Robust spatially sampled controller design for banding reduction in electrophotographic process

An improved controller design and implementation technique for electrophotographic process (EP) was proposed. The new controller was modified from a previous design to address two additional issues for generic EP platforms, i.e., reducing position-dependent disturbances and reducing system sensitivity to manufacturing variations in EP engine and consumables. To handle position-dependent periodic disturbances, a digital repetitive controller was developed and implemented using spatial sampling. The result is a control algorithm that will take 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 (TDOF) 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. Printed samples demonstrated significant reduction in visible banding that was verified by reflectance measurement.