Failure diagnosis device, failure diagnosis method, and program

Abstract

This failure diagnosis device is configured to: charge a capacitor to a prescribed voltage through application of a voltage from an electric power supply by turning a motor drive unit to an OFF state and bringing a reverse connection protection circuit to a conduction state, and subsequently stop charging when the charging is completed; determine an ON failure of the reverse connection protection circuit on the basis of a first voltage between the reverse connection protection circuit and the capacitor and a second voltage between the reverse connection protection circuit and an electric power supply cutoff circuit in a state where the reverse connection protection circuit is switched so that an electric current does not flow from the capacitor side to the electric-power-supply side after the capacitor is charged; determine an OFF failure of the reverse connection protection circuit on the basis of the first voltage and the second voltage in a state where the reverse connection protection circuit is switched so that the electric current flows from the capacitor side to the electric-power-supply-cutoff-circuit side after the capacitor is charged; and determine that an abnormality has occurred in the capacitor or the motor drive unit in response to the first voltage falling below a threshold value when the capacitor is charged by a charging unit.

Description

Fault diagnosis device, fault diagnosis method, and program

[0001] The present invention relates to a fault diagnosis device, a fault diagnosis method, and a program.

[0002] In recent years, motors have been used in various devices, such as electric power steering devices that perform assist control related to steering of a vehicle. In electric power steering devices, a switching circuit is provided on the path to properly control the power supply from a battery, which is a power supply source. Diagnosing whether such a switching circuit is operating normally is important from the perspective of operational safety of electric power steering devices and the like.

[0003] For example, Patent Document 1 discloses a configuration for determining whether there is a failure in MOS-FETs (Metal-Oxide-Semiconductor Field Effect Transistors), which are two switching elements for turning on and off a current path in an electric power steering device.

[0004] Japanese Patent No. 5742356

[0005] For example, in an electric power steering device, in addition to a switching element for power cutoff and a switching element for reverse connection protection, a capacitor is provided on the current path. In order to determine a fault related to the operation of the switching element, it is necessary to determine the status of not only the switching element but also the devices provided around it. Patent Document 1 shows a configuration including a capacitor for absorbing current ripple, but does not consider determining the status of the capacitor.

[0006] In view of the above problems, an object of the present invention is to easily perform fault diagnosis of a device including a reverse connection protection circuit.

[0007] In order to solve the above problems, the present invention has the following configuration: A fault diagnosis device for a motor device having: a motor, a motor drive unit that outputs drive power to the motor, a power supply interruption circuit connected to a power source and configured to be able to switch its conduction state, a reverse connection protection circuit connected to the power supply interruption circuit and the motor drive unit and configured to be able to switch its conduction state, and a capacitor provided in a conduction path between the reverse connection protection circuit and the motor drive unit, wherein a charging unit turns the motor drive unit off and then turns the reverse connection protection circuit on, thereby charging the capacitor by applying a voltage from the power source up to a predetermined voltage, and then stops charging as the charging is completed, and an ON fault determination unit determines an ON fault of the reverse connection protection circuit based on a first voltage between the reverse connection protection circuit and the capacitor and a second voltage between the reverse connection protection circuit and the power supply interruption circuit when the reverse connection protection circuit is switched so that no current flows from the capacitor to the power source after the capacitor has been charged. an OFF fault determination unit that determines an OFF fault of the reverse connection protection circuit based on the first voltage and the second voltage in a state in which the reverse connection protection circuit is switched so that a current flows from the capacitor side to the power supply cutoff circuit side after the capacitor has been charged; and a determination unit that determines that an abnormality has occurred in the capacitor or the motor drive unit when the first voltage falls below a predetermined threshold value or charging is not completed within a predetermined time while the capacitor is being charged by the charging unit.

[0008] Another aspect of the present invention has the following configuration: A fault diagnosis method for a motor device having a motor, a motor drive unit that outputs drive power to the motor, a power supply interruption circuit connected to a power source and configured to be able to switch its conduction state, a reverse connection protection circuit connected to the power supply interruption circuit and the motor drive unit and configured to be able to switch its conduction state, and a capacitor provided in a conduction path between the reverse connection protection circuit and the motor drive unit, comprising: a charging step of turning the motor drive unit off and then turning the reverse connection protection circuit on to charge the capacitor by applying a voltage from the power source up to a predetermined voltage, and then stopping the charging as the charging is completed; an ON fault determination step of determining an ON fault of the reverse connection protection circuit based on a first voltage between the reverse connection protection circuit and the capacitor and a second voltage between the reverse connection protection circuit and the power supply interruption circuit after the capacitor has been charged, in a state in which the reverse connection protection circuit is switched so that no current flows from the capacitor to the power source; a fault diagnosis method comprising: an OFF fault determination step of determining an OFF fault of the reverse connection protection circuit based on the first voltage and the second voltage in a state in which, after the capacitor has been charged, the reverse connection protection circuit has been switched so that a current flows from the capacitor side to the power supply cutoff circuit side; and a determination step of determining that an abnormality has occurred in the capacitor or the motor drive unit in response to the first voltage falling below a predetermined threshold value or charging not being completed within a predetermined time while the capacitor is being charged in the charging step.

[0009] Another aspect of the present invention has the following configuration: a computer for controlling a motor device having: a motor, a motor drive unit that outputs drive power to the motor, a power supply cutoff circuit connected to a power source and configured to be able to switch its conduction state, a reverse connection protection circuit connected to the power supply cutoff circuit and the motor drive unit and configured to be able to switch its conduction state, and a capacitor provided in a conduction path between the reverse connection protection circuit and the motor drive unit, the computer comprising: a charging step of turning the motor drive unit off and then turning the reverse connection protection circuit on to charge the capacitor by applying a voltage from the power source up to a predetermined voltage, and then stopping the charging as the charging is completed; and an ON fault determination step of determining an ON fault of the reverse connection protection circuit based on a first voltage between the reverse connection protection circuit and the capacitor and a second voltage between the reverse connection protection circuit and the power supply cutoff circuit after the capacitor has been charged, with the reverse connection protection circuit switched so that no current flows from the capacitor to the power source. a determination step of determining an OFF fault of the reverse connection protection circuit based on the first voltage and the second voltage in a state in which the reverse connection protection circuit is switched so that a current flows from the capacitor side to the power supply cutoff circuit side after the capacitor has been charged; and a determination step of determining that an abnormality has occurred in the capacitor or the motor drive unit in response to the first voltage falling below a predetermined threshold value or charging not being completed within a predetermined time while the capacitor is being charged in the charging step.

[0010] According to the present invention, it is possible to easily perform a fault diagnosis of a device including a reverse connection protection circuit.

[0011] 1 is a schematic diagram of a circuit configuration around a reverse connection protection circuit according to one embodiment of the present invention. 2 is a schematic diagram for explaining switching during ON fault diagnosis of a reverse connection protection circuit according to one embodiment of the present invention. 3 is a schematic diagram for explaining switching during OFF fault diagnosis of a reverse connection protection circuit according to one embodiment of the present invention. 4 is a flowchart of fault determination processing according to one embodiment of the present invention. 5 is a flowchart of ON fault determination processing according to one embodiment of the present invention. 6 is a flowchart of OFF fault determination processing according to one embodiment of the present invention. 7 is a schematic diagram of an electric power steering device according to one embodiment of the present invention.

[0012] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Note that the embodiment described below is one embodiment for explaining the present invention and is not intended to be interpreted as limiting the present invention. Furthermore, not all of the configurations described in each embodiment are necessarily essential configurations for solving the problems of the present invention. Furthermore, in each drawing, the same components are assigned the same reference numerals to indicate corresponding relationships.

[0013] Furthermore, in this specification, the terms "first" and "second" are used merely to distinguish from other components and are not intended to be interpreted as being limited to specific components. Therefore, such expressions may be interpreted as appropriate depending on the configuration of the device to which they are applied. Furthermore, in this specification, when components that achieve the same type or function require individual explanation, a suffix (a, b, ...) is added to the reference number, and when a comprehensive explanation is given, the suffix is ​​omitted.

[0014] First Embodiment A first embodiment of the present invention will be described below. The present invention is widely applicable to devices including a reverse connection protection circuit for power supply to a motor device or the like. In this embodiment, an electric power steering device (EPS: Electric Power Steering) mounted on a vehicle will be described as an example.

[0015] [Circuit Overview] Fig. 1 is a schematic diagram of the circuit configuration of a power supply connection circuit 100 arranged on a power supply path between a battery (not shown) and a three-phase bridge circuit 104 according to this embodiment. An example configuration when applied to an electric power steering device is shown in Fig. 7 and will be described later. The power supply connection circuit 100 is configured to include switching elements 101 and 102 and a capacitor 103. A voltage is applied to the power supply connection circuit 100 from a power supply (PIG), and the power supply to the three-phase bridge circuit 104 is switched (conductive state / non-conductive state) based on an instruction described later.

[0016] The switching element 101 is configured with a FET (Field Effect Transistor) and functions as a power supply cutoff circuit (power supply cutoff FET). The switching element 101 cuts off the flow of current from the power supply to VR2 when an OFF signal is received, and becomes conductive from the power supply to VR2 when an ON signal is received. Note that in the switching element 101, a parasitic diode may cause a reverse current flow from VR2 to the power supply when an OFF signal is received. The switching element 102 is configured with a FET and functions as a reverse connection protection circuit (reverse connection protection FET). The switching element 102 cuts off the flow of current from VR1 to VR2 when an OFF signal is received, and becomes conductive from VR1 to VR2 when an ON signal is received. Note that in the switching element 102, a parasitic diode may cause a reverse current flow from VR2 to VR1 when an OFF signal is received.

[0017] The FET has a gate, a source, and a drain terminal. The switching elements 101 and 102 may be, for example, N-channel or P-channel MOS-FETs, but are not limited to these.

[0018] The capacitor 103 has a predetermined capacitance and functions as a protection circuit against the application of an unintended current (for example, a ripple current) to the three-phase bridge circuit 104. The three-phase bridge circuit 104 is a circuit for driving using electric power from a power supply, and in this embodiment corresponds to the configuration on the motor side of an electric power steering device 700 as described later with reference to FIG.

[0019] In this embodiment, an N-channel MOS-FET will be described as an example. The drain of the FET of switching element 102 is connected to capacitor 103 and three-phase bridge circuit 104, and the voltage value at this connection point is defined as VR1 (first voltage value). The source of the FET of switching element 101 is connected to the source of the FET of switching element 102, and the voltage value at this connection point is defined as VR2 (second voltage value).

[0020] In this embodiment, a fault is determined by checking the operation of the following three components shown in Fig. 1. Note that in this embodiment, it is assumed that the switching element 101 serving as the power supply cutoff circuit is normal. (i) Checking the ON / OFF operation of the switching element 102 serving as the reverse connection protection circuit, (ii) Checking the operation of the capacitor 103, and (iii) Checking the operation of the three-phase bridge circuit 104.

[0021] In the following description, a state in which the switching element 102, which is a reverse connection protection circuit, does not normally turn off in response to an OFF signal is referred to as an "ON failure" (stuck in the ON state). Also, a state in which the switching element 102, which is a reverse connection protection circuit, does not normally turn on in response to an ON signal is referred to as an "OFF failure" (stuck in the OFF state). Diagnoses for these are referred to as "ON failure diagnosis" and "OFF failure diagnosis," respectively.

[0022] FIG. 2 is a diagram showing the state of the power supply connection circuit 100 during ON fault diagnosis. FIG. 2( a) shows the state before diagnosis. First, the three-phase bridge circuit 104 is set to a fully OFF state. Here, the fully OFF state corresponds to a state in which no current flows from the VR1 side to the three-phase bridge circuit 104 side. Then, an ON signal is output as a switching signal to the switching element 101, and an OFF signal is output as a switching signal to the switching element 102. Note that, as long as current flows from the VR2 side to the VR1 side in the switching element 102, an ON signal may be output to the switching element 102. In this state, the capacitor 103 is in a conductive state from the power supply (PIG), a voltage is applied to the capacitor 103, and the capacitor 103 is charged.

[0023] After a certain period of time has elapsed in the state shown in FIG. 2(a), the charging of capacitor 103 is considered complete, and the state is switched to that shown in FIG. 2(b), and an ON fault diagnosis is performed. Completion of charging may be determined by detecting that the charging voltage VR1 of capacitor 103 has reached a predetermined voltage. In FIG. 2(b), an OFF signal is output as a switching signal to switching elements 101 and 102. Note that if an OFF signal was output as a switching signal to switching element 102 before the diagnosis was performed, an OFF signal is output as a switching signal only to switching element 101. This interrupts current from the power supply (PIG) ​​to VR2. At this time, if the OFF function of switching element 102 as a reverse connection protection circuit is normal, VR2 = 0 V. On the other hand, if an abnormality occurs in switching element 102 as a reverse connection protection circuit, i.e., if an ON fault occurs, VR2 will be at the same potential as VR1 (VR2 = VR1). This change is used to diagnose an ON fault. The detailed flow of the diagnosis will be described later with reference to FIGS.

[0024] 3A and 3B are diagrams showing the state of the power supply connection circuit 100 during OFF fault diagnosis. FIG. 3A shows the state before diagnosis. First, the three-phase bridge circuit 104 is set to an all-OFF state. Then, an ON signal is output as a switching signal to the switching element 101, and an ON signal is output as a switching signal to the switching element 102. Note that, since it is sufficient for current to flow from the VR2 side to the VR1 side in the switching element 102, an OFF signal may be output to the switching element 102. In this state, the capacitor 103 is in a conductive state from the power supply (PIG), a voltage is applied to the capacitor 103, and the capacitor 103 is charged.

[0025] After a certain period of time has elapsed in the state shown in FIG. 3(a), the charging of capacitor 103 is considered complete, and the state is switched to that shown in FIG. 3(b), and an OFF fault diagnosis is performed. Completion of charging may be determined by detecting that the charging voltage VR1 of capacitor 103 has reached a predetermined voltage. In FIG. 3(b), an OFF signal is output as a switching signal to switching element 101. If an OFF signal was output to switching element 102 before the diagnosis was performed, an ON signal is output to switching element 102. This interrupts current from the power supply (PIG) ​​to VR2. If the ON function of switching element 102, acting as a reverse connection protection circuit, is normal, voltage is conducted from VR1 to VR2, and VR2 has the same potential as VR1 (VR2 = VR1). On the other hand, if an abnormality occurs in switching element 102 acting as a reverse connection protection circuit, i.e., if an OFF fault occurs, VR2 = 0 V. This change is used to diagnose an OFF fault. The detailed flow of the diagnosis will be described later with reference to FIGS.

[0026] [Processing Flow] The fault diagnosis processing according to this embodiment will be described using the flowcharts shown in Figures 4 to 6. This processing flow may be implemented by a control unit (not shown) of a device, such as an electric power steering device, in which the power supply connection circuit 100 according to this embodiment is provided, reading and executing programs and various data stored in a memory unit (not shown).

[0027] This process flow may be executed, for example, when a vehicle (not shown) equipped with the electric power steering device is started, or may be executed periodically at a predetermined timing. Fig. 4 shows the overall flow of the fault diagnosis process according to this embodiment. For convenience, the processing entity is described as a control unit, which corresponds to, for example, a CPU 701 described later in Fig. 7.

[0028] In S401, the control unit switches the three-phase bridge circuit 104 to the all-OFF state. As described above, the all-OFF state corresponds to a state in which no current flows from the capacitor 103 to the three-phase bridge circuit 104, and the control content may differ depending on the configuration of the three-phase bridge circuit 104, etc.

[0029] In S402, the control unit executes an ON fault determination process for the power supply connection circuit 100. Details of this process will be described later with reference to Fig. 5. After this process, the process of the control unit proceeds to S403.

[0030] In S403, the control unit determines whether VR1 has fallen below threshold A during the ON fault determination process in S402. Threshold A is predefined based on the hardware configuration, the applied voltage of the power supply (PIG), etc., and is stored so that it can be referenced. Threshold A corresponds to a condition for executing and continuing ON fault determination and OFF fault determination. Threshold A may be set to, for example, 5 V, as a voltage value at which diagnosis can be performed stably without erroneous detection. If VR1 has fallen below threshold A (YES in S403), the control unit proceeds to S404. On the other hand, if VR1 has not fallen below threshold A (NO in S403), the control unit proceeds to S406.

[0031] In S404, the control unit determines whether or not a motor current has flowed. The motor current corresponds to the current flowing on the three-phase bridge circuit 104 side, and whether or not a motor current has flowed is monitored as appropriate. This will be described in detail later with reference to FIG. 7. If a motor current has flowed (YES in S404), the control unit proceeds to S405. On the other hand, if a motor current has not flowed (NO in S404), the control unit returns to S402 and repeats the process.

[0032] In S405, the control unit determines that an abnormality has occurred on the three-phase bridge circuit 104 side and notifies the user of this fact. The notification method is not particularly limited, and may be, for example, a notification to another control unit of the vehicle equipped with the electric power steering device, or a visual or audible notification to the driver of the vehicle. Then, this processing flow ends.

[0033] In S406, the control unit determines whether the result of the ON failure determination process in S402 is a normal state. If the determination result is a normal state (YES in S406), the control unit proceeds to S407. On the other hand, if the determination result is not a normal state (NO in S406), the control unit proceeds to S412.

[0034] In S407, the control unit executes an OFF fault determination process for the power supply connection circuit 100. Details of this process will be described later with reference to Fig. 6. After this process, the process of the control unit proceeds to S408.

[0035] In S408, the control unit determines whether VR1 has fallen below threshold A during the OFF fault determination process of S407. Threshold A may be the same as the value in the determination step of S403. If VR1 has fallen below threshold A (YES in S408), the control unit proceeds to S404. On the other hand, if VR1 has not fallen below threshold A (NO in S408), the control unit proceeds to S409.

[0036] 4, if the determination result in S408 is "YES," the process proceeds to step S404 to determine whether motor current has flowed, but this is not limited to this. Since it has already been confirmed that motor current is not flowing during the ON fault determination, this process may be omitted, and if the determination in S408 is "YES," the process may return directly to step S407. Also, if the determination in S408 is "YES," the process proceeds to step S404 to determine whether motor current has flowed, but if it is determined here that motor current is not flowing (NO in S404), the process may then proceed directly to the OFF fault determination in S407.

[0037] In S409, the control unit determines whether the result of the OFF fault determination process in S407 is a normal state. If the determination result is a normal state (YES in S409), this processing flow ends. In this case, the control unit may notify other parts, etc., that the state is normal. If the determination result is not normal (NO in S409), the control unit proceeds to S410.

[0038] In S410, the control unit determines whether the result of the OFF fault determination process in S407 is an abnormality other than that of the reverse connection protection circuit. If the determination result is an abnormality other than that of the reverse connection protection circuit (YES in S410), the control unit proceeds to S413. On the other hand, if the determination result is not an abnormality other than that of the reverse connection protection circuit (NO in S410), the control unit proceeds to S411.

[0039] In S411, the control unit determines that an OFF failure has occurred in the switching element 102 as a reverse connection protection circuit, and notifies the user of this fact. The notification method is not particularly limited, and may be, for example, a notification to another control unit of the vehicle equipped with the electric power steering device, or a visual or audible notification to the driver of the vehicle. Then, this processing flow ends.

[0040] In S412, the control unit determines whether the result of the ON fault determination process in S402 is an abnormality other than that of the reverse connection protection circuit. If the determination result is an abnormality other than that of the reverse connection protection circuit (YES in S412), the control unit proceeds to S413. On the other hand, if the determination result is not an abnormality other than that of the reverse connection protection circuit (NO in S412), the control unit proceeds to S414.

[0041] In S413, the control unit determines that an abnormality has occurred in the capacitor 103 and notifies the user of this. That is, if the ON fault determination process in S402 or the OFF fault determination process in S407 determines that an abnormality is occurring in something other than the reverse connection protection circuit, the control unit identifies that an abnormality has occurred in the capacitor 103. Note that, among the abnormalities other than the reverse connection protection circuit, if an abnormality has occurred on the three-phase bridge circuit 104 side, this is identified in steps S404 and S405. The notification method here is not particularly limited, and for example, the notification may be sent to another control unit of the vehicle equipped with the electric power steering device, or the driver of the vehicle may be notified visually or audibly. Then, this processing flow ends.

[0042] In S414, the control unit determines that an ON failure has occurred in the switching element 102 as a reverse connection protection circuit, and notifies the user of this fact. The notification method is not particularly limited, and may be, for example, a notification to another control unit of the vehicle equipped with the electric power steering device, or a visual or audible notification to the driver of the vehicle. Then, this processing flow ends.

[0043] (ON Failure Determination Process) FIG. 5 is a flowchart of the ON failure determination process according to this embodiment, which corresponds to step S402 in FIG.

[0044] In S501, the control unit outputs a switching signal to switch the capacitor 103 to a conductive state from the power supply (PIG). That is, the switching is performed as shown in Fig. 2(a). With the switching, charging of the capacitor 103 begins.

[0045] In S502, the control unit determines whether VR1 is equal to or greater than threshold B. Threshold B is determined in advance based on the hardware configuration, the applied voltage of the power supply (PIG), etc., and is stored so that it can be referenced. Threshold B corresponds to the condition for executing and continuing ON fault determination. Threshold B is higher than threshold A, and may be set to, for example, 7.9 V, which makes it less likely that diagnosis will be stopped due to a voltage drop in VR1. If VR1 is equal to or greater than threshold B (YES in S502), the control unit proceeds to S505. On the other hand, if VR1 is not equal to or greater than threshold B (NO in S502), the control unit proceeds to S503.

[0046] In S503, the control unit determines whether a predetermined time has elapsed since the start of conduction in S501. The predetermined time may be determined in advance depending on the capacitance of capacitor 103, the voltage applied from the power supply (PIG), the threshold value B used in S502, etc. If the predetermined time has elapsed (YES in S503), the control unit proceeds to S504. On the other hand, if the predetermined time has not elapsed (NO in S503), the control unit returns to S502 and continues charging capacitor 103.

[0047] In S504, the control unit determines that an abnormality has occurred in a device other than the switching element 102, which is the reverse connection protection circuit. In this embodiment, this is treated as an abnormality occurring in either the capacitor 103 or the three-phase bridge circuit 104. Then, this processing flow ends, and the process proceeds to S403 in FIG. 4.

[0048] In S505, the control unit outputs a switching signal to switch the power supply (PIG) ​​to the capacitor 103 so that the power supply is not electrically connected to the capacitor 103. That is, the switching is performed as shown in FIG. 2B. With the switching, charging of the capacitor 103 is interrupted.

[0049] In S506, the control unit resets each counter, including a normal time counter for counting the time during which the device is continuously determined to be normal, and an abnormal time counter for counting the time during which the device is continuously determined to be abnormal.

[0050] In S507, the control unit determines whether the voltage value of VR1 is equal to or greater than threshold value A. If the voltage value of VR1 is equal to or greater than threshold value A (YES in S507), the control unit proceeds to S508. On the other hand, if the voltage value of VR1 is not equal to or greater than threshold value A (NO in S507), the control unit proceeds to S517.

[0051] In S508, the control unit determines whether the voltage value of VR2 is greater than the voltage value of (VR1-α). α is a margin value determined according to the hardware configuration of the power supply connection circuit 100. The margin value α may be set to, for example, 2 V. When the OFF function of the switching element 102, which is a reverse connection protection circuit, is normal, VR2=0 or a state close to this. In the case of an ON failure, VR2 and VR1 are at the same potential. Therefore, when the voltage value of VR2 is greater than the voltage value of (VR1-α), it is treated as an abnormality in the OFF function (ON failure). When the voltage value of VR2 is greater than the voltage value of (VR1-α) (YES in S508), the control unit proceeds to S509. On the other hand, when the voltage value of VR2 is not greater than the voltage value of (VR1-α) (NO in S508), the control unit proceeds to S513.

[0052] In S509, the control unit starts counting up the abnormality time counter, or if the counter is already counting up, continues counting up.

[0053] In S510, the control unit resets the normal time counter.

[0054] In S511, the control unit determines whether the value of the abnormality time counter exceeds a predetermined duration A. The duration A may be set to, for example, 200 ms. In this case, if the diagnostic cycle is 1 ms, the count is 200, and if the diagnostic cycle is 2 ms, the count is 100. If the value of the abnormality time counter exceeds the predetermined duration A (YES in S511), the control unit proceeds to S512. If the value of the abnormality time counter does not exceed the predetermined duration A (NO in S511), the control unit returns to S507 and repeats the process.

[0055] In S512, the control unit determines that an ON failure has occurred in the switching element 102, which is a reverse connection protection circuit. That is, the control unit diagnoses that the switching element 102, which is a reverse connection protection circuit, is in a state where it is not normally turning OFF in response to an OFF signal. Then, this processing flow ends, and the process proceeds to S403 in FIG. 4.

[0056] In S513, the control unit starts counting up the normal time counter, or if counting up is already underway, continues counting up.

[0057] In S514, the control unit resets the abnormality time counter.

[0058] In S515, the control unit determines whether the value of the normal time counter exceeds a predetermined duration B. Duration B may be set to, for example, 10 ms. In this case, if the diagnostic period is 1 ms, the normal time counter counts to 10, and if the diagnostic period is 2 ms, the normal time counter counts to 5. If the value of the normal time counter exceeds the predetermined duration B (YES in S515), the control unit proceeds to S516. If the value of the normal time counter does not exceed the predetermined duration B (NO in S515), the control unit returns to S507 and repeats the process.

[0059] In S516, the control unit determines that no ON failure has occurred in the switching element 102, which is a reverse connection protection circuit. That is, the control unit diagnoses that the switching element 102, which is a reverse connection protection circuit, is in a state in which the OFF operation is performed normally in response to the OFF signal. Then, this processing flow ends, and the process proceeds to S403 in FIG. 4.

[0060] In S517, the control unit determines whether the number of times the capacitor 103 has been charged exceeds a threshold C. The threshold C is not particularly limited and may be, for example, 2 (i.e., the upper limit of the number of times the capacitor 103 can be charged is 3). If the number of times the capacitor 103 has been charged exceeds the threshold C (YES in S517), the process ends and proceeds to S403 in FIG. 4. This corresponds to a case where the normality / abnormality of the OFF function could not be determined after charging the capacitor 103 multiple times, and therefore may be treated as an abnormality determination other than that of the reverse connection protection circuit. On the other hand, if the number of times the capacitor 103 has been charged does not exceed the threshold C (NO in S517), the control unit returns to S501 and repeats the process. In this case, the control unit counts up the number of times the capacitor 103 has been charged by one in order to recharge the capacitor 103.

[0061] (OFF Failure Determination Process) FIG. 6 is a flowchart of the OFF failure determination process according to this embodiment, which corresponds to step S407 in FIG.

[0062] In S601, the control unit outputs a switching signal to switch the capacitor 103 to a conductive state from the power supply (PIG). That is, the switching is performed as shown in Fig. 3(a). With the switching, charging of the capacitor 103 begins.

[0063] In S602, the control unit determines whether VR1 is equal to or greater than threshold B. Threshold B may be the same value as that used in the ON failure determination in FIG. 5. If VR1 is equal to or greater than threshold B (YES in S602), the control unit proceeds to S605. On the other hand, if VR1 is not equal to or greater than threshold B (NO in S602), the control unit proceeds to S603.

[0064] In S603, the control unit determines whether a predetermined time has elapsed since the start of conduction in S601. The predetermined time may be determined in advance depending on the capacitance of the capacitor 103, the voltage applied from the power supply (PIG), the threshold value B used in S602, etc. If the predetermined time has elapsed (YES in S603), the control unit proceeds to S604. On the other hand, if the predetermined time has not elapsed (NO in S603), the control unit returns to S602 and continues charging the capacitor 103.

[0065] In S604, the control unit determines that an abnormality has occurred in a device other than the switching element 102, which is the reverse connection protection circuit. In this embodiment, this is treated as an abnormality occurring in either the capacitor 103 or the three-phase bridge circuit 104. Then, this processing flow ends, and the process proceeds to S408 in FIG. 4.

[0066] In S605, the control unit outputs a switching signal to switch the power supply (PIG) ​​to the capacitor 103 so that the power supply is not electrically connected to the capacitor 103. That is, the switching is performed as shown in FIG. 3B. Charging the capacitor 103 is interrupted in response to the switching. Note that if the capacitor 103 is sufficiently charged as a result of the ON failure determination that has already been performed, the processes of S601 to S605 may be omitted.

[0067] In S606, the control unit resets each counter, including a normal time counter for counting the time during which the device is continuously determined to be normal, and an abnormal time counter for counting the time during which the device is continuously determined to be abnormal.

[0068] In S607, the control unit determines whether the voltage value of VR1 is equal to or greater than threshold value A. If the voltage value of VR1 is equal to or greater than threshold value A (YES in S607), the control unit proceeds to S608. On the other hand, if the voltage value of VR1 is not equal to or greater than threshold value A (NO in S607), the control unit proceeds to S617.

[0069] In S608, the control unit determines whether the voltage value of VR2 is smaller than the voltage value (0 + β). β is a margin value defined depending on the hardware configuration of the power supply connection circuit 100. The margin value β may be set to, for example, 2 V. When the ON function of the switching element 102, which is the reverse connection protection circuit, is normal, VR2 = VR1 or a state close to this. When an OFF fault occurs, VR2 = 0 or a state close to this. Therefore, when the voltage value of VR2 is smaller than the voltage value (0 + β), it is treated as an abnormality in the ON function (OFF fault). When the voltage value of VR2 is smaller than the voltage value (0 + β) (YES in S608), the control unit proceeds to S609. On the other hand, when the voltage value of VR2 is not smaller than the voltage value (0 + β) (NO in S608), the control unit proceeds to S613.

[0070] In S609, the control unit starts counting up the abnormality time counter, or if the counter is already counting up, continues counting up.

[0071] In S610, the control unit resets the normal time counter.

[0072] In S611, the control unit determines whether the value of the abnormality time counter exceeds a predetermined duration A. The duration A may be the same value as that used for the ON failure determination in FIG. 5. If the value of the abnormality time counter exceeds the predetermined duration A (YES in S611), the control unit proceeds to S612. If the value of the abnormality time counter does not exceed the predetermined duration A (NO in S611), the control unit returns to S607 and repeats the process.

[0073] In S612, the control unit determines that an OFF failure has occurred in the switching element 102, which is a reverse connection protection circuit. That is, the control unit diagnoses that the switching element 102, which is a reverse connection protection circuit, is in a state where it is not normally turning on in response to an ON signal. Then, this processing flow ends, and the process proceeds to S408 in FIG. 4.

[0074] In S613, the control unit starts counting up the normal time counter, or if counting up is already underway, continues counting up.

[0075] In S614, the control unit resets the abnormality time counter.

[0076] In S615, the control unit determines whether the value of the normal time counter exceeds a predetermined duration B. The same value as that used for the ON fault determination in FIG. 5 may be used as the duration B. If the value of the normal time counter exceeds the predetermined duration B (YES in S615), the control unit proceeds to S616. If the value of the normal time counter does not exceed the predetermined duration B (NO in S615), the control unit returns to S607 and repeats the process.

[0077] In S616, the control unit determines that an OFF failure has not occurred in the switching element 102, which is a reverse connection protection circuit. That is, the control unit diagnoses that the switching element 102, which is a reverse connection protection circuit, is in a state in which the ON operation is normally performed in response to an ON signal. Then, this processing flow ends, and the process proceeds to S408 in FIG. 4.

[0078] In S617, the control unit determines whether the number of times the capacitor 103 has been charged has exceeded a threshold C. The threshold C here is not particularly limited and may be, for example, 2 (i.e., the upper limit of the number of times the capacitor 103 can be charged is 3 times). If the number of times the capacitor has been charged has exceeded the threshold C (YES in S617), this processing flow ends and the process proceeds to S408 in FIG. 4. On the other hand, if the number of times the capacitor has been charged has not exceeded the threshold C (NO in S617), the control unit returns to S601 and repeats the process. In this case, the control unit counts up the number of times the capacitor 103 has been charged by one in order to recharge the capacitor 103.

[0079] [Application Example] Fig. 7 is a block diagram showing the schematic configuration of a motor device including the power supply connection circuit 100 shown in Fig. 1, for example, an electric power steering device 700. Note that Fig. 7 focuses on the components related to this embodiment and omits some components such as a steering mechanism, a steering torque detector, and a vehicle speed detector. Therefore, the electric power steering device 700 may further include other components.

[0080] The electric power steering device 700 includes a CPU 701, an FET drive circuit 702, a current detection circuit 703, a motor cutoff circuit 704, a motor rotation angle detection circuit 705, a battery 706, a power supply cutoff circuit 707, a reverse connection protection circuit 708, a capacitor 709, an inverter 710, a terminal voltage detector 713, a switching circuit 715, a motor 716, and a rotation angle sensor 717. The components are connected to each other so as to be able to communicate with each other via a CAN (Controller Area Network), electrical wiring, or the like.

[0081] The CPU (Central Processing Unit) 701 is a control unit that controls the electric power steering device 700. The CPU 701 may be configured, for example, as part of an ECU (Electronic Control Unit: not shown) that constitutes the electric power steering device 700. The FET drive circuit 702 controls the operation of the inverter 710 based on instructions from the CPU 701. The current detection circuit 703 detects the current in the inverter 710 and notifies the CPU 701. The motor cutoff circuit 704 controls the switching circuit 715 based on instructions from the CPU 701. The motor rotation angle detection circuit 705 notifies the CPU 701 of the rotation angle of the motor 716 based on a value detected by a rotation angle sensor 717.

[0082] The battery 706 is a power source for the electric power steering device 700. The battery 706 corresponds to the power source (PIG) ​​shown in FIG. 1. The power supply cutoff circuit 707 is configured with an FET, and switching control is performed based on a switching signal A from the CPU 701. The power supply cutoff circuit 707 corresponds to the switching element 101 shown in FIG. 1 and other figures. The reverse connection protection circuit 708 is configured with an FET, and switching control is performed based on a switching signal B from the CPU 701. The reverse connection protection circuit 708 corresponds to the switching element 102 shown in FIG. 1 and other figures. The capacitor 709 is configured to be able to charge and discharge the voltage applied from the battery 706. The capacitor 709 corresponds to the capacitor 103 shown in FIG. 1 and other figures.

[0083] In this embodiment, the motor 716 is a three-phase motor having three-phase windings, and the configuration on the motor 716 side of the inverter 710 corresponds to the three-phase bridge circuit 104 shown in Fig. 1 etc. The CPU 701 appropriately monitors VR1, which is the voltage between the reverse connection protection circuit 708 and the inverter 710, and VR2, which is the voltage between the power supply cutoff circuit 707 and the reverse connection protection circuit 708, and acquires the values.

[0084] The inverter 710 applies current to the motor 716 based on instructions from the CPU 701. The inverter 710 includes six FETs 711a to 711f and three current sensors 712a to 712c corresponding to the configuration of the motor 716, which is a three-phase motor. The FETs 711a to 711f are controlled based on instructions from the CPU 701 via an FET drive circuit 702. The values ​​detected by the current sensors 712a to 712c are notified to the CPU 701 via a current detection circuit 703. The values ​​of the voltages VA, VB, and VC applied to the motor 716 by the inverter 710 are also notified to the CPU 701.

[0085] Terminal voltage detector 713 detects the terminal voltage applied between inverter 710 and motor 716. Terminal voltage detector 713 includes six resistors 714a to 714f corresponding to the configuration of motor 716, which is a three-phase motor. FETs 715a to 715c are controlled based on instructions from CPU 701 via motor shutoff circuit 704.

[0086] 1 corresponds to a state in which no current flows through the FETs 711a to 711f of the inverter 710 and the FETs 715a to 715c connected to the motor 716 by controlling these components. In this state, the motor current through the motor 716 is zero.

[0087] For example, suppose that FETs 711a and 711d in inverter 710 simultaneously short-circuit. In this case, even if the FETs are controlled to be all OFF, the motor current will not be zero. Furthermore, if FET 711d in inverter 710 short-circuits, the power charged in capacitor 709 causes a current to flow through the path VR1 → resistor 714a of terminal voltage detector 713 → FET 711d, and this current is detected by current detection circuit 703.

[0088] Furthermore, if FET 711d and FET 715a in inverter 710 simultaneously fail short-circuited, the power charged in capacitor 709 causes current to flow through a path of VR1 → resistor 714b of terminal voltage detector 713 → FET 715b → FET 715a → FET 711d in inverter 710, and a path of VR1 → resistor 714c of terminal voltage detector 713 → FET 715c → FET 715a → FET 711d in inverter 710, and this is detected by current detection circuit 703. Furthermore, if FETs 711c, 711d, and FET 715a in inverter 710 simultaneously fail short-circuited, the power charged in capacitor 709 causes current to flow through a path of VR1 → FET 711c in inverter 710 → FET 715c → FET 715a → FET 711d in inverter 710, and this is detected by current detection circuit 703.

[0089] In this way, for example, the detection result of the current on the three-phase bridge circuit side is used in an electric power steering device 700, which is an example of a motor device, to diagnose the normality / abnormality of the capacitor and the normality / abnormality of the three-phase bridge circuit side, in addition to the normality / abnormality of the ON function and OFF function of the reverse polarity protection circuit.

[0090] As described above, this embodiment makes it possible to easily diagnose faults in a device including a reverse connection protection circuit. In particular, it is possible to determine whether the ON and OFF functions of the reverse connection protection circuit are normal or abnormal, whether the capacitor is normal or abnormal, and whether the three-phase bridge circuit is normal or abnormal, without adding any new components to the conventional configuration.

[0091] <Other Embodiments> In the above embodiment, an EPS has been described as an example of a fault diagnosis target. However, the present invention can also be applied to other devices, and may be applied to, for example, a device including a motor, such as an electric actuator device with a linear motion mechanism. It may also be used, for example, in an electric actuator device that controls the brakes of a vehicle. Furthermore, the present invention is not limited to motor control, and the processing allocation method according to the present invention may also be applied to other control.

[0092] In addition, in the present invention, a program or application for realizing the functions of the above-mentioned embodiments can be supplied to a system or device using a network or a storage medium, etc., and one or more processors in the computer of the system or device can read and execute the program.

[0093] As such, the present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these modifications and applications are included in the scope of protection sought.

[0094] As described above, this specification discloses the following: (1) A fault diagnosis device (e.g., 701) for a motor device having: a motor (e.g., 716), a motor drive unit (e.g., 104, 710, 715a to 715c) that outputs drive power to the motor, a power supply cutoff circuit (e.g., 101, 707) connected to a power source (e.g., 706) and configured to be able to switch its conduction state, a reverse connection protection circuit (e.g., 102, 708) connected to the power supply cutoff circuit and the motor drive unit and configured to be able to switch its conduction state, and a capacitor (e.g., 103, 709) provided in a conduction path between the reverse connection protection circuit and the motor drive unit, wherein the charging unit (e.g., 701) turns the motor drive unit off and then turns the reverse connection protection circuit on, thereby applying a voltage from the power source to charge the capacitor up to a predetermined voltage, and then stops charging as the charging is completed; an ON fault determination unit (e.g., 701) that determines an ON fault of the reverse connection protection circuit based on a first voltage (e.g., VR1) between the reverse connection protection circuit and the capacitor and a second voltage (e.g., VR2) between the reverse connection protection circuit and the power supply cut-off circuit when the reverse connection protection circuit is switched so that no current flows from the capacitor to the power supply after the capacitor has been charged; an OFF fault determination unit (e.g., 701) that determines an OFF fault of the reverse connection protection circuit based on the first voltage and the second voltage when the reverse connection protection circuit is switched so that current flows from the capacitor to the power supply cut-off circuit after the capacitor has been charged; and a determination unit (e.g., 701) that determines an abnormality in the capacitor or the motor drive unit when the first voltage falls below a predetermined threshold or charging is not completed within a predetermined time while the capacitor is being charged by the charging unit. This configuration makes it possible to easily perform a fault diagnosis on a device including a reverse connection protection circuit.

[0095] (2) The fault diagnosis device according to (1), wherein the charging unit causes the capacitor to be charged again when the first voltage falls below a predetermined threshold during the determination process by the ON fault determination unit and the OFF fault determination unit. With this configuration, the fault diagnosis can be continued by recharging the capacitor in response to the loss of charge in the capacitor.

[0096] (3) The fault diagnosis device according to (1) or (2), wherein the ON fault determination unit determines that the reverse connection protection circuit has an ON fault when a state in which the second voltage is greater than a difference between the first voltage and a predetermined margin value continues for a first duration. With this configuration, by performing a fault determination when it is determined that an ON fault state continues, it is possible to improve the accuracy of the diagnosis.

[0097] (4) The fault diagnosis device according to any one of (1) to (3), wherein the OFF fault determination unit determines that the reverse connection protection circuit has an OFF fault when the second voltage remains smaller than a predetermined margin value for a second duration. With this configuration, it is possible to improve the accuracy of the diagnosis by making a fault determination when it is determined that the OFF fault state continues.

[0098] (5) The fault diagnosis device according to any one of (1) to (4), wherein the power supply interruption circuit and the reverse connection protection circuit are configured with FETs (Field Effect Transistors), and a source of the power supply interruption circuit and a source of the reverse connection protection circuit are connected. With this configuration, fault diagnosis can be performed on a configuration using a power supply interruption circuit and a reverse connection protection circuit that use FETs.

[0099] (6) The fault diagnosis device according to any one of (1) to (5), wherein the motor device is an electric power steering device. With this configuration, it is possible to diagnose faults in a reverse connection protection circuit, a capacitor, and a three-phase bridge circuit for the electric power steering device.

[0100] (7) A fault diagnosis method for a motor device having a motor (e.g., 716), a motor drive unit (e.g., 104, 710, 715a to 715c) that outputs drive power to the motor, a power supply cutoff circuit (e.g., 101, 707) that is connected to a power source (e.g., 706) and is configured to be able to switch its conduction state, a reverse connection protection circuit (e.g., 102, 708) that is connected to the power supply cutoff circuit and the motor drive unit and is configured to be able to switch its conduction state, and a capacitor (e.g., 103, 709) that is provided in a conduction path between the reverse connection protection circuit and the motor drive unit, the method comprising: a charging step of charging the capacitor to a predetermined voltage by applying a voltage from the power source by turning the motor drive unit off and then turning the reverse connection protection circuit on, and then stopping the charging as the charging is completed; a fault diagnosis method comprising: an ON fault determination step of determining an ON fault of the reverse connection protection circuit based on a first voltage between the reverse connection protection circuit and the capacitor and a second voltage between the reverse connection protection circuit and the power supply cut-off circuit in a state in which the reverse connection protection circuit is switched so that a current does not flow from the capacitor side to the power supply side after the capacitor has been charged; an OFF fault determination step of determining an OFF fault of the reverse connection protection circuit based on the first voltage and the second voltage in a state in which the reverse connection protection circuit is switched so that a current flows from the capacitor side to the power supply cut-off circuit side after the capacitor has been charged; and a determination step of determining that an abnormality has occurred in the capacitor or the motor drive unit when the first voltage falls below a predetermined threshold or charging is not completed within a predetermined time while the capacitor is being charged in the charging step. This configuration makes it possible to easily perform fault diagnosis of a device including a reverse connection protection circuit.

[0101] (8) A computer (e.g., 701) for controlling a motor device having a motor (e.g., 716), a motor drive unit (e.g., 104, 710, 715a to 715c) that outputs drive power to the motor, a power supply cutoff circuit (e.g., 101, 707) that is connected to a power source (e.g., 706) and is configured to be able to switch its conduction state, a reverse connection protection circuit (e.g., 102, 708) that is connected to the power supply cutoff circuit and the motor drive unit and is configured to be able to switch its conduction state, and a capacitor (e.g., 103, 709) that is provided in a conduction path between the reverse connection protection circuit and the motor drive unit, includes: a charging step of turning the motor drive unit off and turning the reverse connection protection circuit on, thereby applying a voltage from the power source to charge the capacitor until it reaches a predetermined voltage, and then stopping the charging as the charging is completed; an ON fault determination step of determining an ON fault of the reverse connection protection circuit based on a first voltage between the reverse connection protection circuit and the capacitor and a second voltage between the reverse connection protection circuit and the power supply cut-off circuit in a state in which the reverse connection protection circuit is switched so that a current does not flow from the capacitor side to the power supply side after the capacitor has been charged, an OFF fault determination step of determining an OFF fault of the reverse connection protection circuit based on the first voltage and the second voltage in a state in which the reverse connection protection circuit is switched so that a current flows from the capacitor side to the power supply cut-off circuit side after the capacitor has been charged, and a determination step of determining that an abnormality has occurred in the capacitor or the motor drive unit in response to the first voltage falling below a predetermined threshold or charging not being completed within a predetermined time while the capacitor is being charged in the charging step. This configuration makes it possible to easily perform fault diagnosis of a device including a reverse connection protection circuit.

[0102] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0103] This application is based on a Japanese patent application (Patent Application No. 2024-072691) filed on April 26, 2024, the contents of which are incorporated herein by reference.

[0104] 100... Power supply connection circuit 101, 102... Switching element 103... Capacitor 104... Three-phase bridge circuit 700... Electric power steering device 701... CPU (Central Processing Unit) 702... FET drive circuit 703... Current detection circuit 704... Motor cut-off circuit 705... Motor rotation angle detection circuit 706... Battery 707... Power supply cut-off circuit 708... Reverse connection protection circuit 709... Capacitor 710... Inverter 711a to 711f... FET (Field Effect Transistor) 712a to 712c... Current sensor 713... Terminal voltage detector 714a to 714f... Resistor 715a to 715c... Switching circuit 716... Motor 717... Rotation angle sensor

Claims

1. A fault diagnosis device for a motor device having: a motor; a motor drive unit that outputs drive power to the motor; a power supply interruption circuit that is connected to a power supply and configured to be able to switch its conduction state; a reverse connection protection circuit that is connected to the power supply interruption circuit and the motor drive unit and configured to be able to switch its conduction state; and a capacitor provided in the conduction path between the reverse connection protection circuit and the motor drive unit, wherein the device has a charging unit that turns the motor drive unit off and then turns the reverse connection protection circuit on, thereby charging the capacitor up to a predetermined voltage by applying voltage from the power supply and then stopping the charging as the charging is completed; and an ON fault determination unit that, after charging the capacitor, determines an ON fault of the reverse connection protection circuit based on a first voltage between the reverse connection protection circuit and the capacitor and a second voltage between the reverse connection protection circuit and the power supply interruption circuit in a state where the reverse connection protection circuit is switched so that no current flows from the capacitor to the power supply after the reverse connection protection circuit has been switched on. an OFF fault determination unit that determines an OFF fault of the reverse connection protection circuit based on the first voltage and the second voltage in a state in which the reverse connection protection circuit is switched so that a current flows from the capacitor side to the power supply cutoff circuit side after the capacitor has been charged; and a determination unit that determines that an abnormality has occurred in the capacitor or the motor drive unit when the first voltage falls below a predetermined threshold value or charging is not completed within a predetermined time while the capacitor is being charged by the charging unit.

2. The fault diagnosis device according to claim 1, wherein, if the first voltage falls below a predetermined threshold during the determination process by the ON fault determination unit and the OFF fault determination unit, the charging unit causes the capacitor to be charged again, and causes the ON fault determination unit and the OFF fault determination unit to perform the determination process.

3. The fault diagnosis device according to claim 1, wherein the ON fault determination unit determines that the reverse connection protection circuit has an ON fault when a state in which the second voltage is greater than the difference between the first voltage and a predetermined margin value continues for a first duration.

4. The fault diagnosis device according to claim 1, wherein the OFF fault determination unit determines that the reverse connection protection circuit has an OFF fault when the second voltage remains smaller than a predetermined margin value for a second duration.

5. The fault diagnosis device according to claim 1, wherein the power supply cutoff circuit and the reverse connection protection circuit are configured with FETs (Field Effect Transistors), and the source of the power supply cutoff circuit and the source of the reverse connection protection circuit are connected.

6. The fault diagnosis device according to claim 1, wherein the motor device is an electric power steering device.

7. A fault diagnosis method for a motor device having a motor, a motor drive unit that outputs drive power to the motor, a power supply interruption circuit connected to a power source and configured to be able to switch its conduction state, a reverse connection protection circuit connected to the power supply interruption circuit and the motor drive unit and configured to be able to switch its conduction state, and a capacitor provided in the conduction path between the reverse connection protection circuit and the motor drive unit, comprising: a charging step of turning the motor drive unit off and then turning the reverse connection protection circuit on, thereby charging the capacitor to a predetermined voltage by applying a voltage from the power source, and then stopping the charging as the charging is completed; and an ON fault determination step of determining an ON fault of the reverse connection protection circuit based on a first voltage between the reverse connection protection circuit and the capacitor and a second voltage between the reverse connection protection circuit and the power supply interruption circuit, after the capacitor has been charged, in a state in which the reverse connection protection circuit is switched so that no current flows from the capacitor to the power source. a fault diagnosis method comprising: an OFF fault determination step of determining an OFF fault of the reverse connection protection circuit based on the first voltage and the second voltage in a state in which, after the capacitor has been charged, the reverse connection protection circuit has been switched so that a current flows from the capacitor side to the power supply cutoff circuit side; and a determination step of determining that an abnormality has occurred in the capacitor or the motor drive unit in response to the first voltage falling below a predetermined threshold value or charging not being completed within a predetermined time while the capacitor is being charged in the charging step.

8. A computer for controlling a motor device having a motor, a motor drive unit that outputs drive power to the motor, a power supply cutoff circuit connected to a power source and configured to be able to switch its conduction state, a reverse connection protection circuit connected to the power supply cutoff circuit and the motor drive unit and configured to be able to switch its conduction state, and a capacitor provided in the conduction path between the reverse connection protection circuit and the motor drive unit, includes: a charging step of turning the motor drive unit off and then turning the reverse connection protection circuit on, thereby charging the capacitor to a predetermined voltage by applying a voltage from the power source, and then stopping the charging as the charging is completed; and an ON failure determination step of determining an ON failure of the reverse connection protection circuit based on a first voltage between the reverse connection protection circuit and the capacitor and a second voltage between the reverse connection protection circuit and the power supply cutoff circuit, after the capacitor has been charged, with the reverse connection protection circuit switched so that no current flows from the capacitor to the power source. a determination step of determining an OFF fault of the reverse connection protection circuit based on the first voltage and the second voltage in a state in which the reverse connection protection circuit is switched so that a current flows from the capacitor side to the power supply cutoff circuit side after the capacitor has been charged; and a determination step of determining that an abnormality has occurred in the capacitor or the motor drive unit in response to the first voltage falling below a predetermined threshold value or charging not being completed within a predetermined time while the capacitor is being charged in the charging step.

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