JP5595551B1 - Motor control device and electric power steering device provided with motor control device - Google Patents

Abstract

The present invention improves the detectability of a relay abnormality determination during motor rotation when determining an abnormality of a relay that cuts off a motor output.
When performing abnormality determination of relays 21a and 21b with motor terminal voltage monitoring means 22 and 23, a plurality of switching elements 20a to 20d are turned on so as to be in power braking, and then abnormality of relay 21a is determined. When the switching element 20c is turned on, the motor terminal voltage monitoring means 22 when the switching element 20c is turned on is used. When the abnormality of the relay 21b is determined, the motor terminal voltage monitoring means when the switching element 20d is turned on. 23 is used.
[Selection] Figure 1

Description

  The present invention relates to a motor control device and an electric power steering device including the motor control device, and in particular, by driving a predetermined switching element of a bridge circuit composed of a plurality of switching elements constituting a driving device of an electric motor. The present invention relates to a motor control device that determines abnormality of a relay that cuts off power feeding between the bridge circuit and the electric motor, and an electric power steering device that includes the motor control device.

  The electric power steering device of an automobile assists the driver's steering by using the driving force of the electric motor controlled by the motor control device. The electric motor used in the electric power steering apparatus starts its operation after the motor relay is turned on when the automobile is started and control by the motor control apparatus becomes possible.

  FIG. 12 is a schematic configuration diagram of an electric power steering device for an automobile disclosed in, for example, Japanese Patent Application Laid-Open No. 2010-148274. As shown in FIG. 12, the electric power steering apparatus 10 includes a steering column 12 provided outside a steering shaft (not shown) connected to the handle 11 and torque for detecting the steering force of the driver's handle 11. A sensor 13, an electric motor 14 that applies auxiliary steering torque to the steering shaft, a reduction gear 15 that obtains an output of the electric motor 14 that is proportional to the gear reduction ratio, and a motor control device 16 that controls the electric motor 14 are provided. Yes. The motor control device 16 receives a vehicle signal 17 such as the speed of the automobile, a steering force of the handle 11 detected by the torque sensor 13, and the like. A battery 18 is connected to the motor control device 16.

  Next, the motor control device 16 will be described. FIG. 13 is an internal schematic configuration diagram of the motor control device 16. In FIG. 13, reference numeral 19 denotes a control unit, and this control unit 19 is configured by the electric motor 14 based on a torque sensor signal (output signal of the torque sensor 13) that changes according to the steering force of the driver and the vehicle signal 17. A simple assist current is calculated, and the drive device 20 of the electric motor 14 is controlled. The driving device 20 is configured by a bridge circuit composed of a plurality of switching elements, and allows the electric current calculated in advance to flow through the electric motor 14. When the control unit 19 or the drive device 20 is abnormal, the control unit 19 turns off the relays 21a and 21b to stop power supply to the electric motor 14.

  The conventional electric power steering apparatus 10 is configured as described above, and relays 21a and 21b are activated when the motor control apparatus 16 is started so that the output of the electric motor 14 can be cut off when the control unit 19 or the drive apparatus 20 is abnormal. After performing the abnormality determination, the steering force assist is started after determining the abnormality.

JP 2010-148274 A

  In the electric power steering device that assists the steering force of the driver with the electric motor as described above, the technology disclosed in Patent Document 1, that is, after the relay abnormality determination is performed at the time of starting the motor control device, In the case where the assist of the steering force is started after the determination, since the relay is repeatedly turned on and off when the relay is determined to be abnormal, there is a problem that the contact of the relay is consumed and the life is shortened.

  In order to improve the above problem, the voltage at both terminals of the electric motor, that is, the motor terminal voltage is used to turn on a predetermined switching element of the bridge circuit, so that the relay malfunctions without repeating the on / off of the relay. There is a method of making a determination. However, in this method, when the driver steers the steering wheel at the time of starting the automobile or the steering wheel rotates due to tire torsion or the like, the rotational speed of the steering wheel 11 is reduced via the reduction gear 15 as shown in FIG. Thus, there is a problem that the abnormality of the relays 21a and 21b cannot be determined while the electric motor 14 is rotating because of the induced voltage generated at a higher motor rotation speed because of the motor speed multiplied by the reduction ratio.

  The present invention has been made to solve the above-described problem, and is a motor control device that improves the detectability of relay abnormality determination during rotation of the electric motor when determining abnormality of a relay that cuts off the output of the electric motor. An object of the present invention is to provide an electric power steering device including a motor control device.

A motor control device according to the present invention includes a control unit that controls an electric motor, and a bridge circuit that includes a plurality of switching elements. The drive device that drives the electric motor, and between the bridge circuit and the electric motor. A relay that cuts off the power supply, and motor terminal voltage monitoring means for monitoring each terminal voltage of the electric motor,
The control unit includes an abnormality determination unit that determines an abnormality of the relay, and the abnormality determination unit determines only a switching element on the upstream side as viewed from the electric motor among the switching elements constituting the bridge circuit. By turning on for a time or by turning on only the downstream side switching element as viewed from the electric motor for a predetermined time, the electric motor is caused to perform dynamic braking, and then, of the switching elements in the off operation A predetermined switching element is driven, and the abnormality of the relay is determined based on the monitor voltage detected by the motor terminal voltage monitoring means.

  According to the motor control device of the present invention, it is possible to improve the detectability of the relay abnormality determination when the electric motor rotates when determining the abnormality of the relay that cuts off the output of the electric motor.

It is a figure which shows the motor control apparatus by Embodiment 1 of this invention. It is a flowchart explaining operation | movement of the motor control apparatus by Embodiment 1 of this invention. It is a figure which shows the equivalent circuit of the electric motor by Embodiment 1 of this invention. It is a figure which shows the relationship between the motor rotational speed of the electric motor by Embodiment 1 of this invention, and a motor induced voltage. It is a figure explaining the abnormality determination of the relay which comprises the motor control apparatus by Embodiment 1 of this invention. It is a flowchart explaining operation | movement of the motor control apparatus by Embodiment 2 of this invention. It is a figure explaining the abnormality determination of the relay which comprises the motor control apparatus by Embodiment 3 of this invention. It is a figure which shows the relationship between the motor rotational speed of the electric motor by Embodiment 3 of this invention, and a motor induced voltage. It is a flowchart explaining operation | movement of the motor control apparatus by Embodiment 3 of this invention. It is a flowchart explaining operation | movement of the motor control apparatus by Embodiment 4 of this invention. It is a flowchart explaining operation | movement of the motor control apparatus by Embodiment 6 of this invention. It is a schematic block diagram of the conventional electric power steering apparatus. It is an internal schematic block diagram of the motor control apparatus with which the conventional electric power steering apparatus was equipped.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a motor control device and an electric power steering device according to the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a motor control apparatus according to Embodiment 1 of the present invention. For convenience of explanation, FIG. 1 also shows an electric motor controlled by the motor control device and a battery connected to the motor control device. The electric power steering apparatus provided with the motor control apparatus according to the first embodiment has the same configuration as the electric power steering apparatus described in FIG. 12 except for the motor control apparatus. FIG. 1 corresponds to FIG. 13, and the same reference numerals are assigned to the same or corresponding parts as FIG.

In FIG. 1, the motor control device 16 includes a control unit 19, which controls an electric motor from a torque sensor signal (an output signal of the torque sensor 13) and a vehicle signal 17 that change according to the steering force of the driver. (Hereinafter, simply referred to as a motor.) An appropriate assist current by 14 is calculated, and the driving device 20 of the motor 14 is controlled. As will be described later , the driving device 20 is configured by a bridge circuit of first to fourth switching elements 20a , 20b, 20c, and 20d , and allows the motor 14 to pass a current calculated in advance. When the control unit 19 or the drive device 20 is abnormal, the control unit 19 turns off the relays 21a and 21b to stop the power supply to the motor 14.

As shown in FIG. 1, the first to fourth switching elements 20 a , 20 b, 20 c, and 20 d are arranged with the first switching element 20 a and the second switching element 20 b on the upstream side when viewed from the motor 14. The third switching element 20c and the fourth switching element 20d are arranged on the downstream side when viewed from the motor 14, the connection point between the first switching element 20a and the third switching element 20c, and the second switching element 20b. A so-called H-bridge circuit configuration is formed in which the motor 14 is connected to the connection point of the fourth switching element 20d.
The first to fourth switching elements 20a, 20b, 20c, and 20d are switching elements that generate a PWM (Pulse Width Modulation) signal calculated by the control unit 19, and are generally used MOSFETs (Metal The MOSFET includes a parasitic diode. Note that a battery 18 is connected to the driving device 20, and the driving device 20 drives the motor 14 that assists the steering force of the steering wheel.

The motor controller 16 includes motor plus terminal voltage monitoring means 22 for monitoring the terminal voltage on the plus terminal M + side of the motor 14 and motor minus terminal voltage monitoring means 23 for monitoring the terminal voltage on the minus terminal M− side of the motor 14. Is provided. The motor plus terminal voltage monitoring means 22 is constituted by resistors 22a to 22c connected in a Y shape, for example, as shown in FIG. A voltage (for example, 5 V) is applied by connecting the Vcc power supply 24 to one end of the resistor 22a. Further, the motor minus terminal voltage monitoring means 23 includes resistors 23a to 23c connected in a Y shape, for example, as shown in FIG. A voltage (for example, 5 V) is applied by connecting the Vcc power supply 24 to one end of the resistor 23a. In FIG. 1, the first to fourth switching elements 20a, 20b, 20c, and 20d are described as an H-bridge circuit configuration, and a brushed motor is described as an example. However, not only a brushed motor but also a brushless polyphase is described. Similarly, the motor includes relays 21a and 21b, a bridge circuit including the first to fourth switching elements 20a , 20b, 20c, and 20d, a motor plus terminal voltage monitoring unit 22, and a motor minus terminal voltage monitoring unit 23. Applicable.

The motor control device 16 according to the first embodiment is configured as described above. Next, the operation thereof will be described.
First, an off failure determination method that is an abnormality of the relays 21a and 21b will be described with reference to the flowchart of FIG. In step S101, the relays 21a and 21b are turned on. This ON instruction is output from the control unit 19. In step S102, the motor plus terminal voltage monitoring means 22 and the motor minus terminal voltage monitoring means 23 monitor the terminal voltages of the plus terminal M + and minus terminal M- of the motor 14.

  As shown in FIG. 3, since the motor 14 can be ignored when the coil component of the motor 14 is stationary, an equivalent circuit can be configured from the induced voltage 14a of the motor 14 and the armature resistor 14b. Here, the induced voltage 14a of the motor 14 becomes higher as the motor rotation speed is higher, as shown in FIG. The induced voltage 14a can be calculated from the voltage between the motor terminals, and since the induced voltage is proportional to the rotation speed, the rotation speed of the motor 14 can be obtained from the voltage between the terminals of the motor 14.

Returning to FIG. 2, in step S103, if the absolute value of the voltage between the motor terminals is smaller than the predetermined value Vth1 as shown in the following equation (1), it is determined that the motor 14 is stopped, and in step S105. Proceeding to the process, if greater than the predetermined value Vth1, it is determined that the motor 14 is rotating, and the process proceeds to step S104. The control unit 19 has an abnormality determination unit, and each determination is performed by the abnormality determination unit.
| (M + terminal voltage monitor value) − (M−terminal voltage monitor value) | <Vth1 (1)

In step S104, the first and second switching elements 20a and 20b on the battery 18 side of the drive device 20 , that is, the upstream side when viewed from the motor 14 , are turned on, and the GND side , that is, the downstream side when viewed from the motor 14 side. When the third and fourth switching elements 20c and 20d are turned off and the plus terminal M + and the minus terminal M− of the motor 14 are short-circuited, the motor 14 can be subjected to dynamic braking. The motor 14 is stopped using the braking torque according to the rotational speed of the motor 14 at this time.

In step S105, when the rotation speed of the motor 14 is determined to stop by the abnormality determining means of the control unit 19, as shown in FIG. 5, the first switching element 20a, a second switching element 20b, a When the switching element 20d of No. 4 is turned off and the third switching element 20c is turned on, the relay 21a is turned on when it is normal, so the terminal voltage monitor value of the positive terminal M + of the motor 14 is expressed by the following equation (2). As shown.
22b * 22c * Vcc / {22b * 22c + 22a * (22b + 22c)} (2)

On the other hand, since the relay 21a is off when the relay 21a has an off failure, the monitor voltage value at the plus terminal M + of the motor 14 is expressed by the equation (3). Here, the resistance values 22a to 22c are set so that Expression (2) <Expression (3).
22b · Vcc / (22a + 22b) (3)

After step S105 has been set to drive the third switching element 20c, in step S106, (2) formula <Vth2 <(3) positive terminal M + of the terminal of the threshold Vth2 and the motor 14 that satisfy the equation Compare with the voltage monitor value. Thereby, the failure determination of the relay 21b is performed.

  If (M + terminal voltage monitor value) <Vth2 in step S106, it is determined that the relay 21a is normal, and the process proceeds to step S107 to determine whether the negative terminal M− side relay 21b is faulty. On the other hand, if (M + terminal voltage monitor value) <Vth2 is not satisfied in step S106, it is determined that the relay 21a is off-failure, the process proceeds to step S120, and assist stop processing is performed.

In step S107, when the first switching element 20a, the second switching element 20b, and the third switching element 20c are turned off and the fourth switching element 20d is turned on, the motor terminal voltage when the relay 21b is normal The monitor value is expressed by the following equation (4) as in step S105, while the motor terminal voltage when the relay 21b is broken is expressed by the following equation (5).
23b.23c.Vcc / {23b.23c + 23a. (23b + 23c)} (4)
23b · Vcc / (23a + 23b) (5)

  Here, by setting the resistance values so that 23a = 22a, 23b = 22b, and 23c = 22c, the failure determination of the relay 21b can be made in step S108 as in step S106.

  If (M−terminal voltage monitor value) <Vth2 in step S108, it is determined that the relay 21b is normal, and the process proceeds to step S109 to perform assist start processing. On the other hand, if (M−terminal voltage monitor value) <Vth2 is not satisfied, it is determined that the relay 21b is out of order, and the process proceeds to step S120 to perform assist stop processing.

As described above, the motor control device according to the first embodiment uses the motor terminal voltage to determine the first to fourth switching elements 20a constituting the drive device 20 before determining the relays 21a and 21b to be off-failure. , 20b, 20c, 20d of the bridge circuit 18 side, that is, the first switching element 20a and the second switching element 20b on the upstream side when viewed from the motor 14 are turned on, and the GND side, that is, viewed from the motor 14 side. By turning off the third switching element 20c and the fourth switching element 20d on the downstream side, dynamic braking is performed and the motor 14 is stopped. As a result, it is possible to improve the detectability of the OFF failure determination of the relays 21a and 21b when the motor 14 is rotating at the time of startup.

Embodiment 2. FIG.
Next, a motor control apparatus according to Embodiment 2 of the present invention will be described. In the first embodiment, the first switching element 20a and the second switching element 20b on the battery 18 side of the bridge circuit of the driving device 20 are turned on, and the third switching element 20c and the fourth switching element 20d on the GND side are turned on. Was turned off, and the motor 14 was stopped by power generation braking. However, even if the first switching element 20a and the second switching element 20b on the battery 18 side of the bridge circuit are turned off and the third switching element 20c and the fourth switching element 20d on the GND side are turned on, the motor The same effect as in the first embodiment can be obtained without short-circuiting the 14 terminals.

Hereinafter, a description will be given using the flowchart shown in FIG. The flowchart of FIG. 6 the setting of the switching element at S104 of the flowchart of FIG. 2, and off the first switching element 20a, a second switching element 20b, as shown in S201, the third switching element 20c, the fourth The switching element 20d is replaced so as to be turned on. Since the motor control device of the second embodiment is configured in the same manner as FIG. 1 described in the first embodiment, the description thereof is omitted.

As described above, the motor control device according to the second embodiment uses the motor terminal voltage to determine the third failure on the GND side of the bridge circuit that constitutes the drive device 20 before determining the relays 21a and 21b to be off-failure . By turning on the switching element 20c and the fourth switching element 20d and turning off the first switching element 20a and the second switching element 20b on the battery 18 side, dynamic braking is performed and the motor 14 is stopped. As a result, it is possible to improve the detectability of the OFF failure determination of the relays 21a and 21b when the motor 14 is rotating at the time of startup.

Embodiment 3 FIG.
Next, a motor control apparatus according to Embodiment 3 of the present invention will be described. In the first embodiment, the first switching element 20a and the second switching element 20b are turned on, the third switching element 20c and the fourth switching element 20d are turned off, and dynamic braking is performed to stop the motor. However, the pair of third switching elements 20c on the GND side of the bridge circuit constituting the driving device 20 is turned on, and the other first switching element 20a, second switching element 20b, and fourth switching element 20d are turned on. When turned off, a circuit as shown in FIG. 7 is obtained. In this case, the power generation braking capability is as shown in FIG. 8 due to the parasitic diode of the fourth switching element 20d, and the braking capability of the motor 14 is reduced as compared with the case of FIG. The same effects as those of the first embodiment can be obtained.

  Hereinafter, a description will be given using the flowchart shown in FIG. Note that the motor control apparatus according to the third embodiment is configured in the same manner as in FIG. 1 described in the first embodiment, and a description thereof will be omitted. Further, steps S101 to S102 in FIG. 9 are the same as those in the first embodiment, and the description thereof is omitted.

In step S301, the motor terminal voltage monitored in step S102 is compared. If the terminal voltage monitor value of the positive terminal M + of the motor 14 is higher, the third switching element 20c of the bridge circuit is turned on in step S105. By doing so, the terminal with the higher induced voltage of the motor 14 is connected to the GND to perform power braking. The reason why the motor braking is performed by connecting the terminal having the higher motor terminal voltage to the GND is to improve the detection by the determination of the terminal voltage monitor value of the plus terminal M + of the motor 14 <Vth2 in the next step S106. The reason for this is as follows.

  Due to the motor induced voltage generated by the rotation of the motor 14, the monitor value of the motor plus terminal voltage monitoring means 22 is increased or decreased depending on the rotation direction of the motor 14 as compared with the monitor value when the motor is stopped. When the M + terminal becomes high, the motor terminal voltage affected by the motor induced voltage becomes low, and when the M + terminal becomes low, the M- terminal becomes high. become. When the motor 14 is not completely stopped, the threshold voltage Vth2 is normal because the influence of the induced voltage due to the rotation of the motor 14 has become the threshold value Vth2 or less despite the OFF failure of the relay 21a. It cannot be determined whether or not For this reason, it is possible to improve the detection by connecting and determining the higher terminal to GND.

  Next, if (M + terminal voltage monitor value) <Vth2 in step S106, it is determined that the relay 21a is normal, and the process proceeds to step S107. On the other hand, if (M + terminal voltage monitor value) <Vth2, it is determined that the relay 21a has an open failure, the process proceeds to step S120, and assist stop processing is performed.

In step S107, in order to determine the failure of the relay 21b, only the fourth switching element 20d is turned on and the other first switching element 20a, second switching element 20b, and third switching element 20c are turned off. Proceed to step S108.

  If (M-terminal voltage monitor value) <Vth2 in step S108, it is determined that the relay 21b is normal, and the process proceeds to step S109 to perform assist start processing. On the other hand, if (M−terminal voltage monitor value) <Vth2 is not satisfied, it is determined that the relay 21b is in an off-failure state, the process proceeds to step S120, and assist stop processing is performed.

If (M + terminal voltage monitor value)> (M− terminal voltage monitor value) is not satisfied in step S301, the induced voltage of the motor 14 is increased by turning on the fourth switching element 20d of the bridge circuit in step S302. One motor terminal is connected to GND to perform dynamic braking.

  In step S303, if (M-terminal voltage monitor value) <Vth2, it is determined that the relay 21b is normal, and the process proceeds to step S304. On the other hand, if (M−terminal voltage monitor value) <Vth2 is not satisfied, it is determined that the relay 21b is in an off-failure state, and the process proceeds to step S120 to perform assist stop processing.

Next, in step S304, the third switching element 20c is turned on to determine the failure of the relay 21a, and the other first switching element 20a, second switching element 20b, and fourth switching element 20d are turned on. Turn off and proceed to the next Step S305.

  In step S305, if (M + terminal voltage monitor value) <Vth2, it is determined that the relay 21a is normal, and the process proceeds to step S109 to perform assist start processing. On the other hand, if (M + terminal voltage monitor value) <Vth2 is not satisfied, it is determined that the relay 21a is in an off-failure state, the process proceeds to step S120, and assist-off processing is performed.

  As described above, in the motor control device according to the third embodiment, the switching element (20c, 20d) of the bridge circuit that constitutes the drive device 20 is connected so that the motor terminal having the higher motor terminal voltage is connected to the GND. ) Is turned on and the other switching elements (any of 20a, 20b and 20c, 20d) are turned off to perform dynamic braking and stop the motor 14. As a result, it is possible to improve the detectability of the OFF failure determination of the relays 21a and 21b when the motor 14 is rotating at the time of startup.

Embodiment 4 FIG.
Next explained is a motor control apparatus according to embodiment 4 of the invention. The motor control device according to the fourth embodiment is configured in the same manner as in FIG. 1 described in the first embodiment, and the description thereof is omitted. In the first embodiment, the first switching element 20a and the second switching element 20b are turned on, and the third switching element 20c and the fourth switching element 20d are turned off, so that the motor 14 is driven by performing dynamic braking. Stopped. However, after performing dynamic braking for a predetermined time, the voltage between the motor terminals is compared, and if it is determined that the motor 14 has not stopped, the desired switching element is driven again to perform dynamic braking, and the motor 14 The failure determination of the relays 21a and 21b may be performed after the voltage between the motor terminals that can be determined to be stopped.

  Hereinafter, a description will be given using the flowchart shown in FIG. The difference from the flowchart shown in FIG. 2 is that, after power generation braking is performed for a predetermined time in step S104, the process returns to step S103, and the stop of the motor 14 is determined again using the voltage between the motor terminals. The other parts are the same as those in the flowchart of FIG.

As described above, the motor control device according to the fourth embodiment uses the voltage between the motor terminals until the state in which the motor 14 can be determined to be stopped is the first of the bridge circuits constituting the drive device 20 . When the first switching element 20a and the second switching element 20b are turned on and the third switching element 20c and the fourth switching element 20d are turned off, dynamic braking is performed and the motor 14 is stopped. As a result, it is possible to improve the detectability of the OFF failure determination of the relays 21a and 21b when the motor 14 is rotating at the time of startup.

Embodiment 5 FIG.
Next explained is a motor control apparatus according to embodiment 5 of the invention. The motor control device according to the fifth embodiment is configured in the same manner as in FIG. 1 described in the first embodiment, and the description thereof is omitted. In the fourth embodiment, after determining the rotation state of the motor 14 in step S103, if it is determined that the motor 14 is rotating, power generation braking is performed in step S104, but power generation is performed again in step S104. When braking, power generation braking may be performed for a longer time than the previous time. The flowchart is the same as that in FIG.

As described above, the motor control device according to the fifth embodiment uses the voltage between the motor terminals until the state in which the motor 14 can be determined to be stopped is the first of the bridge circuits constituting the drive device 20 . The first switching element 20a and the second switching element 20b are turned on, the third switching element 20c and the fourth switching element 20d are turned off, and the power generation braking time when the voltage between the terminals of the motor is confirmed again is lengthened. As a result, the determination of the voltage between the motor terminals and the number of loops of dynamic braking can be reduced, and as a result, the failure determination of 21a and 21b can be performed in a shorter time.

Embodiment 6 FIG.
Next explained is a motor control apparatus according to the sixth embodiment of the invention. The motor control apparatus according to the sixth embodiment is configured in the same manner as in FIG. 1 described in the first embodiment, and the description thereof is omitted. In the first embodiment, the OFF failure of the relays 21a and 21b is determined using the motor terminal voltage after the dynamic braking of the motor 14, but the ON failure of the relays 21a and 21b may be determined.

  This will be described below with reference to the flowchart shown in FIG. The change from the flowchart shown in FIG. 2 is that the relays 21a and 21b are turned off in step S601 after the motor 14 is stopped in step S103 or step S104. Next, in order to determine the failure of the relay 21a in step S105, a desired switching element is driven, and in step S602, the ON failure of the relay 21a is determined from the motor terminal voltage.

  The motor terminal voltage when the relay 21a is on failure is expressed by equation (2), and the motor terminal voltage when normal is expressed by equation (3). Therefore, when (M + terminal voltage monitor value) ≧ Vth2, the relay 21a is It determines with it being normal, and progresses to step S107, and when not satisfy | filling determination formula, it determines with the on failure of the relay 21a, and progresses to step S120.

  On the other hand, in order to determine the failure of the relay 21b, if (M + terminal voltage monitor value) ≧ Vth2 in step S603, it is determined that the relay 21b is normal and the process proceeds to step S109, and the determination formula is not satisfied. Is determined as an ON failure of the relay 21b, and the process proceeds to step S120. Except for the above, the second embodiment is the same as the first embodiment, and a description thereof is omitted.

  As described above, according to the motor control device according to the sixth embodiment, not only in the case of the relay 21a, 21b off failure, but also in the case of the relay 21a, 21b on failure, as shown in the first embodiment, The detectability of the on failure of the relays 21a and 21b when the motor 14 is rotating at the time of startup can be improved.

  While the first to sixth embodiments of the present invention have been described above, the present invention can be modified or omitted as appropriate within the scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus, 11 Steering wheel, 12 Steering column, 13 Torque sensor, 14 Electric motor, 14a Induced voltage, 14b Armature resistance, 15 Reduction gear, 16 Motor control apparatus, 17 Vehicle signal, 18 Battery, 19 Control part, 20 driving device, 20a, 20b, 20c, 20d switching element, 21a, 21b relay, 22 motor plus terminal voltage monitoring means, 22a-22c, 23a-23c resistance, 23 motor minus terminal voltage monitoring means, 24 Vcc power supply.

Claims (5)

A control unit for controlling the electric motor;
A drive device configured with a bridge circuit composed of a plurality of switching elements and driving the electric motor;
A relay that cuts off power supply between the bridge circuit and the electric motor;
Motor terminal voltage monitoring means for monitoring each terminal voltage of the electric motor;
With
The control unit includes an abnormality determination unit that determines abnormality of the relay,
The abnormality determining means is configured to turn on only a switching element on the upstream side as viewed from the electric motor among the switching elements constituting the bridge circuit for a predetermined time, or on the downstream side as viewed from the electric motor. Only for a predetermined period of time, the electric motor is subjected to dynamic braking, and then the predetermined switching element among the switching elements in the off state is driven, and the monitor detected by the motor terminal voltage monitoring means A motor control device that determines an abnormality of the relay based on a voltage. When the monitor voltage difference is larger than a first predetermined value, the relay is judged to be abnormal after performing the dynamic braking, and when the monitor voltage difference is smaller than the first predetermined value, the power generation The motor control device according to claim 1 , wherein the abnormality of the relay is determined without performing braking. After performing the dynamic braking, the switching element is turned on so that the motor terminal with the higher monitor voltage is connected to the ground, based on the voltage detected by the motor terminal voltage monitoring means at that time, the motor control device according to claim 1 or 2, characterized in that to determine the abnormality of the relay. The difference between the monitor voltage is equal to or larger than a second predetermined value, the motor control device according to any one of claims 1 to 3, and extends further predetermined time and performing the dynamic braking. An electric power steering apparatus comprising: a steering shaft; an electric motor that applies an auxiliary steering torque to the steering shaft; and the motor control device according to any one of claims 1 to 4 .