Non-holonomic integrators

We introduce a discretization of the Lagrange-d'Alembert principle for Lagr angian systems with non-holonomic constraints, which allows us to construct numerical integrators that approximate the continuous flow. We study the g eometric invariance properties of the discrete flow which provide an explan ation for the good performance of the proposed method. This is tested on tw o examples: a non-holonomic particle with a quadratic potential and a mobil e robot with fixed orientation.