(139b) On the Stability of Infinite Horizon Economic MPC

The method of Economic Model Predictive Control (EMPC) is conceptually attractive in that it replaces the traditional quadratic objective function of MPC with an economic based objective function. However, may have indicated concerns about the stability of EMPC. In this presentation, we begin with an exceedingly simple example of a reactor with a time-invariant economic objective function and illustrate that minor changes to the economic objective function will render the closed-loop system unstable. Furthermore, it will be shown that for this example larger prediction horizons will recover stable operations. These stability characteristics will then be shown to be an example of myopic behavior in the sense that insufficient horizons will cause the EMPC to reach for short-term gains as it is unaware of the long-term consequences. We will then present Infinite Horizon EMPC (IH-EMPC) as an extension of EMPC and illustrate that for this example, stability and closed-loop performance are virtually insensitive to the computational horizon employed.