DISCRETE-TIME, MIXED-NORM CONTROL SYNTHESIS APPLIED TO AIRCRAFT TERRAIN FOLLOWING

A fixed-order, mixed-norm control synthesis technique for discrete tim e linear systems is demonstrated. The method allows the control-system designer to combine the H-2, I-1, and H-infinity, norms of dissimilar transfer functions into a single constrained optimization problem. An y number or combination of constraints can be added to the problem, an d the method constrains the norms directly without reliance on upper b ounds to the norms. The method is applied to a terrain-following probl em involving a multi input multi-output model of a lighter aircraft. A n H-2-I-1 problem is formulated and solved to provide altitude and fli ght-path angle tracking in the presence of wind gusts and sensor noise . Finally, an H-infinity constraint on output complementary sensitivit y is added to improve robust stability.