Controller design for a micro coaxial helicopter using characteristic ratio assignment

A micro coaxial helicopter exhibits not only increased sensitivity to control inputs and disturbances, but also higher dynamic bandwidth. These properties make it much more difficult to control. The dynamic model accuracy will determine the performance of the designed controller. It is attractive in this regard to have a controller that can accommodate the fast parameter changes and perform well in such situations. Characteristic Ratio Assignment (CRA) is such a candidate for synthesizing such a controller due to its simplicity and convenience in demonstrating integrated performance measures including equivalent time constant, stability indices and robustness, with the exception of the uncertainty in determining the order of the designed controller. The paper explores the relationship between time-domain indexes (overshoot, response speed and robustness) on the one hand, and an algorithm on the other hand to design a similar PID fixed order controller for attitude control. The simulation results and their analysis validate preliminarily the proposed design method.