Simultaneous low-order control of a nonlinear quadrotor model at four equilibria

Four equilibria of a nonlinear quadrotor model are considered as a problem for simultaneous stabilization. Linearizations at these equilibria represent the operating modes corresponding to hover, vertical translation with any constant velocity, and horizontal translations with either any constant roll angle tilt or any constant pitch angle tilt. The linearizations at hover and vertical translation give rise to linear time-invariant systems to be stabilized. Each setting of constant roll angle or pitch angle gives rise to a different linear time-invariant system to be stabilized. Any finite number of such systems are shown be simultaneously stabilizable by simple, low-order and decentralized controllers with integral-action. Synthesis procedure for such controllers is described.