Motor control device and steering system having a motor control device

Abstract

Disclosed is a motor control device and a steering system having the same. A main power supply (10) having a large capacity and a backup power supply (20) having a small capacity are switched by a power supply switching determination unit (25) in the system. A motor control device (300) drives a motor (80) by the main power supply (10) or the backup power supply (20). A drive control unit (40) outputs a drive signal calculated by feedback control of a current detection value with respect to a current command value to an inverter circuit (70). In a case where the power supply switching determination unit (25) switches from the main power supply (10) to the backup power supply (20), the drive control unit (40) shifts from normal control using the main power supply to backup control that limits power consumption and prevents the backup power supply (20) from stopping.

Description

Technical Field

[0001] This disclosure relates to motor control devices and steering systems having motor control devices. Background Technology

[0002] Typically, in systems configured to switch between a main power supply and a backup power supply, there are known devices that use power from either the main power supply or the backup power supply to drive a motor.

[0003] For example, in the electric power steering device disclosed in Patent Document 1, when the motor is driven by a backup power supply, compared with the case of using the main power supply, the electric power steering device increases the d-axis current of the field weakening control and suppresses the decrease in motor speed caused by voltage drop.

[0004] Furthermore, motor control devices are generally known to limit the power supply current flowing from the power source to the inverter circuit to an upper limit value or less. For example, the motor control device disclosed in Patent Document 2 is applied to the drive of an IPM motor. This motor control device calculates the q-axis current limit value based on the voltage command value, the current detection value, and the target power supply current, and also uses a torque current limit value converted from the q-axis current limit value to limit the torque current command value proportional to the motor torque.

[0005] Existing technical documents

[0006] [Patent Literature]

[0007] Patent document 1: JP-2007-326379-A.

[0008] Patent document 2: JP-2020-127346-A. Summary of the Invention

[0009] A backup power supply is an emergency sub-battery used when the main power supply fails. Compared to the main power supply (e.g., a lead-acid battery), backup power supplies are required to be compact and inexpensive. However, they also have a smaller capacity. Therefore, when using a backup power supply, if the power current momentarily overshoots and the output exceeds the upper limit, the backup power supply stops and the motor output function is lost. For example, in an electric power steering system, there may be a difficulty where, when the backup power supply stops, the drive of the steering assist motor stops and the assist function is lost. Patent Documents 1 and 2 do not describe this difficulty.

[0010] This disclosure is provided in view of these points, and its purpose is to provide a motor control device for preventing loss of motor output function due to the interruption of the backup power supply when driving a motor using a backup power supply.

[0011] In the motor control device of this disclosure, the system is configured to switch between a main power supply and a backup power supply using a power switching determination unit. The main power supply is a DC power supply with a relatively large capacity, and the backup power supply is a DC power supply with a relatively small capacity. The system drives the motor using electricity from either the main power supply or the backup power supply.

[0012] The motor control unit includes an inverter circuit and a drive control unit. The inverter circuit converts DC power from the primary or backup power source into AC power and supplies it to the motor. The drive control unit outputs a drive signal calculated through feedback control of the current detection value relative to the current command value to the inverter circuit.

[0013] The drive control unit includes a current detection value conversion unit, a voltage command value calculation unit, and a voltage command upper limit protection unit. The current detection value conversion unit performs coordinate transformation on the detected values ​​of the phase current flowing from the inverter circuit to the motor, and calculates the d-axis current detection value and the q-axis current detection value.

[0014] The voltage command value calculation unit calculates the voltage command value or its related values ​​applied to the inverter circuit, namely the d-axis voltage command value and the q-axis voltage command value, such that the d-axis current detection value and the q-axis current detection value follow the d-axis current command value and the q-axis current command value, respectively. The voltage command upper limit protection unit protects the upper limit of the absolute values ​​of the d-axis voltage command value and the q-axis voltage command value through the voltage command upper limit protection value.

[0015] When the power switching determination unit switches from the main power supply to the backup power supply, the drive control unit changes from "normal control" performed when using the main power supply to "backup control" that limits power consumption and prevents the backup power supply from stopping. Therefore, the motor control device of this disclosure can prevent the loss of motor output function due to the interruption of the backup power supply. Furthermore, in systems using the motor control device of this disclosure, backup control can be implemented with a low-capacity backup power supply, thereby reducing the size and cost of the backup power supply.

[0016] Furthermore, this disclosure provides a steering system including: a steering assist motor that outputs steering assist torque; a reaction force motor that outputs reaction force torque for driver steering; and a rotation motor that rotates the tires. The motor control device controls the drive of at least one of the steering assist motor, reaction force motor, and rotation motor. The effectiveness of the motor control device is particularly demonstrated in steering systems requiring high reliability. Attached Figure Description

[0017] The above and other objects, features, and advantages of this disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. In the drawings:

[0018] Figure 1 This is a schematic diagram of an electric power steering system;

[0019] Figure 2 This is a schematic diagram of the steer-by-wire system.

[0020] Figure 3 This is a block diagram showing the power supply configuration of a system that utilizes a motor control device;

[0021] Figure 4 yes Figure 3 The flowchart of the power switching determination process in the system;

[0022] Figure 5 This is a block diagram of the feedback control unit shared by the drive control units of the first and second embodiments;

[0023] Figure 6 This is a block diagram of the current command calculation unit for the IPM motor in the drive control unit of the first embodiment;

[0024] Figure 7 This is a flowchart of the transition process to standby control;

[0025] Figure 8 It is a graph showing the relationship between the charge level and temperature of the backup power supply and the target allowable power.

[0026] Figure 9 This is a graph showing the relationship between the backup power supply's charge level and temperature and the upper limit protection value limit ratio; and

[0027] Figure 10 This is a block diagram of the current command calculation unit for the SPM motor in the drive control unit of the second embodiment. Detailed Implementation

[0028] In the following description, a motor control device according to several embodiments of the present disclosure will be described with reference to the accompanying drawings. The motor control device of each embodiment is applied to the steering system of a vehicle and controls the drive of a steering assist motor, a reaction force motor, and a rotation motor. Furthermore, the first embodiment uses an IPM motor as the driving target, and the second embodiment uses an SPM motor as the driving target. In the following description, the first embodiment and the second embodiment are collectively referred to as this embodiment.

[0029] [Steering System]

[0030] Reference Figure 1 and Figure 2 The schematic configuration of the electric power steering system (hereinafter referred to as the "EPS system") and the steer-by-wire system (hereinafter referred to as the "SBW system") is described as a steering system.Figure 1 and Figure 2 In the image, only one tire 99 is shown, while the tire on the opposite side is not shown.

[0031] Figure 1 The overall configuration of the EPS system 901 is shown, in which the steering mechanism and the rotation mechanism are mechanically coupled. Although Figure 1 A rack-assisted EPS system is shown, but this also applies to a column-assisted EPS system. In EPS system 901, the steering shaft 92 and the rack 97 are connected via an intermediate shaft 95.

[0032] When the driver operates the steering wheel 91, the rotational motion of the steering shaft 92 is transmitted to the pinion 96 via the intermediate shaft 95. The rotational motion of the pinion 96 is converted into the linear motion of the rack 97, and the tie rods 98 at both ends of the rack 97 cause the steering knuckle arm 985 to reciprocate, thereby rotating the tire 99.

[0033] The EPS system 901 includes a steering torque sensor 94, a motor control unit 300, and a steering assist motor 801. The steering torque sensor 94 is located in the middle of the steering shaft 92 to detect the steering torque applied by the driver. The motor control unit 300 includes a drive control unit 40 and an inverter circuit 70. The drive control unit 40 calculates the drive signal to be output to the inverter circuit 70 based on the steering torque, etc. The steering assist torque output by the steering assist motor 801, powered by the inverter circuit 70, is transmitted to the rack 97 via a reduction gear 89.

[0034] Figure 2 The overall structure of the SBW system 902 is shown, in which the steering mechanism and the rotation mechanism are mechanically separated. In the SBW system 902, the steering shaft 92 and the rack 97 are separate. A reaction force motor 802 is provided on the steering shaft 92 side to output a reaction torque for the driver's steering output. The reaction torque generated by the reaction force motor 802 is transmitted to the steering shaft 92 via a reduction gear 79. On the rack 97 side, a rotation motor 803 is provided to cause the rack 97 to move linearly, thereby rotating the tire 99. The torque of the rotation motor 803 is transmitted to the tire 99 via the reduction gear 89.

[0035] Motor control devices 300, including drive control units 40 and inverter circuits 70, are provided for both the reaction force motor 802 and the rotary motor 803. The drive control units 40 of the reaction force motor 802 and the rotary motor 803 communicate with each other and calculate the drive signals to be output to the corresponding inverter circuits 70, so that the reaction force motor 802 and the rotary motor 803 operate in cooperation with each other.

[0036] In this embodiment, the steering assist motor 801 of the EPS system 901, the reaction force motor 802 of the SBW system 902, and the rotation motor 803 all use three-phase brushless motors. The motor in the first embodiment is an IPM motor, i.e., an embedded permanent magnet synchronous motor with salient polarity. The motor in the second embodiment is an SPM motor, i.e., a surface permanent magnet synchronous motor. Each of motors 801, 802, and 803 can be configured as a mechanical / electrical integrated motor in which a motor control device 300 is integrally formed. Figure 3 In the following text, motor 801, motor 802 and motor 803 are collectively referred to as "motor 80".

[0037] [System Power Configuration]

[0038] Next, refer to Figure 3 The power supply configuration of the system using the motor control device 300 will be described. The system includes a main power supply 10 and a backup power supply 20. The main power supply 10 is a DC power supply with a relatively large capacity, and the backup power supply 20 is a DC power supply with a relatively small capacity. The backup power supply is an emergency sub-battery used in case the main power supply fails. Regarding the power supply voltage, as referenced in Patent Document 1 (JP-2007-326379-A, corresponding U.S. Publication: US2008 / 0277191A1), which is incorporated herein by reference, the main power supply 10 is a high-voltage battery of several hundred volts, and the backup power supply 20 is a low-voltage battery of 12 volts or the like. Alternatively, both the main power supply 10 and the backup power supply 20 may be low-voltage batteries of approximately 12V.

[0039] The backup power supply unit 200 includes a backup power supply 20, a temperature sensor 23, a switch 24, and a power switching determination unit 25. The positive terminal of the main power supply 10 is connected, as needed, via a step-down circuit 12 to one of the input terminals of the 2-input / 1-output switch 24. The positive terminal of the backup power supply 20 is connected to the other input terminal of the switch 24. The high-potential line Lp of the inverter circuit 70 is connected to the output terminal of the switch 24. The low-potential line Lg of the inverter circuit 70 has the same potential as the negative terminals of both the main power supply 10 and the backup power supply 20.

[0040] When the main power supply 10 is functioning normally, the input side of switch 24 is connected to the main power supply 10. The power switching determination unit 25 monitors the power supply voltage Vbtm of the main power supply 10, and if the power supply voltage Vbtm drops below a predetermined threshold due to a failure of the main power supply 10, the power switching determination unit 25 outputs a switching signal to switch 24 to connect the input side to the backup power supply 20. As described above, the system is configured to enable switching between the main power supply 10 and the backup power supply 20 via the power switching determination unit 25.

[0041] The motor control unit 300 includes an inverter circuit 70 and a drive control unit 40, and uses DC power from the main power supply 10 or the backup power supply 20 to drive the motor 80. The inverter circuit 70 includes multiple switching elements connected by a bridge between the upper and lower arms, and a smoothing capacitor disposed at the input section. The inverter circuit 70 converts the DC power from the main power supply 10 or the backup power supply 20 into AC power and supplies it to the motor 80.

[0042] The drive control unit 40 outputs a drive signal calculated through feedback control of the current detection value relative to the current command value to the inverter circuit 70. The drive control unit 40 includes a microcomputer, a pre-driver, etc., and has a CPU (not shown), ROM, RAM, I / O, buses connecting these components, etc. The drive control unit 40 performs software processing by executing a pre-stored program by the CPU, and performs hardware processing through dedicated electronic circuitry.

[0043] In addition, a current sensor 75 and a rotation angle sensor 84 are provided. The current sensor 75 is used to detect the phase current flowing from the inverter circuit 70 to the motor 80, and the rotation angle sensor 84 is used to detect the electrical angle θ of the motor 80. The current sensor 75 can detect the three-phase currents Iu, Iv, and Iw, or it can detect the current of two of the three phases and calculate the current of the remaining phase using Kirchhoff's laws. The arrangement of the current sensor 75 is not limited to the power path between the inverter circuit 70 and the motor 80 as shown in the attached figure, and it can be arranged inside the inverter circuit 70. The three-phase currents Iu, Iv, Iw and the electrical angle θ are acquired by the drive control unit 40.

[0044] Furthermore, when the power switching determination unit 25 switches from the main power supply 10 to the backup power supply 20, the power switching determination unit 25 notifies the drive control unit 40 that the backup state is valid. In the following text, in the drive control unit 40, the control executed when using the main power supply 10 is referred to as "normal control," and the control executed when using the backup power supply 20 is referred to as "backup control." Upon receiving the notification of the backup state, the drive control unit 40 switches from normal control to backup control.

[0045] During standby control, the drive control unit 40 obtains information about the charge level and temperature of the standby power supply 200 from the standby power supply unit 200. The charge level of the standby power supply 20 is determined, for example, based on the power supply current Ibtbu flowing from the standby power supply 20 to the inverter circuit 70. For example, the temperature of the standby power supply 20 is detected by a temperature sensor 23 installed near the standby power supply 20. Instead of being limited to a dedicated temperature detection value, the detection value of the outside air temperature or ambient temperature can also be used.

[0046] The charge level is not limited to a continuous value and can be acquired as multiple charge level levels, such as "Level 0, Level 1, Level 2, and Level 3". For example, Level 0 is defined as a charge rate of 0% to 25%, and Level 1 is defined as a charge rate of 25% to 50%. Temperature can be acquired, for example, based on the temperature dependence of the power supply characteristics, as a low-temperature flag that is turned on when the temperature is below a predetermined temperature.

[0047] Reference Figure 4 The flowchart describes the power switching determination process. In the flowchart description, the symbol "S" indicates a step. In S01, the power switching determination unit 25 acquires the power supply voltage Vbtm of the main power supply 10. In S02, it determines whether the power supply voltage Vbtm is lower than the threshold Vbtm_th. If it is "yes" in S02, in S03, the power switching determination unit 25 outputs a switching signal to the switch 24 to switch from the main power supply 10 to the standby power supply 20. Furthermore, in S04, the power switching determination unit 25 notifies the drive control unit 40 that the standby state is valid.

[0048] Here, because the backup power supply 20 has a small capacity, if the backup power supply 20 is used and the power supply current exceeds the output limit due to a momentary overshoot, the backup power supply 20 may stop and the output function of the motor 80 may be lost. For example, in an EPS system, there may be a difficulty where, when the backup power supply 20 stops, the drive of the steering assist motor may stop and the assist function may be lost.

[0049] Therefore, when the backup power supply 20 is used, the motor control device 300 of this embodiment performs backup control, that is, "control to limit power consumption and prevent the backup power supply 20 from stopping". In other words, "backup control" in this embodiment means "control to limit power consumption and prevent the backup power supply 20 from stopping". Specifically, the motor control device 300 limits the power in multiple control blocks of the drive control unit 40.

[0050] [Drive Control Unit]

[0051] Next, the detailed configuration of the drive control unit 40 will be described sequentially by dividing the drive control unit 40 into a first embodiment in which an IPM motor is the drive target and a second embodiment in which an SPM motor is the drive target. In an IPM motor, in addition to the magnet torque, which is the motor torque, magnetic reluctance based on the difference between the d-axis inductance and the q-axis inductance is generated. On the other hand, a conventional SPM motor does not generate magnetic reluctance torque. Magnetic reluctance torque is unusually generated in an intercalation-type SPM motor with salient polarity. In this disclosure, an intercalation-type SPM motor is considered to be included in the IPM motor category.

[0052] Based on this difference in characteristics, the drive control unit 40 has a different configuration specifically related to the calculation of the q-axis current command value. In the following description, the drive control unit 401 for the IPM motor will be described as a first embodiment, and the drive control unit 402 for the SPM motor will be described as a second embodiment. In the description of the first embodiment, common aspects will be described. Specifically, for the control configuration for the IPM motor, reference is made to Patent Document 2 (JP-2020-127346-A, corresponding US Publication: US2020 / 0252015A1). Figure 2 , Figure 3 , Figure 4 And so on, and incorporate them into this article by reference.

[0053] (First Implementation)

[0054] First, refer to Figures 5 to 9 The first embodiment is described. First, refer to... Figure 5 This section describes the control configuration shared by the drive control unit 401 of the first embodiment and the drive control unit 402 of the second embodiment. The shared portion mainly relates to the current feedback control via vector control, and in addition to the normal control configuration, it also includes a backup control configuration unique to this embodiment. Figure 5 In the description, the reference numeral for the drive control unit is referred to as "401".

[0055] The drive control unit 401 acquires the detected values ​​of phase currents Iu, Iv, and Iw detected by current sensor 75, and the electrical angle θ of motor 80 detected by rotation angle sensor 84. Furthermore, the drive control unit 401 acquires the inverter input voltage Vin from voltage sensors (not shown). Based on this information, the drive control unit 401 drives the inverter circuit 70 through feedback control. Additionally, the drive control unit 401 acquires standby status notification signals, the charging level of backup power supply 20, and temperature information.

[0056] The drive control unit 401 includes a three-phase to two-phase conversion unit 61, a current deviation calculation unit 62, a voltage command value calculation unit 63, a voltage command upper limit protection unit 67, a two-phase to three-phase conversion unit 68, and a PWM control unit 69, a target allowable power calculation unit 41, and a current limit value calculation unit 43, configured for normal control. Essentially, vector control is performed using dq-axis coordinates, where "current" and "voltage" refer to dq-axis current and dq-axis voltage, respectively.

[0057] The three-phase two-phase conversion unit 61, which is a "current detection value conversion unit", uses the electrical angle θ to convert the detection values ​​Iu, Iv and Iw of the phase current detected by the current sensor 75 into three-phase two-phase coordinates, thereby calculating the d-axis current detection value Id_sns and the q-axis current detection value Iq_sns.

[0058] The current deviation calculation unit 62 calculates the current deviations ΔId and ΔIq between the input d-axis current command value (referred to as "Id command value" in the figure) and q-axis current command value (referred to as "Iq command value" in the figure) and the d-q axis current detection values ​​Id_sns and Iq_sns fed back from the three-phase two-phase conversion unit 61. Here, because the specific signs of the Id command value and Iq command value differ between the drive control unit 401 of the first embodiment and the drive control unit 402 of the second embodiment, therefore... Figure 5 These symbols are not used in the text.

[0059] The voltage command value calculation unit 63 performs PI calculations to ensure that the d-axis current detection value Id_sns and the q-axis current detection value Iq_sns are consistent with the d-axis current command value and the q-axis current command value, respectively; that is, the current deviations ΔId and ΔIq are set to zero. The voltage command value calculation unit 63 calculates the d-axis voltage command value Vd and the q-axis voltage command value Vq, which are the target values ​​for the output voltage of the inverter circuit 70.

[0060] Furthermore, the voltage command value calculation unit 63 of this embodiment converts the dq axis voltage command values ​​Vd* and Vq* into dq axis duty cycle command values ​​Dd* and Dq* using the inverter input voltage Vin according to equations (1.1) and (1.2).

[0061] (Equations 1.1 and 1.2)

[0062]

[0063]

[0064] The dq-axis duty cycle command values ​​Dd* and Dq* are related values ​​of the dq-axis voltage command values ​​Vd* and Vq*. In this embodiment, the dq-axis duty cycle command values ​​Dd* and Dq* have a broad meaning and are interpreted as "dq-axis voltage command values". Therefore, the portion from the input, i.e., the current deviations ΔId and ΔIq, to ​​the output, i.e., the dq-axis duty cycle command values ​​Dd* and Dq*, is referred to as the "voltage command value calculation unit 63".

[0065] The voltage command upper limit protection unit 67 protects the upper limit of the absolute values ​​of the d-axis duty cycle command value Dd* and the q-axis duty cycle command value Dq* by using the voltage command upper limit protection value, and outputs the protected dq-axis duty cycle command values ​​Dd** and Dq**.

[0066] For example, the voltage command upper limit protection unit 67 calculates the protected d-axis duty cycle command value Dd**, and then calculates the protected q-axis duty cycle command value Dq** based on the protected d-axis duty cycle command value Dd** by multiplying it by the saturation protection calculation coefficient. At this time, the voltage command upper limit protection unit 67 can calculate the q-axis duty cycle command value Dq** using polynomial operations on the protected d-axis duty cycle command value Dd**. In the polynomial operations, for example, the value obtained by adding the 0th-order term to the 3rd-order term is calculated.

[0067] The two-phase to three-phase conversion unit 68 uses electrical angle θ to convert the protected duty cycle command values ​​Dd** and Dq** into three-phase duty cycle command values ​​Du*, Dv*, and Dw* through two-phase and three-phase coordinate transformation. The PWM control unit 69 generates voltage pulse signals as drive signals based on the three-phase duty cycle command values ​​Du*, Dv*, and Dw* and controls the inverter circuit 70. By switching the inverter circuit 70 according to the drive signal, the output voltage corresponding to the voltage command value is applied to the motor 80.

[0068] The target allowable power calculation unit 41 calculates the target allowable power Pinv_lim, which is the upper limit allowable value of the inverter power to be output by the inverter circuit 70. During normal control, the predetermined target allowable power Pinv_lim is output. The operation during standby control will be described later.

[0069] The current limit calculation unit 43 obtains the pre-protection d-axis duty cycle command value Dd* (d-axis voltage command value), the q-axis duty cycle command value Dq* (q-axis voltage command value), the d-axis current detection value Id_sns, the target allowable power Pinv_lim, and the inverter input voltage Vin. Information regarding the q-axis current detection value Iq_sns may not be necessary, therefore it is indicated by a dashed line. Based on this information, the current limit calculation unit 43 calculates the q-axis current limit value Iq_lim, ensuring that the inverter power is equal to or less than the target allowable power Pinv.

[0070] Equation (2) using equations (1.1) and (1.2) represents the inverter power Pinv.

[0071] (Equation 2)

[0072]

[0073] Here, in equation (2), the d-axis current Id is the detected value Id_sns, and the q-axis current Iq is the q-axis current limit value Iq_lim, thus obtaining equation (3). By rearranging equation (3), equation (4) is obtained regarding the q-axis current limit value Iq_lim.

[0074] (Equations 3 and 4)

[0075]

[0076]

[0077] Next, the backup control configuration unique to this embodiment will be described. The objective is to allow the power calculation unit 41 to obtain the charge level and temperature of the backup power supply 20. The objective is to allow the power calculation unit 41 to obtain the charge level as a multi-stage charge level, or to obtain the temperature as a low-temperature flag activated when the temperature is equal to or below a predetermined temperature.

[0078] When the target allowable power calculation unit 41 receives a notification of standby status, it switches to standby control and sets the target allowable power Pinv_lim to a value smaller than that under normal control. Furthermore, during standby control, the target allowable power calculation unit 41 variably sets the target allowable power Pinv_lim based on the charging level or temperature of the standby power supply 20. (See below for further details.) Figure 8 Describe the specific setup method.

[0079] In addition, a filter (referred to as "LPF" in the figure) 42 is provided on the output side of the target allowable power calculation unit 41 to suppress sudden changes in the target allowable power Pinv_lim when the standby control starts.

[0080] In addition, the drive control unit 401 has an upper limit protection value limit ratio calculation unit 65. The upper limit protection value limit ratio calculation unit 65 acquires notifications of the standby status, charge level, and temperature of the backup power supply 20. The upper limit protection value limit ratio calculation unit 65 can acquire the charge level as a multi-stage charge level, or it can acquire the temperature as a low-temperature flag that is activated when the temperature is equal to or lower than a predetermined temperature.

[0081] The upper limit protection value limit ratio calculation unit 65 calculates the upper limit protection value limit ratio α, which is "the limit ratio of the voltage command upper limit protection value during standby control period to the voltage command upper limit protection value during normal control period". During normal control, the upper limit protection value limit ratio calculation unit 65 sets the upper limit protection value limit ratio α to 1.

[0082] Upon receiving a notification of standby status, the upper limit protection value limit ratio calculation unit 65 switches to standby control and sets the upper limit protection value limit ratio α to a value greater than 0 and less than 1, that is, a value smaller than the value in normal control. Furthermore, during standby control, the upper limit protection value limit ratio calculation unit 65 variably sets the upper limit protection value limit ratio α based on the charging amount or temperature of the standby power supply 20. (See below for further details.) Figure 9 Describe the specific setup method.

[0083] In addition, a filter (designated as "LPF" in the drawing) 66 for suppressing a sudden change in the upper limit protection value limiting ratio α at the start of the standby control is provided on the output side of the upper limit protection value limiting ratio calculation unit 65.

[0084] The upper limit protection value limiting ratio α set by the upper limit protection value limiting ratio calculation unit 65 is input to the voltage command upper limit protection unit 67. During the standby control, the voltage command upper limit protection unit 67 protects the upper limits of the absolute values of the d-axis duty ratio command value Dd* and the q-axis duty ratio command value Dq* by multiplying the voltage command upper limit protection value by the limiting factor α, and outputs the protected dq-axis duty ratio command values Dd** and Dq**. This directly limits the power consumption.

[0085] Subsequently, Figure 6 , the configuration of the current command calculation unit for the IPM motor in the drive control unit 401 of the first embodiment will be described. The drive control unit 401 includes a torque current conversion unit 44, a torque current command value limiting unit 56, a field weakening control calculation unit 52, and a dq-axis current conversion unit 570 as normal control configurations. In an IPM motor that generates reluctance torque depending on both the d-axis current Id and the q-axis current Iq, it is effective to use a torque current proportional to the torque of the motor 80. For details of the torque current conversion unit 44, the torque current command value limiting unit 56, and the dq-axis current conversion unit 570, refer to Patent Document 2.

[0086] The torque current conversion unit 44 converts the q-axis current limit value Iq_lim into a torque current limit value Itrq_lim using the d-axis current detection value Id_sns. The torque current limit value Itrq_lim is a value reflecting the target allowable power Pinv_lim. Therefore, when the target allowable power Pinv_lim is limited during the standby control, the torque current limit value Itrq_lim is also limited. A filter can be provided after the torque current conversion unit 44.

[0087] The torque current command value limiting unit 56 compares the torque current command value Itrq* converted from the torque command value required by the motor with the torque current limit value Itrq_lim, and outputs the smaller value as the torque current command value Itrq**. That is, when "Itrq* < Itrq_lim", the torque current command value limiting unit 56 outputs the input torque current command value Itrq* as it is. On the other hand, when "Itrq* ≥ Itrq_lim", the torque current command value limiting unit 56 outputs the torque current limit value Itrq_lim.

[0088] The field weakening control calculation unit 52 calculates the d-axis current command value Id_wf* for field weakening control based on the rotational speed of the motor 80 and the saturation relative to the maximum applied voltage. By executing field weakening control that increases the absolute value of the negative d-axis current when the motor rotates at high speed, it is possible to prevent the current from becoming difficult to flow in the motor windings due to back electromotive force.

[0089] The dq-axis current conversion unit 570 acquires the limited torque current command value Itrq** and the limited d-axis current command value Id_wf*, and converts them into d-axis current command values ​​Id* and q-axis current command values ​​Iq*. The d-axis current command values ​​Id* and Iq* are input as feedback control command values ​​to the current deviation calculation unit 62. The limitation on the target allowable power Pinv_lim is reflected in the limitation on the torque current command value Itrq*, which in turn limits the dq-axis current command values ​​Id* and Iq*. Therefore, power consumption is limited.

[0090] Furthermore, the drive control unit 401 includes a field weakening control execution determination unit 51 and a d-axis current zero-point setting determination unit 53, configured as standby control. The field weakening control execution determination unit 51 determines whether to execute field weakening control. When field weakening control is executed, which increases the absolute value of the d-axis current command value Id*, power consumption increases. Therefore, in standby mode, power consumption is further limited by not executing field weakening control.

[0091] Here, in the electric power steering system of Patent Document 1, when using a backup power supply, priority is given to ensuring steering operability, which in turn increases the absolute value of the d-axis current. This is due to a difference in perspectives on what should be given the highest priority. First, backup control performed in an emergency may not meet all requirements. Even if steering operability is ensured, it is meaningless if the system stops. In view of this, in this embodiment, avoiding the shutdown of the backup power supply 20 is given the highest priority.

[0092] The d-axis current zero-point setting determination unit 53 determines whether to set the d-axis current command value Id* to 0A (zero amperes, hereinafter the same). Even without field weakening control, the absolute value of the d-axis current command value Id* is only reduced and is not always 0A. Therefore, in standby mode, the d-axis current zero-point setting determination unit 53 forcibly enables the valid flag for setting "Id* = 0A". This further limits power consumption.

[0093] As described above, the drive control unit 401 of the first embodiment completely limits power consumption by executing multiple power limits multiple times during standby control in the target allowable power calculation unit 41, the upper limit protection value limit ratio calculation unit 65, the field weakening control execution determination unit 51, and the d-axis current zero point setting determination unit 53. Therefore, loss of motor output function due to the shutdown of the backup power supply 20 can be avoided. Specifically, in the EPS system 901, steering assist function failure due to the stopping of the steering assist motor 801 can be avoided. In the SBW system 902, reaction force presentation function failure due to the stopping of the reaction force motor 802 and steering function failure due to the stopping of the rotation motor 803 can be avoided. Therefore, the reliability of the vehicle's steering system is improved.

[0094] Furthermore, in a system using the motor control device 300 of this embodiment, backup control can be achieved using a small-capacity backup power supply 20, thereby reducing the size and cost of the backup power supply 20.

[0095] Next, we will refer to Figure 7 Flowchart and Figure 8 and Figure 9 The transition process to standby control in the drive control unit 401 is described. In S10, it is determined whether a standby state is set, i.e., whether a standby state notification signal is received. If yes in S10, in the first embodiment, four steps S11, S12, S13, and S15 are executed as standby control. In the second embodiment, described later, three steps other than S15 are executed. The order in which these steps are executed can be any.

[0096] In S11, the target allowable power calculation unit 41 variably sets the target allowable power Pinv_lim based on the charging amount and temperature of the backup power supply 20. For example... Figure 8 As shown, the smaller the charge amount, the lower the target allowable power Pinv_lim is set. Furthermore, when temperature T2 is lower than the normal temperature T1, the target allowable power Pinv_lim is set even lower.

[0097] In S12, the upper limit protection value limit ratio calculation unit 65 variably sets the upper limit protection value limit ratio α within the range of "0 < α < 1" based on the charging amount and temperature of the backup power supply 20. For example... Figure 9 As shown, the smaller the charge amount, the lower the upper limit protection value limit α is set. Furthermore, when temperature T2 is lower than the normal temperature T1, the upper limit protection value limit α is set even lower.

[0098] exist Figure 8 and Figure 9In this system, the target allowable power Pinv_lim and the upper limit protection value limit ratio α can be progressively changed by using multiple charging levels. Furthermore, the mapping for charging can be switched between when the cryogenic flag is off and when it is on. By limiting the output values ​​to discrete numerical values, the computational load is reduced.

[0099] In S13, the field weakening control execution determination unit 51 determines that field weakening control will not be executed. In S14, it is determined whether the drive target is an IPM motor. In the case of the first embodiment, it is determined to be "yes" in S14, and in S15, the d-axis current zero point setting determination unit 53 enables the valid flag to set "Id*=0A".

[0100] On the other hand, if S10 is not true, S21 and S22 are executed as normal control. The execution order of S21 and S22 can be any order. In S21, the target allowable power calculation unit 41 sets the target allowable power Pinv_lim to the value under normal control. In S22, the upper limit protection value limit ratio calculation unit 65 sets the upper limit protection value limit ratio α to 1.

[0101] (Second Implementation)

[0102] Reference Figure 10 The configuration of the current command calculation unit for the SPM motor in the drive control unit 402 of the second embodiment will be described. Figure 10 In, with Figure 6 The configurations that are substantially the same are indicated by the same reference numerals and their description will be omitted. Regarding the configuration of the feedback control unit in the drive control unit 402, reference is made in common with the first embodiment. Figure 5 .

[0103] In the drive control unit 402 for SPM, the q-axis current limit value Iq_lim calculated by the current limit value calculation unit 43 is input to the q-axis current limit unit 59. The q-axis current limit unit 59 compares the q-axis current command value Iq* before limiting with the q-axis current limit value Iq_lim, sets the smaller value as the q-axis current command value Iq** after limiting, and outputs it to the current deviation calculation unit 62.

[0104] Regarding the d-axis current command value, a field weakening control execution determination unit 51 and a field weakening control calculation unit 52 are provided as in the drive control unit 401 of the first embodiment. The d-axis current command value Id_wf* for field weakening control calculated by the field weakening control calculation unit 52 is input to the current deviation calculation unit 62.

[0105] Regarding the control transition in the standby state in the second embodiment, Figure 8S11, S12, and S13 are the same as in the first embodiment. In the second embodiment, where the SPM motor is the driving target, S15 is skipped since it is determined to be "no" in S14. In the second embodiment, by limiting power consumption during standby control as in the first embodiment, loss of motor output function due to the shutdown of the standby power supply 20 can be avoided.

[0106] (Other implementation methods)

[0107] (A) in Figure 7 In the flowchart, during standby control, the power limiting of four items in the first embodiment and three items in the second embodiment are performed. It is not limited to this; one or more steps, including at least one of the target allowable power Pinv_lim and the upper limit protection value limit ratio α, may be performed. By performing at least a portion of the power limiting, loss of motor output function due to the shutdown of the standby power supply 20 can be avoided.

[0108] (B) During standby control, the target allowable power calculation unit 41 can variably set the target allowable power Pinv_lim using only information about the charge amount or temperature of the standby power supply 20. Alternatively, during standby control, the target allowable power calculation unit 41 can set the target allowable power Pinv_lim to a fixed value smaller than the value during normal control.

[0109] Similarly, during standby control, the upper limit protection value limit ratio calculation unit 65 can variably set the upper limit protection value limit ratio α using only information relating to either the charge amount or temperature of the backup power supply 20. Alternatively, during standby control, the upper limit protection value limit ratio calculation unit 65 can set the upper limit protection value limit ratio α to a fixed value greater than 0 and less than 1 (greater than zero and less than one).

[0110] (C) Without considering the impact of sudden changes in power limits at the start of standby control, filter 42 may not be provided on the output side of target allowable power calculation unit 41, or filter 66 may not be provided on the output side of upper limit protection value limit calculation unit 65.

[0111] (D) in Figure 3In the configuration example shown, the backup power supply unit 200 notifies the drive control unit 40 of the motor control unit 300 of the backup status, charge level, and temperature. Alternatively, the functional arrangement involving the determination and notification of various information may not be limited to these features. The transition to backup control can be determined based on the current and voltage values ​​detected by the motor control unit 300. For example, a power switching determination unit 25 can be provided internally in the motor control unit 300. In this case, the motor control unit 300 monitors the voltage Vbtm of the main power supply 10 and switches from the main power supply 10 to the backup power supply 20 when the voltage drops.

[0112] (E) During standby control, the charging amount of the backup power supply 20 may not be limited to the power supply current Ibtbu, and may be determined based on the battery capacity of the backup power supply 20. In this case, the backup power supply device 200 continuously detects the battery capacity after the start of standby control, converts it into charging amount, and notifies the drive control unit 40 of the motor control device 300. The drive control unit 40 accordingly sets the target allowable power Pinv_lim and the upper limit protection value limit ratio α.

[0113] (F) The motor control device of this embodiment is not limited to EPS or SBW steering systems, and can be applied to any motor drive system configured to switch between main power supply 10 and backup power supply 20.

[0114] The controllers and methods described in this disclosure can be implemented by a special-purpose computer created by configuring a memory and processor programmed to perform one or more specific functions embodied in a computer program. Alternatively, the controllers and methods described in this disclosure can be implemented by a special-purpose computer created by configuring a processor provided by one or more special-purpose hardware logic circuits. Alternatively, the controllers and methods described in this disclosure can be implemented by one or more special-purpose computers created by configuring a combination of a memory and processor programmed to perform one or more specific functions and a processor provided by one or more hardware logic circuits. The computer program can be stored as instructions executable by a computer in a tangible, non-transitory, computer-readable medium.

[0115] Note that the processing in the flowchart or process diagram in this application includes multiple parts (also referred to as steps), each of which is represented, for example, S1. Furthermore, each part can be divided into several sub-parts, and several parts can be combined into a single part. Additionally, each such configured part can also be referred to as a device, module, or apparatus.

[0116] While this disclosure has been described with reference to its embodiments, it should be understood that this disclosure is not limited to these embodiments and constructions. This disclosure is intended to cover various modifications and equivalent arrangements. Furthermore, although various combinations and configurations have been disclosed, other combinations and configurations including more, fewer, or only a single element are also within the spirit and scope of this disclosure.

Claims

1. A motor control device, in a system configured to switch between a main power supply having a large capacity DC power supply and a backup power supply having a small capacity DC power supply using a power switching determination unit, drives a motor via electricity from the main power supply or the backup power supply, the motor control device comprising: The system includes an inverter circuit and a drive control unit. The inverter circuit converts DC power from the main power supply or the backup power supply into AC power and supplies it to the motor. The drive control unit outputs a drive signal obtained through feedback control of the current detection value relative to the current command value. The drive control unit includes: The current detection value conversion unit performs coordinate transformation on the detected values ​​of the phase current flowing from the inverter circuit to the motor, and calculates the d-axis current detection value and the q-axis current detection value. A voltage command value calculation unit calculates the voltage command value to be applied to the inverter circuit, or the d-axis voltage command value and q-axis voltage command value as related values ​​of the voltage command value, such that the d-axis current detection value and q-axis current detection value respectively follow the d-axis current command value and q-axis current command value; and The voltage command upper limit protection unit protects the upper limit of the absolute value of each of the d-axis voltage command value and the q-axis voltage command value by using a voltage command upper limit protection value; and When the power switching determination unit switches from the main power supply to the backup power supply, the drive control unit changes from normal control performed when using the main power supply to backup control that prevents the backup power supply from stopping by limiting power consumption.

2. The motor control device according to claim 1, wherein: The drive control unit further includes: A target allowable power calculation unit calculates the target allowable power, which is the upper limit allowable value of the inverter power output by the inverter circuit; and The current limit calculation unit calculates the q-axis current limit value such that the inverter power calculated based on the d-axis voltage command value, the q-axis voltage command value, the d-axis current detection value, and the q-axis current detection value is equal to or less than the target allowable power; and The target allowable power calculation unit sets the target allowable power during the standby control period to be smaller than the target allowable power during the normal control period.

3. The motor control device according to claim 1, wherein: The drive control unit further includes: The upper limit protection value limitation ratio calculation unit calculates the upper limit protection value limitation ratio, which is the limitation ratio of the upper limit protection value of the voltage command under standby control to the upper limit protection value of the voltage command under normal control; and During the standby control period, the upper limit protection value limit ratio calculation unit sets the upper limit protection value limit ratio to be greater than zero and less than one.

4. The motor control device according to claim 2, wherein: During the standby control period, the target allowable power calculation unit variably sets the target allowable power based on the charging amount or temperature of the standby power supply.

5. The motor control device according to claim 3, wherein: During the standby control period, the upper limit protection value limit ratio calculation unit variably sets the upper limit protection value limit ratio based on the charging amount or temperature of the standby power supply.

6. The motor control device according to claim 4, wherein: The charge level of the backup power supply is determined based on the power supply current flowing from the backup power supply to the inverter circuit.

7. The motor control device according to claim 2, further comprising: A filter, which suppresses sudden changes in the target allowable power when the backup control is initiated, is located on the output side of the target allowable power calculation unit.

8. The motor control device according to claim 3, further comprising: A filter is provided on the output side of the upper limit protection value limit ratio calculation unit to suppress sudden changes in the upper limit protection value limit ratio when the backup control is started.

9. The motor control device according to claim 2, wherein: The drive control unit further includes a field weakening control execution determination unit, which determines whether to execute or not execute the field weakening control; and The field weakening control execution determination unit does not execute the field weakening control during the standby control period.

10. The motor control device according to claim 2, wherein: The motor is an IPM motor; The drive control unit further includes a d-axis current zero-point setting determination unit, which determines whether to set the d-axis current command value to zero; and The d-axis current zero-point setting determination unit sets the d-axis current command value to zero during the standby control period.

11. The motor control device according to any one of claims 1 to 10, wherein: The power switching determination unit switches from the main power supply to the backup power supply based on the main power supply voltage.

12. A steering system, comprising: The vehicle includes a steering assist motor, a reaction force motor, or a rotation motor, wherein the steering assist motor outputs steering assist torque, the reaction force motor outputs reaction force torque in response to the driver's steering operation, and the rotation motor causes the vehicle's tires to rotate. as well as The motor control device according to any one of claims 1 to 11 controls the drive of at least one of the steering assist motor, the reaction force motor, or the rotation motor that is the motor.

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