Robust multi-rotor attitude control using cascaded feedback control architecture and feedforward

This paper deals with the robust attitude control of a multirotor UAV. The main novelty is the use of a cascaded model-matching control structure that includes a reference feedforward controller along with the two angle and velocity feedback controllers. The design methodology used derives the control gain to the inner feedback loop above a certain frequency, while the outer feedback loop dominates at low frequencies. A balanced distribution of feedback between loops results in simpler, lower-bandwidth feedback controllers that allow fast angle control without dangerously amplifying measurement noise in the control action. The control designs are robust and performed in the discrete frequency domain according to the postulates of Quantitative Feedback Theory, with explicit consideration of stability, torque disturbance rejection, and angular reference tracking specifications. The proposed control solution is experimentally validated on a real quadrotor.