Material advance tracking system

A friction drive system for printing, plotting or cutting a graphic image on a strip material, said system comprising:

• at least one drive motor for rotating a plurality of friction wheels, said plurality of friction wheels driving said strip material in a longitudinal direction;
• a motor encoder cooperating with said drive motor for tracking rotational movement of said drive motor, said motor encoder generating a motor encoder signal;
• detecting means for tracking movement of said strip material, said detecting means generating a detecting encoder signal indicative of said longitudinal position of said strip material;
• means for comparing said motor encoder signal with a commanded position of said strip material and based on such comparison generating a motor encoder position error signal, said means for comparing also comparing said detecting encoder signal with said commanded position of said strip material and based on such comparison generating a detecting encoder position error signal;
• means for filtering said detecting encoder position error signal to generate a filtered detecting encoder position error signal and for filtering said motor encoder position error signal to generate a filtered motor encoder position error signal;
• and
• means for combining said filtered detecting encoder position error signal and said filtered motor encoder position error signal to generate a combined position error signal.

A method for feeding a strip material through a printer, plotter or cutter apparatus, said strip material being driven in a longitudinal direction by a drive motor, said drive motor generating a drive motor signal said method comprising:

• coupling a motor encoder to said drive motor to detect rotational movement of said drive motor, said motor encoder generating a motor encoder signal;
• communicating said motor encoder signal to a microprocessor;
• monitoring actual longitudinal motion of said strip material with detecting means;
• coupling a detecting encoder to said detecting means to detect movement of said detecting means, said detecting encoder generating a detecting encoder signal;
• communicating said detecting encoder signal to said microprocessor;
• comparing said motor encoder signal with a commanded position of said strip material to generate a motor encoder error signal;
• comparing said detecting encoder signal with said commanded position of said strip material to generate a detecting encoder error signal;
• passing said detecting encoder error signal through a low pass filter to generate a filtered detecting encoder error signal;
• generating an error position signal using said filtered detecting encoder error signal;
• and
• communicating said error position signal to said drive motor to minimize difference between said actual position of said strip material and said commanded position of said strip material.

A method for feeding a strip material through a printer, plotter or cutter apparatus, said strip material being driven in a longitudinal direction by a drive motor, said drive motor generating a drive motor signal said method comprising:

• coupling a motor encoder to said drive motor to detect rotational movement of said drive motor, said motor encoder generating a motor encoder signal;
• communicating said motor encoder signal to a microprocessor;
• monitoring actual longitudinal motion of said strip material with detecting means;
• coupling a detecting encoder to said detecting means to detect movement of said detecting means, said detecting encoder generating a detecting encoder signal;
• communicating said detecting encoder signal to said microprocessor;
• comparing said motor encoder signal with a commanded position of said strip material to generate a motor encoder error signal;
• comparing said detecting encoder signal with said commanded position of said strip material to generate a detecting encoder error signal;
• passing said motor encoder error signal through an all pass filter to generate a filtered motor encoder error signal;
• passing said detecting encoder error signal through a low pass filter to generate a filtered detecting encoder error signal;
• generating an error position signal by combining said filtered motor encoder error signal and said filtered detecting encoder error signal;
• and
• communicating said error position signal to said drive motor to minimize difference between said actual position of said strip material and said commanded position of said strip material.