Advanced Attitude Command Generation for a Helicopter UAV in the Context of a Feedback Free Reference System

Abstract

For flight control of helicopter UAV a reference model based adaptive approach is often used. In order to cope with having four control inputs to manipulate six degrees of freedom of the UAV’s rigid body, translational and rotational motion can be decoupled. This paper addresses a problem arising from this approach: the rotation control loop has to cope with two different, often contradicting, demands. The first ensures the thrust to be correctly oriented for the desired flight path. The second arises from the mission demanding a certain heading, e. g. for observation during continuous flight. A quaternion based approach is presented based on geometric relations. Two types of heading requirements are considered, one for a vector based line-of-vision (e. g. for object observation) and a heading represented by a yaw angle (e. g. for cruise flight). In order to verify the proposed algorithm a hardware-in-the-loop simulation is used. The so called elliptic turn maneuver is a challenging example for which the direction of view is commanded from the flight path independently and is thus selected for verification.