JP2023128493A - Motor control device and motor control method - Google Patents

Abstract

To provide a motor control device capable of suppressing the influence of the rotational speed of a motor on output torque of the motor.SOLUTION: A motor control device includes a target torque determination part, an Id determination part (522), an Iq determination part (524), and a control part. The Id determination part (522) determines a d-axis current command value (Id1) on the basis of the rotational speed (ω) of a motor, target torque (Tr1), and information for preliminarily associating the d-axis current command value (Id1) with the rotational speed (ω) of the motor and the target torque (Tr1). The Iq determination part (524) determines a q-axis current command value (Iq1) on the basis of the d-axis current command value (Id1), the target torque (Tr1), and a prescribed relation expression. The control part controls the drive of the motor on the basis of the d-axis current command value (Id1) and the q-axis current command value (Iq1).SELECTED DRAWING: Figure 5

Description

The present invention relates to a motor control device that controls motor drive, and a motor control method.

Conventionally, in the control of synchronous motors, there have been demands for higher accuracy, higher efficiency, and higher output. In the synchronous motor disclosed in Patent Document 1, a d-axis current command that maximizes torque efficiency is calculated using a preset data table in response to a torque command. By recalculating the q-axis current command from the torque command and d-axis current command using the synchronous motor torque formula, it is possible to control the output torque with high precision and control the synchronous motor with high efficiency. It is possible.

JP2010-088238A

However, when a motor is driven using a battery mounted on a vehicle or the like, a desired torque may not be output depending on the rotational speed of the motor due to the rated current or rated voltage determined for the battery. This is because the voltage applied to the stator coil is reduced due to the induced electromotive force generated when the motor rotates, and the current flowing through the stator coil becomes smaller than the q-axis current command value.

For this reason, when determining the d-axis current command value only by the torque command as in Patent Document 1, the output torque decreases with respect to the torque command required as the motor output, and the motor rotation speed In some cases, the desired torque may not be output.

SUMMARY OF THE INVENTION An object of the present invention is to provide a motor control device and a motor control method that can suppress the influence of the rotational speed of a motor on the output torque of the motor.

In order to solve the above problems, a motor control device according to one aspect of the present invention includes a target torque determining unit that determines a target torque that is a target torque of a motor, a rotation speed of the motor, and a target torque that is a target torque of a motor. Based on the target torque determined by the determination unit and information associating a d-axis current command value, which is a current command value of the d-axis of the motor, with the rotational speed of the motor and the target torque, a first determining unit that determines the d-axis current command value of the d-axis current command value, the d-axis current command value determined by the first determining unit, the target torque determined by the target torque determining unit, and a predetermined relational expression. a second determining unit that determines a q-axis current command value, which is a current command value of the q-axis of the motor, based on the d-axis current command value and the q-axis current command value; A control unit for controlling.

The motor control method according to one aspect of the present invention includes a target torque determining step of determining a target torque that is a target torque of the motor, a rotational speed of the motor, and a target torque determined in the target torque determining step. and information in which a d-axis current command value, which is a d-axis current command value of the motor, is associated in advance with the rotational speed of the motor and the target torque, the d-axis current command value of the motor is determined. a d-axis current command value determining step for determining the d-axis current command value, the d-axis current command value determined in the d-axis current command value determining step, the target torque determined in the target torque determining step, and a predetermined relational expression. a q-axis current command value determining step of determining a q-axis current command value, which is a current command value of the q-axis of the motor, based on the d-axis current command value and the q-axis current command value; and a control step of controlling driving of the motor.

According to one aspect of the present invention, it is possible to realize a motor control device that can suppress the influence of the rotational speed of the motor on the output torque of the motor.

1 is a diagram showing a schematic configuration of an electric power steering system including an ECU according to an embodiment of the present invention. FIG. 2 is a block diagram showing the electrical configuration of the ECU shown in FIG. 1. FIG. FIG. 3 is a block diagram showing the electrical configuration of a control section in FIG. 2. FIG. It is a figure showing the control method of the motor by ECU. FIG. 4 is a block diagram showing the electrical configuration of a dq-axis target current determining section in FIG. 3. FIG. It is a graph showing map information showing the correspondence between the rotational speed and target torque of the motor and the d-axis current command value. 7 is a graph showing switching of motor control according to the rotational speed of the motor. It is a graph showing the correspondence between the d-axis current value and the d-axis inductance value for each q-axis current value. It is a graph showing the correspondence between the q-axis current value and the q-axis inductance value for each d-axis current. It is a graph regarding limit processing of a q-axis current command value.

A motor control device according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 10. In this embodiment, a case will be described in which a motor control device of the present invention is applied to an ECU (Electronic Control Unit) 1 of an electric power steering system 100.

FIG. 1 is a diagram showing a schematic configuration of an electric power steering system 100 including an ECU 1. As shown in FIG. As shown in FIG. 1, the electric power steering system 100 includes an ECU 1, a steering mechanism 2, an assist mechanism 3, a power source 50, a torque sensor 60, and a vehicle speed sensor 70.

The steering mechanism 2 includes a steering wheel 11, a steering shaft 12, a rack shaft 13, and a rack and pinion mechanism 14. The steering mechanism 2 is a mechanism for steering left and right wheels 16 connected to both ends of the rack shaft 13 via tie rods 15 based on the operation of the steering wheel 11 by the driver.

The steering shaft 12 is fixed to the steering wheel 11 and serves as a rotation axis of the steering wheel 11. The steering shaft 12 includes a column shaft 12a, an intermediate shaft 12b, and a pinion shaft 12c.

Column shaft 12a is connected to steering wheel 11. The intermediate shaft 12b is connected to the lower end of the column shaft 12a. The pinion shaft 12c is connected to the lower end of the intermediate shaft 12b.

The rack shaft 13 is connected to the lower end of the steering shaft 12 via a rack and pinion mechanism 14. When the steering shaft 12 rotates as the driver operates the steering wheel 11, the rotational motion is converted into a reciprocating linear motion in the axial direction of the rack shaft 13 via the rack and pinion mechanism 14.

The reciprocating linear motion of the rack shaft 13 is transmitted to the wheels 16 via tie rods 15 connected to both ends of the rack shaft 13. As a result, the steering angle of the wheels 16 changes, and the direction of travel of the vehicle is changed.

The assist mechanism 3 is a mechanism for assisting the driver in operating the steering wheel 11, and includes a motor 30. The motor 30 is, for example, a three-phase (U-phase, V-phase, W-phase) internal permanent magnet (IPM) synchronous motor. The internal permanent magnet synchronous motor includes a three-phase stator coil and a rotor in which permanent magnets are embedded. A rotating shaft 31 of the motor 30 is connected to the column shaft 12a via a speed reduction mechanism 32. The motor 30 is configured to be integrated with the ECU 1. Note that the ECU 1 may be provided separately from the motor 30.

In the assist mechanism 3, the rotational force of the rotating shaft 31 of the motor 30 is transmitted to the column shaft 12a by the deceleration mechanism 32, and causes the rack shaft 13 to reciprocate linearly in the axial direction via the intermediate shaft 12b and pinion shaft 12c. converted into power. This axial force applied to the rack shaft 13 becomes an assist force and changes the steering angle of the wheels 16.

The ECU 1 is connected to the motor 30. A torque sensor 60 and a vehicle speed sensor 70 are connected to the ECU 1. Torque sensor 60 is provided on column shaft 12a. The torque sensor 60 detects the steering torque _Tr generated on the steering shaft 12 based on the driver's operation of the steering wheel 11, and outputs the detected steering torque _Tr to the ECU 1.

The vehicle speed sensor 70 detects a vehicle speed v, which is the traveling speed of the vehicle, and outputs the detected vehicle speed v to the ECU 1. The ECU 1 controls the current supplied to the motor 30 by vector control based on the detection results from the torque sensor 60, vehicle speed sensor 70, angular velocity sensor 80 (see FIG. 2), etc., as described later. The output torque T _r2 of the motor 30 is controlled.

The electric power steering system 100 is a system that allows the ECU 1 to control the drive of the motor 30 to apply the force obtained by rotating the motor 30 to the steering shaft 12 via the deceleration mechanism 32. . The electric power steering system 100 can assist the driver in steering, and can also suppress vibrations of the steering wheel 11 caused by external forces applied to the wheels 16.

[Electrical configuration of ECU1]
Next, the electrical configuration of the ECU 1 will be explained with reference to FIGS. 2 and 3. FIG. 2 is a block diagram showing the electrical configuration of the ECU 1. FIG. 3 is a block diagram showing the electrical configuration of the control section 5. As shown in FIG.

As shown in FIG. 2, the ECU 1 includes a control section 5, an inverter circuit 20, and a cutoff circuit 40.

As shown in FIG. 2, a torque sensor 60, a vehicle speed sensor 70, an angular velocity sensor 80, and a memory 90 are electrically connected to the ECU 1. The control unit 5 includes, for example, a CPU (Central Processing Unit), and controls the inverter circuit 20 and the cutoff circuit 40 based on the detection results of the torque sensor 60, vehicle speed sensor 70, angular velocity sensor 80, and the like.

The inverter circuit 20 includes an inverter drive section 21 and a bridge circuit 22. The inverter drive unit 21 controls the drive of the bridge circuit 22 using a PWM (Pulse Width Modulation) signal.

The bridge circuit 22 is configured by connecting in parallel a U-phase circuit Cu, a V-phase circuit Cv, and a W-phase circuit Cw corresponding to the U-phase, V-phase, and W-phase of the motor 30, respectively. The bridge circuit 22 is connected to the positive side of the power source 50 via the power line Lh, and is grounded to the negative side of the power source 50 via the ground line Ll. Power supply 50 supplies DC power to inverter circuit 20 via power line Lh. The power source 50 is, for example, a secondary battery (battery).

In the U-phase circuit Cu, a first semiconductor switching element Quh and a second semiconductor switching element Qul are connected in series. In the V-phase circuit Cv, a third semiconductor switching element Qvh and a fourth semiconductor switching element Qvl are connected in series. In the W-phase circuit Cw, a fifth semiconductor switching element Qwh and a sixth semiconductor switching element Qwl are connected in series. The first to sixth semiconductor switching elements Quh, Qvh, Qwh, Qul, Qvl, and Qwl are MOSFETs (metal oxide semiconductor field effect transistors).

The inverter drive unit 21 outputs a PWM signal to the U-phase circuit Cu, V-phase circuit Cv, and W-phase circuit Cw of the bridge circuit 22, thereby controlling the first to sixth semiconductor switching elements Quh, Qvh, Qwh, Qul. , Qvl, and Qwl are turned on and off.

A first semiconductor switching element Quh, a third semiconductor switching element Qvh, and a fifth semiconductor switching element Qwh are connected to the high potential side of the inverter drive unit 21. A second semiconductor switching element Qul, a fourth semiconductor switching element Qvl, and a sixth semiconductor switching element Qwl are connected to the low potential side of the inverter drive section 21. Note that the semiconductor switching element provided on the high potential side is also referred to as an upstream semiconductor switching element, and the semiconductor switching element provided on the low potential side is also referred to as a downstream semiconductor switching element.

A drain D of each of the first semiconductor switching element Quh, the third semiconductor switching element Qvh, and the fifth semiconductor switching element Qwh is connected to the power supply line Lh side. A capacitor C and a relay Ry are provided between the power line Lh and the power source 50. Relay Ry is a relay that opens and closes a power supply path from power supply 50 to inverter circuit 20.

The source S of the first semiconductor switching element Quh is connected to the drain D of the second semiconductor switching element Qul. The source S of the third semiconductor switching element Qvh is connected to the drain D of the fourth semiconductor switching element Qvl. The source S of the fifth semiconductor switching element Qwh is connected to the drain D of the sixth semiconductor switching element Qwl. Further, the sources S of each of the second semiconductor switching element Qul, the fourth semiconductor switching element Qvl, and the sixth semiconductor switching element Qwl are connected to the ground line Ll side.

A first current detector Ru that detects a current value Iu flowing in the U phase of the motor 30 is provided between the source S of the second semiconductor switching element Qul and the ground. A second current detector Rv that detects a current value Iv flowing in the V phase of the motor 30 is provided between the fourth semiconductor switching element Qvl and the ground. A third current detector Rw that detects a current value Iw flowing in the W phase of the motor 30 is provided between the sixth semiconductor switching element Qwl and the ground.

U-phase current value Iu detected by the first current detector Ru, V-phase current value Iv detected by the second current detector Rv, and W-phase current value detected by the third current detector Rw. Iw is output to the inverter drive section 21.

A connection point j1 between the first semiconductor switching element Quh and the second semiconductor switching element Qul is connected to the U phase of the motor 30 via the cutoff circuit 40. A connection point j2 between the third semiconductor switching element Qvh and the fourth semiconductor switching element Qvl is connected to the V phase of the motor 30 via the cutoff circuit 40. A connection point j3 between the fifth semiconductor switching element Qwh and the sixth semiconductor switching element Qwl is connected to the W phase of the motor 30 via the cutoff circuit 40.

The cutoff circuit 40 is a circuit for cutting off electricity between the inverter circuit 20 and the motor 30. The cutoff circuit 40 has a cutoff circuit drive section 41 . The cutoff circuit drive unit 41 operates the first cutoff semiconductor switching element Zu, the second cutoff semiconductor switching element Zv, and the third cutoff semiconductor switching element based on the control signal from the control unit 5 and the detection result by the angular velocity sensor 80. Controls on and off of element Zw.

The sources of the first cutoff semiconductor switching element Zu, the second cutoff semiconductor switching element Zv, and the third cutoff semiconductor switching element Zw are connected to connection points j1, j2, and j3, respectively. The respective drains of the first cutoff semiconductor switching element Zu, the second cutoff semiconductor switching element Zv, and the third cutoff semiconductor switching element Zw are connected to the U phase, V phase, and W phase of the motor 30, respectively.

The cutoff circuit drive unit 41 energizes or cuts off the current between each phase of the inverter circuit 20 and each phase of the motor 30 . Note that the provision of three semiconductor switching elements for interruption is not limited to the provision of three semiconductor switching elements for interruption, such as the first semiconductor switching element for interruption Zu, the second semiconductor switching element for interruption Zv, and the third semiconductor switching element for interruption Zw. There may be. In this case, the motor 30 can be energized by turning on the two cutoff semiconductor switching elements.

The angular velocity sensor 80 detects the rotation angle θ of the rotation shaft 31 of the motor 30. The angular velocity sensor 80 is, for example, a magnetic sensor such as an MR sensor. The angular velocity sensor 80 detects the rotational speed ω of the rotational shaft 31 based on calculating a temporal change in the detected rotational angle θ of the rotational shaft 31. The rotation angle θ and the rotation speed ω can be detected by various known methods. The angular velocity sensor 80 outputs the detected rotation angle θ and rotation speed ω to the control unit 5 of the ECU 1.

The memory 90 stores various control programs and various data. The control unit 5 of the ECU 1 controls the motor 30 by controlling the bridge circuit 22 via the inverter drive unit 21 based on the input steering torque T _r , vehicle speed v, rotation speed ω, rotation angle θ, etc. Control the drive.

[Motor control method using ECU]
Next, a method for controlling the motor 30 by the ECU 1 will be described in detail with reference to FIGS. 3 to 10. As shown in FIG. 3, the control unit 5 includes a target torque determination unit 51, a dq-axis target current determination unit 52, a detection current conversion unit 53, a current control unit 54, and a voltage conversion unit 55. There is.

As shown in FIG. 4, the ECU 1 performs a target torque determination step (S1), a d-axis current command value determination step (S2), an inductance value determination step (S3), and a q-axis current command value step (S4). , control step (S5) are performed in order.

In S1, the target torque determining unit 51 determines a target torque T _r1 to be generated by the motor 30 based on the vehicle speed v output from the vehicle speed sensor 70 and the steering torque T _r output from the torque sensor 60. Specifically, the target torque determination unit 51 determines the target torque T _r1 such that, for example, when the vehicle speed v is high, the target torque T _r1 is smaller than when the vehicle speed v is low.

Furthermore, the detected current converter 53 converts the three-phase current values output from the inverter drive unit 21 into two-phase current values in the dq coordinate system based on the rotation angle θ output from the angular velocity sensor 80. That is, the detection current converter 53 converts the U-phase current value Iu, the V-phase current value Iv, and the W-phase current value Iw into a d-axis current value I d that is the d-axis current value, and a q-axis current value I _d , which is the d-axis current value. It is converted into a q-axis current value _Iq , which is a current value. The d-axis current value I _d and the q-axis current value I _q converted by the detection current conversion unit 53 are output to the dq-axis target current determination unit 52 and the current control unit 54 .

Subsequently, the dq-axis target current determination unit 52 calculates the target torque T _r1 determined by the target torque determination unit 51 , the rotational speed ω output from the angular velocity sensor 80 , and the d-axis current value output from the detected current conversion unit 53 Based on I _d and the q-axis current value I _q , a d-axis current command value I _d1 , which is a d-axis current command value, is determined (S2). After that, the dq-axis target current determination unit 52 determines the q-axis current command value _Iq1 (S4). The d-axis current command value I _d1 and the q-axis current command value I _q1 determined by the dq-axis target current determination section 52 are output to the current control section 54 . A specific method for determining the d-axis current command value I _d1 and the q-axis current command value I _q1 by the dq-axis target current determination unit 52 will be described later.

Next, the current control unit 54 calculates the deviation between the input d-axis current value I _d and q-axis current value I _q and the d-axis current command value I _d1 and the q-axis current command value I _q1 . Then, the current control unit 54 performs PI (proportional integral) control so that the calculated deviation approaches 0, thereby controlling the d-axis voltage command values V _d1 and q, which are the two-phase voltage command values of the dq coordinate system. The shaft voltage command value V _q1 is calculated and output to the voltage converter 55 .

The voltage conversion unit 55 converts the two-phase d-axis voltage command value V _d1 and the q-axis voltage command value V _q1 based on the rotation angle θ output from the angular velocity sensor 80 into the three-phase (U phase, V phase, W phase) to the voltage command value. That is, the voltage converter 55 converts the d-axis voltage command value V _d1 and the q-axis voltage command value V _q1 into the U-phase voltage command value Vu ₁ , the V-phase voltage command value Vv ₁ , and the W-phase voltage command value Vw1. The converted voltage command values Vu ₁ , Vv ₁ , Vw ₁ of each phase are output to the inverter drive unit 21 .

Here, the dq-axis target current determining section 52 of FIG. 3 will be explained with reference to FIG. 5. As shown in FIG. 5, the dq-axis target current determining section includes an ABS (Absolute) 21, an Id determining section 522, an inductance determining section 523, an Iq determining section 524, an Iq limit determining section 525, and an Iq limiting section 526. It has

The rotation speed ω of the motor 30 detected by the angular velocity sensor 80 is input to the ABS 521 . The ABS 521 outputs the input absolute value |ω| of the rotational speed ω to the Id determining unit 522. The absolute value |ω| of the rotational speed ω of the motor 30 and the target torque T _r1 determined by the target torque determining unit 51 are input to the Id determining unit 522 .

In S2, the Id determining unit 522 generates information (hereinafter referred to as a map) indicating the correspondence relationship between the rotational speed ω and the target torque _Tr1 , the preset rotational speed ω and the target torque _Tr1 , and the d-axis current command value _Id1 . This is a first determining unit that determines the d-axis current command value I _d1 based on the information).

Here, FIG. 6 is a graph illustrating map information showing the correspondence between the rotation speed ω, the target torque T _r1 , and the d-axis current command value I _d1 . The map information is stored in the memory 90 in advance. Specifically, the Id determining unit 522 selects the d-axis current command value corresponding to the input rotational speed ω from among the correspondence relationships set for the target torque closest to the value of the input target torque _Tr1 . Find I _d1 .

Note that in this embodiment, as described above, the absolute value |ω| of the rotational speed ω is used as a parameter. As a result, even if the rotation direction of the motor 30 is in the opposite direction, it is possible to determine the d-axis current command value I _d1 using the same correspondence as in the forward direction, and the capacity occupied by the map information in the memory 90 is reduced. It becomes possible to suppress this.

In this embodiment, considering that the influence of the induced electromotive force increases as the rotational speed ω of the motor 30 increases, the influence of the induced electromotive force is reduced by adding a negative current as the d-axis current command value I _d1 . The influence of the rotational speed ω of the motor 30 on the output torque T _r2 of the motor 30 is suppressed.

Here, the correspondence between the rotational speed ω, the target torque T _r1 , and the d-axis current command value I _d1 will be explained in detail with reference to FIG. 7. FIG. 7 is a graph showing switching of control of the motor 30 according to the rotational speed ω of the motor 30. As shown in FIG. 7, in this embodiment, the control unit 5 of the ECU 1 performs MTPA (Maximum Torque Per Ampere) control (maximum torque/current control) and FW (Flux Weakening control) according to the rotational speed ω of the motor 30. ) control (field weakening control). The MTPA control is a control that allows the motor 30 to obtain the maximum output torque T _r2 with a current of the same amplitude. MTPA control is also referred to as maximum torque control. The FW control is a control that makes the negative direction d-axis current command value I _d1 stronger than the MTPA control, that is, it makes it larger.

Specifically, the ECU 1 performs the MTPA control when the rotation speed ω of the motor 30 is equal to or lower than the base rotation speed ω ₀ . Further, when the rotational speed ω of the motor 30 is greater than the base rotational speed ω ₀ and less than the output limit rotational speed ω ₁ during MTPA control, the ECU 1 performs MTPA control and FW control according to the target torque _Tr1 . Switch.

During MTPA control, the d-axis current command value I _d1 is determined based on equation (1) shown below. In equation (1), K _e represents a back electromotive force coefficient, L _q represents a q-axis inductance value, and L _d represents a d-axis inductance value.

On the other hand, the ECU 1 performs FW control when the rotational speed ω of the motor 30 is larger than the output limit rotational speed _ω1 . At the time of FW control, the d-axis current command value I _d1 is determined based on equation (2) shown below. In Equation (2), Vm indicates a limit voltage value determined by the motor 30 standard.

In this way, the graph of FIG. 6 can be created by determining I _d for each rotational speed ω of the motor 30 based on the above equations (1) and (2).

Returning to FIG. 5, the d-axis current value I _d and the q-axis current value I _q are input to the inductance determination unit 523 from the detection current conversion unit 53 . In S3, the inductance determining unit 523 determines the input d-axis current value Id and _q -axis current value _Iq , predetermined d-axis current value _Id , q-axis current value _Iq , and d-axis inductance value L. The d-axis inductance value L _d is determined based on the correspondence relationship with _d . Furthermore, the inductance determination unit 523 determines the input d-axis current value Id and _q -axis current value _Iq , predetermined d-axis current value _Id and q-axis current value _Iq , and q-axis inductance value _Lq. The q-axis inductance value _Lq is determined based on the correspondence relationship between Lq and Lq. Inductance determining section 523 is a third determining section.

FIG. 8 is a graph showing the correspondence between the d-axis current value I _d and the d-axis inductance value L _d for each q-axis current value I _q . In the correspondence between the d-axis current value I _d and the q-axis current value I _q and the d-axis inductance value L _d , the higher each current value is, the smaller the d-axis inductance value L _d becomes. FIG. 9 is a graph showing the correspondence between the q-axis current value _Iq and the q-axis inductance value _Lq for each _d -axis current value Id. In the correspondence between the d-axis current value I _d and the q-axis current value I _q and the q-axis inductance value L _q , the higher each current value is, the smaller the q-axis inductance value L _q becomes.

The target torque T _r1 and the d-axis current command value I _d1 determined by the Id determining unit 522 are input to the Iq determining unit 524 . Further, the d-axis inductance value L _d and the q-axis inductance value L _q determined by the inductance determination unit 523 are input to the inductance determination unit 523 .

In S4, the Iq determining unit 524 substitutes the target torque T _r1 , the d-axis current command value I _d1 , the d-axis inductance value L _d , and the q-axis inductance value L _q into the following equation (3). This is a second determining unit that determines the q-axis current command value _Iq1 . In equation (3), Pn indicates the number of magnetic pole pairs consisting of N and S poles of the permanent magnets of the motor 30. K _e indicates a back electromotive force coefficient.

The Iq limit determining unit 525 determines the Iq limit by using the following equation (4). Here, I _{q_lim} is a limit value of the q-axis current value I _q (see FIG. 10). I _{dq_lim} is the maximum current value that is allowed to flow through the motor 30 and is set in advance according to the standard. The d-axis current value I _d is the d-axis current command value determined by the Id determination unit 522.

The Iq limiter 526 determines whether the value of the q-axis current command value _Iq1 determined by the Iq determiner 524 is within a predetermined range. The "predetermined range" is a range in which the q-axis current command value I _q1 is greater than or equal to -I _{q_lim} and less than or equal to I _{q_lim} . _{Iq_lim} is a predetermined value. When the Iq limiter 526 determines that the q-axis current command value _Iq1 is not within a predetermined range, it sets the q-axis current command value to a limit value _{Iq_lim} that is a value within a predetermined range.

On the other hand, when determining that the q-axis current command value I _q1 is within the predetermined range, the Iq limiting unit 526 sets the q-axis current command value to I _q1 determined in S4. The Iq limiter 526 outputs the q-axis current command value _Iq1 or the limit value _{Iq_lim} to the current controller 54.

Returning to FIG. 3, the d-axis current command value I _d1 and the q-axis current command value I _q1 are input to the current control unit 54. In FIG. 4, the current control unit 54 of the control unit 5 controls the motor 30 via the inverter drive unit 21, as shown below, based on the d-axis current command value I _d1 and the q-axis current command value I _q1 . Control the drive (S5: control step).

The d-axis current value I _d and the q-axis current value I _q converted by the detected current conversion unit 53 are input to the current control unit 54 . The current control unit 54 calculates the deviation between the d-axis current value I _d and the q-axis current value I _q , and the d-axis current command value I _d1 and the q-axis current command value I _q1 , and determines when the calculated deviation becomes 0. Perform PI (proportional integral) control to approach the target. Then, the current control unit 54 calculates a d-axis voltage command value V _d1 and a q-axis voltage command value V _q1 , which are two-phase voltage command values of the dq coordinate system, and outputs them to the voltage conversion unit 55.

The voltage converter 55 converts the d-axis voltage command value V _d1 and the q-axis voltage command value V _q1 into the U-phase voltage command value Vu ₁ and the V-phase voltage based on the rotation angle θ output from the angular velocity sensor 80. The command value Vv ₁ is converted into a voltage command value Vw ₁ for the W phase, and the converted voltage command values Vu ₁ , Vv ₁ , Vw ₁ for each phase are output to the inverter drive unit 21 . As shown in FIG. 2, the inverter drive section 21 controls the drive of the motor 30 via the bridge circuit 22 based on each voltage command value Vu ₁ , Vv ₁ , Vw ₁ from the control section 5 .

In this way, the ECU 1 controls the drive of the motor 30 while switching between MTPA control and FW control according to the rotation speed ω of the motor 30, as shown in FIG. is increased from ω ₁ to ω ₂ , thereby making it possible to suppress a decrease in the output torque T _r2 due to a change in the rotational speed ω of the motor 30.

[Effects of embodiment]
As explained above, in the ECU 1 of this embodiment, the d-axis current command value I _d1 is determined by acquiring the rotational speed ω of the motor 30 in addition to the target torque _Tr1 (S2: d-axis current command value decision step). Then, the q-axis current command value I _q1 is determined based on the target torque T _r1 and the d-axis current command value I _d1 determined in S2 (S4: q-axis current determination step). Thereby, it is possible to suppress the output torque T _r2 from decreasing with respect to the target torque T _r1 due to the influence of the induced electromotive force generated as the motor 30 rotates. Therefore, the influence of the rotational speed ω of the motor 30 on the output torque T _r2 can be suppressed.

Further, the ECU 1 determines the d-axis inductance value L _d and the q-axis inductance value L _q of the motor 30 based on the d-axis current value I _d and the q-axis current value I _q flowing through the motor 30 (S3: Inductance value determination step). Then, the Iq determining unit 524 determines the q-axis current command value I _q1 by using the d-axis inductance value L _d and the q-axis inductance value L _q (S4). Thereby, by using the d-axis current value I _d and the q-axis current value I _q that actually flow through the motor 30, the d-axis inductance value L _d and the q-axis inductance value L _q can be accurately calculated.

Furthermore, if the q-axis current command value I _q1 is not within a predetermined range, the Iq-limiting unit 526 sets the q-axis current command value I _q1 to a limit value I _{q_lim} . As a result, if the q-axis current command value I _q1 becomes a current command value higher than the standard value of the power supply 50, it is possible to prevent a phenomenon in which desired currents do not flow in the d-axis and q-axis as a result. It can be prevented.

In this embodiment, since the motor 30 is an internal permanent magnet synchronous motor, field weakening control can be easily performed by using two types of torque, magnet torque and reluctance torque.

[Other embodiments]
In the embodiment described above, it is assumed that the motor 30 is disposed between the motor 30 and the steering shaft 12, but the present invention is not limited thereto. For example, steering assistance may be performed by disposing a speed reduction mechanism 32 between the motor 30 and the rack and pinion mechanism 14 and transmitting the force of the motor 30 to the rack and pinion mechanism 14 via the speed reduction mechanism 32. good.

Further, in the embodiment described above, the target torque determining unit 51 determines the target torque T _r1 based on the vehicle speed v and the steering torque T _r , but the present invention is not limited thereto. For example, the target torque determination unit 51 may determine the target torque T _r1 using the target steering angle and the steering angle.

Further, in the above embodiment, the graph shown in FIG. 6 is created based on equations (1) and (2), but the graph is not limited to this. The graph shown in FIG. 6 may be created based on the above.

Further, in the above embodiment, a case has been described in which the motor control device of the present invention is applied to the ECU 1 of the electric power steering system 100, but the present invention is not limited to this, and the power transmission between the steering wheel 11 and the wheels 16 is separated. It can also be applied as a motor control device in steer-by-wire systems and automatic driving systems.

Further, in the above embodiment, an internal permanent magnet synchronous motor is used as the motor 30, but the present invention is not limited to this, and for example, a synchronous reluctance motor may be used.

The present invention is not limited to the embodiments described above, and can be modified in various ways within the scope of the claims, and can be implemented by appropriately combining technical means disclosed in different embodiments. The form is also included within the technical scope of the present invention.

1 ECU
5 Control section 20 Inverter circuit 21 Inverter drive section 22 Bridge circuit 30 Motor 50 Power source 51 Target torque determination section 52 dq axis target current determination section 522 Id determination section 523 Inductance determination section 524 Iq determination section 526 Iq restriction section 60 Torque sensor 70 Vehicle speed Sensor 80 Angular velocity sensor 100 Electric power steering system T _r steering torque T _r1 target torque T _r2 output torque ω rotational speed v vehicle speed

Claims (9)

a target torque determination unit that determines a target torque that is a target torque of the motor;
A d-axis current command value, which is a current command value of the d-axis of the motor, is set in advance for the rotational speed of the motor, the target torque determined by the target torque determination unit, and the rotational speed of the motor and the target torque. a first determining unit that determines the d-axis current command value of the motor based on the associated information;
a q-axis current command value of the q-axis of the motor based on the d-axis current command value determined by the first determination unit, the target torque determined by the target torque determination unit, and a predetermined relational expression; a second determining unit that determines a current command value;
a control unit that controls driving of the motor based on the d-axis current command value and the q-axis current command value;
A motor control device comprising: A d-axis inductance value and a q-axis inductance value of the motor are determined based on a d-axis current value that is a d-axis current value flowing in the motor, and a q-axis current value that is a q-axis current value flowing in the motor. further comprising a third determining unit that determines the
The motor control device according to claim 1, wherein the second determining unit determines the q-axis current command value based on the d-axis inductance value and the q-axis inductance value. The control unit includes:
maximum torque control that controls the maximum torque to be output with a current of the same amplitude according to the rotational speed; and field weakening control that makes the d-axis current command value in the negative direction larger than the maximum torque control. to control the drive of the motor,
The d-axis current command value in the information is the d-axis current command value I _d1 , the back electromotive force coefficient K _e , the d-axis inductance value L _d , the q-axis inductance value L _q , and the When the q-axis current value flowing through the motor is _Iq , the limit voltage value of the motor is Vm, and the rotational speed value is ω,
At the time of the maximum torque control, it is obtained by using the following formula (1),
The motor control device according to claim 1, wherein the field weakening control is determined by using the following equation (2).

The second determining unit is
The q-axis current command value is I _q , the target torque value is T _r1 , the number of magnetic pole pairs consisting of N and S poles of the permanent magnet of the motor is P _n , the back electromotive force coefficient is K _e , and the above d When the axis inductance value is L _d , the q-axis inductance value is L _q , and the d-axis current command value is I _d1 , the q-axis current command value is determined by using the following equation (3). The motor control device according to claim 1, characterized in that:

5. The motor control device according to claim 4, wherein when the q-axis current command value is not within a predetermined range, the q-axis current command value is set to a value within the predetermined range. The control unit receives a value of a steering torque generated as a result of operation of a steering wheel of a vehicle, and a vehicle speed value that is a speed of the vehicle;
The motor control according to any one of claims 1 to 5, wherein the target torque determining unit determines the target torque based on the input value of the steering torque and the vehicle speed value. Device. a target torque determining step of determining a target torque that is a target torque of the motor;
A d-axis current command value that is a d-axis current command value of the motor is determined with respect to the rotational speed of the motor, the target torque determined in the target torque determination step, and the rotational speed of the motor and the target torque. a d-axis current command value determining step of determining the d-axis current command value of the motor based on information associated with each other in advance;
A q-axis current command of the motor based on the d-axis current command value determined in the d-axis current command value determination step, the target torque determined in the target torque determination step, and a predetermined relational expression. a q-axis current command value determining step for determining a q-axis current command value that is a value;
a control step of controlling the drive of the motor based on the d-axis current command value and the q-axis current command value;
A motor control method comprising: Determining a d-axis inductance value, which is a d-axis inductance value, and a q-axis inductance value, which is a q-axis inductance value, of the motor, based on a d-axis current value and a q-axis current value flowing through the motor. further comprising an inductance value determination step;
In the q-axis current command value determining step, the q-axis current command value is determined based on the d-axis inductance value determined in the inductance value determining step and the q-axis inductance value. The motor control method according to item 7. 9. The q-axis current command value determining step sets the q-axis current command value to a value within the predetermined range if the q-axis current command value is not within the predetermined range. motor control method.

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