Almost-global tracking for a rigid body with internal rotors

Inspired by recent work on a PID-like tracking control law for an interconnected mechanical system on a Lie group, this article presents a novel tracking control law for such mechanical systems, adapted from the one proposed by the authors for systems evolving on a Riemannian manifold setting. The interconnected mechanical system consists of a rigid body with three internal rotors for attitude actuation. The novelty of the control law lies in viewing the rigid body as a simple mechanical system (SMS) by incorporating the additional quadratic velocity terms arising from the interconnection into the control law, and then proceeding with a straightforward stabilizing PID tracking synthesis. The novel algorithm achieves tracking of feasible trajectories from almost all initial conditions.