Motor control device, electric power steering device, and vehicle

Abstract

A motor control device according to the present disclosure comprises: an inverter circuit that has a plurality of high-potential-side switching elements, a plurality of low-potential-side switching elements, and a plurality of electric current sensors; an electric power control unit that controls the plurality of high-potential-side switching elements and the plurality of low-potential-side switching elements on the basis of a duty value; and an abnormality detection unit that, for each phase of a plurality of phases, detects an abnormality by comparing a first threshold value and an offset electric current value that is detected using the electric current sensors with a first threshold value when the low-potential-side switching elements are in a non-conductive state, and determines a failure on the basis of the number of times the abnormality has been detected, wherein the abnormality detection unit, when an abnormality is detected by the comparison, causes the electric power control unit to generate a limit duty value in which the duty value of a phase to be restricted is limited to be equal to or greater than a predetermined lower limit value for the phase to be restricted including the phase in which the abnormality is detected, and causes the electric power control unit to perform duty limit processing for controlling the high potential-side switching elements and the low potential-side switching elements on the basis of the limit duty value.

Description

Motor control device, electric power steering device, and vehicle

[0001] The present disclosure relates to a motor control device, an electric power steering device, and a vehicle.

[0002] A motor control device for controlling a motor includes an inverter circuit having a high-side switching element and a low-side switching element, and a power control unit for controlling the inverter circuit. A current sensor is connected to the low-side switching element, and the current value detected by the current sensor is typically used to control the inverter circuit. Patent Documents 1 and 2 disclose a configuration in which the motor control device is provided with an abnormality detection unit that detects an abnormality based on the current value detected by the current sensor when no current flows through the current sensor (hereinafter referred to as the offset current value).

[0003] Japanese Patent No. 5168307 Japanese Patent No. 5023833

[0004] When the output of the inverter circuit is high and a switching signal indicating a low on-duty value is input to the inverter circuit, the conduction time of the low-potential side switching element becomes long, which may make it impossible to detect the offset current value using the current sensor. Even when the output of the inverter circuit is high, it is required to accurately detect an abnormality based on the offset current value without delay.

[0005] In view of the above circumstances, the present disclosure aims to provide a motor control device, an electric power steering device, and a vehicle that can prevent a decrease in motor output under normal conditions and can accurately and without delay detect abnormalities based on offset current values ​​even when the output of the inverter circuit is high.

[0006] One aspect of a motor control device according to the present disclosure is an inverter circuit that supplies power to a motor having windings for multiple phases, the inverter circuit having a plurality of high-potential side switching elements and a plurality of low-potential side switching elements provided corresponding to each of the multiple phases, and a plurality of current sensors connected to the plurality of low-potential side switching elements, respectively; a power control unit that controls the plurality of high-potential side switching elements and the plurality of low-potential side switching elements based on a duty value; and a power control unit that detects an abnormality for each of the multiple phases by comparing an offset current value detected by the current sensor when the low-potential side switching element is in a non-conducting state with a first threshold value. and an abnormality detection unit that outputs a value indicating a fault in the output of the power supply and determines a fault based on the number of times the abnormality is detected, and when an abnormality is detected by comparing the offset current value with the first threshold, the abnormality detection unit causes the power control unit to perform a duty limiting process, which is a process of controlling the high-potential side switching element and the low-potential side switching element based on the limited duty value, by generating a limited duty value for the target phase of limitation, which includes at least the phase in which the abnormality is detected, to be equal to or greater than a predetermined lower limit value so that the time during which the low-potential side switching element is in a non-conducting state is equal to or greater than the time required to detect the offset current value.

[0007] One aspect of the electric power steering device according to the present disclosure includes the motor control device, the motor that assists steering of the steering wheel, and a torque sensor that detects steering torque due to steering of the steering wheel, and the motor control device controls the drive of the motor in accordance with the steering torque detected by the torque sensor.

[0008] One aspect of the vehicle according to the present disclosure includes the electric power steering device and a notification unit that notifies the occurrence of a malfunction when the abnormality detection unit determines that a malfunction has occurred.

[0009] According to the present disclosure, it is possible to prevent a decrease in motor output during normal operation, and even when the output of the inverter circuit is high, it is possible to accurately and without delay detect abnormalities based on the offset current value.

[0010] 1 is an overall configuration diagram of a motor control device according to a first embodiment. FIG. 2 is a block diagram of a power control unit according to the first embodiment. FIG. 3 is a diagram for explaining the principle of generation of a switching signal in a PWM generating unit according to the first embodiment. FIG. 4 is a diagram showing an example of a duty value input to a power control unit according to the first embodiment. FIG. 5 is a diagram showing an example of a duty value input to a PWM generating unit according to the first embodiment. FIG. 6 is a flowchart showing a flow of processing performed by an abnormality detection unit according to the first embodiment. FIG. 7 is a flowchart showing a flow of processing performed by an abnormality detection unit according to a modified example of the first embodiment. FIG. 8 is a schematic configuration diagram of an electric power steering device according to a second embodiment. FIG. 9 is a diagram showing an example of a duty value input to a PWM generating unit according to a third embodiment. FIG. 10 is a diagram showing an example of a duty value input to a PWM generating unit according to the third embodiment.

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the scope of the present disclosure is not limited to the following embodiments and can be modified as desired within the scope of the technical concept of the present disclosure.

[0012] Embodiment 1. Figure 1 is an overall configuration diagram of a motor control device 100 according to embodiment 1. The motor control device 100 includes an inverter circuit 1, an abnormality detection unit 4, a power control unit 5, a current value acquisition unit 6, and a duty value generation unit 7. The motor control device 100 controls a motor 3 based on a control command input from outside the motor control device 100. A motor that is driven to rotate by a polyphase AC can be used as the motor 3. In embodiment 1, an example will be described in which the motor 3 is a three-phase brushless motor having a three-phase winding composed of a U-phase winding, a V-phase winding, and a W-phase winding.

[0013] A DC voltage is supplied to the inverter circuit 1 from a DC power supply unit 2. The inverter circuit 1 applies an AC voltage to three-phase windings of a motor 3 based on the DC voltage output from the DC power supply unit 2.

[0014] The inverter circuit 1 includes high-potential side switching elements 11u, 11v, and 11w, low-potential side switching elements 12u, 12v, and 12w, and current sensors 13u, 13v, and 13w. The inverter circuit 1 also includes a power supply line L1 connected to the positive electrode of the DC power supply unit 2 and a ground line L2 connected to the negative electrode of the DC power supply unit 2. The high-potential side switching element 11u, the low-potential side switching element 12u, and the current sensor 13u are provided corresponding to the U-phase of the motor 3. The high-potential side switching element 11v, the low-potential side switching element 12v, and the current sensor 13v are provided corresponding to the V-phase of the motor 3. The high-potential side switching element 11w, the low-potential side switching element 12w, and the current sensor 13w are provided corresponding to the W-phase of the motor 3. In the following description, the high potential side switching elements 11u, 11v, and 11w may be collectively referred to simply as the "high potential side switching elements 11." Similarly, the low potential side switching elements 12u, 12v, and 12w may be collectively referred to simply as the "low potential side switching elements 12." The current sensors 13u, 13v, and 13w may be collectively referred to simply as the "current sensors 13."

[0015] The high-potential side switching elements 11u, 11v, and 11w are connected to a power supply line L1. The low-potential side switching elements 12u, 12v, and 12w are connected to the high-potential side switching elements 11u, 11v, and 11w, respectively, and are also connected to a ground line L2 via current sensors 13u, 13v, and 13w, respectively. The connection point between the high-potential side switching element 11u and the low-potential side switching element 12u is connected to a U-phase winding of the motor 3. The connection point between the high-potential side switching element 11v and the low-potential side switching element 12v is connected to a V-phase winding of the motor 3. The connection point between the high-potential side switching element 11w and the low-potential side switching element 12w is connected to a W-phase winding of the motor 3.

[0016] The high-potential side switching elements 11u, 11v, 11w receive switching signals Gup, Gvp, and Gwp output from the power control unit 5, respectively. The low-potential side switching elements 12u, 12v, 12w receive switching signals Gun, Gvn, and Gwn output from the power control unit 5, respectively. The inverter circuit 1 performs chopper control of the high-potential side switching elements 11u, 11v, 11w and the low-potential side switching elements 12u, 12v, and 12w based on the switching signals Gup, Gvp, Gwp, Gun, Gvn, and Gwn. Specifically, the high-potential side switching elements 11u, 11v, 11w and the low-potential side switching elements 12u, 12v, 12w are turned on (conductive) or off (non-conductive) by the switching signals Gup, Gvp, Gwp, Gun, Gvn, and Gwn. For example, when the switching signal Gup is an "ON command (=1)," the high-potential side switching element 11u is turned on, and when the switching signal Gup is an "OFF command (=0)," the high-potential side switching element 11u is turned off. The same applies to the other switching elements 11v, 11w, 12u, 12v, and 12w. In this way, the inverter circuit 1 flows current through the three-phase windings of the motor 3 by switching the switching elements 11u, 11v, 11w, 12u, 12v, and 12w between the on and off states using the switching signals Gup, Gvp, Gwp, Gun, Gvn, and Gwn. This generates motor torque.

[0017] The high-side switching elements 11u, 11v, and 11w and the low-side switching elements 12u, 12v, and 12w are, for example, field effect transistors (FETs). Note that the switching elements 11u, 11v, 11w, 12u, 12v, and 12w may be any devices that can be switched between an on state and an off state by a switching signal. For example, the switching elements 11u, 11v, 11w, 12u, 12v, and 12w may be thyristors or bipolar transistors.

[0018] The current sensors 13u, 13v, and 13w are respectively disposed between the low-potential side switching elements 12u, 12v, and 12w and the ground line L2. The current sensors 13u, 13v, and 13w are respectively connected in series to the low-potential side switching elements 12u, 12v, and 12w. The current sensors 13u, 13v, and 13w detect the values ​​of currents flowing through the low-potential side switching elements 12u, 12v, and 12w. The current sensors 13u, 13v, and 13w are, for example, shunt resistors. It is sufficient for the current sensors 13u, 13v, and 13w to detect the values ​​of currents flowing through the low-potential side switching elements 12u, 12v, and 12w. For example, the current sensors 13u, 13v, and 13w may be current transformers (CTs) or Hall elements.

[0019] The current values ​​detected by the current sensors 13u, 13v, and 13w are input to the current value acquiring unit 6. The current value acquiring unit 6 has a sample-and-hold circuit. The current value acquiring unit 6 acquires offset current values ​​Iu, Iv, and Iw by performing a sample-and-hold process that holds the current values ​​detected by the current sensors 13u, 13v, and 13w at predetermined sample timings, and outputs the acquired offset current values ​​Iu, Iv, and Iw to the abnormality detecting unit 4 or the like. The offset current value Iu is the U-phase current value detected by the current sensor 13u when no current flows through the low-potential side switching element 12u (current sensor 13u). The offset current value Iv is the V-phase current value detected by the current sensor 13v when no current flows through the low-potential side switching element 12v (current sensor 13v). The offset current value Iw is the W-phase current value detected by the current sensor 13w when no current flows through the low-potential side switching element 12w (current sensor 13w). The sample timing occurs at each predetermined current detection period Ti. The sample timing is set to a timing when the low-potential side switching elements 12u, 12v, and 12w are in the off state. The offset current values ​​Iu, Iv, and Iw are used to calibrate the current sensor 13, for example, so that the value of the current sensor 13 when no current flows is 0 (A). The offset current values ​​Iu, Iv, and Iw are also used to detect abnormalities in the abnormality detection unit 4.

[0020] The abnormality detection unit 4 detects an abnormality in the power supply path that supplies power to the motor 3 based on the offset current values ​​Iu, Iv, and Iw detected by the current sensors 13u, 13v, and 13w. The abnormality detection unit 4 also determines a failure based on the number of times an abnormality is detected. Examples of causes of the failure include a short-circuit failure of the low-potential side switching elements 12u, 12v, and 12w, a failure of the current sensors 13u, 13v, and 13w, and a failure of the current value acquisition unit 6.

[0021] The detection of an abnormality by the abnormality detection unit 4 will be described below. In the following description, any one of the three phases will be referred to as the "x phase," and the offset current value of the x phase will be referred to as the "offset current value Ix."

[0022] If the power supply path supplying power to the motor 3 is normal, the offset current value Ix of the x-phase will be "0." The abnormality detection unit 4 compares the offset current value Ix input from the current value acquisition unit 6 with a predetermined abnormality detection threshold Ith (first threshold). If the offset current value Ix is equal to or less than the abnormality detection threshold Ith, the abnormality detection unit 4 determines that there is no abnormality in the x-phase. If the offset current value Ix is greater than the abnormality detection threshold Ith, the abnormality detection unit 4 determines that there is an abnormality in the x-phase (i.e., detects an abnormality in the x-phase). As described above, if the power supply path is normal, the offset current value Ix will be "0." Therefore, it is ideal to set the abnormality detection threshold Ith to "0." However, because the current value detected by the current sensor 13 may contain an error, the abnormality detection threshold Ith is set to a value slightly greater than "0."

[0023] The abnormality detection unit 4 outputs a duty limiting process flag according to the above detection result to the power control unit 5. Specifically, the abnormality detection unit 4 sets the duty limiting process flag of the phase in which the abnormality was detected to "true" and outputs it to the power control unit 5.

[0024] Furthermore, to prevent erroneous determination, the abnormality detection unit 4 does not determine a fault in a phase in which an abnormality is detected based on only one abnormality detection, but determines the fault after detecting the abnormality multiple times. Details of the fault determination will be described later. When the abnormality detection unit 4 determines a fault, it outputs a fault determination flag to an external control device or the like. This causes processes such as notifying the user of the motor 3 of the occurrence of a fault and stopping the motor 3 according to a predetermined process to be performed.

[0025] An external control command is input to the duty value generator 7. The duty value generator 7 generates a duty value based on the control command. The duty value generator 7 outputs the duty value to the power control unit 5. The duty values ​​include a U-phase duty value, a V-phase duty value, and a W-phase duty value. The U-phase duty value corresponds to the voltage to be applied to the U-phase winding of the motor 3. The U-phase duty value indicates the proportion of time that the U-phase high-potential side switching element 11u is energized relative to one signal period (carrier period Tc of a carrier triangular wave C described below), and ranges from 0 to 1 (0% to 100%). The V-phase duty value corresponds to the voltage to be applied to the V-phase winding of the motor 3. The V-phase duty value indicates the proportion of time that the V-phase high-potential side switching element 11v is energized relative to one signal period, and ranges from 0 to 1 (0% to 100%). The W-phase duty value corresponds to the voltage to be applied to the W-phase winding of the motor 3. The W-phase duty value indicates the proportion of time that the W-phase high-potential side switching element 11w is energized relative to one signal period, and ranges from 0 to 1 (0% to 100%).

[0026] The power control unit 5 receives a duty value from the duty value generation unit 7. The power control unit 5 receives a duty limiting process flag from the abnormality detection unit 4. The power control unit 5 drives the inverter circuit 1 based on the duty value and the duty limiting process flag.

[0027] Fig. 2 is a block diagram of the power control unit 5. As shown in Fig. 2, the power control unit 5 has a duty limiting unit 21, a selecting unit 22, and a PWM generating unit 23.

[0028] The duty limiting unit 21 receives a duty value from the duty value generating unit 7. The duty limiting unit 21 generates a limited duty value by limiting the duty value received from the duty value generating unit 7 to a predetermined limit threshold Duty_th (lower limit value) or greater. In this embodiment, the duty limiting unit 21 generates the limited duty value by performing clipping processing to make duty values ​​smaller than the limit threshold Duty_th equal to the limit threshold Duty_th. The duty limiting unit 21 outputs the limited duty value to the selecting unit 22.

[0029] The selector 22 receives an input of a duty value from the duty value generator 7. The selector 22 receives an input of a limited duty value from the duty limiter 21. The selector 22 receives an input of a duty limiting process flag from the abnormality detector 4. The selector 22 selects a duty value to be output to the PWM generator 23 based on the duty limiting process flag. Specifically, for phases subject to limitation, including at least phases for which the duty limiting process flag indicates "true", the selector 22 outputs the limited duty value generated by the duty limiter 21 to the PWM generator 23. For phases other than the phases subject to limitation, the selector 22 outputs the duty value output from the duty value generator 7 (i.e., a duty value that is not limited to or greater than the limit threshold Duty_th) to the PWM generator 23. In the present embodiment, the phase to be limited is the phase for which the duty limiting process flag indicates "true." That is, for example, if the duty limiting process flag for the U phase indicates "true" and the duty limiting process flags for the V and W phases indicate "false," the selector 22 outputs the U-phase limited duty value generated by the duty limiter 21 and the V-phase and W-phase duty values ​​output from the duty value generator 7 to the PWM generator 23. In the following description, the limited duty value or the duty value output from the selector 22 to the PWM generator 23 may be collectively referred to simply as the "duty value."

[0030] 4 is a diagram showing an example of duty values ​​input from the duty value generator 7 to the power controller 5. The horizontal axis of FIG. 4 represents time, and the vertical axis represents duty value. In the example shown, the duty value of the U phase is represented as DutyU, the duty value of the V phase as DutyV, and the duty value of the W phase as DutyW. As shown in FIG. 4, in this embodiment, the duty value of each phase changes in a sinusoidal waveform.

[0031] 5 is a diagram showing an example of the duty value input to the PWM generating unit 23 when the phase to be limited is the U phase. The horizontal axis of Fig. 5 represents time, and the vertical axis represents the duty value. In the example shown, the limit duty value of the U phase is indicated as DutyU_Limit.

[0032] The PWM generating unit 23 generates switching signals Gup, Gvp, Gwp, Gun, Gvn, and Gwn, which are control signals by PWM (Pulse Width Modulation) control, based on the duty value input from the selecting unit 22, and outputs the signals to the inverter circuit 1. In other words, the PWM generating unit 23 controls the high potential side switching elements 11u, 11v, and 11w and the low potential side switching elements 12u, 12v, and 12w based on the duty value input from the selecting unit 22. Specifically, for the phase to be limited, the PWM generating unit 23 controls the high potential side switching elements 11u, 11v, and 11w and the low potential side switching elements 12u, 12v, and 12w based on the limited duty value generated by the duty limiting unit 21. For the phases other than the phases to be restricted, the PWM generating unit 23 controls the high potential side switching elements 11u, 11v, 11w and the low potential side switching elements 12u, 12v, 12w based on the duty values ​​output from the duty value generating unit 7.

[0033] As described above, when the power control unit 5 receives a duty limiting processing flag indicating "true" from the abnormality detection unit 4, it generates a limiting duty value that limits the duty value output from the duty value generation unit 7 to a limit threshold value Duty_th or more for the phases to be limited, including at least the phase for which the duty limiting processing flag indicating "true" has been received, and performs duty limiting processing, which is a process of controlling the high-potential side switching elements 11u, 11v, 11w and the low-potential side switching elements 12u, 12v, 12w based on the limiting duty value.

[0034] Note that the power control unit 5 may perform duty limiting processing by changing the processing and thresholds in the duty limiting unit 21 according to the duty limiting processing flag, without using the selection unit 22. For example, for a phase to be limited, the duty limiting unit 21 generates a limited duty value that limits the duty value to a limit threshold Duty_th or more, and outputs the limited duty value to the PWM generation unit 23. For phases other than the phase to be limited, the duty limiting unit 21 does not process the duty value output from the duty value generation unit 7, and outputs the duty value output from the duty value generation unit 7 directly to the PWM generation unit 23. The PWM generation unit 23 controls the high-potential side switching elements 11u, 11v, and 11w and the low-potential side switching elements 12u, 12v, and 12w based on the duty value input from the duty limiting unit 21.

[0035] A method for generating a switching signal by the PWM generating unit 23 will be described with reference to Fig. 3. Note that the following description will be made on the U phase, representing the three phases of U, V, and W. In other words, the following description also applies to the V and W phases.

[0036] FIG. 3 shows the time series changes in the U-phase duty value, carrier triangular wave C with carrier period Tc (carrier frequency fc), and U-phase switching signals Gup and Gun. The horizontal axis of FIG. 3 represents time, and the vertical axis represents signal level. The carrier frequency fc is, for example, 20 kHz. The U-phase duty value ranges from 0 to 1 (0% to 100%). The carrier triangular wave C also ranges from 0 to 1 (0% to 100%). The PWM generation unit 23 generates the U-phase switching signals Gup and Gun by comparing the U-phase duty value with the carrier triangular wave C.

[0037] Specifically, when the U-phase duty value is larger than the carrier triangular wave C, the PWM generation unit 23 sets the high-potential side switching signal Gup to "1" as an ON command and sets the low-potential side switching signal Gun to "0" as an OFF command. That is, when the U-phase duty value is larger than the carrier triangular wave C, the PWM generation unit 23 sets the U-phase high-potential side switching element 11u to the ON state and the U-phase low-potential side switching element 12u to the OFF state. When the U-phase duty value is smaller than the carrier triangular wave C, the PWM generation unit 23 sets the high-potential side switching signal Gup to "0" as an OFF command and sets the low-potential side switching signal Gun to "1" as an ON command. That is, when the U-phase duty value is smaller than the carrier triangular wave C, the U-phase high-potential side switching element 11u to the OFF state and the U-phase low-potential side switching element 12u to the ON state. Strictly speaking, in order to prevent the high-potential side switching element 11u and the low-potential side switching element 12u from being turned on at the same time, a dead time is provided during which both the high-potential side switching element 11u and the low-potential side switching element 12u are turned off for a very short period of time.

[0038] The reason for performing the duty limiting process will be explained below with reference to FIGS.

[0039] As described above, the duty value includes a U-phase duty value, a V-phase duty value, and a W-phase duty value. The greater the voltage difference between the phases, the stronger the tendency to pass current through the three-phase windings of the motor 3. Therefore, when the output of the inverter circuit 1 is high, the amplitude of the duty value increases. When a switching signal indicating a low duty value is input to the inverter circuit 1, the low-potential-side switching element 12 of the phase to which this switching signal is input is kept in the ON state for a longer period (i.e., the low-potential-side switching element 12 is kept in the OFF state for a shorter period). Here, the time required to detect the offset current value using the current sensor 13 is referred to as the current detection time. If the time the low-potential-side switching element 12 is kept in the OFF state is shorter than the current detection time, the current sensor 13 cannot detect the offset current value. In this case, the anomaly detection unit 4 cannot detect an anomaly based on the offset current value. Furthermore, the anomaly detection unit 4 determines a fault by detecting an anomaly multiple times. To perform such a fault determination, it is necessary to constantly detect the offset current value of the phase in which the abnormality is detected during the fault determination period. In the example of FIG. 4 , for example, during the period from 0.15 seconds to approximately 0.3 seconds, the duty values ​​of the three phases are equal to or greater than the limit threshold Duty_th. In this case, since there is an electrical angle during which the offset current value can be detected, if the fault determination period is short, the abnormality can be detected. However, as the rotation speed of the motor 3 increases, the electrical angle during which the offset current value can be detected becomes shorter. Furthermore, the amplitude of the duty value tends to increase due to the back electromotive force of the motor 3. Therefore, in this case, it becomes difficult to constantly detect the offset current value of the phase in which the abnormality is detected during the fault determination period.

[0040] In this embodiment, a duty limiting process is performed in which a limit duty value is generated for the phase to be limited, the limit duty value being equal to or greater than a limit threshold Duty_th, and the high-potential side switching elements 11u, 11v, and 11w and the low-potential side switching elements 12u, 12v, and 12w are controlled based on the limit duty value. The limit threshold Duty_th is set to a value that ensures that the time during which the low-potential side switching element 12 is in the off state is equal to or greater than the current detection time (e.g., 5 μs). The limit threshold Duty_th is, for example, 0.1 (10%).

[0041] By performing the duty limiting process, the power control unit 5 can ensure that the low-side switching element 12 is in the off state for a period of time equal to or longer than the current detection time for the phase to be limited, and therefore the offset current value can be reliably acquired using the current sensor 13. In other words, when the duty limiting process is performed, abnormalities can be reliably detected for the phase to be limited based on the offset current value. Note that if the duty value is equal to or greater than the limit threshold Duty_th, the low-side switching elements 12u, 12v, and 12w of all phases are in the off state around the time when the carrier triangular wave C becomes 0. Therefore, the sampling timing in the current value acquiring unit 6 is set to the above time.

[0042] 6 is a flowchart showing the flow of processing performed by the abnormality detection unit 4. The abnormality detection processing by the abnormality detection unit 4 is performed, for example, at every current detection period Ti. The current detection period Ti is an integer multiple of the carrier period Tc of the carrier triangular wave C. The abnormality detection processing by the abnormality detection unit 4 may be performed at every period that is an integer multiple of the current detection period Ti. Furthermore, the abnormality detection processing by the abnormality detection unit 4 is performed in parallel for each of the U phase, V phase, and W phase. Below, an example will be described in which the abnormality detection processing is performed in an "x phase," which is any one of the three phases.

[0043] In step S101, the abnormality detection unit 4 acquires Duty_x, which is the Duty value of the x-phase, and determines whether Duty_x is smaller than the limit threshold Duty_th. If Duty_x is smaller than the limit threshold Duty_th (step S101: YES), the offset current value Ix of the x-phase cannot be detected, and the determination in the subsequent step S102 cannot be made, so this flowchart ends.

[0044] If Duty_x is equal to or greater than the limit threshold Duty_th (step S101: NO), the process proceeds to step S102. In step S102, the abnormality detection unit 4 calculates the absolute value |Ix| of the offset current value Ix of the x phase input from the current value acquisition unit 6, and determines whether the absolute value |Ix| is greater than the abnormality detection threshold Ith.

[0045] If the absolute value |Ix| is equal to or smaller than the abnormality detection threshold Ith (step S102: NO), it is determined that there is no abnormality in the x-phase, and the process proceeds to step S201.

[0046] If the absolute value |Ix| is greater than the abnormality detection threshold Ith (step S102: YES), it is determined that an abnormality exists in the x-phase (an abnormality in the x-phase is detected), and the process proceeds to step S103. In step S103, the abnormality detection unit 4 increments a free-running counter (FRC), which indicates the number of times an abnormality has been detected, by 1. After step S103, the process proceeds to step S104. In step S104, the abnormality detection unit 4 sets the duty limiting process flag for the x-phase to "true" and outputs it to the power control unit 5. This causes the power control unit 5 to execute the duty limiting process. After step S104, the process proceeds to step S201. Note that if the power control unit 5 is already executing the duty limiting process, the determination result in step S101 is always "YES," and the process always proceeds to step S102 after step S101.

[0047] In step S201, it is determined whether it is time to execute a failure determination routine. Specifically, in step S201, the abnormality detection unit 4 determines whether the current cycle is a preset failure determination cycle Te. The failure determination cycle Te is an integer multiple (e.g., several to several tens of times) of the current detection cycle Ti. If the current cycle is not the failure determination cycle Te (step S201: NO), this flowchart ends.

[0048] If the current cycle is the failure determination cycle Te (step S201: YES), the process proceeds to step S202. In step S202, the abnormality detection unit 4 determines whether the free-running counter (FRC) is equal to the free-running counter (FRCpast) at the time of the previous execution of the failure determination routine.

[0049] If the free-running counter (FRC) and the free-running counter (FRCpast) at the time of the previous execution of the fault determination routine are not the same (step S202: NO), this means that step S103 has been executed one or more times since the previous execution of the fault determination routine. That is, this means that the absolute value |Ix| has been determined to be greater than the abnormality detection threshold Ith one or more times in step S102 since the previous execution of the fault determination routine (i.e., an abnormality has been detected in the x-phase one or more times). In this case, since a fault is suspected, the abnormality detection unit 4 increments the abnormality counter by 1 in step S203. Then, the process proceeds to step S204.

[0050] In step S204, the abnormality detection unit 4 determines whether the abnormality counter is equal to or greater than the fault determination threshold Nth. If the abnormality counter is equal to or greater than the fault determination threshold Nth (step S204: YES), in step S205, the abnormality detection unit 4 determines that a fault has occurred and outputs a fault determination flag to an external control device or the like.

[0051] If the abnormality counter is smaller than the fault determination threshold Nth (step S204: NO), the process proceeds to step S208.

[0052] If the free-running counter (FRC) and the free-running counter (FRCpast) at the time of the previous execution of the fault determination routine are the same (step S202: YES), this means that step S103 has not been executed since the previous execution of the fault determination routine. That is, since the previous execution of the fault determination routine, the state in which the absolute value |Ix| is determined to be equal to or less than the abnormality detection threshold Ith in step S102 has been maintained, and no abnormality has been continuously detected in the x-phase. In this case, since there is no suspicion of a fault, in step S206 the abnormality detection unit 4 sets the duty limiting process flag for the x-phase to "false" and outputs this to the power control unit 5. This causes the power control unit 5 to cancel (end) the duty limiting process. In addition, in step S207, the abnormality detection unit 4 resets the abnormality counter. Then, the process proceeds to step S208.

[0053] In step S208, the abnormality detection unit 4 assigns the free-running counter (FRC) to a variable FRCpast, and ends this flowchart.

[0054] As described above, the motor control device 100 according to this embodiment includes an inverter circuit 1 that supplies power to a motor 3 having windings for multiple phases, a power control unit 5, and an abnormality detection unit 4. The inverter circuit 1 includes a plurality of high-potential side switching elements 11u, 11v, and 11w and a plurality of low-potential side switching elements 12u, 12v, and 12w that are provided corresponding to each of the multiple phases, and a plurality of current sensors 13u, 13v, and 13w that are connected to the plurality of low-potential side switching elements 12u, 12v, and 12w, respectively. The power control unit 5 controls the plurality of high-potential side switching elements 11u, 11v, and 11w and the plurality of low-potential side switching elements 12u, 12v, and 12w based on a duty value. The abnormality detection unit 4 detects abnormalities by comparing the offset current values ​​Iu, Iv, Iw detected using the current sensors 13u, 13v, 13w when the low-potential side switching elements 12u, 12v, 12w are in the off state with the abnormality detection threshold Ith for each of the multiple phases, and determines whether a failure has occurred based on the number of times the abnormality has been detected. When an abnormality is detected by comparing the offset current values ​​Iu, Iv, Iw with the abnormality detection threshold Ith, the abnormality detection unit 4 causes the power control unit 5 to perform a duty limiting process, which is a process of generating a limiting duty value that limits the duty value of the phase to be limited, which includes at least the phase in which the abnormality was detected, to a predetermined limiting threshold Duty_th or more so that the time during which the low-potential side switching elements 12u, 12v, 12w are in the off state is equal to or greater than the time required to detect the offset current values ​​Iu, Iv, Iw, and based on the limiting duty value.

[0055] When an abnormality is detected by comparing the offset current values ​​Iu, Iv, and Iw with the abnormality detection threshold Ith, the abnormality detection unit 4 causes the power control unit 5 to perform duty limiting processing for at least the phases to be limited, including the phase in which the abnormality was detected. As a result, the time during which the low-potential side switching elements 12u, 12v, and 12w are in the off state in the limited phase is equal to or longer than the time required to detect the offset current values ​​Iu, Iv, and Iw. Therefore, even when the output of the inverter circuit 1 is high, the offset current values ​​Iu, Iv, and Iw can be reliably detected in subsequent comparisons. Therefore, even when the output of the inverter circuit 1 is high, abnormalities can be detected accurately and without delay based on the offset current values ​​Iu, Iv, and Iw. Furthermore, during normal operation when no abnormality is detected, the power control unit 5 controls the multiple high-potential side switching elements 11u, 11v, and 11w and the multiple low-potential side switching elements 12u, 12v, and 12w based on the duty value without limiting the duty value to or above the limit threshold Duty_th. Therefore, it is possible to prevent a decrease in the output of the motor 3 during normal operation. As described above, it is possible to prevent a decrease in the output of the motor 3 during normal operation, and even when the output of the inverter circuit 1 is high, it is possible to accurately and without delay detect an abnormality based on the offset current values ​​Iu, Iv, and Iw.

[0056] Furthermore, since the abnormality detection unit 4 determines whether a failure has occurred based on the number of times an abnormality has been detected, it is possible to prevent erroneous determination of a failure due to noise or the like.

[0057] Furthermore, the abnormality detection unit 4 performs a failure determination for each failure determination period Te, and cancels the duty limiting process if no abnormality is detected consecutively in the failure determination for each failure determination period Te. This prevents the duty limiting process from being cancelled at an inappropriate time even if it is erroneously determined that there is no abnormality due to noise or the like, despite the occurrence of a failure.

[0058] Furthermore, in the duty limiting process, the power control unit 5 generates the limit duty value by matching the duty value of the phase to be limited that is smaller than the abnormality detection threshold Ith with the abnormality detection threshold Ith, thereby making it possible to suppress a decrease in the output of the motor 3 due to the duty limiting process.

[0059] The phase to be restricted is the phase in which an abnormality is detected by the abnormality detection unit 4. This makes it possible to more effectively suppress the reduction in the output of the motor 3.

[0060] 7 is a flowchart showing the flow of processing performed by the abnormality detection unit 4 according to a modification of the embodiment 1. In this modification, the current detection period Ti and the fault determination period Te are the same, and steps S103, S201, and S202 are omitted.

[0061] Specifically, if the absolute value |Ix| is equal to or less than the abnormality detection threshold Ith in step S102 (step S102: NO), it is determined that there is no abnormality in the x-phase, and the process proceeds to step S206. In step S206, the abnormality detection unit 4 sets the duty limiting process flag for the x-phase to "false" and outputs it to the power control unit 5. This causes the power control unit 5 to cancel (end) the duty limiting process. Furthermore, in step S207, the abnormality detection unit 4 resets the abnormality counter, and the process of this flowchart ends.

[0062] In step S102, if the absolute value |Ix| is greater than the abnormality detection threshold Ith (step S102: YES), it is determined that an abnormality exists in the x-phase (an abnormality in the x-phase is detected), and the process proceeds to step S104. In step S104, the abnormality detection unit 4 sets the duty limiting process flag for the x-phase to "true" and outputs it to the power control unit 5. This causes the power control unit 5 to execute the duty limiting process. After step S104, the process proceeds to step S203. In step S203, the abnormality detection unit 4 increments the abnormality counter by 1. Then, the process proceeds to step S204.

[0063] In step S204, the abnormality detection unit 4 determines whether the abnormality counter is equal to or greater than the fault determination threshold Nth. If the abnormality counter is smaller than the fault determination threshold Nth (step S204: NO), the flow chart ends. If the abnormality counter is equal to or greater than the fault determination threshold Nth (step S204: YES), in step S205, the abnormality detection unit 4 determines that a fault has occurred and outputs a fault determination flag to an external control device or the like, and the flow chart ends.

[0064] This modification can also achieve the same effects as those of the above-described embodiment 1. Furthermore, this modification can simplify the processing performed by the abnormality detection unit 4.

[0065] Embodiment 2 The motor control device 100 according to embodiment 1 can be applied to an electric power steering device for a vehicle. An electric power steering device 50 and a vehicle A according to embodiment 2 will be described below with reference to FIG. 8. Note that components having the same functions and actions as those in embodiment 1 are given the same reference numerals, and descriptions thereof will be omitted.

[0066] 8 , vehicle A includes an electric power steering device 50 and a notification unit 51. The electric power steering device 50 includes a motor 3, a motor control device 100, a torque sensor 52, a steering wheel 53, a steering shaft 54, a rack and pinion gear 55, wheels 56, and a reduction gear 57.

[0067] The steering wheel 53 is steered by the driver. A steering shaft 54 ​​is connected to the steering wheel 53 and a rack and pinion gear 55. The steering torque applied to the steering wheel 53 by the driver is transmitted to the rack and pinion gear 55 via the steering shaft 54. A rack included in the rack and pinion gear 55 is connected to wheels 56 via tie rods and knuckle arms. When the steering torque is transmitted to the rack, the tie rod pushes the knuckle arm of one wheel 56, and the tie rod pulls the knuckle arm of the other wheel 56. This causes the wheels 56 to turn.

[0068] The motor 3 functions as a driving force source that assists the steering of the steering wheel 53. Specifically, the motor 3 is connected to the steering shaft 54 ​​via a reduction gear 57. The motor torque generated by the motor 3 is transmitted to the steering shaft 54 ​​via the reduction gear 57, reducing the steering force applied by the driver when steering.

[0069] The torque sensor 52 is attached to the steering shaft 54. The torque sensor 52 detects the steering torque applied to the steering shaft 54 ​​when the driver turns the steering wheel 53. The torque sensor 52 outputs the detected steering torque to the motor control device 100.

[0070] In the motor control device 100, the duty value generator 7 receives the steering torque detected by the torque sensor 52 as an input and generates a duty value. The duty value generator 7 outputs the generated duty value to the power controller 5. The power controller 5 drives the inverter circuit 1 based on the duty value. As a result, a current is supplied from the inverter circuit 1 to the motor 3, and motor torque is generated.

[0071] The notification unit 51 is connected to the motor control device 100. When the abnormality detection unit 4 determines that a malfunction has occurred, it outputs a malfunction determination flag to the notification unit 51. The notification unit 51 notifies the driver of the occurrence of the malfunction. For example, the notification unit 51 may be provided with a display unit (not shown) that displays the occurrence of the malfunction on the display unit.

[0072] As described above, the electric power steering device 50 according to this embodiment includes the motor control device 100, the motor 3 that assists the steering of the steering wheel 53, and the torque sensor 52 that detects the steering torque caused by the steering of the steering wheel 53. The motor control device 100 controls the driving of the motor 3 in accordance with the steering torque detected by the torque sensor 52.

[0073] If a malfunction occurs in the electric power steering device 50 while the vehicle is running, the driver feels a strong sense of discomfort. Therefore, when a malfunction occurs, it is desirable to quickly transition to control corresponding to the abnormal state, and therefore it is desirable to accurately determine the malfunction in a short time. It is also desirable to suppress deterioration of the steering feel during malfunction determination. Because the electric power steering device 50 is provided with the motor control device 100, the malfunction detection unit 4 can detect the malfunction accurately and without delay, and it is possible to quickly and accurately determine the malfunction. Therefore, when a malfunction occurs, it is possible to quickly transition to control corresponding to the abnormal state, and it is possible to reduce the discomfort felt by the driver. It is also possible to suppress deterioration of the steering feel during malfunction determination.

[0074] Furthermore, the vehicle A according to this embodiment includes an electric power steering device 50 and a notification unit 51 that notifies the driver of the occurrence of a malfunction when the abnormality detection unit 4 determines that a malfunction has occurred. This allows the driver to be notified of the occurrence of a malfunction when a malfunction occurs.

[0075] Embodiment 3 Next, a motor control device according to embodiment 3 will be described. The basic configuration of the motor control device according to this embodiment is similar to that of the motor control device according to embodiment 1, so the following description will focus on the differences.

[0076] 9 and 10 are diagrams showing examples of duty values ​​input to the PWM generation unit 23 in the third embodiment. The horizontal axis in FIGS. 9 and 10 represents time, and the vertical axis represents duty value. The duty limiting unit 21 generates the limited duty value by performing an amplitude reduction process to reduce the amplitude of the duty value. Specifically, the duty limiting unit 21 generates the limited duty value by multiplying the amplitude of the duty value by a coefficient Duty_Lim such that the minimum value of the limited duty value is equal to or greater than the limit threshold Duty_th. The coefficient Duty_Lim is less than 1, for example, 0.9. When performing the amplitude reduction process, the limited duty value varies sinusoidally, similar to the duty value. Furthermore, the oscillation center of the limited duty value is maintained at 0.5.

[0077] Furthermore, the power control unit 5 does not instantaneously change the duty value. Instead, at the start of the duty limiting process, the coefficient Duty_Lim is gradually decreased from 1 to gradually decrease the amplitude of the duty value. At the end of the duty limiting process, the coefficient Duty_Lim is gradually increased to 1 to gradually increase the amplitude of the duty value. In the example of FIG. 9 , the duty limiting process is not performed from time 0 seconds to time T1 (near 0.57 seconds), and the duty limiting process is started at time T1. Furthermore, from time T1, the coefficient Duty_Lim is gradually decreased to gradually decrease the amplitude of the duty value. Furthermore, in the example of FIG. 10 , the duty limiting process is performed from time 0 seconds to time T2 (near 0.25 seconds), and release of the duty limiting process is started at time T2. Furthermore, from time T2, the coefficient Duty_Lim is gradually increased, thereby gradually increasing the amplitude of the Duty value.

[0078] As described above, in this embodiment, the power control unit 5 generates the limited duty value in the duty limiting process by multiplying the amplitude of the duty value of the phase to be limited by the coefficient Duty_Lim such that the minimum value of the limited duty value is equal to or greater than the limit threshold Duty_th. This ensures that the limited duty value maintains a waveform similar to that of the duty value. For example, if the duty value is sinusoidal, the limited duty value also becomes sinusoidal. Therefore, harmonic vibration components synchronized with the rotation of the motor 3 can be prevented from occurring in the motor torque generated based on the limited duty value. As a result, for example, when the motor control device 100 is used in an electric power steering device 50, deterioration of steering feel during fault detection can be effectively prevented.

[0079] Furthermore, the power control unit 5 gradually decreases the coefficient Duty_Lim from 1 when the duty limiting process starts, and gradually increases the coefficient Duty_Lim to 1 when the duty limiting process ends. This makes it possible to suppress fluctuations in motor torque when the duty limiting process starts and ends. As a result, when the motor control device 100 is used in an electric power steering device 50, for example, it is possible to more effectively suppress deterioration in steering feel during failure determination.

[0080] The rate at which the coefficient Duty_Lim (amplitude of the duty value) is gradually increased or decreased may be set by taking into consideration the time (fault-tolerant time interval) permissible from the viewpoint of functional safety or the amount of motor torque fluctuation permissible from the viewpoint of steering feel. Furthermore, if the minimum value of the duty value is equal to or greater than the limit threshold Duty_th even when the duty limiting process is not being executed, it is not necessary to limit the duty value to equal to or greater than the limit threshold Duty_th. Therefore, the minimum value of the duty value may be compared with a predetermined gradual increase / decrease start threshold, and if the minimum value of the duty value is smaller than the gradual increase / decrease start threshold, the coefficient Duty_Lim (amplitude of the duty value) may be gradually increased or decreased. In this case, the limit threshold Duty_th may be used as the gradual increase / decrease start threshold. Alternatively, in order to gradually increase or decrease the coefficient Duty_Lim (amplitude of the Duty value) more gently, a value (for example, 0.2) larger than the limit threshold Duty_th may be used as the gradual increase / decrease start threshold.

[0081] Embodiment 4 Next, a motor control device according to embodiment 4 will be described. The basic configuration of the motor control device according to this embodiment is similar to that of the motor control device according to embodiment 3, so the following description will focus on the differences.

[0082] FIG. 11 is a diagram showing an example of duty values ​​input to the PWM generation unit 23 in the fourth embodiment. The horizontal axis of FIG. 11 represents time, and the vertical axis represents duty value. In this embodiment, the duty values ​​are modulated by performing offset processing so that the maximum duty value among all phases matches a predetermined value. The duty limiting unit 21 limits the modulated duty value to a limit threshold Duty_th or greater. Also, in this embodiment, as in the third embodiment, the duty limiting unit 21 generates a limit duty value by multiplying the amplitude of the duty value by a coefficient Duty_Lim such that the minimum value of the limit duty value is equal to or greater than the limit threshold Duty_th. This suppresses a decrease in the voltage utilization rate compared to when a duty value that has not been modulated is used, thereby more effectively suppressing a decrease in the output of the motor 3 even when duty limiting processing is performed.

[0083] The technical scope of the present disclosure is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present disclosure.

[0084] For example, in the above embodiment, the phase in which the abnormality detection unit 4 detected an abnormality was defined as the phase to be limited. However, the phase to be limited may include all three phases. That is, when an abnormality is detected by comparing the offset current value with the abnormality detection threshold Ith, the power control unit 5 may generate a limit duty value that limits the duty values ​​of all phases to a predetermined limit threshold Duty_th or higher, and control the multiple high-potential side switching elements 11u, 11v, and 11w and the multiple low-potential side switching elements 12u, 12v, and 12w based on the limit duty value. In this case, torque ripple caused by an imbalance in the duty values ​​of the phases can be suppressed.

[0085] In addition, in the first embodiment, the duty limiting unit 21 generates the limited duty value by performing clipping processing to make a duty value smaller than the limit threshold Duty_th equal to the limit threshold Duty_th. In the third and fourth embodiments, the duty limiting unit 21 generates the limited duty value by performing amplitude reduction processing to reduce the amplitude of the duty value. However, the generation of the limited duty value by the duty limiting unit 21 is not limited to this. For example, the duty limiting unit 21 may generate the limited duty value by superimposing an offset voltage on the duty value of the phase to be limited so that the minimum value of the limited duty value is equal to or greater than the limit threshold Duty_th. In addition, the duty limiting unit 21 may limit the space vector modulated duty value to be equal to or greater than the limit threshold Duty_th.

[0086] In the above embodiment, the duty value generation unit 7 is described as being included in the motor control device 100. However, the duty value generation unit 7 may be provided outside the motor control device 100.

[0087] Furthermore, the abnormality detection unit 4 may record the abnormality detection as a log on a recording medium (not shown). In the above-described embodiment, if no abnormality is detected consecutively in the abnormality determination for each abnormality determination period Te, the abnormality detection unit 4 determines that there is no suspicion of a malfunction and cancels the duty limiting process. However, if an abnormality is detected again, albeit non-consecutively, after the first abnormality detection, it may be desirable to perform maintenance on the motor control device 100 and the motor 3. For example, during maintenance of the vehicle A, an operator may check the log and determine whether maintenance of the motor control device 100 and the motor 3 is required.

[0088] Furthermore, when the power control unit 5 is executing the duty limiting process, the abnormality detection unit 4 may notify a control unit higher than the motor control unit 100 that the duty limiting process is being executed. The higher-level control unit is, for example, a control unit that controls the vehicle A. This allows the higher-level control unit to execute control according to the duty limiting process while the duty limiting process is being executed.

[0089] The functions of the motor control device 100 described above are realized by a processor such as a central processing unit (CPU) executing a program stored in a program memory. Some or all of these functions may be realized by hardware such as a large-scale integration (LSI), an application-specific integrated circuit (ASIC), or a field-programmable gate array (FPGA), or may be realized by a combination of software and hardware.

[0090] The program for realizing the functions of the motor control device 100 described above is recorded, for example, on a computer-readable recording medium. The program recorded on this recording medium may then be loaded into a computer and executed to perform the processing of the motor control device 100 described above. Here, "loading a program recorded on a recording medium into a computer and executing it" includes installing the program on a computer. The term "computer" here includes the OS and hardware such as peripheral devices.

[0091] Furthermore, the term "computer" may include multiple computer devices connected via a network, including the Internet or communication lines such as WAN, LAN, and dedicated lines. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computers. Thus, the recording medium storing the program may be a non-transitory recording medium such as a CD-ROM.

[0092] The recording medium also includes an internal or external recording medium accessible from a distribution server for distributing the program. The program may be divided into multiple parts, each downloaded at a different time, and then combined in the motor control device 100. Each divided program may be distributed by a different distribution server.

[0093] The term "computer-readable recording medium" includes a storage medium that stores a program for a certain period of time, such as volatile memory (RAM) inside a computer that acts as a server or client when the program is transmitted over a network. The program may also be a program that realizes part of the functions described above. Furthermore, the program may be a so-called differential file (differential program). A differential program realizes the functions described above in combination with a program already stored on the computer.

[0094] In addition, the above-described embodiments and modifications may be combined as appropriate.

[0095] REFERENCE SIGNS LIST 100...motor control device 1...inverter circuit 3...motor 4...abnormality detection unit 5...power control unit 11u, 11v, 11w...high-potential side switching element 12u, 12v, 12w...low-potential side switching element 13u, 13v, 13w...current sensor 21...duty limiting unit 22...selecting unit 23...PWM generating unit 50...electric power steering device 52...torque sensor 53...steering wheel A...vehicle

Claims

1. An inverter circuit for supplying power to a motor having windings of multiple phases, comprising: a plurality of high-potential-side switching elements and a plurality of low-potential-side switching elements provided corresponding to each of the multiple phases; and a plurality of current sensors respectively connected to the plurality of low-potential-side switching elements. A power control unit configured to control the plurality of high-potential-side switching elements and the plurality of low-potential-side switching elements based on a Duty value. An abnormality detection unit configured to detect an abnormality by comparing, for each phase of the multiple phases, an offset current value detected using the current sensor when the low-potential-side switching element is in a non-conducting state with a first threshold value, and to determine a failure based on the number of times the abnormality is detected. The inverter circuit is provided with the above components. When an abnormality is detected by comparing the offset current value with the first threshold value, the abnormality detection unit causes the power control unit to generate a restricted Duty value for a restricted target phase including at least the phase in which the abnormality is detected among the multiple phases, such that the time during which the low-potential-side switching element is in a non-conducting state is equal to or longer than the time required for detecting the offset current value, and to perform a Duty restriction process of controlling the high-potential-side switching element and the low-potential-side switching element based on the restricted Duty value. A motor control device.

2. The abnormality detection unit determines a failure for each failure determination period, and cancels the Duty restriction process when the abnormality is not continuously detected in the failure determination for each failure determination period. The motor control device according to Claim 1.

3. In the Duty restriction process, the power control unit generates the restricted Duty value by matching the Duty value of the restricted target phase that is smaller than the lower limit value with the lower limit value. The motor control device according to Claim 1.

4. In the Duty restriction process, the power control unit generates the restricted Duty value by multiplying a coefficient such that the minimum value of the restricted Duty value is equal to or greater than the lower limit value by the amplitude of the Duty value of the restricted target phase. The motor control device according to Claim 1.

5. The motor control device according to claim 4, wherein the power control unit gradually decreases the coefficient from 1 at the start of the Duty limit process and gradually increases the coefficient to 1 at the end of the Duty limit process.

6. The motor control device according to claim 1, wherein the phase to be restricted is the phase in which the abnormality is detected.

7. The motor control device according to claim 1, wherein the phase to be restricted includes all of the plurality of phases.

8. The motor control device according to any one of claims 1 to 7, the motor that assists in steering the steering wheel, a torque sensor that detects a steering torque caused by steering of the steering wheel, comprising: the motor control device controls driving of the motor according to the steering torque detected by the torque sensor. An electric power steering device.

9. The electric power steering device according to claim 8, a notification unit that notifies of the occurrence of a failure when the abnormality detection unit determines a failure, a vehicle comprising.