Voice coil driven positioner for coarse and fine positioning of magnetic head in multi-track tape drive

A voice-coil based positioning system comprising:

• (a) a movable voice-coil having a tubular shape, where said tubular shape includes inner and outer bounds;
• (b) a stator for generating a flux field passing through the voice-coil;
• (c) voice-coil drive means for delivering a current to the voice-coil to thereby generate a magnetic motive force that moves the voice-coil;
• and
• (d) position determining means for determining the position of the movable voice-coil, said position determining means having a movable first position determining means and a stationary second position determining means,
• (d.1) wherein the movable first position determining means includes a permanent magnet that is coupled to the movable voice-coil for moving with the voice-coil,
• (d.2) wherein the movable first position determining means is positioned within the inner bounds of the tubular shape of the voice-coil,
• (d.3) wherein the stationary second position determining means is positioned within a region that is bounded by a path traveled by the inner bounds of the tubular shape of the voice-coil;
• and
• (d.4) wherein the stationary second position determining means is operatively coupled to the movable first position determining means for detecting the position of the movable voice-coil relative to the stationary second position determining means.

A voice-coil based positioning system comprising:

• (a) a movable voice-coil having a tubular shape;
• (b) a stator assembly for generating a flux field passing through the voice-coil;
• (c) voice-coil drive means for driving a current through the voice-coil to thereby apply a motive force to the voice-coil and move the voice-coil;
• (d) a movable magnet coupled to the movable voice-coil for moving with the voice-coil, said movable magnet being positioned within the tubular shape of the voice-coil;
• (e) magnetic field sensing means positioned within a region bounded by a path of travel of the tubular shape of the voice-coil, the magnetic field sensing means having a Hall-effect device magnetically coupled to the movable magnet for detecting the position of the movable magnet relative to the magnetic field sensing means.

A method for making and calibrating a positioning system comprising the steps of:

• (a) providing a voice coil reciprocally disposed in a magnetic stator structure, the voice coil moving relative to the stator structure in response to the application of electrical current through the voice coil;
• (b) providing a programmable measurement means for measuring movement of the voice coil relative to the stator structure, said measurement means including a permanent magnet coupled to the voice coil, the output of the measurement means being defined by a programmable table look-up means included in the programmable measurement means;
• (c) removably attaching a precision measurement means to the voice coil for precisely measuring the position of the voice coil relative to the stator structure;
• (d) applying current to the voice coil to move the voice coil to a precision position as determined by the precision measurement means;
• and
• (e) programming the programmable table look-up means to output a signal representing said position while said current is applied to the voice coil.

A load positioning apparatus for providing coarse and fine positioning of a load, said apparatus comprising:

• (a) a voice-coil having a hollow defined in an interior portion thereof;
• (b) a stator assembly for generating a flux field passing through the voice-coil;
• (c) a movable carriage supporting the voice coil and further adapted for supporting the load;
• (d) a guide rail operatively coupled to the movable carriage for guiding the movable carriage along a predefined guide path that allows the carriage to carry the load to predefined positions and that further carries the voice-coil through the flux field generated by the stator assembly;
• (e) a carriage position measuring mechanism for measuring the position of the carriage relative to a reference frame and outputting a corresponding measurement signal;
• wherein the carriage position measuring mechanism includes:
• (e.1) a first position measuring part coupled to the carriage so as to move with the carriage, said first position measuring part having a permanent magnet situated within the hollow of the voice-coil;
• and
• (e.2) a second position measuring part for magnetically detecting the position of the permanent magnet relative to the second position measuring part, the second position measuring part being situated in a region traversed by the hollow of the voice-coil;
• and
• (f) a coil driving circuit that is responsive to the measurement signal of the carriage position measuring mechanism and to supplied, coarse and fine position-control signals, the coil driving circuit outputting a responsive drive current to the voice-coil for respective coarse and fine positioning of said load.