Motor control device

Abstract

A motor control device (12) includes a second setting unit configured to set an armature current command value and a current phase angle command value based on a rotational speed and a motor torque command value, and a current vector setting unit configured to set a d-axis current command value and a q-axis current command value based on the armature current command value and the current phase angle command value. The second setting unit is configured to set the armature current command value and the current phase angle command value so that an armature current vector set based on the d-axis current command value and the q-axis current command value is included in an area enclosed by an armature current vector locus in maximum torque / current control and a vertical axis in a d-q coordinate system.

Description

TECHNICAL FIELD

[0001] The present application relates to a motor control device that controls a motor in which a rotor rotates using reluctance torque (hereinafter also referred to as "motor using reluctance torque"). Examples of the motor using reluctance torque include, in addition to a reluctance motor in which a rotor rotates using only reluctance torque, a motor in which a rotor rotates using reluctance torque and magnet torque. BACKGROUND

[0002] A reluctance motor that rotates a rotor using only reluctance torque is known. Examples of the reluctance motor include a switched reluctance motor (SRM) including a rotor and a stator having a salient pole portion and a synchronous reluctance motor (SynRM) having a stator having the same structure as a brushless motor.

[0003] In the stator and the rotor of the synchronous reluctance motor, only the rotor includes the salient pole portion. In the synchronous reluctance motor, due to the salient pole portion of the rotor, there are a direction of the salient pole portion in which magnetic flux easily flows (hereinafter referred to as "d-axis direction") and a direction of the non-salient pole portion in which magnetic flux does not easily flow (hereinafter referred to as "q-axis direction"). Therefore, due to a difference (L d -L q ) between inductance in the d-axis direction (hereinafter referred to as "d-axis inductance L d -L q "), a reluctance torque is generated, and the rotor rotates by the reluctance torque.

[0004] WO 2019-017231 discloses a control method of controlling a synchronous reluctance motor in which maximum torque / current control using a maximum torque table and maximum output / speed control using a high output table are switched based on a rotational speed. In the maximum torque table, motor torque generated from the motor is stored with respect to a combination of an armature current command value and a current phase angle command value in which, for each armature current command value, the motor torque is maximized at the current phase angle command value at which the armature current command value. In the high output table, a combination of an armature current command value and a current phase angle command value in which the motor torque is maximized is stored for each rotational speed of the motor.

[0005] When the rotational speed of the motor is in a low rotational speed region equal to or lower than a predetermined rotational speed (for example, in a constant torque region), maximum torque / current control is executed. Specifically, an armature current command value and a current phase angle command value are calculated based on a maximum torque table such that a motor torque corresponding to a motor torque command value is generated from the motor, and the motor is controlled based on the calculated armature current command value and the calculated current phase angle command value.

[0006] On the other hand, when the rotational speed of the motor is in a high rotational speed region higher than the predetermined rotational speed (for example, in a constant output region), maximum output / speed control is executed. Specifically, an armature current command value and a current phase angle command value are calculated based on a high output table with which a motor torque is maximized at a current rotational speed, and the motor is controlled based on the calculated armature current command value and the calculated current phase angle command value. SUMMARY

[0007] In the control method described in WO 2019 / 017231, in the high rotational speed region in which maximum output / speed control is executed, a maximum torque can be output, but a motor torque corresponding to a motor torque command value cannot be output. The present invention provides a motor control device that can output a maximum torque and output a motor torque corresponding to a motor torque command value in all rotational speed regions.

[0008] According to an aspect of the present invention, there is provided a motor control device that controls a motor using a reluctance torque. The motor control device includes a first setting unit configured to set a motor torque command value that is a command value of a motor torque to be generated from the motor, a rotational speed detection unit configured to detect a rotational speed of the motor, a second setting unit configured to set an armature current command value and a current phase angle command value based on the rotational speed and the motor torque command value, a current vector setting unit configured to set a d-axis current command value and a q-axis current command value based on the armature current command value and the current phase angle command value, and a drive unit configured to drive the motor based on the d-axis current command value and the q-axis current command value. The second setting unit is configured to set the armature current command value and the current phase angle command value such that an armature current vector set based on the d-axis current command value and the q-axis current command value is included in a region enclosed by an armature current vector locus in maximum torque / current control and a vertical axis in a d-q coordinate system that is a d-axis current on a horizontal axis and a q-axis current on the vertical axis.

[0009] According to this aspect, the maximum torque can be output and the motor torque corresponding to the motor torque command value can be output in all rotational speed regions. The motor control device according to this aspect can further include a first table in which motor torques generated from the motor are stored in association with combinations of the armature current command value and the current phase angle command value, where the motor torque is maximized at the current phase angle command value at the corresponding armature current command value, and a second table in which the armature current command value, the current phase angle command value, and the motor torque at a plurality of operating points on a voltage limit ellipse are stored in association for each rotational speed of the motor. The second setting unit can be configured to calculate a first candidate of the armature current command value and the current phase angle command value based on the motor torque command value and the first table, calculate a second candidate of the armature current command value and the current phase angle command value based on the rotational speed, the motor torque command value, and the second table, set the armature current command value and the current phase angle command value of the first candidate as the command values in a case where the current phase angle command value of the first candidate is equal to or greater than the current phase angle command value of the second candidate, and set the armature current command value and the current phase angle command value of the second candidate as the command values in a case where the current phase angle command value of the first candidate is less than the current phase angle command value of the second candidate.

[0010] In this configuration, the plurality of operating points on the voltage limit ellipse corresponding to the rotational speed of the motor can include an operating point at which the motor torque is maximized at the rotational speed. The motor control device according to this aspect can further include a first table in which motor torques generated from the motor are stored in association with combinations of the armature current command value and the current phase angle command value, where the motor torque is maximized at the current phase angle command value at the corresponding armature current command value, and a third table in which the armature current command value, the current phase angle command value, and the motor torque at a plurality of third operating points are stored in association for each rotational speed of the motor, the plurality of third operating points including a first operating point at which the motor torque is maximized at the corresponding rotational speed and a plurality of second operating points set in a direction in which the operating point moves from the first operating point when the terminal-to-terminal voltage of the motor decreases. The second setting unit can be configured to set the armature current command value and the current phase angle command value based on the motor torque command value and the first table in a case where the rotational speed is equal to or lower than a predetermined value, and set the armature current command value and the current phase angle command value based on the rotational speed, the motor torque command value, and the third table in a case where the rotational speed is higher than the predetermined value.

[0011] In this configuration, in the d-q coordinate system, the plurality of third operating points can be set on a straight line connecting a convergence point and the first operating point at the corresponding rotational speed, the convergence point being set as the origin of the d-q coordinate system or a predetermined point close to the origin, for each rotational speed. BRIEF DESCRIPTION OF DRAWINGS

[0012] Features, advantages, and technical and industrial significance of exemplary embodiments of the application will be described below with reference to the accompanying drawings, wherein the same reference numerals denote the same elements throughout the different drawings, and wherein:

[0013] Figure 1 is a diagram schematically showing a configuration of an electric power steering apparatus to which a motor control device according to an embodiment of the application is applied;

[0014] Figure 2 is a diagram schematically showing a configuration of a motor;

[0015] Figure 3 is a diagram schematically showing Figure 1 an electrical configuration of an ECU (Electronic Control Unit) shown;

[0016] Figure 4 is a graph showing an example of setting a motor torque command value T h with respect to a detected steering torque T s *;

[0017] Figure 5 is a graph showing an example of characteristic data of a motor torque T s with respect to a current phase angle β, which is acquired for each of a plurality of armature currents I a *;

[0018] Figure 6 is a diagram schematically showing details of a forward rotation table in a command value / maximum torque table, an example;

[0019] Figure 7A is a diagram schematically showing details of a torque command value table, an example;

[0020] Figure 7B is a diagram schematically showing details of a torque command value table, an example;

[0021] Figure 7C is a diagram schematically showing details of a current phase angle command value table, an example;

[0022] Figure 8 is a graph showing a method of preparing a torque command value table, a current command value table, and a current phase angle command value table;

[0023] Figure 9 is a flowchart showing operations performed by a current command value setting unit;

[0024] Figure 10 is a graph showing a method of preparing a torque command value table, a current command value table, and a current phase angle command value table according to a second embodiment; and

[0025] Figure 11 is a flowchart showing operations performed by the current command value setting unit according to the second embodiment. DETAILED DESCRIPTION

[0026] Hereinafter, embodiments of the present application will be described in detail with reference to the attached drawings.

[0027] [1] First Embodiment

[0028] Figure 1 is a diagram schematically showing a configuration of an electric power steering apparatus to which a motor control device according to the first embodiment of the present application is applied. The electric power steering apparatus 1 includes a steering wheel 2 as a steering member for steering a vehicle, a turning mechanism 4 that turns a turning wheel 3 in accordance with a rotation of the steering wheel 2, and a steering assist mechanism 5 that assists a driver in steering. The steering wheel 2 and the turning mechanism 4 are mechanically connected to each other via a steering shaft 6 and an intermediate shaft 7.

[0029] The steering shaft 6 includes an input shaft 8 connected to the steering wheel 2 and an output shaft 9 connected to the intermediate shaft 7. The input shaft 8 and the output shaft 9 are connected via a torsion bar 10 so that they can rotate relative to each other. A torque sensor 11 is provided around the steering shaft 6. The torque sensor 11 detects a steering torque T h input to an electronic control unit (ECU) 12 on the basis of a relative rotational displacement between the input shaft 8 and the output shaft 9. h

[0030] The turning mechanism 4 is constituted by a rack and pinion mechanism including a pinion shaft 13 and a rack shaft 14 as a turning shaft. The turning wheel 3 is connected to an end portion of the rack shaft 14 via tie rods 15 and knuckle arms (not shown). The pinion shaft 13 is connected to the intermediate shaft 7. A pinion 16 is connected to a top end of the pinion shaft 13. The rack shaft 14 extends in a straight line shape in a lateral direction of the vehicle. A rack 17 engaged with the pinion 16 is formed in the middle in an axial direction of the rack shaft 14. Rotation of the pinion shaft 13 is converted into movement of the rack shaft 14 in the axial direction by the pinion 16 and the rack 17. By moving the rack shaft 14 in the axial direction, it is possible to turn the turning wheel 3.

[0031] ​When the steering wheel 2 is steered (rotated), the rotation is transmitted to the pinion shaft 13 via the steering shaft 6 and the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into the movement of the rack shaft 14 in the axial direction by the rack-and-pinion mechanism. Thus, the turning wheels 3 are turned. The steering assist mechanism 5 includes a motor (M) 18 for assisting the steering and a reduction gear 19 that transmits the output torque of the motor 18 to the turning mechanism 4. In this embodiment, the motor 18 is composed of a synchronous reluctance motor. The reduction gear 19 is composed of a worm-and-gear mechanism including a worm 20 and a worm wheel 21 that is engaged with the worm 20. The reduction gear 19 is housed in a gear box 22.

[0032] The worm 20 is rotationally driven by the motor 18. The worm wheel 21 is connected to the steering shaft 6 so that they can rotate as a whole. The worm wheel 21 is rotationally driven by the worm 20. When the worm 20 is rotationally driven by the motor 18, the worm wheel 21 is rotationally driven, and the steering shaft 6 is rotated. The rotation of the steering shaft 6 is transmitted to the pinion shaft 13 via the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into the movement of the rack shaft 14 in the axial direction by the rack-and-pinion mechanism. Thus, the turning wheels 3 are turned. That is, by rotationally driving the worm 20 using the motor 18, steering assist using the motor 18 becomes possible.

[0033] The rotation angle of the rotor of the motor 18 (hereinafter referred to as "rotor rotation angle") is detected by a rotation angle sensor 25 (e.g., resolver). The output signal of the rotation angle sensor 25 is input to the ECU 12. The motor 18 is controlled by the ECU 12 as a motor control device. Figure 2 is a diagram that schematically shows the configuration of the motor 18.

[0034] The motor 18 is a synchronous reluctance motor as described above, and includes a rotor 100 including a plurality of protruding magnetic pole portions arranged at intervals in the circumferential direction, and a stator 105 including an armature winding, as Figure 2 schematically shown. The armature winding has a configuration in which a U-phase stator coil 101, a V-phase stator coil 102, and a W-phase stator coil 103 are star-connected.

[0035] A three-phase fixed coordinate system (UVW coordinate system) having a U-axis, a V-axis, and a W-axis set in the directions of the phase stator coils 101, 102, and 103 is defined. A two-phase rotating coordinate system (d-q coordinate system, actual rotating coordinate system) in which the direction of the d-axis is the direction in which the magnetic flux easily flows from the rotation center of the rotor 100 to the protruding magnetic pole portions of the outer peripheral portion, and the direction of the q-axis is the direction in which the magnetic flux does not easily flow from the rotation center of the rotor 100 to the non-protruding magnetic pole portions of the outer peripheral portion is defined. The d-q coordinate system is an actual rotating coordinate system that corresponds to the rotation angle (rotor rotation angle) θ of the rotor 100.

[0036] In this embodiment, the rotor rotation angle (electrical angle) θ is defined as a rotation angle in a counterclockwise direction from the U-axis to one of the two adjacent salient pole portions (d-axis) that serves as a reference. The direction of the one salient pole portion that serves as a reference is defined as the +d-axis direction, and the direction of the other salient pole portion adjacent thereto is defined as the -d-axis direction. An axis that rotates +90 degrees in electrical angle from the +d-axis is defined as the +q-axis, and an axis that rotates -90 degrees in electrical angle from the +d-axis is defined as the -q-axis. The poles (salient pole portions) generated in the rotor 100 (N-pole and S-pole) are determined by the direction of the current vector I a in the d-q coordinate system. In this embodiment, the forward rotation direction of the motor 18 corresponds to the counterclockwise direction (CCW) of the rotor 100 in Figure 2 , and the reverse rotation direction of the motor 18 corresponds to the clockwise direction (CW) of the rotor 100 in Figure 2 .

[0037] The coordinate conversion between the UVW coordinate system and the d-q coordinate system is performed using the rotor rotation angle θ (see, for example, expressions (1) and (2) in Japanese Unexamined Patent Application Publication No. 2009-137323 (JP 2009-137323 A)). In this specification, the current flowing in the armature winding is referred to as the "armature current" or "motor current". The current vector I a in the d-q coordinate system is the vector of the current flowing in the armature winding (armature current vector). β represents the current phase angle, and is the phase difference between the d-axis and the armature current vector I a . i d represents the d-axis current, and is represented by i d = I a · cos β. i q represents the q-axis current, and is represented by i q = I a · sin β.

[0038] Figure 3 is a diagram schematically showing the electrical configuration of the ECU 12 shown in Figure 1 . The ECU 12 includes a microcomputer 31, a drive circuit (inverter circuit) 32 controlled by the microcomputer 31 and supplying electric power to the motor 18, and current sensors 33, 34, and 35 that detect the U-phase current, the V-phase current, and the W-phase current flowing in the motor 18.

[0039] The microcomputer 31 includes a CPU and memory, and functions as multiple functional processing units by executing predetermined programs. The memory includes ROM, RAM, and non-volatile memory 40. The multiple functional processing units include a torque command value setting unit 41, a current command value setting unit 42, a current vector calculation unit (current vector setting unit) 43, a d-axis current difference calculation unit 44, a q-axis current difference calculation unit 45, a d-axis proportional-integral (PI) control unit 46, a q-axis proportional-integral (PI) control unit 47, a voltage limiting unit 48, a two-phase / three-phase coordinate transformation unit 49, a PWM control unit 50, a current detection unit 51, a three-phase / two-phase coordinate transformation unit 52, a rotation angle calculation unit 53, and a speed calculation unit 54.

[0040] The rotation angle calculation unit 53 calculates the rotation angle (rotor rotation angle θ) of the rotor of the motor 18 based on the output signal of the rotation angle sensor 25. The rotor rotation angle θ calculated by the rotation angle calculation unit 53 is provided to the speed calculation unit 54 and the coordinate transformation units 49 and 52. The speed calculation unit 54 calculates the speed ω [rpm] of the motor 18 by integrating the rotor rotation angle θ calculated by the rotation angle calculation unit 53 with respect to time.

[0041] The current detection unit 51 detects the phase currents i of phases U, V, and W based on the output signals of current sensors 33, 34, and 35. U i V and i W (Hereinafter referred to as "detected three-phase current i") U i V and i W The torque command value setting unit 41 sets the motor torque command value (hereinafter referred to as "torque command value T"). s *”), the motor torque command value is the command value of the motor torque to be generated from motor 18. Specifically, the torque command value setting unit 41 is based on the steering torque (detected steering torque T) detected by torque sensor 11. h Set the torque command value T s * Figure 4 This shows the steering torque T relative to the detected torque. h To set the torque command value T s Example of *. Regarding the detected steering torque T h For example, the torque for left steering is defined as a positive value, and the torque for right steering is defined as a negative value. The direction of the motor torque for left steering of the auxiliary motor 18 is defined as corresponding to the forward rotation direction of the motor 18, and the direction of the motor torque for right steering is defined as corresponding to the reverse rotation direction of the motor 18. When generating steering assist force for left steering from the motor 18, the torque command value T is... s* indicates a positive value, and the torque command value T is used when generating steering assist force from motor 18 for right steering. s * indicates a negative value.

[0042] When the detected steering torque T h When it is positive, the torque command value T s * indicates a positive value, and when the detected steering torque T h When it is negative, the torque command value T s * indicates a negative value. When the detected steering torque T... h When it is 0, the torque command value T s * is 0. With the detected steering torque T h As the absolute value increases, the torque command value T s The absolute value of * increases. Therefore, as the detected steering torque T... h As the absolute value of the steering assist increases, the steering assist force can also increase.

[0043] Torque command value setting unit 41, for example, uses the steering torque T stored therein. h With torque command value T s Mapping of relationships between * or such as Figure 4 The expression shown indicates the calculation of this relationship to set the value corresponding to the steering torque T. h Torque command value T s * The torque command value T set by the torque command value setting unit 41. s *Provided to the current command value setting unit 42 and the current vector calculation unit 43.

[0044] The non-volatile memory 40 stores a command value / maximum torque table 60 and a speed / command value table 70. The command value / maximum torque table 60 is an example of the "first table" in the claims, and the speed / command value table 70 in the first embodiment is an example of the "second table" in the claims. Details of these tables 60 and 70 will be described later. The current command value setting unit 42 is based on the torque command value T. s * Set the armature current command value I in the rotor speed ω and command value / maximum torque table 60 or speed / command value table 70. a *(I a *>0) and the current phase angle command value β* (β*>0). Details of the current command value setting unit 42 will be described later.

[0045] The current vector calculation unit 43 is based on the armature current command value I set by the current command value setting unit 42. a * and current phase angle command value β* and torque command value T s The asterisk (*) is used to calculate the d-axis current command value i. d * and q-axis current command value iq Specifically, the current vector calculation unit 43 calculates the d-axis current command value i d .

[0046] i d * = I a * · cos β * … (1)

[0047] The current vector calculation unit 43 calculates the q-axis current command value i q .

[0048] i q * = I a * · sin β * if T s * ≥ 0 … (2a)

[0049] i q * = I a * · sin (-β *) if T s * < 0 … (2b)

[0050] The d-axis current command value i d * and the q-axis current command value i q * can be collectively referred to as "two-phase command currents i d * and i q *". The three-phase currents i U , i V , and i W detected by the current detection unit 51 are supplied to the three-phase / two-phase coordinate conversion unit 52. The three-phase / two-phase coordinate conversion unit 52 converts the detected three-phase currents i U , i V , and i W to the d-axis current i d and the q-axis current i q in the d-q coordinate system using the rotor rotation angle θ calculated by the rotation angle calculation unit 53 (hereinafter collectively referred to as "detected two-phase currents i d and i q "). The d-axis current i d obtained by the three-phase / two-phase coordinate conversion unit 52 is supplied to the d-axis current difference calculation unit 44. The q-axis current i q obtained by the three-phase / two-phase coordinate conversion unit 52 is supplied to the q-axis current difference calculation unit 45.

[0051] The d-axis current difference calculation unit 44 calculates the difference Δi d (= i d * - i d ) between the d-axis current i d and the d-axis current command value i d). The d-axis PI control unit 46 calculates a d-axis command voltage v d by performing proportional integral (PI) on the current difference Δi d * calculated by the d-axis current difference calculation unit 44. d * is supplied to the voltage limiter unit 48. The q-axis current difference calculation unit 45 calculates a difference Δi q between a q-axis current command value i q * and a q-axis current i q (= i q * - i q ). The q-axis PI control unit 47 calculates a q-axis command voltage v q * by performing proportional integral (PI) on the current difference Δi q * calculated by the q-axis current difference calculation unit 45. q * is supplied to the voltage limiter unit 48.

[0052] The voltage limiter unit 48 is set to avoid a state in which an induced voltage in the motor 18 is higher than a source voltage and a current cannot flow in the motor 18 (voltage saturation state). For example, the voltage limiter unit 48 limits the d-axis command voltage v d * to be equal to or smaller than a preset maximum d-axis voltage command value, and limits the q-axis command voltage v q * to be equal to or smaller than a preset maximum q-axis voltage command value. The d-axis command voltage v d * and the q-axis command voltage v q * subjected to the limiting process of the voltage limiter unit 48 are supplied to the two-phase / three-phase coordinate conversion unit 49.

[0053] The two-phase / three-phase coordinate conversion unit 49 converts the d-axis command voltage v d * and the q-axis command voltage v q * into command voltages v U *, v V *, and v W * of U, V, and W phases using a rotor rotation angle θ calculated by the rotation angle calculation unit 53. The command voltages v U *, v V *, and v W * of U, V, and W phases are collectively referred to as "three-phase command voltages v U *, v V *, and v W * ". The PWM control unit 50 generates duty ratios corresponding to the U-phase command voltage v U *, the V-phase command voltage v V *, and the W-phase command voltage v WThe U-phase PWM control signal, V-phase PWM control signal, and W-phase PWM control signal are generated and provided to the drive circuit 32.

[0054] The drive circuit 32 includes a three-phase inverter circuit corresponding to phases U, V, and W. The power elements constituting the inverter circuit are controlled by PWM control signals from the PWM control unit 50, causing them to operate in accordance with the three-phase command voltage V. U *、v V * and v W The voltage * is applied to the phase stator windings of motor 18. Current difference calculation units 44 and 45, along with PI control units 46 and 47, constitute the current feedback control unit. The motor current (armature current) flowing in motor 18 is controlled by the current feedback control unit to achieve the two-phase command current i calculated by the current vector calculation unit 43. d * and i q *

[0055] The command value / maximum torque table 60, the speed / command value table 70, and the current command value setting unit 42 will be described in detail below. First, the command value / maximum torque table 60 will be described. The command value / maximum torque table 60 includes a forward rotation (CCW) armature current / current phase angle setting table (hereinafter referred to as "forward rotation table 61") and a reverse rotation (CW) armature current / current phase angle setting table (hereinafter referred to as "reverse rotation table 62").

[0056] To effectively drive motor 18, motor 18 only needs to be controlled to increase the ratio of motor torque to armature current. It has the following pole number P. n The motor torque T in a synchronous reluctance motor s It is represented by expression (3).

[0057] T s =P n ·(L d -L q )·i d ·i q …(3)

[0058] L d It is the d-axis inductance [H], and L q It is the q-axis inductance [H]. d It is the d-axis current [A], and i q It is the q-axis current [A].

[0059] When the magnitude of the armature current is defined as I a And when the current phase angle is defined as β, i satisfies q =I a sinβ and i d= I a • cos β, and thus the motor torque T s is expressed by expression (4). The current phase angle β indicates a phase difference between the armature current vector and the d-axis.

[0060] T s = (1 / 2) • P n • (L d - L q ) • I a 2 sin 2β... (4)

[0061] Therefore, when the d-axis inductance L d and the q-axis inductance L q are constant, the motor torque T s is maximized when the current phase angle β is 45 degrees. However, in a synchronous reluctance motor, since the d-axis inductance L d and the q-axis inductance L q change due to magnetic saturation of the rotor core and the stator core, the motor torque T s may not be maximized when the current phase angle β is 45 degrees.

[0062] Figure 5 is a graph showing characteristic data of the motor torque T a with respect to the current phase angle β, which is acquired for each of a plurality of armature currents I s in a certain synchronous reluctance motor. Figure 5 The characteristic data shown reuses data described in Masaru HASEGAWA (Chubu Univ.), Shinji DOKI (Nagoya Univ.), Akiyoshi SATAKE (Okuma Corporation), Daohong WANG (Gifu Univ.), "Drive Circuit Technique and Drive Control Technique of Reluctance Motor of Permanent Magnet Motor - 6. Reluctance Motor Control Technique-," the Institute of Electrical Engineers of Japan, Industrial Application Group Conference, Papers, I-119 to I-124 (2004). In Figure 5 , the horizontal axis is set to the current phase angle β, and the vertical axis is set to the motor torque T sand the motor torque T s with respect to each armature current I a The characteristic of the current phase angle β at which the motor torque T s is maximized is indicated by the curve.

[0063] As Figure 5 indicated, the motor torque T a is maximized at a current phase angle β that differs depending on the magnitude of the armature current I a In the example indicated in Figure 5 , as the armature current I s increases, the current phase angle β at which the motor torque T a is maximized increases. In order to efficiently drive the motor 18, the current phase angle β at which the motor torque T s is maximized is preferably set to the current phase angle β with respect to the armature current command value I a *.

[0064] Figure 6 is a schematic diagram showing an example of details of the forward rotation table 61 in the command value / maximum torque table 60. In the forward rotation table 61, for each armature current command value I a *, the combination of the armature current command value I a * when the motor 18 rotates in the forward rotation direction and the current phase angle command value β* at which the motor torque T s is maximized in that armature current command value I s [Nm] is stored in association with.

[0065] In this example, data of K armature current command values I a * is stored in the forward rotation table 61. The K armature current command values I a * have a relationship of I a1 * < I a2 * < … < I a(K-1) * < I aK *. The motor torque T s increases as the armature current command value I a * increases. For example, the forward rotation table 61 is prepared as follows. When a predetermined armature current command value I a *, a predetermined current phase angle command value β*, and a sign indicating the forward rotation direction are supplied to the current vector calculation unit 43 of the motor control circuit indicated in Figure 3 , the motor 18 generates a motor torque T a based on two-phase command currents i d * and i q corresponding to the armature current command value I *, the current phase angle command value β*, and the sign.* is driven in the forward rotation direction. In a state where the motor 18 is driven in the forward rotation direction, the motor torque T s generated from the motor 18 is acquired (for example, an average value of the motor torque in a predetermined time). Thus, the motor torque T a corresponding to the combination of the predetermined armature current command value I s * and the predetermined current phase angle command value β* is acquired. The motor torque T s is measured using a measuring instrument (not shown).

[0066] By performing this test for each of a plurality of current phase angle command values β*, data of the motor torque T a corresponding to each combination of the predetermined armature current command value I s * and the plurality of current phase angle command values β* is acquired. Based on the acquired data, the current phase angle command value β* at which the motor torque T a is maximized with respect to the predetermined armature current command value I s is identified.

[0067] By performing this test for each of a plurality of armature current command values I a *, for each of the plurality of armature current command values I a *, data of the motor torque T a corresponding to the combination of the armature current command value I s * and the current phase angle command value β* at which the motor torque T s is maximized is acquired. Thus, data for preparing the forward rotation table 61 is acquired. Although not shown, in the reverse rotation table 62, for each armature current command value I a *, the motor torque T a generated from the motor 18 for the armature current command value I a * and the current phase angle command value β* at which the motor torque T s is maximized at the armature current command value I s [Nm] is stored.

[0068] The reverse rotation table 62 is prepared by performing the same test as the test performed for preparing the forward rotation table 61. When preparing the reverse rotation table 62, unlike when preparing the forward rotation table 61, a sign indicating the reverse rotation direction at the time of the test is provided to the current vector calculation unit 43. Thus, the motor 18 is driven in the reverse rotation direction at the time of the test.

[0069] Based on the forward rotation table 61 or the reverse rotation table 62, the armature current command value I s corresponding to the torque command value T a* and current phase angle refer to the command value β* and are based on the acquired armature current command value I. a The method of controlling motor 18 using the acquired current phase angle command value β* is called "maximum torque / current control". The speed / command value table 70 will be described below. Figure 3 and Figure 7A to 7C As shown, the speed / command value table 70 includes a torque command value table 71, a current command value table 72, and a current phase angle command value table 73.

[0070] In the torque command value table 71, the speeds ω1 to ω2 of the motor 18 are specified. N Each of the storage units contains multiple motor torques T. sn1 To T snM ,like Figure 7A As shown. N represents the number of speed data entries, and M represents the motor torque T set for each speed. s The number of data entries. In the leftmost column of Torque Command Value Table 71, 1 to N represent the index number n of the speed (hereinafter referred to as "speed number"). In the top row of Torque Command Value Table 71, 1 to M represent the index number m of the motor torque (hereinafter referred to as "torque number").

[0071] In the current command value table 72, such as Figure 7B As shown, for each of the speed numbers 1 to N, multiple armature current command values ​​I are stored corresponding to torque numbers 1 to M. an1 * to I anM *.like Figure 7C As shown, in the current phase angle command value table 73, for each of the speed numbers 1 to N, multiple current phase angle command values ​​β corresponding to torque numbers 1 to M are stored. n1 *to β nM *. The following will refer to Figure 8 Describe the method for preparing Tables 71 to 73.

[0072] Figure 8 This illustrates a dq coordinate system with the d-axis current on the horizontal axis and the q-axis current on the vertical axis. Figure 8 In the diagram, curve A represents the trajectory of the armature current vector during maximum torque / current control. Curve A can be prepared, for example, as follows: Figure 6 The command values / maximum torque are shown in Table 60, assuming for each armature current I a The current phase angle β at which the motor torque is maximized is obtained in advance.

[0073] Based on i d =I a ·cosβ and i q =I a ·sinβ, for each armature current I aThe d-axis current command value and the q-axis current command value for the current phase angle β at which the motor torque is maximized are calculated. Then, for each armature current I a The end points of the armature current vector (hereinafter referred to as "operation points") corresponding to the d-axis current command value and the q-axis current command value for the current phase angle β at which the motor torque is maximized are plotted on the d-q coordinate system. A curve passing through these points is plotted to obtain a curve A.

[0074] In Figure 8 , curves B1 to B8 represent the trajectories of the armature current vector when the current phase angle is varied at 8 rotational speeds that differ from each other by a predetermined value (200 rpm in this example) within a predetermined range of rotational speed (a range from 1600 rpm to 3000 rpm in this example). The right end (lower end) of each curve represents the operation point when the current phase angle is 45 degrees. The left end (upper end) of each curve represents the operation point at which the motor torque is maximized.

[0075] Curve B1 is the trajectory of the armature current vector corresponding to 1600 rpm, curve B8 is the trajectory of the armature current vector corresponding to 3000 rpm, and the magnitude of the armature current vector when the current phase angle is 45 degrees decreases as the rotational speed increases. Curve C represents a straight line passing through the operation points on curves B1 to B8 when the current phase angle is 45 degrees. For example, curve B1 can be plotted as follows.

[0076] The maximum value of the armature current command value I a * and the predetermined current phase angle command value β* are supplied to the current vector calculation unit 43 of the motor control circuit shown in Figure 3 to drive the motor 18. Then, the load is adjusted so that the rotational speed reaches a predetermined rotational speed (1600 rpm at which curve B1 is prepared). While the current phase angle command value β* is slightly increased from 45 degrees, the motor torque T s and the armature current I a are measured for a plurality of current phase angle command values β*. The current phase angle command value β* at which the motor torque is maximized is calculated, and the motor torque T s and the armature current I a at that time are measured.

[0077] The motor torque T s is measured using a measuring instrument (not shown). The armature current I a may be calculated from the d-axis current command value i Figure 3 * and the q-axis current command value i d * output from the coordinate conversion unit 52 in q* is used for calculation. In this way, the motor torque T is calculated for M different current phase angle command values ​​β*, ranging from 45 degrees to the current phase angle command value β* at which the motor torque is maximized. s and armature current I a Curve B1 is obtained by plotting the operating points corresponding to the M current phase angle command values ​​β* on the dq coordinate system and then drawing the curves passing through them. Other curves B2 to B8 can be drawn using the same method. Figure 8 In the diagram, the operating point drawn from curves B1 to B8 to the dashed line 81 is the operating point where the motor torque is maximized.

[0078] When 1600rpm is defined as speed number 1, the M motor torques T calculated for a speed of 1600rpm are... s For example, the motor torque T is stored in ascending order of the current phase angle command value β*, corresponding to the row of speed number 1 in the torque command value table 71. s11 To T s1M The calculation of M armature currents I at a speed of 1600 rpm. a For example, the armature current command value I is stored in ascending order of the current phase angle command value β*, corresponding to the row of speed number 1 in the current command value table 72. a11 * to I a1M * The M current phase angle command values ​​β* calculated for a speed of 1600 rpm are stored, for example, in ascending order of the current phase angle command values ​​β*, as the current phase angle command value β in the row corresponding to speed number 1 in the current phase angle command value table 73. 11 *to β 1M *

[0079] For each of the other speeds 2 to N, the torque T of the M motors n1 To T nM M armature current command values ​​I an1 * to I anM * and M current phase angle command values ​​β n1 *to β nM *Calculated in the same manner and stored in torque command value table 71, current command value table 72, and current phase angle command value table 73. The torque command value T is obtained based on the speed / command value table 70. s * and the armature current command value I corresponding to the rotational speed ω a * and the current phase angle command value β*, and based on the acquired armature current command value I a The method of controlling motor 18 using the obtained current phase angle command value β* is called "torque / speed control".

[0080] The operation of the current command value setting unit 42 will be described in detail below. Figure 9 is a flowchart showing an operation routine performed by the current command value setting unit 42. Figure 9 The routine shown is repeatedly executed at intervals of a predetermined operation period. In the following description, the latest rotational speed ω calculated by the rotational speed calculation unit 54 is referred to as "actual rotational speed ω". The current command value setting unit 42 calculates a first candidate armature current command value I acan1 *and a current phase angle command value β can1 *(step S1).

[0081] Specifically, first, the current command value setting unit 42 selects the table 61 or 62 of the rotational direction corresponding to the sign of the torque command value T s *from among the forward rotation table 61 and the reverse rotation table 62. Then, the current command value setting unit 42 acquires the armature current command value I s *and the current phase angle command value β* corresponding to the torque command value T a *based on the selected table 61 or 62, and stores the acquired command values as the first candidate armature current command value I acan1 *and the current phase angle command value β can1 *in the memory.

[0082] More specifically, the current command value setting unit 42 searches for a motor torque T s having the same magnitude as the torque command value T s *from among the plurality of motor torques T s *in the selected table 61 or 62. When a motor torque T s having the same magnitude as the torque command value T s *can be searched for, the current command value setting unit 42 reads the armature current command value I s *and the current phase angle command value β* corresponding to the motor torque T a from the table 61 or 62, and stores the read command values as the first candidate armature current command value I acan1 *and the current phase angle command value β can1 *in the memory.

[0083] On the other hand, when a motor torque T s having the same magnitude as the torque command value T s *cannot be searched for, the current command value setting unit 42 performs the following processing. The current command value setting unit 42 reads the armature current command value I s *and the current phase angle command value β* corresponding to the motor torque T s *closest to the torque command value Ts the motor torque T s (corresponding to the first motor torque T sL ) corresponding to the armature current command value I a *and the current phase angle command value β*.

[0084] The current command value setting unit 42 reads the armature current command value I s *and the current phase angle command value β* corresponding to the motor torque T s *that is greater than the torque command value T s *and closest to the torque command value T s (corresponding to the second motor torque T sH ) corresponding to the armature current command value I a *and the current phase angle command value β*. Then, the current command value setting unit 42 calculates the armature current command value I a *and the current phase angle command value β* corresponding to the torque command value T s *by linearly interpolating the armature current command values I a *and the current phase angle command values β* of the two sets read.

[0085] Specifically, the armature current command value I sL *and the current phase angle command value β* corresponding to the first motor torque T a are set to I aL *and β L *, and the armature current command value I sH *and the current phase angle command value β* corresponding to the second motor torque T a are set to I aH *and β H *. T sH -T sL = ΔT s , I aH *-I aL *= ΔI a , and β H *2-β L *= Δβ* are set.

[0086] The current command value setting unit 42 calculates the armature current command value I s *and the current phase angle command value β* corresponding to the torque command value T a *based on the expressions (5) and (6), and stores the calculated command values as the first candidate armature current command value I acan1 *and the current phase angle command value β can1 *in the memory.

[0087] I a *= (ΔIa * / T s )·(T s *-T sL )+I aL * …(5)

[0088] β*=(Δβ* / T s )·(T s *-T sL )+β L * …(6)

[0089] Then, the current command value setting unit 42 acquires the second candidate armature current command value I acan2 *and the current phase angle command value β can2 *(step S2) based on the speed / command value table 70.

[0090] Specifically, the current command value setting unit 42 acquires the speed number n closest to the actual rotation speed ω from the torque command value table 71 as the first speed number nl. Then, the current command value setting unit 42 searches for the motor torque T s having the same magnitude as the torque command value T s *from among the plurality of motor torques T s corresponding to the first speed number nl in the torque command value table 71. When the motor torque T s having the same magnitude as the torque command value T s *can be searched for, the current command value setting unit 42 acquires the torque number m of the motor torque T s closest to the torque command value T a *as the first torque number ml.

[0091] Then, the current command value setting unit 42 reads the armature current command value I acan2 *and the current phase angle command value β can2 *corresponding to the first speed number nl and the first torque number ml from the current command value table 72 and the current phase angle command value table 73, and stores the read command values as the second candidate armature current command value I s *and the current phase angle command value β s *in the memory. On the other hand, when the motor torque T s having the same magnitude as the torque command value T s *cannot be searched for, the current command value setting unit 42 performs the following processing. The current command value setting unit 42 acquires the motor torque T s closest to the torque command value T s *from among the plurality of motor torques T sLcorresponding to the first motor torque T a and the current phase angle command value β corresponding to the second motor torque T sL are stored in the memory. a

[0092] The current command value setting unit 42 acquires a plurality of motor torques T s in the torque command value table 71 corresponding to the first speed number n1 that is greater than the torque command value T s and closest to the torque command value T s *and the current phase angle command value β corresponding to the second motor torque T s (subsequently referred to as "second motor torque T sH corresponding to the first speed number n1 and the second torque number m2 as a second torque number m2. Then, the current command value setting unit 42 reads the armature current command value I a and the current phase angle command value β corresponding to the first speed number n1 and the second torque number m2 from the current command value table 72 and the current phase angle command value table 73, and stores the read command values as the armature current command value I sH and the current phase angle command value β corresponding to the second motor torque T a in the memory.

[0093] Then, the current command value setting unit 42 calculates the armature current command value I a and the current phase angle command value β corresponding to the torque command value T s and the actual rotational speed ω by interpolating the armature current command values I a and the current phase angle command values β of the two sets that are read. Specifically, the armature current command value I sL and the current phase angle command value β corresponding to the first motor torque T a are set to I aL and β L , and the armature current command value I sH and the current phase angle command value β corresponding to the second motor torque T a are set to I aH and β H . T sH -T sL = ΔT s , I aH *-I aL * = ΔI a ​*and β H *-β L *Δβ*.

[0094] The current command value setting unit 42 calculates the armature current command value I s *and the current phase angle command value β* corresponding to the torque command value T a *and the actual rotational speed ω based on the expressions (5) and (6), and stores the read command values as the first candidate armature current command value I acan2 *and the first candidate current phase angle command value β can2 *in the memory. Then, the current command value setting unit 42 determines whether the first candidate current phase angle command value β can1 *is equal to or greater than the second candidate current phase angle command value β can2 *(step S3). When β can1 *≥ β can2 *is satisfied (step S3: "Yes"), the current command value setting unit 42 sets the first candidate armature current command value I acan1 *and the first candidate current phase angle command value β can1 *as the armature current command value I a *and the current phase angle command value β* (step S4). Accordingly, the maximum torque / current control is executed. Then, the routine in this operation cycle ends.

[0095] When it is determined in step S3 that β can1 *< β can2 *is satisfied (step S3: "No"), the current command value setting unit 42 sets the second candidate armature current command value I acan2 *and the second candidate current phase angle command value β can2 *as the armature current command value I a *and the current phase angle command value β* (step S5). Accordingly, the torque / speed control is executed. Then, the routine in this operation cycle ends.

[0096] The reason why the first candidate is selected when β can1 *≥ β can2 *is satisfied and the second candidate is selected when β can1 *< β can2 *is satisfied will be described below. Figure 8 The curves B1 to B8 in FIG. 10 indicate the trajectories of the armature current vector in the torque / speed control. The curves B1 to B8 are when the maximum value is given as the armature current command value I aThe trajectory of the armature current vector for each rotational speed. Therefore, curves B1 to B8 constitute part of a voltage limiting oval. The voltage limiting oval uses the trajectory of the armature current vector to indicate the controllable range of the armature current vector at any input voltage (voltage between motor terminals) and any rotational speed. The voltage limiting oval decreases as the rotational speed of motor 18 increases.

[0097] Figure 8 Curve A in the diagram indicates the trajectory of the armature current vector during maximum torque / current control and the trajectory of the armature current vector when the armature current is minimized to output arbitrary torque from motor 18. When it is intended to output arbitrary torque from motor 18 and the operating point of torque / speed control is above or to the right of curve A, the operating point of maximum torque / current control is the most efficient point for outputting torque. For example, when the actual speed is 1600 rpm and the operating point of torque / speed control is above or to the right of the intersection of curve A and curve B1, the operating point of maximum torque / current control is the most efficient point for outputting torque. Therefore, in this case, it is preferable to control the motor by maximum torque / current control. Therefore, when β is satisfied... can1 *≥β can2 When *, the first candidate is set to the armature current command value I. a * and the current phase angle command value β*.

[0098] On the other hand, when the operating point of torque / speed control is to the left of curve A, the target torque cannot be output in maximum torque / current control. For example, when the actual speed is 1600 rpm and the operating point of torque / current control is to the left of the intersection of curve A and curve B1, the target torque cannot be output in maximum torque / current control. Therefore, in this case, torque / speed control is preferably used to control motor 18. Therefore, when β is satisfied... can1 *<β can2 When *, the second candidate is set to the armature current command value I. a * and the current phase angle command value β*.

[0099] That is, in the first embodiment, the armature current command value I a * and the current phase angle command value β* are set such that the armature current command value I is... a The current vector set by the * and current phase angle command value β* is included. Figure 8 The region is bounded by the current vector trajectory (curve A) in the maximum torque / current control and the q-axis in the dq coordinate system. Therefore, the maximum torque can be output, and the motor torque corresponding to the motor torque command value can be output in all speed ranges.

[0100] [2] Second Embodiment

[0101] In the first embodiment, the speed / command value table 70 is prepared based on the assumption that the motor terminal voltage is a predetermined reference voltage. When the motor terminal voltage decreases, the voltage limit ellipse decreases. Therefore, due to the change in the characteristics indicated by the curves B1 to B8 in FIG. 7, the details of the speed / command value table 70 in the first embodiment are not suitable for the characteristics when the motor terminal voltage decreases. Figure 8

[0102] Therefore, when the motor terminal voltage decreases, there is a problem that even when the torque command value is in the range in which the motor torque can be output in the torque / speed control according to the first embodiment, an area in which the motor torque cannot be output is generated. The reason is that when the motor terminal voltage decreases in the speed / command value table 70 according to the first embodiment, the command values corresponding to the motor torque that cannot be output as the armature current command value Ia* and the current phase angle command value β* are set, and thus the unintended armature current flows in the motor 18.

[0103] The purpose of the second embodiment is to achieve a motor control that can output the maximum torque, performs the torque control in all the rotational speed regions, and solves the above-described problem in the first embodiment. In the second embodiment, the method of preparing the speed / command value table 70 is different from that in the first embodiment. That is, the methods of preparing the torque command value table 71, the current command value table 72, and the current phase angle command value table 73 are different from those in the first embodiment. The second embodiment differs from the first embodiment in the operation of the current command value setting unit 42. The other points are the same as in the first embodiment.

[0104] The method of preparing the speed / command value table 70 will be described first with reference to Figure 10 Figure 10 A d-q coordinate system in which the d-axis current is on the horizontal axis and the q-axis current is on the vertical axis is shown. First, as shown in FIG. 8, a curve A indicating the trajectory of the armature current vector in the maximum torque / current control is plotted in the d-q coordinate system. The curve A can be plotted using the same method as in the first embodiment. Figure 10

[0105] Then, the operation point at the time of the motor torque maximization (hereinafter referred to as "maximum output point") is calculated at each of eight rotational speeds in a predetermined range (a range from 1600 rpm to 3000 rpm in this example) of the rotational speed that differ from each other by a predetermined value (200 rpm in this example), and the calculated operation points are plotted on the d-q coordinate system. The operation points plotted into the closed point-like curve 91 in Figure 10 the maximum operation point at the corresponding rotational speed and corresponds to the operation point at the time of the motor torque maximization.​​​Figure 8 The operation points plotted into the closed-point curve 81. These operation points can be calculated using the same method as the method of preparing the curves B1 to B8 described in the first embodiment described above.

[0106] Then, a predetermined point of the origin or near the origin of the d-q coordinate system is set as the convergence point V. In this embodiment, a predetermined point on the curve A near the origin of the d-q coordinate system is set as the convergence point V. The maximum output point at each rotational speed and the convergence point V are connected by a straight line. Thus, the straight lines D1 to D8 are obtained at 8 rotational speeds. The straight line D1 is a straight line corresponding to 1600 rpm, the straight line D8 is a straight line corresponding to 3000 rpm, and the rotation angle of the d-axis (current phase angle β) increases as the rotational speed increases.

[0107] Then, for each of the straight lines D1 to D8, M operation points including the maximum output point are set on the corresponding straight line. In this embodiment, the M operation points are set on each of the straight lines D1 to D8 so that two adjacent operation points are separated by the same length. The M operation points are a plurality of operation points (third operation points) including the maximum output point (first operation point) and a plurality of operation points (second operation points) set in a direction in which the operation point moves from the maximum output point as the terminal-to-terminal voltage of the motor 18 decreases.

[0108] Then, the d-axis current i d , the q-axis current i q , the armature current I a , and the current phase angle β corresponding to each of the set operation points are calculated. The armature current I a at a certain operation point is calculated from the d-axis current i d and the q-axis current i q at that operation point. Then, for each operation point, the armature current I a and the current phase angle β are provided to the current vector calculation unit 43 of the motor control circuit shown in FIG. 8 as the armature current command value I a * and the current phase angle command value β*. Figure 3 and the motor torque T s is measured. In this way, the motor torque T s , the armature current command value I a * and the current phase angle command value β* at the M operation points can be acquired for each of the straight lines D1 to D8.

[0109] For example, when 1600 rpm is defined as speed number 1, the motor torque T s at the M operation points on the straight line D1 is plotted against the armature current command value I a* corresponding to the speed number 1 in the torque command value table 71 is stored as the motor torque T s11 s1M (see Figure 7A ) at the M operating points on the straight line D1 a * corresponding to the speed number 1 in the current command value table 72 is stored as the armature current command value I a * corresponding to the speed number 1 in the current command value table 72 is stored as the armature current command value I a11 * to I a1M (see Figure 7B ) at the M operating points on the straight line D1 a * corresponding to the speed number 1 in the current phase angle command value table 73 is stored as the current phase angle command value β 11 * to β 1M *.

[0110] The M motor torques T n1 to T nM , the M armature current command values I an1 * to I anM * and the M current phase angle command values β n1 * to β nM * for each of the other speed numbers 2 to N are calculated in the same manner and stored in the torque command value table 71, the current command value table 72 and the current phase angle command value table 73. The speed / command value table 70 according to the second embodiment is an example of the "third table" in the claims.

[0111] The operation of the current command value setting unit 42 will be described in detail below. Figure 11 is a flowchart showing an operation routine performed by the current command value setting unit 42. Figure 11 The routine shown is repeatedly executed at intervals of a predetermined operation period. The current command value setting unit 42 determines whether the actual rotational speed ω is equal to or lower than a predetermined rotational speed ω th (Step S11). The predetermined rotational speed ω th is set to a rotational speed in the vicinity of a boundary point between a predetermined low rotational speed region and a predetermined high rotational speed region. The predetermined low rotational speed region can be a constant torque region in which the torque in the speed-torque characteristic of the motor 18 is almost constant. In this case, the predetermined high rotational speed region is a constant output region in which the rotational speed is higher than that in the constant torque region.

[0112] When the actual rotational speed ω is equal to or lower than the predetermined rotational speed ω th ​When the actual rotation speed ω is higher than the predetermined rotation speed ω (step Sll: "Yes"), the current command value setting unit 42A sets the armature current command value Ia* and the current phase angle command value β* corresponding to the torque command value Ts* using the command value / maximum torque table 60 (step S12: "Yes"). The method of calculating the armature current command value Ia* and the current phase angle command value β* using the command value / maximum torque table 60 is the same as described in the first embodiment. Then, the routine in this operation cycle ends.

[0113] When it is determined in step Sll that the actual rotation speed ω is lower than the predetermined rotation speed ω th (step Sll: "No"), the current command value setting unit 42 sets the armature current command value Ia* and the current phase angle command value β* corresponding to the torque command value Ts* and the actual rotation speed ω using the speed / command value table 70 (step S13: "Yes"). The method of calculating the armature current command value Ia* and the current phase angle command value β* using the speed / command value table 70 is the same as described in the first embodiment. Then, the routine in this operation cycle ends.

[0114] In the second embodiment, the armature current command value I a * and the current phase angle command value β* are set so that the current vector set by the d-axis current command value i d * and the q-axis current command value i q * is included in the region surrounded by the current vector locus in the maximum torque / current control and the q-axis in the d-q coordinate system. Therefore, the maximum torque can be output and the motor torque corresponding to the motor torque command value can be output in all rotation speed regions.

[0115] In the second embodiment, a plurality of operation points are set in the direction in which the operation point moves due to the reduction of the motor terminal-to-terminal voltage, and the armature current, the current phase angle, and the motor torque corresponding to each operation point are set as the table values of the speed / command value table 70. Therefore, even when the motor terminal-to-terminal voltage is reduced, the motor torque can be output in the case where the torque command value is in the range in which the motor torque can be output.

[0116] That is, in the second embodiment, when the motor terminal-to-terminal voltage is reduced and the torque command value is in the range in which the motor torque can be output, the motor torque corresponding to the torque command value can be output. In other words, in the second embodiment, even when the motor terminal-to-terminal voltage is reduced, the region in which the motor torque corresponding to the torque command value can be output is wider than in the first embodiment. Therefore, the problem in the first embodiment can be solved.

[0117] While the first and second embodiments of the application have been described above, the application can be implemented in other forms. In the first and second embodiments, the microcomputer 31 includes the voltage limiting unit 48, but it can not include the voltage limiting unit 48. In the first and second embodiments, the synchronous reluctance motor which can rotate in two directions including the forward rotation direction and the reverse rotation direction has been exemplified, but the application can also be applied to an electric synchronous reluctance motor which is rotationally driven in only one direction.

[0118] In the first and second embodiments, the motor 18 is a synchronous reluctance motor, but the motor 18 can be a motor other than the synchronous reluctance motor (for example, a switched reluctance motor or an IPM motor) as long as it is a motor which rotates a rotor using reluctance torque. In the first and second embodiments, the application has been applied to the control device of the motor for the electric power steering system. However, the application can also be applied to a motor control device other than the control device of the motor for the electric power steering system as long as it is a control device of a motor which is controlled based on a torque command value.

[0119] The application can be variously changed in design without departing from the scope of the application described in the appended claims.

Claims

1. A motor control device (12) that controls a motor (18) that uses reluctance torque, the motor control device (12) characterized by comprising: a first setting unit configured to set a motor torque command value that is a command value of a motor torque to be generated from the motor (18); a rotational speed detection unit configured to detect a rotational speed of the motor (18); a second setting unit configured to set an armature current command value and a current phase angle command value based on the rotational speed and the motor torque command value; a current vector setting unit configured to set a d-axis current command value and a q-axis current command value based on the armature current command value and the current phase angle command value; and a drive unit (32) configured to drive the motor (18) based on the d-axis current command value and the q-axis current command value, wherein the second setting unit is configured to set the armature current command value and the current phase angle command value such that an armature current vector set based on the d-axis current command value and the q-axis current command value is included in an area enclosed by a d-q coordinate system in a vertical axis that is a d-axis current and a horizontal axis that is a q-axis current and an armature current vector locus in maximum torque / current control, the motor control device (12) further comprising: a first table in which motor torques generated from the motor (18) are stored in association with combinations of armature current command values and current phase angle command values, wherein the motor torque is maximized at the current phase angle command value at a corresponding armature current command value; and a second table in which, for each rotational speed of the motor (18), armature current command values, current phase angle command values, and motor torques at a plurality of operating points on a voltage limit ellipse are stored in association, wherein the second setting unit is configured to calculate a first candidate of an armature current command value and a current phase angle command value based on the motor torque command value and the first table, calculate a second candidate of an armature current command value and a current phase angle command value based on the rotational speed, the motor torque command value, and the second table, set the first candidate of the armature current command value and the current phase angle command value as the command values in a case where the first candidate of the current phase angle command value is equal to or greater than the second candidate of the current phase angle command value, and set the second candidate of the armature current command value and the current phase angle command value as the command values in a case where the first candidate of the current phase angle command value is less than the second candidate of the current phase angle command value. The plurality of operating points on the voltage limit ellipse corresponding to the rotational speed of the motor (18) include an operating point at which the motor torque is maximized at the rotational speed.

2. The electric machine control device (12) according to claim 1, characterized in that 3. A motor control device (12) that controls a motor (18) that uses reluctance torque, the motor control device (12) characterized by comprising: ​ a first setting unit configured to set a motor torque command value that is a command value of a motor torque to be generated from the motor (18); a rotational speed detection unit configured to detect a rotational speed of the motor (18); a second setting unit configured to set an armature current command value and a current phase angle command value based on the rotational speed and the motor torque command value; a current vector setting unit configured to set a d-axis current command value and a q-axis current command value based on the armature current command value and the current phase angle command value; and a drive unit (32) configured to drive the motor (18) based on the d-axis current command value and the q-axis current command value, wherein the second setting unit is configured to set the armature current command value and the current phase angle command value such that an armature current vector set based on the d-axis current command value and the q-axis current command value is included in an area enclosed by a d-q coordinate system in which a d-axis current is on a horizontal axis and a q-axis current is on a vertical axis, and a d-axis current vector locus in maximum torque / current control, the motor control device (12) further includes: a first table in which motor torques generated from the motor (18) are stored in association with combinations of armature current command values and current phase angle command values, in which the motor torque is maximized at the current phase angle command value at a corresponding armature current command value; and a third table in which, for each rotational speed of the motor (18), armature current command values, current phase angle command values, and motor torques at a plurality of third operation points are stored in association, the third operation points including a first operation point at which the motor torque is maximized at a corresponding rotational speed and a plurality of second operation points set in a direction in which an operation point moves from the first operation point when a terminal voltage of the motor (18) decreases, wherein the second setting unit is configured to set the armature current command value and the current phase angle command value based on the motor torque command value and the first table in a case where the rotational speed is equal to or lower than a predetermined value, and set the armature current command value and the current phase angle command value based on the rotational speed, the motor torque command value, and the third table in a case where the rotational speed is higher than the predetermined value. In the d-q coordinate system, for each rotational speed, the plurality of third operation points are set on a straight line connecting a convergence point and the first operation point at the corresponding rotational speed, the convergence point being set as an origin of the d-q coordinate system or a predetermined point close to the origin.

4. The electric machine control device (12) according to claim 3, characterized in that ​

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