Motor control device, electric power steering system, 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

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

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

[0005] In view of the above circumstances, this disclosure aims to provide a motor control device, an electric power steering device, and a vehicle that can prevent a decrease in motor output during normal operation and can accurately and without delay detect abnormalities based on the offset current value even when the output of the inverter circuit is high. [Means for solving the problem]

[0006] One embodiment of a motor control device according to this disclosure is an inverter circuit that supplies power to a motor having multiple phase windings, comprising: a plurality of high-potential-side switching elements and a plurality of low-potential-side switching elements provided corresponding to each phase of the plurality of phases; a plurality of current sensors connected to each of the plurality of low-potential-side switching elements; 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 cycle; and for each of the plurality of phases, an abnormality is detected by comparing an offset current value detected using the current sensor when the low-potential-side switching element is in a non-conductive state with a first threshold value. The system includes an abnormality detection unit that outputs a signal and determines a fault based on the number of times the abnormality has been detected. 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 generate a limited duty cycle value for the restricted phase, which includes at least the phase in which the abnormality was detected, such that the time the low-potential side switching element is in a non-conductive state is equal to or greater than the time required to detect the offset current value. The power control unit then performs a duty cycle limiting process, which controls the high-potential side switching element and the low-potential side switching element based on the limited duty cycle value.

[0007] One embodiment of the electric power steering system according to this disclosure comprises a motor control device, a motor that assists in steering the steering wheel, and a torque sensor that detects the steering torque caused by steering the steering wheel, wherein the motor control device controls the drive of the motor in accordance with the steering torque detected by the torque sensor.

[0008] One embodiment of the vehicle relating to this disclosure comprises the electric power steering device and a notification unit that notifies of the occurrence of a malfunction when the abnormality detection unit confirms a malfunction. [Effects of the Invention]

[0009] According to this 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, abnormalities based on the offset current value can be detected accurately and without delay. [Brief explanation of the drawing]

[0010] [Figure 1] This is an overall configuration diagram of the motor control device according to Embodiment 1. [Figure 2] This is a block diagram of the power control unit according to Embodiment 1. [Figure 3] This figure illustrates the principle of switching signal generation in the PWM generation unit according to Embodiment 1. [Figure 4] This figure shows an example of a duty cycle value input to the power control unit according to Embodiment 1. [Figure 5] This figure shows an example of a duty cycle value input to the PWM generation unit according to Embodiment 1. [Figure 6] This flowchart shows the processing flow performed by the abnormality detection unit according to Embodiment 1. [Figure 7] This flowchart shows the processing flow performed by the abnormality detection unit according to a modified example of Embodiment 1. [Figure 8] This is a schematic diagram of the electric power steering system according to Embodiment 2. [Figure 9] This figure shows an example of a duty cycle value input to the PWM generation unit according to Embodiment 3. [Figure 10] This figure shows an example of a duty cycle value input to the PWM generation unit according to Embodiment 3. [Figure 11] This figure shows an example of a duty cycle value input to the PWM generation unit according to Embodiment 4. [Modes for carrying out the invention]

[0011] Embodiments of this disclosure will be described below with reference to the drawings. However, the scope of this disclosure is not limited to the embodiments described below and can be modified at will within the scope of the technical idea of ​​this disclosure.

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

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

[0014] The inverter circuit 1 includes high-potential-side switching elements 11u, 11v, 11w, low-potential-side switching elements 12u, 12v, 12w, and current sensors 13u, 13v, 13w. The inverter circuit 1 also has a power 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, 11w may be simply referred to as "high-potential-side switching element 11". Similarly, the low-potential-side switching elements 12u, 12v, 12w may be simply referred to as "low-potential-side switching element 12". The current sensors 13u, 13v, 13w may be simply referred to as "current sensor 13".

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

[0016] The high-potential side switching elements 11u, 11v, and 11w are respectively input with switching signals Gup, Gvp, and Gwp output from the power control unit 5. The low-potential side switching elements 12u, 12v, and 12w are respectively input with switching signals Gun, Gvn, and Gwn output from the power control unit 5. 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, 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 become an on state (conducting state) or an off state (non-conducting state) according to 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 becomes an on state, and when the switching signal Gup is an "off command (=0)", the high-potential side switching element 11u becomes an off state. The same applies to the other switching elements 11v, 11w, 12u, 12v, and 12w. Thus, by switching the on state and the off state of the switching elements 11u, 11v, 11w, 12u, 12v, and 12w with the switching signals Gup, Gvp, Gwp, Gun, Gvn, and Gwn, the inverter circuit 1 causes current to flow through the three-phase windings of the motor 3. Thereby, motor torque is generated.

[0017] The high-potential side switching elements 11u, 11v, 11w and the low-potential side switching elements 12u, 12v, 12w are, for example, FETs (Field Effect Transistors). Note that the switching elements 11u, 11v, 11w, 12u, 12v, 12w may be any device 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, 12w may be thyristors or bipolar transistors, etc.

[0018] The current sensors 13u, 13v, and 13w are positioned between the low-potential switching elements 12u, 12v, and 12w and the ground line L2, respectively. The current sensors 13u, 13v, and 13w are connected in series with the low-potential switching elements 12u, 12v, and 12w, respectively. The current sensors 13u, 13v, and 13w detect the current values ​​flowing through the low-potential switching elements 12u, 12v, and 12w, respectively. The current sensors 13u, 13v, and 13w are, for example, shunt resistors. The current sensors 13u, 13v, and 13w only need to be able to detect the current values ​​flowing through the low-potential switching elements 12u, 12v, and 12w. For example, the current sensors 13u, 13v, and 13w may be CTs (Current Transformers) or Hall elements, etc.

[0019] The current values ​​detected by the current sensors 13u, 13v, and 13w are input to the current value acquisition unit 6. The current value acquisition unit 6 has a sample-and-hold circuit. The current value acquisition 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 sampling timings, and outputs the acquired offset current values ​​Iu, Iv, and Iw to the abnormality detection unit 4 or the like. The offset current value Iu is the U-phase current value detected using the current sensor 13u when no current flows through the low-potential 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 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 switching element 12w (current sensor 13w). The sampling timing is a timing that occurs at each predetermined current detection period Ti. The sampling timing is set to the timing when the low-potential switching elements 12u, 12v, and 12w are in the off state. The offset current values ​​Iu, Iv, and Iw are used, for example, to calibrate the current sensor 13 so that the value of the current sensor 13 becomes 0 (A) when no current flows. 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 abnormalities in the power supply path that supplies power to the motor 3 based on the offset current values ​​Iu, Iv, and Iw detected using the current sensors 13u, 13v, and 13w. The abnormality detection unit 4 also determines a failure based on the number of times an abnormality has been detected. Examples of the causes of the above failure include short-circuit failures of the low-potential switching elements 12u, 12v, and 12w, failures of the current sensors 13u, 13v, and 13w, and failures of the current value acquisition unit 6.

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

[0022] If the power supply path that supplies power to the motor 3 is functioning correctly, the offset current value Ix for 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 less than or equal to 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 mentioned above, if the power supply path is functioning correctly, the offset current value Ix will be "0", so ideally the abnormality detection threshold Ith should be set to "0". However, since the current sensor 13 may have errors in detecting the current value, the abnormality detection threshold Ith is set to a value slightly greater than "0".

[0023] The anomaly detection unit 4 outputs a duty cycle limiting processing flag to the power control unit 5 according to the detection result. Specifically, the anomaly detection unit 4 outputs the duty cycle limiting processing flag for the phase in which the anomaly was detected as "true" to the power control unit 5.

[0024] Furthermore, to prevent misjudgments, the abnormality detection unit 4 does not confirm a failure in a phase where an abnormality is detected based on a single abnormality detection, but rather confirms the failure after multiple abnormality detections. Details of the failure determination will be described later. When the abnormality detection unit 4 confirms a failure, it outputs a failure confirmation flag to an external control device or the like. This triggers processes such as notifying the user of the motor 3 of the occurrence of the failure and stopping the motor 3 according to a predetermined process.

[0025] The Duty Value Generation Unit 7 receives control commands from an external source. Based on the control commands, the Duty Value Generation Unit 7 generates a Duty Value. The Duty Value Generation Unit 7 outputs the Duty Value to the Power Control Unit 5. The Duty Value includes the Duty Value for the U-phase, the Duty Value for the V-phase, and the Duty Value for the W-phase. The Duty Value for the U-phase corresponds to the voltage to be applied to the U-phase winding of the motor 3. The Duty Value for the U-phase indicates the ratio of the time during which the high-potential side switching element 11u of the U-phase is energized relative to one period of the signal (the carrier period Tc of the carrier triangular wave C described later), and takes a range of 0 to 1 (0% to 100%). The Duty Value for the V-phase corresponds to the voltage to be applied to the V-phase winding of the motor 3. The Duty Value for the V-phase indicates the ratio of the time during which the high-potential side switching element 11v of the V-phase is energized relative to one period of the signal, and takes a range of 0 to 1 (0% to 100%). The W-phase duty cycle corresponds to the voltage to be applied to the W-phase winding of motor 3. The W-phase duty cycle indicates the ratio of the time during which the high-potential side switching element 11w of the W-phase is energized relative to one period of the signal, and takes a range of 0 to 1 (0% to 100%).

[0026] The power control unit 5 receives a duty cycle value from the duty cycle value generation unit 7. The power control unit 5 also receives a duty cycle limit processing flag from the abnormality detection unit 4. Based on the duty cycle value and the duty cycle limit processing flag, the power control unit 5 drives the inverter circuit 1.

[0027] Figure 2 is a block diagram of the power control unit 5. As shown in Figure 2, the power control unit 5 includes a duty limiting unit 21, a selection unit 22, and a PWM generation unit 23.

[0028] The Duty Limit Unit 21 receives Duty values ​​from the Duty Value Generation Unit 7. The Duty Limit Unit 21 generates a limited Duty value that limits the Duty values ​​input from the Duty Value Generation Unit 7 to a predetermined limit threshold Duty_th (lower limit). In this embodiment, the Duty Limit Unit 21 generates the limited Duty value by performing a clipping process to make Duty values ​​smaller than the limit threshold Duty_th match the limit threshold Duty_th. The Duty Limit Unit 21 outputs the limited Duty value to the Selection Unit 22.

[0029] The selection unit 22 receives duty values ​​from the duty value generation unit 7. The selection unit 22 receives limited duty values ​​from the duty limiting unit 21. The selection unit 22 receives a duty limiting processing flag from the anomaly detection unit 4. Based on the duty limiting processing flag, the selection unit 22 selects the duty values ​​to output to the PWM generation unit 23. Specifically, for restricted phases that include at least one phase in which the duty limiting processing flag indicates "true", the selection unit 22 outputs the limited duty values ​​generated by the duty limiting unit 21 to the PWM generation unit 23. For phases other than the restricted phases, the selection unit 22 outputs the duty values ​​output from the duty value generation unit 7 (i.e., duty values ​​that are not limited to the limit threshold Duty_th) to the PWM generation unit 23. In this embodiment, the restricted phases are those in which the duty limiting processing flag indicates "true". In other words, for example, if the Duty limit processing flag for the U phase indicates "true" and the Duty limit processing flags for the V phase and W phase indicate "false", the selection unit 22 outputs the limited Duty value for the U phase generated by the Duty limiting unit 21, and the Duty values ​​for the V phase and W phase output from the Duty value generation unit 7, to the PWM generation unit 23. In the following description, the limited Duty value or Duty value output from the selection unit 22 to the PWM generation unit 23 may be collectively referred to simply as "Duty value".

[0030] Figure 4 shows an example of a duty cycle input from the duty cycle generation unit 7 to the power control unit 5. In Figure 4, the horizontal axis represents time, and the vertical axis represents the duty cycle. In the illustrated example, the duty cycle of the U phase is denoted as DutyU, the duty cycle of the V phase as DutyV, and the duty cycle of the W phase as DutyW. As shown in Figure 4, in this embodiment, the duty cycle of each phase changes in a sinusoidal manner.

[0031] Figure 5 shows an example of a duty cycle input to the PWM generation unit 23 when the phase to be limited is the U phase. In Figure 5, the horizontal axis represents time, and the vertical axis represents the duty cycle. In the example shown, the limited duty cycle for the U phase is shown as DutyU_Limit.

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

[0033] As described above, when the abnormality detection unit 4 inputs a Duty limit processing flag indicating "true", the power control unit 5 generates a limited Duty value for the restricted phases that include at least the phase for which the Duty limit processing flag indicating "true" was input, by limiting the Duty value output from the Duty value generation unit 7 to a limit threshold Duty_th or higher, and performs Duty limit processing, which controls the high-potential side switching elements 11u, 11v, 11w and the low-potential side switching elements 12u, 12v, 12w based on the limited Duty value.

[0034] The power control unit 5 may perform duty limit processing by changing the processing and threshold values ​​in the duty limit unit 21 according to the duty limit processing flag, without using the selection unit 22. For example, for the phase to be limited, the duty limit unit 21 generates a limited duty value that limits the duty value to a limit threshold Duty_th or higher and outputs it to the PWM generation unit 23. For phases other than the phase to be limited, the duty limit 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 as is to the PWM generation unit 23. The PWM generation 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 value input from the duty limit unit 21.

[0035] The method by which the PWM generation unit 23 generates switching signals will be explained using Figure 3. In the following explanation, the U-phase will be described as representative of the three phases: U-phase, V-phase, and W-phase. Therefore, the following explanation also applies to the V-phase and W-phase.

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

[0037] Specifically, the PWM generation unit 23 sets the high-potential switching signal Gup to "1" as an ON command and the low-potential switching signal Gun to "0" as an OFF command when the Duty Value of the U-phase is greater than the carrier triangular wave C. In other words, when the Duty Value of the U-phase is greater than the carrier triangular wave C, the high-potential switching element 11u of the U-phase is turned ON and the low-potential switching element 12u of the U-phase is turned OFF. The PWM generation unit 23 sets the high-potential switching signal Gup to "0" as an OFF command and the low-potential switching signal Gun to "1" as an ON command when the Duty Value of the U-phase is less than the carrier triangular wave C. In other words, when the Duty Value of the U-phase is less than the carrier triangular wave C, the high-potential switching element 11u of the U-phase is turned OFF and the low-potential switching element 12u of the U-phase is turned ON. More precisely, in order to prevent the high-potential switching element 11u and the low-potential switching element 12u from being turned on simultaneously, a dead time is provided in which both the high-potential switching element 11u and the low-potential switching element 12u are turned off for a very short period of time.

[0038] The reason for implementing duty cycle limits is explained below with reference to Figures 4 and 5.

[0039] As described above, the duty cycle includes the duty cycles for the U-phase, V-phase, and W-phase. The larger the voltage difference between phases, the stronger the force trying to flow current through the three-phase windings of the motor 3. Therefore, when the output of the inverter circuit 1 is large, the amplitude of the duty cycle increases. When a switching signal indicating a low duty cycle is input to the inverter circuit 1, the time that the low-potential side switching element 12 of the phase to which this switching signal is input is ON increases (i.e., the time that the low-potential side switching element 12 is OFF decreases). Here, the time required to detect the offset current value using the current sensor 13 is called the current detection time. If the time that the low-potential side switching element 12 is OFF is shorter than the current detection time, the current sensor 13 cannot detect the offset current value. In this case, the abnormality detection unit 4 cannot detect an abnormality based on the offset current value. The abnormality detection unit 4 confirms a fault after detecting an abnormality multiple times. To determine such a fault, it is necessary to continuously monitor the offset current value of the phase in which the abnormality was detected during the fault determination process. In the example in Figure 4, for example, during the period from approximately 0.15 seconds to 0.3 seconds, the duty cycle values ​​of the three phases are greater than or equal to the limit threshold Duty_th. In this case, there is an electrical angle during which the offset current value can be detected, so if the period during fault detection is short, it is possible to detect the abnormality. However, as the rotational speed of motor 3 increases, the period during which the electrical angle during which the offset current value can be detected becomes shorter, and furthermore, the back electromotive force of motor 3 acts, causing the amplitude of the duty cycle value to tend to increase. Therefore, in this case, it becomes difficult to always detect the offset current value of the phase in which an abnormality has been detected during the period during fault detection.

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

[0041] The power control unit 5 performs duty cycle limiting processing, ensuring that the time during which the low-potential side switching element 12 is in the off state for the phase to be limited is greater than or equal to the current detection time. This allows the current sensor 13 to reliably acquire the offset current value. In other words, when the duty cycle limiting processing is executed, abnormalities based on the offset current value can be reliably detected for the phase to be limited. If the duty cycle value is greater than or equal to the limiting threshold Duty_th, the low-potential side switching elements 12u, 12v, and 12w of all phases will be in the off state around the time when the carrier triangular wave C becomes 0. Therefore, the sampling timing in the current value acquisition unit 6 is set to the above time.

[0042] Figure 6 is a flowchart showing the processing flow performed by the anomaly detection unit 4. The anomaly detection process by the anomaly detection unit 4 is performed, for example, at each 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 anomaly detection process by the anomaly detection unit 4 may also be performed at periods that are integer multiples of the current detection period Ti. Furthermore, the anomaly detection process by the anomaly detection unit 4 is performed in parallel for each of the U, V, and W phases. In the following, we will explain the case where the anomaly detection process is performed in any one of the three phases, which is the "x phase," as an example.

[0043] In step S101, the anomaly detection unit 4 obtains Duty_x, which is the duty cycle 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 terminates.

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

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

[0046] If the absolute value |Ix| is greater than the anomaly detection threshold Ith (step S102: YES), it is determined that there is an anomaly in the x-phase (an anomaly in the x-phase is detected), and the process proceeds to step S103. In step S103, the anomaly detection unit 4 increments the free-run counter (FRC), which indicates the number of times an anomaly has been detected, by 1. After step S103, the process proceeds to step S104. In step S104, the anomaly detection unit 4 sets the duty limit processing flag for the x-phase to "true" and outputs it to the power control unit 5. As a result, the power control unit 5 executes the duty limit processing. After step S104, the process proceeds to step S201. If the power control unit 5 has already executed the duty limit processing, the result of the determination in step S101 will always be "YES", and the process will always proceed to step S102 after step S101.

[0047] Step S201 determines whether or not it is time to execute the fault detection routine. Specifically, in step S201, the anomaly detection unit 4 determines whether or not the current period is a pre-set fault detection period Te. The fault detection period Te is an integer multiple (for example, several times to tens of times) of the current detection period Ti. If the current period is not the fault detection period Te (step S201: NO), this flowchart terminates.

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

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

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

[0051] If the abnormality counter is less than the failure confirmation threshold Nth (step S204: NO), the process proceeds to step S208.

[0052] If the free-run counter (FRC) and the free-run counter (FRCpast) at the time of the previous fault detection routine execution are the same (step S202: YES), then step S103 has not been executed since the previous fault detection routine execution. In other words, since the previous fault detection routine execution, the state in step S102 in which the absolute value |Ix| is determined to be less than or equal to the abnormality detection threshold Ith has been maintained, and no abnormalities have been detected consecutively in the x-phase. In this case, assuming there is no suspicion of a fault, in step S206, the abnormality detection unit 4 sets the duty limit processing flag for the x-phase to "false" and outputs it to the power control unit 5. As a result, the power control unit 5 releases (terminates) the duty limit processing. Also, in step S207, the abnormality detection unit 4 resets the abnormality counter. After that, the process proceeds to step S208.

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

[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 multiple phase windings, a power control unit 5, and an abnormality detection unit 4. The inverter circuit 1 has a plurality of high-potential switching elements 11u, 11v, 11w and a plurality of low-potential switching elements 12u, 12v, 12w, which are provided corresponding to each phase of the plurality of phases, and a plurality of current sensors 13u, 13v, 13w, which are connected to the plurality of low-potential switching elements 12u, 12v, 12w, respectively. The power control unit 5 controls the plurality of high-potential switching elements 11u, 11v, 11w and the plurality of low-potential switching elements 12u, 12v, 12w based on the duty cycle value. The abnormality detection unit 4 detects abnormalities by comparing the offset current values ​​Iu, Iv, and Iw detected using the current sensors 13u, 13v, and 13w when the low-potential side switching elements 12u, 12v, and 12w are in the off state for each phase of the multiple phases, with the abnormality detection threshold Ith, and also determines a fault based on the number of times an abnormality has been detected. 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 instructs the power control unit 5 to generate a limited duty cycle value for the restricted phase, which includes at least the phase in which the abnormality was detected, such that the time during which the low-potential switching elements 12u, 12v, and 12w are in the off state is equal to or greater than the time required to detect the offset current values ​​Iu, Iv, and Iw. Based on this limited duty cycle value, the power control unit 5 performs a duty cycle limiting process, which controls the high-potential switching elements 11u, 11v, and 11w and the low-potential switching elements 12u, 12v, and 12w.

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

[0056] Furthermore, since the abnormality detection unit 4 determines a fault based on the number of times an abnormality has been detected, it can suppress false fault detections caused by noise and other factors.

[0057] Furthermore, the abnormality detection unit 4 performs a fault determination for each fault determination cycle Te, and if no abnormalities are detected consecutively in the fault determination for each fault determination cycle Te, it releases the duty cycle limiting process. This prevents the duty cycle limiting process from being released at an inappropriate time, even if a malfunction occurs but is mistakenly detected as normal due to noise or other factors.

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

[0059] Furthermore, the restricted phases are those in which an abnormality has been detected by the abnormality detection unit 4. This makes it possible to more effectively suppress the decrease in the output of motor 3.

[0060] A modified example of Embodiment 1. Figure 7 is a flowchart showing the processing flow performed by the abnormality detection unit 4 in a modified example of Embodiment 1. In this modified example, the current detection period Ti and the fault determination period Te are the same, and steps S103, S201, and S202 are omitted.

[0061] Specifically, in step S102, if the absolute value |Ix| is less than or equal to 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 S206. In step S206, the abnormality detection unit 4 sets the duty cycle limit processing flag for the x-phase to "false" and outputs it to the power control unit 5. As a result, the power control unit 5 cancels (terminates) the duty cycle limit processing. In step S207, the abnormality detection unit 4 resets the abnormality counter and terminates this flowchart.

[0062] In step S102, if the absolute value |Ix| is greater than the anomaly detection threshold Ith (step S102: YES), it is determined that there is an anomaly in the x-phase (an anomaly in the x-phase is detected), and the process proceeds to step S104. In step S104, the anomaly detection unit 4 sets the duty limit processing flag for the x-phase to "true" and outputs it to the power control unit 5. As a result, the power control unit 5 executes the duty limit processing. After step S104, the process proceeds to step S203. In step S203, the anomaly detection unit 4 increments the anomaly counter by 1. After that, the process proceeds to step S204.

[0063] In step S204, the abnormality detection unit 4 determines whether the abnormality counter is greater than or equal to the failure confirmation threshold Nth. If the abnormality counter is less than the failure confirmation threshold Nth (step S204: NO), this flowchart ends. If the abnormality counter is greater than or equal to the failure confirmation threshold Nth (step S204: YES), in step S205, the abnormality detection unit 4 confirms the failure, outputs a failure confirmation flag to an external control device, and ends this flowchart.

[0064] In this modified example, the same effects as in Embodiment 1 described above can be achieved. Furthermore, in this modified example, the processing performed by the anomaly detection unit 4 can be simplified.

[0065] Embodiment 2. The motor control device 100 according to Embodiment 1 can be applied to an electric power steering system for a vehicle. Hereinafter, the electric power steering system 50 and vehicle A according to Embodiment 2 will be described with reference to Figure 8. Components having the same functions and operations as those in Embodiment 1 are denoted by the same reference numerals and their descriptions are omitted.

[0066] As shown in Figure 8, vehicle A includes an electric power steering system 50 and a notification unit 51. The electric power steering system 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, a wheel 56, and a reduction gear 57.

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

[0068] Motor 3 functions as a driving force source that assists in steering the steering wheel 53. Specifically, motor 3 is connected to the steering shaft 54 ​​via a reduction gear 57. The motor torque generated by motor 3 is transmitted to the steering shaft 54 ​​via the reduction gear 57, reducing the steering force applied by the driver during 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 steers 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 cycle generation unit 7 receives the steering torque detected by the torque sensor 52 as input and generates a duty cycle value. The duty cycle generation unit 7 outputs the generated duty cycle value to the power control unit 5. The power control unit 5 drives the inverter circuit 1 based on the duty cycle value. As a result, 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 confirms a fault, it outputs a fault confirmation flag to the notification unit 51. The notification unit 51 notifies the driver of the occurrence of the fault. For example, the notification unit 51 may include a display unit (not shown) and display the occurrence of the fault on the display unit.

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

[0073] In the electric power steering system 50, if a malfunction occurs while the vehicle is in motion, the driver will experience a significant sense of discomfort. Therefore, it is desirable to quickly transition to a control system that corresponds to the abnormal condition when a malfunction occurs, and for this reason, it is desirable to accurately determine the malfunction in a short amount of time. It is also desirable to suppress the deterioration of steering feel during the malfunction determination process. Since the electric power steering system 50 is equipped with a motor control device 100, the abnormality detection unit 4 can detect abnormalities accurately and without delay, allowing for quick and accurate fault identification. Therefore, when a fault occurs, the system can quickly transition to control corresponding to the abnormal condition, minimizing the discomfort felt by the driver. Furthermore, deterioration of the steering feel during fault detection can be suppressed.

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

[0075] Embodiment 3. Next, a motor control device according to Embodiment 3 will be described. Since the basic configuration of the motor control device according to this embodiment is the same as that of the motor control device of Embodiment 1, the differences will be the main points to be explained.

[0076] Figures 9 and 10 show examples of duty cycle values ​​input to the PWM generation unit 23 in Embodiment 3. In Figures 9 and 10, the horizontal axis represents time, and the vertical axis represents the duty cycle value. The duty limiting unit 21 generates a limited duty cycle value by performing an amplitude reduction process to reduce the amplitude of the duty cycle value. Specifically, the duty limiting unit 21 generates a limited duty cycle value by multiplying the amplitude of the duty cycle value by a coefficient Duty_Lim such that the minimum value of the limited duty cycle value is greater than or equal to the limit threshold Duty_th. The coefficient Duty_Lim is less than 1, for example, 0.9. When the amplitude reduction process is performed, the limited duty cycle value changes sinusoidally, similar to the duty cycle value. Also, the oscillation center of the limited duty cycle value is maintained at 0.5.

[0077] Furthermore, the power control unit 5 does not change the Duty value instantaneously. Instead, at the start of the Duty limiting process, it gradually decreases the amplitude of the Duty value by gradually decreasing the coefficient Duty_Lim from 1, and at the end of the Duty limiting process, it gradually increases the amplitude of the Duty value by gradually increasing the coefficient Duty_Lim to 1. In the example in Figure 9, duty cycle limiting is not performed from time 0 seconds to time T1 (around 0.57 seconds), and starts at time T1. Furthermore, the amplitude of the duty cycle value is gradually decreased by gradually decreasing the coefficient Duty_Lim from time T1. In the example in Figure 10, duty cycle limiting is performed from time 0 seconds to time T2 (around 0.25 seconds), and starts to be released at time T2. Furthermore, the amplitude of the duty cycle value is gradually increased by gradually increasing the coefficient Duty_Lim from time T2.

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

[0079] Furthermore, the power control unit 5 gradually decreases the coefficient Duty_Lim from 1 at the start of the duty limiting process, and gradually increases the coefficient Duty_Lim back to 1 at the end of the duty limiting process. This makes it possible to suppress fluctuations in motor torque at the start and end of the duty cycle limiting process. As a result, for example, when the motor control device 100 is used in an electric power steering system 50, the deterioration of steering feel during fault detection can be more effectively suppressed.

[0080] Furthermore, the rate at which the coefficient Duty_Lim (amplitude of the Duty value) is gradually increased or decreased may be set by considering the allowable time from a functional safety perspective (fault-tolerant time interval) or the allowable amount of motor torque fluctuation from a steering feel perspective, and setting the amount of change in the coefficient Duty_Lim (amplitude of the Duty value) per unit of time. Also, even when Duty limiting processing is not being performed, if the minimum value of the Duty value is greater than or equal to the limit threshold Duty_th, it is not necessary to limit the Duty value to the limit threshold Duty_th or greater. For this reason, the minimum value of the Duty value may be compared with a predetermined threshold for starting the gradual increase or decrease, and the gradual increase or decrease of the coefficient Duty_Lim (amplitude of the Duty value) may be started if the minimum value of the Duty value is less than the threshold for starting the gradual increase or decrease. In this case, the limit threshold Duty_th may be used as the threshold for starting the gradual increase or decrease. Alternatively, to make the coefficient Duty_Lim (amplitude of the duty cycle) increase or decrease more gradually, a value larger than the limit threshold Duty_th (for example, 0.2) may be used as the threshold for starting the increase or decrease.

[0081] Embodiment 4. Next, a motor control device according to Embodiment 4 will be described. Since the basic configuration of the motor control device according to this embodiment is the same as that of the motor control device of Embodiment 3, the differences will be explained in detail.

[0082] Figure 11 shows an example of a Duty Value input to the PWM generation unit 23 in Embodiment 4. The horizontal axis of Figure 11 represents time, and the vertical axis represents the Duty Value. In this embodiment, as a modulation method for the Duty Value, modulation is performed by applying an offset process so that the maximum value among the Duty Values ​​of all phases matches a predetermined value. The Duty Limit Unit 21 limits the Duty Value, which has been modulated as described above, to a limit threshold Duty_th or higher. In this embodiment, similar to Embodiment 3, the Duty Limit Unit 21 generates a 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. As a result, the decrease in voltage utilization rate can be suppressed compared to the case where the Duty Value without the above modulation is used, and the decrease in the output of the motor 3 can be suppressed more effectively even when duty limit processing is performed.

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

[0084] For example, in the above embodiment, the phase in which an abnormality was detected by the abnormality detection unit 4 was designated as the restricted phase. However, the restricted phase 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 restricted duty cycle value that limits the duty cycle values ​​of all phases to a predetermined restriction threshold Duty_th or higher, and control multiple high-potential switching elements 11u, 11v, 11w and multiple low-potential switching elements 12u, 12v, 12w based on the restricted duty cycle value. In this case, torque ripple caused by an imbalance in the duty cycle values ​​of each phase can be suppressed.

[0085] Furthermore, in Embodiment 1, the Duty limiting unit 21 generates a limited Duty value by performing a clipping process to make Duty values ​​smaller than the limit threshold Duty_th match the limit threshold Duty_th. In Embodiments 3 and 4, the Duty limiting unit 21 generates a limited Duty value by performing an amplitude reduction process 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 these. For example, the Duty limiting unit 21 may generate a 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 greater than or equal to the limit threshold Duty_th. Furthermore, the Duty limiting unit 21 may limit the Duty value, which has undergone spatial vector modulation, to a limit threshold Duty_th or higher.

[0086] In the above-described embodiment, the duty cycle generation unit 7 was explained to be included in the motor control device 100. However, the duty cycle generation unit 7 may be provided outside the motor control device 100.

[0087] Furthermore, the abnormality detection unit 4 may record the detection of abnormalities as a log on a recording medium (not shown). In the above embodiment, if no abnormalities are detected consecutively in the fault determination for each fault determination cycle Te, the abnormality detection unit 4 determines that there is no suspicion of a fault and releases the duty cycle limit processing. However, if an abnormality is detected again, albeit not 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 vehicle A, the worker may check the log and determine whether maintenance of the motor control device 100 and the motor 3 is necessary.

[0088] Furthermore, when the power control unit 5 is performing duty cycle limiting processing, the abnormality detection unit 4 may notify a control unit higher than the motor control unit 100 that duty cycle limiting processing is being performed. The higher-level control unit is, for example, the control unit that controls vehicle A. This allows the higher-level control unit to perform control corresponding to the duty cycle limiting processing while it is being performed.

[0089] The functions of the motor control device 100 described above are realized, for example, by a processor such as a CPU (Central Processing Unit) executing a program stored in program memory. Some or all of these functions may be realized by hardware such as an LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), or FPGA (Field-Programmable Gate Array), or by the cooperation 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 processing in the motor control device 100 may then be performed by loading the program recorded on this recording medium into a computer and executing it. Here, "loading the program recorded on the recording medium into a computer and executing it" includes installing the program on the computer. Here, "computer" includes hardware such as the OS and peripheral devices.

[0091] Furthermore, "computer" may include multiple computer devices connected via a network including the Internet or communication lines such as WANs, LANs, and dedicated lines. Also, "computer-readable recording media" refers to portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computers. Thus, the recording media on which the program is stored may also be non-transient recording media such as CD-ROMs.

[0092] Furthermore, the recording medium also includes internal or external recording media accessible from the distribution server for distributing the program. The program may be divided into multiple parts, downloaded at different times, and then combined by the motor control device 100. Also, different distribution servers may be used to distribute each of the divided programs.

[0093] "Computer-readable recording medium" includes volatile memory (RAM) inside a computer that acts as a server or client when a program is transmitted over a network, which holds the program for a certain period of time. Furthermore, the program may be for the purpose of implementing some of the functions described above. In addition, the program may be a so-called differential file (differential program). A differential program implements the functions described above in combination with a program already recorded on the computer.

[0094] Other embodiments or modifications described above may be combined as appropriate. [Explanation of Symbols]

[0095] 100…Motor control device 1…Inverter circuit 3…Motor 4…Anomaly detection unit 5…Power control unit 11u, 11v, 11w…High-potential switching element 12u, 12v, 12w…Low-potential switching element 13u, 13v, 13w…Current sensor 21…Duty limiting unit 22…Selection unit 23…PWM generation 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 multiple phase windings, comprising: a plurality of high-potential-side switching elements and a plurality of low-potential-side switching elements provided corresponding to each phase of the plurality of phases; and a plurality of current sensors connected to each of the plurality of low-potential-side switching elements; A power control unit that controls the plurality of high-potential switching elements and the plurality of low-potential switching elements based on the duty cycle, An abnormality detection unit detects an abnormality by comparing the offset current value detected using the current sensor when the low-potential side switching element is in a non-conductive state with a first threshold value for each of the multiple phases, and determines a fault based on the number of times the abnormality has been detected. Equipped with, 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 generate a limited duty cycle value for the restricted phase, which includes at least the phase in which the abnormality was detected, such that the time during which the low-potential switching element is in a non-conductive state is equal to or greater than the time required to detect the offset current value, thereby limiting the duty cycle value of the restricted phase to a predetermined lower limit value, and to perform a duty cycle limiting process, which controls the high-potential switching element and the low-potential switching element based on the limited duty cycle value. Motor control device.

2. The motor control device according to claim 1, wherein the abnormality detection unit performs a fault determination for each fault determination cycle, and if no abnormality is detected consecutively in the fault determination for each fault determination cycle, the duty cycle limiting process is released.

3. The motor control device according to claim 1, wherein the power control unit generates the limited duty cycle value in the duty cycle limiting process by making the duty cycle value of the phase to be limited, which is smaller than the lower limit value, match the lower limit value.

4. The motor control device according to claim 1, wherein the power control unit 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 a coefficient such that the minimum value of the limited duty value is greater than or equal to the lower limit.

5. The motor control device according to claim 4, wherein the power control unit gradually decreases the coefficient from 1 when the duty limiting process starts, and gradually increases the coefficient to 1 when the duty limiting process ends.

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

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

8. A motor control device according to any one of claims 1 to 7, The motor assists in steering the steering wheel, A torque sensor that detects the steering torque caused by steering the steering wheel, Equipped with, The motor control device controls the drive of the motor in accordance with the steering torque detected by the torque sensor. Electric power steering system.

9. The electric power steering device according to claim 8, When the abnormality detection unit confirms a malfunction, a notification unit notifies the occurrence of the malfunction, A vehicle equipped with the following features.

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