Early warning offtrack collision system for hard disk drives

A hard disk drive comprising:

• a recording head configured to write data in data tracks on a spinning magnetic recording disk;
• and
• controller electronics coupled to the recording head for controlling writing data, the controller electronics configured to:
• measure and record a first position error signal that exceeds a squeeze threshold set for detecting adjacent track squeeze events, the first position error signal associated with a first sector on a first track of the spinning magnetic recording disk;
• while data is being written at a second sector on a second track adjacent to the first sector on the first track, generate a predicted position error signal for a next sector on the second track;
• compare a difference between the predicted position error signal and the first position error signal to a squeeze limit;
• and
• responsive to comparing the difference to the squeeze limit, control the recording head to write the next sector on the second track when the difference is not greater than the squeeze limit, and otherwise set a squeeze event flag that prevents writing the next sector until the squeeze event flag is cleared,
• wherein the controller electronics are further configured to implement a servo control system that prevents data writes when a current position error signal exceeds an on-cylinder limit, the on-cylinder limit being greater than the squeeze threshold.

A method for use in a hard disk drive, the hard disk drive having data recorded in sectors arranged in tracks, the method comprising:

• measuring and recording a first position error signal that exceeds a squeeze threshold set for detecting adjacent track squeeze events, the first position error signal associated with a first sector on a first track;
• while writing data at a second sector on a second track adjacent to the first sector on the first track, generating a predicted position error signal for a next sector on the second track;
• comparing a difference between the predicted position error signal and the first position error signal to a squeeze limit;
• responsive to comparing the difference to the squeeze limit, writing the next sector on the second track when the difference is not greater than the squeeze limit, otherwise setting a squeeze event flag and preventing writing the next sector until the squeeze event flag is cleared;
• and
• determining for any position error signal that exceeds the squeeze threshold whether that position error signal is associated with a single-sided squeeze event or a double-sided squeeze event.