Angular velocity observer design using vector measurements with application to attitude tracking

This article addresses the design of angular velocity observer for rigid bodies using vector measurements directly. The main contributions of our observer compared with the classical estimation algorithms lie in that it does not need to reconstruct the attitude information from the measurements nor be implemented with velocity sensors. Meanwhile, it provides three-degrees-of-freedom (3DOF) full state estimates. To avoid the unstable critical points for the attitude estimation errors on SO(3), the synergistic potential functions based hybrid method is adopted. Afterwards, an output feedback attitude tracking controller with a proportional-derivative (PD) plus feedforward form is built based on the estimates from the observer, which can also be implemented using vector measurements directly. Rigorous analysis of the stability of the observer and the combined observer-controller are presented in detail, with a separation property shown between the observer and the controller. Simulations are conducted to illustrate the effectiveness of the proposed observer and the combined attitude tracking law.