Model Life Extension for Continuous Process: Non-Invasive Correction of Model-Plant Mismatch with Regularization

In continuous process plants controlled by model predictive control, model-plant mismatch (MPM), due to the aging of processes, causes degradation of control performance. We propose a concept called Model Life Extension (MLE) and its implementation to mitigate this degradation in a non-invasive manner. The purpose of MLE is to continually update (re-identify) process models by using routine operating data on the assumption that the timescale of aging is much larger than the interval of excitation of reference signals. We implemented MLE by estimating MPM via L-1 regularized regression and by finding an optimal regularization parameter via crossvalidation and showed through numerical experiments that an optimal parameter can exist and be found by cross-validation for a pilot-scale distillation column. We then constructed the updated model based on the found parameter to demonstrate the possibility of correcting static-gain mismatch and transport-delay mismatch without injecting excitation signals to process inputs.