Position Control of VTOL UAVs using Inertial Vector Measurements

Existing position controllers for VTOL UAVs require measurements of the system attitude (orientation) for feedback. However, in practice the orientation cannot be measured directly; it is rather obtained through the use of an attitude observer relying on a set of inertial vector measurements. In this paper a new control strategy is proposed for VTOL-UAVs which avoids the direct measurement of the system attitude (in terms of a rotation matrix, unit-quaternion or other attitude parameterization). In the proposed controller inertial vector measurements are used instead of the system attitude. This eliminates the need for an attitude observer thereby reducing the overall complexity of implementing the closed loop system and avoiding errors that are associated with the attitude observer.