  Almost-global orientation trajectory tracking for a rigid body with external
actuation has been well studied in the literature, and in the geometric setting
as well. The tracking control law relies on the fact that a rigid body is a
simple mechanical system (SMS) on the $3-$dimensional group of special
orthogonal matrices. However, the problem of designing feedback control laws
for tracking using internal actuation mechanisms, like rotors or control moment
gyros, has received lesser attention from a geometric point of view. An
internally actuated rigid body is not a simple mechanical system, and the
phase-space here evolves on the level set of a momentum map. In this note, we
propose a novel proportional integral derivative (PID) control law for a rigid
body with $3$ internal rotors, that achieves tracking of feasible trajectories
from almost all initial conditions.
