Motor control device, vehicle steering device, and motor control method

Abstract

To provide a motor control device, a vehicle steering device, and a motor control method capable of providing assist force according to steering conditions. [Solution] If the torque command value Tref for the motor is less than or equal to the torque threshold Tth (Step S101; No), and the angular velocity ω of the motor is less than or equal to the angular velocity threshold ωth (Step S103; No), control is performed to keep the d-axis current at zero (Step S201). If the torque command value Tref is greater than the torque threshold Tth (Step S101; Yes), maximum torque control is performed with the d-axis current added (Step S202). If the torque command value Tref is less than or equal to the torque threshold Tth (Step S101; No), and the angular velocity ω of the motor is greater than the angular velocity threshold ωth (Step S103; Yes), field weakening control is performed with the d-axis current added (Step S203).

Description

[Technical Field]

[0001] The present invention relates to a motor control device, a vehicle steering device, and a motor control method. [Background technology]

[0002] An electric steering system (EPS), one type of vehicle steering system, provides steering assistance (steering assist force) to the vehicle's steering system using the rotational force of a motor. Generally, permanent magnet synchronous motors such as surface magnet type SPMSM (Surface Permanent Magnet Synchronous Motor) and embedded magnet type IPMSM (Interior Permanent Magnet Synchronous Motor) are used as motors for EPS. In permanent magnet synchronous motors, torque degradation (a phenomenon in which the actual torque decreases relative to the torque command value) occurs due to the effect of armature reaction, reducing motor efficiency. Patent Document 1 below discloses a technology that utilizes reluctance torque generated by applying a d-axis current to suppress torque degradation in the high-load region. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 5897298 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In the conventional technology described above, advance angle control is performed in the high-load region where the actual torque decreases. This makes it possible to apply a high assist force during stationary steering, such as when parking a vehicle. On the other hand, increasing the d-axis current increases vibration along with the increase in reluctance torque, so depending on the setting of the high-load region, vibration and noise caused by reluctance torque may occur during normal steering. Furthermore, even in the low-load region, sudden steering, such as during emergency avoidance, can increase back electromotive force, which may hinder high-speed steering.

[0005] The present invention has been made in view of the above problems, and aims to provide a motor control device, a vehicle steering device, and a motor control method that can provide assist force according to the steering conditions. [Means for solving the problem]

[0006] To achieve the above objective, a motor control device according to one aspect of the present invention is a motor control device for driving a motor having salient polarity and a q-axis inductance greater than the d-axis inductance, wherein when the torque command value for the motor is less than or equal to a torque threshold and the angular velocity of the motor is less than or equal to an angular velocity threshold, the motor controls the d-axis current to be kept at zero; when the torque command value is greater than the torque threshold, the motor controls the maximum torque by adding a d-axis current; and when the torque command value is less than or equal to the torque threshold and the angular velocity of the motor is greater than the angular velocity threshold, the motor controls the field weakening by adding a d-axis current.

[0007] The above configuration makes it possible to provide assist force according to the steering situation. Specifically, for example, in the normal steering range of the vehicle, it is possible to suppress vibrations and noise caused by the generation of reluctance torque. Furthermore, it becomes possible to provide high assist force when turning the steering wheel while stationary, such as when parking the vehicle. In addition, it becomes possible to perform high-speed steering in sudden steering maneuvers, such as during emergency avoidance.

[0008] In a preferred configuration of the motor control device, it is preferable that the maximum value of the motor's magnet torque is set as the torque threshold.

[0009] This allows for maximum torque control with added d-axis current in the region where the torque command value is greater than the maximum value of the motor's magnet torque.

[0010] In a preferred configuration of the motor control device, when the torque command value is greater than the torque threshold, it is preferable to set the torque threshold for the next processing step to a value obtained by subtracting a small value from the torque threshold.

[0011] This makes it possible to suppress chattering in the threshold determination process of torque command values.

[0012] In a preferred configuration of the motor control device, the angular velocity threshold is preferably derived using the armature voltage of the motor and the voltage equation of the dq axis in a steady state.

[0013] This allows for field weakening control with added d-axis current in the region where the angular velocity is greater than that which can be tracked with d-axis current id=0.

[0014] In a preferred configuration of the motor control device, when the angular velocity of the motor is greater than the angular velocity threshold, it is preferable to set the value obtained by subtracting a small value from the angular velocity threshold as the angular velocity threshold for the next processing.

[0015] This makes it possible to suppress chattering in the threshold determination process for the motor's angular velocity.

[0016] In a preferred configuration of the motor control device, the motor may be an SPMSM (Surface Permanent Magnet Synchronous Motor).

[0017] In a preferred configuration of the motor control device, the motor may be an IPMSM (Interior Permanent Magnet Synchronous Motor).

[0018] To achieve the above objective, a vehicle steering device according to one aspect of the present invention includes the motor control device, the motor being mounted on the column shaft, pinion shaft, or rack shaft of the steering wheel, and assisting the steering force of the steering wheel.

[0019] A preferred embodiment of a vehicle steering system is that it comprises a torque command value generation unit that generates the torque command value based on the steering torque detected by a torque sensor and the vehicle speed detected by a vehicle speed sensor, and a current command value generation unit that generates a d-axis current command value and a q-axis current command value based on at least the torque command value and the angular velocity of the motor.

[0020] The above configuration makes it possible to provide assist force according to the steering situation. Specifically, for example, in the normal steering range of the vehicle, it is possible to suppress vibrations and noise caused by the generation of reluctance torque. Furthermore, it becomes possible to provide high assist force when turning the steering wheel while stationary, such as when parking the vehicle. In addition, it becomes possible to perform high-speed steering in sudden steering maneuvers, such as during emergency avoidance.

[0021] To achieve the above objective, a motor control method according to one aspect of the present invention is a motor control method for driving a motor having salient polarity and a q-axis inductance greater than the d-axis inductance, wherein when the torque command value for the motor is less than or equal to a torque threshold and the angular velocity of the motor is less than or equal to an angular velocity threshold, assist control by magnet torque is performed; when the torque command value is greater than the torque threshold, maximum torque control is performed by adding a d-axis current; and when the torque command value is less than or equal to the torque threshold and the angular velocity of the motor is greater than the angular velocity threshold, field weakening control is performed by adding a d-axis current.

[0022] This makes it possible to apply assist force according to the steering situation. Specifically, for example, it can suppress vibrations and noise caused by the generation of reluctance torque in the normal steering range of the vehicle. It also makes it possible to apply high assist force when turning the steering wheel while stationary, such as when parking the vehicle. Furthermore, it enables high-speed steering in sudden steering maneuvers, such as during emergency avoidance. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a motor control device, a vehicle steering device, and a motor control method that can provide assist force according to the steering conditions. [Brief explanation of the drawing]

[0024] [Figure 1] Figure 1 is a configuration diagram showing an overview of a vehicle steering device according to an embodiment. [Figure 2] Figure 2 is a schematic diagram showing the hardware configuration of a control unit for controlling a vehicle steering device according to an embodiment. [Figure 3] Figure 3 is a block diagram showing an example configuration of a motor control device according to an embodiment. [Figure 4A] Figure 4A is a schematic cross-sectional view showing the first example of SPMSM. [Figure 4B] Figure 4B is a schematic cross-sectional view showing a second example of SPMSM. [Figure 5] Figure 5 is a schematic cross-sectional view showing an example of an IPMSM. [Figure 6] Figure 6 shows an example of an assist map for deriving torque command values. [Figure 7] Figure 7 shows an example of the block configuration of the current command value generation unit. [Figure 8] Figure 8 is a flowchart showing a specific example of processing in the current command value generation unit. [Figure 9] Figure 9 is a conceptual diagram showing the steering range in EPS. [Figure 10] Figure 10 is a conceptual diagram showing the relationship between the advance angle value and the d-axis current and q-axis current in advance angle control. [Modes for carrying out the invention]

[0025] Hereinafter, embodiments for carrying out the invention (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments described below. Furthermore, the components in the embodiments described below include those that are easily conceivable by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the components disclosed in the embodiments described below can be combined as appropriate.

[0026] Figure 1 is a configuration diagram showing an overview of a vehicle steering system according to an embodiment. Figure 1 illustrates a vehicle steering system (hereinafter also referred to as "EPS"), which is one type of vehicle steering system.

[0027] The EPS is connected to the steering wheels 8L and 8R via hub units 7a and 7b, in the order in which the force applied by the helmsman is transmitted, through the steering column shaft (steering shaft, handle shaft) 2 of the steering wheel 1, a reduction mechanism 3, universal joints 4a and 4b, a pinion rack mechanism 5, tie rods 6a and 6b, and further to the steering wheels 8L and 8R via the column shaft 7a and 7b. The column shaft 2, which has a torsion bar, is equipped with a torque sensor 10 that detects the steering torque Ts of the steering wheel 1 and a steering angle sensor 14 that detects the steering angle θh. A motor 20 that assists the steering force of the steering wheel 1 is connected to the column shaft 2 via the reduction mechanism 3. Power is supplied to the control unit (ECU) 30 that controls the EPS from the battery 13, and an ignition key signal is input via the ignition key 11. The control unit 30 calculates the current command value of the assist (steering assistance) command based on the steering torque Ts detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12, and controls the current supplied to the motor 20 by applying compensation to the current command value. The motor 20 may be mounted on the pinion shaft or rack shaft of the pinion rack mechanism 5.

[0028] The control unit 30 is connected to an in-vehicle network such as a CAN (Controller Area Network) 40 for exchanging various vehicle information. In addition, the control unit 30 can also be connected to a non-CAN 41 for exchanging communications other than CAN 40, analog / digital signals, radio waves, etc.

[0029] The control unit 30 is mainly composed of a CPU (including an MCU, MPU, etc.). Figure 2 is a schematic diagram showing the hardware configuration of a control unit that controls a vehicle steering device according to this embodiment.

[0030] The control computer 1100, which constitutes the control unit 30, includes a CPU (Central Processing Unit) 1001, ROM (Read Only Memory) 1002, RAM (Random Access Memory) 1003, EEPROM (Electrically Erasable Programmable ROM) 1004, an interface (I / F) 1005, an A / D (Analog / Digital) converter 1006, a PWM (Pulse Width Modulation) controller 1007, etc., and these are connected to a bus.

[0031] The CPU 1001 is a processing unit that controls the EPS by executing a computer program for controlling the EPS (hereinafter referred to as the control program).

[0032] ROM 1002 stores the control program for controlling the EPS. RAM 1003 is used as work memory for running the control program. EEPROM 1004 stores control data and other information that the control program inputs and outputs. The control data is used by the control computer program loaded into RAM 1003 after power is supplied to the control unit 30, and is overwritten in EEPROM 1004 at predetermined timings.

[0033] ROM1002, RAM1003, and EEPROM1004, etc., are storage devices that store information and are storage devices (primary storage devices) that the CPU1001 can directly access.

[0034] The A / D converter 1006 receives input signals such as steering torque Ts, motor 20 current detection value Im, and steering angle θh, and converts them into digital signals.

[0035] Interface 1005 is connected to CAN40. Interface 1005 is for receiving the vehicle speed V signal (vehicle speed pulse) from the vehicle speed sensor 12.

[0036] The PWM controller 1007 outputs PWM control signals for each phase (UVW) based on the current command value for the motor 20.

[0037] Figure 3 is a block diagram showing an example configuration of a motor control device according to this embodiment. In this embodiment, each component constituting the motor control device 100 is realized by a control unit 30 that controls the EPS.

[0038] In this embodiment, the motor 20 is a three-phase brushless motor that rotates by supplying three phase alternating currents with a 120° phase difference to the u-phase, v-phase, and w-phase coils. Figure 3 shows a two-phase feedback type vector control system as an example of a vector control system in which the q-axis, which controls the torque and the d-axis, which controls the magnetic field strength, are set independently, and the currents corresponding to each axis (d-axis current and q-axis current) are controlled by the vectors of these axes, since the axes are in a 90° relationship.

[0039] In addition, in the present embodiment, the motor 20 is a permanent magnet synchronous motor such as a surface magnet type SPMSM (Surface Permanent Magnet Synchronous Motor) or an interior magnet type IPMSM (Interior Permanent Magnet Synchronous Motor). Further, as a prerequisite for the EPS control according to the present disclosure, in addition to the torque generated by the permanent magnet (hereinafter also referred to as "magnet torque"), the inductance L in the q-axis direction q (hereinafter also referred to as "q-axis inductance L q ") and the inductance L in the d-axis direction d (hereinafter also referred to as "d-axis inductance L d "), it is premised on using a motor in which reluctance torque is generated due to the difference therebetween.

[0040] FIG. 4A is a schematic cross-sectional view showing a first example of an SPMSM. FIG. 4B is a schematic cross-sectional view showing a second example of an SPMSM. FIG. 5 is a schematic cross-sectional view showing an example of an IPMSM. In FIGS. 4A, 4B, and 5, 21 indicates a stator core, 22 indicates windings, 23 indicates magnets, and 24 indicates a rotor core.

[0041] In the SPMSM, as shown in FIG. 4A, when the rotor core 24 is polygonal, the magnetic resistance of the q-axis becomes smaller than that of the d-axis, so the q-axis inductance L q becomes larger than the d-axis inductance L d . Thereby, reluctance torque that can be used as an assist force is generated.

[0042] Also, as shown in FIG. 4B, when there are protrusions 24a for positioning the magnets 23 on the rotor core 24, the magnetic resistance of the q-axis becomes smaller than that of the d-axis, so the q-axis inductance L q becomes larger than the d-axis inductance L d . Thereby, reluctance torque that can be used as an assist force is generated.

[0043] "L q >L dThe torque T of a motor with salient polarity is calculated by the number of pole pairs of the motor p n , the flux linkage by a permanent magnet is Ψ a , current phase (q-axis current i q armature current i a Let β be the phase difference between the two. This can be expressed by equations (1) and (2) below.

[0044]

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[0045]

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[0046] A rotation sensor (not shown), such as a resolver, is connected to the motor 20, and the electrical angle of the motor 20 is detected and input to the motor control device 100. Note that the rotation sensor is not limited to a resolver, but may be composed of other sensors, such as a rotary encoder.

[0047] The motor control device 100 includes a torque command value generation unit 31, a current command value generation unit 32, a subtraction unit 33, a PI control unit 34, a 2-phase / 3-phase conversion unit 35, a PWM control unit 36, an inverter 37, a 3-phase / 2-phase conversion unit 38, and an angular velocity calculation unit 39.

[0048] The inverter 37 drives the motor 20 using PWM based on the three-phase (u-phase, v-phase, w-phase) PWM signals from the PWM control unit 36. The inverter 37 also controls the u-phase current I flowing through each phase coil of the motor 20. u , v-phase current I v , w phase current I w , and armature voltage V r Outputs the armature voltage V. r v is defined by equation (3) below. d This shows the d-axis component of the armature voltage, and v dThis shows the q-axis component of the armature voltage. The voltage equations for the dq axis in the steady state with d-axis current id=0 are expressed by equations (4) and (5) below. Ra shown in equation (5) below represents the armature winding resistance.

[0049]

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[0050]

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[0051]

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[0052] The angular velocity calculation unit 39 is a component that calculates the angular velocity ω from the electrical angle of the motor 20.

[0053] The 3-phase / 2-phase conversion unit 38 receives the 3-phase u-phase current i output from the inverter 37. u , v phase current i v , w phase current i w The d-axis current i of the two phases d and q-axis current i q This is the component that converts to [a specific type of current]. The explanation of the conversion formula for calculating 2-phase current from 3-phase current will be omitted.

[0054] The torque command value generation unit 31 generates a torque command value Tref based on the steering torque Ts detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12. The torque command value Tref is derived using, for example, an assist map. Figure 6 shows an example of an assist map for deriving the torque command value.

[0055] The current command value generation unit 32 generates the torque command value Tref, the angular velocity ω of the motor 20, and the q-axis current i. q Based on this, the d-axis current command value I d ref and q-axis current command value I qThis generates a ref. A detailed explanation of the current command value generation unit 32 will be given later.

[0056] The subtraction unit 33 (33d) calculates the d-axis current command value I d ref and d-axis current i d ΔI d The subtraction unit 33 (33q) calculates the q-axis current command value I. q ref and q-axis current i q Q-axis current deviation ΔI q Calculate.

[0057] The PI control unit 34 calculates the d-axis current deviation ΔI from the subtraction unit 33. d and q-axis current deviation ΔI q PI control calculation is performed for the d-axis voltage command value V d ref and q-axis voltage command value V q Calculate the ref.

[0058] The 2-phase / 3-phase conversion unit 35 receives the 2-phase d-axis voltage command value V output from the PI control unit 34. d ref and q-axis voltage command value V q ref is the u-phase voltage command value V of the 3-phase system. u ref, v-phase voltage command value V v Ref, W-phase voltage command value V w This is the component that converts to ref. The conversion formula for calculating the three-phase voltage from the two-phase voltage is omitted.

[0059] The PWM control unit 36 ​​receives the u-phase voltage command value V output from the 2-phase / 3-phase conversion unit 35. u ref, v-phase voltage command value V v Ref, W-phase voltage command value V w Based on the reference, the duty cycles of the u-phase, v-phase, and w-phase PWM signals output to the inverter 37 are calculated.

[0060] The following describes in detail the specific configuration and processing of the current command value generation unit 32. Figure 7 is a diagram showing an example of the block configuration of the current command value generation unit. Figure 8 is a flowchart showing a specific example of processing in the current command value generation unit.

[0061] The current command value generation unit 32 includes a determination processing unit 321 and an arithmetic processing unit 322 as components for executing the processing according to the embodiment.

[0062] The determination processing unit 321 is a component that determines the steering region indicating the steering state in the EPS based on the torque command value Tref and the angular velocity ω of the motor 20.

[0063] In the processing flow shown in Figure 8, the determination processing unit 321 determines whether the torque command value Tref generated by the torque command value generation unit 31 is greater than the torque threshold Tth represented by the following equation (6) (step S101). The torque threshold Tth is stored, for example, in the EEPROM 1004 of the control computer 1100 that constitutes the control unit 30. In the following equation (6), i am This refers to the armature current i in EPS control. a This is the upper limit.

[0064]

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[0065] In equation (6) above, the maximum value of the magnet torque given by the first term on the right-hand side of equation (2) above is set as the torque threshold Tth.

[0066] If the torque command value Tref is less than or equal to the torque threshold Tth (maximum value of magnet torque) (step S101; No), the determination processing unit 321 sets the torque threshold Tth represented by the above equation (6) as the torque threshold Tth for the next step S101 (Tth = Tth), and updates the torque threshold Tth stored in the EEPROM 1004 (step S102).

[0067] Next, the determination processing unit 321 determines whether the angular velocity ω of the motor 20 is greater than the angular velocity threshold ωth expressed by equation (7) below (step S103). The angular velocity threshold ωth is stored, for example, in the EEPROM 1004 of the control computer 1100 that constitutes the control unit 30.

[0068]

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[0069] The angular velocity threshold ωth expressed by equation (7) above is equal to the armature voltage V defined by equation (3) above. r This can be derived by substituting the voltage equations for the dq axis in the steady state when the d-axis current id=0, as shown in equations (4) and (5) above.

[0070] If the angular velocity ω of the motor 20 is less than or equal to the angular velocity threshold ωth (step S103; No), the determination processing unit 321 sets the angular velocity threshold ωth represented by the above equation (7) as the angular velocity threshold ωth for the next step S103 (ωth=ωth), and updates the angular velocity threshold ωth stored in the EEPROM 1004 (step S104).

[0071] Figure 9 is a conceptual diagram showing the steering range in EPS. In Figure 9, the horizontal axis represents the assist force provided by EPS, and the vertical axis represents the steering speed.

[0072] The first region A1 shown in Figure 9 represents the normal steering range of the vehicle. The steering speed Y1 shown in Figure 9 is assumed to be, for example, 400 to 800 (deg / sec). The assist force X1 shown in Figure 9 is assumed to be approximately 80 to 90% of the assist force X2 (described later) (specifically, for example, 4000 to 13500 (N)). The calculation processing unit 322, when the torque command value Tref is less than or equal to the torque threshold Tth (maximum value of magnet torque) (step S101; No), and the angular velocity ω of the motor 20 is less than or equal to the angular velocity threshold ωth (step S103; No), uses equations (8) and (9) below to calculate the d-axis current command value I in the first region A1. d ref and q-axis current command value I q Calculate the ref.

[0073]

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[0074]

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[0075] Equation (9) above can be obtained by transforming the first term on the right-hand side of equation (1) above.

[0076] In the first region A1 shown in Figure 9, control is performed to keep the d-axis current Id at zero (step S201). In other words, in the first region A1 shown in Figure 9, the d-axis current command value I d Set ref to zero (I d (ref=0), assist control is performed using magnetic torque. This makes it possible to suppress vibrations and noise caused by the generation of reluctance torque, for example, in the normal steering range (first range) of the vehicle.

[0077] Returning to the process of step S101, if the torque command value Tref in step S101 is greater than the torque threshold Tth (maximum value of magnet torque) (step S101; Yes), the determination processing unit 321 sets the torque threshold Tth for the next step S101 process to a value obtained by subtracting a small value ΔT from the torque threshold Tth represented by the above equation (6) (Tth = Tth - ΔT), and updates the torque threshold Tth stored in the EEPROM 1004 (step S105).

[0078] The second region A2 shown in Figure 9 represents a high-load region where the magnetic torque alone is insufficient for assistance, for example, when steering a vehicle while parked. The assist force X2 shown in Figure 9 is assumed to be column EPS, pinion EPS, and rack EPS, and is set to, for example, 5000 to 15000 (N). In this disclosure, when the torque command value Tref is greater than the torque threshold Tth (maximum value of the magnetic torque) (step S101; Yes), the armature current i a The angle advance is controlled, and the d-axis current i d The following is added. Specifically, the arithmetic processing unit 322 uses equations (10) to (13) below to determine the d-axis current command value I in the second region A2. d ref and q-axis current command value I q Calculate the ref.

[0079]

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[0081]

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[0083] The armature current i shown in equation (12) above a This can be calculated using equation (2) above. The current phase β shown in equation (13) above is the optimal current phase that yields the maximum torque, obtained by partially differentiating equation (2) with respect to the current phase β.

[0084] Figure 10 is a conceptual diagram showing the relationship between the advance angle value and the d-axis current and q-axis current in advance angle control. In Figure 10, the armature current i a is the d-axis current i d and q-axis current i q It is represented by a composite vector. In the second region A2 shown in Figure 9, the current phase β shown in equation (13) above is applied as the advance angle value in advance angle control, and the d-axis current i d Maximum torque control is performed using the reluctance torque generated by adding this (step S202). This makes it possible to provide high assist force during stationary steering, such as when parking a vehicle.

[0085] The armature current i calculated using the above equation (12) is a Instead, the upper limit value of the armature current in EPS control i am It is also possible to use a method that calculates the current phase β (advance angle value) using [a specific method].

[0086] Returning to the process of step S101, if in step S101 the torque command value Tref is less than or equal to the torque threshold Tth (maximum value of magnet torque) (step S101; No), and in step S103 the angular velocity ω of the motor 20 is greater than the angular velocity threshold ωth (step S103; Yes), the determination processing unit 321 sets the angular velocity threshold ωth for the next step S103 as a value obtained by subtracting a small value Δω from the angular velocity threshold ωth expressed by equation (7) above (ωth = ωth - Δω), and updates the angular velocity threshold ωth stored in the EEPROM 1004 (step S106).

[0087] The third region A3 shown in Figure 9 is the back electromotive force ωΨ of the motor 20 due to sudden steering, such as during an emergency avoidance maneuver. aThis shows a region where the torque increases and is expected to hinder high-speed steering. The steering speed Y2 shown in Figure 9 is assumed to be about 200% of the steering speed Y1 (specifically, for example, 800 to 1600 (deg / sec)). In this disclosure, when the torque command value Tref is less than or equal to the torque threshold Tth (maximum value of magnet torque) (step S101; No), and the angular velocity ω of the motor 20 is greater than the angular velocity threshold ωth (step S103; Yes), the d-axis current i d Field weakening control is performed with the addition of the following. Specifically, the calculation processing unit 322 uses equations (14) and (15) below to determine the d-axis current command value I in the third region A3. d ref and q-axis current command value I q Calculate the ref.

[0088]

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[0089]

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[0090] Equation (14) above is the armature current i shown in equation (16) below. a and d-axis current i d and q-axis current i q In the relationship between the armature current upper limit i, am This is obtained by applying and transforming the formula. This results in the armature current upper limit value i am The d-axis current command value I is within a range that does not exceed d ref is set. Equation (15) above is obtained by rearranging equation (1) above.

[0091]

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[0092] In the third region A3 shown in Figure 9, the d-axis current i d By adding this, the magnetic flux generated by the armature reaction creates a magnetic flux linkage Ψ by the permanent magnet.a This allows for weakening of the field (field weakening control, step S203). This enables high-speed steering, such as in emergency evasive maneuvers.

[0093] As described above, in the configuration and processing according to the embodiment, when the torque command value Tref is less than or equal to the torque threshold Tth (maximum value of magnet torque) (step S101; No), and the angular velocity ω of the motor 20 is less than or equal to the angular velocity threshold ωth (step S103; No), assist control by magnet torque is performed. This makes it possible to suppress vibrations and noise caused by the generation of reluctance torque, for example, in the normal steering range (first range) of the vehicle.

[0094] Furthermore, if the torque command value Tref is greater than the torque threshold Tth (maximum value of the magnet torque) (step S101; Yes), the armature current i a The angle advance is controlled, and the d-axis current i d This adds a feature that allows for increased assist force during stationary steering maneuvers, such as when parking a vehicle.

[0095] Furthermore, if the torque command value Tref is less than or equal to the torque threshold Tth (maximum value of the magnet torque) (Step S101; No), and the angular velocity ω of the motor 20 is greater than the angular velocity threshold ωth (Step S103; Yes), the d-axis current i d Field weakening control is implemented with added functionality. This enables high-speed steering during sudden steering maneuvers, such as in emergency evasive maneuvers.

[0096] Furthermore, in the configuration and processing according to the above embodiment, if the torque command value Tref is greater than the torque threshold Tth (maximum value of the magnet torque) (step S101; Yes), the torque threshold Tth in the next step S101 is set to a value obtained by subtracting a small value ΔT from the torque threshold Tth represented by equation (6) above (Tth = Tth - ΔT). This makes it possible to suppress chattering in the threshold determination processing of the torque command value Tref (step S101).

[0097] Furthermore, if the angular velocity ω of the motor 20 is greater than the angular velocity threshold ωth (step S103; Yes), the angular velocity threshold ωth in the next step S103 is set to a value obtained by subtracting a small value Δω from the angular velocity threshold ωth expressed by equation (7) above (ωth = ωth - Δω). This makes it possible to suppress chattering in the threshold determination process for the angular velocity ω of the motor 20 (step S103).

[0098] The figures used above are conceptual diagrams intended to provide a qualitative explanation of this disclosure and are not limited to them. Furthermore, while the embodiments described above are examples of preferred implementations of this disclosure, they are not limited to them, and various modifications are possible without departing from the gist of this disclosure. [Explanation of Symbols]

[0099] 1 handle 2 Column axis 3 Reduction mechanism 4a, 4b Universal joint 5. Pinion Rack Mechanism 6a, 6b Tie rod 7a, 7b Hub Unit 8L,8R steering wheel 10 Torque Sensor 11 Ignition Key 12. Vehicle speed sensor 13 batteries 14. Steering angle sensor 20 motors 30 Control Unit (ECU) 31 Torque command value generation unit 32 Current command value generation unit 33, 33d, 33q Subtraction section 34 PI Control Unit 35 Two-phase / three-phase conversion unit 36 PWM control unit 37 Inverter 38 3-phase / 2-phase conversion unit 39 Angular velocity calculation section 100 Motor control device 321 Determination Processing Unit 322 Arithmetic Processing Unit 1001 CPU 1002 ROM 1003 RAM 1004 EEPROM 1005 Interface 1006 A / D Converter 1007 PWM Controller 1100 Control Computer (MCU) i a Armature Current i am Armature Current Upper Limit Value I d ref d-axis Current Command Value I q ref q-axis Current Command Value i d d-axis Current i q q-axis Current i u u-phase Current i v v-phase Current i w w-phase Current L d d-axis Inductance L q q-axis Inductance p n Number of Pole Pairs Tref Torque Command Value Tth Torque Threshold Value [[ID=7x]]V r Armature Voltage v d d-axis Component (Armature Voltage) v q q-axis Component (Armature Voltage) V d ref d-axis Voltage Command Value V q ref q-axis Voltage Command Value V u ref u-phase Voltage Command Value V v ref v-phase Voltage Command Value V w ref w-phase Voltage Command Value ΔI It should be noted that in the original text, there is a potential error in the "7x" in line 73. It might be a typo. I translated it as "V" according to the context. If this is not correct, please provide more accurate information.d d-axis current deviation ΔI q q-axis current deviation Ψ a locked magnetic beam β current phase ω angular velocity ωth angular velocity threshold

Claims

1. A motor control device for driving a motor having salient polarity and inductance greater than d-axis inductance, When the torque command value for the motor is below the torque threshold and the angular velocity of the motor is below the angular velocity threshold, control is performed to keep the d-axis current at zero. When the torque command value is greater than the torque threshold, maximum torque control is performed by adding a d-axis current. When the torque command value is less than or equal to the torque threshold, and the angular velocity of the motor is greater than the angular velocity threshold, field weakening control is performed by adding a d-axis current. Motor control device.

2. The maximum value of the magnet torque of the motor is set as the torque threshold. The motor control device according to claim 1.

3. If the torque command value is greater than the torque threshold, the torque threshold for the next processing step is set to a value obtained by subtracting a small value from the torque threshold. The motor control device according to claim 2.

4. The angular velocity threshold is derived using the armature voltage of the motor and the voltage equation of the dq axis in a steady state. The motor control device according to claim 1.

5. If the angular velocity of the motor is greater than the angular velocity threshold, the value obtained by subtracting a small value from the angular velocity threshold is set as the angular velocity threshold for the next processing. The motor control device according to claim 4.

6. The motor is an SPMSM (Surface Permanent Magnet Synchronous Motor). The motor control device according to claim 1.

7. The motor is an IPMSM (Interior Permanent Magnet Synchronous Motor). The motor control device according to claim 1.

8. A motor control device according to any one of claims 1 to 7, The motor is mounted on the steering column shaft, pinion shaft, or rack shaft of the vehicle's steering wheel, and assists the steering force of the steering wheel. Vehicle steering device.

9. A torque command value generation unit generates the torque command value based on the steering torque detected by the torque sensor and the vehicle speed detected by the vehicle speed sensor, A current command value generation unit that generates a d-axis current command value and a q-axis current command value based at least the torque command value and the angular velocity of the motor, Equipped with, The vehicle steering device according to claim 8.

10. The torque threshold Tth is calculated by the number of pole pairs of the motor p ｎ , the flux linkage by a permanent magnet is Ψ ａ armature current i ａ The upper limit of i ａｍ In that case, it can be expressed by equation (1) below, The angular velocity threshold ωth is determined by the armature winding resistance of the motor R ａ , q-axis current I ｑ , q-axis inductance L ｑ , armature voltage V ｒ In that case, it is expressed by the following equation (2): The vehicle steering device according to claim 9. [Math 1] [Math 2]

11. The current command value generation unit, When the torque command value is less than or equal to the torque threshold value and the angular velocity of the motor is less than or equal to the angular velocity threshold value, when the torque command value is set as Tref, the d-axis current command value I ｄ ref and the q-axis current command value I ｑ ref are calculated using the following equations (3) and (4). The vehicle steering device according to claim 10. [Math 3] [Math 4]

12. The current command value generation unit, When the torque command value is greater than the torque threshold, the d-axis inductance of the motor is set to L ｄ When the current phase is β and the torque command value is Tref, the d-axis current command value I is calculated using equations (5) to (8) below. ｄ ref and q-axis current command value I ｑ Calculate ref The vehicle steering device according to claim 10. [Math 5] [Math 6] [Number 7] [Number 8]

13. The current command value generation unit, When the torque command value is less than or equal to the torque threshold, and the angular velocity of the motor is greater than the angular velocity threshold, the d-axis inductance of the motor is set to L ｄ When the torque command value is Tref, the d-axis current command value I is calculated using the following equations (9) and (10). ｄ ref and q-axis current command value I ｑ Calculate ref The vehicle steering device according to claim 10. [Number 9] [Number 10]

14. A motor control method for driving a motor having salient polarity and whose q-axis inductance is greater than its d-axis inductance, When the torque command value for the motor is less than or equal to the torque threshold, and the angular velocity of the motor is less than or equal to the angular velocity threshold, assist control using magnetic torque is performed. When the torque command value is greater than the torque threshold, maximum torque control is performed by adding a d-axis current. When the torque command value is less than or equal to the torque threshold, and the angular velocity of the motor is greater than the angular velocity threshold, field weakening control is performed by adding a d-axis current. Motor control method.

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