Spindle motor initialization after a control processor reset condition in a disc drive

• US 6,664,749 B2
• Filed: 09/28/2001
• Issued: 12/16/2003
• Est. Priority Date: 04/06/2001
• Status: Expired due to Fees

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Street, David R., Heydt, Jeffrey A.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US09/966,383
• Publication Number:
  US 20020171380A1
• Time in Patent Office: 809 Days
• Field of Search: 318/138, 318/254, 318/375, 318/379, 318/430, 318/431, 318/439, 318/720, 318/721, 318/459, 318/500, 388/928.1
• US Class Current: 318/400.34
• CPC Class Codes: G11B 19/20 Driving; Starting; Stopping; Control thereof

Abstract

Method and apparatus for initializing a disc drive to bring a spindle motor to a final, operational velocity after a disc drive processor reset condition. The spindle motor is rotated using electronic commutation and back electromotive force (bemf) detection. Upon initialization of the disc drive, a control circuit checks for the presence or absence of detected bemf. The absence of bemf indicates the spindle motor is either at rest or is rotating at a relatively low velocity. In the absence of bemf, the electrical rotational position of the spindle motor is determined, a short braking pulse is applied to the motor, and rotation of the spindle motor is detected in relation to changes in the electrical rotational position. Further breaking pulses are applied until no apparent change in electrical rotational position is detected, after which the spindle motor is accelerated from rest to the final, operational velocity.

Claims

1. A method for initializing a disc drive having a spindle motor, back electromotive force (bemf) detection circuitry which detects bemf from rotation of the spindle motor above an intermediate velocity, and commutation circuitry which electrically commutates the spindle motor in relation to the detected bemf over a range of electrical rotational positions, the method comprising steps of:

(a) determining the spindle motor to be either stationary or rotating at a rate below the intermediate velocity in relation to an absence of detected bemf from the spindle motor;

(b) identifying the electrical rotational position of the spindle motor;

(c) applying a braking force to the spindle motor;

(d) subsequently identifying the electrical rotational position of the spindle motor after application of the braking force of step (c); and

(e) determining whether the spindle motor is still rotating in relation to a change between the electrical rotational position identified in step (d) and the electrical rotational position identified m step (b).

2. The method of claim 1, further comprising a step of:

(f) accelerating the spindle motor from rest to a final, operational velocity at which data are transferred from a disc supported by the spindle motor and a host device when no apparent change is detected between the electrical rotational position identified in step (d) and the electrical rotational position identified in step (b).

3. The method of claim 1, further comprising steps of:

(f) when the spindle motor is determined to still be rotating, repeating steps (c) and (d) until no apparent change is detected in the electrical rotational position of the spindle motor; and

(g) accelerating the spindle motor from rest to a final, operational rotational velocity at which data are transferred from a disc supported by the spindle motor and a host device.

4. The method of claim 1, wherein the identifying step (b) comprises steps of:

(b1) sequentially applying a drive pulse to each of a plurality of commutation states respectively corresponding to each of the electrical rotational positions; and

(b2) measuring a corresponding rise time for a resulting voltage induced by application of each said drive pulse, said rise time determined in relation to impedance of the spindle motor determined in turn by the electrical rotational position of the spindle motor.

5. The method of claim 4, wherein the identifying step (d) comprises steps of:

(d1) sequentially applying a drive pulse to each of a selected subset of the commutation states less than the plurality of commutation states; and

(d2) measuring a corresponding rise time for a resulting voltage induced by application of each said drive pulse applied during step (d1).

6. A disc drive, comprising:

a spindle motor configured to rotate at least one recording disc;

a read/write bead configured to write data to the disc and read data from the disc;

back electromotive force (bemf) detection circuitry coupled to the spindle motor and which detects bemf from rotation of the spindle motor above an intermediate velocity;

commutation circuitry coupled to the bemf detection circuitry and spindle motor which electrically commutates the spindle motor in relation to the detected bemf over a range of electrical rotational positions of the spindle motor; and

a control circuit which, upon initialization of the disc drive, determines the presence or absence of detected bemf from the bemf detection circuitry, and in the absence of detected bemf sequentially identifies the electrical rotational position of the spindle motor, directs the application of a braking force to the spindle motor, determines whether the spindle motor is rotating in relation to a change in the electrical rotational position of the spindle motor, and commands an acceleration of the spindle motor to a final, operational velocity by the commutation circuitry when the spindle motor is determined to be at rest, wherein the final, operational velocity is a velocity at which user data are read from the disc and transferred to a host device.

7. The disc drive of claim 6, wherein the control circuit further operates to command the alternating application of additional braking forces to the spindle motor followed by determinations of the electrical rotational position of the spindle motor until the spindle motor is determined to be at rest.

8. The disc drive of claim 6, further comprising spindle driver circuitry coupled to the spindle motor and the commutation circuitry and which applies drive pulses to each of a plurality of windings of the spindle motor in response to commutation pulses from the commutation circuitry to rotate the spindle motor, wherein the control circuit identifies the electrical rotational position of the spindle motor by directing the spindle driver to sequentially apply a drive pulse to each of a plurality of windings of the spindle motor and measuring a corresponding rise time for a resulting voltage induced by inductance of said windings in relation to the electrical rotational position of the spindle motor.

9. The disc drive of claim 8, wherein the spindle driver circuitry comprises:

a sense resistor connected in series between the plurality of windings of the spindle motor and ground; and

a comparator having a positive input and a negative input the positive input connected in parallel with the sense resistor to receive a motor sense voltage and the negative input connected to receive a reference threshold voltage, wherein the comparator outputs a pulse when the motor sense voltage reaches the reference threshold voltage, and wherein the control circuit determines the rise time in relation to the pulse output by the comparator.

10. The disc drive of claim 6, wherein the control circuit comprises control logic coupled to the commutation circuitry and the bemf detection circuitry, and a top level programmable processor coupled to the control logic and which father directs the transfer of data between the disc and the host device.

11. A disc chive, comprising:

a spindle motor configured to rotate at least one recording disc;

a read/write head configured to write data to the disc and read data from the disc;

back electromotive force (bemf) detection circuitry coupled to the spindle motor and which detects bemf from rotation of the spindle motor above an intermediate velocity;

commutation circuitry coupled to the bemf detection circuitry and spindle motor which electrically commutates the spindle motor in relation to the detected bemf over a range of electrical rotational positions of the spindle motor; and

means for initializing the disc drive to bring the spindle motor to a final, operational rotational velocity at which user data are transferred between the disc and a host device alter determining that the spindle motor is either at rest or rotating at a rotational velocity less than the intermediate velocity due to an absence of detected bemf from the spindle motor, by identifying the electrical rotational position of the spindle motor, applying a braking force to the spindle motor, and detecting a change in the electrical rotational position of spindle motor after application of the braking force.

12. The disc drive of claim 11, wherein the means for initializing comprises control logic coupled to the commutation circuitry and the bemf detection circuitry, and a top level programmable processor coupled to the control logic and which further directs the transfer of data between the disc and the host device.

13. A method, comprising:

detecting an absence of sensed rotation from a motor;

sequentially identifying a first electrical rotational position of the motor, applying a braking force to the motor and identifying a second electrical rotational position of the motor; and

determining the motor to be in the stopped condition or in the low speed rotation condition in relation to the first and second electrical rotational positions.

14. The method of claim 13, wherein the detecting step comprises detecting an absence of rotation induced back electromotive force (bemf) from a motor indicative of a stopped condition or a low speed rotation condition of the motor.

15. The method of claim 13, wherein the applying a braking force step comprises electrically shorting at least two phases of the motor for a selected period of time.

16. The method of claim 13, further comprising repeating the sequentially identifying step when the determining step determines the motor to be in the low speed rotation condition.

17. The method of claim 13, further comprising accelerating the motor to an operational velocity when the determining step determines the motor to be in the stopped condition.

18. The method of claim 13, wherein the first electrical rotational position is identified by steps comprising sequentially applying a drive pulse to each of a plurality of commutation states respectively corresponding to each of the electrical rotational positions, and measuring a corresponding rise time for a resulting voltage induced by application of each said drive pulse, said rise time determined in relation to impedance of the motor determined in turn by the electrical rotational position of the motor.

19. The method of claim 18, wherein the second electrical rotational position is identified by steps comprising sequentially applying a drive pulse to each of a selected subset of the commutation states less than the plurality of commutation states, and measuring a corresponding rise time for a resulting voltage induced by application of each said drive pulse applied to the selected subset of the commutation states.

20. The apparatus of claim 13, wherein the motor is characterized as a spindle motor in a data storage device configured to rotate a data storage medium.

21. An apparatus, comprising:

a rotatable motor, and

a motor control circuit which detects an absence of sensed rotation from the motor, sequentially identifies a first electrical rotational position of the motor, applies a braking force to the motor and identifies a second electrical rotational position of the motor, and then determines the motor to be in a stopped condition or in a low speed rotation condition in relation to the first and second electrical rotational positions.

22. The apparatus of claim 21, wherein the motor control circuit detects the absence of sensed rotation from the motor in relation to an absence of rotation induced back electromotive force (bemf) from the motor.

23. The apparatus of claim 21, wherein the motor control circuit applies a braking force by electrically shorting at least two phases of the motor for a selected period of time.

24. The apparatus of claim 21, wherein the motor control circuit further accelerates the motor to an operational velocity when the motor is determined to be in the stopped condition.

25. The apparatus of claim 21, wherein the motor control circuit identifies the first electrical rotational position by sequentially applying a drive pulse to each of a plurality of commutation states respectively corresponding to each of the electrical rotational positions, and measuring a corresponding rise time for a resulting voltage induced by application of each said drive pulse, said rise time determined in relation to impedance of the motor determined in turn by the electrical rotational position of the motor.

26. The apparatus of claim 25, wherein the motor control circuit identifies the second electrical rotational position by sequentially applying a drive pulse to each of a selected subset of the commutation states less than the plurality of commutation states, and measuring a corresponding rise time for a resulting voltage induced by application of each said drive pulse applied to the selected subset of the commutation states.

27. The apparatus of claim 21, wherein the motor is characterized as a spindle motor in a data storage device configured to rotate a data storage medium.