  A Pontryagin-based approach to solve a class of constrained Nonlinear Model
Predictive Control problems is proposed which employs the method of barrier
functions for dealing with the state constraints. Unlike the existing works in
literature the proposed method is able to cope with nonlinear input and state
constraints without any significant modification of the optimization algorithm.
A stability analysis of the closed-loop system is carried out by using the L-2
norm of the predicted state tracking error as a Lyapunov function. Theoretical
results are tested and confirmed by numerical simulations on the Lotka-Volterra
prey/predator system.
