JP5321043B2 - Vehicle steering control device and vehicle steering control method - Google Patents

Description

  The present invention relates to a vehicle steering control device and a vehicle steering control method in which a steering unit and a steering unit can be mechanically connected and disconnected via a clutch.

Conventionally, there is a steering control device that performs steer-by-wire control (SBW control) in which a steering mechanism that is mechanically separated from a handle is driven by a steering motor. In this steering control device, switching from SBW control to steering assist control (EPS control) is generally performed during a steering reaction force system failure.
When an abnormality occurs in the torque sensor, the electric power steering apparatus that performs EPS control stops the EPS control and shifts to manual steering (see, for example, Patent Document 1). In this electric power steering apparatus, the torque sensor includes a main potentiometer and a sub potentiometer. Then, the main value and the sub value are compared, and when the difference between the two becomes a predetermined value or more, it is determined that the torque sensor is abnormal.
JP-A-3-121974

However, the technique described in Patent Document 1 only determines whether or not an abnormality has occurred in the torque sensor. That is, it cannot be determined whether an abnormality has occurred in the main value or the sub value.
Therefore, if an abnormality occurs in the main value or sub value of the torque sensor during the SBW control and then a failure occurs in the steering reaction force system, the SBW control cannot be shifted to the EPS control. Therefore, in this case, the process shifts to manual steering. As a result, a large change in steering force occurs.
Accordingly, an object of the present invention is to provide a vehicle steering control device and a vehicle steering control method capable of ensuring a transition from SBW control to EPS control during a steering reaction force system failure.

In order to solve the above-described problems, a vehicle steering control device according to the present invention includes a steering reaction force actuator and a steering actuator in a state where the clutch is released and the steering unit and the steering unit are mechanically separated. Steering control is performed to control the drive. During this steering control, the detected first steering torque, the second steering torque, and the estimated estimated steering torque are compared to determine a steering torque value in which an abnormality has occurred among the three values. Then, when it is determined that only the estimated steering torque shows an abnormal value and the transition condition from the steering control to the steering assist control is satisfied, the clutch is engaged and the steering control is switched to the steering assist control. At this time, in the steering assist control, control is performed based on the determined normal steering torque value.

  With the vehicle steering control device according to the present invention, it is possible to determine a steering torque value in which an abnormality has occurred during steering control. Therefore, if the transition condition to the steering assist control is satisfied when the steering control is performed in a state where the steering torque value is abnormal, the transition to the steering assist control is performed by using the normal steering torque value. Can do. As a result, transition from steering control to manual steering can be prevented. Therefore, it is possible to prevent a large change in steering force.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<< First Embodiment >>
"Constitution"
FIG. 1 is an overall configuration diagram of a steer-by-wire system to which a vehicle steering control device according to the present invention is applied.
As shown in FIG. 1, the steering wheel 1 operated by the driver is mechanically separated from the steering mechanism 10 that steers the left and right front wheels 11R and 11L. The steering shaft 2 is connected to the steering wheel 1. The steering shaft 2 is provided with a steering angle sensor 3, a steering torque sensor 4, and a reaction force motor 5.

The steering torque sensor 4 detects the steering torque transmitted from the steering wheel 1 to the input shaft 2a. The steering torque sensor 4 detects the steering torque by detecting a torsional angular displacement of a torsion bar (not shown) interposed between the input shaft 2a and the output shaft 2b with a potentiometer.
In the present embodiment, two potentiometers, a main potentiometer 4a and a sub potentiometer 4b, are provided. The steering torque detected by the main potentiometer 4a is set as the main steering torque Tm. Further, the steering torque detected by the sub potentiometer 4b is defined as a sub steering torque Ts.

The reaction force motor 5 is for applying a steering reaction force to the steering wheel 1 and is composed of a brushless motor or the like. Further, the reaction force motor 5 includes a current sensor 5 a that detects an energization current value (actual current) Ir of the reaction force motor 5.
The pinion shaft 7 is connected to the steering mechanism 10. The pinion shaft 7 is provided with a turning motor 8 and a turning angle sensor 9. The steered motor 8 is constituted by a brushless motor or the like, similarly to the reaction force motor 5. The turning angle sensor 9 detects the actual turning angle θt of the front wheels 11R and 11L.

The steering shaft 2 and the pinion shaft 7 are configured to be mechanically connectable by a backup clutch 6. The backup clutch 6 is connected when any abnormality occurs in the steer-by-wire system.
The axial force sensor 12 is provided at the hub portion of the left and right front wheels 11R and 11L. The axial force sensor 12 detects an axial force F (reaction force from the road surface input to the left and right front wheels 11R and 11L) F applied to the rack of the steering mechanism 10.

The turning controller 13 and the steering reaction force controller 14 are connected via a communication line 15.
The steering controller 13 inputs the steering angle θ of the steering wheel 1 detected by the steering angle sensor 3, and the main steering torque Tm and the sub steering torque Ts detected by the steering torque sensor 4.
The steering reaction force controller 14 uses the main steering torque Tm and the sub steering torque Ts detected by the steering torque sensor 4, the actual current Ir detected by the current sensor 5a, and the actual road surface reaction force F detected by the axial force sensor 12. input.

In this steer-by-wire system, the fastening of the backup clutch 6 is released, so that there is no mechanical connection between the steering wheel 1 and the steering mechanism 10.
When the backup clutch 6 is disengaged, the turning controller 13 first calculates a command turning angle corresponding to the steering angle θ. Next, the steered controller 13 calculates a drive command value for the steered motor 8 so that the actual steered angle θt matches the commanded steered angle. The calculated drive command value is output to the steered motor 8. In this way, the steering operation is performed.

Here, the steering controller 13 performs a drive command value (current command value) of the steering motor 8 by steering angle servo control that performs control calculation so that the actual turning angle follows the command turning angle with a predetermined response characteristic. Is calculated. In the steering angle servo control, the drive command value is calculated by feedforward control + feedback control + robust compensation.
Further, the steering reaction force controller 14 calculates a drive command value of the reaction force motor 5 for applying a steering reaction force corresponding to the actual road surface reaction force F. The calculated drive command value is output to the reaction force motor 5. In this way, the reaction force motor 5 is driven to apply a steering reaction force to the steering wheel 1.

Here, similarly to the steering angle servo control described above, the drive command value (current command value) of the reaction force motor 5 is calculated by the reaction force servo control by feedforward control + feedback control + robust compensation.
As described above, when the backup clutch 6 is disengaged, the front wheels 11R and 11L are steered by drivingly controlling the steered motor 8 according to the rotation angle (steering state) of the steering wheel 1. At the same time, the reaction force motor 5 is driven and controlled in accordance with the actual road surface reaction force (the steering state of the front wheels), thereby applying a steering reaction force to the steering wheel 1. In this way, steer-by-wire control (hereinafter referred to as SBW control) is performed.

Further, in this steer-by-wire system, the steering wheel 1 and the steering mechanism 10 are mechanically connected by fastening the backup clutch 6.
In the engaged state of the backup clutch 6, steering assist control (hereinafter referred to as EPS control) for applying a steering assist force that reduces the driver's steering burden to the steering system is performed. Further, when the backup clutch 6 is engaged, the EPS control can be stopped and manual steering can be performed.

When performing EPS control, the steering controller 13 calculates a drive command value of the steering motor 8 for applying a steering assist force according to the steering torque detected by the steering torque sensor 4. The calculated drive command value is output to the steered motor 8. In this way, the steering motor 8 is driven to assist the driver's steering force.
In the present embodiment, when the steering reaction force system is normal (the steering reaction force can be normally applied by the drive control of the reaction force motor 5), the engagement of the backup clutch 6 is released and the SBW control is performed. I do.

If an abnormality occurs in the steering reaction system while the SBW control is being performed, the backup clutch 6 is engaged and the control proceeds to the EPS control. At this time, the EPS control is performed using the steering torque indicating the normal value of the main steering torque Tm and the sub steering torque Ts.
The abnormality diagnosis of the steering torque value is performed by a three-party majority diagnosis using the estimated steering torque Tr estimated based on the main steering torque Tm, the sub steering torque Ts, and the actual current value Ir of the reaction force motor 5.

The steering reaction force controller 14 determines whether to switch from the SBW control to the EPS control.
When the EPS control cannot be continued, the EPS control is stopped and the process shifts to manual steering. Here, the state in which the EPS control cannot be continued means, for example, a state in which an abnormality has occurred in the steered motor 8 and the steering assist force cannot be normally applied.
The turning controller 13 determines whether to switch from EPS control to manual steering.

FIG. 2 is a flowchart showing a control switching processing procedure executed by the steering reaction force controller 14. This control switching process starts when the SBW control is started, and is executed at predetermined time intervals while the SBW control is being performed.
First, in step S1, the steering reaction force controller 14 reads various data. Specifically, the main steering torque Tm and the sub steering torque Ts detected by the torque sensor 2 and the actual current Ir of the reaction force motor 5 detected by the current sensor 5a are read.

Next, in step S2, the steering reaction force controller 14 estimates the steering torque Tr based on the actual current Ir of the reaction force motor 5 read in step S1. Here, the steering torque Tr is calculated by multiplying the actual current Ir by a torque constant Kr (Tr = Kr × Ir). The torque constant Kr is a constant unique to the reaction force motor.
Next, in step S3, the steering reaction force controller 14 performs a three-party majority decision using the main steering torque Tm, the sub steering torque Ts, and the estimated steering torque Tr.

The majority decision diagnosis is performed by comparing three values of the main steering torque Tm, the sub steering torque Ts, and the estimated steering torque Tr. Then, it is determined whether any one of these three values has an error with the other two. If an error greater than a predetermined value has occurred, it is determined that the value is an abnormal value.
In this way, by comparing and diagnosing the three values, it is possible to determine not only whether or not an abnormality has occurred in the steering torque value, but which is indicating an abnormal value.

If it is determined by the majority decision that the three steering torque values are normal, the process proceeds to step S4. On the other hand, when it determines with it being normal, it transfers to step S8 mentioned later.
In step S4, the steering reaction force controller 14 determines whether or not the steering reaction force system is normal. Here, it is determined whether or not the steering reaction force can be normally applied by the drive control of the reaction force motor 5. For example, it is determined whether the motor angle of the reaction force motor 5 is normal, whether the detection of the motor angle of the reaction force motor 5 is performed normally, and whether an excessive current is flowing in the reaction force motor 5.
When the steering reaction force controller 14 determines that the steering reaction force system is normal, the process proceeds to step S5, the SBW control is continued, and the process proceeds to step S1.

On the other hand, when the steering reaction force controller 14 determines in step S4 that an abnormality has occurred in the steering reaction force system, the process proceeds to step S6 and the backup clutch 6 is engaged. Next, the steering reaction force controller 14 proceeds to step S7, performs a transition process to EPS control, and ends the control switching process.
As a transition process to the EPS control, the steering reaction force controller 14 first stops driving the reaction force motor 5. Then, the steering reaction force controller 14 outputs a command signal that instructs the steering controller 13 to start EPS control.

At this time, both the main steering torque Tm and the sub steering torque Ts are normal values. Therefore, a command signal is output to the steering controller 13 so that EPS control is performed using the main steering torque Tm.
In step S8, the steering reaction force controller 14 determines whether one of the main steering torque Tm and the sub steering torque Ts shows an abnormal value based on the majority decision result.

If it is determined that either the main steering torque Tm or the sub steering torque Ts indicates an abnormal value, the process proceeds to step S9. On the other hand, when it is determined that the main steering torque Tm and the sub steering torque Ts indicate normal values, the process proceeds to step S13 described later.
In step S9, the steering reaction force controller 14 determines whether or not the steering reaction force system is normal as in step S4.
When the steering reaction force controller 14 determines that the steering reaction force system is normal, the process proceeds to step S10, the SBW control is continued, and the process proceeds to step S1.

On the other hand, when the steering reaction force controller 14 determines in step S9 that an abnormality has occurred in the steering reaction force system, the process proceeds to step S11 and the backup clutch 6 is engaged. Next, the steering reaction force controller 14 proceeds to step S12, performs a transition process to EPS control similarly to step S7, and ends the control switching process.
At this time, one of the main steering torque Tm and the sub steering torque Ts indicates an abnormal value. Therefore, a command signal is output to the steered controller 13 so that EPS control is performed using the steering torque value determined to be a normal value here.

In Step S13, the steering reaction force controller 14 determines whether or not the estimated steering torque Tr indicates an abnormal value based on the majority decision result.
If it is determined that the estimated steering torque Tr indicates an abnormal value, it is determined that an abnormality has occurred in the steering reaction system, and the process proceeds to step S14. On the other hand, if it cannot be determined which of the main steering torque Tm, the sub steering torque Ts, and the estimated steering torque Tr is an abnormal value, the process proceeds to step S16 described later.

In step S <b> 14, the steering reaction force controller 14 engages the backup clutch 6. Next, the steering reaction force controller 14 proceeds to step S15, performs a transition process to EPS control similarly to step S7, and ends the control switching process.
At this time, both the main steering torque Tm and the sub steering torque Ts are normal values. Therefore, a command signal is output to the steering controller 13 so that EPS control is performed using the main steering torque Tm.
In step S <b> 16, the steering reaction force controller 14 engages the backup clutch 6. Next, the steering reaction force controller 14 proceeds to step S17, transitions to manual steering, and ends the control switching process.

<Operation>
Next, the operation of this embodiment will be described.
Assume that no abnormality has occurred in the steering torque sensor 4 and the steering reaction system. Further, at this time, it is assumed that the SBW control is being executed in a state where the engagement of the backup clutch 6 is released.
In this case, the steering reaction force controller 14 executes the control switching process of FIG. In step S1, the main steering torque Tm, the sub steering torque Ts, and the actual current Ir of the reaction force motor 5 are read. Next, in step S2, the estimated steering torque Tr is calculated based on the actual current Ir.

  Then, a majority decision diagnosis is performed in step S3 using three values of the main steering torque Tm, the sub steering torque Ts, and the estimated steering torque Tr. At this time, since there is no abnormality in the steering torque sensor 4 and the steering reaction force system, there is no error in these three values. Therefore, it determines with Yes by step S3, and transfers to step S4. Moreover, it determines with Yes by step S4, and transfers to step S5. Therefore, the engagement release state of the backup clutch 6 is maintained and the SBW control is continued.

When the driver performs a steering operation in this state, the steering angle sensor 3 detects the steering angle θ input by the driver. Then, the turning controller 13 drives and controls the turning motor 8 so that the actual turning angle θt becomes a turning amount corresponding to the steering angle θ detected by the steering angle sensor 3. Thereby, the front wheels 11R and 11L are steered.
At this time, a road surface reaction force corresponding to the turning of the front wheels 11R and 11L is generated. This road surface reaction force is detected by the axial force sensor 12. Then, the steering reaction force controller 14 drives and controls the reaction force motor 5 so as to apply a steering reaction force corresponding to the actual road surface reaction force F detected by the axial force sensor 12. Thereby, a steering reaction force is applied to the steering wheel 1.

In this way, the SBW control is performed, and the driver can perform a steering operation that matches his / her feeling.
It is assumed that an abnormality has occurred in the main steering torque Tm from this state. In this case, an error occurs between the main steering torque Tm, the sub steering torque Ts, and the estimated steering torque Tr. Since this error is greater than or equal to a predetermined value, the steering reaction force controller 14 determines No in step S3 and proceeds to step S8. At this time, since an abnormality has occurred in the main steering torque Tm, it is determined Yes in step S8, and the process proceeds to step S9. Further, since the steering reaction system is normal, it is determined Yes in step S9, and the process proceeds to step S10. Therefore, the engagement release state of the backup clutch 6 is maintained and the SBW control is continued.

In the SBW control, the steering torque value is not used. Therefore, even if an abnormality occurs in the main steering torque Tm as described above, the SBW control can be continued if the steering reaction system is normal.
Thereafter, when an abnormality occurs in the motor angle sensor of the reaction force motor 5, the steering reaction force controller 14 determines in step S9 that an abnormality has occurred in the steering reaction force system. Therefore, it determines with No by step S9, and transfers to step S11. And the backup clutch 6 is fastened and it transfers to EPS control from SBW control.

  At this time, since an abnormality has occurred in the main steering torque Tm, EPS control is performed using the normal sub steering torque Ts. Therefore, when the driver performs a steering operation here, the steering controller 13 calculates the steering assist force based on the sub steering torque Ts detected by the steering torque sensor 4. And the steering motor 8 is drive-controlled so that this steering assistance force may be provided. This assists the driver's steering force.

  By the way, in general, in an electric power steering apparatus that performs EPS control, when an abnormality of the steering torque sensor is detected, the EPS control is stopped and the process shifts to manual steering. At this time, the steering torque sensor is diagnosed as having a configuration including a main potentiometer and a sub potentiometer. When the error in the steering torque value between the main and the sub is equal to or greater than a predetermined value, it is determined that an abnormality has occurred in the steering torque sensor.

However, when this abnormality diagnosis is applied to a steer-by-wire system that performs SBW control, it may not be possible to shift from SBW control to EPS control during a steering reaction force system failure.
FIG. 3 is a diagram showing a control transition flow when a general steering torque sensor abnormality diagnosis is performed.
When there is no error between the main steering torque value and the sub steering torque value, and the steering reaction system is normal, SBW control is executed. If an abnormality occurs in the steering reaction system from this state, the control shifts from SBW control to EPS control. Thereafter, when the occurrence of an abnormality in the steering torque sensor is detected, it is determined that the EPS control cannot be continued, and the EPS control is stopped and the process proceeds to manual steering.

On the other hand, if an error occurs between the main steering torque value and the sub steering torque value while the SBW control is being performed, the occurrence of an abnormality in the steering torque sensor is detected. However, since the steering torque value is not used in the SBW control, the SBW control can be continued even if an abnormality occurs in the steering torque sensor.
At this time, since the abnormality diagnosis of the steering torque sensor is performed by comparing the two values, it cannot be determined which of the main steering torque value and the sub steering torque value is abnormal. Therefore, if an abnormality occurs in the steering reaction system from this state and the SBW control cannot be continued, it is not possible to shift to the EPS control. Therefore, it shifts from SBW control to manual steering.

As described above, when the shift to the manual steering is performed without the shift to the EPS control, a large change in the steering force occurs. Therefore, the driver feels uncomfortable.
FIG. 4 is a diagram showing a control transition flow when the steering torque sensor abnormality diagnosis of the present embodiment is performed.
In the present embodiment, an abnormality diagnosis of the steering torque sensor is performed by comparing three values of the main steering torque Tm, the sub steering torque Ts, and the estimated steering torque Tr. Therefore, when an abnormality occurs in any one of these three, only the one in which the abnormality has occurred becomes a value different from the other two. Therefore, it is possible to determine which of these three is abnormal.

For example, when an abnormality occurs in the main steering torque Tm, an error of a predetermined value or more occurs in the main steering torque Tm. Therefore, it is possible to appropriately determine that an abnormality has occurred in the main steering torque Tm by the majority decision diagnosis.
Therefore, when the SBW control is performed in a state where the main steering torque Tm is abnormal, if an abnormality occurs in the steering reaction force system, it is possible to shift to the EPS control. At this time, EPS control is performed using the sub steering torque Ts in which no abnormality has occurred.
In this way, it is possible to avoid shifting from SBW control directly to manual steering.

In the present embodiment, the front wheels 11R and 11L constitute steered wheels, the steering mechanism 10 constitutes a steering mechanism, the reaction force motor 5 constitutes a steering reaction force actuator, and the steering motor 8 turns. A rudder actuator is configured. Further, the main potentiometer 4a constitutes first torque detecting means, and the sub potentiometer 4b constitutes second torque detecting means.
Further, step S2 in FIG. 2 corresponds to the steering torque estimating means, steps S5 and S10 correspond to the steering control means, and steps S3, S8 and S13 correspond to the abnormality determining means. Steps S7, S12 and S15 correspond to the steering assist control means, and steps S4, S6, S9, S11 and S14 correspond to the control switching means.

"effect"
(1) The steering unit includes a steering wheel and a steering reaction force actuator that applies a steering reaction force to the steering wheel. The steered portion has a steered wheel and a steered actuator that drives a steered mechanism that steers the steered wheel. The clutch can mechanically connect and disconnect the steering unit and the steered unit.

  The steering control means drives and controls the steered actuator so that the steered wheel has a steered angle corresponding to the steered state with the clutch released, and the steered wheel steered state. Steering control is performed to drive and control the steering reaction force actuator so as to apply a steering reaction force according to the above. The steering assist control means performs steering assist control according to the steering state using at least one of the steering reaction force actuator and the turning actuator as the assist means in a state where the clutch is engaged. The control switching means engages the clutch and switches from the steering control to the steering assist control when a transition condition from the steering control by the steering control means to the steering assist control by the steering assist control means is satisfied.

  The first torque detection means detects the steering torque input to the steering unit as the first steering torque. The second torque detecting means detects the steering torque input to the steering unit as the second steering torque. The steering torque estimating means estimates the steering torque based on the driving state of the steering reaction force actuator. The abnormality determining means is a first steering torque detected by the first torque detecting means, a second steering torque detected by the second torque detecting means, and an estimation estimated by the steering torque estimating means during the steering control by the steering control means. The steering torque is compared, and a steering torque value indicating an abnormal value among the three values is determined.

The steering assist control means performs steering assist control based on the steering torque value determined by the abnormality determination means to indicate a normal value.
As a result, it is possible to determine the steering torque sensor value in which an abnormality has occurred during the steering control (SBW control). Therefore, when SBW control is performed in a state where an abnormality has occurred in the steering torque sensor signal, if a failure occurs in the steering reaction force system, it is possible to shift to steering assist control (EPS control). At this time, in the EPS control, control using a normal steering torque sensor value can be performed.
Thus, since the transition from the SBW control to the EPS control can be ensured, a large change in the steering force can be prevented as compared with the case where the SBW control is shifted to the manual steering.

(2) The steering reaction force actuator includes a reaction force motor that applies a steering reaction force to the rotating shaft of the steering wheel. The steering torque estimating means estimates the steering torque based on the energization current value of the reaction force motor.
Thus, it is possible to diagnose whether or not the reaction force motor is operating normally when diagnosing an abnormality in the steering torque value. Therefore, the abnormality diagnosis function of the reaction force motor (the steering reaction force system failure diagnosis function) can be provided.

(3) The control switching means determines that the transition condition from the steering control to the steering assist control is satisfied when an abnormality has occurred in the steering reaction force actuator.
Thereby, when it is determined in the abnormality diagnosis of the steering torque value that an abnormality has occurred in the estimated steering torque, it can be determined that the transition condition is satisfied. Therefore, when the SBW control cannot be continued, it is possible to stop the SBW control and shift to the EPS control.

(4) During the steering control, the detected first steering torque and second steering torque are compared with the third steering torque estimated based on the driving state of the steering reaction force actuator, and the normal value of the three values is compared. The steering torque value is determined. When the transition condition from the steering control to the steering assist control is satisfied, the steering assist control is performed based on the determined normal steering torque value.
Thereby, when steering control (SBW control) is performed in a state where an abnormality has occurred in the steering torque sensor signal, when a failure occurs in the steering reaction force system, the control shifts to steering assist control (EPS control). be able to. Therefore, a large change in steering force can be prevented as compared with the case of shifting from SBW control to manual steering.

<Modification>
In the above-described embodiment, the case where the EPS control is performed using the steered motor 8 as an assist unit has been described. However, the EPS control can also be performed using the reaction force motor 5 as an assist unit. Furthermore, EPS control can be performed using both the reaction force motor 5 and the steering motor 8 as assist means.
In the above embodiment, the case where it is determined that the transition condition to the EPS control is satisfied when an abnormality occurs in the steering reaction system has been described. However, other transition conditions can be set. For example, when the steering amount by the driver is large and the turning angles of the front wheels 11R and 11L are large (close to the maximum turning angle) or the like, it is preferable to apply the steering assist force. It can also be determined that it has been established.

1 is an overall configuration diagram showing an embodiment of a vehicle steering control device according to the present invention. It is a flowchart which shows the control switching process sequence which a steering reaction force controller performs. It is a figure which shows the control transfer flow at the time of performing a general steering torque sensor abnormality diagnosis. It is a figure which shows the control transfer flow at the time of performing the steering torque sensor abnormality diagnosis of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Steering angle sensor 4 Steering torque sensor 5 Reaction force motor 6 Backup clutch 7 Pinion shaft 8 Steering motor 9 Steering angle sensor 10 Steering mechanism 11R, 11L Front wheel 12 Axial force sensor 13 Steering controller 14 Steering Reaction force controller 15 Communication line

Claims (4)

A steering unit having a steering wheel and a steering reaction force actuator for applying a steering reaction force to the steering wheel;
A steered portion having a steered wheel and a steered actuator that drives a steered mechanism that steers the steered wheel;
A clutch capable of mechanically connecting and disconnecting the steering unit and the steered unit;
In a state where the clutch is disengaged, the steered actuator is driven and controlled so that a steered angle of the steered wheel becomes a steered angle corresponding to a steered state, and the steered wheel is brought into a steered state. Steering control means for performing steering control for driving and controlling the steering reaction force actuator so as to apply a corresponding steering reaction force;
Steering assistance control means for performing steering assistance control according to a steering state with at least one of the steering reaction force actuator and the steering actuator as assistance means in a state where the clutch is engaged;
A control switching means for fastening the clutch and switching from the steering control to the steering assist control when a transition condition from the steering control by the steering control means to the steering assist control by the steering assist control means is established;
First torque detection means for detecting a steering torque input to the steering section as a first steering torque;
Second torque detecting means for detecting a steering torque input to the steering section as a second steering torque;
Steering torque estimating means for estimating the steering torque based on the driving state of the steering reaction force actuator;
During the steering control by the steering control means, the first steering torque detected by the first torque detection means, the second steering torque detected by the second torque detection means, and the estimated steering estimated by the steering torque estimation means An abnormality determining means for determining a steering torque value indicating an abnormal value among the three values by comparing the torque,
The steering assist control means have lines the steering assist control based on the steering torque value is determined to indicate a normal value in the abnormality determination means,
The control switching means determines that a condition for transition from the steering control to the steering assist control is satisfied when the abnormality determination means determines that only the estimated steering torque indicates an abnormal value. A vehicle steering control device. The steering reaction force actuator includes a reaction force motor that applies a steering reaction force to the rotating shaft of the steering wheel.
The vehicle steering control device according to claim 1, wherein the steering torque estimating unit estimates the steering torque based on an energization current value of the reaction force motor.   The control switching means determines that a transition condition from the steering control to the steering assist control is satisfied when an abnormality occurs in the steering reaction force actuator. The vehicle steering control device described in 1. During the steering control, the detected first steering torque and second steering torque are compared with the third steering torque estimated based on the driving state of the steering reaction force actuator, and the normal value of the three values is indicated. When the transition condition from the steering control to the steering assist control is satisfied, the steering control is stopped and the determined normality is determined. A steering control method for a vehicle, wherein the steering assist control is performed based on a stable steering torque value.

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