Direct Digital Design Method for Reconfigurable Multivariable Control Laws for the A-7D Digitac II Aircraft

摘要

This thesis investigates control of an aircraft when there is a primary control surface failure. The object of this study is to reconfigure the remaining control surfaces to compensate for the additional forces and moments generated by the inoperative control surface. To study this flight control problem, a comprehensive aircraft model is required which considers each control surface operating individually. A six degree-of-freedom aircraft model is developed, including all the individual control surfaces. A control surface input can produce both a lateral and/or a longitudinal response. Thus, the equations of motion cannot be decoupled for the design of the control laws. The coupling between the axes requires the derivation of several new non-dimensional control derivatives. Using the geometrical properties of the aircraft and the Digital Datcom computer program, the needed control derivatives are derived. The entire eigenstructure assignment method is used to assign both the eigenvalues and the eigenvectors to the closed-loop plant matrix. This method is used for the direct digital design of a multivariable discrete regulator and tracker control law. The effect of increasing the number of control inputs on the relative degree of controllability of the states was determined by singular value decomposition.