Estimation and control of head fly height

1. A method of controlling head fly height comprising:

estimating fly height clearance between a head and a data storage media in response to heater signal levels applied to a heater element to heat the head;

generating a repository of calibrated fly height values for a range of heater signal levels applied to the heater element to heat the head and for a range of ambient air temperatures, wherein the fly height is estimated in response to the repository of calibrated fly height values, a present level of the heater signal applied to the heater element, and a present air temperature; and

regulating heating of the head by the heater element in response to the estimated fly height.

2. The method of claim 1 , wherein:

the fly height clearance is further estimated based on a combination of an estimate of head fly height at a sensed air temperature, an estimate of head pole-tip-protrusion from head heating from writing data, and an estimate of head pole-tip-protrusion from head heating by the heater element;

the estimate of head pole-tip-protrusion from head heating from writing data is based on the following equation:

PTP W ( k )= A 1 (α 1 (1− e (−kT/τ 1 ) )+(1−α 1 )(1− e (−kT/τ 2 ) )),

 where PTP w (k) represents the head pole-tip-protrusion at time k, T represents a servo spoke location of the head, A 1 represents amplitude of pole-tip-protrusion over an operable range of writing-induced heating,α 1 represents a gain factor, and τ 1 and τ 2 are time constants indicative of the rate of change of pole-tip-protrusion in response to writing data through the head; and

the estimate of head pole-tip-protrusion from head heating by the heater element is based on the following equation:

PTP H ( k )= A 2 (α 2 (1− e (−kT/τ 3 ) )+(1−α 2 )(1− e (−kT/τ 4 ) )),

 where PTP H (k) represents the head pole-tip-protrusion at time k, T represents a servo spoke location of the head, A 2 represents amplitude of pole-tip-protrusion over an operable range of heating by the heater element, α 2 represents a gain factor, and τ 3 and τ 4 are time constants indicative of rate of change of pole-tip-protrusion in response to a heater signal applied to the heater element.

3. A method of controlling head fly height comprising:

estimating fly height clearance between a head and a data storage disk in response to heater signal levels applied to a heater element to heat the head;

generating a repository of calibrated fly height values for a range of heater signal levels applied to the heater element to heat the head and at a plurality of radial locations across the disk, wherein the fly height is estimated in response to the repository of calibrated fly height values, a present level of the heater signal applied to the heater element, and a radial location on the disk where data is to be written/read by the head; and

regulating heating of the head by the heater element in response to the estimated fly height.

4. A method of controlling head fly height comprising:

estimating fly height clearance between a head and a data storage media in response to heater signal levels applied to a heater element to heat the head;

regulating the heater signal to increase heating by the heater element in response to the estimated fly height exceeding an upper target threshold;

regulating the heater signal to decrease heating by the heater element in response to the estimated fly height being less than a lower target threshold;

inhibiting writing and/or reading through the head in response to the estimated fly height being less than a lower operational threshold; and

inhibiting writing through the head in response to the estimated fly height being greater than an upper operational threshold.

5. The method of claim 4 , wherein writing is inhibited in response to a first lower operational threshold and reading is inhibited in response to a second lower operational threshold that is different than the first lower operational threshold.

6. A method of controlling head fly height comprising:

estimating fly height clearance between a head and a data storage media in response to heater signal levels applied to a heater element to heat the head;

in response to selection of a head for reading/writing on the media, regulating a heater signal to increase heating by the heater element until the estimated fly height is less than an upper target threshold; and

enabling writing of data through the head onto the media in response to the estimated fly height becoming less than a write gate upper limit.

7. A method of controlling head fly height comprising:

estimating fly height clearance between a head and a data storage media by measuring duty cycle of writing of a data segment on the media, decreasing the fly height estimate in response to increased duty cycle, and increasing the fly height estimate in response to decreased duty cycle; and

regulating heating of the head by a heater element in response to the estimated fly height.

8. The method of claim 7 , wherein the fly height is estimated in response to length of a data segment that is about to be written through the head.

9. A circuit comprising:

a fly height controller that estimates fly height clearance between a head and a data storage media in response to a present heater signal level applied to a heater element to heat the head, a present air temperature, and a repository of calibrated fly height values for a range of heater signal levels and for a range of ambient air temperatures, and that regulates heating of the head by the heater element in response to the estimated fly height.

10. The circuit of claim 9 , wherein the fly height controller estimates fly height based on a combination of an estimate of head fly height at a sensed air temperature, an estimate of head pole-tip-protrusion from head heating from writing data, and an estimate of head pole-tip-protrusion from head heating by the heater element.