MIXED H-2 H-INFINITY METHOD SUITABLE FOR GAIN SCHEDULED AIRCRAFT CONTROL/

The formulations of mixed H-2/H-infinity gain scheduling control of ai rcraft in longitudinal motion are developed, The coefficients of a lin ear model of aircraft are estimated from the aircraft geometry. Based on flight Mach number, gain scheduling is applied with the mixed H-2/H -infinity. It is shown that the state equation of aircraft can be math ematically simplified to the standard mixed H-2/H-infinity problem. Th e advantage of decoupling the aircraft system based on phugoid (slow) and short period (fast) modes is to allow the slow model with its dist urbance to be controlled by the H-2 method, whereas the fast system wi th the fast disturbance is to be stabilized by the H-infinity techniqu e. A comparison of this method with the standard H-infinity control is made using aircraft coefficients derived for a large commercial airpl ane. It is shown that the current method will provide better performan ce for the given aircraft while the condition on the disturbance atten uation is also satisfied. The actual model controlled by the estimated controller and by the real controller is also discussed, It is shown that the estimated controller performs as well as the controller deriv ed from the actual model.