Method and apparatus for calibrating piezoelectric driver in dual actuator disk drive

• US 6,975,123 B1
• Filed: 12/20/2001
• Issued: 12/13/2005
• Est. Priority Date: 12/20/2000
• Status: Expired due to Fees

• Current Assignee: Maxtor Corporation (Seagate Technology Holdings Plc)
• Original Assignee: Maxtor Corporation (Seagate Technology Holdings Plc)
• Inventors: Malang, Keith, Hutsell, Larry
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Lair, Donald M.
• Application Number:
  US10/028,068
• Time in Patent Office: 1,454 Days
• Field of Search: 324/212, 324/727, 324/658, 360/77.16, 360/291.9, 360/292, 360/294.4, 360/294.5
• US Class Current: 324/658
• CPC Class Codes: G11B 5/5552 using fine positioning means for track acquisition separate from the coarse (e.g. track changing) positioning means
• CPC Class Codes: G11B 5/59627 Aligning for runout, eccentricity or offset compensation G11B5/5534, G11B5/59677, G11B5/59688 take precedence

Abstract

A method and apparatus are disclosed which are operable to determine a capacitance associated with at least one piezoelectric element in an dual actuator disk drive. The capacitance information is used to adjust a driver used to drive the piezoelectric element. Capacitance is determined by supplying a predetermined current into the piezoelectric element(s) for a predetermined time period. A voltage associated with the piezoelectric element(s) is measured following the predetermined time period. The capacitance of the piezoelectric element(s) is then calculated based on the measured voltage, the current supplied, and the predetermined time period.

Claims

1. A method for calibrating a driver in a dual actuator disk drive, comprising:

determining a measured capacitance associated with at least one piezoelectric element prior to positioning the piezoelectric element over a disk surface including the steps of;

driving said at least one piezoelectric element to a predetermined starting voltage;

supplying a predetermined current to said at least one piezoelectric element for a predetermined time period;

measuring a second voltage associated with said at least one piezoelectric element after said supplying step; and

calculating said measured capacitance based on said measuring step, wherein said calculating step is performed based on the following equation;

C=I*(T/(V_m2−

V_m1)

 

where C is the measured capacitance, I is the current supplied to said at least one piezoelectric element during said supplying step, T is the predetermined time period;

V_m2 is the second voltage, and V_m1 is the starting voltage; and

adjusting said driver based on said determining step.

2. A method, as claimed in claim 1, further comprising:

secondly determining a second measured capacitance associated with said at least one piezoelectric element after a predetermined time period following said adjusting step; and

secondly adjusting said driver based on said determining step.

3. A method, as claimed in claim 1, wherein said adjusting step includes:

determining a difference between said measured capacitance and an expected capacitance; and

adjusting a gain associated with said driver based on said determining step.

4. A method, as claimed in claim 1, wherein said driver is a voltage control driver.

5. A method, as claimed in claim 1, wherein said driver is a charge control driver.

6. A method for calibrating a driver in a dual actuator disk drive, comprising:

determining a measured capacitance associated with at least one piezoelectric element prior to positioning the piezoelectric element over a disk surface including the steps of;

driving said at least one piezoelectric element is a predetermined starting voltage;

supplying a predetermined current to said actuator element;

starting a timer;

monitoring a voltage associated with said at least one piezoelectric element;

stopping said timer to get an elapsed time when said voltage reaches a predetermined voltage level in said monitoring step; and

calculating said measured capacitance based on said elapsed time, wherein said calculating step is performed based on the following equation;

C=I*(T/(V_m2−

V_m1)

 

where C is the measured capacitance, I is the current supplied to said at least one piezoelectric element during said supply step, T is the elapsed time, V_m2 is the predetermined voltage level, and V_m1 is the starting voltage; and

adjusting said driver based on said determining step.

7. A method for determining a number of piezoelectric elements present in a dual actuator hard disk drive, comprising:

determining a total capacitance associated with at least one piezoelectric element including the steps of;

driving said at least one piezoelectric element is a predetermined starting voltage;

supplying a predetermined current to said at least one piezoelectric element for a predetermined time period;

measuring a second voltage associated with said at least one piezoelectric element after said supplying step; and

calculating said total capacitance based on said measuring step, wherein said calculating step is performed based on the following equation;

C=I*(T/(V_m2−

V_m1)

 

where C is the total capacitance, I is the current supplied to said at least one piezoelectric element during said supplying step, T is the predetermined time period;

V_m2 is the second voltage, and V_m1 is the starting voltage;

ascertaining a number of piezoelectric elements present in said disk drive based on said determining step.

8. A method for determining a number of piezoelectric elements present in a dual actuator hard disk drive, comprising:

determining a total capacitance associated with at least one piezoelectric element

ascertaining a number of piezoelectric elements present in said disk drive based on said determining step, wherein said ascertaining step comprises;

dividing said total capacitance by an expected capacitance and rounding to the closest natural number.

9. A method, as claimed in claim 8, wherein said expected capacitance is approximately a capacitance associated with a single piezoelectric element.