US 5,377,058 A · Fly height servo control of read/write head suspension

Abstract

The fly height of read/write heads in multiple disk drives is dynamically adjusted to optimum fly height by a servo loop. The fly height is sensed in real time with a harmonic ratio fly height detector and compared to an optimum or reference fly height. The suspension system of each head is adjusted in accordance with the departure of the fly height of that head from the optimum fly height. The adjustment of the suspension system is accomplished by bonding a piezoelectric film to the flexible suspension arm carrying each head. The fly height is corrected for both radial and circumferential error as the head changes radial and circumferential position relative to the disk surface. The reference fly height, to which each head is moved by the servo loop, may be selectively changed in the fly height servo operation. This can be done to lift the heads away from the disk surface during track seek mode or disk drive sleep mode. The reference fly height can also be changed to lower the heads towards the disk surface during error recovery mode.

Claims18

Dependent claims

In a disk drive having a read/write head, that aerodynamically flies above the recording disk surface, and an actuator arm for moving a read/write head from recording track to recording track on a recording disk surface, apparatus for dynamically controlling the fly height of each head above the disk surface while the head is flying along a data track reading a signal recorded at the data track, said apparatus comprising:

suspension means connected between the arm and the head for flexibly suspending the head above the disk surface and pushing on the head with a spring force against the aerodynamic lift force of the head;
said head reading the recorded signal in the data track and providing a read signal;
means for detecting from the read signal a current fly height of the head above the disk surface at the same time and location where said head is reading the recorded signal;
means :for comparing the current fly height of the head to a reference fly height and generating a fly height error signal indicative of the difference between the current fly height and the reference fly height;
and
means responsive to the fly height error signal for controlling the spring force provided by said flexible suspension means to adjust the fly height of the head to the reference fly height at the same time and location where the head is reading the recorded signal and flying along the track.

3 more elements

Fly-height servo-loop apparatus in a disk drive for controlling the fly height of a read/write head as the head flies aerodynamically above a data track on the surface of a recording disk, said data track having a plurality of sectors and said head moved between data tracks by an actuator arm, said apparatus comprising:

suspension means connected between said head and said actuator arm for flexibly suspending the head above the surface of the disk, said suspension means providing a spring force that acts against the aerodynamic lift force of the head as the head flies along the track;
said head for or reading a sector signal recorded in at least a portion of each sector of the data track.;
means responsive to the sector signal read by said head for measuring the actual fly height of the head at a sector location on the data track where said head is reading the sector signal as the head flies along the track on the disk surface;
means for calculating the difference between a predetermined reference fly height and the actual fly height to produce a fly height error signal;
and
means responsive to said calculating means for bending said suspension means to adjust the spring force of the suspension on the head until the fly height error signal is reduced to zero whereby the head is controlled to fly at the reference fly height while the sector signal is read and the actual fly height is measured.

3 more elements

Dependencies are inferred from the claim text.

Fly height servo control of read/write head suspension

Life of this patent

Fly height servo control of read/write head suspension

Life of this patent

Abstract

Claims18