Control device of an electric rotary machine

Abstract

Control device (60) of an electric rotary machine (20) which controls an electric rotary machine (20), wherein the control device (60) of the electric rotary machine (20) comprises: a torque command value (Tr*) acquisition section (S14) that acquires a torque command value (Tr*) for the electric rotary machine (20), and a setting part (S16) which sets a negative limit value (Idm) which limits a current command value (Id*) of the d-axis of the electric rotary machine (20), the current command value (Id*) of the d-axis being calculated in accordance with the torque command value (Tr*), where: the setting part (S16) sets the limit value (Idm) which has a larger absolute value in a case where the torque command value (Tr*) is large compared to a case where the torque command value (Tr*) is small, and in a case where the torque command value (Tr*) is equal to or less than a predetermined reference command value (Ttg), the setting part (S16) sets the negative limit value (Idm) of the current command value (Id*) of the d-axis to (i) to reduce it linearly from a negative first reference value (Ik1) to a negative second reference value (Ik2) in a first range (Wa1) in which the q-axis current (Iqr) varies from zero to a first q-axis current (Iqr1), (ii) to maintain it at the second reference value (Ik2) in a second range (Wa2) in which the q-axis current (Iqr) varies from the first q-axis current (Iqr1) to a second q-axis current (Iqr2), and (iii) to increase it linearly from the second reference value (Ik2) to zero in a third range (Wa3) in which the q-axis current (Iqr) varies from the second q-axis current (Iqr2) to a rated current (Ist) of the electric rotary machine (20).

Description

[0001] The present disclosure relates to a control device of an electric rotary machine.

[0002] As disclosed in JP 3 686 987 B2, a control device is known that is configured to limit a d-axis current command value in accordance with a q-axis current command value of a rotating electric machine. JP 3 686 987 B2 discloses setting a predetermined negative limit value of a voltage command value of the rotating electric machine to achieve a substantially constant output at an upper limit usage voltage of the rotating electric machine, and limiting the d-axis current command value to more than the limit value.

[0003] If the limit value is set to be small, that is, if the negative limit value has an absolute value set to be large, the d-axis current will have a negative value and a large absolute value, possibly causing overheating of the rotating electric machine. The rotating electric machine is configured to generate torque that decreases with increasing speed. The d-axis current must have a negative value and a large absolute value to prevent the reduction of the torque that can be generated by the rotating electric machine. If the limit value is set to be large, that is, if the negative limit value has an absolute value set to be small, the torque reduction of the rotating electric machine must not be inhibited in the above case.

[0004] Furthermore, EP 3 290 296 A1 discloses a main control device comprising: a d-axis current limiter that calculates a d-axis current limiting value with priority based on a dq-converted current limiting value, and calculates a limited d-axis current command value by limiting the d-axis current command value to the d-axis current limiting value or less; a q-axis current limiter configured to calculate a q-axis current limiting value based on the dq-converted current limiting value and the limited d-axis current command value, and calculates a limited q-axis current command value by limiting the q-axis current command value to the q-axis current limiting value or less; and an inverter controller configured to control the motor current based on the limited d-axis current command value and the limited q-axis current command value.

[0005] DE 102 06 955 B4 discloses a steering control device capable of mitigating a reduction in the output torque of a motor during a high-speed steering operation. The steering control device includes a motor, a motor current command value generation section for generating a current command value for the motor, and a motor current detection section for detecting a current flowing through the motor. The motor is driven to rotate based at least on the current flowing through the motor and the current command value. The motor current command value generation section includes a correction section for correcting the current command value for controlling the magnetic field in a field magnet of the motor, and the correction section is operable to correct the current command value for controlling the magnetic field of the field magnet of the motor when the steering speed is fast.

[0006] JP 2014-131392 A discloses an inverter control device that can increase the power of a permanent magnet motor up to an actual limit while preventing the occurrence of irreversible demagnetization. To this end, a vector control section is configured to control a permanent magnet motor with permanent magnets in a rotor, and a temperature estimation section estimates a temperature of the permanent magnets based on an input temperature around the rotor, a heat flux of the permanent magnets, heat transfer resistances of the rotor, and a heat transfer medium present around the rotor, all of which have been stored in advance.A current command setting section sets the desired D-axis and Q-axis current values ​​from a desired torque value, and a voltage command setting section sets voltage commands for external output from the current flows to the stator windings and the desired D-axis and Q-axis current values. There is also a section for setting an upper limit for the D-axis current and a section for limiting the desired D-axis current value to the upper limit.

[0007] It is an object of the present disclosure to provide a control device configured to appropriately limit a current setpoint of the d-axis of an electric rotary machine. This object is achieved by the independent claims. Advantageous further developments are disclosed in the dependent claims.

[0008] According to one aspect of the present disclosure, a rotary electric machine control device is provided that controls a rotary electric machine. The rotary electric machine control device includes: a torque command acquisition section that acquires a torque command for the rotary electric machine; and a setting part that sets a negative limit value that limits a d-axis current command value of the rotary electric machine, the d-axis current command value being calculated in accordance with the torque command value. The setting part sets the limit value, which has a larger absolute value, in a case where the torque command value is large compared to a case where the torque command value is small.

[0009] According to another aspect of the present disclosure, a system for an electric rotary machine is provided. The system includes: an electric power steering system that outputs torque according to an operation of a steering wheel, an electric rotary machine included in the electric power steering system, and the electric rotary machine controller. The torque command increases as the torque of the electric rotary machine increases.

[0010] The rotating electric machine experiences an increase in speed and a decrease in torque when the torque command is large. The absolute value of the negative limit value must be set to be large to inhibit a drop in torque. In the other case, where the torque command value is small, the absolute value of the negative limit value must be set to be small to inhibit overheating of the rotating electric machine. The torque command value and the limit value are thus correlated with each other. The control device for the rotating electric machine according to the present disclosure sets the absolute value of the negative limit value to be larger when the torque command value is large compared to when the torque command value is small.It may be possible to prevent the torque of the rotating electric machine from decreasing when the torque command value is large. It may be possible to inhibit the overheating of the rotating electric machine when the torque command value is small. Accordingly, it may be possible to appropriately limit the d-axis current command value of the rotating electric machine.

[0011] The above and other objects, features and advantages of the present disclosure will become apparent from the following detailed description with reference to the accompanying drawings. Fig. 1 is a diagram showing an entire configuration of an electric rotating machine system in a vehicle. Fig. 2 is a diagram showing a configuration of an electrification circuit and an electric rotary machine. Fig. 3 is a diagram showing a circuit configuration of an EPS-ECU according to a first embodiment. Fig. 4 is a graph showing a relationship between a steering torque and a base assist torque. Fig. 5 is a flowchart of setting processing according to the first embodiment. Fig. 6 is a graph indicating a relationship between a first threshold value and a second threshold value according to the first embodiment. Fig. 7 is a graph showing a relationship between a first threshold value and a second threshold value according to the second embodiment. Fig. 8 is a flowchart of setting processing according to the second embodiment. Fig. 9 is a diagram showing a circuit configuration of an EPS-ECU according to another embodiment. (First embodiment)

[0012] A control system for a rotating electric machine of a vehicle 100 including a rotating electric machine control device according to a first embodiment will be described below with reference to the drawings. The controller according to the present embodiment configures the rotating electric machine control system of an electric power steering (EPS) device 10 that assists steering by a driver. A rotating electric machine may be referred to as a dynamoelectric machine. A rotating electric machine control device may also be referred to as a rotating electric machine control device. A control device may also be referred to as a control device.

[0013] Fig. 1 shows the vehicle 100, which includes a steering wheel 90, a steering shaft 91, a pinion gear 92, a rack shaft 93, and the EPS device 10. The steering shaft 91 is connected to the steering wheel 90. The steering shaft 91 has a distal end provided with the pinion gear 92. The pinion gear 92 engages the rack shaft 93. The rack shaft 93 has ends each provided with a wheel 95 rotatably coupled via a tie rod or the like. The steering shaft 91 is rotated when the driver turns the steering wheel 90. The pinion gear 92 converts the rotational movement of the steering shaft 91 into a linear movement of the rack shaft 93. The wheels 95 are steered to have a steering angle corresponding to the displacement of the rack shaft 93.

[0014] The EPS device 10 includes a torque sensor 94, a reduction gear 96, a rotary electric machine 20, and an electrification circuit 30. The torque sensor 94 is provided on the steering shaft 91 and detects the steering torque Trq output from the steering shaft 91. The rotary electric machine 20 generates an auxiliary torque according to the thus detected steering torque Trq and a steering direction of the steering wheel 90. The electrification circuit 30 controls the drive of the rotary electric machine 20. The reduction gear 96 is configured to decelerate the rotation of a rotary shaft included in a rotor of the rotary electric machine 20 and to transmit the auxiliary torque to the steering shaft 91.

[0015] The electric rotary machine 20 and the electrification circuit 30 are connected to Fig. 2 described.

[0016] The rotating electric machine 20 may be of a permanent magnet field type or a coil field type. The rotating electric machine 20 includes a stator having a first coil group M1 and a second coil group M2. The first coil group M1 includes a first U-phase coil U1, a first V-phase coil V1, and a first W-phase coil W1 connected in a star configuration. The second coil group M2 includes a second U-phase coil U2, a second V-phase coil V2, and a second W-phase coil W2 connected in a star configuration. The first phase coils, U-, V-, and W-phase coils U1, V1, and W1, have first ends connected to each other at a neutral point. The first phase coils, U-, V-, and W-phase coils U1, V1, and W1, are shifted from each other by 120 degrees with respect to an electrical angle θe. The second phase coils, U, V and W phase coils U2, V2 and W2, have first ends connected to each other at a neutral point.The second phase coils, U, V and W phase coils U2, V2 and W2, are shifted from each other by 120 degrees with respect to the electrical angle θe.

[0017] The electrification circuit 30 includes a first inverter 40 and a second inverter 50, each functioning as a power converter. In the first inverter 40, a node between the first U-phase upper and lower branch switches SU1p and SU1n is connected to a second end of the first U-phase coil U1. A node between the first V-phase upper and lower branch switches SV1p and SV1n is connected to a second end of the first V-phase coil V1. A node between the first W-phase upper and lower branch switches SW1p and SW1n is connected to a second end of the first W-phase coil W1. In the second inverter 50, a node between the second U-phase upper and lower branch switches SU2p and SU2n is connected to a second end of the second U-phase coil U2. A node between the second V-phase upper and lower branch switches SV2p and SV2n is connected to a second end of the second V-phase coil V2.A node between the second W-phase upper and lower branch switches SW2p and SW2n is connected to a second end of the second W-phase coil W2.

[0018] Each of the switches SU1p to SW2n only needs to be configured as a voltage-controlled semiconductor switching element, such as an IGBT (insulated-gate bipolar transistor) or a MOSFET (metal-oxide-semiconductor field-effect transistor). Each of the switches SU1p to SW2n is connected in antiparallel with a diode.

[0019] The electrification circuit 30 includes a first high-voltage path Lp1, a first low-voltage path Ln1, a second high-voltage path Lp2, a second low-voltage path Ln2, and a capacitor 31. The first U-, V-, and W-phase upper-branch switches SU1p, SV1p, and SW1p each have a high-potential terminal connected to a positive electrode terminal of a battery 97 as a DC power source via the first high-potential path Lp1. The first U-, V-, and W-phase lower-branch switches SU1n, SV1n, and SW1n each have a low-potential terminal connected to a negative electrode terminal of the battery 97 via the first low-potential path Ln1. The negative electrode terminal of the battery 97 is connected to ground.The second U-, V-, and W-phase upper branch switches SU2p, SV2p, and SW2p each have a high-potential terminal connected to the positive electrode terminal of the battery 97 via the second high-potential path Lp2 and the first high-potential path Lp1. The second U-, V-, and W-phase lower branch switches SU2n, SV2n, and SW2n each have a low-potential terminal connected to the negative electrode terminal of the battery 97 via the second low-potential path Ln2 and the first low-potential path Ln1.

[0020] The electrification circuit 30 includes a current sensor. In the first inverter 40, the low-potential terminals of the first U-, V-, and W-phase sub-branch switches SU1n, SV1n, and SW1n and the first low-potential path Ln1 are connected by electrical paths provided with the first U-, V-, and W-phase current sensors DU1, DV1, and DW1. The first U-, V-, and W-phase current sensors DU1, DV1, and DW1 are configured to detect the current flowing through the electrical paths and output the detected current as the first U-, V-, and W-phase currents Iur1, Ivr1, and Iwr1, respectively.

[0021] In the second inverter 50, the low-potential terminals of the second U-, V-, and W-phase sub-branch switches SU2n, SV2n, and SW2n, as well as the second low-potential path Ln2, are connected by electrical paths provided with second U-, V-, and W-phase current sensors DU2, DV2, and DW2. The second U-, V-, and W-phase current sensors DU2, DV2, and DW2 are configured to detect the current flowing through the electrical paths and output the detected current as the second U-, V-, and W-phase currents Iur2, Ivr2, and Iwr2, respectively.

[0022] The electrification circuit 30 includes a voltage sensor 32, an angle sensor 33, and a vehicle speed sensor 34. The voltage sensor 32 detects a terminal voltage of the capacitor 31 as a source voltage VDC. The angle sensor 33 outputs an angle signal corresponding to the electrical angle θe of the rotating electric machine 20. The angle sensor 33 may include a magnet serving as a magnetism generator provided on a rotor of the rotating electric machine 20 and a magnetism detection element provided adjacent to the magnet. The vehicle speed sensor 34 detects a vehicle speed Vm of the vehicle 100. The voltage sensor 32, the angle sensor 33, the vehicle speed sensor 34, and the torque sensor 94 each output a signal received by an EPS ECU 60 included in the electrification circuit 30.

[0023] The EPS-ECU 60 is mainly configured by a microcomputer and operates the switches of the first and second inverters 40 and 50 to control the torque of the rotating electric machine 20 to achieve a torque command Tr*. The torque command Tr* is set, for example, in accordance with the steering torque Trq detected by the torque sensor 94. The EPS-ECU 60 calculates the electrical angle θe of the rotating electric machine 20 according to the signal output from the angle sensor 33. The EPS-ECU 60 has a function that can be performed by software recorded in a non-volatile tangible storage medium and a computer configured to execute the software, hardware, or a combination thereof. The EPS-ECU 60 corresponds to a "control device" according to the present embodiment.

[0024] The electric rotary machine 20 is in relation to Fig. 3 with regard to the torque control processing executed by the EPS-ECU 60.

[0025] A two-phase converter 73 converts the U-, V-, and W-phase currents lur1, Ivr1, and Iwr1 in a three-phase fixed coordinate system of the rotating electric machine 20 into the first d- and q-axis currents Idr1 and Iqr1 in a two-phase rotating coordinate system (dq coordinate system) in accordance with the phase current lur1, Ivr1, and Iwr1 for the first coil group M1 and the electrical angle θe detected by the current sensors. The two-phase converter 73 also converts the U-, V-, and W-phase currents lur2, Ivr2, and Iwr2 into the second d- and q-axis currents Idr2 and Iqr2 in the dq coordinate system in accordance with the phase current lur2, Ivr2, and Iwr2 detected by the current sensors for the second coil group M2 and the electrical angle θe.

[0026] A second converter 74 converts the first and second d-axis currents Idr1 and Idr2 into d-axis current Idr and differential d-axis current Idr#, and outputs the obtained current. The d-axis current Idr is obtained by halving a value obtained by adding the first d-axis current Idr1 and the second d-axis current Idr2, and the differential d-axis current Idr# is obtained by halving a value obtained by subtracting the second d-axis current Idr2 from the first d-axis current Idr1. The second converter 74 also converts the first and second q-axis currents Iqr1 and Iqr2 into q-axis current Iqr and differential q-axis current Iqr#, and outputs the obtained current.

[0027] A torque setting section 61 sets the torque command value Tr* in accordance with the steering torque Trq detected by the torque sensor 94. As shown in Fig. As shown in Figure 4, the torque setting section 61 stores a conversion table indicating the relationship between the steering torque Trq and the basic assist torque Trk. The conversion table has a relationship that the basic assist torque Trk increases with increasing steering torque Trq. The torque setting section 61 acquires the basic assist torque Trk according to the steering torque Trq with reference to the conversion table and performs stabilization control such as differentiation control on the thus obtained basic assist torque Trk to set the torque command Tr*. Examples of stabilization control include differentiation control for ensuring the stability of the torque command Tr*.

[0028] A torque command limiter 62 limits the torque command Tr* when the torque command Tr* set by the torque setting section 61 is too high. Specifically, the torque command limiter 62 limits the torque command Tr* according to a predetermined reference power in an exemplary case where the torque of the rotating electric machine 20 is controlled as the torque command Tr* and the battery 97 outputs a higher power than the reference power. Examples of the reference power include the normal rated power of the battery 97. The torque command limiter 62 specifically limits the torque command Tr* depending on the temperature of the rotating electric machine 20, the first inverter 40, and the second inverter 50 in an exemplary case where these devices are overheated.

[0029] A current command setting section 63 sets the d- and q-axis current command values ​​Id* and Iq* so that the sum of the torques output by the first coil group M1 and the second coil group M2 is equal to the torque command value Tr* in accordance with the torque command value Tr* output by the torque command limiter 62. The current command setting section 63 sets the d- and q-axis current command values ​​Id* and Iq* with reference to the d- and q-axis torque maps MPd and MPp stored in advance in a memory 70 included in the EPS-ECU 60. The d- and q-axis torque maps MPd and MPp provide map information including the d- and q-axis current command values ​​Id* and Iq* prescribed in conjunction with the torque command value Tr*. Examples of memory 70 include a non-volatile substantive storage medium other than ROM (e.g.,a non-volatile memory that is different from ROM).

[0030] A d-axis current setpoint limiter 65 limits the d-axis current setpoint Id*, which is set by the d-axis current setpoint setting section 63, to a predetermined negative limit value Idm when the d-axis current setpoint Id* is smaller than the limit value Idm, that is, when the negative d-axis current setpoint Id* has an absolute value greater than an absolute value of the limit value Idm. Thus, the absolute value of the d-axis current setpoint Id* may become too large to prevent overheating of the rotary electric machine 20, the first inverter 40, and the second inverter 50.

[0031] An FB controller 66 calculates the d- and q-axis voltage command values ​​Vd* and Vq* as control inputs for adjusting the d- and q-axis currents Idr and Iqr output from the second converter 74 to the d- and q-axis current command values ​​Id* and Iq*. Specifically, the FB controller 66 calculates d- and q-axis current deviations ΔId and ΔIq as values ​​obtained by subtracting the d- and q-axis currents Idr and Iqr from the d- and q-axis current command values ​​Id* and Iq*. The FB controller 66 calculates the d- and q-axis voltage command values ​​Vd* and Vq* as control inputs for controlling the calculated d- and q-axis current deviations ΔId and ΔIq to zero. The FB controller 66 further calculates the d- and q-axis differential voltage command values ​​Vd#* and Vq#* as control inputs for controlling the d- and q-axis differential currents Idr# and Iqr# output from the second converter 74 to zero.Examples of the control performed by the FB controller 66 include proportional integrated control.

[0032] A first converter 67 converts the d-axis voltage command value Vd* and the d-axis differential voltage command value Vd#* into a first d-axis voltage command value Vd1* for the first coil group M1 and a second voltage command value Vd2* for the second coil group M2. The first and second d-axis voltage command values ​​Vd1* and Vd2* are obtained, for example, by halving a value obtained by adding the d-axis voltage command value Vd* and the d-axis differential voltage command value Vd#*. The first converter 67 also converts the q-axis voltage command Vq* and the q-axis differential voltage command Vq#* into a first q-axis voltage command Vq1* for the first coil group M1 and a second q-axis voltage command Vq2* of the second coil group M2.

[0033] A three-phase converter 68 converts the first voltage command values ​​Vd1* and Vq1* of the d- and q-axes in a two-phase fixed coordinate system of the rotary electric machine 20 into the first U-, V-, and W-phase voltage command values ​​Vu1, Vv1, and Vw1 of the three-phase fixed coordinate system in accordance with the first voltage command values ​​Vd1* and Vq1* of the first d- and q-axes output from the first converter 67 and the electrical angle θe. The three-phase converter 68 also converts the second voltage command values ​​Vd2* and Vq2* of the d- and q-axes in the two-phase fixed coordinate system of the electric rotary machine 20 into the second voltage command values ​​Vu2, Vv2 and Vw2 of the U-, V- and W-phases in the three-phase fixed coordinate system according to the second d- and q-axis voltage command values ​​Vd2* and Vq2* output from the first converter 67 and the electrical angle θe.According to the present embodiment, the first voltage command values ​​Vu1, Vv1 and Vw1 of the U, V and W phases serve as sinusoidal signals with a phase shift of 120 degrees with respect to the electrical angle θe, and the second voltage command values ​​Vu2, Vv2 and Vw2 of the U, V and W phases serve as sinusoidal signals with phase shifts of 120 degrees with respect to the electrical angle θe.

[0034] A first modulator 71 generates drive signals that cause the switches SU1p to SW1n of the first inverter 40 to be turned on or off through sinusoidal PWM control according to a carrier signal such as a triangular wave signal, the first voltage commands Vu1, Vv1, and Vw1 of the U, V, and W phases output from the three-phase converter 68, and the power supply voltage VDC. The first modulator 71 generates the drive signals, causing the switches SU1p to SW1n of the first inverter 40 to control the d-axis current Idr to the d-axis current command Id* output from the d-axis current command limiter 65. The sinusoidal PWM control specifically includes generating the drive signals according to the comparison in magnitude between the values ​​obtained by dividing the first voltage command values ​​Vu1, Vv1 and Vw1 of the U, V and W phases by “VDC / 2” and the carrier signal.A second modulator 72 also generates drive signals, whereby the switches SU2p to SW2n of the second inverter 50 are turned on or off via the sinusoidal PWM control according to the carrier signal in accordance with the second U-, V- and W-phase voltage command values ​​Vu2, Vv2 and Vw2 output from the three-phase converter 68 and the source voltage VDC.

[0035] A d-axis current command value setting section 81 sets the d-axis current command value id* so that a voltage vector determined according to the first d- and q-axis voltage command values ​​Vd1* and Vq1* output from the first converter 67 has a magnitude that does not exceed a maximum voltage value Vmax. The d-axis current command value setting section 81 also sets the negative d-axis current command value Id* so that a voltage vector determined according to the second d- and q-axis voltage command values ​​Vd2* and Vq2* output from the first converter 67 has a magnitude that does not exceed the maximum voltage value Vmax. The maximum voltage value Vmax has the maximum voltage value that can be output from the first and second inverters 40 and 50 to the first and second coil groups M1 and M2.

[0036] Specifically, the d-axis current command value setting section 81 calculates a saturation factor Ran obtained by dividing an nth q-axis voltage command value Vqn* by a square root Hen of a value obtained by subtracting a square of an nth d-axis voltage command value Vdn* (n = 1, 2) from a square of the maximum voltage value Vmax. The square root Hen and the saturation factor Ran are expressed by Equations 1 and 2, respectively. Hen=(Vmax2−Vdn*2) Ran=Vqn* / Hen=Vqn* / (Vmax2−Vdn*2)

[0037] The d-axis current setpoint setting section 81 sets the negative d-axis current setpoint Id* in accordance with a difference between the saturation factor Ran and a predetermined target saturation factor Rtgn so that the saturation factor Ran reaches the target saturation factor Rtgn. The predetermined target saturation factor Rtgn has a predetermined value, such as a value of 0.8 to 0.9.

[0038] Specifically, the d-axis current command setting section 81 sets the negative d-axis current command Id* as the control input for controlling the saturation factor Ran to the target saturation factor Rtgn, so that the absolute value of the d-axis current command Id* increases when the saturation factor Ran is smaller than the target saturation factor Rtgn. The d-axis current command setting section 81 sets the d-axis current command so that the absolute value of the d-axis current command Id* decreases when the saturation factor Ran is larger than the target saturation factor Rtgn. The d-axis current command Id* set by the d-axis current command setting section 81 is hereinafter referred to as the second d-axis current command Id*2.

[0039] A limit value setting section 82 sets the negative limit value Idm in accordance with the torque command Tr* output from the d-axis current command setting section 81. Specifically, the limit value setting section 82 selects one of a plurality of negative limit values ​​Idm assigned to the q-axis current Iqr output from the second converter 74 in accordance with the torque command Tr*. The limit value setting section 82 sets, as the limit value Idm, a smaller absolute value than the selected limit value Idm and the negative second d-axis current command Id*2 output from the d-axis current command setting section 81, and sends the thus set limit value Idm to the d-axis current command limiter 65.

[0040] When the driver quickly turns the steering wheel 90, the rotating electric machine 20 has an increased electric angular velocity ω as the torque command Tr* increases. The rotating electric machine 20 has an induced voltage proportional to the electric angular velocity ω generated on the q-axis around which the torque of the rotating electric machine 20 is generated. Thus, the q-axis current Iqr decreases with increasing electric angular velocity ω to reduce the maximum value of the torque that can be generated by the rotating electric machine 20. In a state where the maximum value of the torque that can be generated by the rotating electric machine 20 is smaller than the torque command Tr* (hereinafter referred to as a voltage saturated state), the rotating electric machine 20 fails to output torque beyond the torque command Tr*.

[0041] In an exemplary case where the first coil group M1 has a non-aligning pole structure including a permanent magnet, the q-axis voltage Vdr is expressed by Equation 3 containing the electrical angular velocity ω. As expressed in Equation 3, at the q-axis voltage Vdr, the induced voltage contained in a second element on the right increases according to the electrical angular velocity ω, while the q-axis current Iqr contained in a first element on the right decreases. Equation 3 includes R indicating a resistance value of the first coil group M1, ϕ indicating an induced voltage constant of the rotating electric machine 20, and Ld indicating the d-axis inductance of the rotating electric machine 20. Vdr1=R×Iqr+ω×(ϕ+Ld×Idr)

[0042] Field weakening control is known as a technique for reducing the induced voltage according to the electrical angular velocity ω in the voltage-saturated state. Field weakening control can cause the d-axis current Idr to have a predetermined negative value to achieve a decrease in the induced voltage.

[0043] The d-axis current setpoint limiter 65 limits the d-axis current setpoint Id* to control the d-axis current Idr to be equal to or greater than the negative limit value Idm. In a case where the absolute value of the limit value Idm is set to be small, the negative d-axis current Idr has an absolute value that cannot be sufficiently increased, and the induced voltage cannot be reduced. In another case, where the absolute value of the limit value Idm is set to be large, the absolute value of the negative d-axis current Idr increases, and the rotary electric machine 20, the first inverter 40, and the second inverter 50 overheat.

[0044] In view of this, the present embodiment includes executing the setting processing of setting the absolute value of the negative limit value Idm to be larger when the torque command Tr* is large, compared to a case where the torque command Tr* is small. Thus, the induced voltage can be preferentially reduced when the torque command Tr* is large, and overheating of the rotating electric machine 20, the first inverter 40, and the second inverter 50 can be inhibited in the other case where the torque command Tr* is small.

[0045] Fig. 5 is a flowchart of the setting processing according to the present embodiment. This setting processing is repeatedly executed at predetermined time intervals, for example, by the EPS-ECU 60.

[0046] When the adjustment processing starts, the EPS-ECU 60 first acquires the torque command Tr* from the torque sensor 94 in S14. The EPS-ECU 60 acquires the torque command Tr* adjusted in accordance with the steering torque Trq. In S16, the EPS-ECU 60 determines whether the torque command Tr* acquired in S14 is greater than a predetermined reference command Ttg. The predetermined reference command Ttg is a threshold for determining whether the driver suddenly operates the steering wheel 90. The steering torque Trq increases when the driver suddenly operates the steering wheel 90. Accordingly, the electrical angular velocity ω increases, and the torque command Tr* exceeds the predetermined reference command Ttg. Specifically, the steering torque Trq is large when the torque command Tr* is greater than the predetermined reference command Ttg.In the present embodiment, the processing in S14 may correspond to a "torque command value detection part", and the processing in S16 may correspond to a "setting section".

[0047] In a case where a negative determination is made in S16, the second converter 74 obtains the q-axis current Iqr in S18. In the subsequent S20, a first limit value Idm1 (see Fig. 6) associated with the q-axis current Iqr obtained in S18, and the limit value Idm is set to the first limit value Idm1. The first limit value Idm1 is set to a negative value.

[0048] In another case, where a positive determination is made in S16, the second converter 74 acquires the q-axis current Iqr in S22. In the subsequent S24, a second limit value Idm2 (see Fig. 6) associated with the q-axis current Iqr detected in S22 is determined, and the threshold value Idm is set to the second threshold value Idm2. The second threshold value Idm2 is set to a negative value having an absolute value greater than the absolute value of the first threshold value Idm1. The processing in S18 and S22 according to the present embodiment may correspond to a "current acquisition part."

[0049] In S26, the d-axis current command value setting section 81 obtains the negative second d-axis current command value Id*2. S28 involves determining whether the limit value Idm set in S20 or S24 is smaller than the second d-axis current command value Id*2 obtained in S26.

[0050] In a case where a negative determination is made in S28, that is, when the absolute value of the negative second d-axis current command value Id*2 is greater than the absolute value of the negative limit value Idm, the limit value Idm is maintained at the value set in S20 or S24, and the setting processing is terminated. In another case, where a positive determination is made in S28, that is, when the absolute value of the negative second d-axis current command value Id*2 is less than the absolute value of the negative limit value Idm, the limit value Idm is set to the second d-axis current command value Id*2, and the setting processing is terminated.

[0051] The first limit value Idm1 and the second limit value Idm2 are defined below with reference to Fig. 6. The memory 70 in the EPS-ECU 60 stores a limit map MPm that associates the q-axis current Iqr with the first limit value Idm1 and the second limit value Idm2. As shown in Fig. 6, the first limit value Idm1 and the second limit value Idm2 are set in a range Wa in which the q-axis current Iqr varies from zero to the rated current Ist of the rotating electric machine 20. The first limit value Idm1 is set to be smaller than the second limit value Idm2 in the range Wa. The EPS-ECU 60 determines in the setting processing which limit value Idm is set to the first limit value Idm1 or the second limit value Idm2 in accordance with the q-axis current Iqr thus obtained and the limit value map MPm.

[0052] As in Fig. 6, the first limit value Idm1 decreases linearly from a negative first reference value Ik1 to a negative second reference value Ik2 in a first range Wa1, which varies the q-axis current Iqr from zero to the first q-axis current Iqr1. The first limit value Idm1 is maintained at the second reference value Ik2 in a second range Wa2, in which the q-axis current Iqr varies from the first q-axis current Iqr1 to the second q-axis current Iqr2. The first limit value Idm1 increases linearly from the second reference value Ik2 to zero in a third range Wa3, in which the q-axis current Iqr varies from the second q-axis current Iqr2 to the rated current Ist.

[0053] The absolute value of the first limit value Idm1 is set to decrease as the q-axis current Iqr decreases in the first region Wa1 for the following reason. In the first region Wa1, the q-axis current Iqr is relatively small, and the rotating electric machine 20 requires a small torque. If the absolute value of the negative d-axis current Idr increases in the first region Wa1, the rotating electric machine 20, the first inverter 40, and the second inverter 50 are likely to overheat. The absolute value of the first limit value Idm1 is set to decrease as the q-axis current Iqr decreases in the first region Wa1 in the present embodiment, whereby it may be possible to inhibit overheating of the rotating electric machine 20, the first inverter 40, and the second inverter 50.

[0054] The second limit value Idm2 is maintained at a negative third set value Ik3, which is smaller than the second set value Ik2 in the first range Wa1 and the second range Wa2. The absolute value of the second limit value Idm2 does not decrease when the q-axis current Iqr decreases in the first range Wa1. In the first range Wa1 with a small q-axis current Iqr, a difference between the first limit value Idm1 and the second limit value Idm2 is set to be larger than the difference in the second range Wa2 where the q-axis current Iqr is large.

[0055] In the third range Wa3, the second limit value Idm2 increases from the third reference value Ik3 to zero in accordance with a predetermined lower limit value Imin determined by the rated current Ist of the rotating electric machine 20. The predetermined lower limit value Imin is a limit value set based on the fact that the resultant current of the q-axis current Iqr and the d-axis current Idr are equal to or less than the rated current Ist. Therefore, the third range Wa3 can be said to have the lower limit value Imin greater than the third reference value Ik3.

[0056] The present embodiment described in detail above achieves, for example, the following effect.

[0057] The rotating electric machine 20 experiences an increase in electrical angular velocity ω and a decrease in torque when the torque command Tr* is large. The absolute value of the negative limit value Idm must be set to be large to prevent a decrease in torque. Conversely, when the torque command Tr* is small, the absolute value of the negative limit value Idm must be set to be small to inhibit overheating of the rotating electric machine 20, the first inverter 40, and the second inverter 50. The torque command Tr* and the limit value Idm are thus correlated with each other.

[0058] The present embodiment includes setting the absolute value of the negative limit value Idm to be larger when the torque command Tr* is large compared to when the torque command Tr* is small. It may be possible to inhibit the reduction of the torque of the rotating electric machine 20 when the torque command Tr* is large. It may be possible to inhibit the overheating of the rotating electric machine 20, the first inverter 40, and the second inverter 50 when the torque command Tr* is small. It may be possible to appropriately limit the d-axis current command Id* of the rotating electric machine 20.

[0059] Specifically, in the EPS device 10 that outputs torque according to the driver's operation of the steering wheel 90, the steering wheel 90 may be suddenly operated to prevent collisions or the like. The sudden operation of the steering wheel 90 increases the steering torque Trq of the steering shaft 91, causing a corresponding increase in the torque command Tr*. The torque command Tr* increases as the steering torque Trq of the steering shaft 91 increases. It may be possible to appropriately set the threshold value Idm in accordance with the operation of the steering wheel 90.

[0060] The memory 70 in the EPS-ECU 60 according to the present embodiment stores the first limit value Idm1 and the second limit value Idm2. The limit value Idm is set to the first limit value Idm1 when the torque command value Tr* is smaller than the command value Ttg, and the limit value Idm is set to the second limit value Idm2 when the torque command value Tr* is greater than the command value Ttg. The limit value Idm set to the first limit value Idm1 inhibits overheating of the rotating electric machine 20, the first inverter 40, and the second inverter 50 in the voltage unsaturated state or the like. The limit value Idm set to the second limit value Idm2 inhibits the torque reduction of the rotating electric machine 20 in the voltage saturated state or the like.

[0061] The first limit value Idm1 and the second limit value Idm2 are stored in association with the q-axis current Iqr in the present embodiment. In the first range Wa1 with a small q-axis current Iqr, the difference between the first limit value Idm1 and the second limit value Idm2 is set larger than the difference in the second range Wa2 with a large q-axis current Iqr. Specifically, the absolute value of the first limit value Idm1 is set to be relatively smaller in the first range Wa1 than in the second range Wa2.

[0062] In the first range Wa1, the q-axis current Iqr is relatively small, and the rotating electric machine 20 requires a small torque. The rotating electric machine 20 requires a small torque, specifically in the case where the limit value Idm is set to the first limit value Idm1. When the absolute value of the first limit value Idm1 is set relatively large in the first range Wa1 and the absolute value of the d-axis current Idr, which causes no torque of the rotating electric machine 20, increases, the rotating electric machine 20, the first inverter 40, and the second inverter 50 are likely to overheat. The absolute value of the first limit value Idm1 according to the present embodiment is set to be relatively smaller in the first range Wa1 than in the second range Wa2.It may be possible to inhibit the increase of the absolute value of the d-axis current Idr to preferentially inhibit the overheating of the rotary electric machine 20, the first inverter 40 and the second inverter 50. (Second embodiment)

[0063] A second embodiment will be described below with reference to the drawings mainly with regard to the differences from the first embodiment.

[0064] The present embodiment differs in that, as in Fig. 7, the limit map MPm stores a plurality of second limit values ​​Idm2 associated with the q-axis current Iqr. The plurality of second limit values ​​Idm2 are set in a range Xa from the first limit value Idm1 to the lower limit value Imin, and specifically, the third, fourth, and fifth limit values ​​Idm3, Idm4, and Idm5 are stored. The lower limit value Imin corresponds to a "predetermined lower limit" according to the present embodiment. The multiple second limit values ​​may correspond to a plurality of second limit value positions.

[0065] The third limit value Idm3 is maintained at the third reference value Ik3 in the first range Wa1 and in the second range Wa2. The fourth limit value Idm4 is maintained at a negative fourth reference value Ik4, which is less than the third reference value Ik3, in the first range Wa1 and in the second range Wa2. The fifth limit value Idm5 is maintained at a negative fifth reference value Ik5, which is less than the fourth reference value Ik4, in the first range Wa1 and in the second range Wa2. For the fourth limit value Idm4, the lower limit value Imin is greater than the fourth reference value Ik4 in the second range Wa2. The fourth limit value Idm4 thus increases in accordance with the lower limit value Imin in a sub-range, where the lower limit value Imin is greater than the fourth reference value Ik4 in the second range Wa2. The same applies to the fifth limit value Idm5.

[0066] The limit value map MPm includes the third, fourth, and fifth limit values ​​Idm3, Idm4, and Idm5 associated with the vehicle speed Vm. In other words, the limit value map MPm associates the q-axis current Iqr and the vehicle speed Vm with the first limit value Idm1 and the second limit value Idm2. Specifically, the third limit value Idm3 is associated with the vehicle speed Vm in a low speed range that does not exceed the first reference speed. The fourth limit value Idm4 is associated with the vehicle speed Vm in a medium speed range that is greater than the first reference speed and equal to or less than the second reference speed, which is greater than the first reference speed. The fifth limit value Idm5 is associated with the vehicle speed Vm in a high speed range that is greater than the second reference speed.

[0067] The present embodiment includes different setting processing. Fig. 8 is a flowchart of the setting processing according to the present embodiment. Fig. 8 shows a processing that is compatible with the Fig. 5, which for the sake of simplicity is given the same reference symbol and will not be described repeatedly.

[0068] The setting processing according to the present embodiment includes S40 for obtaining the vehicle speed Vm from the vehicle speed sensor 34 when the torque command value Tr* obtained in S14 is determined to be greater than the predetermined reference command value Ttg in S16, that is, when the limit value Idm is set to the second limit value Idm2. In the subsequent S42, the limit value Idm is set to the second limit value Idm2 according to the vehicle speed Vm obtained in S40. Specifically, as in Fig. 7, the third limit value Idm3 is selected when the vehicle speed Vm is low. The selected second limit value Idm2 is switched from the third limit value Idm3 to the fourth limit value Idm4 and the fifth limit value Idm5 in the named order as the vehicle speed Vm increases. In S42, when the vehicle speed Vm is high, the limit value Idm is set to the second limit value Idm2 having a larger difference from the first limit value Idm1 compared to a case where the vehicle speed Vm is low. The processing in S40 according to the present embodiment may correspond to a "vehicle speed acquisition section."

[0069] As described above, according to the present embodiment, the second limit values ​​Idm2 include the third, fourth, and fifth limit values ​​Idm3, Idm4, and Idm5. When the vehicle speed Vm is high, the limit value Idm is set to the second limit value Idm2, which has a larger difference from the first limit value Idm1, compared to the case where the vehicle speed Vm is low. When the vehicle speed Vm is high, the absolute value of the second limit value Idm2 is set relatively larger than the case where the vehicle speed Vm is low.

[0070] Compared with the case where the vehicle speed Vm is low, when the vehicle speed Vm is high, the driver suddenly operates the steering wheel 90 at a higher operating speed to avoid a collision or the like, and the torque command Tr* increases accordingly. This results in an increase in the absolute value of the d-axis negative current Idr required to cancel the voltage saturated state of the rotating electric machine 20. When the vehicle speed Vm is high, the absolute value of the second limit value Idm2 is set to be relatively larger in the present embodiment compared to the case where the vehicle speed Vm is low. It is possible to cancel the voltage saturated state when the vehicle speed Vm is high. The torque of the rotating electric machine 20 is ensured, and it is possible to quickly steer the wheels 95. (Other embodiments)

[0071] The electric rotary machine is not limited to the EPS device.

[0072] Alternatively, the electric rotary machine may contain only one coil group.

[0073] Fig. 3 merely illustrates the circuit configuration of the EPS-ECU 60. The electric rotary machine 20 having the non-aligning pole structure does not necessarily include the d-axis current setpoint limiter 65. Fig. Figure 9 shows a circuit configuration of the EPS-ECU 60 for the rotating electric machine 20 having the non-aligned pole structure. The current command setting section 63 sets the q-axis current command Iq* in accordance with the torque command Tr* without adjusting the d-axis current command Id*.

[0074] The FB controller 66 calculates the d-axis voltage command value Vd* as a control input for controlling the d-axis current output from the second converter 74 to the limit value Idm output from the limit value setting section 82.

[0075] Alternatively, the limit value may be calculated in accordance with a numerical expression or the like instead of the map.

[0076] It should be noted that a flowchart or the processing of the flowchart in the present application includes multiple steps (also referred to as parts), each of which is represented individually as, for example, S14. Furthermore, each step may be divided into multiple substeps, while multiple steps may be combined into a single step.

[0077] Control devices and methods described in the present disclosure may be implemented by a special-purpose computer created by configuring a memory and a processor programmed to perform one or more specific functions contained in computer programs. Alternatively, the control units, control devices, and methods described in the present disclosure may be implemented by a special-purpose computer created by configuring a processor provided by one or more logic circuits for special-purpose hardware.Alternatively, the control units, control devices, and methods described in the present disclosure may be implemented by one or more special-purpose computers created by configuring a combination of a memory and a processor programmed to perform one or more specific functions, and a processor provided by one or more hardware logic circuits. The computer programs may be stored on a tangible, non-transitory, computer-readable medium as instructions executed by a computer.

[0078] While various embodiments, configurations, and aspects of a control device of a rotary electric machine according to the present disclosure have been exemplified, the embodiments, configurations, and aspects of the present disclosure are not limited to those described above. For example, embodiments, configurations, and aspects resulting from a suitable combination of technical elements disclosed in various embodiments, configurations, and aspects are also included within the scope of the embodiments, configurations, and aspects of the present disclosure.

Claims

[1] Control device (60) of an electric rotary machine (20) which controls an electric rotary machine (20), the control device (60) of the electric rotary machine (20) comprising: a torque command value (Tr*) acquisition section (S14) that acquires a torque command value (Tr*) for the electric rotary machine (20), and a setting part (S16) which sets a negative limit value (Idm) which limits a current command value (Id*) of the d-axis of the electric rotary machine (20), the current command value (Id*) of the d-axis being calculated in accordance with the torque command value (Tr*), where: the setting part (S16) sets the limit value (Idm) which has a larger absolute value in a case where the torque command value (Tr*) is large compared to a case where the torque command value (Tr*) is small, and in a case where the torque command value (Tr*) is equal to or less than a predetermined reference command value (Ttg), the setting part (S16) sets the negative limit value (Idm) of the current command value (Id*) of the d-axis to (i) to reduce it linearly from a negative first reference value (Ik1) to a negative second reference value (Ik2) in a first range (Wa1) in which the q-axis current (Iqr) varies from zero to a first q-axis current (Iqr1), (ii) to maintain it at the second reference value (Ik2) in a second range (Wa2) in which the q-axis current (Iqr) varies from the first q-axis current (Iqr1) to a second q-axis current (Iqr2), and (iii) to increase it linearly from the second reference value (Ik2) to zero in a third range (Wa3) in which the q-axis current (Iqr) varies from the second q-axis current (Iqr2) to a rated current (Ist) of the electric rotary machine (20). [2] Control device (60) of an electric rotary machine (20) according to claim 1, wherein: the setting part (S16) sets the limit value (Idm) to a first limit value (Idm1) in response to the torque command value (Tr*) being smaller than the predetermined reference command value (Ttg), and the setting part (S16) sets the limit value (Idm) to a second limit value (Idm2) which is greater in absolute value than the first limit value (Idm1) in response to the torque command value (Tr*) being greater than the reference command value (Ttg). [3] Control device (60) of an electric rotary machine (20) according to claim 2, further comprising: a current acquisition part (S18, S22) which acquires the current (Iqr) of the q-axis of the electric rotary machine (20), and a memory (70) storing a map (MPm) in which the q-axis current (Iqr) is associated with the first limit value (Idm1) and the second limit value (Idm2), where: the setting part (S16) determines to which of the limit values ​​(Idm), first limit value (Idm1) and second limit value (Idm2), the limit value (Idm) is set in accordance with the obtained current (Iqr) of the q-axis and the map (MPm), and in the map (MPm), a difference between the first limit value (Idm1) and the second limit value (Idm2) in a case where the q-axis current (Iqr) is small is larger than the difference between the first limit value (Idm1) and the second limit value (Idm2) in a case where the q-axis current (Iqr) is large. [4] Control device (60) of an electric rotary machine (20) according to claim 2, further comprising: a current acquisition part (S18, S22) which acquires the current (Iqr) of the q-axis of the electric rotary machine (20), a vehicle speed acquisition part (S40) that acquires a speed (Vm) of a vehicle (100) including the electric rotary machine (20), and a memory (70) storing a map (MPm) containing the q-axis current (Iqr) and the speed (Vm) of the vehicle (100) associated with the first limit value (Idm1) and the second limit value (Idm2), where: the map (MPm) contains a plurality of second limit value positions as the second limit value (Idm2), the second limit value positions being in a range from the first limit value (Idm1) to a predetermined lower limit value (Imin), the setting part (S16) determines to which of the first limit value (Idm1) and second limit value positions the limit value (Idm) is set in accordance with the acquired current (Iqr) of the q-axis and the map (MPm), and when setting the limit value (Idm) to one of the second limit value positions, the setting part (S16) sets the limit value (Idm) to one of second limit value positions having a larger difference from the first limit value (Idm1) in a case where the speed (Vm) being obtained is high compared to a case where the speed (Vm) is low. [5] System for an electric rotary machine (20), comprising: an electric power steering device (10) which outputs a torque corresponding to an operation of a steering wheel (90), an electric rotary machine (20) included in the electric power steering device (10), and the control device (60) of an electric rotary machine (20) according to one of claims 1 to 4, where: the torque setpoint (Tr*) increases as the torque output by the electric rotary machine (20) increases. [6] Control device (60) of an electric rotary machine (20) according to claim 2, further comprising: a current acquisition part (S18, S22) which acquires the current (Iqr) of the q-axis of the electric rotary machine (20), a memory (70) storing a map (MPm) in which a current (Iqr) of the q-axis is associated with the first limit value (Idm1) and the second limit value (Idm2), where: the setting part (S16) determines to which of the limit values ​​(Idm), first limit value (Idm1) and second limit value (Idm2), the limit value (Idm) is set in accordance with the obtained current (Iqr) of the q-axis and the map (MPm), and in the card (MPm), a difference between the first limit value (Idm1) and the second limit value (Idm2) in a case where the current (Iqr) of the q-axis is smaller than a predetermined current value is greater than the difference between the first limit value (Idm1) and the second limit value (Idm2) in a case where the current (Iqr) of the q-axis is larger than the predetermined current value. [7] Control device (60) of an electric rotary machine (20) according to claim 2, further comprising: a current acquisition part (S18, S22) which acquires the current (Iqr) of the q-axis of the electric rotary machine (20), a vehicle speed acquisition part (S40) that acquires a speed (Vm) of a vehicle (100) including the electric rotary machine (20), and a memory (70) storing a map (MPm) containing the q-axis current (Iqr) and the speed (Vm) of the vehicle (100) associated with the first limit value (Idm1) and the second limit value (Idm2), where: the map (MPm) contains a plurality of second limit value positions as the second limit value (Idm2), the second limit value positions being in a range from the first limit value (Idm1) to a predetermined lower limit value (Imin), the setting part (S16) determines to which of the first limit value (Idm1) and second limit value positions the limit value (Idm) is set in accordance with the acquired current (Iqr) of the q-axis and the map (MPm), and when setting the limit value (Idm) to one of the second limit value positions, the setting part (S16) sets the limit value (Idm) to one of the second limit value positions having a larger difference from the first limit value (Idm1) in a case where the speed (Vm) being obtained is faster than a reference speed compared to a case where the speed (Vm) is slower than the reference speed.

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