Robust attitude control of small-scale unmanned helicopter

Robust attitude control problem is investigated for a small-scale unmanned helicopter. The control objective is to track roll and pitch reference signals agilely and accurately. Under hovering and mild maneuver flight conditions, the model of roll or pitch dynamics is regarded as a nominal linear plant with an equivalent disturbance which contains parameter perturbations and external disturbances. Based on the signal compensation technique, the controller is designed in two parts: a nominal linear controller and a robust compensator. The designed controller is linear and time-invariant, easy to be realized and suitable for the onboard system of the helicopter. Only knowledge about the bound of the equivalent disturbance is required. The robust control properties of the closed-loop system are proven and real flight experiments show the effectiveness of the proposed control strategy.