Rotational vibration detection using spindle motor velocity sense coils

• US 6,222,336 B1
• Filed: 04/30/1999
• Issued: 04/24/2001
• Est. Priority Date: 06/05/1998
• Status: Expired due to Term

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Douglas, D. Brent, McKenzie, Lealon R.
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US09/302,586
• Time in Patent Office: 725 Days
• Field of Search: 318/448, 318/460, 318/126, 318/127, 318/128, 318/611, 318/623, 318/621, 369/43, 369/44.35, 369/44.36, 369/239
• US Class Current: 318/448
• CPC Class Codes: G11B 19/04 Arrangements for preventing, inhibiting, or warning against double recording on the same blank or against other recording or reproducing malfunctions
• CPC Class Codes: G11B 19/28 Speed controlling, regulating, or indicating G11B19/24 takes precedence
• CPC Class Codes: G11B 25/043 using rotating discs
• CPC Class Codes: G11B 33/08 Insulation or absorption of undesired vibrations or sounds

Abstract

An apparatus and method for detecting rotational vibration applied to a disc drive having an actuator supporting a head adjacent a rotatable disc. A spindle motor has a set of driver coils which rotate the disc through electrical commutation, and a set of velocity sense coils which sense the rotational velocity of the motor in relation to voltages established across the sense coils. Rotational vibration is detected in relation to changes in the rotational velocity of the disc. A data transfer operation between the disc and a host device is interrupted when the magnitude of the rotational vibration exceeds an acceptable level. A servo circuit compensates for the application of rotational vibration to the disc drive by adjusting current applied to the actuator in relation to the changes in the rotational velocity of the disc.

Claims

1. A method for detecting application of rotational vibration to a disc drive having a spindle motor with a driver coil and a driver magnet, the spindle motor rotating a data storage disc through controlled application of current to the driver coil to establish a magnetic field which interacts with a magnetic field generated by the permanent magnet, the method comprising steps of:

(a) immersing a velocity sense coil in a magnetic field generated by a permanent magnet of the spindle motor;

(b) generating a motor velocity signal indicative of a rotational velocity of the disc in relation to a voltage induced across the velocity sense coil by relative movement between the velocity sense coil and the magnetic field of the immersing step (a); and

(c) detecting application of rotational vibration to the disc drive in relation to the motor velocity signal.

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

(d) interrupting a data transfer operation between the disc and a host device when a magnitude of the rotational vibration applied to the disc drive exceeds an acceptable level.

3. The method of claim 2, wherein the disc drive further has a head controllably positionable adjacent a surface of the disc through application of current to an actuator coil, and wherein the method further comprises a step of:

(e) controlling the application of current to the actuator coil in relation to the motor velocity signal.

4. The method of claim 2, wherein the detecting step (c) further comprises steps of:

(c1) obtaining a velocity error signal indicative of error in rotational velocity of the disc, wherein a magnitude of the current applied to the driver coil is adjusted in relation to the velocity error signal; and

(b2) determining a rotational vibration velocity signal in relation to the velocity error signal and the motor velocity signal, the rotational vibration velocity signal indicative of rotational velocity imparted to the disc by the application of rotational vibration to the disc drive.

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

(d1) comparing a magnitude of the rotational vibration velocity signal to a predetermined threshold; and

(d2) interrupting the data transfer operation when the magnitude of the rotational vibration velocity signal exceeds the predetermined threshold.

6. The method of claim 1, wherein the sense coil is disposed proximate the driver coil, and wherein the permanent magnet of the immersing step (a) comprises the driver magnet so that both the driver coil and the sense coil are immersed in the magnetic field generated by the driver magnet.

7. The method of claim 1, wherein the driver coil is one of a set of driver coils to which currents are applied to rotate the disc, and wherein the sense coil is one of a set of separate sense coils which output voltage signals which are rectified to generate the motor velocity signal.

8. A spindle motor operably configured to rotate a disc in a disc drive, comprising:

a plurality of circumferentially extending driver magnets;

a set of driver coils which rotate the disc when electrical currents are applied to the driver coils, wherein the electrical currents establish magnetic fields which interact with magnetic fields established by the driver magnets; and

a separate set of sense coils which output a set of voltages indicative of rotational velocity of the disc to detect application of rotational vibration to the disc drive.

9. The spindle motor of claim 8, wherein the sense coils are disposed proximate the driver coils and immersed in the magnetic fields established by the driver magnets.

10. The spindle motor of claim 8, further comprising a plurality of circumferentially extending sense magnets separated from the driver magnets, wherein the sense coils are immersed in magnetic fields established by the sense magnets.

11. A disc drive, comprising:

a spindle motor which controllably rotates a data storage disc and comprises;

a plurality of circumferentially extending driver magnets;

a set of driver coils which rotate the disc when electrical currents are applied to the driver coils, wherein the electrical currents establish magnetic fields which interact with magnetic fields established by the driver magnets; and

a separate set of sense coils which output a set of voltages indicative of rotational velocity of the disc;

a spindle motor driver circuit which applies the electrical currents to the set of driver coils and outputs a velocity error signal indicative of error in rotational velocity of the disc, wherein the spindle motor driver circuit adjusts the electrical currents in relation to the velocity error signal;

a spindle velocity sense circuit which generates a motor velocity signal indicative of the velocity of the spindle motor in response to the set of voltages output by the set of sense coils; and

a processor having associated programming to detect application of rotational vibration to the disc drive in relation to the velocity error signal and the motor velocity signal.

12. The disc drive of claim 11, wherein the processor obtains a rotational vibration velocity signal in relation to a difference between the velocity error signal and the motor velocity signal, and wherein the processor interrupts transfer of data between the disc and a host device when a magnitude of the rotational vibration velocity signal exceeds a predetermined threshold.

13. The disc drive of claim 11, further comprising:

an actuator comprising a head supported adjacent the disc and a coil of an actuator motor; and

a servo circuit, operably coupled to the head and the actuator motor, which applies current to the coil to position the head relative to the disc, wherein the servo circuit compensates for the application of rotational vibration to the disc drive by adjusting the current applied to the coil in relation to the motor velocity signal.

14. The disc drive of claim 11, wherein the spindle velocity sense circuit rectifies the set of voltages output by the set of sense coils to generate the motor velocity signal.