Controlled Lagrangians and Stabilization of Euler--Poincar\'e Mechanical Systems with Broken Symmetry I: Kinetic Shaping

We extend the method of controlled Lagrangians with kinetic shaping to those mechanical systems on semidirect product Lie groups with broken symmetry, more specifically to the Euler–Poincar'e equations with advected parameters. We find a matching condition for the controlled Lagrangian for such systems whose configuration manifold is a general semidirect product Lie group $$\mathsf{G}$ \ltimes V$. Our motivating examples are a bottom-heavy underwater vehicle and a top spinning on a movable base. Their configuration space is the special Euclidean group $\mathsf{S}\mathsf{E}(3)=\mathsf{S}\mathsf{O}(3)⋉{\mathbb{R}}^3$, where the $\mathsf{S}\mathsf{E}(3)$-symmetry is broken by the gravity. The controls resulting from the matching condition stabilize unstable equilibria of these examples. Furthermore, the matching helps us find additional dissipative controls that asymptotically stabilize those unstable equilibria.