Motor control apparatus

• US 7,667,427 B2
• Filed: 12/30/2005
• Issued: 02/23/2010
• Est. Priority Date: 07/09/2002
• Status: Active Grant

• Current Assignee: Ibaraki Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: DENSO Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Fujiki, Kenichi, Kobiki, Yasushi, Inoue, Yuji, Kamio, Shigeru, Amamiya, Sumiko
• Primary Examiner(s): Benson; Walter
• Assistant Examiner(s): MCCLOUD, RENATA D
• Application Number:
  US11/320,962
• Publication Number:
  US 20060108966A1
• Time in Patent Office: 1,516 Days
• Field of Search: 318/701, 318/721, 318/724, 318/568.24
• US Class Current: 318/701
• CPC Class Codes: G05B 19/4062 Monitoring servoloop, e.g. overload of servomotor, loss of feedback or reference
• CPC Class Codes: G05B 2219/42287 On feedback failure, use profile stored in memory during learning
• CPC Class Codes: G05B 2219/42322 Emit dummy pulses, detect loss of pulses, feedback failure, wire brake, short
• CPC Class Codes: H02P 6/12 Monitoring commutation; Providing indication of commutation failure

Abstract

Presence/absence of a failure in a feedback control system of a motor is monitored. When a failure is detected in the feedback control system, the motor is driven by switching to an open-loop control. During the open-loop control, the motor is rotated by sequentially switching the motor current supply phase without feeding back encoder count information. The position count is incremented or decremented every time the current supply phase is switched. When the position count has reached a target count, it is determined that the rotor has reached a target position, whereupon the open-loop control is finished.

Claims

1. A motor control apparatus comprising:

an encoder for producing a pulse signal in synchronism with rotation of a rotor of a motor that rotates a control object;

control means for rotating the rotor to a target position by detecting a rotation position of the rotor on the basis of a count of the pulse signal of the encoder and sequentially switching a current supply phase of the motor; and

abnormality monitoring means for monitoring presence/absence of an abnormality in a state of a feedback control on the motor,

wherein the control means switches from the feedback control to an open-loop control and rotates the rotor by sequentially switching the current supply phase of the motor without feeding back information of the count of the pulse signal of the encoder, when the abnormality monitoring means detects an abnormality in the state of the feedback control.

2. The motor control apparatus according to claim 1,

wherein the abnormality monitoring means monitors presence/absence of an abnormality in the state of the feedback control by monitoring one of an output interval of the pulse signal of the encoder and a rotation speed of the rotor during the feedback control.

3. The motor control apparatus according to claim 1, wherein:

the encoder produces an A-phase signal and a B-phase signal that have a prescribed phase difference in synchronism with rotation of the rotor;

the control means updates the count of the pulse signal of the encoder by counting a pulse of the A-phase signal and a pulse of the B-phase signal during the feedback control to determine a rotation direction of the rotor on the basis of order of occurrence of the pulse of the A-phase signal and the pulse of the B-phase signal and to increment or decrement the count in accordance with the rotation direction, and the control means selects a current supply phase on the basis of the updated count and the rotation direction of the rotor; and

the abnormality monitoring means monitors presence/absence of an abnormality in the state of the feedback control by separately counting pulses of the A-phase signal and pulses of the B-phase signal during the feedback control and comparing counts of the A-phase signal and the B-phase signal.

4. The motor control apparatus according to claim 1,

wherein the abnormality monitoring means monitors a rotation direction of the rotor during the feedback control, and monitors presence/absence of an abnormality in the state of the feedback control on the basis of whether the rotation direction of the rotor has reversed from a rotation direction toward the target position.

5. The motor control apparatus according to claim 1, wherein the control means comprises:

means for learning a corresponding relationship between a rotation position of the rotor and a current supply phase by effecting current supply for all phases of the motor around according to a prescribed time schedule in an initial drive that is performed after power application; and

means for learning at least one of limit positions of a movable range of the control object by performing a butting control in which the rotor is rotated until butting occurs at the at least one limit position,

wherein the control means performs an initial drive and a butting control also when a return is made from the open-loop control to a feedback control.

6. The motor control apparatus according to claim 5,

wherein the abnormality monitoring means suspends monitoring of presence/absence of an abnormality in the state of the feedback control during the butting control.

7. The motor control apparatus according to claim 1,

wherein the control means counts the number of times of switching of the current supply phase during the open-loop control and causes a return to a feedback control when determining that the rotor has reached the target position on the basis of a resulting count, when an abnormality is detected in the state of the feedback control.

8. The motor control apparatus according to claim 7,

wherein, when an event that even if a return is made from an open-loop control to a feedback control an abnormality is detected again in the state of the feedback control and switching is made to an open-loop control has occurred a prescribed number of times consecutively, the abnormality monitoring means finally decides that an abnormality exists and does not cause a return to a feedback control any more.

9. The motor control apparatus according to claim 1,

wherein the motor is a switched reluctance motor.

10. The motor control apparatus according to claim 1,

wherein the control object is a position switching device for switching between a parking position and another position of a vehicle.

11. A motor control apparatus comprising:

an encoder for producing a pulse signal in synchronism with rotation of a rotor of a motor that rotates a control object;

control means for rotating the rotor to a target position by detecting a rotation position of the rotor on the basis of a count of the pulse signal of the encoder and sequentially switching a current supply phase of the motor;

failure monitoring means for monitoring presence/absence of a failure in a feedback control system of the motor; and

fail-safe means for switching from the feedback control to an open-loop control when the failure monitoring means has detected a failure in the feedback control system, sequentially switching the current supply phase of the motor without feeding back information of the count of the pulse signal of the encoder, counting the number of times of switching of the current supply phase, and rotating the rotor to the target position on the basis of a resulting count.

12. The motor control apparatus according to claim 11,

wherein, in driving the motor from a stop state by the open-loop control, the fail-safe means performs two-phase current supply as first current supply and thereafter performs one-phase current supply and two-phase current supply alternately.

13. The motor control apparatus according to claim 11,

wherein, in driving the motor from a stop state by the open-loop control, the fail-safe means sets a current supply time of a prescribed number of first current supply attempts longer than a current supply time of subsequent current supply attempts.

14. The motor control apparatus according to claim 11,

wherein, during the open-loop control, the fail-safe means sets a current supply time on the basis of at least one of a rotation speed of the rotor, a rotation amount of the rotor after a start of driving, an elapsed time from the start of the driving, a rotation amount to the target position, and load torque.

15. The motor control apparatus according to claim 11,

wherein the fail-safe means disregards a received target position switching manipulation signal in a period when the rotor is rotated toward the target position by the open-loop control.

16. The motor control apparatus according to claim 11, further comprising:

an output shaft sensor for detecting a rotation position of an output shaft of the motor or position information correlated with it, wherein the fail-safe means finishes the open-loop control when a rotation position of the rotor inferred on the basis of a count of the number of times of switching of the current supply phase during the open-loop control has reached the target position, determines whether driving of the motor by the open-loop control has succeeded or failed on the basis of an output signal of the output shaft sensor, and, if the driving of the motor has failed, drives the motor again by an open-loop control.

17. The motor control apparatus according to claim 16,

wherein, if the driving of the motor by the open-loop control has failed a prescribed number of times consecutively, the fail-safe means determines that the motor cannot be controlled by an open-loop control and turns off current supply of the motor.

18. The motor control apparatus according to claim 16,

wherein the fail-safe means infers an initial position of the rotor at a start of the open-loop control on the basis of the output signal of the output shaft sensor, and infers a rotation position of the rotor during the open-loop control on the basis of the inferred initial position of the rotor and the count of the number of times of switching of the current supply phase.

19. The motor control apparatus according to claim 11,

wherein the motor is a switched reluctance motor.

20. The motor control apparatus according to claim 11,

wherein the control object is a position switching device for switching between a parking position and another position of a vehicle.

21. The motor control apparatus according to claim 20,

wherein the fail-safe means performs a torque restriction control for restricting engine torque during a position switching operation by the open-loop control.

22. A motor control apparatus comprising:

an encoder for producing a pulse signal in synchronism with rotation of a rotor of a motor that rotates a control object;

feedback control means for performing a feedback control for rotating the rotor to a target position by detecting a rotation position of the rotor on the basis of a count of the pulse signal of the encoder and sequentially switching a current supply phase of the motor;

open-loop control means for switching from the feedback control to an open-loop control if a feedback control execution condition is not satisfied, sequentially switching the current supply phase by supplying a drive signal to a drive circuit of the motor without feeding back information of the count of the pulse signal of the encoder, counting pulses of the drive signal, and rotating the rotor to the target position on the basis of a resulting count; and

abnormality diagnosis means for determining presence/absence of an abnormality in the encoder by comparing a count of the pulse signal of the encoder and the count of the drive signal that are obtained during the open-loop control.

23. The motor control apparatus according to claim 22,

wherein the abnormality diagnosis means prohibits a return from the open-loop control to a feedback control when detecting an abnormality in the encoder.

24. The motor control apparatus according to claim 22, wherein:

the encoder produces an A-phase signal and a B-phase signal that have a prescribed phase difference in synchronism with rotation of the rotor and also produces pulses of a Z-phase signal at reference rotation positions of the rotor;

the feedback control means counts edges of the A-phase signal and the B-phase signals during the feedback control, sequentially switches the current supply phase on the basis of an edge count, determines whether a deviation exists between the rotation position of the rotor and the current supply phase on the basis of the Z-phase signal, and performs a Z-phase correction of correcting for the deviation if any; and

the abnormality diagnosis means determines presence/absence of an abnormality in the A-phase signal and the B-phase signal of the encoder by comparing the edge count obtained during the open-loop control and the count of the drive signal.

25. The motor control apparatus according to claim 24,

wherein, when determining that the A-phase signal and the B-phase signal of the encoder are normal, the abnormality diagnosis means determines presence/absence of an abnormality in the Z-phase signal by determining an output interval of the Z-phase signal on the basis of the edge count.

26. The motor control apparatus according to claim 25,

wherein the abnormality diagnosis means prohibits the Z-phase correction when detecting an abnormality in the Z-phase signal.

27. The motor control apparatus according to claim 22,

wherein the motor is a switched reluctance motor.

28. The motor control apparatus according to claim 22,

wherein the control object is a position switching device for switching between a parking position and another position of a vehicle.