Conditions for offset elimination in state space receding horizon controllers: A tutorial analysis.

ALEJANDRO GONZÁLEZ; EDUARDO ADAM; JACINTO MARCHETTI

CHEMICAL ENGINEERING AND PROCESSING

Elsevier

Año: 2008 vol. 47 p. 2184 - 2194

0255-2701

An offset free control is one that drives the controlled outputs to their desired targets at steady state. In the linear model predictive control (MPC) framework, the elimination of steady state offset may seem a little obscure, since the closed loop optimization tends to hide the integral action. Theoretically, implementing a well posed optimization problem and having unbiased steady state predictions are sufficient conditions to eliminate the output offset. However, these basic conditions are not always achieved in practical applications, especially when state space models are used to perform the output predictions. This paper presents a detailed practical analysis of the existing strategies to eliminate offset when using linear models with moderated uncertainties. In addition, these strategies are used for a continuous stirred tank reactor (CSTR) control with nonlinear dynamic, in order to evaluate the formulations in a more realistic condition.