Control system design and evaluation for robust autonomous rotorcraft guidance

This paper describes the design and performance analysis of a control system for rotorcraft with an emphasis on the requirements called for by autonomous guidance. To be able to track trajectories, such as those generated by a guidance system, a path following controller is used in combination with a velocity control augmentation. The path following system is motivated by nonlinear stability analysis. The velocity control augmentation follows a loop-shaping design for the inner-loop attitude control and a dynamic inversion velocity control design for the outer-loop. The identified model of the dynamics along with the uncertainties is used to determine the robustness and performance of the velocity control system. Finally, the paper presents a novel method to evaluate the overall performance of the control system in terms of the tracking error statistics. These results are then used to determine a tracking error model, which can be used to predict the tracking error for a given reference.