JP2018207685A - Motor controller - Google Patents

Abstract

To provide a motor controller capable of detecting failure of a driving circuit at high speed.SOLUTION: An ECU (a failure determination part) determines whether a duty ratio D is larger than a duty ratio threshold value D0 and an actual current value I is less than an actual current threshold value I0 when a motor estimation rotation speed ω is less than a rotation speed threshold value ω0 (YES in step S2)(step S3). The ECU determines whether a failure detection count CNT is equal to a failure detection count threshold value Th1 or more by adding the failure detection count CNT (step S4) when the duty ratio D is larger than the duty ratio threshold value D0, and the actual current value I is less than the actual current threshold value I0 (YES in step S3)(step S5). The ECU detects an open failure of an FET when the failure detection count CNT is equal to a first failure detection count threshold value Th1 or more (YES in step S5)(step S6).SELECTED DRAWING: Figure 5

Description

  The present invention relates to a motor control device.

  2. Description of the Related Art Conventionally, a steering device that assists a driver's steering operation by applying a driving force of a motor to a steering mechanism of a vehicle is known. For example, Patent Document 1 discloses a motor control device that controls driving of a motor based on steering torque applied to a steering mechanism by a driver. The motor control device calculates a current command value as a target value of the assist force to be applied to the steering mechanism based on the steering torque, and controls the drive circuit based on the current command value to thereby obtain a current applied to the motor. Control.

  The motor control device detects that a failure has occurred in the drive circuit when the actual current value that actually flows through the motor is smaller, even though the current command value is set to a larger value. To do.

JP2015-104956A

  By the way, when it is attempted to detect that a failure has occurred in the drive circuit based on the above-described failure determination condition, it is necessary to ensure a sufficient time until the failure is determined. This is because the failure determination condition may be temporarily satisfied even in a normal state where no failure has occurred in the drive circuit.

  Here, when one switching element of the drive circuit fails, it is not possible to energize the failed system side, but it is possible to energize the other non-failed system side. For this reason, when the driver performs a steering operation in one steering direction, the assist by the motor torque is possible, but when the steering operation is performed in the other steering direction, the assist by the motor torque cannot be performed. For this reason, the left-right difference of the assist force due to the motor torque is large. As described above, in order to detect the failure of the drive circuit more accurately, it is necessary to ensure a sufficient time for the failure detection, but it is not preferable that the situation where the left-right difference of the assist force is large continues for a long time. . For this reason, there has been a demand for a method for more quickly detecting a failure in a drive circuit that causes a difference in left and right assist force.

  Note that, in any motor device, not limited to the steering device, it is preferable to detect the failure of the drive circuit more quickly when a left-right difference in motor torque generated by the motor occurs.

  An object of the present invention is to provide a motor control device that can more quickly detect a failure of a drive circuit.

  The motor control device that can achieve the above object includes a drive circuit that supplies electric power to the motor, a current detection unit that detects an actual current value supplied from the drive circuit to the motor, and the state control unit according to various state quantities. A current command value calculation unit that calculates a current command value that is a target of the actual current value to be applied to the motor; a feedback control unit that performs current feedback control that causes the actual current value to follow the current command value; and When the inter-terminal voltage is less than the inter-terminal voltage threshold, there is a predetermined situation where the actual current value is smaller than the actual current value threshold even though the current command value is set to a value larger than the command threshold. And a determination unit that determines failure of the drive circuit based on whether or not the time continues.

  According to this configuration, although the current command value is set to a larger value, the situation in which the actual current value is a small value is not only when the drive circuit fails but also temporarily during normal operation. May occur. However, during normal operation, when the current command value is set to a large value, the voltage between the terminals of the motor increases. For this reason, even when the current command value is set to a large value, the situation where the actual current value is a small value is less likely to include the normal time. This makes it possible to set the determination time “whether or not it continues for a predetermined time” to be shorter, so that a failure in the drive circuit can be detected more quickly. It is also possible to take measures for eliminating the left-right difference in motor torque more quickly.

  In the motor control device described above, the motor control device includes a rotation speed estimation unit that calculates an estimated rotation speed that is a value obtained by estimating the rotation speed of the motor based on the voltage between the terminals of the motor, and the determination unit uses the voltage between the terminals. If the estimated rotation speed is used instead, the rotation speed threshold is used instead of the voltage threshold between the terminals, and the estimated rotation speed is less than the rotation speed threshold, the current command value is set to a value larger than the command threshold. Nevertheless, the failure of the drive circuit may be determined based on whether or not the situation where the actual current value is smaller than the actual current value threshold value continues for a predetermined time.

  According to this configuration, during normal operation, when the current command value is set to a large value, the voltage between the terminals of the motor increases. Therefore, the estimated rotation speed estimated based on the voltage between the terminals exceeds the rotation speed threshold. . For this reason, even when the estimated rotational speed is less than the rotational speed threshold and the current command value is set to a large value, the situation where the actual current value is a small value is less likely to include the normal time. . This makes it possible to set the determination time “whether or not it continues for a predetermined time” to be shorter, so that a failure in the drive circuit can be detected more quickly.

  In the motor control device described above, when the estimated rotation speed is less than a rotation speed threshold, the predetermined time is set as a first threshold, a failure of the drive circuit is determined, and the estimated rotation speed is set to the rotation speed threshold. In the case described above, it is preferable to determine the failure of the drive circuit by setting the predetermined time to a second threshold value that is larger than the first threshold value.

  According to this configuration, when the estimated rotation speed is less than the rotation speed threshold, the failure of the drive circuit is determined more quickly by setting the predetermined time to the first threshold, and the estimated rotation speed is determined to be the rotation speed. If it is equal to or greater than the threshold value, the failure of the drive circuit can be more reliably determined by setting the predetermined time to the second threshold value. Note that when the estimated rotational speed is equal to or higher than the rotational speed threshold value, it is included even in the normal state, but in the normal state, the actual current value is decreased even though the current command value is set large. Therefore, it is possible to make a determination by setting a long predetermined time for determining a failure of the drive circuit.

  In the motor control device, the estimated rotational speed is calculated in proportion to a difference obtained by subtracting a product of a resistance and a current value, which are constants set based on the actual current value, from the voltage between the terminals of the motor. It is preferable.

  According to this configuration, the estimated rotation speed is calculated based on the voltage between the terminals, so that even if the current command value is set to a large value, the estimated rotation speed can be reduced. When the speed is less than the rotation speed threshold, the case where the drive circuit is normal is not included. Thereby, the predetermined time can be further shortened.

  In the motor control device, when the estimated rotation speed is less than the rotation speed threshold, the determination unit determines that the actual current value is set even though the current command value is set to a value larger than the command threshold. Is preferably smaller than the actual current value threshold, it is preferable to determine an open failure of any one of the switching elements provided in the drive circuit.

  According to this configuration, it is possible to take measures to eliminate the left-right difference in the motor torque by determining whether there is a left-right difference in the motor torque by determining an open failure of the switching element provided in the drive circuit. become.

  In the motor control device described above, the switching element of the drive circuit is turned on / off based on the duty ratio of the PWM signal output by the feedback control unit, and when the duty ratio is larger than a duty ratio threshold, the current command When the value is set to a value larger than the command threshold, and when the actual current value is smaller than the actual current value threshold, the actual current value is smaller than the actual current value threshold. The determination unit is predetermined when the count added when the duty ratio is larger than the duty ratio threshold and the actual current value is smaller than the actual current value threshold exceeds a count threshold. It is preferable to determine that the time has continued.

  According to this configuration, when the estimated rotational speed is less than the rotational speed threshold, the count is added when the duty ratio is larger than the duty ratio threshold and the actual current value is smaller than the actual current value threshold. When the count exceeds the count threshold, a failure of the drive circuit is detected.

  In the motor control device, the determination unit is configured such that the inter-terminal voltage is less than the inter-terminal voltage threshold, the current command value is set to a value larger than the command threshold, and the actual current value is the actual current. In addition to basic determination conditions including a value smaller than a value threshold, the upstream terminal voltage and downstream terminal voltage of the motor are smaller than a first power supply voltage threshold, and the upstream terminal voltage and downstream of the motor Whether the determination is made using an additional determination condition including at least one of the side terminal voltage being greater than the second power supply voltage threshold, and a situation in which both the basic determination condition and the additional determination condition are satisfied continues for a predetermined time It is preferable to determine the failure of the drive circuit based on whether or not.

  According to this configuration, even if a situation in which the actual current value is a small value occurs even though the current command value is set to a larger value due to the influence of the counter electromotive voltage, the upstream terminal of the motor Unless the voltage and the downstream terminal voltage are smaller than the first power supply voltage threshold or the upstream terminal voltage and the downstream terminal voltage of the motor are larger than the second power supply voltage threshold, Does not detect drive circuit failure. For this reason, the failure of the drive circuit can be detected more reliably.

  According to the motor control device of the present invention, the failure of the drive circuit can be detected more quickly.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the electric power steering apparatus by which the motor control apparatus of 1st Embodiment is mounted. The control block diagram in the motor control device of a 1st embodiment. (A) is a figure which shows the electric power feeding state to the motor at the time of steering to the normal direction at the time of normal, (b) is a figure which shows the electric power feeding state to the motor at the time of the steering to the reverse direction at the time of normal. (A) is a figure which shows the electric power feeding state to the motor at the time of the steering in the forward direction at the time of the failure of a switching element, (b) is the motor at the time of the steering at the reverse direction at the time of a failure of a switching element The figure which shows the electric power feeding state to. 5 is a flowchart illustrating a drive circuit failure detection method in the motor control apparatus according to the first embodiment. (A) is a figure which shows the electric power feeding state to the motor at the time of the steering in the positive direction at the time of failure of a motor connector, (b) is the motor control apparatus of one Embodiment, The figure which shows the electric power feeding state to the motor at the time of the steering in a reverse direction. The figure which shows the electric power feeding state to the motor at the time of the steering in the forward / reverse direction when the disconnection failure of the ground has occurred. The flowchart which shows the failure detection method of a drive circuit in the motor control apparatus of 2nd Embodiment. The motor control apparatus of 3rd Embodiment WHEREIN: The flowchart which shows the failure detection method of a drive circuit.

<First Embodiment>
Hereinafter, a first embodiment in which the motor control device is applied to an electric power steering device will be described.

  As shown in FIG. 1, the EPS 1 (electric power steering device) includes a steering mechanism 2 that steers the steered wheels 18 based on an operation of the steering wheel 10 of the driver, an EPS actuator 3 that assists the steering operation of the driver, And an ECU 30 (electronic control unit) as a motor control unit for controlling the EPS actuator 3.

  The steering mechanism 2 includes a steering wheel 10 and a steering shaft 11 that rotates integrally with the steering wheel 10. The steering shaft 11 includes a column shaft 12 connected to the steering wheel 10, an intermediate shaft 13 connected to the lower end portion of the column shaft 12, and a pinion shaft 14 connected to the lower end portion of the intermediate shaft 13. Yes. A lower end portion of the pinion shaft 14 is connected to a rack shaft 15 that is a steered shaft via a rack and pinion mechanism 16. Therefore, in the steering mechanism 2, the rotational movement of the steering shaft 11 is performed by the axis of the rack shaft 15 via the rack and pinion mechanism 16 including a pinion provided at the tip of the pinion shaft 14 and a rack provided on the rack shaft 15. It is converted into a reciprocating linear motion in the direction (left-right direction in FIG. 1). The reciprocating linear motion is transmitted to the left and right steered wheels 18 via tie rods 17 connected to both ends of the rack shaft 15, respectively, so that the steered angle of the steered wheels 18 is changed.

  The EPS actuator 3 includes a motor 20 that applies assist force to the steering shaft 11 and a speed reducer 21. The motor 20 is a DC motor with a brush. A rotation shaft of the motor 20 is connected to the column shaft 12 via a speed reducer 21. The speed reducer 21 transmits the output torque (rotational force) of the motor 20 to the column shaft 12. The reduction gear 21 has a wheel gear 22 connected to the column shaft 12 and a worm gear 23 connected to the motor 20 and meshing with the wheel gear 22. The rotation of the motor 20 is decelerated by the speed reducer 21, and the rotational force of the decelerated motor 20 is transmitted as an assist force to the steering shaft 11, thereby assisting the driver's steering operation.

  The ECU 30 controls the motor 20 based on detection results of various sensors provided in the vehicle. As various sensors, for example, a torque sensor 41 and a vehicle speed sensor 42 are provided. The torque sensor 41 is provided on the column shaft 12. The torque sensor 41 detects a steering torque τ applied to the steering shaft 11 in accordance with the driver's steering operation. The vehicle speed sensor 42 detects a vehicle speed V that is the traveling speed of the vehicle. The ECU 30 controls the drive power supplied to the motor 20 based on the output of each sensor.

Next, the configuration of the ECU 30 will be described in detail.
As shown in FIG. 2, the ECU 30 includes a current detection unit 31, a current command value calculation unit 33, a PI calculation unit 34 (control unit), a drive circuit 35, and a motor rotation speed estimation unit 36 (rotation speed estimation unit). ) And a failure determination unit 37 (determination unit).

The current command value calculation unit 33 calculates a current command value I * based on the steering torque τ detected by the torque sensor 41 and the vehicle speed V detected by the vehicle speed sensor 42.
The drive circuit 35 is an H-type bridge circuit including FETs 35A to 35D that are switching elements. The drive circuit 35 is provided between the battery B and the ground Gnd. As the FETs 35A to 35D, for example, MOS-FETs (Metal Oxide Semiconductor Field Effect Transistors) are employed. Two FETs 35A and 35C are connected in series, and two FETs 35B and 35D are connected in series. The FETs 35A and 35C and the FETs 35B and 35D are connected in parallel.

  The FETs 35A to 35D are switched between the OFF state and the ON state based on the PWM signal Sp. When the FETs 35A and 35D are turned on and the FETs 35B and 35C are turned off, the motor 20 rotates in the positive direction. Further, when the FETs 35B and 35C are in the ON state and the FETs 35A and 35D are in the OFF state, the motor 20 rotates in the reverse direction. As described above, the rotation direction of the motor 20 is switched by switching the FETs 35A to 35D to the ON state or the OFF state. Further, the torque of the motor 20 is controlled by the ratio of the time during which the FETs 35A to 35D are maintained in the OFF state and the period during which the FET 35 is maintained in the ON state, that is, the duty ratio of the PWM signal Sp.

  The current detection unit 31 includes a current sensor 32 and a resistor R. The resistor R is provided between the drive circuit 35 and the ground Gnd. The current sensor 32 is electrically connected to both ends of the resistor R. The current sensor 32 detects the current (actual current value I) flowing through the motor 20 by detecting the current flowing through the resistor R. Then, the current sensor 32 outputs the detected actual current value I to the PI calculation unit 34.

  The PI calculation unit 34 generates the PWM signal Sp based on the current command value I * calculated by the current command value calculation unit 33 and the actual current value I detected by the current sensor 32, and the generated PWM signal Sp is output to the FETs 35 </ b> A to 35 </ b> D of the drive circuit 35. On and off of the FETs 35 </ b> A to 35 </ b> D are switched based on the PWM signal Sp generated by the PI calculation unit 34.

  The motor rotation speed estimation unit 36 acquires the terminal voltage Vm of the motor 20. The inter-terminal voltage Vm is the difference between the voltage V1 at the terminal M1 and the voltage V2 at the terminal M2. The motor rotation speed estimation unit 36 estimates the motor estimated rotation speed ω based on the voltage Vm between the terminals of the motor 20. That is, the motor rotation speed estimation unit 36 calculates the motor estimated rotation speed ω based on the following equation (1).

Motor estimated rotational speed ω = [(terminal voltage Vm−motor resistance × current) / back electromotive force constant] (1)
In Equation (1), the motor resistance and current are constants set based on the value of the current that actually flows through the motor 20 when the current flows through the motor 20. The counter electromotive voltage constant is determined by the specifications of the motor 20 and is determined based on the relationship between the voltage applied to the motor 20 (rotational speed of the motor) and the counter electromotive voltage generated in the motor 20. The inter-terminal voltage Vm is a value detected when the FETs 35A and 35D of the drive circuit 35 are in the ON state or the FETs 35B and 35C are in the ON state.

  The failure determination unit 37 takes in the duty ratio D calculated by the PI calculation unit 34, the actual current value I detected by the current sensor 32, and the estimated motor rotation speed ω detected by the motor rotation speed estimation unit 36. The duty ratio D is the sum of the duty ratios of the FETs 35A and 35D or the sum of the duty ratios of the FETs 35B and 35C. Further, the failure determination unit 37 includes, as various threshold values, for example, a rotation speed threshold value ω0 that is a threshold value of the motor estimated rotation speed ω, a duty ratio threshold value D0 that is a threshold value of the duty ratio D, and a threshold value of the actual current value I. The actual current value threshold I0 and the first and second failure detection count thresholds Th1 and Th2 are fetched from a memory (not shown). The duty ratio threshold D0 is set to 200%, which is the sum of the maximum duty ratios (100%) of the FETs 35A and 35D, or 200%, which is the sum of the maximum duty ratios (100%) of the FETs 35B and 35C, for example. The Further, for example, 5A is adopted as the actual current value threshold I0. The failure determination unit 37 includes a duty ratio, an actual current value I, a motor estimated rotation speed ω, a rotation speed threshold ω0, a duty ratio threshold D0, an actual current value threshold I0, and a first failure detection count threshold Th1 (first threshold). And a failure of the drive circuit 35 is detected based on the second failure detection count threshold Th2 (second threshold). Examples of the failure of the drive circuit 35 include an open failure of the FETs 35 </ b> A to 35 </ b> D and a disconnection failure of the drive circuit 35.

  When the failure determination unit 37 detects a failure of the drive circuit 35, the PI calculation unit 34 stops the assist function in the EPS 1 by, for example, stopping generation of a PWM signal.

Next, a power supply state to the motor 20 by the drive circuit 35 will be described.
First, with reference to FIGS. 3A and 3B, a power supply state to the motor 20 in a normal state in which no failure has occurred in the drive circuit 35 will be described.

  As shown in FIG. 3A, when the steering wheel 10 is steered in the forward direction by the driver, an assist force is required in the forward direction. Therefore, it is necessary to rotate the motor 20 in the forward direction. The ECU 30 turns the FETs 35A, 35D on and the FETs 35B, 35C off to rotate the motor 20 in the forward direction. As a result, the actual current value I flows between the terminals M1 and M2 of the motor 20. In this case, a counter electromotive voltage Fc is generated as the motor 20 rotates. The counter electromotive voltage Fc is a voltage that attempts to flow a current in a direction opposite to the direction in which the actual current value I flows. When the back electromotive voltage Fc becomes larger than the power supply voltage Vp of the battery B, the terminal M1 of the motor 20 is connected even though the voltage V2 of the upstream terminal M2 is almost the same as the power supply voltage Vp of the battery B. The actual current value I does not flow during M2. For this reason, when the counter electromotive voltage Fc is equal to or higher than the power supply voltage Vp of the battery B, the motor 20 cannot be rotated in the forward direction even when the steering wheel 10 is steered in the forward direction. The steering operation cannot be fully assisted. On the other hand, when the back electromotive voltage Fc is smaller than the power supply voltage Vp of the battery B, the steering operation is assisted because the motor 20 can be rotated in the forward direction when the steering wheel 10 is steered in the forward direction. can do. The inter-terminal voltage Vm is generated regardless of the magnitude of the back electromotive voltage Fc. When the counter electromotive voltage Fc increases as the duty ratio increases, the inter-terminal voltage Vm also increases, so that the estimated motor rotation speed ω is greater than, for example, the rotation speed threshold ω0.

  Next, as shown in FIG. 3 (b), when the steering wheel 10 is steered in the reverse direction by the driver, an assist force is required in the reverse direction. Therefore, it is necessary to rotate the motor 20 in the reverse direction. . The ECU 30 turns the FETs 35B and 35C on and the FETs 35A and 35D off to rotate the motor 20 in the reverse direction. As a result, the actual current value I flows between the terminals M1 and M2 of the motor 20. The actual current value I flows in the opposite direction to the actual current value I in the case of FIG. Similarly in this case, when the counter electromotive voltage Fc becomes larger than the power supply voltage Vp of the battery B, the voltage V1 of the upstream terminal M1 is almost the same as the power supply voltage Vp of the battery B. Since the downstream terminal M2 becomes almost the same as the ground voltage of the ground Gnd, the actual current value I does not flow between the terminals M1 and M2 of the motor 20. For this reason, when the back electromotive voltage Fc is equal to or higher than the power supply voltage Vp of the battery B, the motor 20 cannot be rotated in the reverse direction even when the steering wheel 10 is steered in the reverse direction. The steering operation cannot be fully assisted. On the other hand, when the back electromotive voltage Fc is smaller than the power supply voltage Vp of the battery B, the steering operation is assisted because the motor 20 can be rotated in the reverse direction when the steering wheel 10 is steered in the reverse direction. can do. Even in this case, the inter-terminal voltage Vm is generated. When the counter electromotive voltage Fc increases as the duty ratio D increases, the inter-terminal voltage Vm similarly increases, so that the estimated motor rotation speed ω is greater than, for example, the rotation speed threshold ω0.

  As described above, the voltage Vm between the terminals of the motor 20 is normal regardless of whether the steering wheel 10 is rotated in the forward direction or the steering wheel 10 is rotated in the reverse direction when there is no failure in the drive circuit 35. Can be detected. Therefore, for example, when the failure determination condition that “the duty ratio D is greater than the duty ratio threshold D0 and the actual current value I is less than the actual current value threshold I0” is satisfied, the inter-terminal voltage Vm increases. The estimated motor rotation speed ω becomes larger than the rotation speed threshold value ω0.

Next, with reference to FIGS. 4A and 4B, the power supply state to the motor 20 at the time of abnormality in which an open failure has occurred in the FET 35A of the drive circuit 35 will be described.
As shown in FIG. 4A, when the steering wheel 10 is steered in the forward direction by the driver, the ECU 30 needs an assist force in the forward direction. Therefore, in order to rotate the motor 20 in the forward direction, The FETs 35A and 35D are turned on, and the FETs 35B and 35C are turned off. As a result, the ECU 30 attempts to cause the actual current value I to flow between the terminals M1 and M2 of the motor 20. However, since an open failure has occurred in the FET 35A, the power supply path from the battery B to the motor 20 is blocked by the FET 35A even though the FET 35A is in the ON state. Since the actual current value I cannot flow between the terminals M1 and M2 of the motor 20, the motor 20 cannot be rotated in the positive direction, and the steering operation cannot be assisted sufficiently. In this case, since an open failure has occurred in the FET 35A, the actual current value I does not flow in the first place, and the voltages V1 and V2 of the terminals M1 and M2 of the motor 20 are almost the same (both voltages V1 and V2 are “0V”). ")become. Since the voltages V1 and V2 of the terminals M1 and M2 of the motor 20 are almost the same, the voltage Vm between the terminals is almost zero, and the estimated motor rotation speed ω is also almost zero.

  On the other hand, as shown in FIG. 4B, the ECU 30 rotates the motor 20 in the reverse direction because an assist force is required in the reverse direction when the steering wheel 10 is steered in the reverse direction by the driver. Therefore, the FETs 35B and 35C are turned on and the FETs 35A and 35D are turned off. As a result, the ECU 30 tries to pass a current between the terminals M1 and M2 of the motor 20. As in the case of FIG. 3B, when the steering wheel 10 is steered in the reverse direction, the power supply path from the battery B to the motor 20 is not interrupted, and therefore, between the terminals M1 and M2 of the motor 20. The actual current value I flows through Until the counter electromotive voltage Fc becomes equal to or higher than the power supply voltage Vp of the battery B, the steering operation can be assisted because the motor 20 can be rotated in the reverse direction when the steering wheel 10 is steered in the reverse direction. it can. In this case, since the voltage Vm between the terminals can be detected, when the counter electromotive voltage Fc becomes equal to or higher than the power supply voltage Vp of the battery B as the duty ratio D increases, the estimated motor rotational speed ω is For example, it becomes larger than the rotation speed threshold value ω0.

  As described above, when an open failure occurs in the FET 35A of the drive circuit 35, it is not possible to assist sufficiently when the steering wheel 10 is steered in the forward direction, but normally when the steering wheel 10 is steered in the reverse direction. It is possible to assist the street (as in the case where there is no failure). For this reason, the left-right difference in assist force (motor torque) when the steering wheel 10 is steered in the left-right direction (forward / reverse direction) increases.

  When an open failure occurs in the FET 35B, it is possible to assist normally when the steering wheel 10 is steered in the forward direction, but it is possible to assist sufficiently when the steering wheel 10 is steered in the reverse direction. Can not. As described above, when an open failure occurs in any one of the FETs 35 </ b> A to 35 </ b> D, the left-right difference in assist force when the steering wheel 10 is steered in the left-right direction becomes large.

Next, a failure detection method for the drive circuit 35 will be described.
As shown in the flowchart of FIG. 5, the ECU 30 (motor rotation speed estimation unit) calculates a motor estimated rotation speed ω (step S1). Here, the terminal voltage Vm is used to estimate the rotational speed of the motor 20.

  Next, the ECU 30 (failure determination unit 37) determines whether or not the motor estimated rotational speed ω is less than the rotational speed threshold ω0 (step S2). That is, it is determined whether or not the motor 20 is rotating at a high speed based on the estimated motor speed ω that reflects the voltage Vm between the terminals. The rotation speed threshold value ω0 is set to a low rotation speed that is about 2500 degrees per second, that is, the motor 20 rotates several times per second.

  When the estimated motor rotation speed ω is less than the rotation speed threshold ω0 (YES in step S2), the ECU 30 (failure determination unit 37) determines that the duty ratio D is greater than the duty ratio threshold D0 and the actual current value I is the actual current. It is determined whether the value is less than the threshold value I0 (step S3).

  When the duty ratio D is greater than the duty ratio threshold D0 and the actual current value I is less than the actual current value threshold I0 (YES in step S3), the ECU 30 (failure determination unit 37) adds the failure detection count CNT. (Step S4), it is determined whether or not the failure detection count CNT is greater than or equal to the first failure detection count threshold Th1 (Step S5). The case where the duty ratio D is larger than the duty ratio threshold value D0 and the actual current value I is less than the actual current value threshold value I0 is actually a sufficient current even though the motor 20 is trying to pass a current. Is not flowing.

  When the failure detection count CNT is equal to or greater than the first failure detection count threshold Th1 (YES in step S5), the ECU 30 (failure determination unit 37) detects an open failure of the FET (step S6). In this case, it is considered that a situation in which sufficient current does not actually flow though the motor 20 is caused to flow further is not temporary. Therefore, any open failure of the FETs 35A to 35D Alternatively, it is considered that the current path in the drive circuit 35 is disconnected.

In contrast, when the failure detection count CNT is less than the first failure detection count threshold Th1 (NO in step S5), the ECU 30 (failure determination unit 37) ends the process.
Further, the ECU 30 (failure determination unit 37) resets the failure detection count CNT when the duty ratio D is equal to or less than the duty ratio threshold D0 or the actual current value I is equal to or greater than the actual current value threshold I0 (NO in step S3). (Step S7), the process ends.

  When the estimated motor rotation speed ω is equal to or higher than the rotation speed threshold (NO in step S2), the ECU 30 (failure determination unit 37) determines that the duty ratio D is greater than the duty ratio threshold D0 and the actual current value I is the actual current value. It is determined whether or not the threshold value is less than I0 (step S8).

  When the duty ratio D is greater than the duty ratio threshold D0 and the actual current value I is less than the actual current value threshold I0 (YES in step S8), the ECU 30 (failure determination unit 37) adds the failure detection count CNT. (Step S9), it is determined whether or not the failure detection count CNT is greater than or equal to the second failure detection count threshold Th2 (Step S10). Note that the second failure detection count threshold Th2 is set to be larger than the first failure detection count threshold Th1.

  When the failure detection count CNT is greater than or equal to the second failure detection count threshold Th2 (YES in step S10), the ECU 30 (failure determination unit 37) detects a failure in the drive circuit 35 (step S11). Examples of the failure of the drive circuit 35 include an open failure of a motor connector and a disconnection failure of the ground Gnd.

On the other hand, when the failure detection count CNT is less than the second failure detection count threshold Th2 (NO in step S10), the ECU 30 (failure determination unit 37) ends the process.
Further, the ECU 30 (failure determination unit 37) resets the failure detection count CNT when the duty ratio D is equal to or less than the duty ratio threshold D0 or the actual current value I is equal to or greater than the actual current value threshold I0 (NO in step S8). (Step S12).

The process ends here.
The operation and effect of this embodiment will be described.
(1) As a comparative example, a failure of the drive circuit 35 is determined based on a failure determination condition (whether the duty ratio D is larger than the duty ratio threshold D0 and the actual current value I is less than the actual current value threshold I0). In the case of detection, a sufficient time for detecting the failure of the drive circuit 35 (a time required for the failure detection count CNT to reach the second failure detection count threshold Th2) is required. This is because the failure determination condition may be temporarily satisfied when the back electromotive voltage Fc is generated with the steering operation. For this reason, the failure of the drive circuit 35 has been determined when the failure determination condition is satisfied for a long time such as 4 seconds. It should be noted that it is not normally considered that the situation where the failure determination condition is satisfied for a long time is continued at the normal time.

  However, when an open failure of any one of the FETs 35 </ b> A to 35 </ b> D of the drive circuit 35 and a disconnection failure of the current path of the drive circuit 35 occur, the left-right difference in assist force when steering the steering wheel 10 in the left-right direction is large. turn into. For this reason, in the method of the comparative example, until the failure determination condition is satisfied, the left-right difference of the assist force when the steering operation is performed is large, and the driver's comfort of the steering operation is impaired. End up.

  In this regard, in the present embodiment, although a failure of the drive circuit 35 is detected based on the fact that the failure determination condition is satisfied, if the estimated motor rotation speed ω is smaller than the rotation speed threshold value ω0, the drive is performed in a shorter time. The failure of the circuit 35 is confirmed. That is, in the present embodiment, in order to detect that the failure determination condition has been satisfied for a predetermined time, the failure detection count CNT has a threshold value (first failure detection count threshold Th1 or second failure detection count threshold Th2). When it exceeds, a failure of the drive circuit 35 is detected. As this threshold value becomes smaller, the number of times that the failure determination condition should be satisfied when detecting a failure of the drive circuit 35 is reduced, so that the failure can be detected in a shorter time (for example, several tens of milliseconds shorter than 4 seconds). It becomes possible. In the present embodiment, the first failure detection count threshold Th1 used when the motor estimated rotation speed ω is larger than the rotation speed threshold ω0 is the second failure detection count threshold Th1 used when the motor estimated rotation speed ω is equal to or less than the rotation speed threshold ω0. Is set smaller than the failure detection count threshold Th2. For this reason, it becomes possible to detect the failure of the drive circuit 35 more quickly.

  In addition, when the motor estimated rotational speed ω is equal to or higher than the rotational speed threshold ω0, a situation in which the actual current value I is difficult to flow due to the counter electromotive voltage Fc is included. On the other hand, when the motor estimated rotational speed ω is less than the rotational speed threshold ω0 and when the failure determination condition is satisfied, the situation where the actual current value I is difficult to flow due to the counter electromotive voltage Fc is not included. For this reason, when the estimated motor rotation speed ω is less than the rotation speed threshold ω 0, it is possible to reduce the number of times to be counted in order to determine the failure. For this reason, since the failure of the drive circuit 35 (for example, any one open failure of the FETs 35A to 35D) can be detected more quickly, the time during which the left / right difference of the assist force is large is reduced. Can do.

  (2) If NO in step S2 of FIG. 5, the process proceeds to determinations in steps S8 to S12. However, in this case, since there is no difference between the left and right assist forces, it is considered that the failure of the drive circuit 35 may be determined over time. For this reason, by setting the second failure detection count threshold value Th2 to be larger than the first failure detection count threshold value Th1, a sufficient time is secured and the failure of the drive circuit 35 is accurately detected.

  For example, as shown in FIGS. 6A and 6B, when an open failure of the motor connector (connection portion of the motor 20 to the drive circuit 35) occurs between the terminal M1 and the terminal M2, The actual current value I does not flow in both the steering operation in the direction and the steering operation in the reverse direction. In this case, the estimated motor rotation speed ω is less than the rotation speed threshold ω0. In this regard, when an open failure of the motor connector has occurred, the situation where the failure determination condition is satisfied continues for the time until the failure detection count CNT exceeds the second failure detection count threshold Th2. For this reason, a failure of the drive circuit 35 can be detected by the determinations in steps S8 to S12 in FIG.

  Further, as shown in FIG. 7, when a disconnection failure of the ground Gnd occurs, no actual current flows in both the forward steering operation and the reverse steering operation. In this case, the estimated motor rotation speed ω is less than the rotation speed threshold ω0. In this regard, when a disconnection failure of the ground Gnd has occurred, the state in which the failure determination condition is satisfied continues for the time until the failure detection count CNT exceeds the second failure detection count threshold Th2. For this reason, a failure of the drive circuit 35 can be detected by the determinations in steps S8 to S12 in FIG.

As described above, various failures of the drive circuit 35 can be detected by the determination process of FIG.
Second Embodiment
Next, a second embodiment in which the motor control device is applied to an electric power steering device will be described. Here, the difference from the first embodiment will be mainly described.

  In the first embodiment, in step S2 of FIG. 5, based on whether the motor estimated rotational speed ω is less than the rotational speed threshold ω0, the threshold of the number of times that the failure determination condition is satisfied is set as the first failure detection count threshold Th1. In contrast to the second failure detection count threshold Th2, the second embodiment does not separate the threshold of the number of times that the failure determination condition is satisfied.

  The failure determination conditions of the present embodiment are that the duty ratio D is larger than the duty ratio threshold D0, the actual current value I is smaller than the actual current value threshold I0, and the motor estimated rotational speed ω is less than the rotational speed threshold ω0. Whether or not.

A failure detection method for the drive circuit 35 in the second embodiment will be described.
As shown in FIG. 8, after step S1, when the failure determination condition is satisfied (YES in step S20), the ECU 30 adds the failure detection count CNT (step S4), and the failure detection count CNT becomes the failure detection count threshold value. It is determined whether or not it is greater than or equal to Th (step S21).

  When the failure detection count CNT is equal to or greater than the failure detection count threshold Th (YES in step S21), the ECU 30 detects an open failure of the FETs 35A to 35D (step S6).

On the other hand, when the failure detection count CNT is less than the failure detection count threshold Th (YES in step S21), the ECU 30 ends the process.
If the failure determination condition is not satisfied after step S1 (NO in step S20), the ECU 30 resets the failure detection count CNT (step S7) and ends the process.

The effect of this embodiment will be described.
(1) When the failure determination condition (D> D0, I <I0, ω <ω0) is satisfied, the situation where the actual current value I is less likely to flow due to the counter electromotive voltage Fc is not included. For this reason, it is possible to reduce the number of times that the failure determination condition is satisfied. For this reason, it is possible to determine and detect a failure of the drive circuit 35 more quickly.

<Third Embodiment>
Next, a third embodiment in which the motor control device is applied to an electric power steering device will be described. Here, the difference from the second embodiment will be mainly described. In the third embodiment, when there is a delay in the responsiveness of the estimated motor rotation speed ω with respect to the actual current value I detected by the current sensor 32, the failure determination condition may be transiently satisfied. It is to suppress.

  The failure determination conditions of the present embodiment are based on the failure determination conditions (D> D0, I <I0, and ω <ω0) of the second embodiment, and the voltages V1, V2 of the terminals M1, M2 and A determination condition using the power supply voltage Vp is added. That is, in this embodiment, even if the failure determination condition of the second embodiment is satisfied, the failure of the drive circuit 35 is not detected and detected unless the added determination condition is satisfied.

  There are two determination conditions to be added. The first additional determination condition is that the voltage V1 at the terminal M1 is smaller than a first power supply voltage threshold (α × Vp) that is a value obtained by multiplying the power supply voltage Vp by a coefficient α, and the voltage V2 at the terminal M2 is One power supply voltage threshold value is smaller. The second additional determination condition is that the voltage V1 at the terminal M1 is larger than a second power supply voltage threshold value (β × Vp) that is a value obtained by multiplying the power supply voltage Vp by the coefficient β, and the voltage V2 at the terminal M2 is , Greater than the second power supply voltage threshold. For example, α is set to “0.15” and β is set to “0.82”.

Next, a failure detection method for the drive circuit 35 will be described.
As shown in FIG. 9, when the basic determination condition is satisfied after step S1 (YES in step S20), the ECU 30 determines whether or not the first additional determination condition is satisfied (step S21).

  When the first additional determination condition is satisfied (YES in step S21), the ECU 30 adds the failure detection count CNT (step S4), and determines whether or not the failure detection count CNT is equal to or greater than the failure detection count threshold Th. (Step S5).

  If the failure detection count CNT is greater than or equal to the failure detection count threshold Th (YES in step S5), the ECU 30 detects a failure in the drive circuit 35 (step S30) and ends the process.

In contrast, when the failure detection count CNT is less than the failure detection count threshold Th (NO in step S5), the ECU 30 ends the process.
In addition, when the first additional determination condition is not satisfied (NO in step S21), the ECU 30 determines whether the second additional determination condition is satisfied (step S22).

When the second additional determination condition is satisfied (YES in step S22), the ECU 30 adds the failure detection count CNT (step S4).
In contrast, if the second additional determination condition is not satisfied (NO in step S22), the ECU 30 resets the failure detection count CNT (step S7) and ends the process.

The operation and effect of this embodiment will be described.
(1) In addition to the basic determination conditions (D> D0, I <I0, and ω <ω0), a failure of the drive circuit 35 is detected based on two additional determination conditions. That is, when the first additional determination condition (V1 <α × Vp and V2 <α × Vp) or the second additional determination condition (V1> β × Vp and V2> β × Vp) is satisfied. On the other hand, when the failure of the drive circuit 35 is detected, when neither the first additional determination condition nor the second additional determination condition is satisfied, the failure of the drive circuit 35 is not detected.

  Incidentally, the response of the estimated motor rotation speed ω may be different from the response of the actual current value I detected by the current sensor 32. This occurs, for example, when a filter process is performed when the estimated motor rotation speed ω is calculated. If the estimated motor speed ω is delayed in response to the actual current value I, the failure judgment condition may be erroneously satisfied in a transient situation where the estimated motor speed ω and the actual current value I change. There is.

  In this respect, in the present embodiment, since the motor estimated rotational speed ω and the actual current value I change depending on the first additional determination condition and the second additional determination condition, the failure determination condition is erroneously set. Even if it is a case where it satisfy | fills, it is suppressed that this is counted. For this reason, it is possible to make the failure detection count threshold Th smaller. Therefore, it is possible to detect a failure in the drive circuit 35 more quickly, and it is possible to detect a failure in the drive circuit 35 that causes a difference in left and right assist force more quickly.

(2) When none of the FETs 35 </ b> A to 35 </ b> D is out of order, it is possible to more reliably detect whether or not the drive circuit 35 is out of order based on the first and second additional determination conditions.
For example, as shown in FIG. 3A, when the steering wheel 10 is steered in the forward direction by the driver, an assist force is required in the forward direction. Therefore, it is necessary to rotate the motor 20 in the forward direction. The ECU 30 causes the actual current value I to flow by turning on the FETs 35A and 35D in order to rotate the motor 20 in the positive direction. When the actual current value I flows, a counter electromotive voltage Fc that prevents the actual current value I from flowing is generated. When the actual current value I cannot flow due to the counter electromotive voltage Fc, the basic determination condition (D> D0, I <I0, and ω <ω0) is satisfied even if none of the FETs 35A to 35D has failed. Sometimes.

  In this regard, when the actual current value I cannot flow due to the back electromotive voltage Fc, the duty ratio (duty ratio D) of the FETs 35A and 35D increases. In this case, the voltage V2 at the terminal M2 is almost equal to the power supply voltage Vp, while the voltage V1 at the terminal M1 is almost equal to “0” (voltage at the ground Gnd). For this reason, the first additional determination condition is not satisfied.

  Similarly, when the steering wheel 10 is steered in the reverse direction by the driver, when the FETs 35 </ b> A to 35 </ b> D are not broken, when the actual current value I cannot be caused to flow by the counter electromotive voltage Fc, the second The additional determination condition is not satisfied.

  As a result, the first and second additions are made even when the basic determination condition (D> D0, I <I0, and ω <ω0) is satisfied transiently by the influence of the counter electromotive voltage Fc. The judgment condition is not satisfied. For this reason, a failure of the drive circuit 35 can be detected more reliably and quickly.

  (3) When the FET 35A or FET 35B (so-called upper MOS-FET) fails, the failure of the drive circuit 35 can be detected more reliably by the first additional determination condition.

  For example, as shown in FIG. 4 (a), when the FET 35A and 35D are turned on so that the ECU 30 rotates the motor 20 in the positive direction, the actual current value I flows when the FET 35A is broken. I can't. Therefore, the ECU 30 increases the duty ratio (duty ratio D) of the FETs 35A and 35D so that the actual current value I flows. In this case, the voltage V1 of the terminal M1 (downstream terminal voltage in this case) is “0 V” almost equal to the voltage V2 of the terminal M2 (upstream terminal voltage in this case). For this reason, since the first additional determination condition is satisfied, a failure of the drive circuit 35 can be detected more reliably.

  When the first additional determination condition is satisfied, it may be determined that a failure has occurred on the upper MOS-FET (FET 35A, 35B) side in the drive circuit 35. That is, by adding the first additional determination condition, it is possible to further specify the faulty part of the drive circuit 35.

  (4) When the FET 35C or FET 35D (so-called lower MOS-FET) fails, the failure of the drive circuit 35 can be detected more reliably by the second additional determination condition.

  For example, when the FETs 35A and 35D are turned on so that the ECU 30 rotates the motor 20 in the positive direction, the actual current value I cannot flow when the FET 35D is out of order. Therefore, the ECU 30 increases the duty ratio (duty ratio D) of the FETs 35A and 35D so that the actual current value I flows. In this case, the voltage V1 (the downstream terminal voltage in this case) is almost equal to the voltage V2 (the upstream terminal voltage in this case) and becomes the “power supply voltage Vp”. For this reason, since the second additional determination condition is satisfied, a failure of the drive circuit 35 can be detected more reliably.

  When the second additional determination condition is satisfied, it may be determined that a failure has occurred on the lower MOS-FET (FET 35C, 35D) side in the drive circuit 35. That is, the failure part of the drive circuit 35 can be further specified by adding the second additional determination condition.

Each embodiment may be changed as follows. Further, the following other embodiments can be combined with each other within a technically consistent range.
-In 1st Embodiment, although the open failure of FET35A-35D etc. were detected by step S3-step S7 of FIG. 5, it is not restricted to this. In the case of YES in step S2, since the estimated motor rotational speed ω is small, it is considered that the actual current value I is not likely to flow due to the counter electromotive voltage Fc, so that an open failure of the motor connector or a disconnection of the ground Gnd Other faults of the drive circuit 35 such as a fault may be detected.

  In the first embodiment, in step S3 and step S8 in FIG. 5, it is determined whether the duty ratio D is larger than the duty ratio threshold D0 and whether the actual current value I is less than the actual current value threshold I0. Not limited to this. For example, instead of the condition “the duty ratio D is greater than the duty ratio threshold D0”, the condition “the current command value (command threshold) is greater than the current command value threshold” may be used. The condition may be greater than the voltage command value threshold. That is, it suffices if it is possible to detect that no current actually flows though the motor 20 is trying to pass a current.

  In each embodiment, the failure of the drive circuit 35 is determined when the estimated motor rotation speed ω is less than the rotation speed threshold value ω 0, but the present invention is not limited to this. If the inter-terminal voltage Vm is used in place of the estimated motor rotational speed ω, the inter-terminal voltage threshold is used in place of the rotational speed threshold ω 0, and the inter-terminal voltage Vm is less than the inter-terminal voltage threshold, the drive circuit 35 fails May be confirmed. The terminal voltage threshold is, for example, the terminal voltage Vm corresponding to the rotation speed threshold ω0. For example, when applied to the second embodiment, the failure determination condition is that the duty ratio D is larger than the duty ratio threshold D0, the actual current value I is smaller than the actual current value threshold I0, and the terminal voltage Vm is the terminal voltage. Whether it is less than the threshold.

  In the third embodiment, in addition to the basic determination conditions (D> D0, I <I0, and ω <ω0), the first determination conditions (V1 <α × Vp and V2 <α × Vp) and the first Although the failure of the drive circuit 35 is detected based on the two additional determination conditions (V1> β × Vp and V2> β × Vp), the present invention is not limited to this. For example, the failure of the drive circuit 35 may be detected based on the basic determination condition and the first additional determination condition, or the failure of the drive circuit 35 may be detected based on the basic determination condition and the first additional determination condition. Also good. In other words, the failure of the drive circuit 35 may be detected by adding only one of the first and second additional determination conditions to the basic determination condition.

  -In each embodiment, although FET35A-35D (especially MOS-FET) was used as a switching element, it is not restricted to this. For example, an IGBT (insulated gate bipolar transistor) may be used.

In each embodiment, the ground Gnd is provided inside the ECU 30, but a ground may be provided outside the ECU 30.
In each embodiment, the PI calculation unit 34 stops the assist function in the EPS 1 when the failure determination unit 37 detects a failure in the drive circuit 35, but the assist function is performed in a state where the left-right difference of the motor torque is reduced. You may continue.

  In each embodiment, the control target of the ECU 30 (motor control device) is the motor 20 (brush motor), but the rotation angle for detecting the rotation speed of the rotation shaft of the motor 20 is not limited to the brush motor. It may be a motor in which no sensor is provided.

  -Although ECU30 of each embodiment was materialized in EPS1 which assists a driver | operator's steering operation, it is not restricted to this. That is, the ECU 30 may be applied to any device, for example, a steer-by-wire.

  DESCRIPTION OF SYMBOLS 1 ... EPS, 2 ... Steering mechanism, 3 ... EPS actuator, 10 ... Steering wheel, 11 ... Steering shaft, 12 ... Column shaft, 13 ... Intermediate shaft, 14 ... Pinion shaft, 15 ... Rack shaft, 16 ... Rack and pinion Mechanism: 17 ... Tie rod, 18 ... Steering wheel, 20 ... Motor, 21 ... Reduction gear, 22 ... Wheel gear, 23 ... Worm gear, 30 ... ECU (motor control device), 31 ... Current detection unit, 32 ... Current sensor, 33 ... Current command value calculation unit, 34 ... PI calculation unit (control unit), 35 ... Drive circuit, 35A to 35D ... FET (switching element), 36 ... Motor rotation speed estimation unit (rotation speed estimation unit), 37 ... Failure determination Part (determination part), 41 ... torque sensor, 42 ... vehicle speed sensor, θ ... rudder angle, τ ... steering torque, ω ... Estimated rotational speed, B ... battery, D ... duty ratio, I ... actual current value, R ... resistance, V ... vehicle speed, ω0 ... rotational speed threshold, D0 ... duty ratio threshold (command threshold), Fc ... counter electromotive voltage, I *: current command value, I0: actual current value threshold, M1, M2: terminal, Sp: PWM signal, τ: steering torque, Vm: voltage between motor terminals, CNT: failure detection count, Gnd: ground, Th: failure Detection count threshold, Th1... First failure detection count threshold (first threshold), Th2... Second failure detection count threshold (second threshold).

Claims (7)

A drive circuit for supplying power to the motor;
A current detector for detecting an actual current value supplied to the motor from the drive circuit;
A current command value calculation unit that calculates a current command value that is a target of the actual current value to be given to the motor according to various state quantities;
A feedback control unit for performing current feedback control for causing the actual current value to follow the current command value;
When the motor terminal voltage is less than the terminal voltage threshold, the actual current value is smaller than the actual current value threshold even though the current command value is set to a value larger than the command threshold. And a determination unit that determines a failure of the drive circuit based on whether or not the situation continues for a predetermined time. The motor control device according to claim 1,
A rotation speed estimation unit that calculates an estimated rotation speed that is a value obtained by estimating the rotation speed of the motor based on a voltage between terminals of the motor;
The determination unit uses the estimated rotation speed instead of the terminal voltage, uses the rotation speed threshold instead of the terminal voltage threshold,
When the estimated rotational speed is less than the rotational speed threshold, the actual current value is smaller than the actual current value threshold even though the current command value is set to a value larger than the command threshold. A motor control device that determines failure of the drive circuit based on whether or not is continued for a predetermined time. The motor control device according to claim 2,
The determination unit
If the estimated rotational speed is less than a rotational speed threshold, the predetermined time is set as a first threshold to determine a failure of the drive circuit;
A motor control device that determines a failure of the drive circuit by setting the predetermined time to a second threshold value that is greater than the first threshold value when the estimated rotational speed is greater than or equal to a rotational speed threshold value. In the motor control device according to claim 2 or 3,
The estimated rotational speed is a motor control device that is calculated in proportion to a difference obtained by subtracting a product of a resistance and a current value, which are constants set based on the actual current value, from a terminal voltage of the motor. In the motor control device according to any one of claims 2 to 4,
When the estimated rotational speed is less than the rotational speed threshold, the determination unit determines that the actual current value is greater than the actual current value threshold, even though the current command value is set to a value greater than the command threshold. The motor control apparatus which determines the open failure of any one of the switching elements provided in the said drive circuit when the condition which is a small value continues for the predetermined time. In the motor control device according to any one of claims 1 to 5,
The switching element of the drive circuit is turned on / off based on the duty ratio of the PWM signal output by the feedback control unit,
The duty ratio is greater than a duty ratio threshold when the current command value is set to a value greater than the command threshold;
When the actual current value is smaller than the actual current value threshold, the actual current value is a situation that is smaller than the actual current value threshold,
The determination unit
When the duty ratio is larger than the duty ratio threshold, and when the actual current value is smaller than the actual current value threshold, when the count added exceeds the count threshold, it continues for a predetermined time. A motor control device for determining. In the motor control device according to any one of claims 1 to 6,
The determination unit
Basic determination including that the voltage between terminals is less than a voltage threshold between terminals, the current command value is set to a value larger than the command threshold, and the actual current value is smaller than the actual current value threshold. In addition to the conditions
At least one of the upstream terminal voltage and the downstream terminal voltage of the motor being smaller than a first power supply voltage threshold, and the upstream terminal voltage and the downstream terminal voltage of the motor being larger than a second power supply voltage threshold. Judgment is performed using additional judgment conditions including
A motor control device that determines a failure of the drive circuit based on whether or not a situation that satisfies both the basic determination condition and the additional determination condition continues for a predetermined time.