Controller for brushless motor

Abstract

A controller for a brushless motor generates a rotation force of a rotor by applying a voltage to an armature winding based on a d-axis target voltage Vd*, a q-axis target voltage Vq*, and a detected rotation position of the rotor. The d-axis target voltage Vd* is determined based on a value obtained by correcting a result of a feedback calculation for a d-axis current with a d-axis correction value −ωLqIq, and the q-axis target voltage Vq* is determined based on a value obtained by correcting a result of a feedback calculation for a q-axis current with a q-axis correction value ωLdId+ωΦ, in which ω stands for a rotation speed of the rotor, Ld stands for a d-axis self-inductance of the armature winding, Lq stands for a q-axis self-inductance of the armature winding, Id stands for the d-axis current, Iq stands for the q-axis current, and Φ stands for a value obtained by multiplying a maximum value of magnetic flux linkage of the armature winding in a field system of the rotor by a factor of (3/2)1/2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional view of an electric power steering apparatus of embodiments of the present invention.

FIG. 2 is a schematic explanatory drawing of a controller of the embodiments of the present invention.

FIG. 3 is a block-diagram illustrating the configuration of a dq-axes target voltage calculation part in the controller of the first embodiment of the present invention.

FIG. 4 illustrates an example of relationship between the rotation position of the rotor and the target applied voltage.

FIG. 5 is a flowchart illustrating the control procedure performed with the controller of the embodiment of the present invention.

FIG. 6A is a flow chart illustrating the calculation procedure of the target voltage with the controller of the first embodiment of the present invention.

FIG. 6B is a flow chart illustrating the calculation procedure of the target voltage with the controller of the first embodiment of the present invention.

FIG. 7A is a bode diagram representing a frequency response characteristic of q-axis current relative to q-axis target current in a case where the rotation speed of the brushless motor of the comparative example is 1500 rpm.

FIG. 7B is a bode diagram representing a frequency response characteristic of q-axis current relative to q-axis target current in a case where the rotation speed of the brushless motor of the first embodiment is 1500 rpm.

FIG. 8A is a bode diagram representing a frequency response characteristic of q-axis current relative to q-axis target current in a case where the rotation speed of the brushless motor of the comparative example is 500 rpm.

FIG. 8B is a bode diagram representing a frequency response characteristic of q-axis current relative to q-axis target current in a case where the rotation speed of the brushless motor of the first embodiment is 500 rpm.

FIG. 9 is a block-diagram illustrating the configuration of a dq-axes target voltage calculation part in the controller of the second embodiment of the present invention.

FIG. 10 is a flow chart illustrating the calculation procedure of the target voltage with the controller of the second embodiment of the present invention.

FIG. 11 is a block diagram illustrating the configuration of a dq-axis target voltage calculation part in the controller of a brushless motor of the comparative example of the present invention.

Claims

1. A controller for a brushless motor, comprising a current detection part that detects a current flowing in an armature winding of said motor;a rotation position detection part that detects a rotation position of a rotor of said motor;a dq-axes target current calculation part that calculates a d-axis target current and a q-axis target current, where an axis along a magnetic flux direction of a field system of said rotor is taken as the d axis, and an axis perpendicular to said d axis and a rotation axis of said rotor is taken as the q axis;a dq-axes current calculation part that determines a d-axis current and a q-axis current based on the detected current and the detected rotation position;a d-axis target voltage calculation part that determines a d-axis target voltage based on a feedback calculation for said d-axis current so as to decrease a d-axis difference between said d-axis target current and said d-axis current; anda q-axis target voltage calculation part that determines a q-axis target voltage based on a feedback calculation for said q-axis current so as to decrease a q-axis difference between said q-axis target current and said q-axis current, whereina rotation force of said rotor is generated by applying a voltage to said armature winding based on said d-axis target voltage, said q-axis target voltage, and the detected rotation position;a d-axis correction value calculation part for determining a d-axis correction value −ωLqIq and a q-axis correction value calculation part for determining a q-axis correction value ωLdId+ωΦ are provided, where ω stands for a rotation speed (rad/sec) of said rotor, Ld stands for a d-axis self-inductance of said armature winding, Lq stands for a q-axis self-inductance of said armature winding, Id stands for said d-axis current, Iq stands for said q-axis current, and Φ stands for a value obtained by multiplying a maximum value of magnetic flux linkage of said armature winding in said field system by a factor of (3/2)1/2;said d-axis target voltage is determined based on a value obtained by correcting a result of the feedback calculation for said d-axis current with said d-axis correction value −ωLqIq; andsaid q-axis target voltage is determined based on a value obtained by correcting a result of the feedback calculation for said q-axis current with said q-axis correction value ωLdId+ωΦ.

2. A controller for a brushless motor, comprising a current detection part that detects a current flowing in an armature winding of said brushless motor;a rotation position detection part that detects a rotation position of a rotor of said motor;a dq-axes target current calculation part that calculates a d-axis target current and a q-axis target current, where an axis along a magnetic flux direction of a field system of said rotor is taken as the d axis, and an axis perpendicular to said d axis and a rotation axis of said rotor is taken as the q axis;a dq-axes current calculation part that determines a d-axis current and a q-axis current based on the detected current and the detected rotation position;a d-axis target voltage calculation part that determines a d-axis target voltage based on a feedback calculation for said d-axis current so as to decrease a d-axis difference between said d-axis target current and said d-axis current; anda q-axis target voltage calculation part that determines a q-axis target voltage based on a feedback calculation for said q-axis current so as to decrease a q-axis difference between said q-axis target current and said q-axis current, whereina rotation force of said rotor is generated by applying a voltage to said armature winding based on said d-axis target voltage, said q-axis target voltage, and the detected rotation position;a d-axis correction value calculation part for determining a d-axis correction value −ωLqIq and a q-axis correction value calculation part for determining a q-axis correction value ωLdId are provide, where ω stands for a rotation speed (rad/sec) of said rotor, Ld stands for a d-axis self-inductance of said armature winding, Lq stands for a q-axis self-inductance of said armature winding, Id stands for said d-axis current, and Iq stands for said q-axis current;said d-axis target voltage is determined based on a value obtained by correcting a result of the feedback calculation for said d-axis current with said d-axis correction value −ωLqIq; andsaid q-axis target voltage is determined based on a value obtained by correcting a result of the feedback calculation for said q-axis current with said q-axis correction value ωLdId.

3. The controller for a brushless motor according to claim 1, comprising: a dq-axes limiting value calculation part that determines a d-axis limiting value and a q-axis limiting value so that a target voltage applied to said armature winding does not exceed a set maximum value;a d-axis addition part that adds said d-axis correction value to the result of the feedback calculation for said d-axis current;a q-axis addition part that adds said q-axis correction value to the result of the feedback calculation for said q-axis current;a first d-axis limiter that limits an absolute value of the sum of said d-axis correction value and the result of the feedback calculation for said d-axis current to said d-axis limiting value;a second d-axis limiter that limits an absolute value of the result of the feedback calculation for said d-axis current to said d-axis limiting value;a first q-axis limiter that limits an absolute value of the sum of said q-axis correction value and the result of the feedback calculation for said q-axis current to said q-axis limiting value; anda second q-axis limiter that limits an absolute value of the result of the feedback calculation for said q-axis current to said q-axis limiting value, whereinan output value of said first d-axis limiter is treated as said d-axis target voltage;an output value of said first q-axis limiter is treated as said q-axis target voltage;an output value of said second d-axis limiter is used as a preceding value in the feedback calculation for said d-axis current in a next calculation cycle; andan output value of said second q-axis limiter is used as a preceding value in the feedback calculation for said q-axis current in a next calculation cycle.

4. The controller for a brushless motor according to claim 2, comprising: a dq-axes limiting value calculation part that determines a d-axis limiting value and a q-axis limiting value so that a target voltage applied to said armature winding does not exceed a set maximum value;a d-axis addition part that adds said d-axis correction value to the result of the feedback calculation for said d-axis current;a q-axis addition part that adds said q-axis correction value to the result of the feedback calculation for said q-axis current;a first d-axis limiter that limits an absolute value of the sum of said d-axis correction value and the result of the feedback calculation for said d-axis current to said d-axis limiting value;a second d-axis limiter that limits an absolute value of the result of the feedback calculation for said d-axis current to said d-axis limiting value;a first q-axis limiter that limits an absolute value of the sum of said q-axis correction value and the result of the feedback calculation for said q-axis current to said q-axis limiting value; anda second q-axis limiter that limits an absolute value of the result of the feedback calculation for said q-axis current to said q-axis limiting value, whereinan output value of said first d-axis limiter is treated as said d-axis target voltage;an output value of said first q-axis limiter is treated as said q-axis target voltage;an output value of said second d-axis limiter is used as a preceding value in the feedback calculation for said d-axis current in a next calculation cycle; andan output value of said second q-axis limiter is used as a preceding value in the feedback calculation for said q-axis current in a next calculation cycle.

5. The controller for a brushless motor according to claim 1, comprising: a dq-axes limiting value calculation part that determines a d-axis limiting value and a q-axis limiting value so that a target voltage applied to said armature winding does not exceed a set maximum value;a d-axis corrected limiting value calculation part that determines a d-axis corrected limiting value that is obtained by subtracting an absolute value of said d-axis correction value from said d-axis limiting value;a q-axis corrected limiting value calculation part that determines a q-axis corrected limiting value that is obtained by subtracting an absolute value of said q-axis correction value from said q-axis limiting value;a d-axis limiter that limits an absolute value of the result of the feedback calculation for said d-axis current to said d-axis corrected limiting value;a q-axis limiter that limits an absolute value of the result of the feedback calculation for said q-axis current to said q-axis corrected limiting value;a d-axis addition part that adds said d-axis correction value to an output value of said d-axis limiter; anda q-axis addition part that adds said q-axis correction value to an output value of said q-axis limiter, whereinan output value of said d-axis addition part is treated as said d-axis target voltage;an output value of said q-axis addition part is treated as said q-axis target voltage;the output value of said d-axis limiter is used as a preceding value in the feedback calculation for said d-axis current in a next calculation cycle; andthe output value of said q-axis limiter is used as a preceding value in the feedback calculation for said q-axis current in a next calculation cycle.

6. The controller for a brushless motor according to claim 2, comprising: a dq-axes limiting value calculation part that determines a d-axis limiting value and a q-axis limiting value so that a target voltage applied to said armature winding does not exceed a set maximum value;a d-axis corrected limiting value calculation part that determines a d-axis corrected limiting value that is obtained by subtracting an absolute value of said d-axis correction value from said d-axis limiting value;a q-axis corrected limiting value calculation part that determines a q-axis corrected limiting value that is obtained by subtracting an absolute value of said q-axis correction value from said q-axis limiting value;a d-axis limiter that limits an absolute value of the result of the feedback calculation for said d-axis current to said d-axis corrected limiting value;a q-axis limiter that limits an absolute value of the result of the feedback calculation for said q-axis current to said q-axis corrected limiting value;a d-axis addition part that adds said d-axis correction value to an output value of said d-axis limiter; anda q-axis addition part that adds said q-axis correction value to an output value of said q-axis limiter, whereinan output value of said d-axis addition part is treated as said d-axis target voltage;an output value of said q-axis addition part is treated as said q-axis target voltage;the output value of said d-axis limiter is used as a preceding value in the feedback calculation for said d-axis current in a next calculation cycle; andthe output value of said q-axis limiter is used as a preceding value in the feedback calculation for said q-axis current in a next calculation cycle.