Apparatus and method compensating recurring false speed errors in DC motor and disk drive adopting same

Abstract

Provided are an apparatus and method of controlling a motor by compensating for recurring false speed errors generated in a direct current (DC) motor. The apparatus includes a learning control unit adapted to calculate recurring false speed errors related to a mechanical tolerance associated with the motor in each one of a plurality of controlling sections associated with a single rotation of the motor, and generate a corresponding reference speed for each controlling section, and a motor control unit adapted to control the rotational speed of the motor in relation to a speed error defined by a difference between the reference speed for each controlling section and an actual measured speed of the motor for each controlling section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Figure (FIG.) 1 is a plan view of a disk drive according to an embodiment of the present invention;

FIG. 2 is a block diagram of an electric circuit in the disk drive, to which an apparatus and method of compensating repeated false speed errors in a direct current (DC) motor is applied, according to an embodiment of the present invention;

FIG. 3 is a block diagram of an apparatus for compensating repeated false speed errors in a DC motor according to an embodiment of the present invention;

FIG. 4 is a flow chart illustrating a method of compensating the repeated false speed errors in a DC motor according to an embodiment of the present invention; and

FIG. 5 is a waveform diagram illustrating processes of phase signals using back electromotive force of a spindle motor.

Claims

1. A motor control apparatus compensating recurring false speed errors in a direct current (DC) motor, comprising: a learning control unit adapted to calculate recurring false speed errors related to a mechanical tolerance associated with the motor in each one of a plurality of controlling sections associated with a single rotation of the motor, and generate a corresponding reference speed for each controlling section; anda motor control unit adapted to control the rotational speed of the motor in relation to a speed error defined by a difference between the reference speed for each controlling section and an actual measured speed of the motor for each controlling section.

2. The apparatus of claim 1, wherein the learning control unit comprises; a plant modeling tool adapted to determining the reference speed for each controlling section.

3. The apparatus of claim 2, wherein the speed of the motor is measured using a phase signal generated in relation to a back electromotive force of the motor.

4. The apparatus of claim 2, wherein the learning control unit further comprises: a first average calculator adapted to calculate an average value of the actual measured motor speed in each of the controlling section in which a recurring false speed error is generated in relation to an initial reference speed;a second average calculator adapted to calculate an average value of control input signals driving the motor in each of the controlling sections in which a recurring false speed error is generated in relation to the initial reference speed;wherein the plant modeling tool is further adapted to calculate an estimated motor speed in each of the controlling section according to the average value of the control input signals;a subtractor adapted to calculate the false speed error of each controlling section by subtracting the estimated motor speed in each of the controlling sections from the average value of the actual measured motor speed; anda reference speed adjustor adapted to adjust the reference speed in each of the controlling sections to decrease the false speed error.

5. The apparatus of claim 4, wherein the plurality of controlling sections is N, (N being an integer greater than 1), and the number of controlling sections having a recurring false speed error is N.

6. The apparatus of claim 4, wherein the reference speed adjustor adjusts the reference speed of each controlling section using a look-up table in which corrected reference speed information corresponding to false speed errors in each of the controlling sections is defined.

7. The apparatus of claim 6, wherein the DC motor includes a brushless DC motor.

8. A method adapted to control operation of a motor, the motor having a mechanical tolerance generating recurring false speed errors, the method comprising: determining operation of the motor at a constant speed;controlling the speed of the motor in accordance with a reference speed;calculating recurring false speed errors associated with the mechanical tolerance in each one of a plurality of controlling sections related to one rotation of the motor;correcting the reference speed in each controlling section in relation to the calculated recurring false speed errors.

9. The method of claim 8, wherein the calculating of the false speed error and correcting of the reference speed comprises: calculating an average value for an actual measured motor speed in each of the controlling sections in which recurring false speed errors are generated while controlling the motor in relation to an initial reference speed;calculating an average value of control input signals driving the motor in each of controlling sections in which recurring false speed errors are generated while controlling the speed of motor in relation to the initial reference speed;estimating the motor speed in relation to the average value of the control input signals using a plant modeling tool;generating a false speed error for each controlling section by subtracting the estimated motor speed in each controlling section from the average value of the actual measured motor speed in each of the controlling sections; andchanging the reference speed from the initial reference speed for each controlling section to decrease the corresponding false speed error of each controlling section.

10. The method of claim 9, wherein the plurality of controlling sections is N, (N being an integer greater than 1), and the number of controlling sections having a recurring false speed error is N.

11. The method of claim 9, wherein the changing of the reference speed from the initial speed for each of the controlling sections is performed using a look-up table in which corrected reference speed information corresponding to false speed errors is defined.

12. A disk drive comprising: a disk adapted to store data;a spindle motor having a mechanical tolerance and adapted to rotate the disk at a constant angular velocity;a spindle motor controller adapted to calculate recurring false speed errors associated with eh mechanical tolerance during a plurality of N controlling sections related to a single rotation of the disk while controlling the speed of the spindle motor in relation to an initial reference speed, and further adapted to correct the reference speed for each controlling sections with reference to a false speed error calculated for each controlling section and generate a control input signal based on a difference between the corrected reference speed and the actual measured motor speed in each controlling sections; anda spindle motor driving unit adapted to generate an electric current in accordance with the control input signal to drive the spindle motor.

13. The disk drive of claim 12, wherein the spindle motor includes a brushless DC motor.

14. The disk drive of claim 12, wherein the speed of the spindle motor is measured using a phase signal generated by a back electromotive force generated in the spindle motor.

15. The disk drive of claim 12, wherein the spindle motor controller comprises: a first average calculator adapted to calculate an average value of the actual measured motor speed in each of the controlling section in which a recurring false speed error is generated in relation to an initial reference speed;a second average calculator adapted to calculate an average value of control input signals driving the motor in each of the controlling sections in which a recurring false speed error is generated in relation to the initial reference speed;wherein the plant modeling tool is further adapted to calculate an estimated motor speed in each of the controlling section according to the average value of the control input signals;a subtractor adapted to calculate the false speed error of each controlling section by subtracting the estimated motor speed in each of the controlling sections from the average value of the actual measured motor speed; anda reference speed adjustor adapted to adjust the reference speed in each of the controlling sections to decrease the false speed error.

16. The disk drive of claim 15, wherein the reference speed adjustor corrects the reference speed using a look-up table in which corrected reference speed corresponding to false speed errors in each of the controlling sections is defined.

17. The disk drive of claim 16, wherein when N is an integer greater than 1 and the number of controlling sections having recurring false speed error is N.

18. The disk drive of claim 17, wherein the spindle motor controlling unit corrects the reference speed in each of the controlling sections by adopting the false speed error of each controlling section during a predetermined period at an initial stage of driving the spindle motor at a constant speed.