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A first order model of an electrophotographic process under the influence of several process control loops has been developed. The model is used to examine the transient behavior of the system over a range of control conditions. Results illustrate the potential benefits of process control to image quality stability. However, it is also shown that poorly designed controls can lead to significant degradation in performance. 1. INTRODUCTION The electrophotographic process consists of a series of steps which tpqether must produce a high-quality reproduction of some input image. Various models ' f3' have been developed to describe the process, beginning with document exposure, aerial image formation, electrostatic image formation and developed image formation. However, these models treat the system as time-invariant when in reality it is quite transient due to fluctuations in mechanisms, circuitry, and materials and due to ageing effects.Designers of electrophotographic equipment5' often attempt to stabilize the performance of the system by using one or more control loops. Control loops for exposure, initial photoconductor voltage, developer bias, and toner concentration are quite common. However, the effectiveness and robustness of such loops are difficult to understand and predict.This paper, the first of a series, illustrates the use of mathematical simulation as a method for studying the behavior of both uncontrolled as well as controlled systems under the influence of certain common transient phenomena.The simulation is used to assess the individual and collective performance of control loops. This is particularly valuable in instances where the design of process subsystems is decentralized. It is shown, that whereas individual control loops may perform quite well independently, interactions between loops can lead to a runaway degradation in image quality. |
