Modeling and Control of Mid-flight Coupling of Quadrotors: A new concept for Quadrotor cooperation

Multirotor vehicles, quadrotors specifically, have formed a fast-growing field in robotics, with the range of applications spanning from surveillance and reconnaissance to agriculture and large area mapping. Although in most applications, a single quadrotors is used, there is an increasing interest in architectures controlling multiple quadrotors executing a collaborative task. This paper introduces a new concept of control involving more than one quadrotors, according to which two quadrotors can be physically coupled in mid-flight. This concept equips the quadrotors with new capabilities, e.g. increased payload or pursuit and capturing of other quadrotors. A comprehensive analysis of the approach is presented for the system of two coupled quadrotors. The dynamics and modeling of the coupled system is presented together with a discussion regarding the coupling mechanism and the overall control architecture. Controller gains were found using Linear Quadratic Control (LQR) techniques combined with Proportional Integral Derivative (PID) gain scheduling to account for the change in system dynamics to ensure stability and satisfactory response characteristics in actual experiments. Finally, the proposed methods are evaluated through an experiment that involved physical coupling and coupled flight of a pair of quadrotors.