Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
2002-02-14
2003-08-19
Nappi, Robert E. (Department: 2832)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S609000, C318S610000, C318S434000, C318S132000
Reexamination Certificate
active
06608456
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor control apparatus for controlling currents flowing through the armatures of a DC brushless motor according to a feedback control process.
2. Description of the Related Art
One conventional method of controlling a DC brushless motor employs a vector control process (hereinafter referred to as “dq control process”) which converts a 3-phase (U, V, W) DC brushless motor into an equivalent circuit having a q-axis armature on a q-axis which is aligned with the direction of magnetic fluxes of field systems on the rotor of the motor and a d-axis armature on a d-axis which extends perpendicularly to the q-axis.
A conventional motor control apparatus for carrying out the dq control process is arranged as shown in
FIG. 3
of the accompanying drawings. As shown in
FIG. 3
, a motor control apparatus
50
serves to control currents flowing through the armatures of a DC servomotor
51
, and has a U-phase current sensor
52
for detecting a current IU_s flowing through a U-phase armature of the DC servomotor
51
and a W-phase current sensor
53
for detecting a current IW_s flowing through a W-phase armature of the DC servomotor
51
.
The currents IU_s, IW_s and an electric angle &thgr; of the rotor of the motor
51
which is detected by a position detecting sensor (resolver or the like)
54
are supplied to a 3-phase/dq converter
55
, which outputs an actual current Id_s flowing through the d-axis armature and an actual current Iq_s flowing through the q-axis armature.
The motor control apparatus
50
is supplied with a command value Id_c for the current flowing through the d-axis armature and a command value Iq_c for the current flowing through the q-axis armature. A first subtractor
56
calculates the difference &Dgr;Id between the command value Id_c and the actual current Id_s, and a second subtractor
57
calculates the difference &Dgr;Iq between the command value Iq_c and the actual current Iq_s.
A first PI processor
58
and a second PI processor
59
perform a proportional and integral (PI) process to reduce the differences &Dgr;Id, &Dgr;Iq, and calculate a command value Vd_c for the voltage applied to the d-axis armature and a command value Vq_c for the voltage applied to the q-axis armature, respectively. The command values Vd_c, Vq_c are supplied to a dq/3-phase converter
60
, which converts them into command values VU_c, VV_c, VW_c for the voltages applied to the three-phase (U, V, W) armatures. A power drive unit
61
applies voltages according to the command values VU_c, VV_c, VW_c to the three-phase armatures of the motor
51
.
The process carried out by the first PI processor
58
and the second PI processor
59
is expressed by the following equation (1):
[
Vd
Vq
]
=
[
Kp
Δ
Id
+
Ki
∫
Δ
Id
ⅆ
t
+
ω
Ke
Kp
Δ
Iq
+
Ki
∫
Δ
Iq
ⅆ
t
]
(
1
)
where Vd: the voltage applied to the d-axis armature, Vq: the voltage applied to the q-axis armature, Kp: the proportional gain, Ki: integral gain, &ohgr;: the angular velocity of the motor, and Ke: the induced voltage constant.
In the applications of many motors, sufficient stability and responsiveness is achieved by the feedback control process of the above general proportional and integral control system. However, when the motor is operated at high rotational speeds, the motor may operate unstably or the control responsiveness may become insufficient under the control of the general proportional and integral control system.
The primary reason for the above drawbacks is considered to reside in that since the state equation of the proportional and integral control system is given as the following equation (2), when the motor operates at a high rotational speed, interference between the d- and q-axes increases due to the induced voltage generated depending on the angular velocity &ohgr; of the motor, causing the control system to respond in a vibrating fashion.
ⅆ
ⅆ
t
[
Id
Iq
]
=
[
-
r
+
Kp
Ld
ω
Lq
Ld
-
ω
Ld
Lq
-
r
+
Kp
Lq
]
&AutoLeftMatch;
[
Id
Iq
]
-
[
Ki
Ld
∫
Id
·
ⅆ
t
Ki
Lq
∫
Iq
·
ⅆ
t
]
-
[
r
Ld
0
0
-
r
Lq
]
[
Id_c
Iq_c
]
(
2
)
where Id: the current flowing through the d-axis armature, Iq: the current flowing through the q-axis armature, Ld: the inductance of the d-axis armature, Lq: the inductance of the q-axis armature, and r: the resistance of the d-axis armature and the q-axis armature.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a motor control apparatus for converting a DC brushless motor into an equivalent circuit having a q-axis armature on a q-axis which is aligned with the direction of magnetic fluxes of field systems of the motor and a d-axis armature on a d-axis which extends perpendicularly to the q-axis, comprising current detecting means for detecting currents flowing through armatures of the motor, actual current calculating means for calculating a q-axis actual current flowing through the q-axis armature and a d-axis actual current flowing through the d-axis armature from the currents detected by the current detecting means, and current difference calculating means for calculating a q-axis current difference between a q-axis command current which is a command value for the current flowing through the q-axis armature and the q-axis actual current and a d-axis current difference between a d-axis command current which is a command value for the current flowing through the d-axis armature and the d-axis actual current, means for generating a d-axis command voltage which is a command value for the voltage applied to the d-axis armature and a q-axis command voltage which is a command value for the voltage applied to the q-axis armature in order to reduce the d-axis current difference and the q-axis current difference, and means for controlling the currents flowing through the armatures of the motor depending on the d-axis command voltage and the q-axis command voltage.
The motor control apparatus comprises proportional term component generating means for carrying out a proportional process to multiply the d-axis current difference and the q-axis current difference by respective predetermined proportional gains to generate a d-axis proportional term component which is a proportional term component of the d-axis command voltage and a q-axis proportional term component which is a proportional term component of the q-axis command voltage, integral term component generating means for effecting an integrating process on the d-axis current difference and the q-axis current difference based on a predetermined integral gain to generate a d-axis integral term component which is an integral term component of the d-axis command voltage and a q-axis integral term component which is an integral term component of the q-axis command voltage, and command voltage generating means for generating the d-axis command voltage depending on the sum of the d-axis proportional term component and the d-axis integral term component, and the q-axis command voltage depending on the sum of the q-axis proportional term component and the q-axis integral term component, means for setting the integral gain to stabilize a system in which the d-axis current difference and the q-axis current difference are multiplexed, integrated, and inputted, with respect to a steady gain which approximates, including the proportional gains, the steady input-to-output relationship of the motor to which the voltage applied to the d-axis armature and the voltage applied to the q-axis armature are inputted and from which the current flowing through the d-axis armature and the current flowing through the q-axis armature are outputted.
With the above arrangement, the proportional term component generating means generates the d-axis proportional term component an
Imai Nobuyuki
Tsukamoto Toshinori
Arent Fox Kintner & Plotkin & Kahn, PLLC
Duda Rina I.
Honda Giken Kogyo Kabushiki Kaisha
Nappi Robert E.
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