Asymptotic stabilization of quadrotor helicopter's attitude using an optimal hierarchical control technique

A hierarchical controller design based on nonlinear optimal theory and backstepping technique is developed. This control law which stabilizes globally the attitude of the system for all the equilibrium points, is parameterized by quaternions. First, for the kinematic subsystem, we design a virtual optimal angular velocity. To obtain the global minimum of the performance index, this optimal angular velocity is only discontinuous in initial values. It can be regarded as a combination of open loop control and closed loop control. Then for the dynamic subsystem, we design a optimal control that can force the angular velocity to track the virtual optimal angular velocity. Thus, we design a control that is more natural and efficient use of energy, fact that states converge to the nearest equilibrium. The effectiveness of the proposed method is demonstrated by simulation results.