JP2020142740A - Motor energization control method - Google Patents

Abstract

To provide a motor energization control method by which motor drive is continued and a dead point can be overcome even if phase fall occurs.SOLUTION: When phase fall occurs, there is an electric angle on a near side by a prescribed angle with respect to a torque dead point at which an output torque becomes zero, and when a rotation speed of an electric motor 15 and a steering torque satisfy prescribed condition, the electric angle is returned to a first electric angle θ4 to flow a phase current in a reverse direction, and the electric motor 15 is reversely rotated. Then, the phase current is flown in a forward direction until reaching a second electric angle θ5 to normally rotate the electric motor 15, and a sufficient angular speed is maintained, thereby overcoming the torque dead point.SELECTED DRAWING: Figure 4

Description

The present invention relates to, for example, a motor energization control method used in an electric power steering device or the like.

In recent years, when an abnormality occurs in one phase of a three-phase electric motor in an electric power steering device, there is an increasing demand for continuously driving (assisting) the electric motor with the remaining two normal phases without stopping the motor control. In such a phase failure, the motor torque decreases in the vicinity of the electric angle corresponding to the faulty phase, and a region where the steering wheel cannot be cut occurs. Therefore, it has been a problem from the past to improve the steering feeling by jumping over the motor torque drop region at the time of phase failure.

For example, Patent Document 1 reduces the phase current command value when the sum of the steering torque and the steering auxiliary torque generated by the electric motor is balanced with the external force and the motor torque drop region cannot be overcome when the motor is driven by two phases. Disclosed is an electric power steering device that accelerates the motor by increasing the command current value after returning the electric angle by an external force (steering reaction force) to overcome the region where the motor torque decreases.

Japanese Patent No. 5610048

In the electric power steering device of Patent Document 1, the current command value is lowered when the sum of the steering torque and the steering auxiliary torque is balanced with the external force, and the electric angle is set to the acceleration region including the motor torque reduction region and the motor torque generation region. At one point, the current command value is increasing. Therefore, since the motor assist is returned from the lost state, there is a problem that the feeling of the steering being caught on the driver is increased.

As another technology, a configuration has been proposed in which the current command value is increased and corrected when the electric angle is in the acceleration region to accelerate the rotation of the motor to overcome the region where the motor torque decreases, but for example, when parking, the vehicle speed At low speeds, there is a problem that it is difficult to overcome the region where the motor torque drops only by accelerating.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is a motor energization control method capable of driving and controlling an electric motor to continue smooth assist even if a failure occurs in one phase of a plurality of phases. Is to provide.

The following configuration is provided as a means for achieving the above object and solving the above-mentioned problem. That is, the exemplary first invention of the present application is a motor energization control method used in an electric power steering device that assists the steering of a driver such as a vehicle by a multi-phase electric motor having three or more phases. A detection step for detecting the presence or absence of a failure of any one of the phases, and a phase current calculation step for calculating the phase current for the remaining phases excluding the failed phase when the failure is detected in the detection step. When the failure is detected in the detection step, the electric angle of the electric motor is on the front side of a predetermined angle from the electric angle at which the output torque of the electric motor becomes zero, and at least the rotation speed of the electric motor. In the determination step of determining whether or not the steering torque satisfies the predetermined condition, and in the determination step, the electric angle of the electric motor is on the front side of the predetermined angle, and the rotation speed and steering torque of the electric motor are determined. When it is determined that the predetermined condition is satisfied, the electric angle is returned in the opposite direction until the output torque of the electric motor reaches the first target electric angle that becomes the predetermined torque, and the phase current calculation step for the electric motor. The first control step in which the phase current calculated in the above is passed in the direction opposite to the steering direction, and the electric motor after the electric angle of the electric motor reaches the first target electric angle until it reaches the second target electric angle. It is characterized by including a second control step of flowing the phase current calculated in the phase current calculation step to the motor in the steering direction.

An exemplary second invention of the present application is an electric power steering control device that assists the steering of a driver of a vehicle or the like by a multi-phase electric motor having three or more phases, and the loss of any one of the polyphases. It includes a detection unit that detects the presence or absence of a depression, and a control unit that drives and controls the electric motor by the motor energization control method according to the first exemplary invention when the detection unit detects the failure. It is characterized by that.

The third exemplary invention of the present application is an electric power steering system, characterized in that the electric power steering control device according to the second exemplary invention is provided.

According to the present invention, the arrival of a torque dead point at which the rotation of the electric motor stops at the time of phase loss is predicted, and acceleration control is performed before the rotation stops to overcome the torque dead point and smooth the steering direction. Assist can be continued.

FIG. 1 is a diagram showing a schematic configuration of an electric power steering device (system) using the motor energization control method according to the embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a motor control device. FIG. 3 is a diagram showing a phase current with respect to an electric angle during two-phase energization control and an output torque corresponding to the phase current. FIG. 4 is a diagram showing the relationship between the electric angle of the motor, the output torque, and the rotation speed of the motor during two-phase energization control in the motor control device according to the embodiment. FIG. 5 is a flowchart showing the procedure of overcoming control in chronological order. FIG. 6 is a diagram schematically showing an example of a temporal change in the electric angle in overcoming control.

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic configuration of an electric power steering device (system) using the motor energization control method according to the embodiment of the present invention. The electric power steering device 1 of FIG. 1 includes a motor control device 10 as an electronic control unit (ECU), a steering handle 2 which is a steering member, a rotating shaft 3 connected to the steering handle 2, and a pinion gear 6. A rack shaft 7 and the like are provided.

The rotating shaft 3 meshes with a pinion gear 6 provided at its tip. The pinion gear 6 converts the rotary motion of the rotary shaft 3 into a linear motion of the rack shaft 7, and a pair of wheels 5a, 5b provided at both ends of the rack shaft 7 at an angle corresponding to the displacement amount of the rack shaft 7. Is steered.

The rotating shaft 3 is provided with a torque sensor 9 that detects the steering torque when the steering handle 2 is operated, and the detected steering torque is sent to the motor control device 10. The motor control device 10 generates a motor drive signal based on signals such as steering torque acquired from the torque sensor 9 and vehicle speed from a vehicle speed sensor (not shown), and outputs the signal to the electric motor 15.

An auxiliary torque for assisting the steering of the steering handle 2 is output from the electric motor 15 to which the motor drive signal is input, and the auxiliary torque is transmitted to the rotating shaft 3 via the reduction gear 4. As a result, the torque generated by the electric motor 15 assists the rotation of the rotating shaft 3, thereby assisting the driver in operating the steering wheel.

Next, the configuration and control operation of the motor control device according to this embodiment will be described.

<Configuration of motor control device>
FIG. 2 is a block diagram showing the configuration of the motor control device 10 of FIG. In FIG. 2, the motor control device 10 targets the electric motor 15 as a drive target. The electric motor 15 is, for example, a three-phase (U, V, W) brushless motor.

The motor control device 10 is a central control unit (CPU) 11 that controls the entire device, an inverter control unit 13 that receives a control signal from the CPU 11 and generates a motor drive signal (PWM signal), and each motor coil of the electric motor 15. Is provided with a motor drive unit 14 or the like as an inverter circuit (INV) that supplies a predetermined drive current.

The inverter control unit 13 is also called a pre-driver unit (PrDr) that functions as an FET drive circuit. The semiconductor switching elements (FET1 to FET6) constituting the motor drive unit 14 correspond to each phase of the electric motor 15. Specifically, FETs 1 and 2 correspond to the U phase, FETs 3 and 4 correspond to the V phase, and FETs 5 and 6 correspond to the W phase.

FETs 1, 3 and 5 are switching elements for the upper arms (also referred to as high side (HiSide)) of the U phase, V phase and W phase, respectively, and the FETs 2, 4 and 6 are the U phase, V phase and W phase, respectively. It is a switching element of the lower arm (also referred to as a low side). The switching element (FET) is also called a power element, and for example, a switching element such as a MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor) is used.

The drain terminals of FETs 1, 3 and 5 constituting the bridge circuit are connected to the power supply side, and the source terminals are connected to the drain terminals of FETs 2, 4 and 6. Further, the source terminals of FETs 2, 4 and 6 are connected to the ground (GND) side.

The CPU 11 of the motor control device 10 has a normal energization control unit 21 that generates a motor drive signal (PWM signal) corresponding to a normal drive (three-phase energization drive) without a failure such as a phase loss, and a phase loss or the like. The two-phase energization control unit 31 is provided to generate a motor drive signal (PWM signal) corresponding to the failure of the above.

The normal energization control unit 21 has a target phase current calculation unit 23 that calculates a three-phase target phase current in order to perform normal motor control without phase failure. On the other hand, since the two-phase energization control unit 31 performs energization control by the other two phases in the event of a one-phase failure, the overcoming control unit 33, the 180 ° energization electric angle calculation unit 35, and the motor control in the event of a phase failure It has a two-phase energization target phase current calculation unit 37 for calculating a two-phase target phase current.

A current detection unit (current sensor) 17 provided corresponding to each phase is arranged in the motor drive unit 14. The current detection unit 17 detects the direct current flowing through the shunt resistors R1 to R2 for detecting the motor drive current by using an amplifier circuit such as an operational amplifier. The electric motor 15 is equipped with a rotation sensor (electric angle sensor) 19 that detects the rotation position of the rotor. Further, a signal detected by a speed sensor (not shown) for detecting the traveling speed of the vehicle is input to the CPU 11.

The current detection value of the current detection unit 17, the motor rotation angle of the rotation sensor 19, and the like are converted into digital data and output to the failure phase determination unit 32 in the two-phase energization control unit 31. The failure phase determination unit 32 determines the presence or absence of a phase failure in the motor control device 10 based on these input data.

The voltage command value of each phase supplied to the inverter control unit 13 or the pulse width modulation signal of each phase supplied to the motor drive unit 14 is compared with the motor voltage of each phase, and the comparison result is compared. A configuration may be provided for transmission to the failure phase determination unit 32. As a result, the failure phase determination unit 32 can detect non-conduction and short-circuit abnormality of each phase as phase failure.

A switching signal corresponding to the presence or absence of a failure such as a phase failure is input to the switching unit 12 from the failure phase determination unit 32. The switching unit 12 switches between the motor drive signal during normal driving and the motor drive signal during two-phase energization according to the switching signal, and supplies the switched motor drive signal to the inverter control unit 13.

<Operation of motor control device>
During normal control, the motor control device 10 controls the electric motor 15 by a three-phase alternating current composed of U-phase, V-phase, and W-phase currents whose phases differ by 120 ° from each other. If one phase is lost due to a failure of the motor drive unit 14 that constitutes the inverter circuit, the motor coil of the electric motor 15, or the disconnection of the power line (motor line) connected to the motor coil, etc., two phases of three-phase AC If the minute is passed through the electric motor 15 as it is, the output torque will be reduced except for a part.

Therefore, the motor control device according to the present embodiment switches to the control by the phase current defined by the following equation (1) when one phase fails. That is, two-phase energization control is performed to maintain the output torque within a range in which the currents of the two phases of the phase currents I _{u, v, and w} excluding the failing phase do not exceed the limit value.

I _{u, v, w} = [−√3 × (target torque × torque constant)] / √2 × sin (θ + φ)
… (1)

Here, θ is an electric angle, φ is a constant that is switched according to the collapsed phase, and U phase = 30 °, V phase = 150 °, and W phase = 270 °.

At the time of two-phase energization, the overcoming control unit 33 of the two-phase energization control unit 31 overwrites the target torque input to the motor control device 10. Then, the two-phase energization target phase current calculation unit 37 calculates the target phase current corresponding to the two-phase energization, excluding the rotation angle with respect to the failed phase.

FIG. 3A shows a phase current with respect to an electric angle during two-phase energization control, and FIG. 3B shows an output torque corresponding to the phase current of FIG. 3A. In each case, the case where the failed phase is the W phase is illustrated.

In the calculation of the target phase current corresponding to the two-phase energization, a known mathematical method is used, and the predetermined rotation angle corresponding to the collapsed phase is set as an asymptote by the equation (1), as shown in FIG. 3A. As shown, the target phase current that changes in the form of a secant curve (reciprocal of cos θ) or cosecant curve (reciprocal of sin θ) is calculated.

There is an upper limit to the current that can be applied to each coil of the electric motor 15. Therefore, the phase current is limited by cutting the peak in the region indicated by reference numerals A to D in FIG. 3A so that the current does not exceed the rated current of the electric motor, switching element, or the like. Further, in the two-phase energization control, most of the current becomes invalid when θ + ψ is around 0 ° or 180 °. Therefore, the current is set to 0 in the region indicated by the reference numerals a to c in FIG. 3A. Here, the weakening magnetic flux control is not performed.

Therefore, when a failure occurs in one phase, even if an attempt is made to pass a current through the electric motor 15, the output torque of the electric motor 15 is not generated and the motor does not rotate (reference numerals DP1 to DP3 in FIG. 3B). (Shown) occurs in units of 180 ° electric angle. These points are called torque dead points (hereinafter, also simply referred to as dead points), and mean points where the steering wheel cannot be turned.

<Two-phase energization control>
FIG. 4 shows the relationship between the electric angle of the motor, the output torque, and the rotation speed of the motor during two-phase energization control (also referred to as overcoming control as appropriate) in the motor control device according to the present embodiment. Further, FIG. 5 is a flowchart showing the procedure of overcoming control in chronological order.

The CPU 11 of the motor control device 10 performs control according to a phase failure described later according to a program stored in a memory (not shown) such as a ROM (read-only memory).

First, the failure phase determination unit 32 of the CPU 11 determines the motor control device 10 based on the current detection result by the current detection unit provided for each phase as described above, the motor rotation angle, and the like in step S11 of FIG. Judge whether there is a failure such as a failure in the above. If there is no phase loss or the like, normal control (normal energization control unit 21 performs three-phase energization drive) is performed in step S40.

If there is a phase failure or the like, the dead point differs depending on the phase that has failed. Therefore, in step S13, the failure phase determination unit 32 determines which of the U phase, V phase, and W phase is the failure phase. While making a judgment, a switching signal is output to the switching unit 12. As a result, the motor control device 10 can shift from the motor drive control during normal drive to the two-phase energization control corresponding to the phase failure.

The 180 ° energization electric angle calculation unit 35 adjusts the electric angle used for overcoming control. As described above, since the dead point is generated every 180 °, the variation of the dead point position for each failure phase is eliminated by offsetting the electric angle and limiting it within the range of 180 °. Specifically, as shown in FIG. 4, the electric angle at which the torque output is maximized is set to 0 °, and the electric angle at which the torque output is zero (dead point) is set to ± 90 °.

As shown by reference numeral 41 in FIGS. 3B and 4, the output torque of the electric motor 15 at the time of one-phase failure gradually decreases as it approaches the dead point DP. Therefore, in step S15 of FIG. 5, the overcoming control unit 33 is based on, for example, the rotation speed, steering torque, and electric angle of the electric motor 15 in the region where the output torque decreases as shown by reference numeral 43 in FIG. , Predict whether the current driver's steering force can exceed the dead point DP or whether it is difficult to overcome the dead point DP.

Specifically, in the above-mentioned region where the output torque decreases, the steering torque is, for example, assuming that the rotation speed of the electric motor 15 is smaller than, for example, 2 rotations per second, and the driver turns the handle to some extent. Overcoming the dead point when the electric angle is smaller than 2 Nm and the electric angle is in front of the electric angle (θ _{3 in} FIG. 4) at which the output torque of the electric motor 15 becomes zero by a predetermined angle (for example, 45 °). Judges as difficult.

The above-mentioned determination threshold value is a parameter that can be calibrated in order to alleviate the vibration that occurs when two-phase energization is applied.

If it is determined in step S15 that the current driver's steering force can overcome the dead point, in step S50, the electric motor 15 is accelerated and controlled to assist the driver in the steering direction, so that the dead point can be easily overcome. To do.

On the other hand, when it is predicted that it will be difficult to overcome the dead point, the electric motor 15 is once rotated in the direction opposite to the steering direction of the driver, and overcoming control is performed to intentionally obtain the steering force of the driver. ..

That is, in step S17, the two-phase energization target phase current calculation unit 37 obtains the two-phase energization electric angle calculated (adjusted) by the 180 ° energization electric angle calculation unit 35 and the assist torque from the overcoming control unit 33. Based on this, the two-phase target phase current for controlling the motor at the time of phase failure is calculated.

In step S19, as shown by the locus P1-P2 (broken line portion) in FIG. 4, the electric angle is returned in the reverse direction until the target electric angle (θ _{4 in} FIG. ₄ ) at which the output torque of the electric motor 15 is maximized is reached. At the same time, the phase current calculated in step S17 is passed through the electric motor 15 in the direction opposite to the steering direction. The locus P1'-P2' (dashed line portion) in FIG. 4 indicates the rotation speed of the electric motor rotating in the opposite direction.

Returning the electric angle in the opposite direction as described above corresponds to the control for giving momentum (running) to the acceleration control described later. Therefore, the target electric angle (θ ₄ ) when the electric angle is returned in the opposite direction in step S19 can be adjusted according to the torque or the like output in the acceleration control (in other words, the approach distance is changed). ..

After starting the above overcoming control, in step S21, when it is determined that a steering torque in the reverse direction exceeding a predetermined value (for example, 2 Nm) is generated, or when it is determined that the vehicle speed is low (for example, less than 3 km / h). Assuming that the dead point overcoming control is unnecessary, the process proceeds to step S35 to interrupt the overcoming control. Then, the process returns to the normal two-phase control (step S33). By interrupting the overcoming control in this way, it is possible to avoid the hindrance of steering and the rattling of the steering due to the overcoming control.

When it is determined in step S23 that the electric angle has reached the target return angle (θ ₄ ) without generating the steering torque in the reverse direction as described above after the start of the overcoming control, the current is switched in step S25. That is, the phase current calculated in step S17 is passed through the electric motor 15 in the steering direction (forward direction). This accelerates the electric motor 15.

If it is determined in step S27 that the steering torque is less than a predetermined value (for example, 1 Nm) after accelerating the electric motor, it is assumed that the driver has not turned the steering wheel and it is not necessary to get over it, and the process proceeds to step S35 to get over. The control is interrupted and the normal two-phase control is returned (step S33).

On the other hand, if it is determined in step S27 that the steering torque is equal to or greater than a predetermined value, it is determined in step S29 whether or not the overcoming is completed. Here, after reaching the above-mentioned target electric angle (θ ₄ ), the next target electric angle θ ₅ (for example, an electric angle within the range of 30 ° in the positive direction from the angle θ _{3 at} which the torque becomes zero) Determine if it has been reached. In the example shown in FIG. 4, it is determined that the overcoming is completed when the electric angle reaches + 120 °.

Since the target electric angle (θ ₅ ) is a point for determining torque recovery, for example, in the case of an electric power steering device using the motor control device 10, depending on the vehicle or the like on which the electric power steering device is mounted. Make it adjustable.

As described above, the change in the output torque of the electric motor 15 after switching the current direction is shown by the trajectories P2-P3 (two-dot chain line portion) in FIG. Further, the change in the motor rotation speed at that time is shown by the locus P2'-P3' (two-dot chain line portion) in FIG.

When it is confirmed in step S29 that the overcoming control is completed, the motor control device 10 has overcome the dead point DP by combining the steering force of the driver and the output torque of the electric motor 15. Therefore, after that, the process returns to the normal two-phase control (step S33).

On the other hand, if the overcoming control is not completed, it is determined in step S31 whether or not the overcoming has failed. For example, if the electric angle does not reach θ ₅ even after a lapse of a predetermined time after the phase current is passed in the opposite direction in step S19 described above, it is determined that the overcoming has failed.

The above predetermined time is, for example, a time smaller than 500 msec. Therefore, if the time until the overcoming ends normally is longer than the set time, it is considered that the overcoming cannot be performed, the process is returned to step S17, and the dead point overcoming control (acceleration control) is executed again.

FIG. 6 schematically shows an example of the temporal change of the electric angle in the above-mentioned overcoming control (acceleration control). As shown in FIG. 6, when the dead point is approached when the control state is in the normal control state 61, the reverse rotation control of the motor is started at the point P1 (corresponding to P1 in FIG. 4) in front of the dead point, and the reverse rotation control is performed. It shifts to the state 62.

When the point P2 (corresponding to P2 in FIG. 4) is reached in the reverse rotation control state 62, the forward rotation control of the motor is started to shift to the normal rotation control state 63. Then, when the point P3 (corresponding to P3 in FIG. 4) is reached in the normal rotation control state 63, it returns to the normal control state 64, assuming that the overcoming control (acceleration control) is completed.

On the other hand, when overcoming control (acceleration control) is not performed, the motor does not shift to reverse control at point P1. As a result, as shown by the dotted line in FIG. 6, a dead point DP at which torque is not generated is reached, the rotation speed of the electric motor decreases, and when the reaction force is large, the electric motor stops.

As described above, in a motor control device that controls a multi-phase electric motor, when a failure occurs in any one of the multiple phases, the electric angle becomes zero and the output torque becomes zero (torque dead). If it is on the front side of a predetermined angle from the point) and the rotation speed of the electric motor and the steering torque satisfy the predetermined conditions, the electric angle is returned and the output torque becomes a predetermined value (for example, the maximum output torque). A phase current is passed in the opposite direction up to the electric angle of 1, and the electric motor is rotated in the reverse direction. Subsequently, a phase current is passed in the forward direction until the second electric angle is reached to rotate the electric motor in the normal direction, so that a sufficient angular velocity is maintained at the torque dead point.

By doing so, it becomes easy to judge whether or not the dead point can be overcome with the steering force of the current driver, and the steering direction of the steering and the rotation direction of the electric motor match at the time of one-phase failure. The rotation of the electric motor can be stopped at each stage, that is, the arrival of a torque dead point can be predicted, and the rotation of the electric motor can be accelerated without being stopped.

As a result, when the assist is continued by the degenerate motor drive by the phase excluding the collapsed phase, for example, the electric motor is continued to be driven at the maximum output in the steering direction of the driver, and the steering force of the driver and the output torque of the electric motor are reduced. At the same time, it is possible to overcome the dead point and provide smooth steering assist.

On the other hand, if the circuits of the electric motor and its control device are completely made redundant by the hardware configuration, it is possible to realize a system with a low failure rate in which the entire system does not stop due to some failures, but such a system is costly. It will be high. From this, it is possible to provide a low-cost motor control device by making the failure control redundant by software as in the motor control device according to the above-described embodiment.

The present invention is not limited to the above-described embodiment, and various modifications are possible. The mode of interrupting the overcoming control is not limited to the interruption under the above-mentioned conditions. For example, it is determined in step S31 of FIG. 5 that the overcoming of the dead point has failed, and the process returns to step S17 to perform overcoming control again. A limit (for example, 3 times) may be provided on the number of times (acceleration control) is executed.

By limiting the number of retries for overcoming control (acceleration control) in this way, it is possible to quickly determine that the dead point cannot be overcome, and noise and vibration are generated due to torque fluctuations due to the inability to overcome. Etc. can be avoided.

Further, in the electric power steering control device that assists the steering of the driver of the vehicle or the like by a multi-phase electric motor of three or more phases, or in the electric power steering system provided with the electric power steering control device, the above-described embodiment By driving and controlling the electric motor by the motor energization control method, for example, even if a failure occurs in one of the three phases, the assist can be continued by controlling the dead point overcoming by the remaining two phases.

Further, in the above-mentioned electric power steering control device or electric power steering system, a visible display means for notifying the driver or the like that overcoming control (acceleration control) is being executed at the time of steering may be provided. ..

1 Electric power steering device (system)
2 Steering handle 3 Rotating shaft 4 Reduction gear 6 Pinion gear 7 Rack shaft 9 Torque sensor 10 Motor control device 11 Central control unit (CPU)
12 Switching unit 13 Inverter control unit 14 Motor drive unit 15 Electric motor 17 Current detection unit (current sensor)
19 Rotation sensor (electric angle sensor)
21 Normal energization control unit 23 Target phase current calculation unit 31 Two-phase energization control unit 32 Lost phase determination unit 33 Overcoming control unit 37 Two-phase energization target phase current calculation unit R1 to R2 Shunt resistance

Claims (10)

A motor energization control method used in an electric power steering device that assists the steering of a driver such as a vehicle by using a three-phase or more multi-phase electric motor.
A detection step for detecting the presence or absence of failure of any one of the polyphases, and
When the failure is detected in the detection step, a phase current calculation step of calculating the phase current for the remaining phases excluding the failure phase, and a phase current calculation step.
When the failure is detected in the detection step, the electric angle of the electric motor is on the front side of a predetermined angle from the electric angle at which the output torque of the electric motor becomes zero, and at least the rotation speed and steering of the electric motor. A determination process for determining whether or not the torque satisfies a predetermined condition, and
In the determination step, when it is determined that the electric angle of the electric motor is on the front side of the predetermined angle and the rotation speed and steering torque of the electric motor satisfy the predetermined conditions, the output torque of the electric motor is determined. The first control in which the electric angle is returned in the opposite direction until the first target electric angle at which the predetermined torque is reached is reached, and the phase current calculated in the phase current calculation step is passed to the electric motor in the direction opposite to the steering direction. Process and
After the electric angle of the electric motor reaches the first target electric angle, the phase current calculated in the phase current calculation step is passed through the electric motor in the steering direction until it reaches the second target electric angle. 2 control steps and
A motor energization control method characterized by comprising. The motor energization control method according to claim 1, wherein the predetermined torque is the maximum output torque of the electric motor. The first control step is characterized in that the phase current flowing in the direction opposite to the steering direction and the phase current flowing in the steering direction in the second control step are the rated maximum currents of the electric motor. The motor energization control method according to. The first aspect of the present invention is characterized in that the step of driving the electric motor by reducing the phase current flowing in the steering direction after the electric angle of the electric motor reaches the second target electric angle is further provided. Motor energization control method. The first control step is characterized in that the first control step is interrupted when the steering torque in the reverse direction is determined to be equal to or higher than a predetermined value or when the vehicle speed is determined to be less than a predetermined value. The motor energization control method according to 1. When the second target electric angle has not been reached after a lapse of a predetermined time from the start of the first control step, the first control step and the second control step are executed again. The motor energization control method according to claim 1. The motor according to claim 6, wherein the predetermined time is shorter than 500 msec, and the second target electric angle is an angle within a range of 30 ° in the plus direction from the electric angle at which the output torque becomes zero. Energization control method. The sixth aspect of claim 6, wherein when the number of executions of the first control step and the second control step exceeds a predetermined value, the first control step and the second control step are interrupted. Motor energization control method. An electric power steering control device that assists the steering of a driver of a vehicle or the like by a multi-phase electric motor having three or more phases.
A detection unit that detects the presence or absence of failure of any one of the polyphases,
When the failure is detected by the detection unit, the control unit that drives and controls the electric motor by the motor energization control method according to any one of claims 1 to 8.
An electric power steering control device characterized by being equipped with. An electric power steering system comprising the electric power steering control device according to claim 9.

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