On-line implementation of nonlinear MPC: an experimental case study

Abstract

A nonlinear model predictive control algorithm is implemented on-line to control the liquid level and temperature in a pilot plant CSTR, where an irreversible exothermic chemical reaction is simulated experimentally by steam injection. The dynamic behavior of the pilot plant reactor is represented using a mechanistic, first principle model and a comparison between off-line simulation and experimental data is presented. Several sources of model mismatch and unmeasured disturbances are identified that affect the quality of the model in representing the reactor dynamics. Despite these mismatches and disturbances, the closed loop system is able to track setpoint changes and reject disturbances quite well. In particular, the NMPC controller is demonstrated for different tuning parameters and under conditions of constraint saturation at unstable points.