Robust Nonlinear Fault-Tolerant Control of a Small-Scale Helicopter

A robust nonlinear fault-tolerant control system for a class of underactuated non-minimum phase nonlinear mechanical systems such as a small-scale autonomous helicopter is described. This novel helicopter controller innovatively combines the principles of feedback linearization, robust control, and Linear Quadratic Regulator (LQR) techniques in order to ensure asymptotic tracking of the helicopter position and heading for a commanded desired flight trajectory. The control system ensures recovery from unsafe modes of operation arising due to disturbances and certain actuator failures, while assuring the asymptotic stability of the system zero-dynamics characterized by the roll and pitch states and their rates. The proposed controller was implemented in flight tests on R-max Yamaha helicopter.