WO1997036361B1 - Active electromagnetic damping system for spindle motors - Google Patents

Abstract

A method of damping resonances in a rotating system is disclosed, which includes developing a representation of vibrating movement in the rotating system, taking the derivative of that representation and applying an out-of-phase active damping force based on the derivative to the rotating system to damp out the movement.

Claims

AMENDED CLAIMS

[received by the International Bureau on 25 September 1997 (25.09.97); original claims 1 , 4, 5, 14-16, 19 and 21 amended; original claims 2 and 3 cancelled, remaining claims unchanged (5 pages)]

1. A method of damping resonances in a rotating system comprising a spindle

motor having a central shaft defining the central, rotational axis ofthe system and supporting at least one disc which is subject to said undamped vibrating movement; developing a representation of vibrating movement in the rotating system;

taking the derivative of that representation;

applying an out-of-phase active, radial damping force based on said derivative to said

rotating system to damp out said movement.

4. A method as claimed in claim 1 wherein the vibrating movement is defined as a function of two angular rotations α and β which are radial and orthogonal to one another.

5. A method as claimed in claim 14 wherein the vibrating movement is defined as a function of two angular rotations α and β which are radial and orthogonal to one another.

6. A method as claimed in claim 4 wherein said active damping system introduces two radial damping forces which are proportional to the derivatives ofthe angular rotation α and β.

7. A method as claimed in claim 5 wherein said active damping system introduces two radial damping forces which are proportional to the derivatives ofthe angular rotation α and β 8. A method as claimed in claim 6 wherein the radial damping forces are applied to said central shaft below said discs.

9. A method as claimed in claim 7 wherein the radial damping forces are applied to said central shaft below said discs.

10. A method as claimed in claim 8 wherein the central shaft is supported on upper

and lower bearings, and a center of mass ofthe system is defined between the bearings.

1 1. A method as claimed in claim 9 wherein the central shaft is supported on upper and lower bearings, and a center of mass ofthe system is defined between the bearings

12. A method as claimed in claim 10 wherein said central shaft supports a rotor

magnet which rotates with said shaft, said radial active damping forces being applied to said shaft

13. A method as claimed in claim 11 wherein said central shaft supports a rotor magnet which rotates with said shaft, said radial active damping forces being applied to said shaft.

14. A method of micropositioning ofthe spin axis or damping mechanical vibration

in a rotating system comprising a spindle motor having a central shaft defining a central rotational axis

of the spindle motor corresponding to said spin axis applying a rotating force vector created by an

actuator and controlled by the position ofthe spin axis as measured by a sensing device, wherein: a) the force being in phase quadrature with respect to the measured position or displacement of said spin axis; and b) the force being proportional to the velocity of movement of the spin axis position

and in phase opposite to said velocity

15 A method of stabilizing the central spin axis of a rotating system in a given position, said rotating system comprising a spindle motor having a central shaft defining the central spin axis; a rotor mounted on said shaft comprising an inertial load and bearing means to support said rotor for rotation relative to said shaft including developing a representation ofthe position of said spin axis or the oscillatory movements of said spin axis; and

analyzing said representation to calculate and generate radial forces which in turn stabilize the position ofthe spin axis and dampen oscillatory movements of said axis.

16. A method as claimed in claim 15 wherein the forces applied are established to be

proportional to either a derivative of position ofthe rotor or a velocity of oscillatory movement of said rotor.

17. A method as claimed in claim 16 wherein the rotating system includes an

electromagnetic actuator, and the method includes applying the forces utilizing said electromagnetic actuator. 18. A method as claimed in claim 17 wherein said electromagnetic actuator comprises stationary windings and rotating magnets surrounding said spin axis, and said method includes energizing said stationary winding to apply said forces to dampen said oscillatory movements

19. A method as claimed in claim 18 wherein said rotating system includes said motor

surrounding said spin axis and comprising magnets and windings rotating relative to one another.

20. A method as claimed in claim 19 wherein the magnets of said motor and the magnets of said stabilizing actuator are a common set of magnets.

21. A method as claimed in claim 20 wherein the rotating system is said spindle motor having a central shaft comprising said spin axis and defining the central rotational axis ofthe rotating system, and wherein said rotating system inertial load comprises at least one disc which is subject to

said undamped vibrating movement.

22. A method as claimed in claim 21 wherein the vibrating movement is defined as a

function of two angular rotations α and β which are radial and orthogonal to one another

23. A method as claimed in claim 22 wherein the radial damping forces are applied to

said central shaft below said discs.

24. A method as claimed in claim 23 wherein the central shaft is supported on upper

and lower bearings, and a center of mass ofthe system is defined between the bearings - -

25 A method as claimed in claim 24 wherein said central shaft supports a rotor magnet which rotates with said shaft, said radial active damping forces being applied to said shaft