  The problem of estimating the angular speed of a solid body from attitude
measurements is addressed. To solve this problem, we propose an observer whose
dynamics are not constrained to evolve on any specific manifold. This
drastically simplifies the analysis of the proposed observer. Using Lyapunov
analysis, sufficient conditions for global asymptotic stability of a set
wherein the estimation error is equal to zero are established. In addition, the
proposed methodology is adapted to deal with angular speed estimation for
systems evolving on the unit circle. The approach is illustrated through
several numerical simulations.
