JP2009090817A - Electrically operated power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrically operated power steering device which improves the reliability of the rotation angle detection of a motor without using a resolver for backup. <P>SOLUTION: The electrically operated power steering device is provided with a resolver failure detection part 44 for detecting the failure of the resolver 15, and an alternating wave forming means 47 and a superimposing part 34 which superimpose an alternating wave voltage on a d-axis control voltage Vd for controlling a d-axis current. The electrically operated power steering device has a backup circuit 50 for detecting the rotation angle of a motor 8 from each phase current of the motor 8 when the alternating wave voltage is superposed on the d-axis control voltage Vd by the alternating wave forming means 47 and the superimposing part 34. When the failure of the resolver 15 is detected, the superimposition of the alternating wave voltage to the d-axis control voltage Vd is maintained. When the failure of the resolver 15 is not detected, the superimposition of the alternating wave voltage to the d-axis control voltage Vd is carried out with a predetermined timing only for a predetermined time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus.

Conventionally, in an electric power steering device using a driving force of a motor, a device that detects a rotation angle of a brushless motor with a resolver and performs motor control based on the detection result is known (for example, Patent Documents). 1).
JP 2005-274484 A

However, since the above-described electric power steering apparatus includes a plurality of backup resolvers so that the rotation angle of the motor can be detected continuously when the resolver fails, the apparatus becomes large and the degree of installation is reduced. There is a problem.
Also, since the backup resolver does not detect the detection signal unless the main resolver fails, if the main resolver actually fails, the backup resolver will not operate due to the same failure. There is a fear.

  Accordingly, the present invention provides an electric power steering device that can improve the reliability of detection of the rotation angle of a motor without using a resolver for backup.

  In order to solve the above problem, the invention described in claim 1 is a current sensor (for example, a phase current detection unit 39 in the embodiment) that detects a phase current of a brushless motor (for example, the motor 8 in the embodiment). ) And rotation angle detection means for detecting the rotation angle of the brushless motor (for example, the resolver 15 in the embodiment), the q-axis current and the d-axis current obtained using at least the two-axis three-phase conversion In the electric power steering apparatus that controls each phase current of the brushless motor, a failure detection unit (for example, a resolver failure detection unit 44 in the embodiment) that detects a failure of the rotation angle detection unit, and the d-axis current Superimposing means that can superimpose an AC wave voltage or a rectangular wave voltage on a control signal for controlling the voltage (for example, AC wave forming means in the embodiment) 7 or the rectangular wave forming means 60 and the superimposing unit 34), and each of the brushless motors when the AC wave voltage or the rectangular wave voltage is superimposed on the d-axis current control signal by the superimposing means. A backup unit (for example, the backup circuit 50 in the embodiment) for detecting the rotation angle of the brushless motor based on the phase current is provided, and the backup unit detects a failure of the rotation angle detection unit by the failure detection unit. In the case where the AC wave voltage or the rectangular wave voltage is superposed on the control signal of the d-axis current, and when the failure detection means detects no failure of the resolver, the control of the d-axis current is performed. Superimposing an AC wave voltage or a rectangular wave voltage on a signal is performed for a predetermined time at a predetermined timing.

  According to a second aspect of the present invention, in the first aspect of the invention, when the failure detection means does not detect a failure of the rotation angle detection means, the d-axis is used when the brushless motor is in a high rotation state. An AC wave voltage or a rectangular wave voltage is superimposed on a current control signal for a predetermined time.

According to the first aspect of the present invention, the alternating current voltage or the rectangular wave voltage is superimposed on the control signal of the d-axis current by the superimposing means, so that the brushless operation is performed based on the phase current detected by the current sensor by the backup means. Since the rotation angle of the motor can be detected, the rotation angle detecting means such as a resolver is not provided for backup as compared with the conventional case, so that the size of the apparatus can be suppressed and the installation flexibility can be improved. effective.
In addition, when a failure of the rotation angle detection means is detected by the failure detection means, the rotation angle of the brushless motor is detected by the backup means by superimposing an AC wave voltage or a rectangular wave voltage on the d-axis current control signal by the superimposing means. Furthermore, even if a failure of the rotation angle detecting means is not detected, whether the backup means is out of order by superimposing an AC wave voltage or a rectangular wave voltage for a predetermined time at a predetermined timing. Therefore, it is possible to reliably detect the rotation angle of the brushless motor by the backup means when the rotation angle detection means fails, and thus improve the reliability of the detection of the rotation angle of the brushless motor. There is an effect that can be done.

  According to the second aspect of the present invention, for example, when the AC wave voltage or the rectangular wave voltage is superimposed on the d-axis current control signal when the brushless motor is in the low rotation state, the AC wave voltage or the rectangular wave voltage is superimposed. The d-axis current for the amount of superposition flows to the brushless motor and may cause vibrations felt by the driver on the steering wheel. However, when the brushless motor is in a high rotation state, the phase current becomes large and the superposition is relatively small. Therefore, the driver's uncomfortable feeling due to vibration or the like can be suppressed.

Next, an embodiment of the electric power steering apparatus of the present invention will be described with reference to the drawings.
As shown in FIG. 1, in the vehicle steering control apparatus according to this embodiment, a steering shaft 2 provided integrally with a steering wheel 1 is connected to a steering gear via a connecting shaft 3 having universal joints 3a and 3b. A manual steering force generating mechanism 5 is configured by being connected to a pinion 4a of a rack and pinion mechanism 4 provided in a box (not shown).

The pinion 4a meshes with the rack teeth 6a of the rack shaft 6, and the rotational motion input from the steering wheel 1 is converted into the reciprocating motion of the rack shaft 6 via the pinion 4a. , 7 to steer the two steered wheels W, W connected together.
A so-called brushless type motor 8 is disposed coaxially with the rack shaft 6, and the rotational force of the motor 8 is converted into thrust through a ball screw mechanism 9 provided substantially parallel to the rack shaft 6. In other words, a rotor (not shown) of the motor 8 is integrally provided with a drive-side helical gear 8a, and this drive-side helical gear 8a is integrally provided at the shaft end of the screw shaft 9a of the ball screw mechanism 9. 9b. The motor 8 is provided with a resolver 15 that is adjacent to the motor 8 and detects the rotation angle of the rotor.

  In the steering gear box, there is provided a torque sensor 10a for detecting the steering torque TRQ acting on the pinion 4a, that is, the steering torque TRQ input by the driver's manual operation, and is detected by this torque sensor 10a. The detected steering torque TRQ signal is input to the EPS control device 10.

  As shown in FIG. 2, the EPS control device 10 calculates a target current based on the detection results of the torque sensor 10a, the vehicle speed sensor 10b, etc., and performs feedback control of the current on the dq coordinates forming the rotation orthogonal coordinates. It is.

  The EPS control device 10 includes a low-pass filter (LPS) 20 that filters the torque VTI detected by the torque sensor 10a based on the vehicle speed VEL detected by the vehicle speed sensor 10b. The EPS control device 10 also includes a phase compensation unit 21 that performs phase compensation of the torque VTE based on the torque VTE and the vehicle speed VEL, and the phase compensated torque ABSTRQ is output from the phase compensation unit.

  The EPS control device 10 includes an assist base table 22 that is a table of the basic current value ITN_D of the target current for assisting the steering torque by the above-described phase compensated torque ABSTRQ, the vehicle speed VEL, and the motor 8. Based on the post-phase compensation torque ABSTRQ and the vehicle speed VEL, the assist base table 22 determines the basic current value ITN_D.

  Further, the EPS control device 10 improves the responsiveness based on the basic current value ITN_D obtained from the assist base table 22 based on the vehicle speed VEL and the motor torque upper limit value RTOCUR calculated by the motor output limiter 23 (described later). The first correction table 24 for obtaining the correction value is provided. By referring to the first correction table 24, a correction value for improving responsiveness is added to the basic current value ITN_D to obtain a first correction value ITNL_J. Further, the EPS control device 10 sets the second correction value ITNL_H based on the first correction value ITNL_J, the vehicle speed VEL, and the motor speed MVEL calculated by the motor speed calculation unit 26 (described later) in order to perform damper control. A second correction table for output is provided.

  Furthermore, the EPS control apparatus 10 includes a target current calculation unit 27 that calculates the target current ITN based on the second correction value ITNL_H and the average limit value AVELIM of the motor output output from the motor output limit unit 23. The target current ITN output from the target current calculation unit 27 is input to the ITN correction unit 28. The ITN correction unit 28 calculates a correction value of the target current ITN based on the rotation angle of the motor 8, adds the correction value to the target current ITN, and calculates a target current correction value ITN_R. The target current correction value ITN_R is output to the q-axis PI control unit 29 that performs control.

  The q-axis PI control unit 29 and the d-axis PI control unit 30 calculate control voltages for designating the U-phase current IU, V-phase current IV, and W-phase current IW supplied to the motor 8, respectively. The q-axis PI control unit 29 is a q-axis control voltage Vq that is a q-axis control signal based on the target current correction value ITN_R and the q-axis current Iq that is a feedback current value output from the three-phase biaxial conversion unit 32. The q-axis control voltage Vq is input to the 2-axis 3-phase conversion unit 33.

  The d-axis PI control unit 30 includes a correction current ID_T output from the field current control unit 31 that controls the field current based on the motor speed MVEL, and a feedback current value output from the three-phase biaxial conversion unit 32. The d-axis control voltage Vd, which is a d-axis control signal, is calculated based on the d-axis current Id and the motor speed MVEL output from the motor speed calculation unit 26. The d-axis control voltage Vd is input to the two-axis three-phase conversion unit 33 via the superimposing unit 34.

  The dq coordinates that form the rotation orthogonal coordinates are, for example, the magnetic field direction of the field pole by the permanent magnet of the rotor is the d axis (field magnetic pole), and the direction orthogonal to the d axis is the q axis (torque axis). The rotor rotates in synchronization with the rotational phase of the rotor.

  The biaxial three-phase conversion unit 33 uses the rotation angle ANGLE output from the angle calculation unit 36 that calculates the rotation angle of the motor 8 or the rotation angle output from the position detection unit 41 to control the d axis on the dq coordinate. The voltage Vd and the q-axis control voltage Vq are converted into a U-phase output voltage VU, a V-phase output voltage VV, and a W-phase output voltage VW that are voltage commands on a three-phase AC coordinate that is a stationary coordinate. The U-phase output voltage VU, the V-phase output voltage VV, and the W-phase output voltage VW converted by the two-axis three-phase conversion unit 33 are input to the midpoint modulation DUTY control unit 37.

The midpoint modulation DUTY control unit 37 determines the duty of the drive circuit 38 formed of a so-called three-phase inverter based on the U-phase output voltage VU, the V-phase output voltage VV, and the W-phase output voltage VW described above. The voltage DUTY_U, the V-phase duty voltage DUTY_V, and the W-phase duty voltage DUTY_W are converted and output.
The drive circuit 38 controls ON / OFF of the switching element based on the U-phase duty voltage DUTY_U, the V-phase duty voltage DUTY_V, and the W-phase duty voltage DUTY_W output from the midpoint modulation DUTY control unit 37 to the motor 8. The U-phase current IU, the V-phase current IV, and the W-phase current IW are applied.

  An angle calculator 36 is connected to the resolver 15 via an I / F circuit 35. The angle calculator 36 calculates and outputs the rotation angle ANGLE of the motor 8 based on the output signal of the resolver 15.

  A U-phase current IU and a W-phase current IW that are actually energized are detected between the drive circuit 38 and the motor 8, and all three phases are detected based on the U-phase current IU and the W-phase current IW. A phase current detection unit 39 that calculates and outputs a current value is provided. The current values of all three phases calculated by the phase current detection unit 39 are input to a UVW / α-β conversion unit 40 described later.

  Further, the U-phase current value and the W-phase current value output from the phase current detection unit 39 are input to the three-phase biaxial conversion unit 32. The three-phase two-axis conversion unit 32 uses the current value of the U phase and the current value of the W phase and the rotation angle ANGLE of the angle calculation unit 36 to determine the d axis on the rotation coordinate, i. The current Id and the q-axis current Iq are calculated. The d-axis current Id calculated by the three-phase two-axis converter 32 is input to the d-axis PI controller 30, while the q-axis current Iq is input to the q-axis PI controller 29 and the motor output limiter 23. The

  The motor speed calculation unit 26 calculates the motor rotation number MVEL based on the motor rotation angle such as the rotation angle ANGLE by the angle calculation unit 36 described above. The motor rotational speed MVEL output from the motor speed calculation unit 26 is obtained from the d-axis PI control unit 30, the field current control unit 31, the second correction table 25, and the vector pulse switch (Vector Pulse Switch) unit of the backup circuit 50. 42 and a position sensor selection unit 43.

  The backup circuit 50 is a circuit for detecting the rotation angle of the motor 8 without using the resolver 15 when the resolver 15 breaks down. The backup circuit 50 includes the UVW / α-β conversion unit 40, position detection, and the like. Unit (Position Detection) 39, vector pulse switch unit 42, position sensor selection unit 43, resolver failure detection unit 44, selection switch 45, switch 46 and AC wave forming means 47.

  The AC wave forming means 47 is a so-called oscillator that generates an AC minute voltage VS having a predetermined peak frequency and a relatively high frequency as an AC wave voltage, and the AC minute voltage VS generated by the AC wave forming means 47 is The superimposing unit 34 can be supplied via the switch 46. The switch 46 is interposed between the AC wave forming unit 47 and the superimposing unit 34, and shorts and opens between the AC wave forming unit 47 and the superimposing unit 34 based on the control command of the vector pulse switch unit 42. Is what you do. That is, the AC minute voltage VS is superimposed on the d-axis control voltage Vd only when the switch 46 is controlled to be short-circuited.

The UVW / α-β converter 40 converts the current values of all UVW phases output from the phase current detector 39 into α-β coordinates. The α-axis current Iα and the β-axis current Iβ converted by the UVW / α-β conversion unit 40 are input to the position detection unit 41.
The position detection unit 41 converts the phase current that is energized and controlled by the UVW / α-β conversion unit 40 based on the d-axis control voltage Vd on which the AC minute voltage VS is superimposed by the AC wave forming unit 47. The position of the rotor, that is, the rotation angle of the motor 8 is detected based on the shaft current Iα and the β-axis current Iβ. The rotation angle detected by the position detection unit 41 is converted into angle information in place of the rotation angle ANGLE calculated by the angle calculation unit 36 described above, via the selection switch 45, and the motor speed calculation unit 26, the 2-axis three-phase conversion unit 33, and Input to the midpoint modulation duty control unit 37 is possible.

  The selection switch 45 receives an input signal to the motor speed calculation unit 26, the two-axis three-phase conversion unit 33, and the midpoint modulation duty control unit 37, either the output of the angle calculation unit 36 or the output of the position detection unit 41. The position sensor selection unit 43 controls the switching of the output signal.

  The vector pulse switch unit 42 performs ON / OFF control of the switch 46 based on the motor rotation number MVEL output from the motor speed calculation unit 26 and the output of the resolver failure detection unit 44, and the motor rotation number MVEL is When the predetermined number of revolutions or more has elapsed and when it is determined that the resolver 15 has failed, the switch 46 is turned on. On the other hand, it is determined that the resolver 15 has not failed, and the motor speed MVEL Is controlled to be OFF when the rotation speed is less than the predetermined number of revolutions or when a predetermined time has elapsed after the ON control.

  As with the vector pulse switch unit 42 described above, the position sensor selection unit 43 is based on the motor speed MVEL output from the motor speed calculation unit 26 and the output of the resolver failure detection unit 44, and the motor speed calculation units 26, 2. This is for selecting which of the angle calculation unit 36 and the position detection unit 41 is connected to the shaft three-phase conversion unit 33 and the midpoint modulation duty control unit 37. The position sensor selection unit 43 selects and controls the position detection unit 41 when the motor rotation number MVEL is equal to or higher than the predetermined rotation number and a predetermined time has elapsed, and when it is determined that the resolver 15 is out of order. Is determined to have not failed, and the angle calculation unit 36 is selectively controlled when the motor rotation number MVEL is less than the predetermined rotation number or when a predetermined time has elapsed after selection control of the position detection unit 41.

  The resolver failure detection unit 44 detects a failure state of the resolver 15 and is connected to, for example, the I / F circuit 35 or the angle calculation unit 36, and the detection signal of the resolver 15 is below a predetermined level set in advance. When it is determined that the state is lowered or abnormal, a failure detection signal is output toward the position sensor selection unit 43 and the vector pulse switch unit 42.

  Here, when the switch 46 is ON, the position detection unit 41 can calculate the rotation angle ANGLE. Therefore, if the resolver 15 is not malfunctioning, the detection angle of the resolver 15 and the detection angle of the position detection unit 41 Can be detected as a failure of the position detector 41. FIG. 2 shows an example of detecting a failure of the position detection unit 41 using a position detection unit failure detection circuit 60 including a differential amplification unit 61, a comparison unit 62, and a failure detection unit 63. The differential amplification unit 61 of the position detection unit failure detection circuit 60 calculates a difference between the detection angle of the resolver 15 and the detection angle of the position detection unit 41. The comparison unit 62 compares the output of the differential amplification unit 61 with a preset failure detection threshold value, and performs a predetermined output when the output of the differential amplification unit 61 is greater than the threshold value. The failure detection unit 63 is configured to be able to receive the failure detection signal from the resolver failure detection unit 44 and the predetermined output of the comparison unit 62, and when the failure detection signal is not received, the predetermined output of the comparison unit 62 is output. Only when it is made, a failure signal indicating that the position detection unit 41 has failed, that is, a failure signal of the backup circuit (B / U) 50 is output.

  When the switch 46 is ON, the position detection unit 41 is simultaneously selected by the selection switch 45. As a result, the rotation angle detection system by the resolver 15 is disconnected from the main circuit of the EPS control device, and the backup circuit. 50 is connected to the main circuit of the EPS control device 10, and the EPS control device 10 starts motor control based on the rotation angle of the motor 8 detected by the backup circuit 50. The main circuit means a circuit configuration of the EPS control device 10 other than the circuit system that detects the rotation angle of the motor 8.

Next, switching control processing by the vector pulse switch unit 42 and the position sensor selection unit 43 described above will be described with reference to the flowchart of FIG.
First, in step S1, based on the output of the resolver failure detection unit 44, it is determined whether any of the resolver 15, the I / F circuit 35 that is an angle detection system of the resolver 15, and the angle calculation unit 36 is in a failure state. . If the determination result of step S1 is “Yes” (failure), the process proceeds to step S6, and if “No” (not failure), the process proceeds to step S2.

  In step S2, it is determined whether or not the motor 8 is rotating at a high speed. When the determination result of step S2 is “Yes” (high rotation), the process proceeds to step S3, and when it is “No” (not high rotation), this process ends (end). When determining whether or not the rotation speed is high in step S2, a predetermined motor rotation speed threshold value is set in advance, and the motor rotation speed MVEL calculated by the motor speed calculation unit 26 exceeds the motor rotation speed threshold value. It is determined that the speed is high. Here, the predetermined motor rotational speed is an arbitrary motor rotational speed to such an extent that vibrations appearing on the steering wheel are extinguished by the AC minute voltage VS superimposed by the AC wave forming means 47 and become inconspicuous.

In step S3, the switch 46 is turned on and the position detection unit 41 is selected by the selection switch 45 to connect the AC wave forming means 47 to the main circuit of the EPS control device 10 for a predetermined time, and the process proceeds to step S4.
In step S4, it is determined whether or not the backup (B / U) circuit 50 is normal. If the determination result in step S4 is “Yes” (normal), the process ends. If the determination result is “No” (not normal), the process proceeds to step S5. Here, as an example of determining whether or not the backup circuit 50 is normal, for example, when the backup circuit 50 is connected to the main circuit of the EPS control device 10 for a predetermined time in step S3, the motor speed calculation unit 26 sets the motor. It can be determined as normal when the rotational speed MVEL is output and abnormal when it is not output.

In step S5, an alarm to the effect that the backup (B / U) circuit 50 has failed is displayed, for example, on a meter panel in front of the driver's seat of the vehicle or by sound output from a speaker.
On the other hand, in step S6, since it is determined that the resolver 15 is out of order, the switch 46 is ON-controlled and the position detection unit 41 is selected by the selection switch 45 and the backup (B / U) circuit 50 is EPS-controlled. The process is terminated after the connection to the main circuit of the apparatus 10 is always made. Note that the backup circuit 50 may be disconnected from the main circuit of the EPS control device 10 when it is determined that the resolver 15 has resolved the failure state.

  Therefore, according to the above-described embodiment, the alternating current minute voltage is superimposed on the d-axis control voltage Vd by the alternating current wave forming means 47 and the superimposing unit 34, so that the phase current detection unit 39 detects by the backup circuit 50. Since the rotation angle of the motor 8 can be detected based on the phase current, the EPS control device 10 can be prevented from being enlarged and the degree of freedom in installation can be reduced by the amount that the backup resolver 15 is not provided. Can be improved.

  Further, when the resolver failure detection unit 44 detects a failure of the resolver 15, the backup circuit 50 causes the motor 8 of the motor 8 to be superposed on the d-axis control voltage Vd by the AC wave forming unit 47 and the superimposing unit 34. The rotation angle can be detected, and even if the failure of the resolver 15 is not detected, the alternating current minute voltage is superimposed for a predetermined time at a predetermined timing, and whether or not the backup circuit 50 has failed. Therefore, it is possible to reliably detect the rotation angle of the motor 8 by the backup circuit 50 when the resolver 15 fails. As a result, the reliability of the rotation angle detection of the motor 8 can be improved. .

  Further, for example, when an AC minute voltage is superimposed on the d-axis control voltage Vd when the motor 8 is in a low rotation state, a phase current due to the d-axis current corresponding to the superimposed AC minute voltage flows to the motor 8, and the steering wheel. However, when the motor 8 rotates at a high speed, an alternating minute voltage is superimposed, so that the amount of the superimposed current is relatively small with respect to the phase current of the motor 8. As a result, the driver's uncomfortable feeling due to the vibration of the steering wheel can be suppressed.

As another aspect of the above-described embodiment, the AC minute voltage generated by the AC wave forming unit 47 may be replaced with a rectangular wave forming unit 60 that generates a rectangular wave voltage as shown in FIG. .
Specifically, the rectangular wave forming means 60 is an oscillator that generates a voltage of a predetermined frequency having a minute peak value and a relatively high frequency, like the AC wave forming means 47 of the above-described embodiment. As a difference from the forming means 47, a rectangular wave is used instead of an AC wave. In this case, the rotation angle of the motor 8 is detected based on the U / V / W phase currents IU, IV, and IW that are detected values of the phase current output based on the V-axis control voltage Vd on which the rectangular wave is superimposed. Therefore, a current difference vector detection unit 55 is provided instead of the UVW / α-β conversion unit 40 described above.

  The current difference vector detection unit 55 detects a current difference vector, converts the result into α-β coordinates, and outputs an α-axis difference Δisα and a β-axis difference Δisβ. The position detection unit 56 is configured to detect and output the rotation angle of the motor 8 based on the α-axis difference Δisα and the β-axis difference Δisβ detected by the current difference vector detection unit 55. Therefore, by superimposing the rectangular wave on the d-axis control voltage Vd by the rectangular wave forming means 60, the rotation angle of the motor 8 can be detected as in the case of using the AC wave forming means 47 described above.

  In the above embodiment, the case where the resolver 15 is used as a sensor for detecting the rotation angle of the motor 8 has been described. However, the present invention is not limited to the resolver 15 as long as the rotation angle can be detected.

1 is a schematic configuration diagram of an electric power steering device according to an embodiment of the present invention. It is a block diagram of the EPS control apparatus in the embodiment of the present invention. It is a flowchart of the determination process of the backup circuit selection in the embodiment of the present invention. It is a block diagram of the EPS control apparatus in the other aspect of embodiment of this invention.

Explanation of symbols

8 Motor (Brushless motor)
39 Phase current detector (current sensor)
15 Resolver (Rotation angle detection means)
44 Resolver failure detection unit (failure detection means)
47 AC wave forming means (superimposing means)
34 Superimposing part (superimposing means)
50 Backup circuit (backup means)
60 Rectangular wave forming means (superimposing means)

Claims (2)

Two-axis three-phase conversion is performed on the q-axis current and the d-axis current obtained using at least the detection results of the current sensor for detecting the phase current of the brushless motor and the rotation angle detection means for detecting the rotation angle of the brushless motor. In the electric power steering device that controls each phase current of the brushless motor,
A failure detecting means for detecting a failure of the rotation angle detecting means; and a superimposing means capable of superimposing an AC wave voltage or a rectangular wave voltage on a control signal for controlling the d-axis current. Provide backup means for detecting the rotation angle of the brushless motor based on each phase current of the brushless motor when an AC wave voltage or a rectangular wave voltage is superimposed on the control signal of the shaft current;
The backup means maintains a superposition of an AC wave voltage or a rectangular wave voltage on the control signal of the d-axis current when a failure of the rotation angle detection means is detected by the failure detection means, and the failure detection means When the rotation angle detecting means has not detected a failure by the electric power, the AC power or the rectangular wave voltage is superimposed on the d-axis current control signal for a predetermined time at a predetermined timing. Steering device.   When a failure of the rotation angle detection unit is not detected by the failure detection unit, an AC wave voltage or a rectangular wave voltage is applied to the control signal for the d-axis current for a predetermined time when the brushless motor is in a high rotation state. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is superposed.

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