Track pitch error compensation system for data cartridge tape drives

In a tape drive of the type configured for reading data from and/or writing data to any of a plurality of magnetic tapes, each tape having adjacent servo tracks with apparent centerlines spaced about a tracking axis, and including a multichannel head assembly having a plurality of channels of read gaps which produce position error signals (PES) representative of positions of the read gaps on the tracking axis with respect to the apparent centerlines of servo tracks on the tape, a positioner responsive to positioner drive signals for driving and positioning the head assembly on the tracking axis with respect to servo tracks on the tape, and a servo control system connected between the head assembly and positioner for generating positioner drive signals causing a servoing read gap to be servo locked to a desired servo track as a function of the PES when operated in a closed-loop servo mode, a method for operating the servo control system to compensate for the track pitch errors in the tape drive and/or magnetic tape and causing the servoing reed gap to be servo locked to desired centerlines of the servo tracks, the method characterized by:

• determining and storing one or more track pitch error values for each magnetic tape, wherein determining the track pitch errors comprises the steps of:
• determining one track pitch delta drive signal values representative of the magnitudes of positioner drive signals causing the positioner to drive the head assembly between two adjacent servo tracks;
• determining two track pitch delta drive signal values representative of the magnitudes of positioner drive signals causing the positioner to drive the head assembly between two servo tracks spaced apart by a servo track;
• and
• calculating the track pitch errors as a function of the one track pitch delta drive signal values and the two track pitch delta drive signal values;
• determining a gain constant of the servo system;
• calculating as a function of the track pitch error values and the gain constant, and storing, PES correction offsets representative of the magnitudes of positioner drive signals causing the positioner to drive the head assembly distances sufficient to compensate for the track pitch errors;
• and
• summing the PES correction offsets with the PES while operating the servo system in closed-loop mode to cause the servoing read gap to be servo locked to the desired centerlines of the servo tracks.