Robust Spatial-Sampling Controller Design for Banding Reduction in Electrophotographic Process

Abstract

An improved controller design and implementation technique for electrophotographic process (EP) was proposed. The new controller aimed at solving two additional issues for generic EP platforms, i.e., reducing position-dependent or spatially periodic disturbances, and reducing system sensitivity to manufacturing variations in EP engine and consumables. To handle spatially periodic disturbances, a digital repetitive controller was synthesized and implemented using a spatial-sampling scheme. The result is a control algorithm that takes into account the variation of the nominal operating speed. Second, system variations due to manufacturing variations as well as consumable changes were incorporated into the design of a two degree of freedom robust controller. The controller is optimal in the sense that it minimizes the size of the sensitivity function from a set of disturbance signals to a set of measurable signals critical to print quality, e.g., photoconductor drum velocity or scan line spacing. A suitable trade-off between system performance and robustness to system modeling uncertainties was considered in the synthesis and optimization formulation. The effectiveness of the proposed controller design and implementation technique was numerically and experimentally verified. Significant reduction in visible banding was seen in printed images and was verified by reflectance measurement.