Controlled Lagrangians and Potential Shaping for Stabilization of   Discrete Mechanical Systems
  The method of controlled Lagrangians for discrete mechanical systems is extended to include potential shaping in order to achieve complete state-space asymptotic stabilization. New terms in the controlled shape equation that are necessary for matching in the discrete context are introduced. The theory is illustrated with the problem of stabilization of the cart-pendulum system on an incline. We also discuss digital and model predictive control. 
Anthony M. Bloch, Melvin Leok, Jerrold E. Marsden, Dmitry V. Zenkov