Cascade control of the toycopter

This paper deals with the control of a two-degree-of-freedom, laboratory-scale helicopter-like system (termed the toycopter), where the aerodynamic force is manipulated using the propeller speed. This system can be shown not to be flat and thus classical linearization techniques cannot be applied. However, a low-order flat system can be obtained by (i) using a high-gain feedback with suitable proportional gains on the propeller speeds, and (ii) neglecting the inertial cross coupling terms. The flatness can be exploited to ensure precise tracking of reference trajectories and good disturbance rejection.