A Method for the Improvement of Impact Printer Performance

Abstract

The stored energy type of impact printer is a commonly used computer output device. It can be operated at quite high frequencies due to the fact that it has a large initial activation force. However, limitations on printer speed exist; these are thought to be due primarily to uncertainties in the position and velocity of the armature during settle-out between excitation pulses. This results in variations in flight times and in print forces. In this paper we consider an open-loop control strategy which modifies the driving pulse in such a manner that it aids the restoring force of the print hammer and armature during the settle-out phase of the motion. Simulation studies of our simplified piecewise linear model (Tung and Shaw, 1988) and Hendriks’ (1983) model indicate that the operating speed of impact printers can be significantly increased using this method. Printer performance criteria are also established in the paper. These are based on the requirement that acceptable print quality be achieved for arbitrary combinations of driving pulses which have some minimum time lapse between pulses. We use these criteria to demonstrate the limitations on printer speed and to indicate how the control method is able to increase printer speed. Such criteria are quite general and may be used for more complicated models and controllers.