Development and testing of a coaxial helicopter controlled by shifting the center of gravity

Coaxial rotorcraft are superior to quadcopters in terms of power coefficients. The control of coaxial rotorcraft systems entails the use of traditional mechanically complex hub systems. This ultimately offsets some of the advantages yielded by these superior power coefficients. As an alternative to this, the proposed vehicle decouples the thrust production and pitch-and roll-control of the coaxial rotorcraft. This decoupling occurs by shifting the center of gravity of the vehicle, which creates a moment about the desired axis; yaw is controlled by varying the speed of the two coaxial rotors. The control of such a vehicle is arduous due to the presence of sharp nonlinearities in the rotational dynamics. Thus, a non-linear controller is mandatory to effectively control the vehicle. Such a controller has been designed and tested using simulation techniques. Furthermore, the initial flight test has been performed for evaluation.