Discrete Hamiltonian Variational Mechanics and Hamel’s Integrators

Exact variational integrators were exposed in the context of Lagrangian mechanics in Marsden and West (2001). These integrators sample the trajectories of holonomic mechanical systems and are useful for developing practical mechanical integrators. This paper introduces an exact variational integrator for Hamel’s equations, which are interpreted as a noncanonical form of Hamilton’s equations. This exact Hamel integrator is then adopted for a systematic construction of low-order constraint-preserving integrators for nonholonomic mechanical systems.