the closed-loop system is analyzed and established using the Lyapunov approach. Simulation results validate the effectiveness of the proposed controller which outperforms an existing formation controller by driving a team of UAVs elegantly in a target-centric formation. We also present a nonlinear observer to estimate vehicle velocities with the availability of position coordinates and heading angles. Simulation results show that the proposed nonlinear observer results in quick convergence of the estimates to its true values.