Open-loop voltage driving of a DC motor

• US 7,164,250 B2
• Filed: 02/04/2005
• Issued: 01/16/2007
• Est. Priority Date: 02/06/2004
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: Boscolo, Michele, Capretta, Paolo
• Primary Examiner(s): Donovan; Lincoln
• Assistant Examiner(s): HORN, ROBERT WAYNE
• Application Number:
  US11/051,607
• Publication Number:
  US 20050174074A1
• Time in Patent Office: 711 Days
• Field of Search: None
• US Class Current: 318/400.42
• CPC Class Codes: G11B 5/5547 "Seek" control and circuits therefor G11B5/5556 takes precedence
• CPC Class Codes: H02P 25/034 Voice coil motors voice coil motors driven by DC power H02P7/025

Abstract

The driving voltage of the motor is incremented a quantity proportional to the speed of the motor according to a proportionality factor that is adjusted to compensate the back electromotive force. A method includes open-loop voltage control of a DC motor having a certain design speed constant, through a driving signal that is determined for imparting a certain acceleration to the motor and by generating a driving voltage of an output power stage to which the winding of the motor is connected as a function of the driving signal.

Claims

1. A method of open-loop voltage control of a DC motor having a predetermined speed constant, the method comprising:

driving the motor with a command signal to produce a constant acceleration of the DC motor;

generating a driving voltage with a filter for an output power stage connected to the winding of the DC motor based upon the command signal;

sensing an effective acceleration of the DC motor during a time interval;

compensating the driving voltage of the output power stage by incrementing it an amount proportional to a speed of the motor according to a proportionality factor such that during such time interval the acceleration of the DC motor does not vary in absolute value of more than a pre-established maximum value; and

determining an effective speed constant of the DC motor by determining said effective speed constant of the DC motor to be equal to the proportionality factor.

2. The method of claim 1, wherein the compensating is carried out iteratively and comprises the following sequence:

a) setting the proportionality factor equal to the predetermined speed constant;

b) ending the compensating if the absolute value of variations of the acceleration of the DC motor is less than the pre-established maximum value, otherwise

b1) adjusting the proportionality factor by a pre-established amount,

b2) driving the DC motor with an adjusted command signal, and

b3) sensing the effective acceleration of the DC motor during the time interval and continuing the sequence at step b).

3. The method of claim 2, wherein the pre-established amount is halved at each iteration.

4. A method of controlling a motor having a predetermined speed constant, the method comprising:

driving the motor with a command signal to produce a constant acceleration of the motor;

generating a driving voltage with a filter for the motor based upon the command signal;

sensing an effective acceleration of the motor during a time interval; and

compensating the driving voltage by incrementing it based upon a speed of the motor so that during such time interval the acceleration of the motor does not vary by more than a pre-established maximum variation; and

determining an effective speed constant of the motor based upon the proportionality factor.

5. The method of claim 4, wherein the compensating includes incrementing the driving voltage based upon a speed of the motor according to a proportionality factor, and comprises:

a) setting the proportionality factor equal to the predetermined speed constant;

b) ending the compensating if variations of the acceleration of the motor are less than the pre-established maximum variation, otherwise

b1) adjusting the proportionality factor by a pre-established amount,

b2) driving the motor with an adjusted command signal, and

b3) sensing the effective acceleration of the motor during the time interval.

6. The method of claim 5, wherein the pre-established amount is halved at each iteration.

7. An open-loop voltage mode control circuit of a DC motor having a predetermined speed constant, comprising:

a driving circuit generating a command signal to produce an acceleration of the motor;

an output power stage connected to a winding of the motor;

a filter receiving the command signal and generating a driving voltage for the output power stage; and

a compensation circuit to compensate the driving voltage for the output power stage by incrementing it based upon a speed of the motor according to a proportionality factor such that during a time interval the acceleration of the motor does not vary by more than a pre-established maximum variation;

wherein an effective speed constant of the motor is determined based upon the proportionality factor.

8. The control circuit of claim 7, wherein the compensation circuit increments the driving voltage, based upon a speed of the motor according to a proportionality factor, and includes

a) setting the proportionality factor equal to the predetermined speed constant;

b) ending the compensating if variations of the acceleration of the motor are less than the pre-established maximum variation, otherwise

b1) adjusting the proportionality factor by a pre-established amount,

b2) driving the motor with an adjusted command signal, and

b3) sensing the effective acceleration of the motor during the time interval.

9. The control circuit of claim 8, wherein the pre-established amount is halved at each iteration.

10. A method of open-loop voltage control of a DC motor having a predetermined speed constant, the method comprising:

driving the motor with a command signal to produce a constant acceleration of the DC motor;

generating a driving voltage with a filter for an output power stage connected to the winding of the DC motor based upon the command signal;

sensing an effective acceleration of the DC motor during a time interval; and

compensating the driving voltage of the output power stage by incrementing it an amount proportional to a speed of the motor according to a proportionality factor such that during such time interval the acceleration of the DC motor does not vary in absolute value of more than a pre-established maximum value;

wherein the compensating is carried out iteratively and comprises the following sequence

a) setting the proportionality factor equal to the predetermined speed constant,

b) ending the compensating if the absolute value of variations of the acceleration of the DC motor is less than the pre-established maximum value, otherwise

b1) adjusting the proportionality factor by a pre-established amount,

b2) driving the DC motor with an adjusted command signal, and

b3) sensing the effective acceleration of the DC motor during the time interval and continuing the sequence at step b).

11. The method of claim 10, wherein the pre-established amount is halved at each iteration.

12. A method of controlling a motor having a predetermined speed constant, the method comprising;

driving the motor with a command signal to produce a constant acceleration of the motor;

generating a driving voltage with a filter for the motor based upon the command signal;

sensing an effective acceleration of the motor during a time interval; and

compensating the driving voltage by incrementing it based upon a speed of the motor so that during such time interval the acceleration of the motor does not vary by more than a pre-established maximum variation;

wherein the compensating includes incrementing the driving voltage based upon a speed of the motor according to a proportionality factor, and comprises

a) setting the proportionality factor equal to the predetermined speed constant,

b) ending the compensating it variations of the acceleration of the motor are less than the pre-established maximum variation, otherwise

b1) adjusting the proportionality factor by a pre-established amount,

b2) driving the motor with an adjusted command signal, and

b3) sensing the effective acceleration of the motor during the time interval.

13. The method of claim 12, wherein the pre-established amount is halved at each iteration.

14. An open-loop voltage mode control circuit of a DC motor having a predetermined speed constant, comprising:

a driving circuit generating a command signal to produce an acceleration of the motor;

an output power stage connected to a winding of the motor;

a filter receiving the command signal and generating a driving voltage for the output power stage; and

a compensation circuit to compensate the driving voltage for the output power stage by incrementing it based upon a speed of the motor according to a proportionality factor such that during a time interval the acceleration of the motor does not vary by more than a pre-established maximum variation;

wherein the compensation circuit increments the driving voltage based upon a speed of the motor according to a proportionality factor, and includes

a) setting the proportionality factor equal to the predetermined speed constant;

b) ending the compensating if variations of the acceleration of the motor are less than the pre-established maximum variation, otherwise

b1) adjusting the proportionality factor by a pre-established amount,

b2) driving the motor with an adjusted command signal, and

b3) sensing the effective acceleration of the motor during the time interval.

15. The control circuit of claim 14, wherein the pre-established amount is halved at each iteration.