  In this paper, a method is proposed for on-line monitoring of the control
updating period in fast-gradient-based Model Predictive Control (MPC) schemes.
Such schemes are currently under intense investigation as a way to accommodate
for real-time requirements when dealing with systems showing fast dynamics. The
method needs cheap computations that use the algorithm on-line behavior in
order to recover the optimal updating period in terms of cost function
decrease. A simple example of constrained triple integrator is used to
illustrate the proposed method and to assess its efficiency.
