Automatic pen type sensor for graphic recorder

Abstract

An automatic pen positioning system is operative within a graphic recording system having a plurality of recording pens moveably supported by a pen carriage. The pen carriage is moveably along a first path above a media which is moveable along a second path. A motor drive system moves a selected one of the plurality of pens into contact with the media during recording. A closed loop servo system is operative upon the pen motor drive and is controlled by a position information processor. A following error processor is coupled to the servo system and compiles a periodically sampled table of absolute position, commanded position and following error for the servo system during the initialization process in which each pen is moved toward the media at a constant velocity until it impacts the media impeding further pen motion. The following error processor determines the pen to media contact position of the engaged pen on the basis of the information derived from the servo system. A pen type sensor responds to media contact position and determines pen type in accordance with a plurality of contact point ranges stored in a look-up table. The appropriate pen pressure for the pen is applied in response to the pen type sensor input. Each pen is subjected to the initialization process to establish its pen to media contact position and pen type when first used during a plot.