Backstepping-based flight control with adaptive function approximation

A command filtered backstepping approach is presented that uses adaptive function approximation to control unmanned air vehicles. The controller.is designed using three feedback loops. The command inputs to the airspeed and flight-path angle controller are X-c, gamma(c), V-c and the bounded first derivatives of these signals. That loop generates comand inputs mu(c), alpha(c) for a wind-axis angle loop. The sideslip angle command beta(c) is always zero. The wind-axis angle loop generates rate commands P-c, Q(c), R-c for an inner loop that generates surface position commands. The control approach includes adaptive approximation of the aerodynamic force and moment coefficient functions. The approach maintains the stability (in the sense of Lyapunov) of the adaptive function approximation process in the presence of magnitude, rate, and bandwidth limitations on the intermediate states and the surfaces.