Patent Application
20100149682
1. Field of the Invention
The present invention relates to determining a pitch and roll of a head in a hard disk drive.
2. Background Information
Hard disk drives contain a plurality of magnetic heads that are coupled to rotating disks. The heads write and read information by magnetizing and sensing the magnetic fields of the disk surfaces. Each head is attached to a flexure arm to create a subassembly commonly referred to as a head gimbal assembly (“HGA”). The HGA's are suspended from an actuator arm. The actuator arm has a voice coil motor that can move the heads across the surfaces of the disks.
During operation, each head is separated from a corresponding disk surface by an air bearing. The air bearing eliminates mechanical interference between the head and the disks. The strength of the magnetic field from the disk is inversely proportional to the flying height of the head relative to the disk. Reduced spacing results in a stronger magnetic field on the disk, and vice versa.
The flying height of a head is a function of a pitch and roll of the head body. It is desirable to determine the pitch and roll of the head during operation to insure proper head stability. Understanding pitch and roll is particularly important for small flying heights on the order of a few nanometers. Pitch and roll can be determined by attaching a sensor, such as a piezoelectric transducer, to the flexure arm of the HGA. Data from such a sensor may not be entirely accurate.
A head for a hard disk drive that includes a primary read element and a first sensor read element coupled to a head body. The first sensor read element is offset from the primary read element.
Disclosed is a head for a hard disk drive that includes a primary read element and a first sensor read element coupled to a head body. The first sensor read element is offset from the primary read element. The first sensor read element provides a read signal that can be analyzed to determine a pitch of the head. The head may also have a second sensor read element that is offset from the first sensor read element. Read signals of the first and second sensor read elements can be analyzed to determine a roll of the head. The read elements can be embedded into the head body to place the elements in close proximity to the flying height of the head.
Referring to the drawings more particularly by reference numbers,
The disk drive 10 may include a plurality of heads 20 located adjacent to the disks 12. As shown in
Each head may also have a first sensor read element 24 and a second sensor read element 26. The first and second sensor read elements 24 and 26 can each provide a read signal that is analyzed to determine certain characteristics of the head such as pitch, roll and flying height. The sensor read elements 24 and 26 are offset from the primary read element 22 along a length of the head 20. This offset allows for the determination of a head pitch. The read signals from the first and second read sensor elements 24 and 26 can be analyzed to determine a roll of the head. The position of the two read sensors from a longitudinal center line CL may be equally spaced to minimize the complexity in determining the head pitch and roll. The first and second sensor read elements 24 and 26 may be equally spaced from a longitudinal center line CL so that read signals from the elements can be analyzed to determine a roll of the head.
As shown in
Referring to
The hard disk drive 10 may include a printed circuit board assembly 44 that includes a plurality of integrated circuits 46 coupled to a printed circuit board 48. The printed circuit board 46 is coupled to the voice coil 38, heads 20 and spindle motor 14 by wires (not shown).
The read/write channel circuit 58 is connected to a controller 64 through read and write channels 66 and 68, respectively, and read and write gates 70 and 72, respectively. The read gate 70 is enabled when data is to be read from the disks 12. The write gate 72 is to be enabled when writing data to the disks 12. The controller 64 may be a digital signal processor that operates in accordance with a software routine, including a routine(s) to write and read data from the disks 12. The read/write channel circuit 62 and controller 64 may also be connected to a motor control circuit 74 which controls the voice coil motor 36 and spindle motor 14 of the disk drive 10. The controller 64 may be connected to a non-volatile memory device 76. By way of example, the device 76 may be a read only memory (“ROM”) that contains instructions that are read by the controller 64.
The controller 64 can analyze read signals from the read elements 22, 24 and 26 to determine different fly characteristics of the heads. For example, the read signals provided by one or both sensor read elements and primary read element can be analyzed to determine the pitch of the head. The read signals from both sensor read elements, and/or one or both of the sensor read elements and the primary read element can be analyzed to determine a roll of the head. For example, the roll may be the difference between the two flying heights of the sensor read elements. Likewise, the pitch may be determined from the difference of the flying heights between the primary read element and one or both of the sensor read elements. A change in pitch can also be used to determine an altitude of the drive. Each of the read elements is preferably calibrated to determine the absolute flying height of each element.
While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art.
