Steering control apparatus

• US 6,427,104 B1
• Filed: 01/07/2002
• Issued: 07/30/2002
• Est. Priority Date: 07/30/2001
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kifuku, Takayuki, Matsushita, Masaki, Kimata, Masahiro
• Primary Examiner(s): Camby, Richard M.
• Application Number:
  US10/036,532
• Time in Patent Office: 204 Days
• Field of Search: 701/41, 701/42, 180/6.2, 180/410, 180/443, 180/446
• US Class Current: 701/41
• CPC Class Codes: B62D 5/0463 calculating assisting torque from the motor based on driver input

Abstract

A steering control apparatus is provided which is capable of alleviating a decrease in the output torque of a motor during high-speed steering. The steering control apparatus includes a motor 5, a motor current instruction value generation section 100a, 100b for generating a current instruction value for the motor 5, a motor current detection section 102a, 102b for detecting a current flowing through the motor 5, wherein the motor 5 is driven to rotate based on at least the current, which flows through the motor 5, and the current instruction value. The motor current instruction value generation section includes a correction section 100b for correcting the current instruction value which controls the magnetic field of a field magnet of the motor 5, the correction section being operable to correct the current instruction value for controlling the magnetic field of the field magnet of the motor 5 when a steering speed is fast.

Claims

1. A steering control apparatus including a motor, a motor current instruction value generation section for generating a current instruction value for said motor, and a motor current detection section for detecting a current flowing through said motor, said motor being driven to operate based on at least the current flowing through said motor and said current instruction value,

wherein said motor current instruction value generation section includes a correction section for correcting a current instruction value which controls a magnetic field of a field magnet of said motor, said correction section being operable to correct said current instruction value for controlling the magnetic field of said motor field magnet when a steering speed is high.

2. The steering control apparatus according to claim 1, further comprising a motor control section for performing torque control on said motor in accordance with a torque instruction through vector control which is represented by a two-phase rotating magnetic flux coordinate system having a direction of a field current oriented in a d-axis direction and a direction perpendicular to the d-axis oriented in a q-axis direction, wherein said correction section corrects a d-axis current instruction value in such a manner that a d-axis current is controlled to such a predetermined value as to weaken the magnetic field of said motor field magnet when a deviation between the q-axis current instruction value and a q-axis current detection value becomes not less than a predetermined value.

3. The steering control apparatus according to claim 2, wherein said correction section increases a negative d-axis current instruction value for weakening the magnetic field of said motor field magnet when said q-axis current deviation is not less than a first predetermined value, and decreases the negative d-axis current instruction value for weakening the magnetic field of said motor field magnet when said q-axis current deviation is not greater than a second predetermined value.

4. The steering control apparatus according to claim 3, wherein said d-axis current instruction value is limited within a preset range.

5. The steering control apparatus according to claim 2, further comprising a stator phase current instruction value generation section for generating stator respective phase current instruction values from said q-axis current instruction value, wherein said current instruction value for controlling the magnetic field of said motor field magnet is corrected based on a deviation between at least one of said stator phase current instruction values and an actual corresponding stator phase current value in place of said q-axis current deviation.

6. The steering control apparatus according to claim 1, further comprising a reference steering torque generation section for generating a reference steering torque which is used to determine whether the magnetic field of said motor field magnet is to be weakened, wherein when the steering torque becomes not less than said reference steering torque, said correction section corrects said current instruction value to such a prescribed value as to weaken the magnetic field of said motor field magnet.

7. The steering control apparatus according to claim 6, wherein said reference steering torque generation section generates said reference steering torque as a function of at least a vehicle speed.

8. The steering control apparatus according to claim 1, further comprising a steering speed detection section for detecting a steering speed of a steering wheel, wherein said correction of the current instruction value for controlling the magnetic field of said motor field magnet is effected such that when the steering speed of said steering wheel becomes not less than a predetermined value, said current instruction value is corrected to such a prescribed value as to weaken the magnetic field of said motor field magnet.

9. The steering control apparatus according to claim 1, further comprising:

a motor control section for performing torque control on said motor in accordance with a torque instruction through vector control which is represented by a two-phase rotating magnetic flux coordinate system having a direction of a field current oriented in a d-axis direction and a direction perpendicular to the d-axis direction oriented in a q-axis direction;

a speed detection section for detecting a rotational speed of said motor; and

a voltage limitation value generation section for generating a voltage limitation value to a voltage applied to said motor;

wherein said correction section determines a d-axis current value for setting a working point on a voltage limitation circle through calculations based on at least the rotational speed of said motor, a q-axis current instruction value, a stator winding resistance, a stator winding reactance and a motor counter electromotive voltage constant, and effects correction in such a manner that when said d-axis current value determined through calculations is a current value which weakens the magnetic field of said motor field magnet more than a d-axis current instruction value does, said d-axis current value determined through calculations becomes equal to said d-axis current instruction value.

10. The steering control apparatus according to claim 9, further comprising a power supply voltage detection section for detecting a power supply voltage, wherein said voltage limitation value generation section generates, as a voltage limitation value, a value obtained by multiplying said power supply voltage by a predetermined coefficient.

11. The steering control apparatus according to claim 1, wherein said motor comprises a field winding type motor, and said apparatus further comprises a motor control section for performing torque control on said motor in accordance with a torque instruction in such a manner that a field winding current instruction value is corrected when a deviation between an armature current instruction value and an armature current detection value becomes not less than a predetermined value.

12. The steering control apparatus according to claim 11, wherein said field winding current instruction value is corrected in such a manner that it is decreased when said armature current deviation is not less than a first predetermined value, and it is increased when said armature current deviation is not greater than a second predetermined value.

13. The steering control apparatus according to claim 12, wherein said field winding current instruction value is limited to a preset minimum value.

14. The steering control apparatus according to claim 2, wherein said correction section corrects the current instruction value with a correction value which is determined through calculations.

15. The steering control apparatus according to claim 2, wherein said correction section corrects said current instruction value with a correction value which is obtained by referring to a table prepared in advance.

16. The steering control apparatus according to claim 2, wherein said d-axis current instruction value is limited to a value which is obtained by vector subtracting a q-axis current value from a preset maximum current vector value.

17. The steering control apparatus according to claim 2, wherein an integrated value of said deviation is used in place of said deviation.

18. The steering control apparatus according to claim 1, wherein said correction section corrects the current instruction value for controlling the magnetic field of said motor field magnet only when-a vehicle speed is not less than a predetermined value.

19. The steering control apparatus according to claim 1, wherein said correction section corrects the current instruction value for controlling the magnetic field of said motor field magnet only when a steering torque is not less than a predetermined value.