JP2013233932A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of, when an abnormality occurs in one phase of a three-phase electric motor, continuing motor drive by using remaining two phases without deteriorating a steering feeling.SOLUTION: When an abnormality in energization is detected in a drive system of one phase out of respective phase coils by an abnormality detection means, an in-abnormality phase current command value for use of coils of remaining two phases is calculated by an in-abnormality motor command value calculation means 34 on the basis of a steering assist current command value Iref, and a three-phase electric motor 12 is driven on the basis of the in-abnormality phase current command value. In this case, there is provided a current command value correction means that lowers the in-abnormality phase current command value when the sum of steering torque and steering assist torque generated in the three-phase electric motor 12 balances with an external force.

Description

  The present invention relates to an electric power steering apparatus that drives and controls a three-phase brushless motor to apply a steering assist force that reduces a driver's steering burden to a steering system.

As a conventional electric power steering device, for example, there is a technique described in Patent Document 1. In this technology, when an abnormality occurs in one phase in a three-phase brushless motor, an abnormal current command value that makes the motor torque substantially constant is calculated based on the remaining two-phase back electromotive voltage information, The motor is continuously driven based on the current command value.
That is, since the motor rotation is intentionally accelerated in the steering direction in the acceleration region across the electrical angle where the sign of the abnormal time phase current command value calculated by the abnormal motor command value calculation means is reversed, By preventing the generation of the brake torque, the unstable output angle region where the motor torque is reduced can be effectively jumped by the motor inertia force, and the steering feeling can be improved.

JP 2011-51481 A

By the way, in the conventional example described in the above-mentioned Patent Document 1, the motor torque is generated by the two-phase coil excluding the electric angle range in which the motor torque cannot be generated at all or the motor torque is reduced, that is, the failure phase during the increase steering. Therefore, in the vicinity of the electrical angle corresponding to the failure phase, it becomes a torque reduction region where the motor torque decreases, and in the acceleration region including this torque reduction region, the motor rotation is accelerated in the steering direction and jumps over the torque reduction region. I am doing so. However, in the torque reduction region, when the torque obtained by adding the steering torque and the steering assist torque generated by the brushless motor is substantially equal to the external force (steering reaction force) and the steering torque is balanced, the torque reduction region is expressed by the inertia torque. There is an unresolved problem that a case where the driver cannot jump over occurs and gives the driver a feeling of being caught.
Therefore, the present invention provides a motor drive without causing a deterioration in steering feeling by reliably jumping over the torque reduction region when an abnormality occurs in one phase in a three-phase brushless motor and the motor is driven in the remaining two phases. It is an object of the present invention to provide an electric power steering device that can continue the operation.

In order to solve the above problems, a first aspect of an electric power steering apparatus according to the present invention includes a three-phase electric motor in which each phase coil for applying a steering assist force to a steering system is star-connected, and the steering system. The steering torque detecting means for detecting the steering torque transmitted to the coil, the coil energization abnormality detecting means for detecting the energization abnormality of each phase coil, and the coil energization abnormality detecting means detect the energization abnormality of the one-phase coil. Sometimes, an abnormal motor command value calculation means for calculating an abnormal time phase current command value for the remaining two-phase coils, and a motor control means for controlling the driving of the three-phase electric motor based on the abnormal time phase current command value An electric power steering device comprising:
A current command value correction means for reducing the abnormal time phase current command value when balancing the sum of the steering torque and the steering assist torque generated by the three-phase electric motor with an external force;
The current command value correcting means is a predetermined angle region in which the electrical angle of the three-phase electric motor straddles a minimum torque electrical angle at which the sign of the abnormal time phase current command value calculated by the abnormal motor command value calculating means is reversed. An acceleration region determination means for determining whether or not the acceleration angle is within the acceleration region, and when the electrical angle is determined to be within the acceleration region by the acceleration region determination means, Motor rotation acceleration means for accelerating the rotation of the three-phase electric motor in the steering direction by increasing and correcting the calculated abnormal time phase current command value, and the rotation of the three-phase electric motor by the motor rotation acceleration means in the steering direction Retry area determination means for determining whether or not the electrical angle continues across the minimum torque electrical angle and within a retry area wider than the acceleration area when the acceleration is accelerated to Retry acceleration that increases the acceleration region and re-accelerates the rotation of the three-phase electric motor in the steering direction when the region determination means determines that the state in which the electrical angle is within the retry region is continued. Means.

  Further, the second aspect of the electric power steering apparatus according to the present invention is such that the retry acceleration means has the electric angle in an acceleration region, and the abnormality is detected when the sum of the steering torque and the steering assist torque is balanced with an external force. The time phase current command value is decreased from the basic current command value, and when the electrical angle reaches the boundary position of the acceleration region, the abnormal time phase current command value is increased from the basic current command value and the three-phase electric motor The rotation of the motor is reaccelerated in the steering direction.

  A third aspect of the electric power steering apparatus according to the present invention includes motor rotation speed detection means for detecting a motor rotation speed of the three-phase electric motor, and the retry acceleration means includes the steering torque and the motor rotation. A determination of whether the steering direction is the increasing direction or the returning direction based on the speed and setting a first return flag, and a determination result of the acceleration region determining means; Based on the abnormal time phase current command value, the switchback flag, and the motor rotation speed, it is determined whether or not it is a torque reduction region, and a second switchback flag that instructs the switchback when it is in the torque reduction region A torque reduction region determination unit for setting the acceleration, a correction to decrease the abnormal time phase current command value based on the determination result of the acceleration region determination means and the second return flag, and to change the electrical angle by an external force Current And a correction current command gain generator for generating a decree gain.

According to a fourth aspect of the electric power steering apparatus of the present invention, the electrical angle after the retry region determination means re-accelerates the rotation of the three-phase electric motor in the steering direction by the retry acceleration means is retried. When the state in the area is continued, a retry counter for counting the number of retries is provided.
Further, a fifth aspect of the electric power steering apparatus according to the present invention is configured such that the retry region determination means increases the retry region based on the electric angle and the direction of the steering torque.
According to a sixth aspect of the electric power steering apparatus of the present invention, the retry acceleration means causes the abnormal time phase current command value outside the acceleration region when the number of retries of the retry counter exceeds a threshold value. Is increased according to the number of retries.

  According to the present invention, when an abnormality occurs in one phase in a three-phase electric motor, motor driving can be continued using the remaining two phases. At this time, when the sum of the steering torque and the steering assist torque generated by the three-phase electric motor is balanced with the external force, when the torque reduction region cannot be overcome, the abnormal time phase current command value is decreased and the electric angle is generated by the external force. Then, the command current value is increased and the motor is accelerated to reliably overcome the torque reduction region. As a result, even in the vicinity of straight running where the steering torque is small, or even when the vehicle speed is low and the steering torque is large, the torque reduction region where the motor torque decreases can be reliably jumped over by the motor inertia force, and a smooth steering feeling can be achieved. Can do.

1 is a system configuration diagram of an electric power steering apparatus according to the present invention. It is a block diagram which shows the specific structure of a steering assistance control apparatus. It is a block diagram which shows the specific structure of the control arithmetic unit 23 in 1st Embodiment. It is a steering auxiliary current command value calculation map. It is a block diagram which shows the specific structure of the d-axis current command value calculation part of a vector phase command value calculation circuit. It is a characteristic diagram which shows the storage table for dq axis voltage calculation. It is a characteristic diagram which shows the induced voltage waveform which generate | occur | produces with the three-phase brushless motor at the time of normal. It is explanatory drawing which shows the stator magnetic field model at the time of two-phase electricity supply in a three-phase brushless motor. It is a characteristic diagram which shows the motor induced voltage at the time of two-phase electricity supply in a three-phase brushless motor. It is a block diagram which shows the specific structure of a motor acceleration area | region determination part. It is a block diagram which shows the specific structure of a round-off switch-back determination part. It is a block diagram which shows the specific structure of a torque fall area | region determination part. It is a flock figure which shows the specific structure of a correction | amendment electric current command gain production | generation part. It is a figure which shows the example of a switchback correction gain. It is a block diagram which shows the specific structure of a retry count part. It is a block diagram which shows the specific structure of a retry current gain production | generation part. It is explanatory drawing which shows a retry area | region. It is a block diagram which shows the specific structure of the electric current command value production | generation part for two-phase control. It is a figure which shows the motor current and motor torque at the time of additional steering at the time of phase abnormality. It is a characteristic line figure which shows the basic current value of two phases at the time of phase abnormality, and motor torque.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
(Constitution)
FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.
In the figure, reference numeral 1 denotes a steering wheel, and a steering force applied to the steering wheel 1 from a driver is transmitted to the steering shaft 2. The steering shaft 2 has an input shaft 2a and an output shaft 2b. One end of the input shaft 2 a is connected to the steering wheel 1, and the other end is connected to one end of the output shaft 2 b via the steering torque sensor 3.

  The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear 8 and steers steered wheels (not shown). Here, the steering gear 8 is configured in a rack-and-pinion type having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a. It has been converted to a straight motion in the width direction.

A steering assist mechanism 10 for transmitting a steering assist force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The steering assist mechanism 10 includes a reduction gear 11 connected to the output shaft 2 b and a three-phase brushless motor 12 as a three-phase electric motor that generates a steering assist force connected to the reduction gear 11.
The steering torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the steering torque sensor 3 is a torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b. It is configured to convert to a torsional angular displacement, and to detect this by converting the torsional angular displacement into a resistance change or a magnetic change.

  As shown in FIG. 2, the three-phase brushless motor 12 has one end of the A-phase coil La, the B-phase coil Lb, and the C-phase coil Lc connected to each other to form a star connection, and the coils La, Lb, and Lc are connected to each other. The other end is connected to the steering assist control device 20, and motor drive currents Ia, Ib, and Ic are individually supplied. The three-phase brushless motor 12 includes a rotor rotation angle detection circuit 13 that includes a Hall element, a resolver, and the like that detect the rotational position of the rotor.

  The steering assist control device 20 receives the steering torque T detected by the steering torque sensor 3 and the vehicle speed Vs detected by the vehicle speed sensor 21, and the rotor rotation angle θm detected by the rotor rotation angle detection circuit 13. Entered. Further, the steering assist control device 20 is further output from a motor current detection circuit 22 that detects motor drive currents Ia, Ib, and Ic supplied to the phase coils La, Lb, and Lc of the three-phase brushless motor 12. Motor drive current detection values Iad, Ibd and Icd are input.

  The steering assist control device 20 calculates a steering assist current command value based on the steering torque T, the vehicle speed Vs, the motor current detection values Iad, Ibd and Icd, and the rotor rotation angle θm, and each phase motor voltage command value Va, A control arithmetic unit 23 that outputs Vb and Vc is provided. Further, the steering assist control device 20 includes a motor drive circuit 24 composed of a field effect transistor (FET) that drives the three-phase brushless motor 12, and phase voltage command values Va, Vb, and Vc output from the control arithmetic device 23. And an FET gate drive circuit 25 for controlling the gate current of the field effect transistor of the motor drive circuit 24. Further, the steering assist control device 20 includes a cutoff relay circuit 26 connected between the motor drive circuit 24 and the three-phase brushless motor 12, and motor drive currents Ia, Ib and Ic supplied to the three-phase brushless motor 12. And an abnormality detection circuit 27 for detecting the abnormality.

(Configuration of the control arithmetic unit 23)
FIG. 3 is a block diagram showing a specific configuration of the control arithmetic device 23.
As shown in FIG. 3, the control arithmetic device 23 includes a steering auxiliary current command value calculation unit 31, an angle information calculation unit 32, a normal motor command value calculation unit 33, and an abnormal motor command value calculation unit 34. A value output unit 30, a command value selection unit 35, and a motor current control unit 36 are provided.
The steering assist current command value calculation unit 31 inputs the steering torque T detected by the steering torque sensor 3 and the vehicle speed Vs detected by the vehicle speed sensor 21, and calculates the steering assist current command value Iref based on these.
The angle information calculation unit 32 calculates an electrical angle θe based on the rotor rotation angle θm detected by the rotor rotation angle detection circuit 13, and the electrical angle θe output from the electrical angle conversion unit 32a. For example, a motor rotation speed calculation unit 32b that calculates the motor rotation speed ωm.

Here, the steering torque sensor 3 is configured to output the steering torque T with a sign, for example, assuming that the generated torque during right steering is a positive value and the generated torque during left steering is a negative value. Similarly, the motor rotation speed calculation unit 32b of the three-phase brushless motor 12 assigns a code according to the rotation direction of the three-phase brushless motor 12, for example, in the case of a rotation direction that applies a steering assist force when steering in the right direction. Is provided with a positive value and a negative value in the case of a rotational direction in which a steering assist force is applied during leftward steering.
The normal motor command value calculation unit 33 calculates three-phase current command values (normal phase current command values) Iaref to Icref based on the steering assist current command value Iref, the electrical angle θe, and the electrical angular velocity ωe.

  The abnormal-time motor command value calculation unit 34 is configured based on a phase abnormality detection signal AS, a steering assist current command value Iref, an electrical angle θe, and an electrical angular velocity ωe that are input from an abnormality detection circuit 27 described later. Two-phase current command values (abnormal time phase current command values) Iiref and Ijref for a to c) and Lj (j = b to a) are calculated. At this time, as shown in FIG. 19, the two-phase current command values Iiref and Ijref as the basic current command values are calculated with opposite signs and equal absolute values. In other words, the sum of the two-phase current command values Iiref and Ijref is zero, and these signs are inverted at a common electrical angle θe.

The command value selection unit 35 selects the three-phase current command values Iaref to Icref output from the normal motor command value calculation unit 33 when the phase abnormality detection signal AS is “0” based on the phase abnormality detection signal AS. Then, when the phase abnormality detection signal AS is a value other than “0”, the two-phase current command values Iiref and Ijref output from the abnormal-time motor command value calculation unit 34 are selected.
The motor current control unit 36 performs current feedback processing using the current command value selected by the command value selection unit 35 and the motor current detection values Iad, Ibd, and Icd detected by the motor current detection circuit 22.

Hereinafter, processing executed in each block will be described in detail.
The steering assist current command value calculation unit 31 calculates the steering assist current command value Iref based on the steering torque T and the vehicle speed Vs with reference to the steering assist current command value calculation map shown in FIG. As shown in FIG. 4, the steering assist current command value calculation map has a parabolic curve with the steering torque T on the horizontal axis, the steering assist current command value Iref on the vertical axis, and the vehicle speed detection value Vs as a parameter. It consists of a characteristic diagram represented by

This characteristic diagram shows that the steering assist current command value Iref is maintained at “0” from the time when the steering torque T is “0” to the set value Ts1 in the vicinity thereof, and at first, when the steering torque T exceeds the set value Ts1. The steering assist current command value Iref increases relatively slowly as the steering torque T increases, but is set so that when the steering torque T further increases, the steering assist current command value Iref increases steeply. Has been. Further, this characteristic curve is set so that the inclination becomes smaller as the vehicle speed Vs increases.
The angle information calculation unit 32 differentiates the electrical angle conversion unit 32a that converts the rotor rotation angle θm detected by the rotor rotation angle detection circuit 13 into the electrical angle θe, and the electrical angle θe output from the electrical angle conversion unit 32a. And a differentiation circuit 32b for calculating an electrical angular velocity ωe representing the motor rotation speed.

  As shown in FIG. 3, the normal motor command value calculation unit 33 is a d-axis current command value calculation unit 33a that calculates a d-axis current command value Idref based on the steering assist current command value Iref and the electrical angular velocity ωe. A d-q axis voltage calculation unit 33b that calculates the d-axis voltage ed (θe) and the q-axis voltage eq (θe) based on the angle θe is provided. The normal motor command value calculator 33 outputs the d-axis voltage ed (θe) and the q-axis voltage eq (θe) output from the dq-axis voltage calculator 33b and the d-axis current command value calculator 33a. The q-axis current command value calculation unit 33c calculates the q-axis current command value Iqref based on the d-axis current command value Idref and the steering assist current command value Iref output from the steering assist current command value calculation unit 31. Dq-axis current command value calculation unit 33d. Further, the normal motor command value calculation unit 33 includes a d-axis current command value Idref output from the d-axis current command value calculation unit 33a and a q-axis current command value Iqref output from the q-axis current command value calculation unit 33c. Is converted to a three-phase current command value Iaref, Ibref, and Icref.

As shown in FIG. 5, the d-axis current command value calculation unit 33a converts the steering assist current command value Iref output from the steering assist current command value calculation unit 31 into a base angular velocity ωb for the three-phase brushless motor 12. The mechanical angular velocity ωm (= ωe / P) of the motor is calculated from the unit 51, the absolute value portion 52 that calculates the absolute value | Iref | of the steering assist current command value Iref, and the electrical angular velocity ωe and the number of magnetic poles P of the motor. A mechanical angle calculation unit 53, an acos calculation unit 54 that calculates an advance angle Φ = acos (ωb / ωm) based on the base angular velocity ωb and the mechanical angular velocity ωm, and a sin calculation unit 55 that calculates sin Φ based on the advance angle Φ. And the absolute value | Iref | from the absolute value unit 52 and sinΦ output from the sin calculation unit 55 are multiplied by −1 to obtain a d-axis current command value Idref (= − | Iref | si And a multiplier 56 for obtaining the [Phi).
By configuring the d-axis current command value calculation unit 33a in this way, the d-axis current command value Idref is
Idref = − | Iref | · sin (acos (ωb / ωm)) (1)
It becomes.

  Regarding the term of acos (ωb / ωm) in the above equation (1), when the rotational speed of the motor is not high, that is, when the mechanical angular speed ωm of the three-phase brushless motor 12 is lower than the base angular speed ωb, ωm <ωb Therefore, acos (ωb / ωm) = 0, so that Idref = 0. However, during high-speed rotation, that is, when the mechanical angular velocity ωm becomes higher than the base angular velocity ωb, the value of the current command value Idref appears and field weakening control is started. Since the current command value Idref varies depending on the rotational speed of the three-phase brushless motor 12 as expressed in the above formula (1), it is possible to smoothly perform control during high-speed rotation without any joints. effective.

Another effect is that the motor terminal voltage is saturated. The phase voltage V of the motor is generally
V = E + R · I + L (di / dt) (2)
It is represented by Here, E is a counter electromotive voltage, R is a fixed resistance, and L is an inductance. The counter electromotive voltage E increases as the motor rotates at a higher speed, and the power supply voltage such as the battery voltage is fixed, so that the voltage range that can be used for motor control becomes narrower. The angular velocity at which this voltage saturation is reached is the base angular velocity ωb, and when voltage saturation occurs, the duty ratio of PWM control reaches 100%, and beyond this, it becomes impossible to follow the current command value, resulting in an increase in torque ripple.

  However, the current command value Idref expressed by the above equation (1) has a negative polarity, and the induced voltage component of the current command value Idref related to L (di / dt) in the above equation (2) is the back electromotive force E and The polarity is reversed. Therefore, an effect of reducing the counter electromotive voltage E, the value of which increases as the rotation speed increases, is reduced by the voltage induced by the current command value Idref. As a result, even if the three-phase brushless motor 12 rotates at a high speed, the voltage range in which the motor can be controlled by the effect of the current command value Idref is widened. In other words, the field-weakening control by controlling the current command value Idref does not saturate the motor control voltage, so that the controllable range is widened, and the torque ripple can be prevented from increasing even during high-speed rotation of the motor.

  Further, the dq axis voltage calculation unit 33b refers to the dq axis voltage calculation storage table as the three-phase drive storage table shown in FIG. (Θe) and q-axis voltage eq (θe) are calculated. Here, as shown in FIG. 6, the dq-axis voltage calculation storage table has an electrical angle θe on the horizontal axis and a d-axis in which the induced voltage waveform generated by each phase coil is converted into rotational coordinates on the vertical axis. The voltage ed (θ) and the q-axis voltage eq (θ) are taken. When the three-phase brushless motor 12 is a sine wave induced voltage motor in which the induced voltage waveforms A-phase EMF, B-phase EMF, and C-phase EMF are normal sine waves that are 120 degrees different from each other as shown in FIG. As shown in FIG. 6, both ed (θ) and q-axis voltage eq (θ) are constant values regardless of the electrical angle θ.

Furthermore, the q-axis current command value calculation unit 33c converts the input steering assist current command value Iref, d-axis voltage ed (θe), q-axis voltage eq (θe), d-axis current command value Idref, and electrical angular velocity ωe. Based on the calculation of the following equation (3), the q-axis current command value Iqref is calculated.
Iqref = {Kt × Iref × ωe−ed (θe) × Idref (θe)} / eq (θe)
……………… (3)
Here, Kt is a motor torque constant.

(Configuration of the abnormal motor command value calculation unit 34)
When the abnormality occurs in the drive system including the one-phase coil of the three-phase brushless motor 12, the abnormal-time motor command value calculation unit 34 drives the rotation of the three-phase brushless motor 12 using the remaining two-phase coils. The phase current command value for continuing is calculated.
In the three-phase brushless motor 12, for example, as shown in FIG. 8A, when a disconnection occurs in the drive system for the A-phase coil La and the motor current cannot be supplied to the A-phase coil La, the motor current can be supplied. The two coils are the B-phase coil Lb and the C-phase coil Lc. The direction of the current supplied to the B phase coil Lb and the C phase coil Lc is the same as when the motor current is input from the B phase coil Lb and output from the C phase coil Lc, and the motor current is input from the C phase coil Lc. Then, there are two ways of outputting from the B-phase coil Lb.

As shown in FIGS. 8B and 8C, the stator combined magnetic field generated by these motor currents can only be formed in directions different by 180 degrees, so that these stator combined magnetic fields alone are three-phase brushless. The motor 12 cannot be driven in two phases.
Therefore, for example, when an abnormality in energization occurs in the A-phase drive system, the motor-induced voltage when the motor is driven using the remaining B-phase and C-phase is a characteristic with respect to the electrical angle θe as shown in FIG. A combined induced voltage EMFa indicated by a characteristic curve L3 obtained by combining the induced voltages EMFb (θe) and EMFc (θe) indicated by the curves L1 and L2. Then, the phase current command value Im (θe) is calculated based on the combined induced voltage EMFa, and the above-described two-phase current command value is calculated based on the phase current command value Im (θe).
Here, in the present embodiment, when the current electrical angle θe is within a predetermined acceleration region described later, the phase current command value Im (θe) is increased or increased in order to accelerate the three-phase brushless motor 12 in the steering direction. A decreasing correction shall be performed.

Next, a specific configuration of the abnormal-time motor command value calculation unit 34 will be described.
As shown in FIG. 3, the abnormal-time motor command value calculation unit 34 includes a basic current command value generation unit 60, a basic current command gain generation unit 61, a correction current command gain generation unit 62, and a retry current command gain generation unit. 63, the basic current gain Gif output from the basic current command gain generation unit 61, the correction current command gain Gia output from the correction current command gain generation unit 62, and the retry current command output from the retry current command gain generation unit 63 Each phase current command value generation unit 64 for two-phase control that generates two-phase current command values Iiref and Ijref based on the gain Gir is provided. Here, the correction current command gain generation unit 62, the retry current command gain generation unit 63, and each phase current command value generation unit 64 for two-phase control constitute current command value correction means.

The basic current command value generation unit 60 includes an induced voltage calculation unit 60a and a phase current command value calculation unit 60b. The induced voltage calculation unit 60a calculates a combined induced voltage EMFa (θe) based on the electrical angle θe and a phase abnormality detection signal AS output from the abnormality detection circuit 27 described later.
Here, the induced voltage calculation unit 60a is a combined induced voltage calculation storage table showing the relationship between the combined induced voltage EMFa and the electrical angle θe represented by the characteristic curve L3 of FIG. 9 when driving in the B-C2 phase, A synthetic induced voltage calculation table showing the relationship between the combined induced voltage EMFa and the electrical angle θe when driven in the A-B2 phase, and the relationship between the combined induced voltage EMFa and the electrical angle θe when driven in the A-C2 phase. There are three synthesis induced voltage calculation storage tables to be expressed. Then, based on the phase abnormality detection signal AS, the composite induced voltage calculation storage table corresponding to the normal two phases is selected, and the composite induced voltage calculation storage table selected based on the electrical angle θe is referred to for synthesis. The induced voltage EMFa (θe) is calculated.

The phase current command value calculation unit 60b calculates the phase current command value Im (θe) based on the combined induction voltage EMFa (θe) calculated by the induced voltage calculation unit 60a, the steering auxiliary current command value Iref, and the electrical angular velocity ωe. .
That is, the phase current command value calculation unit 60b calculates the phase current command value Im (θe) by performing the following calculation (4).
Im (θe) = (Kt2 × Iref × ωe) / EMFa (θe) (4)
Here, Kt2 is a motor torque constant during two-phase energization.

When the phase abnormality detection signal AS is a value other than “0”, the basic current command gain generation unit 61 sets the electrical angle θe to 0 to 180 ° and 180 ° with respect to two phases other than the phase where the abnormality is detected. Fault-phase-specific angle offset processing unit 65 that performs offset processing to distribute to 360 °, and calculation of reverse-induced pressure characteristic gain that represents the relationship between the offset-processed electrical phase θes after fault-phase shift and the reverse-induced voltage characteristic gain. A back EMF characteristic gain calculation unit 66 having a storage table.
Then, the basic current gain Gif corresponding to the post-shift phase electrical angle θes is supplied from the reverse induced voltage characteristic gain calculation unit 66 to each phase current command value generation unit 64 for two-phase control.
The correction current command gain generation unit 62 includes a cut increase / return determination unit 71, a motor acceleration region determination unit 72, a torque decrease region determination unit 73, and a correction current command gain generation unit 74.

  As shown in FIG. 10, the addition / return determination unit 71 receives a steering torque T detected by the steering torque sensor 3 and inputs a steering torque code determination unit 71 a that determines the sign of the steering torque T, and this steering torque. The determination result of the sign determination unit 71a and the electrical angular velocity ωe are input to determine the rotation direction of the brushless motor, the rotation direction determination unit 71b, the determination result of the rotation direction determination unit 71b, and the determination result of the steering torque code determination unit 71a Is input, and a boost / switchback determination unit 71c that outputs a first switchback flag Fr1 that is "1" in the switchback state is provided.

The steering torque sign determination unit 71a outputs a sign determination output St of a logical value “1” when the steering torque T is a positive value including zero, and a sign of a logical value “0” when the steering torque T is a negative value. A determination output St is output.
When the sign determination output St input from the steering torque sign determination unit 71a is a logical value “1”, the rotation direction determination unit 71b is an absolute value of a value obtained by adding a preset rotation speed hysteresis ωh to the rotation speed ωm. Determines whether or not the rotational speed hysteresis ωh1 is exceeded. When this determination result is | ωm + ωh1 |> ωh1, when the rotational speed ωm is a positive value including 0, a rotational direction determination output Sr having a logical value “1” is output, and the rotational speed ωm is a negative value. When it is, a rotation direction determination output Sr having a logical value “0” is output. When | ωm + ωh1 | ≦ ωh1, the previous output is maintained.

  Further, when the sign determination output St input from the steering torque sign determination unit 71a is a logical value “0”, the rotation direction determination unit 71b has a value obtained by subtracting a preset rotation speed hysteresis ωh2 from the rotation speed ωm. It is determined whether or not the absolute value exceeds the rotational speed hysteresis ωh2. When this determination result is | ωm−ωh2 |> ωh2, when the rotational speed ωm is a positive value including 0, a rotational direction determination output Sr of logical value “1” is output, and the rotational speed ωm is When it is a negative value, a rotational direction determination output Sr having a logical value “0” is output. When | ωm−ωh2 | ≦ ωh2, the previous output is maintained.

  Further, the increase / return determination unit 71c starts from the increase in duration when the rotation direction determination output Sr and the code determination output St are inconsistent based on the input rotation direction determination output Sr and the code determination output St. It is determined whether or not the switching time threshold value for switching to reversal has been exceeded, and the continuation time in which the rotational direction determination output Sr and the sign determination output St are inconsistent exceeds the switching time threshold value for switching from increasing to reverting. If it is, the first return flag Fr1 is set to "1", and in other cases, the increased state is determined and the first return flag Fr1 is set. Reset to "0" and reset internal counter to zero.

  The motor acceleration region determination unit 72b calculates a stable region angle range that is an electrical angle range in which the absolute value of the current value decreases from the maximum value Imax based on the basic current command value Im (θe) shown in FIG. Input from the calculation unit 72a, the return steering stable region correction unit 72b that corrects the stable region angle range based on the region where the first return flag Fr1 is set to “1”, and the retry count unit 81 described later. A retry return steering stable region correction unit 72c that corrects an increase in acceleration region due to retry return steering based on the number of retry times Nr, and a stable region angle θsa output from the retry return steering stable region correction unit 72c. And an electrical angle θes after the shift for each fault phase, it is determined whether or not the acceleration region is within the stable region angle θsa, and an acceleration region determination flag Fa is output. And a region determination unit 72d.

Here, the acceleration region determination unit 72d determines that it is within the acceleration region and sets the acceleration region determination flag Fa when the electrical phase θes after failure phase shift is equal to or larger than the stable region angle θsa (θes ≧ θsa). Otherwise, it is determined that it is within the stable region, and the acceleration region determination flag Fa is reset to “0”.
The acceleration region is set to a predetermined angle region straddling the electrical angle θe where the sign of the phase current command value Im (θe) calculated by the phase current command value calculation unit 60b described above is reversed. Specifically, in the acceleration region, the phase current command value Im (θe) corresponds to the upper limit of the current value that can be energized in the drive system of each phase coil (can be output by the motor drive circuit 24). The angle region includes the front and rear of the angle region that has reached the maximum current value Imax).

An electric current in which one of the three-phase brushless motors 12 is abnormally energized and the three-phase brushless motor 12 is rotationally driven based on the two-phase current command value, the sign of the phase current command value Im (θe) is reversed. The motor torque is always zero at the angle θe. Therefore, the acceleration region can be said to be an angle region straddling the electrical angle θe where the motor torque becomes zero.
As shown in FIG. 12, the torque decrease region determination unit 73 determines whether or not the current command values Iiref and Ijref are equal to or greater than a torque decrease region determination current threshold Itd that is close to the maximum current value Imax. 73a, a rotation speed comparison unit 73b that determines whether or not the motor rotation speed ωm is equal to or less than the torque reduction region determination rotation speed threshold ωtm, the acceleration region determination flag Fa, the comparison output of the current command value comparison unit 73a, and A determination unit 73c that determines whether or not the comparison output of the rotation speed comparison unit 73b is within the torque reduction region.

Here, the current command value comparison unit 73a outputs the comparison output Cti of the logical value “1” when the absolute values of the current command values Iiref and Ijref are equal to or greater than the torque reduction region determination current threshold Itd, and otherwise A comparison output Cti having a logical value “0” is output to
The rotation speed comparison unit 73b outputs a comparison output Ctv having a logical value “1” when the absolute value of the rotation speed ωm is equal to or less than the torque reduction region determination rotation speed threshold ωtm, and otherwise compares the logical value “0”. Output Ctv.

  The determination unit 73c is a duration when the acceleration region determination flag Fa is set to “1”, the current command value determination output Sti is the logical value “1”, and the rotation speed determination output Stv is the logical value “1”. When the torque reduction region determination time threshold is exceeded or when the first return flag Fr1 is set to “1”, it is determined that the current state is the return state and the second return flag Fr2 is set to “1”. In other cases, it is determined that the state is increased, and the second return flag Fr2 is reset to “0” and the internal counter is reset to zero.

The correction current command gain generation unit 74 includes a gain calculation unit 74a that calculates a correction current gain at switchback / increase based on the current command values Iiref and Ijref, an acceleration region determination flag Fa, and a second switchback flag Fr2. And an input current gain calculation unit 74b.
Here, the gain calculation unit 74a calculates the return correction current gain Girv with reference to the gain calculation map shown in FIG. 14 at the time of switchback and sets it in the gain calculation unit 74b. An increased correction current gain is set in the gain calculation unit 74b, and a preset stable region correction current gain is set in the gain calculation unit 74b when the current command values Iiref and Ijref are in the stable region.

Here, as shown in FIG. 14, the return correction current gain Girv becomes a positive value slightly larger than 0 when | Im (θe) | ≧ Im (θe) _TH2 , and | Im (θe) | < When Im (θe) _TH1 , the minimum value is -Girmin. Here, Girmin ≦ 1. Further, the return-correction current gain Girv _{is, Im (θe) TH1 ≦ |} Im (θe) | <Im (θe) when a f _TH2, the basic current instruction value | from -Girmin as increases | Im (.theta.e) It sets so that it may change gradually to Girmax.

That is, when | Im (θe) | ≧ Im (θe) _TH2 , correction is performed to decrease the absolute value of the phase current command value Im (θe). On the other hand, if | Im (θe) | <Im (θe) _TH1 , the sign of the phase current command value Im (θe) is reversed and corrected to decrease.
If Im (θe) _TH1 ≦ | Im (θe) | <Im (θe) _TH2 , the correction amount of the phase current command value Im (θe) is gradually reduced with reference to the steering assist current command value Iref. To prevent sudden changes. Thus, a gradual change region is provided in which the correction amount of the phase current command value Im (θe) is gradually changed according to the steering assist current command value Iref.
Here, the threshold values Im (θe) _TH1 and Im (θe) _TH2 are set based on a steering assist current command value generated by an external load related to the motor to the extent that a rotational force is applied to the motor.

  The gain calculation unit 74b sets the return correction current gain calculated in FIG. 14 to the correction current command gain Gia when the acceleration region determination flag Fa is set to “1” and the return flag Fr is set to “1”. To each phase current command value generation unit 64 for two-phase control. Further, the gain calculation unit 74b uses the two-phase correction correction current gain as the correction current command gain Gia when the acceleration region determination flag Fa is set to “1” and the switchback flag Fr is reset to “0”. It outputs to each phase electric current command value generation part 64 for control. Furthermore, the gain calculation unit 74 outputs the stable region correction current gain as the correction current command gain Gia to each phase current command value generation unit 64 for two-phase control in a state other than the above two states.

  The retry current command gain generation unit 63 includes a retry count unit 81 and a retry current command gain calculation unit 82. As shown in FIG. 15, the retry count unit 81 includes a retry continuation determination unit 81 a that determines whether the electrical angle θes after the failure phase shift is continued within the retry region, and a return of the second return flag Fr 2. State change determination unit 81b that determines a state change from the state to the increase state and outputs the change back → increase change flag Fri, determination output Srt of the retry continuation determination unit 81a, and return of the state change determination unit 81b A retry number counting unit 81c for calculating the number of retry times Nr based on the increment change flag Fri.

Here, the retry continuation determining unit 81a receives the torque comparison unit 81d that compares the steering torque T with the steering torque threshold value Tt, and the electrical phase θes after the failure phase shift and the steering torque T to input the retry region electrical angle θrt. A retry area electrical angle calculation unit 81e to be calculated, a retry electrical angle comparison unit 81f that compares the post-shift phase electrical angle θes and the retry area electrical angle θrt, and a comparison output Cti of the retry electrical angle comparison unit 81f is 1 A delay circuit 81g that delays the number of times, a match detection circuit 81h that compares the current comparison output Cti (n) with the previous comparison output Cti (n-1) and determines whether or not they match, and a match detection An AND circuit 81i that takes a logical product of the output Sco of the circuit 81h and the comparison output Stc of the torque comparison unit 81d is provided.
The torque comparison unit 81d compares the steering torque T with the steering torque threshold value, and outputs the comparison output Ctc having the logical value “1” to the AND circuit 81i when the steering torque T is equal to or greater than the steering torque threshold value. Sometimes, the comparison output Ctc having the logical value “0” is output to the AND circuit 81i.

  When the steering torque T is a positive value including 0, the retry region electrical angle calculation unit 81e is a value obtained by adding the retry region offset value Δθo to 180 ° when the electrical phase θes after failure phase shift is less than 180 °. Is output as the retry area electrical angle θrt (= 180 ° + Δθo) to the retry electrical angle comparison unit 81f, and when the electrical angle θes after shifting by failure phase is 180 ° or more, a value obtained by adding the retry area offset value Δθo to 0 ° Is output to the retry electrical angle comparison unit 81f as the retry region electrical angle θrt (= 0 ° + Δθo). Similarly, when the steering torque T is a negative value, the retry area electrical angle calculation unit 81e is a value obtained by subtracting the retry area offset value Δθo from 180 ° when the electrical phase θes after failure phase shift is less than 180 °. Is output to the retry electrical angle comparison unit 81f as the retry region electrical angle θrt (= 180 ° −Δθo), and the retry region offset value Δθo is subtracted from 0 ° when the electrical angle θes after shift by failure phase is 180 ° or more. The value is output to the retry electrical angle comparison unit 81f as the retry region electrical angle θrt (= 0 ° −Δθo).

The retry electrical angle comparison unit 81f compares the post-shift phase electrical angle θes with the retry region electrical angle θrt, and outputs a comparison output Cti having a logical value “1” when θes <θrt, and θes ≧ θrt. When it is, the comparison output Cti having the logical value “0” is output.
When the second switchback flag Fr2 changes from “1” to “0”, that is, when the state changes from the switchback state to the switchover state, the state change determination unit 81b sets the switchback → switchover change flag Fri to “1”. In other cases, the switch-over → switch-up change flag Fri is reset to “0”.

When the determination result of the retry continuation determining unit 81a is continuation within the retry area electrical angle, the retry number counting unit 81c sets the retry number Nr to “1” every time the reversion → switch increase change flag Fri becomes “1”. When the determination result of the retry continuation determination unit 81a is not within the retry area electrical angle, the retry number Nr is cleared to “0”, and the retry number Nr is generated as the retry current command gain generation unit 82 and the correction current command gain generation. To the motor acceleration area determination unit 72 of the unit 62.
As shown in FIG. 16, the retry current command gain generation unit 82 is a retry gain output determination unit 82a to which the number of retries Nr and the second return flag Fr2 are input, and the determination result of the retry gain output determination unit 82a. And a retry current command gain calculator 82b to which the retry number Nr is input.

Here, the retry gain output determination unit 82a outputs a retry gain when the number of retries Nr is equal to or greater than a preset threshold value Ns and the second return flag Fr2 is set to “1”. The retry gain output determination signal Srg having the logical value “1” is output to the retry current command gain calculation unit 82b, and in other cases, it is determined that the retry gain is not output, and the logical value “0” is output. The retry gain output determination signal Srg is output to the retry current command gain calculator 82b.
When the retry gain output determination signal Srg is the logical value “1”, the retry current command gain calculation unit 82b multiplies the retry current command reference gain Girb by the number of retries Nr to the retry current command gain Gir. (= Gitb * Nr) is output to each phase current command value generation unit 64 for two-phase control.

  As shown in FIG. 18, each phase current command value generation unit 64 for two-phase control has a basic current command gain Gif output from the basic current command gain generation unit 61 and a correction output from the correction current command gain generation unit 62. A multiplier 64a that multiplies the current gain Gia, and an adder that adds the retry current command gain Gir output from the retry current command gain generation unit 63 after bit adjustment of the multiplication output of the multiplier 64a by the bit adjustment circuit 64b. 64c, a multiplier 64d for multiplying the addition output of the adder 64c by the basic current command value Im (θe), a bit adjustment circuit 64e for bit adjustment of the multiplication output of the multiplier 64d, and the bit adjustment circuit 64e The phase current command value limiting circuit 64f that limits the output phase current command value with the maximum value and the phase current command value limiting circuit 64f A rate limiter 64g for limiting the amount of change in the phase current command value, and each phase current selection calculation unit 64h to which the current command value Im output from the rate limiter 64g and the phase abnormality detection signal AS are input. Yes.

  Here, each phase current selection calculation unit 64h sets the phase A current command value Iaref to 0 and the phase B current command value Ibref to -Im when the phase abnormality detection signal AS indicates a phase A failure. Then, the C phase current command value is set to + Im. Each phase current selection calculation unit 64h sets the A-phase current command value Iaref to + Im and sets the B-phase current command value Ibref to 0 when the phase abnormality detection signal AS indicates a B-phase failure. C-phase current command value Icref is set to -Im. Furthermore, each phase current selection calculation unit 64h sets the A-phase current command value Iaref to -Im and sets the B-phase current command value Ibref to + Im when the phase abnormality detection signal AS indicates a C-phase failure. C phase current command value Icref is set to zero.

The command value selection unit 35 includes changeover switches 91a, 91b, and 91c, and a selection control unit 92 that controls the changeover switches 91a, 91b, and 91c.
The normally closed contacts of the changeover switches 91a, 91b and 91c are input with the respective phase current command values Iaref, Ibref and Icref calculated by the two-phase / three-phase conversion unit 33e of the normal motor command value calculation unit 33. The normally open contacts are input with the phase current command values Iaref, Ibref and Icref output from the motor command value calculation unit 34 at the time of abnormality.

  When the phase abnormality detection signal AS output from the abnormality detection circuit 27 is “0” indicating that all phases are normal, the selection control unit 92 selects the normally closed contacts for the changeover switches 91a to 91c. In addition to outputting a selection signal of the logical value “0” to be performed, a relay control signal for controlling these to be turned on is output to the cutoff relay circuits RLY1 to RLY3 described later. On the other hand, when the phase abnormality detection signal AS is not “0”, a selection signal of a logical value “1” for selecting the normally open contact is output to the changeover switches 91a to 91c, and it corresponds to the drive system that has become abnormal. A relay control signal for controlling the cut-off relay circuit RLYx (x = a to c) to an off state is output.

The motor current control unit 36 detects a motor phase current value Iad flowing in each phase coil La, Lb, Lc detected by the current detection circuit 22 from each phase current command value Iaref, Ibref, Icref supplied from the command value selection unit 35. , Ibd, Icd are subtracted to obtain respective phase current errors ΔIa, ΔIb, ΔIc, and proportional integral control is performed on the obtained respective phase current errors ΔIa, ΔIb, ΔIc to obtain a command voltage. And a PI control unit 102 for calculating Va, Vb, and Vc.
Then, command voltages Va, Vb, and Vc output from the PI control unit 102 are supplied to the FET gate drive circuit 25.

As shown in FIG. 2, the motor drive circuit 24 includes switching elements Qaa, Qab, Qba, Qbb and Qca, Qcb composed of N-channel MOSFETs connected in series corresponding to the phase coils La, Lb, and Lc. Are connected in parallel. The connection points of the switching elements Qaa and Qab, the connection points of Qba and Qbb, and the connection point of Qca and Qcb are connected to the opposite side of the neutral point Pn of the phase coils La, Lb and Lc, respectively.
Then, a PWM (pulse width modulation) signal output from the FET gate drive circuit 25 is supplied to the gates of the switching elements Qaa, Qab, Qba, Qbb and Qca, Qcb constituting the motor drive circuit 24.

  Further, the interrupting relay circuit 26 includes terminals opposite to the neutral points Pn of the phase coils La, Lb, and Lc of the three-phase brushless motor 12 and field effect transistors Qaa, Qab, Qba, Qbb of the motor drive circuit 24. And relay contacts RLY1, RLY2, and RLY3 that are individually inserted between the connection points of Qca and Qcb. Each relay contact RLY <b> 1 to RLY <b> 3 is controlled to be turned on / off by a relay control signal output from the selection control unit 92. At this time, in the normal state where no abnormality is detected in all phases by the abnormality detection circuit 27, it is controlled to the closed state (ON state), and the relay contact of the phase that becomes abnormal when an abnormality is detected in any one phase RYLi (i = 1 to 3) is controlled to an open state (off state).

  Furthermore, the abnormality detection circuit 27 compares the voltage command values Va, Vb and Vc supplied to the FET gate drive circuit 25 or the pulse width modulation signal supplied to the motor drive circuit 24 with the motor voltage of each phase. Phase, B-phase, and C-phase discontinuities and short-circuit abnormalities can be detected. In the abnormality detection circuit 27, when all of the A phase, the B phase and the C phase are normal, “0”, “A1” when the A phase non-conducting abnormality occurs, “A2” when the A phase short circuit abnormality occurs, The control arithmetic unit 23 detects a phase abnormality detection signal AS that is “B1” when the phase is not conductive, “B2” when the B phase is short, “C1” when the C phase is abnormal, and “C2” when the C phase is short. It outputs to the hour motor command value calculation unit 34 and the command value selection unit 35.

The steering torque sensor 3 in FIG. 1 corresponds to the steering torque detection means, the vehicle speed sensor 21 corresponds to the vehicle speed detection means, the steering assist control device 20 corresponds to the motor control means, and the abnormality detection circuit 27 in FIG. It corresponds to the coil phase abnormality detection means.
3 corresponds to the steering assist current command value calculating means, the normal motor command value calculating section 33 corresponds to the normal motor command value calculating means, and the abnormal motor command value. The calculation unit 34 corresponds to an abnormal motor command value calculation unit, and the command value selection unit 35 and the motor current control unit 36 correspond to a motor drive control unit. Further, the motor acceleration region determination unit 72 corresponds to the acceleration region determination unit, and the retry current command gain generation unit 63 corresponds to the retry acceleration unit.

Next, the operation of the above embodiment will be described.
(Operation)
Next, the operation of the above embodiment will be described.
Now, it is assumed that the field effect transistors Qaa to Qcb constituting the motor drive circuit 24 are normal and that the phase coils La to Lc of the three-phase brushless motor 12 are in a normal state in which no disconnection or ground fault occurs. . In this case, since the abnormal state is not detected by the abnormality detection circuit 27, the abnormality detection circuit 27 uses the abnormal-time motor command value calculation unit 34 and the command value selection unit as the phase abnormality detection signal AS representing “0”. 35.

  Therefore, the selection control unit 92 of the command value selection unit 35 outputs a selection signal having a logical value “0” to the changeover switches 91a to 91c. Accordingly, the selector switches 91 a to 91 c select the normally closed contact side, and the phase current command values Iaref to Icref output by the normal motor command value calculation unit 33 are supplied to the motor current control unit 36. At the same time, relay control signals for controlling the relay contacts RLY1 to RLY3 to be closed are output.

Thereby, the motor drive currents Ia, Ib and Ic output from the motor drive circuit 24 are supplied to the respective phase coils La, Lb and Lc of the three-phase brushless motor 12 via the relay contacts RLY1, RLY2 and RLY3. That is, motor drive control using a three-phase coil is performed.
At this time, assuming that the vehicle is stopped and the driver is not steering the steering wheel 1, the normal motor command value calculation unit 33 of the control arithmetic device 23 performs the phase current command values Iaref, Ibref and Icref is calculated to be “0”. At this time, when the three-phase brushless motor 12 is stopped, the motor currents Ia, Ib, and Ic supplied to the phase coils La, Lb, and Lc are also “0”, and the three-phase brushless motor 12 is stopped. To maintain.

  When the steering wheel 1 is changed from a non-steering state to a so-called stationary state in which the steering wheel 1 is steered when the vehicle is stopped, the steering torque sensor 3 detects a large steering torque T accordingly. Therefore, the normal motor command value calculation unit 33 calculates the phase current command values Iaref, Ibref and Icref according to the steering torque T, and supplies these to the motor current control unit 36.

  Then, the motor current control unit 36 calculates command voltages Va, Vb, and Vc based on the phase current command values Iaref, Ibref, and Icref, and supplies them to the FET gate drive circuit 25. Thereby, each field effect transistor of the motor drive circuit 24 is controlled, and the three-phase brushless motor 12 is rotationally driven. For this reason, the three-phase brushless motor 12 generates a steering assist force corresponding to the steering torque T input to the steering wheel 1, and this is transmitted to the steering shaft 2 via the reduction gear 11. The steering wheel 1 can be steered with a light steering force.

  From this normal state, for example, the field effect transistor Qaa or Qab of the drive system that drives the A-phase coil La, that is, the motor drive circuit 24 remains off, or a disconnection occurs in the energization path including the A-phase coil La. Thus, it is assumed that an abnormality that causes the A-phase coil La to become non-conductive occurs. In this case, the abnormality detection circuit 27 detects the abnormality, and the abnormality detection circuit 27 outputs the “A1” phase abnormality detection signal AS representing the A-phase continuity abnormality to the abnormal motor command value calculation unit 34 and the command value selection unit 35. To supply.

For this reason, the selection switches 91a to 91c are switched from the normally closed contact side to the normally open contact side. Therefore, the phase current command value supplied to the motor current control unit 36 is obtained from the phase current command values Iaref to Icref output from the normal motor command value calculation unit 33, and the phase current command output from the motor command value calculation unit 34 at the time of abnormality. The value is switched to values Iaref to Icref.
In the abnormal motor command value calculation unit 34, since the phase abnormality detection signal AS input from the abnormality detection circuit 27 is “A1”, the induced voltage calculation unit 60a receives the electrical angle θe input from the angle information calculation unit 32. Based on the above, a combined induced voltage EMFa (θe) of the V-phase induced voltage and the W-phase induced voltage is calculated. The calculated combined induced voltage EMFa (θe) is supplied to the phase current command value calculation unit 60b, and the phase current command value calculation unit 60b performs the calculation of the equation (4) to obtain the basic phase current command value Im ( θe) is calculated.

  As shown in FIG. 17A, the basic phase current command value Im (θe) becomes a minimum positive value when the electrical angle θe = 0 °, and then increases as the electrical angle θe increases, and the electrical angle θe. Becomes the maximum current value in the vicinity of 60 °, and then the electrical angle θe is reversed in sign at 90 ° to become the maximum negative value, and then the electrical angle θe gradually decreases from the maximum negative value in the vicinity of 110 °. When the electrical angle θe is 180 °, the absolute value becomes the minimum value.

  As shown in FIG. 17B, the motor torque generated by the brushless motor 12 by this basic phase current command value Im (θe) until the basic phase current command value Im (θe) reaches a positive maximum current value. Maintains a constant value, and when the basic phase current command value Im (θe) reaches the maximum positive current value, it decreases as the electrical angle θe increases, and the basic phase current command value Im (θe) is inverted in sign. When the electrical angle θe to be turned is 90 °, the motor torque becomes “0”.

Thereafter, when the electrical angle θe increases beyond 90 °, the motor torque also recovers as the electrical angle θe increases, and reaches a constant torque when the absolute value of the basic phase current command value Im (θe) starts to decrease. After returning, the motor torque maintains a constant value regardless of the increase in the electrical angle θe.
Here, a region where the motor torque is decreasing from a constant value is a motor torque reduction region Atd, and includes the motor torque reduction region Atd and a motor torque generation region Atg that can increase the motor torque on both sides to the maximum value. An acceleration area Aa is set.

  At this time, if the steering wheel 1 is turned to the right, for example, and the steering electrical angle θe does not reach the acceleration region and is in the stable region, the motor acceleration region determination unit 72 outputs the acceleration region determination flag Fa = 0. To do. At this time, when the driver is steering the steering wheel 1 in the increasing direction, the increasing / returning determination unit 71 sets the first return flag Fr1 to “0” indicating the increased state. Reset to.

Therefore, since the electrical angle θe is in the stable region, torque shortage does not occur, and the torque reduction region determination unit 73 resets the acceleration region determination flag Fa to “0” and sets the current command value Im (θe). Since the absolute value is also smaller than the torque reduction region determination current threshold, the comparison output Cti of the current command value comparison unit 73a is also a logical value “0”, and the motor rotation speed ωm is also higher than the torque reduction region determination rotation speed. Accordingly, in the determination unit 73c, the second switchback flag Fr2 is reset to “0” representing the increased state.
Therefore, in the correction current command gain generation unit 74, the stable region correction current gain is supplied as the correction current command gain Gia to each phase current command value generation unit 64 for two-phase control.

  On the other hand, in the retry current command gain generation unit 63, the state in which the second switchback flag Fr2 is reset to “0” continues and there is no state change. The reversion → cut increase change flag Fri is maintained at “0”, and the retry count unit 81c maintains the state where the retry count Nr is cleared to “0”. At this time, in the retry region continuation determination unit 81a, if the steering torque T detected by the steering torque sensor 3 is large, the comparison output output from the steering torque comparison unit 81d becomes the logical value “1”, and the retry region electrical The retry region electrical angle θrt calculated by the angle calculator 81e is a positive value because the steering torque T is in the right-turn state, and θrt = 180 ° + retry region offset value Δθo assuming that the electrical angle θe is less than 180 °. It becomes. For this reason, as shown in FIG. 17, the retry area is shifted to the right by the retry area offset value Δθo shown by the dotted line with respect to the basic retry area shown by the solid line in the range of electrical angles of 0 ° to 180 °. For this reason, since the electrical angle θe is smaller than the retry region electrical angle θrt in the retry region electrical angle comparison unit 81f, a comparison output Cti (n) having a logical value “1” is output. At this time, if the previous comparison output Cti (n−1) has an electrical angle θe exceeding 180 ° and less than 360 ° and a logical value “0”, a mismatch is detected by the matching circuit 81h. The output is a logical value “0”, and the output of the AND circuit 81i is a logical value “0” regardless of whether the steering torque T is greater than the steering torque threshold, indicating that the retry region is not in the electrical angle continuation state. . Therefore, the retry count Nr is cleared to “0” in the retry count unit 81c.

For this reason, the retry current gain generation unit 82 has the retry count Nr “0” and the second switchback flag Fr2 is also reset to “0”, so the retry current command gain calculation unit 82b uses the retry current command gain. Gir is set to “0”.
In each phase current command value generation unit 64 for two-phase control, the basic current gain Gif is calculated by the reverse induced voltage characteristic gain calculation unit 67 based on the post-shift phase-specific electrical angle θes. A retry current command gain Gir of “0” is added to a value obtained by multiplying the current gain Gif by a correction current command gain Gia that is a stable region correction current gain and then the bit adjustment, and this is added to the current command value Im (θe). Therefore, the current command value corresponding to the stable region is obtained, and the maximum value is limited by the phase current command value limiting unit 64f, and the rate of change is limited by the rate limiter 64g. It is supplied to the phase current selection calculation unit 64h.

At this time, in each phase current selection calculation unit 64h, the A phase has failed, so the B phase current command value Ibref is set to -Im, and the C phase current command value Icref is set to + Im. For this reason, the current waveform shown in FIG. 20 is supplied to the B-phase coil Lb and the C-phase coil Lc of the brushless motor 12.
At this time, when the electrical angle θe is 0 ° to 90 °, a current flows from the C-phase coil Lc toward the B-phase coil Lb, and when the electrical angle θe is 90 ° to 270 °, the current flows from the B-phase coil Lb to C. A current is passed toward the phase coil Lc. Further, when the electrical angle θe is 270 ° to 360 °, a current is passed from the C-phase coil Lc toward the B-phase coil Lb. The A-phase current command value Iaref is set to “0”.
That is, when an energization abnormality occurs in the A-phase drive system, the B-phase current command value and the C-phase current command value are opposite to each other and have the same absolute value (normal two-phase). So that the sum of the current command values is zero).
Thus, the three-phase brushless motor 12 is driven in two phases by generating a rotating stator combined magnetic field and rotating the rotor.

FIG. 19 is a diagram showing the C-phase motor current and the motor torque at the time of the steering operation. The broken line indicates the motor current and the motor torque when the phase current command value Im (θe) is not corrected, and the solid line indicates the above. The motor current and the motor torque when correction is performed are shown.
Here, since the steering is increased, the motor torque direction and the motor rotation direction are both positive (left to right in FIG. 11), and the direction of the external load (steering reaction force) related to the motor is the negative direction (FIG. 11 from right to left).

  As shown by the broken line in FIG. 19, the C-phase current command value Icref when the phase current command value Im (θe) is not corrected remains the basic current command value Im (θe). In a region before reaching the upper limit (region before reaching the motor torque reduction region Atd), the basic motor current increases to a positive maximum current value in an arc shape that protrudes downward. In the motor torque reduction region Atd, the negative maximum value is maintained in the region before 90 °, the sign is inverted at 90 °, and the negative maximum value is maintained in the region after 90 °. When the motor torque reduction region Atd is exceeded, the motor current has an arc shape protruding upward, and the absolute value decreases from the maximum value.

  At this time, as shown by a broken line in FIG. 19B, the motor torque has a constant value in the angular region before and after the motor torque reduction region Atd. In the motor torque reduction region Atd where the phase current reaches the current upper limit, the motor torque decreases, and the motor torque becomes zero at 90 °. That is, the angular region before and after the motor torque reduction region Atd is a stable output angle region where a constant motor torque can be output, and the motor torque reduction region Atd is a current having a maximum current value Imax that can be output by the motor drive circuit 24. Becomes an unstable output angle region where a constant motor torque cannot be obtained.

Thus, there is an electrical angle θe (90 °, 270 °) at which the sign of the phase current command value Im (θe) is reversed and the motor torque is always zero when the three-phase brushless motor is driven and controlled at the time of abnormal power supply. To do. In the present embodiment, an angular region including a region (region Atg) before and after the region Atd that straddles the electrical angle θe is defined as an acceleration region Aa.
When the electrical angle θe does not reach the acceleration region Aa, the correction current command gain Gia is set to the stable region correction current gain (<1). Therefore, in each phase current command value generation unit 64 for two-phase control, the phase current A current command value Im is generated by reducing the command value Im (θe).
As described above, by correcting the motor current to decrease in the stable output angle region before reaching the acceleration region Aa, the motor torque is reduced in this region. This intentionally increases the steering torque.

Thereafter, when the electrical angle θe reaches the acceleration region Aa, the motor acceleration region determination unit 72 outputs an acceleration region determination flag Fa = 1. At this time, the first switchback flag Fr1 is reset to “0”, and the second switchback flag Fr2 is also reset to “0”.
For this reason, the correction current command gain calculation unit 74b of the correction current command gain generation unit 74 selects the cut correction current gain Gii (> 1), and this increase correction current gain Gii is used as the correction current command gain Gia for two-phase control. Output to each phase current command value generation unit 64.
At this time, the retry current command value gain generation unit 63 maintains the retry current command gain Gir at “0”.

For this reason, the multiplier 64a of each phase current command value generation unit 64 for two-phase control multiplies the basic current command gain Gif by the correction current command gain Gia, which is the increased correction current gain Gii, so that the current gain increases. Since the current command value is multiplied by the current command value Im (θe), the current command value Im (θe) ′ increases rapidly, and is limited to the maximum value by the phase current command value limiter 64f, and the rate limiter 64g. The rate of change is limited. Therefore, the current command value Im output from the rate limiter 64g increases to the maximum value relatively steeply as shown in FIG.
As described above, when the acceleration region Aa is reached, the motor current is increased and corrected, thereby increasing the motor torque and accelerating the three-phase brushless motor 12 in the positive direction. This increase correction is continued while the electrical angle θe exists in the acceleration region Aa.

In the acceleration region Aa, the current command value Im increases to the maximum current value Imax by increasing the correction current command gain Gia by the correction current command gain generation unit 74, whereby 90 ° is increased in the acceleration region Aa. The maximum positive value and the negative maximum value are maintained at the boundary. In other words, in the region Atg before and after the region Aa, the motor current increases compared to the case without correction indicated by the broken line, and the motor torque increases accordingly.
In this way, correction is made to increase the motor current in the stable output angle region Atg before and after reaching the current upper limit, that is, in the angle region where the motor torque can be increased and decreased freely.

  When the electrical angle θe exceeds the acceleration region Aa, the motor acceleration region determination unit 72 outputs an acceleration region determination flag Fa = 0. For this reason, the stable region correction current gain is selected as the correction current command value gain Gia by the correction current command gain generation unit 74, so that the basic current command value Im (θe) is determined by each phase current command value generation unit 64 for two-phase control. Correction to decrease again is performed, the current command value Im decreases, and the motor torque is reduced.

  As described above, when the steering is increased, the motor is accelerated in the forward direction in the region B before reaching the region A. Therefore, a constant motor as shown by a circle b to a circle c in the figure is generated by the inertia torque of the motor. It is possible to jump over the motor torque reduction region Atd where torque cannot be obtained. At this time, the phase current command value is reduced before the acceleration region Aa, and the steering torque is increased. Since the external load applied to the motor is vehicle load-steering force (steering torque), the external load applied to the motor can be reduced by increasing the steering torque. Therefore, it is possible to facilitate motor acceleration in the acceleration region Aa.

Further, in the acceleration region Aa, the motor is accelerated in the positive direction even in the region Atg after exceeding the region Atd. Therefore, after the region Atd is jumped once, the motor is caused by the external load applied to the motor generated in the negative direction. It is possible to prevent the motor torque from falling again into the motor torque reduction region Atd. Therefore, the motor can be appropriately rotated in the forward direction as indicated by the circle c → the circle d.
Thus, when an abnormality occurs in one of the three phases, the three-phase brushless motor 12 can be continuously driven using the remaining two phases. Further, at this time, it is possible to efficiently jump over the motor torque reduction region Atd where a constant motor torque cannot be obtained due to current limitation.

  However, in a steering state close to straight traveling, the steering torque T is small, and accordingly, the steering assist torque generated by the brushless motor 12 is also small, and the total torque value obtained by adding the steering torque T and the steering assist torque is an external load. There may be a case where the steering reaction force is substantially matched with (steering reaction force) and balanced. In this case, as described above, even when the correction current command gain Gia is increased and the brushless motor 12 is accelerated when entering the acceleration region Aa, the brushless motor 12 can obtain a large inertia torque. Therefore, the torque becomes insufficient and the motor torque reduction region Atd cannot be jumped over.

In this case, the current command value Im generated by each phase current command value generation unit 64 for two-phase control maintains the maximum value, but because the motor torque drop region cannot be jumped due to insufficient torque, The post-shift electric angle θes remains in the vicinity of the current value, and the rotational speed ωm of the brushless motor 12 decreases while the steering torque T increases, giving the driver a feeling of being caught.
In such a state, since it is a right turn state, the steering torque T increases in the positive direction, and the electric angle θes after the shift by failure phase is maintained smaller than the retry region electric angle θrt (= 180 ° + Δθo). As a result, the comparison output Cti (n) of the electrical angle comparison unit 81f becomes the logical value “1” and the previous comparison main force Cti (n−1) also has the logical value “1”. The coincidence output of the logical value “1” is supplied to the AND circuit 81i.

On the other hand, since the absolute value | T | of the steering torque is larger than the steering torque threshold value in the steering torque comparison unit 81d, the comparison output Ctc having the logical value “1” is output to the AND circuit 81i. Becomes a logical value “1” representing the continuation within the retry area electrical angle.
At this time, in the torque reduction region determination unit 73, the acceleration region determination flag Fa is set to “1”, and the current command value Im (θe) is the maximum value, so that it is output from the current command value comparison unit 73a. The comparison output Cti becomes a logical value “1”. Further, since the motor rotation speed ωm decreases and approaches substantially zero and decreases below the torque reduction region determination rotation speed threshold, the comparison output Ctv of the rotation speed comparison unit 73b also has a logical value “1”.

When this state continues beyond the torque reduction region determination time threshold, the determination unit 73c forcibly sets the second return flag Fr2 to “1” indicating the return state.
Therefore, in the correction current command gain generation unit 74, the acceleration region flag Fa is set to “1” and the second switchback flag Fr2 is set to “1”, so that the switchback correction current gain Girv is set to the correction current. The command gain Gia is output to each phase current command value generation unit 64 for two-phase control. The return correction current gain Girv at this time is a positive value smaller than “1” and close to zero because the current command value Im (θe) is the maximum value as shown in FIG.

Since this corrected current command gain Gia is supplied to each phase current command value generation unit 64 for two-phase control and is multiplied by the current command value Im (θe), the corrected current command value Im (θe) is shown in FIG. As shown by the arrow Y1, the value is reduced to a value close to zero.
For this reason, since the steering assist torque generated by the brushless motor 12 is substantially zero, the external force (steering reaction force) is larger than the sum of the steering torque T and the steering assist torque. When the brushless motor 12 is returned by an external force, the electrical angle θes decreases as shown by an arrow Y2 in FIG.

  When the electrical angle θe deviates from the acceleration region Aa and shifts to the stable output region, the motor acceleration region determination unit 72 resets the acceleration region determination flag Fa to “0”. Therefore, the torque reduction region determination unit 73 resets the acceleration region determination flag Fa to “0”, thereby resetting the second return flag Fr2 to “0”. Accordingly, since the acceleration region determination flag Fa is reset to “0” and the second switchback flag Fr2 is reset to “0” in the correction current command gain generation unit 74, the correction current command gain calculation unit 74b A stable region correction current gain is selected, and this stable region correction current gain is supplied as a correction current gain to each phase current command value generation unit 64 for two-phase control.

Therefore, as described above, the current command value Im increases as shown by the arrow Y3 in FIG. As the current command value Im increases, the motor torque generated in the brushless motor 13 increases, and the state shifts to the increased state again. As a result, when the electrical angle θes after the shift by failure phase increases and reaches the acceleration region Aa, the acceleration region determination flag Fa is set to “1” again, and the same acceleration control of the brushless motor 12 as described above is retried. It is executed as acceleration control.
At this time, since the retry count unit 81 maintains the electrical angle continuation state in the retry area, when the second switchback flag Fr2 changes from the switchback state to the switchover state, the retry count Nr is “ It is incremented from “0” to “1”.
If this retry acceleration control jumps over the motor torque reduction region Atd, then the two-phase control will be continued.

  However, if the motor torque reduction region Atd cannot be skipped even if the retry acceleration control is repeated a predetermined number of times, the number of retries Nr is sequentially increased. As described above, when the number of retries Nr increases, the acceleration region Aa is sequentially increased as shown in FIG. 19 by the retry return steering stable region correction unit 72c in the motor acceleration region determination unit 72 according to the number of retries. For this reason, the return position of the electrical angle θes due to the external force indicated by the arrow Y2 is gradually distant, and the electrical angle θes at which the current command value becomes the maximum value becomes small. Therefore, the acceleration control of the brushless motor 12 is performed longer, and the brushless motor 12 to increase the inertia torque to make it easier to jump over the motor torque reduction region Atd. If the motor torque decrease region Atd is jumped by the increase in the acceleration region Aa, the normal two-phase control state is restored.

  However, if the acceleration region Aa is not increased and the motor torque reduction region Atd cannot be skipped, the retry count Nr becomes a predetermined threshold and the second return flag Fr2 is set to “1” indicating the return state. When set, the retry gain output determination signal Srg output from the retry gain output determination unit 82a of the retry current gain generation unit 82 becomes the logical value “1”. Since the retry gain output determination signal Srg is supplied to the retry current command gain calculation unit 82b, the retry current command gain calculation unit 82b sets a retry current command gain Gir obtained by multiplying the retry current command reference gain Girb by the number of retries Nr. Will be increased.

  For this reason, the retry current command gain Gir is added to the basic current gain Gif by each phase current command value generation unit 64 for two-phase control, so that the current command value Im in the stable output region is shown by a one-dot chain line in FIG. So that it exceeds the basic current command value. For this reason, the motor torque output from the brushless motor 12 in the stable output region is also increased, torque acceleration control can be performed with a larger current command value of the brushless motor 12, and the motor inertia torque is increased. Thus, the motor torque reduction region Atd can be skipped.

  As described above, according to the embodiment, when the sum of the steering torque T and the motor torque generated by the brushless motor 12 is balanced with the external force (steering reaction force), the motor torque reduction region Atd cannot be jumped over. Occurs, the motor rotation speed ωm decreases while the current command value Im (θw) is maintained at the maximum value, and the driver feels caught. By setting Fr2 to “1” representing the switchback state, the correction current command gain Gia is set to the switchback correction current gain Girv, and the correction current command gain Gia is reduced to near zero. For this reason, when the current command value Im decreases to near zero, the brushless motor 12 is returned to the switchback direction by an external force, and a retry acceleration state in which the brushless motor 12 is accelerated again can be set.

If the motor torque reduction region Atd cannot be skipped even after repeating this retry acceleration state, the acceleration of the brushless motor 12 is accelerated by reducing the stable output region and increasing the acceleration region Aa in accordance with the increase in the number of retries Nr. The brushless motor 12 is subjected to retry acceleration control so as to increase the control time and generate a larger inertia torque.
If the motor torque reduction region Atd cannot be skipped even if the acceleration region Aa is increased, the retry current command gain Gir is finally increased in accordance with the number of retries Nr in the stable output region, and this is increased to the reference current command. By adding to the gain Gif, the current command value Im in the stable output region is increased, a larger motor torque is generated, and the motor torque decrease region Atd is skipped.

Thus, by performing retry acceleration control, it is possible to suppress the driver from being caught in a state where the sum of the steering torque T and the motor torque is in balance with the external force.
In the above embodiment, the hysteresis may be set in consideration of the sensor error of the steering torque sensor 3 when the sign is determined by the steering torque code determination unit 71a of the increase / decrease switching determination unit 71.

  Further, in the above embodiment, the torque reduction region determination unit 73 performs the second switching when the current command value exceeds the torque decrease region determination current threshold value and the motor rotation speed ωm becomes equal to or less than the torque decrease determination rotation speed threshold value. Although the case where the return flag Fr2 is forcibly set to “1” representing the return state has been described, the present invention is not limited to this, and the acceleration region determination flag Fa is “1” and the current command value is the torque. It is sufficient that the current command value Im can be reduced so as to be switched back to the external force when the reduction region determination current threshold is exceeded and the motor rotation speed ωm is equal to or less than the torque decrease determination rotation speed threshold. Can be applied.

In the above embodiment, the case where the maximum current value Imax is fixed at the current upper limit value has been described. However, the present invention is not limited to this, and the magnitude of the maximum current value Imax is changed according to the vehicle speed Vs. You may do it.
In the above-described embodiment, the case where the current command value is corrected to decrease by multiplying by a preset correction gain when the electrical angle is in the acceleration region has been described. However, the phase current command value Im (θe) The correction amount corresponding to the correction current command gain or the retry correction current command gain can be subtracted from or added to the correction current command gain.

  Moreover, although the said embodiment demonstrated the case where the interruption relay circuits RLY1-RLY3 were inserted between each phase coil La-Lc of the three-phase brushless motor 12 and the motor drive circuit 24, the interruption relay circuit Any one of RLY1 to RLY3 may be omitted. In this case, when a short circuit occurs in the field effect transistor of the upper arm or the lower arm in the motor drive circuit 24 in the drive system including the omitted interruption relay circuit, it is not possible to cope with it, and 3 in the abnormal state. The application range of the two-phase drive of the phase brushless motor is only reduced by two places, and does not become a big problem.

  Further, in each of the above embodiments, the case where the two-phase / three-phase conversion unit 33e is provided on the output side of the dq-axis current command value calculation unit 33d of the normal motor command value calculation unit 33 has been described. The two-phase / three-phase converter 33e can be omitted. In this case, instead of this, the motor current detection values Iad, Ibd, and Icd output from the motor current detection circuit 22 are supplied to the three-phase / two-phase converter, and the d-axis current Idd and the q-axis current Iqd of the rotation coordinates are supplied. The motor current control unit 36 subtracts the d-axis current Idd and the q-axis current Iqd from the d-axis current command value Idref and the q-axis current command value Iqref to calculate current deviations ΔId and ΔIq, which are PI controlled. A PI control process is performed in the unit 62 to calculate a d-axis command voltage Vd and a q-axis command voltage Vq, and these are converted into three-phase command pressures Va, Vb and Vc by a 2-phase / 3-phase conversion unit, and an FET gate The entire control arithmetic unit 23 may be configured as a vector control system so as to be supplied to the drive circuit 25.

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Steering torque sensor, 8 ... Steering gear, 10 ... Steering assist mechanism, 12 ... Three-phase brushless motor, 13 ... Rotor rotation angle detection circuit, 20 ... Steering assist control device, 21 DESCRIPTION OF SYMBOLS ... Vehicle speed sensor, 22 ... Motor current detection circuit, 23 ... Control arithmetic unit, 24 ... Motor drive circuit, 25 ... FET gate drive circuit, 26 ... Relay circuit for interruption, 27 ... Abnormality detection circuit, 31 ... Steering auxiliary current command value Arithmetic unit 32... Angle information calculating unit 32 a Electric angle conversion unit 32 b Differentiating circuit 33 Normal motor command value calculation unit 33 a d-axis current command value calculation unit 33 b dq-axis voltage calculation , 33c: q-axis current command value calculation unit, 33e: 2-phase / 3-phase conversion unit, 34: abnormal motor command value calculation unit, 35: command value selection unit, 36: motor current control , 61 ... Basic current command gain generation unit, 62 ... Correction current command gain generation unit, 63 ... Retry current command gain generation unit, 64 ... Each phase current command value generation unit for two-phase control, 66 ... Angle offset processing for each fault phase , 67 ... Back electromotive voltage characteristic gain calculation part, 71 ..., Increase / return switching determination part, 72 ... Motor acceleration area determination part, 73 ... Torque reduction area determination part, 74 ... Correction current command gain generation part, 81 ... Retry Count unit, 82d retry current command gain generation unit, 91a to 91c ... selection switch, 92 ... selection control unit, 101a to 101c ... subtractor, 102 ... PI control unit

Claims (6)

A three-phase electric motor in which each phase coil for applying a steering assist force to the steering system is star-connected, a steering torque detecting means for detecting a steering torque transmitted to the steering system, and an energization abnormality of each phase coil. A coil energization abnormality detecting means for detecting, and an abnormal motor command for calculating an abnormal time phase current command value for the remaining two-phase coils when the energization abnormality of the one-phase coil is detected by the coil energization abnormality detecting means. An electric power steering apparatus comprising: value calculating means; and motor control means for driving and controlling the three-phase electric motor based on the abnormal time phase current command value,
A current command value correction means for reducing the abnormal time phase current command value when balancing the sum of the steering torque and the steering assist torque generated by the three-phase electric motor with an external force;
The current command value correcting means is a predetermined angle region in which the electrical angle of the three-phase electric motor straddles a minimum torque electrical angle at which the sign of the abnormal time phase current command value calculated by the abnormal motor command value calculating means is reversed. Acceleration region determination means for determining whether or not the acceleration region is within the acceleration region;
When the acceleration region determining means determines that the electrical angle is within the acceleration region, the three-phase electric motor is corrected by increasing the abnormal time phase current command value calculated by the abnormal motor command value calculating means. Motor rotation acceleration means for accelerating the rotation of the motor in the steering direction;
Whether or not the electrical angle continues across the minimum torque electrical angle and within a retry region wider than the acceleration region when the rotation of the three-phase electric motor by the motor rotation acceleration means is accelerated in the steering direction. Retry area determination means for determining whether or not
When the retry region determining means determines that the electrical angle is in the retry region, the acceleration region is increased and the rotation of the three-phase electric motor is reaccelerated in the steering direction. An electric power steering apparatus comprising a retry acceleration means.   The retry acceleration means reduces the abnormal phase current command value so that the electrical angle changes due to an external force when the electrical angle is in an acceleration region and the sum of steering torque and steering assist torque is balanced with an external force. When the electric angle reaches the boundary position of the acceleration region, the abnormal time phase current command value is increased from the basic current command value to re-accelerate the rotation of the three-phase electric motor in the steering direction. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is configured. Motor rotation speed detecting means for detecting the motor rotation speed of the three-phase electric motor;
The retry acceleration means determines whether the steering direction is the increase direction or the return direction based on the steering torque and the motor rotation speed, and sets the first return flag by setting the first return flag. Based on the determination result of the determination unit and the acceleration region determination means, the abnormal time phase current command value, the switchback flag, and the motor rotation speed, it is determined whether or not it is a torque decrease region. The abnormal time phase current command value based on the determination result of the acceleration region determining means and the second return flag, and a torque reduction region determination unit for setting a second return flag for instructing return The electric power steering apparatus according to claim 1, further comprising: a correction current command gain generation unit that generates a correction current command gain that reduces the electric angle by an external force.   The retry area determination means counts the number of retries when the electrical angle after the rotation of the three-phase electric motor is reaccelerated in the steering direction by the retry acceleration means continues in the retry area. The electric power steering apparatus according to any one of claims 1 to 3, further comprising a retry counting unit.   5. The electric power steering apparatus according to claim 4, wherein the retry area determination unit is configured to increase the retry area based on the electric angle and the direction of the steering torque. 6. The retry acceleration means is configured to increase the abnormal phase current command value outside the acceleration region according to the number of retries when the number of retries of the retry counter exceeds a threshold value. The electric power steering apparatus according to claim 4 or 5.

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