Adding robustness to good command response of aircraft longitudinal flight control system

The only multivariable design method in the open literature that can optimize robustness is μ synthesis method, which we utilize to add optimal robustness to good command response of aircraft longitudinal control system. The design of flight control systems with uncertainties of aircraft model and external disturbances by using μ synthesis is presented in this paper. On the basis of the requirements of flight performance, we construct the aircraft longitudinal flight control system and select the corresponding weighting functions. In the full paper, we explain in much detail how to construct such an aircraft system; here we just list the two topics explained and discussed: (1) introduction to μ synthesis method; (2) the steps of μ synthesis; the synthesis is done in 7 steps; the fifth step is D-K iterations; the sixth step is iteratively revising weights; the fifth and sixth steps are our new contributions. Longitudinal flight control system of a thrust vector aircraft is given as an example. D-K iterative method is applied till μ < 1. Sixth-order controller is used to control fast dynamic motion of the aircraft. Simulation graphs of pitch rate, normal overload, attack-angle and bank angle respectively are given. The shapes of all curves in the graphs show preliminarily that optimal robustness is ensured. Simulation results from normal overload graph show preliminarily that: (1) tracking process is not overshot; (2) regulating time is about 1.6 s.