PD+ based output feedback attitude control of rigid bodies with improved performance

We address the problem of output feedback attitude control of a rigid body in quaternion coordinate space through a modified PD+ based tracking controller. The control law ensures faster convergence to the desired operating point during attitude maneuver, while keeping the gains small for station keeping, thus being less sensitive to measurement noise. The angular velocity is estimated with a similar technique, thus keeping the property of lower sensitivity to measurement noise. A direct consequence is a drop in energy consumption and more accurate estimation results when affected by sensor noise. More precisely, we show uniform practical asymptotic stability of the equilibrium point for the closed loop system in the presence of unknown, bounded input disturbances. Simulation results illustrate the performance improvement with respect to PD+ based output feedback control with static gains.