IMPROVED CD CONTROL USING WAVELET-BASED MD/CD SEPARATION

摘要

Most cross-directional (CD) control systems on paper machine simply use exponential filtering of raw scanned data obtained from basis weight and moisture gauges to estimate the cross-directional profile. Because those profile estimates are then used to compute the CD control actuations, a reliable and accurate CD profile estimate is crucial to obtain satisfactory performance from the CD controllers. This paper presents the results obtained on a production sack kraft machine when replacing the standard exponential filter by a wavelet filter that has been in continuous use for over 18 months. The significantly improved control performance appears to indicate that the wavelet filter provides a more reliable estimate of the true CD profiles while at the same time filtering out undesirable high-frequency spatial components is difficult to achieve for which robust control.