Design of robust digital model-following flight control systems

The robustness characteristics of digital model-following systems incorporating fast-sampling PID (proportional plus integral plus derivative) controllers are elucidated in the case of both regular and completely irregular linear multivariable plants. It is shown that the plant-parameter variations tolerable by such digital model-following systems can be expressed very simply in terms of the step-response matrices of the nominal and actual plants. These general results are illustrated by examining the robustness characteristics of digital model-following systems for the F4-E aircraft. This example demonstrates the ease with which the methodology of B. Porter et al. (1988) can be used to design robust digital model-following flight control systems