Practical nonlinear control allocation method based on feedback of position of surface

To focus on the problems of nonlinearity and coupling between the moment coefficients and the surface deflections when the aircraft autonomously takes off, lands and flies with high angles of attack, a practical and novel nonlinear control allocation method based on feedback of position of surface was proposed for tailless flying wing aircraft (TFWA). The nonlinear moment coefficient of the surface deflection in previous sampling interval was removed from the desired three-axis moment coefficients by feedback of position of surface. Thus the nonlinear control problem was transformed into the linear control allocation problem and was solved. Unanimous asymptotic stability of this method was proved and steady state error was zero; the feasibility of this method was also analyzed. Comparisons of digital simulation were done with sequential linear programming, sequential quadratic programming and genetic algorithm, and results prove the high accuracy and fast computing speed of this method. Efficiency of this method to solve nonlinear control allocation problem was verified by the digital simulations of pseudo-inverse method, fixed-point iteration and neighbor search method. Finally, strong generality and good real-time performance of this method for TFWA and F18 were demonstrated on the xPC-DSP semi-physical simulation platform.