Quantitative Feedback Theory based robust control design for a flexible launch vehicle

Quantitative Feedback Theory (QFT) method is a frequency domain based robust control design for feedback control systems. This paper deals with the attitude (pitch) control of a flexible launch vehicle using QFT. The objective is to ensure the plant´s stability by reducing the effect of uncertainty and by stabilizing the bending mode components in the closed loop system. Parametric uncertainty of the plant and performance specifications were defined first and a QFT controller is designed satisfying all requirements. Since the plant is unstable and highly uncertain, a multi loop QFT controller design method has been proposed. Results are validated through simulations and performance is compared with a conventional PD controller.