Launch Vehicle Autopilot Design using Automated QFT-PID Controller

Physical systems are normally characterized by high uncertainty which makes it difficult for the closed loop system to have good stability margins and meet required performance specifications. Quantitative feedback theory (QFT) is a method of robust control which deals with the effects of uncertainty systematically. In the proposed work, QFT methodology is being adopted to design the autopilot for a launch vehicle with rigid body dynamics and flexibility dynamics. The conventional approach to QFT is to manually manipulate the poles and zeros of the nominal open loop transfer function. This is an adhoc approach as it greatly depends on the experience of the designer. To overcome this problem, an algorithm has been implemented that gives a set of feasible PID controllers. Based on the gain margin, phase margin, transient response and closed loop tracking specifications, the controller that closely satisfies the given performance specifications is selected. Further, a notch filter is also incorporated to complete the autopilot design.