Position identification for a coarse actuator portion of a compound actuator

A servo system for positioning a head laterally with respect defined servo tracks, comprising:

• a servo sensor and detector for sensing lateral position of said head with respect to said defined servo tracks;
• a compound actuator having a fine actuator portion for translating said head laterally with respect to said defined servo tracks, and a coarse actuator portion for translating said fine actuator portion laterally with respect to said defined servo tracks;
• and
• a position control coupled to said servo sensor and detector and coupled to said compound actuator for operating said compound actuator to position said actuator portions, said position control:
• providing position indications for said coarse actuator portion comprising predetermined nominal lateral position indications with respect to said defined servo tracks;
• positioning said coarse actuator portion at an estimated position with respect to said defined servo tracks;
• upon said positioning, responding to said servo sensor to determine which said servo track is closest to said estimated position;
• and
• setting said coarse actuator portion position indication to said predetermined nominal lateral position indication of said determined defined servo track.

In a servo system for positioning a head laterally with respect to defined servo tracks, said servo system comprising a servo sensor and detector for sensing lateral position of said head with respect to said defined servo tracks, a compound actuator having a fine actuator portion for translating said head laterally with respect to said defined servo tracks and a coarse actuator portion for translating said fine actuator portion laterally with respect to said defined servo tracks, a servo controller comprising:

• a servo input coupled to said servo sensor and detector;
• a servo signal output for operating said compound actuator to position said actuator portions;
• and
• a position control coupled to said servo input and to said servo signal output, said position control:
• providing position indications for said coarse actuator portion comprising predetermined nominal lateral position indications with respect to said defined servo tracks;
• providing servo signals at said servo signal output to position said coarse actuator portion at an estimated position with respect to said defined servo tracks;
• upon said positioning, responding to said servo sensor and detector at said servo input to determine which said servo track is closest to said estimated position;
• and
• setting said coarse actuator portion position indication to said predetermined nominal lateral position indication of said determined defined servo track.

A magnetic tape data storage drive for transferring data with respect to a magnetic tape, said magnetic tape having a plurality of parallel defined servo tracks extending in the longitudinal direction of said magnetic tape, comprising:

• a magnetic tape head for transferring data with respect to said magnetic tape;
• a tape drive system for moving a magnetic tape in said longitudinal direction past said magnetic tape head;
• a servo sensor and detector for sensing lateral position of said magnetic tape head with respect to said defined servo tracks;
• a compound actuator having a fine actuator portion for translating said magnetic tape head laterally with respect to said defined servo tracks, and a coarse actuator portion for translating said fine actuator portion laterally with respect to said defined servo tracks;
• and
• a position control coupled to said servo sensor and detector for operating said compound actuator to position said actuator portions, said position control:
• providing position indications for said coarse actuator portion comprising predetermined nominal lateral position indications with respect to said defined servo tracks;
• positioning said coarse actuator portion at an estimated position with respect to said defined servo tracks;
• upon said positioning, responding to said servo sensor and detector to determine which said defined servo track is closest to said estimated position;
• and
• setting said coarse actuator portion position indication to said predetermined nominal lateral position indication of said determined defined servo track.