High-performance switching QFT control for large radio telescopes with saturation constraints

This paper presents a novel, switching quantitative-feedback-theory (QFT) control system design methodology with a nonlinear model-based internal loop, and applies it to control a large radio telescope with saturation constraints. The dynamics of servo-systems of large radio telescopes typically vary according to azimuth and elevation angles, temperature, friction, speed and acceleration, leading to nonlinearities and plant parameter uncertainty. The new controller design methodology combines robust QFT techniques with nonlinear switching strategies and a nonlinear model-based inner loop, going beyond the classical linear limitations of conventional controllers. As shown in the paper, high performance for robust reference tracking and robust disturbance rejection is achieved, even under saturation constraints in the actuators. The controller performance is demonstrated by using realistic/simplified rigid body model of an existing extra-large radio telescope.