Direct current motor for closed-loop feedback control

• US 5,955,853 A
• Filed: 10/14/1997
• Issued: 09/21/1999
• Est. Priority Date: 01/31/1997
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Lander, Daniel
• Primary Examiner(s): Ip, Paul
• Application Number:
  US08/950,164
• Time in Patent Office: 707 Days
• Field of Search: 318/138, 318/139, 318/245, 318/254, 318/439, 318/734, 318/735, 318/638, 318/799, 318/607, 310/51, 310/67 R, 310/245, 310/186, 310/65, 310/216, 310/195, 310/180
• US Class Current: 388/816
• CPC Class Codes: G05B 19/231 the positional error is used to control continuously the servomotor according to its magnitude
• CPC Class Codes: H02K 23/26 characterised by the armature windings
• CPC Class Codes: H02K 23/66 Structural association with auxiliary electric devices influencing the characteristic of, or controlling, the machine, e.g. with impedances or switches
• CPC Class Codes: H02P 7/28 using semiconductor devices

Abstract

A direct current motor for use in a closed-loop control system is disclosed that produces a time varying signal indicative of a position of the motor. An embodiment of the motor includes a rotating commutator having a plurality of slots, a plurality of windings, the number of windings corresponding to one more than the number of slots of the commutator, and a plurality of brushes that are configured so that application of a direct current voltage across the brushes causes the commutator to rotate.

A closed-loop control system is also disclosed that includes a direct current voltage source, a direct current motor in accordance with the present, a motor position signal source that generates a motor position signal for rotating the shaft of the direct current motor to a desired position, and a feedback circuit that corrects for any error in the desired position of the shaft of the direct current motor.

Further disclosed are methods of controlling a position of a direct current motor constructed in accordance with the present invention in a closed-loop feedback control system.

Claims

1. A direct current motor for use in a closed-loop control system, comprising:

a commutator, the commutator including a plurality of slots and being configured to rotate;

a plurality of windings, the number of windings corresponding to one more than the number of slots of the commutator; and

a plurality of brushes, the brushes being configured so that application of a direct current voltage across the brushes results in a current flow in at least one of the windings which causes the commutator to rotate.

2. The direct current motor of claim 1, wherein two of the windings are electrically in parallel.

3. The direct current motor of claim 1, wherein the current flowing in the windings varies with time and has a maximum magnitude indicative of a position of the motor.

4. The direct current motor of claim 1, further comprising a shaft coupled to the commutator so that rotation of the commutator results in rotation of the shaft, and wherein the current flowing in the windings varies with time in a manner indicative of a position of the shaft.

5. The direct current motor of claim 4, wherein the current flowing in the windings has a maximum magnitude every one hundred and eighty degrees (180°

) of rotation of the shaft.

6. A closed-loop control system, comprising:

a direct current motor including a shaft, a commutator having a plurality of slots and being configured to rotate, and a plurality of windings, the number of windings corresponding to one more than the number of slots of the commutator, the direct current motor being configured so that application of a direct current voltage to the motor causes the shaft to rotate and produces a current that varies with time as the shaft rotates and that has a maximum magnitude indicative of a position of the shaft of the motor;

a motor position signal source, the motor position signal source generating a motor commanded position signal for rotating the shaft of the direct current motor to a desired position;

a feedback circuit configured to generate an actual position signal representative of the actual position of the shaft of the direct current motor, the actual position signal being derived from the time varying magnitude of the current, and further configured to generate a motor position error signal representative of any difference between the motor commanded position signal from the motor position signal source and the actual position signal; and

a direct current voltage source, the direct current voltage source being coupled to the direct current motor;

wherein the motor position error signal is coupled to the direct current voltage source to rotate the shaft of the direct current motor based on the motor position error signal to correct for any error in the desired position of the shaft of the direct current motor.

7. The closed-loop control system of claim 6, wherein the motor position signal source includes one of a microprocessor and a controller.

8. The closed-loop control system of claim 6, wherein the feedback circuit includes an Application Specific Integrated Circuit (ASIC) that is designed to generate the actual position signal based on the time varying magnitude of the current.

9. The closed-loop control system of claim 8, wherein the feedback circuit further includes a comparator configured to generate the motor position error signal representative of any difference between the motor commanded position signal from the motor position signal source and the actual position signal.

10. The closed-loop control system of claim 6, in a printing mechanism.

11. The closed-loop control system of claim 6, wherein two of the windings are electrically in parallel.

12. A closed-loop control system, comprising:

a direct current motor including a shaft, a commutator having a plurality of slots and being configured to rotate, and a plurality of windings, the number of windings corresponding to one more than the number of slots of the commutator, the direct current motor being configured so that application of a constant current to the motor causes the shaft to rotate and produces a voltage that varies with time as the shaft rotates and that has a maximum magnitude indicative of a position of the shaft of the motor;

a motor position signal source, the motor position signal source generating a motor commanded position signal for rotating the shaft of the direct current motor to a desired position;

a feedback circuit configured to generate an actual position signal representative of the actual position of the shaft of the direct current motor, the actual position signal being derived from the time varying magnitude of the voltage, and further configured to generate a motor position error signal representative of any difference between the motor commanded position signal from the motor position signal source and the actual position signal; and

a constant current source, the constant current source being coupled to the direct current motor;

wherein the motor position error signal is coupled to the constant current source to rotate the shaft of the direct current motor based on the motor position error signal to correct for any error in the desired position of the shaft of the direct current motor.

13. The closed-loop control system of claim 12, wherein the motor position signal source includes one of a microprocessor and a controller.

14. The closed-loop control system of claim 12, wherein the feedback circuit includes an Application Specific Integrated Circuit (ASIC) that is designed to generate the actual position signal based on the time varying magnitude of the voltage.

15. The closed-loop control system of claim 14, wherein the feedback circuit further includes a comparator configured to generate the motor position error signal representative of any difference between the motor commanded position signal from the motor position signal source and the actual position signal.

16. The closed-loop control system of claim 12, in a printing mechanism.

17. The closed-loop control system of claim 12, wherein two of the windings are electrically in parallel.

18. A method of controlling a position of a direct current motor in a closed-loop feedback control system, the direct current motor including a shaft, a commutator having a plurality of slots and being configured to rotate, and a plurality of windings, the number of windings corresponding to one more than the number of slots of the commutator, the method comprising the steps of:

generating a motor commanded position signal for rotating the shaft of the direct current motor to a desired position;

generating an actual position signal representative of the actual position of the shaft of the direct current motor, the actual position signal being derived from a time varying magnitude of a current of the direct current motor;

generating a motor position error signal representative of any difference between the motor commanded position signal and the actual position signal; and

generating a direct current voltage based on the motor position error signal to rotate the shaft of the direct current motor to the desired position.

19. A method of controlling a position of a direct current motor in a closed-loop feedback control system, the direct current motor including a shaft, a commutator having a plurality of slots and being configured to rotate, and a plurality of windings, the number of windings corresponding to one more than the number of slots of the commutator, the method comprising the steps of:

generating a motor commanded position signal for rotating the shaft of the direct current motor to a desired position;

generating an actual position signal representative of the actual position of the shaft of the direct current motor, the actual position signal being derived from a time varying magnitude of a voltage of the direct current motor;

generating a motor position error signal representative of any difference between the motor commanded position signal and the actual position signal; and

generating a constant current based on the motor position error signal to rotate the shaft of the direct current motor to the desired position.