The effect of insufficient excitation in PCA estimation

Linear relations external to the monitored plant, such as ratio-control, feedback or upstream constraints, make the data non-persistently exciting for the identification of the plant model. The effect of such external relations is studied on the PCA estimation of linear static models, and compared to LS estimation. Also, ways to detect the presence of such relations in the PCA framework are suggested. The results are extended to persistency and order/degree estimation in linear dynamic and polynomial static models.