Browse Prior Art Database

Software Speed Correction Adjustment for a Print Band

IP.com Disclosure Number: IPCOM000120430D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 4 page(s) / 154K

Publishing Venue

IBM

Related People

Melnyk, G: AUTHOR [+3]

Abstract

Disclosed is a microprocessor routine that will correct the average speed error of the print band in a line printer. Thus, printer throughput is assured without the concern that some machines may run unduly fast. The problem solved is of particular concern in a multiple print speed machine. A programming technique is described that will adjust the band average speed to its nominal value as accurately as is desired.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 50% of the total text.

Software Speed Correction Adjustment for a Print Band

      Disclosed is a microprocessor routine that will correct
the average speed error of the print band in a line printer. Thus,
printer throughput is assured without the concern that some machines
may run unduly fast.  The problem solved is of particular concern in
a multiple print speed machine.  A programming technique is described
that will adjust the band average speed to its nominal value as
accurately as is desired.

      In a high-speed line printer, the program that controls the
band speed to be used and the hardware components that dynamically
control the band to that speed have fixed, but stable, tolerances.
This can cause the average speed to be insufficiently close to the
nominal value.  The speed does not require frequent correction so it
is done the first time the band is started after a speed change
command from the main printer microprocessor.

      High-speed impact printers typically have the printing element
implemented as a steel band having embossed characters, as shown in
Fig. 1.  Additionally, the band contains embossed marks which are
detected and interrupt a microprocessor.  These are used to locate
the characters, identify the band in use and provide a
once-per-revolution "home" pulse so it knows the relative location of
each character.

      The microprocessor typically defines the band speed by placing
a number in a counter.  The value can represent either (a) a fixed
time equal to one-half the desired time between character marks or
(b) a time which makes the counter generate a frequency equal to the
desired frequency of the character marks.  Which value is used
depends on the type of hardware servo loop control system but it does
not affect the intent of the disclosure.

      The microprocessor monitors the band speed by measuring the
time between character marks and compares this time with predefined
error windows.  Any difference between the desired and actual times
of the character marks is an error in the nominal speed of the band.
The error windows in the program are based on the desired nominal so
any error will skew the average toward one error limit.  This reduces
the safety factor and results in slight throughput differences
between machines, because print rate is partially determined by band
speed.

      This solution corrects the band speed by adding an algebraic
factor to the nominal number to be placed into the counter.  The
average band speed is accurately measured over one complete band
revolution and is subtracted from the nominal.  The difference is
divided by twice the number of marks per revolution since the value
in the counter represents one-half the period of one character mark.
This factor is added to the nominal value to be sent to the counter,
thereby correcting the band speed by introducing an error equal to
and opposite that produced by the tolerances in the software/hardware
control system.

...