Modeling and Control of a Hybrid Two-Component Development Process for Xerography

Development is one of the six key steps in xerographic printing processes. Under certain printing conditions, the “deveopability” of the toner particles tends to degrade resulting in a loss of image quality. Existing process controls have limited authority in compensating for this degradation, and, ultimately, a service operation may be required to install fresh toner. From a customer perspective, this machine maintenance results in productivity loss and added cost, both of which need to be minimized. In this paper, a control oriented model that characterizes “developability loss” is derived from an experimentally validated comprehensive statistical model. The resulting model considers the stress case of printing “low area coverage” documents (e.g., text pages) in a low relative humidity environment, and it maps the development voltage and toner dispensing rate actuators to the developed toner mass per unit area, which is the sensed output and is also used as a surrogate for print quality. Under these operating conditions, system analysis shows that developability loss is unavoidable. Given this result, a constrained time optimal control problem is formulated to determine the dispensing strategy to maximize the printer operating time while maintaining acceptable developability. Numerical solution shows that for the stress operating condition leading to developability loss, the optimal dispensing strategy increased the operating time by 170% compared with a conventional dispensing strategy.