Servo control in tape drives

A tape drive, comprising:

• a read/write head for reading and writing data on magnetic tape having at least one servo track for providing transverse position information;
• a drive system for effecting movement of the tape relative to the read/write head;
• at least two servo readers associated with the read/write head, each arranged for reading said at least one servo track during read/write operations, the servo readers being operative concurrently to generate respective servo read signals;
• a position estimator for processing each servo read signal to generate a series of position values, corresponding to respective time instants, indicative of transverse position of the associated servo reader;
• a servo controller for calculating from said position values and time instants (i) a skew value, indicative of tape skew relative to the read/write head, and (ii) a tension variation value indicative of variation of tape tension from a reference value, wherein the servo controller is adapted to account for cross-coupling between tape skew and tension variation in calculating the skew and tension variation values;
• a tension adjustment mechanism for adjusting tape tension in dependence on said tension variation value;
• and
• a skew adjustment mechanism for adjusting tape skew relative to the read/write head in dependence on said skew value.

A servo control method for a tape drive having a read/write head for reading and writing data on magnetic tape with at least one servo track for providing transverse position information, the method comprising the steps of:

• reading at least one said servo track during read/write operations concurrently with at least two servo readers associated with the read/write head to generate respective servo read signals;
• processing each servo read signal to generate a series of position values, corresponding to respective time instants, indicative of transverse position of the associated servo reader;
• and
• calculating from said position values and time instants (i) a skew value, indicative of tape skew relative to the read/write head, and (ii) a tension variation value indicative of variation of tape tension from a reference value;
• and
• accounting in said calculating step for cross-coupling between tape skew and tension variation.