Adaptive control of aircraft lateral directional axis using subspace stabilization

A linear adaptive control for the F-14 aircraft lateral-directional axis using disturbance-observers and subspace-stabilization theory is presented. Disturbance accommodating observers are used to estimate and cancel out the combined effects of nonlinear, uncertain and off-nominal terms in real-time. Subspace stabilization techniques are used to steer the system “error-state” to a certain subspace representing the desired servo-tracking error behavior, while controlling the subsequent motion of the error-state on the subspace to the origin. The results obtained are compared with previous results obtained using gain scheduling and H _∞. Numerical simulation results demonstrate that the ideal closed-loop responses of the rolling rate and sideslip angle are adequately tracked and that the controller effectively decouples the two channels