JP2010215191A - Vehicular steering device and vehicular steering method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering device and a vehicular steering method, capable of accurately suppressing one-side-drift of a vehicle without providing a yaw rate sensor. <P>SOLUTION: The history of wheel speed V<SB>FL</SB>-V<SB>RR</SB>detected by wheel speed sensors 16FL-16RR is obtained, and statistically processed, thereby estimating a detection error of the wheel speed V<SB>FL</SB>-V<SB>RR</SB>generated due to the difference of right and left tire movement radii. Then, the wheel speed V<SB>FL</SB>-V<SB>RR</SB>detected by wheel speed sensors 16FL-16RR is corrected by the estimated detection error. On the basis of the corrected V<SB>FL</SB>-V<SB>RR</SB>, a yaw rate ϕ of a vehicle is estimated, and on the basis of the estimated yaw rate ϕ, the traveling straight ahead determination of the vehicle is carried out. One-side-drift suppressing control is carried out, which adds a one-side-drift steering assisting torque in a direction canceling steering torque Tp to a steering portion, when the vehicle travels straight ahead. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention belongs to the technical field of a vehicle steering apparatus that performs single flow suppression control for suppressing single flow of a vehicle.

  Conventional vehicle steering devices estimate inputs such as crosswinds, road surface cants, and rough roads as dynamic disturbances, and control the steering assist force to compensate for the estimated disturbances (see, for example, Patent Document 1). ).

JP 2001-1923 A

By the way, the single flow of the vehicle includes a steady disturbance caused by the vehicle and a disturbance caused by a cross wind or the like. However, in this vehicle steering apparatus, it is possible to compensate for the dynamic disturbance, but no consideration is given to steady disturbance caused by the vehicle.
Therefore, the yaw rate actually generated in the vehicle is detected, it is determined whether or not the vehicle is in the straight traveling state based on the detected yaw rate, and the steering torque when the vehicle is determined to be in the straight traveling state Based on this history, it is conceivable to compensate for steady disturbance caused by the vehicle by applying a one-flow restraining steering assist force in a direction that cancels the steering torque during straight traveling. However, in this case, since it is necessary to separately provide a yaw rate sensor for detecting the yaw rate, the cost increases.
Therefore, an object of the present invention is to provide a vehicle steering apparatus and a vehicle steering method that can accurately suppress a single flow of a vehicle without providing a yaw rate sensor.

  In order to solve the above-described problem, the vehicle steering apparatus according to the present invention estimates the yaw rate of the vehicle in which an error caused by the difference between the left and right wheel radii is corrected based on the wheel speed of each wheel. Based on the estimated yaw rate, it is determined whether or not the vehicle is traveling straight. Then, based on the history of steering torque generated in the steering section when it is determined that the vehicle is traveling straight, a single-flow suppression steering assist torque that cancels the steering torque during straight traveling is added to the steering section. One-flow suppression control is performed.

  According to the present invention, since the yaw rate of the vehicle is estimated based on the wheel speed, it is not necessary to separately provide a yaw rate sensor or the like. Further, since the error caused by the difference between the left and right wheel moving radii is corrected when estimating the yaw rate, it is possible to properly determine whether the vehicle is going straight. Therefore, the accuracy of the single flow suppression can be improved with a simple configuration.

1 is a schematic configuration diagram of a vehicle steering apparatus according to a first embodiment. It is a block diagram which shows the structure of the controller in 1st Embodiment. It is an electric current command value calculation map. It is a flowchart which shows the single flow suppression control processing procedure performed in the single flow suppression control part in 1st Embodiment. It is a figure for demonstrating the operation | movement of this embodiment. It is a flowchart which shows the single flow suppression control processing procedure performed by the single flow suppression control part in 2nd Embodiment. It is a flowchart which shows the single flow suppression control processing procedure performed in the single flow suppression control part in 3rd Embodiment. It is a flowchart which shows the single flow suppression control processing procedure performed in the single flow suppression control part in 4th Embodiment. It is a drive torque estimation map. It is a torque increase / decrease calculation map. It is a flowchart which shows a torque increase / decrease calculation process procedure. It is a flowchart which shows the single flow suppression control process sequence performed with the single flow suppression control part in 5th Embodiment. It is a block diagram which shows the structure of the controller in 6th Embodiment. It is a flowchart which shows the single flow suppression control process sequence performed with the single flow suppression control part in 6th Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<< First Embodiment >>
"Constitution"
FIG. 1 is a diagram showing a configuration of a vehicle steering apparatus according to a first embodiment of the present invention.
The vehicle steering apparatus includes a steering wheel 1 operated by a driver, and a steering mechanism 3 that steers a front wheel (steering wheel) 2 in accordance with an operation amount of the steering wheel 1.

A steering shaft (steering column) 4 is integrally coupled to the steering wheel 1. A torque sensor 5 and a speed reducer 6 are provided on the steering shaft 4. In addition, a motor 7 is connected via a speed reducer 6. The motor current sensor 15 detects an actual current (motor current) supplied to the motor 7.
A pinion 8 of a rack and pinion mechanism is connected to the tip of the steering shaft 4. The knuckle arms of the left and right front wheels 2 are connected to both ends of the rack 9 that can mesh with the pinion 8 and reciprocate in the vehicle width direction via tie rods 10, respectively.

The wheel speed sensors 16FL to 16RR detect the wheel rotation speed of each wheel, and detect each wheel speed from the detected wheel rotation speed and the design value of the tire moving radius stored in the ROM or the like. Here, wheel speed [m / s] = wheel rotation speed [rpm] / 60 × design value of tire dynamic radius [m].
The controller 11 inputs information from the torque sensor 5 and the vehicle speed sensor 13. Based on these pieces of information, a steering assist force that assists the driver's steering force is generated. Further, the motor 7 is driven by a command value corresponding to the steering assist force. In this way, steering assist control is performed.

  Furthermore, the controller 11 inputs information from the motor current sensor 15 and the wheel speed sensors 16FL to 16RR. Then, based on these pieces of information, the turning torque (pinion shaft torque) when the vehicle is traveling straight is stored in a memory (not shown), and the average value of the history of the memory is calculated. Then, the single flow suppression control is performed in which the calculated value is added to the steering assist force command value as a torque necessary for the single flow suppression.

In the present embodiment, the yaw rate generated in the vehicle is estimated based on the wheel speed of each wheel. Then, the straight traveling state of the vehicle is determined based on the estimated yaw rate.
By the way, the actual tire moving radius (wheel moving radius) varies depending on the tire pressure and the wear state. When the left and right tire moving radii are different, even when the speeds actually generated on the left and right wheels are different, the wheel speeds of the left and right wheels detected by the wheel speed sensors 16FL to 16RR (the number of rotations of the wheel x the design value of the tire moving radius). ) Are equal.
Therefore, in the present embodiment, an error of the wheel speed detection value generated due to the difference in tire dynamic radius of each wheel is calculated, and each wheel speed detected by the wheel speed sensors 16FL to 16RR is corrected by the error. Then, the yaw rate generated in the vehicle is calculated based on the corrected wheel speed.

(Configuration of controller)
FIG. 2 is a block diagram showing the configuration of the controller 11.
The controller 11 includes a steering assist control unit 21 that performs normal steering assist control, a single flow suppression control unit 22 that performs vehicle single flow suppression control, and a current command value correction unit 23.
The steering assist control unit 21 refers to the current command value calculation map shown in FIG. 3 based on the steering torque T and the vehicle speed V, and calculates the motor current command value Ia. The calculated motor current command value Ia is output to the current command value correction unit 23.

The single flow suppression control unit 22 calculates a single flow suppression motor current command value Ib based on the steering torque T, the motor current Im, and the wheel speed V _i (i = FL to RR). The calculated current command value Ib is output to the current command value correction unit 23. A method for calculating the motor current command value Ib will be described later.
The current command value correction unit 23 adds the motor current command value Ia calculated by the steering assist control unit 21 and the motor current command value Ib calculated by the single flow suppression control unit 22 to calculate a final current command value I. To do. The calculated motor current command value I is output to the motor 7.

Next, the configuration of the single flow suppression control unit 22 will be specifically described.
The single flow suppression control unit 22 includes a pinion torque estimation unit 221, a single flow suppression torque calculation unit 222, a single flow suppression current command value calculation unit 223, a wheel speed history storage unit 224, a dynamic radius difference calculation unit 225, and a wheel speed. A correction unit 226, a yaw rate calculation unit 227, and a straight traveling determination unit 228 are provided.
The pinion torque estimation unit 221 receives the steering torque T and the motor current Im, and estimates the pinion torque Tp based on the following formula based on these.
Tp = T + K _M × Im (1)
Here, K _M is a coefficient for converting the motor current Im to the steering assist torque.
In addition, when temperature dependence, speed dependence characteristics, etc. are strong, pinion torque Tp is estimated using a map.

  The single flow suppression torque calculation unit 222 inputs the pinion torque Tp estimated by the pinion torque estimation unit 221 and a straight travel determination flag FLG that is a determination result of a straight travel determination unit 228 described later. Then, the pinion torque Tp when the straight traveling determination flag FLG is “1” indicating that the vehicle is in the straight traveling state is output as torque (single flow suppression steering assist torque) Tb for suppressing single flow.

The single flow suppression current command value calculation unit 223 calculates a motor current command value Ib for adding the single flow suppression torque Tb output from the single flow suppression torque calculation unit 222 to the steering unit. The calculated motor current command value Ib is output to the current command value correction unit 23.
The wheel speed history storage unit 224 stores the history of the wheel speeds V _{FL to} V _RR detected by the wheel speed sensors 16FL to 16RR.
The dynamic radius difference calculation unit 225 statistically processes the wheel speed history stored in the wheel speed history storage unit 224, and detects an error in the detected wheel speed due to the difference in tire dynamic radius (hereinafter simply referred to as “difference in tire dynamic radius”). ").

The wheel speed correction unit 226 corrects and outputs the wheel speeds V _{FL to} V _RR detected by the wheel speed sensors 16 _FL to 16 _RR based on the difference in tire dynamic radius estimated by the dynamic radius difference calculation unit 225.
The yaw rate calculation unit 227 calculates the yaw rate φ generated in the vehicle based on the wheel speeds V _{FL to} V _RR corrected by the wheel speed correction unit 226.
The straight traveling determination unit 228 determines whether or not the vehicle is traveling straight on the basis of the yaw rate φ calculated by the yaw rate calculation unit 227. When it is determined that the vehicle is traveling straight, a straight traveling determination flag FLG = 1 is output. When it is determined that the vehicle is not traveling straight, a straight traveling determination flag FLG = 0 is output.

(Single flow suppression control processing procedure)
Next, the single flow suppression control processing procedure executed by the single flow suppression control unit 22 will be described.
FIG. 4 is a flowchart showing a single flow suppression control processing procedure executed by the single flow suppression control unit 22. This single flow suppression control process is repeatedly executed at a predetermined control cycle during traveling (when the vehicle speed sensor 13 detects vehicle speed ≠ 0).
First, in step S1, the single flow suppression control unit 22 reads signals from various sensors. Specifically, the wheel speed V _i detected by the wheel speed sensors 16FL to 16RR, the steering torque T detected by the torque sensor 5, and the motor current Im detected by the motor current sensor 15 are acquired.

Next, in step S2, the single flow suppression control unit 22 records the wheel speed V _i as a history, and proceeds to step S3.
In step S3, pent suppression control unit 22 determines whether the history of the wheel speed V _i is sufficiently acquired. Here, the predetermined period of time history (e.g., 30 minutes) when acquiring the history of the wheel speed V _i is determined to be sufficiently acquired, the process proceeds to step S4. On the other hand, when it is determined that no history of the wheel speed V _i fully acquired, the process proceeds to step S6 to be described later. The predetermined period is set to a period that is sufficiently long that the calculation accuracy of the difference in tire dynamic radius is reliable.

In step S4, the single flow suppression control unit 22 statistically processes the history of the wheel speed V _i and calculates a difference in tire moving radius.
First, the average value of the wheel speed history is calculated for each of the left front wheel and the right front wheel. At this time, in order to remove an abnormal value, the maximum n data and the minimum n data may be excluded and averaged. Next, the difference between the average value of the right wheel speeds V _FR and V _RR calculated by statistical processing and the average value of the left wheel speeds V _FL and V _RL (= the average value of the right wheel speed−the left wheel speed) (Average value) is calculated. The calculated value is defined as a difference in tire dynamic radius.
In addition, although the case where the difference of the average value of wheel speed was calculated | required here was demonstrated, ratio of the average value of right wheel speed and the average value of left wheel speed (= average value of right wheel speed / average value of left wheel speed) ) May be a difference in tire dynamic radius.

Next, in step S5, the single flow suppression control unit 22 corrects the wheel speeds V _{FL to} V _RR acquired in step S1, using the difference in tire dynamic radius calculated in step S4. At this time, correction is always performed by subtracting the calculated difference in tire dynamic radius from the right wheel speeds V _FR and V _RR . Alternatively, correction is performed to always add the calculated difference in tire dynamic radius to the left wheel speeds V _FL and V _RL .
When calculating the difference in tire dynamic radius using the ratio between the average value of the right wheel speed and the average value of the left wheel speed, the right wheel speeds V _FR and V _RR are calculated based on the calculated tire dynamic radius. Make corrections that always divide by difference. Or, the left wheel speeds V _FL, the V _RL, always perform multiplying correction differences calculated tire dynamic radius.

Next, in step S6, the single flow suppression control unit 22 calculates the yaw rate φ generated in the vehicle based on the wheel speed V _i . The yaw rate φ is calculated using the following equation.
φ = (average wheel speed on the right side-average value on the left wheel speed) / tread (2)
At this time, if the wheel speed V _i is corrected in step S5, the yaw rate φ is calculated using the corrected wheel speed V _i . On the other hand, no history of the wheel speed V _i fully acquired, if not corrected wheel speed V _i calculates the yaw rate φ by using the wheel speed V _i obtained in the step S1.

Next, in step S7, the single flow suppression control unit 22 determines whether or not the absolute value | φ | of the yaw rate φ calculated in step S6 is less than the yaw rate threshold φth. When | φ | <φth, the process proceeds to step S8, and when | φ | ≧ φth, the process proceeds to step S11 described later. Here, the yaw rate threshold φth is set to a value at which it can be determined that the vehicle is traveling straight.
In step S8, the single flow suppression control unit 22 estimates the pinion torque Tp based on the equation (1) based on the steering torque T and the motor current Im acquired in step S1, and proceeds to step S9.

In step S9, the single flow suppression control unit 22 records the pinion torque Tp estimated in step S8 in the history, and proceeds to step S10.
In step S10, the single flow suppression control unit 22 statistically processes the history of the pinion torque Tp, and calculates the single flow suppression torque Tb for suppressing the single flow. Here, the history of the pinion torque Tp is averaged, and the result is defined as a single flow suppression torque Tb. At this time, in order to remove an abnormal value, the maximum n data and the minimum n data may be excluded and averaged.

Next, in step S11, the single flow suppression control unit 22 calculates a motor current command value Ib for adding the single flow suppression torque Tb to the steering unit. At this time, if the vehicle is traveling straight (Yes in step S7), the motor current command value Ib is calculated and output based on the single flow suppression torque Tb calculated in step S10. On the other hand, when the vehicle is not traveling straight (No in step S7), the motor current command value Ib calculated in the previous control cycle is output as it is.
In this way, based on the average value of the left and right wheel speed histories, the error of the wheel speed detection value generated due to the difference between the left and right tire moving radii is calculated, and the error of the calculated wheel speed detection value is corrected. Then, the straight traveling state of the vehicle is determined based on the yaw rate φ calculated based on the corrected wheel speed, and the single flow suppression control is performed.

<Operation>
Next, the operation of the first embodiment will be described.
Here, as shown in FIG. 5 (a), a vehicle that flows unilaterally to the left in a state in which the handle is released will be described. The tire moving radii of the left and right wheels of this vehicle are assumed to be equal.
When the tire moving radii of the left and right wheels are equal, the left and right wheel speed detection values during straight traveling are equal. Therefore, the difference between the average values of the left and right wheel speed histories is zero. This is due to the fact that the number of scenes traveling on a straight road is the largest in the predetermined period of acquiring the wheel speed history.

Thereby, the moving radius difference calculation unit 225 sets the difference between the left and right tire moving radii to 0 (step S4). Therefore, the wheel speed correction unit 226 sets the wheel speeds V _{FL to} V _RR detected by the wheel speed sensors 16FL to 16RR as corrected wheel speeds as they are (step S5).
Next, the yaw rate calculation unit 227 calculates the yaw rate φ from the corrected wheel speed (= sensor detection value) (step S6). The straight traveling determination unit 228 determines that the vehicle is traveling straight when the yaw rate φ calculated by the yaw rate calculation unit 227 is less than the yaw rate threshold φth (step S7).

  Then, the single flow suppression torque calculation unit 222 records the pinion torque Tp at this time in the history (steps S8 and S9), and statistically processes the history to calculate the single flow suppression torque Tb (step S10). Further, the single flow suppression current command value calculation unit 223 calculates a motor current command value Ib for adding the single flow suppression torque Tb calculated by the single flow suppression torque calculation unit 222 to the steering unit (step S11).

The calculated motor current command value Ib is output to the current command value correction unit 23. The current command value correction unit 23 corrects the current command value Ia by adding the current command value Ib to the current command value Ia calculated by the steering assist control unit 21. Then, the motor 7 is driven and controlled with the current command value I (= Ia + Ib).
In this way, the single flow suppression control is performed. As a result, the steered wheel is cut in the right direction to suppress the single flow, and as shown in FIG. 5B, the vehicle maintains the straight traveling state even when the steering wheel is released.

  On the other hand, if the left and right tire radii are different (right side> left side), the left wheel rotation speed is larger than the right side even if the vehicle is traveling straight and the speed at which the wheels are actually generated is the same. Therefore, the wheel speed sensor detects the left wheel speed to a value larger than the right side. In the case of such a vehicle, the left and right wheel rotational speeds become equal when making a left turn, and thus the wheel speed sensor detects the left and right wheel speeds equally when making a left turn.

As shown in FIG. 5C, in the case of a vehicle with different left and right tire moving radii (right side> left side) and a vehicle that unilaterally flows to the left side with the handle released, single flow suppression control is performed using the detected value of the wheel speed sensor as it is. As shown in FIG. 5D, the vehicle further flows to the left.
If the straight value of the vehicle is determined using the detection value of the wheel speed sensor as it is, for the reason described above, it is erroneously determined that the vehicle is traveling straight ahead when turning left. For this reason, the pinion torque Tp at the time of turning left is set as the single flow suppression torque Tb. As a result, by performing the single flow suppression control, the steered wheel is cut leftward, which promotes the single flow of the vehicle.

On the other hand, in this embodiment, the detection value error of the wheel speed sensor generated due to the difference between the left and right tire moving radii is estimated, and the vehicle is determined to go straight on the basis of the wheel speed corrected for this error. Thereby, when the vehicle is traveling straight ahead, it can be properly determined that the vehicle is traveling straight, and the single flow of the vehicle can be suppressed stably.
When the tire moving radius on the right side is larger than the tire moving radius on the left side, the average value of the wheel speed history detected by the wheel speed sensor is larger on the left side. Therefore, the average value of the right wheel speed minus the average value of the left wheel speed is <0. The moving radius difference calculation unit 225 sets the calculation result of (average value of right wheel speed−average value of left wheel speed) as a difference between the left and right tire moving radii (step S4). Then, the wheel speed correction unit 226 subtracts the difference in tire dynamic radius from the right wheel speeds V _FL and V _FR detected by the wheel speed sensors 16FL and 16FR (step S5). As a result, the right wheel speeds V _FL and V _FR are increased and corrected.

The yaw rate calculation unit 227 calculates the yaw rate φ from the corrected wheel speed (step S6). The corrected wheel speed is corrected so that the difference between the left and right wheel speeds becomes zero when the vehicle is traveling straight ahead. Therefore, the yaw rate calculation unit 227 calculates the yaw rate φ to 0 when the vehicle is traveling straight ahead. Therefore, the straight traveling determination unit 228 can appropriately determine that the vehicle is traveling straight when the vehicle is traveling straight.
Then, the steered wheel is turned to the right to restrain the single flow by performing the single flow suppression control, and as shown in FIG. 5E, the vehicle maintains the straight traveling state even when the steering wheel is released.

In FIG. 1, wheel speed sensors 16FL to 16RR constitute wheel speed detecting means. In FIG. 2, the pinion torque estimation unit 221 constitutes a steering torque detection unit, the single flow suppression torque calculation unit 222 and the single flow suppression current command value calculation unit 223 configure a single flow suppression control unit, and a wheel speed history storage unit. 224, the dynamic radius difference calculation unit 225, the wheel speed correction unit 226, and the yaw rate calculation unit 227 constitute a yaw rate estimation unit, and the straight traveling determination unit 228 constitutes a straight traveling state determination unit.
Further, in FIG. 4, steps S2 to S4 constitute error estimation means, step S5 constitutes error correction means, and step S6 constitutes yaw rate calculation means.

"effect"
(1) The yaw rate estimation means estimates the yaw rate of the vehicle in which an error caused by the difference between the left and right wheel moving radii is corrected based on the wheel speed of each wheel detected by the wheel speed detection means. The straight traveling state determination unit determines whether or not the vehicle is in a straight traveling state based on the yaw rate estimated by the yaw rate estimation unit.
The steered torque detecting means detects the steered torque of the steered portion that steers the steered wheels. The single flow suppression control means cancels the turning torque during straight running based on the history of turning torque detected by the turning torque detecting means when the straight running state judging means judges that the vehicle is running straight. A single flow suppression control is performed in which a single flow suppression steering assist torque is added to the steering unit.
Thus, since the yaw rate of the vehicle is estimated based on the wheel speed, it is not necessary to separately provide a yaw rate sensor or the like. Therefore, the cost can be reduced accordingly. Further, since the error caused by the difference between the left and right wheel moving radii is corrected when estimating the yaw rate, it is possible to properly determine whether the vehicle is going straight. Therefore, the accuracy of the single flow suppression can be improved with a simple configuration.

(2) The error estimation means estimates an error of the wheel speed detection value as an error caused by a difference between the left and right wheel moving radii based on the wheel speed history detected by the wheel speed detection means. The error correction unit corrects the error of the wheel speed detection value estimated by the error estimation unit. The yaw rate calculation means calculates the yaw rate of the vehicle based on the wheel speed corrected by the error correction means.
Thereby, when estimating the yaw rate, it is possible to correct an error in the detected wheel speed due to the difference between the left and right wheel moving radii. As a result, it is possible to appropriately determine whether the vehicle is going straight.

(3) The error estimation means calculates an average value of the wheel speed of the right wheel and an average value of the wheel speed of the left wheel based on the wheel speed history detected by the wheel speed detection means, and calculates a difference between these average values. This is an error in the wheel speed detection value.
Therefore, it is possible to estimate and correct an error in the wheel speed detection values of the left and right wheels when the vehicle is traveling straight ahead. Therefore, it can be appropriately determined that the vehicle is traveling straight when traveling straight.

(4) The error estimation means calculates the average value of the wheel speed of the right wheel and the average value of the wheel speed of the left wheel based on the history of the wheel speed detected by the wheel speed detection means, and calculates the ratio of these average values. This is an error in the wheel speed detection value.
Therefore, it is possible to estimate and correct an error in the wheel speed detection values of the left and right wheels when the vehicle is traveling straight ahead. Therefore, it can be appropriately determined that the vehicle is traveling straight when traveling straight.

(5) The error estimation means estimates an error caused by a difference between the left and right wheel moving radii based on the history acquired for a predetermined period. The yaw rate estimating means directly calculates the yaw rate of the vehicle from the wheel speed detected by the wheel speed detecting means until the predetermined period elapses from the start of history acquisition.
Thus, during the period from the start of history acquisition until a predetermined period elapses, the single-flow suppression control is performed with the wheel speed detection value trusted. Thereby, the period which does not implement single flow suppression control is not made.

(6) Based on the wheel speed of each wheel, the yaw rate of the vehicle in which an error caused by the difference between the left and right wheel radii is corrected is estimated. Based on the estimated yaw rate, it is determined whether or not the vehicle is traveling straight. A single flow that adds a single flow suppression steering assist torque to the steering unit that cancels the steering torque during straight traveling based on the history of the steering torque generated in the steering unit when it is determined that the vehicle is traveling straight. Perform suppression control.
Therefore, it is possible to accurately determine whether the vehicle is traveling straight and to suppress the single flow of the vehicle with high accuracy.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described.
In the second embodiment, an external memory for storing the difference in tire dynamic radius is provided, and the difference in tire dynamic radius calculated in the previous control cycle is stored when the ignition switch is turned off.
"Constitution"
The overall configuration of the vehicle steering apparatus in the second embodiment is the same as that of the first embodiment described above shown in FIG.
(Single flow suppression control processing procedure)
The single flow suppression control processing procedure executed by the single flow suppression control unit 22 of the second embodiment will be described.

  FIG. 6 is a flowchart illustrating a single flow suppression control processing procedure executed by the single flow suppression control unit 22 according to the second embodiment. This single flow suppression control process is the same as that of FIG. 4 except that steps S21 to S24 are added in the single flow suppression control process shown in FIG. Accordingly, parts corresponding to those in FIG.

In step S21, the single flow suppression control unit 22 determines the on / off state of the ignition switch. If it is determined that the ignition switch has been switched from the on state (IGNON) to the off state (IGNOFF), the process proceeds to step S22.
In step S22, the single flow suppression control unit 22 stores the difference in tire dynamic radius calculated in the previous control cycle in the external memory, and ends the single flow suppression control process as it is.

If it is determined in step S21 that the ignition switch has been switched from the off state to the on state, the process proceeds to step S23. In step S23, the single flow suppression control unit 22 reads the difference in tire dynamic radius stored in the external memory, and proceeds to step S1.
On the other hand, if it is determined in step S21 that the ignition switch is kept on, the process proceeds to step S1.

Further, in step S3, when the history of the wheel speed V _i is determined not to be sufficiently acquired, the process proceeds to step S24. Then, in step S24, pent suppression control unit 22 uses the difference in tire's dynamic radius read from the external memory in step S23, corrects each wheel speed V _FL ~V _RR acquired in step S1. The correction method for the wheel speeds V _{FL to} V _{RR is the same as} the correction method in step S5 described above.
With such a configuration, the wheel speed detection value is corrected by using the difference in tire dynamic radius stored in the external memory during the period from when the ignition switch is switched from the off state to the on state until the wheel speed history is sufficiently acquired. Thus, the single flow suppression control can be performed.
In FIG. 6, step S22 constitutes a storage means.

"effect"
(7) The error estimation means estimates an error caused by a difference between the left and right wheel moving radii based on the history acquired for a predetermined period. The storage means stores an error caused by the difference between the left and right wheel moving radii estimated by the error estimation means when the ignition switch transitions from the on state to the off state. The error correction unit corrects an error caused by a difference between the left and right wheel moving radii stored in the storage unit from the start of history acquisition until a predetermined period elapses.
Thus, even before the wheel speed history is sufficiently acquired, it is possible to suppress the one-sided flow of the vehicle from the time when the ignition switch is switched to the ON state.

<< Third Embodiment >>
Next, a third embodiment of the present invention will be described.
In the third embodiment, a history of wheel speeds used for calculating a difference in tire dynamic radius is selected.
"Constitution"
The overall configuration of the vehicle steering apparatus in the third embodiment is the same as that of the first embodiment described above shown in FIG.
(Single flow suppression control processing procedure)
A single flow suppression control processing procedure executed by the single flow suppression control unit 22 of the third embodiment will be described.
FIG. 7 is a flowchart illustrating a single flow suppression control processing procedure executed by the single flow suppression control unit 22 of the third embodiment. This single flow suppression control process is the same as that of FIG. 4 except that step S31 is added before step S2 in the single flow suppression control process shown in FIG. Accordingly, parts corresponding to those in FIG.

In step S31, the single flow suppression control unit 22 performs a history selection of the wheel speed V _i .
Here, differential values of the wheel speeds V _i are respectively obtained, and when at least one of them is equal to or higher than a predetermined threshold, it is determined that the selection condition is not satisfied, and is excluded from the history. Here, the threshold value is set to a wheel speed at which it can be determined that the vehicle is traveling on a rough road such as a gravel road.
In addition, a predetermined period (a period during which a rough road may continue) is excluded from the history after the differential value of the wheel speed V _i is less than the above threshold value from a state where the differential value is higher than the above threshold value.

Furthermore, the average value of the wheel speeds V _i of the four wheels is used as a reference, and the reference value and the wheel speed V _{i of} each wheel are compared. If the wheel speed V _i exists, it is excluded from the history.
Further, when the vehicle is traveling at an extremely low speed (for example, the vehicle speed is less than 10 km / h), it is excluded from the history.
In addition to the above, if it is determined that there is a possibility that the vehicle is traveling on a rough road or the wheels are slipping, it is determined that the selection condition is not satisfied, and it is excluded from the history.

Then, the process proceeds to step S2 only when the history selection condition is satisfied, and when the history selection condition is not satisfied, the one-flow suppression control process is terminated as it is.
With such a configuration, it is possible to prevent the wheel speed from being included in the history when traveling on rough roads such as gravel roads. Therefore, the difference in tire dynamic radius can be calculated using only reliable values.
In FIG. 7, step S31 constitutes a sorting means.
"effect"
(8) The sorting means sorts the wheel speed detected by the wheel speed detecting means. The yaw rate estimation means estimates the yaw rate of the vehicle based on the wheel speed that satisfies the selection condition of the selection means.
As a result, a more accurate straight-ahead determination can be made.

<< Fourth Embodiment >>
Next, a fourth embodiment of the present invention will be described.
In the fourth embodiment, when there is a difference in the tire moving radius of the drive wheel, the one-way suppression torque Tb is corrected to increase or decrease.
"Constitution"
The overall configuration of the vehicle steering apparatus in the fourth embodiment is the same as that of the first embodiment described above shown in FIG.

(Single flow suppression control processing procedure)
A single flow suppression control processing procedure executed by the single flow suppression control unit 22 of the fourth embodiment will be described.
FIG. 8 is a flowchart illustrating a single flow suppression control processing procedure executed by the single flow suppression control unit 22 according to the fourth embodiment. This single flow suppression control process is the same as that of FIG. 4 except that steps S41 to S43 are added in the single flow suppression control process shown in FIG. Accordingly, parts corresponding to those in FIG.

In step S41, the single flow suppression control unit 22 determines whether there is a difference in the tire moving radius of the drive wheel. If it is determined that there is a difference in the tire moving radius of the drive wheel, the process proceeds to step S42, and otherwise, the process proceeds to step S11.
Here, first, statistical processing is performed on the history of the wheel speeds of the left front wheel and the right front wheel in the same manner as in the first embodiment described above. At the same time, the history of the wheel speeds of the left rear wheel and the right rear wheel is statistically processed by the same method as in the first embodiment described above.

Further, which of the front wheels and the rear wheels is the driven wheel and which is the driving wheel is stored in advance as data, and the stored data is read and determined.
In this way, it is determined whether there is a difference in the tire moving radius of the drive wheel.
In step S42, the single flow suppression control unit 22 calculates a torque increase / decrease ΔT for increasing / decreasing the single flow suppression torque Tb (torque increase / decrease calculation processing). Here, the pinion torque necessary for canceling the turning moment of the vehicle caused by the difference in the tire moving radius of the driving wheel is the torque increase / decrease ΔT.

Hereinafter, a method of calculating the torque increase / decrease ΔT will be specifically described.
First, the concept will be described.
The rotational motion around the center of gravity of a vehicle traveling at a side slip angle β and a vehicle speed V is expressed by the following equation using a two-wheel model.
Iφ ′ = − 2L _f K _f (β + L _f φ / V−δ) + 2L _r K _r (β−L _r φ / V) (3)
Here, each symbol represents the following parameter.
I: Yaw moment of inertia of vehicle,
L _f : length from the center of gravity to the front axis,
L _r : length from the center of gravity to the rear axis,
K _f : front wheel cornering power,
K _r : rear wheel cornering power,
δ: Actual turning angle

Assuming that the yaw moment caused by the difference in the tire moving radius of the drive wheels is M, the above equation (3) becomes the following equation.
Iφ ′ = − 2L _f K _f (β + L _f φ / V−δ) + 2L _r K _r (β−L _r φ / V) + M (4)
In order for the vehicle to keep going straight, it is necessary to obtain an actual turning angle δ that cancels the influence of the yaw moment M. Therefore, φ ′ = 0 and φ = 0 are substituted into the above equation (4) to solve the actual turning angle δ.
δ = (1−L _r K _r / L _f K _f ) β−1 / L _f K _f −M (5)
If the actual turning angle δ obtained by the above equation (5) is given to the vehicle, the vehicle will go straight even if the tire moving radius of the drive wheels changes. Here, since L _f , L _r , K _f , and K _r are constants, they are held in a ROM or the like. Also, the side slip angle β is estimated based on the following equation, for example, based on the vehicle speed Vx in the front-rear direction detected by the speed sensor and the vehicle speed Vy in the lateral direction.
β = Vy / Vx (6)

Next, a method for estimating the yaw moment M will be described.
Normally, equal driving torque T is transmitted to the left and right wheels via a differential gear. Here, the driving force F generated between the tire and the ground is given by the following equation.
F = T / R (7)
Note that R is a tire moving radius.
Therefore, if there is a left / right difference in the tire dynamic radius R, a difference also occurs in the left / right driving force F, and a yaw moment M is generated. The yaw moment M generated at this time is expressed by the following equation.
M = (F _R −F _L ) / W = (T / R _R −T / R _L ) / W (8)

Here, F _R is the right wheel driving force, F _L is the left wheel drive force, R _R is the right wheel tire dynamic radius, R _L is the left wheel tire's dynamic radius, W is the tread. Since the tread W is a constant, it is stored in a ROM or the like.
The driving torque T is estimated based on the vehicle speed V and the shift position with reference to the driving torque estimation map shown in FIG. The driving torque T can also be estimated from the vehicle speed V using the hyperbola shown by the broken line in FIG. At this time, the vehicle speed-driving torque characteristic is processed into a driving torque T for one wheel in the case of two-wheel driving, and for two wheels in the case of four-wheel driving.

Next, a method for estimating the tire moving radii R _R and R _L of the left and right wheels will be described.
Before implementing this motion algorithm, the “corresponding to the difference in the dynamic radius” is either “each wheel speed when traveling straight” or “the average of the wheel speeds of the left front and rear wheels and the wheel speed of the right front and rear wheels when traveling straight. "Average" is estimated by statistical processing. These are combined with a vehicle driving method (two-wheel drive, four-wheel drive) to estimate tire dynamic radii R _R and R _L for the left and right wheels.

In the case of two-wheel drive, when using the average of the four wheel speeds when traveling straight, the tire moving radii R _R and R _L of the left and right wheels are estimated using the following equations (9) and (10).
R _R = (design value of tire dynamic radius) × (average of wheel speeds during straight traveling) / (right driving wheel for wheel speeds during straight traveling) (9)
R _L = (design value of the tire's dynamic radius) × (average of four wheels fraction of the wheel speed during straight ahead) / (the left driving wheel portion of the wheel speed during straight) ......... (10)

Further, in the case of two-wheel drive, when using the average of the driven wheel of the wheel speed when traveling straight, tire dynamic radii R _R and R _L of the left and right wheels are estimated using the following equations (11) and (12).
R _R = (design value of the tire dynamic radius) × (average of the driven wheel of the wheel speed when going straight) / (for the right drive wheel of the wheel speed when going straight) ………… (11)
R _L = (design value of the tire's dynamic radius) × (average driven wheel portion of the wheel speed during straight ahead) / (the left driving wheel portion of the wheel speed during straight) ......... (12)

On the other hand, in the case of four-wheel drive, the tire moving radii R _R and R _L of the left and right wheels are estimated using the following equations (13) and (14).
R _R = (design value of tire dynamic radius) × (average of four wheel speeds when driving straight) / (average of front and rear right driving wheels of wheel speed when driving straight) (13)
R _L = (design value of tire dynamic radius) × (average of four wheel speeds when traveling straight) / (average of front and rear left driving wheels of wheel speed when traveling straight) (14)
Thus far, the actual turning angle δ that cancels the influence of the yaw moment M is obtained. The torque increase / decrease ΔT for generating the actual turning angle δ is determined with reference to the torque increase / decrease calculation map shown in FIG.

The characteristic line shown in FIG. 10 is obtained from the characteristics of the self-aligning torque of the tire. The characteristics of the self-aligning torque depend on the friction coefficient μ and the vehicle weight, but here, the torque increase / decrease ΔT is set to a relatively small value for low μ and low vehicle weight.
Since what is actually used in the control is mainly the linear region in the characteristic line of FIG. 10, the torque increase / decrease ΔT may be calculated by calculation.

FIG. 11 is a flowchart showing the torque increase / decrease calculation processing procedure executed in step S42 of FIG.
First, in step S421, various information is acquired. Here, the yaw inertia moment I of the vehicle held in the ROM or the like, the length L _f from the center of gravity to the front shaft, the length L _r from the center of gravity to the rear shaft, the front wheel cornering power K _f , the rear wheel cornering power K _r , The design values of the tread W and the tire moving radius are read out. Further, the vehicle speed Vx in the front-rear direction and the vehicle speed Vy in the lateral direction detected by the speed sensor are acquired, and the shift position is acquired.

Next, in step S422, tire radii R _R and R _L are estimated using the above equations (9) to (14), and the process proceeds to step S423.
In step S423, the yaw moment M caused by the difference in tire dynamic radius is estimated using the above equation (8) and FIG.
Next, in step S424, the side slip angle β is estimated using the above equation (6), and the process proceeds to step S425.
In step S425, the actual turning angle δ that cancels the influence of the yaw moment M is estimated using the above equation (5), and the process proceeds to step S426.
In step S426, the torque increase / decrease ΔT that gives the actual turning angle δ is calculated using FIG.

Returning to FIG. 8, in step S43, the single flow suppression control unit 22 adds the torque increase / decrease ΔT calculated in step S42 to the single flow suppression torque Tb calculated in step S10 to obtain the final single flow suppression torque. calculate. Then, a motor current command value Ib for adding this final single flow suppression torque to the steering unit is calculated and output.
With such a configuration, when a difference in tire dynamic radius occurs in the drive wheels, the one-flow suppression torque Tb can be corrected so as to cancel the yaw moment M generated by the difference in tire dynamic radius.
In FIG. 8, step S41 constitutes a determination unit, and steps S42 and S43 constitute a torque correction unit.

"effect"
(9) The determination means determines whether or not a difference between the left and right wheel moving radii has occurred in the drive wheels. When the determining means determines that the difference between the left and right wheel moving radii is occurring in the drive wheels, the torque correcting means is a one-flow suppressing steering assist torque in a direction to cancel the yaw moment generated by the difference in the wheel moving radii of the driving wheels. Correct.
As a result, even if a difference in the tire moving radius of the drive wheels occurs, the single flow suppression torque can be appropriately added, and the single flow of the vehicle can be suppressed.

<< Fifth Embodiment >>
Next, a fifth embodiment of the present invention will be described.
In the fifth embodiment, when the tire moving radius is different and the wheel speed history is not sufficiently acquired, the single flow suppression control is held.
"Constitution"
The overall configuration of the vehicle steering apparatus in the fifth embodiment is the same as that of the first embodiment described above shown in FIG.

(Single flow suppression control processing procedure)
The single flow suppression control processing procedure executed by the single flow suppression control unit 22 of the fifth embodiment will be described.
FIG. 12 is a flowchart illustrating a single flow suppression control processing procedure executed by the single flow suppression control unit 22 according to the fifth embodiment. This single flow suppression control process is the same as that in FIG. 4 except that steps S51 and S52 are added to the single flow suppression control process shown in FIG. Accordingly, parts corresponding to those in FIG.

If the predetermined period has not elapsed since the start of the acquisition of the wheel speed V _i history, it is determined that the difference in tire dynamic radius cannot be calculated with high accuracy, the determination in Step S3 is No, and the process proceeds to Step S51. To do.
In step S51, pent suppression control unit 22 determines whether there is a difference in tire's dynamic radius based on the history of the wheel speed V _i are acquired at present, the process proceeds to step S52. In step S51, as in step S4, the history of the wheel speed V _i is statistically processed to determine whether there is a difference in tire dynamic radius.
In step S52, the single flow suppression control unit 22 receives the determination result of step S51 and proceeds to step S6 when determining that there is no difference in tire moving radius. On the other hand, if it is determined that there is a difference in tire moving radius, the single flow suppression control process is terminated as it is.

  With such a configuration, when the wheel speed history is sufficiently acquired, the wheel speed history is statistically processed to calculate the difference in tire dynamic radius, and the wheel speed is corrected based on the result. On the other hand, if it is determined that there is no difference in tire radius when the wheel speed history is not sufficiently acquired, the wheel speed is not corrected and the yaw rate is estimated by using the wheel speed detection value as it is. Implement suppression control. In addition, when it is determined that there is a difference in tire dynamic radius when the wheel speed history is not sufficiently acquired, the pinion torque history is not updated and the one-flow suppression torque Tb calculated in the previous control cycle is not performed. Is added as it is, that is, the single flow suppression control is set to the hold state.

Thus, until obtaining sufficiently the history of the wheel speed V _i can also be suppressed sided flow of the vehicle. In addition, when the tire dynamic radius difference suddenly occurs before sufficiently acquiring the history of the wheel speed V _i , the single flow suppression control can be held, and therefore the single flow suppression control is performed. Therefore, it is possible to prevent the single flow of the vehicle from being promoted.

"effect"
(10) The error estimation means estimates an error caused by a difference between the left and right wheel moving radii based on the history acquired for a predetermined period. The difference determining means determines whether or not there is a difference between the left and right wheel moving radii based on the acquired history until a predetermined period elapses from the start of history acquisition.
The single flow suppression control unit sets the holding state in which the update of the control amount of the single flow suppression control is stopped when the difference determination unit determines that there is a difference between the left and right wheel moving radii. The yaw rate estimation means calculates the yaw rate of the vehicle directly from the wheel speed detected by the wheel speed detection means when the difference determination means determines that there is no difference between the left and right wheel moving radii.
Thereby, it is possible to perform appropriate one-sided flow suppression control from the start of the acquisition of the wheel speed history to the acquisition of the history sufficiently.

<< Sixth Embodiment >>
Next, a sixth embodiment of the present invention will be described.
In the sixth embodiment, an estimation error of a yaw rate generated due to a difference in tire moving radius is calculated, and the straight error determination is performed by correcting the error.
"Constitution"
The overall configuration of the vehicle steering apparatus in the sixth embodiment is the same as that of the first embodiment described above shown in FIG.
FIG. 13 is a block diagram illustrating a configuration of the controller 11 according to the sixth embodiment.
The controller 11 of the sixth embodiment replaces the wheel speed history storage unit 224, dynamic radius difference calculation unit 225, wheel speed correction unit 226, and yaw rate calculation unit 227 of FIG. 2 with a yaw rate estimation unit 229 and yaw rate history storage. Unit 230, yaw rate deviation calculation unit 231, and yaw rate correction unit 232.

The yaw rate estimation unit 229 estimates the yaw rate φ based on the wheel speeds V _{FL to} V _RR detected by the wheel speed sensors 16FL to 16RR. The estimated yaw rate φ is output to the yaw rate history storage unit 230 and the yaw rate correction unit 232.
The yaw rate history storage unit 230 records the history of the yaw rate φ estimated by the yaw rate estimation unit 229.
The yaw rate deviation calculation unit 231 acquires the yaw rate history recorded by the yaw rate history recording unit 230, and calculates the deviation of the yaw rate φ (estimated error of the yaw rate φ caused by the difference in tire dynamic radius) by statistical processing.
The yaw rate correction unit 232 corrects the deviation of the yaw rate φ estimated by the yaw rate estimation unit 229, and outputs the corrected yaw rate φ to the straight travel determination unit 228.

(Single flow suppression control processing procedure)
The single flow suppression control processing procedure executed by the single flow suppression control unit 22 of the sixth embodiment will be described.
FIG. 14 is a flowchart illustrating a single flow suppression control processing procedure executed by the single flow suppression control unit 22 according to the sixth embodiment. This single flow suppression control process is the same as that of FIG. 4 except that steps S2 to S7 are replaced with steps S61 to S66 in the single flow suppression control process shown in FIG. Accordingly, parts corresponding to those in FIG.

In step S61, the single flow suppression control unit 22 estimates the yaw rate φ based on the formula (2) based on the wheel speeds V _{FL to} V _RR detected by the wheel speed sensors 16FL to 16RR.
Next, in step S62, the single flow suppression control unit 22 records the yaw rate φ estimated in step S61 as a history, and proceeds to step S63.
In step S63, the single flow suppression control unit 22 determines whether or not a sufficient history of the yaw rate φ has been acquired. Here, when the history is acquired for a predetermined period (for example, 30 minutes), it is determined that the history of the yaw rate φ is sufficiently acquired, and the process proceeds to step S64. On the other hand, when it is determined that the history of the yaw rate φ is not sufficiently acquired, the process proceeds to step S66 described later.

In step S64, the single flow suppression control unit 22 statistically processes the history of the yaw rate φ, and calculates the deviation of the estimated value of the yaw rate φ due to the difference in tire dynamic radius. Here, the average value of the history of the yaw rate φ is calculated, and this is taken as the deviation of the estimated value of the yaw rate φ.
When the vehicle is traveling straight ahead, the yaw rate is theoretically zero. Therefore, the value calculated in step S64 becomes the estimation error of the yaw rate φ as it is.
Next, in step S65, the single flow suppression control unit 22 corrects the yaw rate φ estimated in step S61 using the deviation of the yaw rate φ calculated in step S64. At this time, correction is always performed by subtracting the deviation calculated in step S64 from the yaw rate φ estimated in step S61.

Next, in step S66, the single flow suppression control unit 22 determines whether or not the absolute value | φ | of the yaw rate φ corrected in step S65 is less than the yaw rate threshold φth. When | φ | <φth, the process proceeds to step S8. When | φ | ≧ φth, the process proceeds to step S11.
With such a configuration, even when a deviation occurs in the estimated value of the yaw rate φ due to a difference in the tire moving radius, it is possible to correct the deviation and appropriately determine whether to go straight.
In FIG. 14, step S61 constitutes the yaw rate calculation means, steps S62 to S64 constitute error estimation means, and step S65 constitutes error correction means.

"effect"
(11) The yaw rate calculation means calculates the yaw rate of the vehicle based on the wheel speed detected by the wheel speed detection means. The error estimation unit estimates an error of the yaw rate calculation value as an error caused by a difference between the left and right wheel moving radii based on the yaw rate history calculated by the yaw rate calculation unit. The error correction unit corrects the error of the yaw rate calculation value estimated by the error estimation unit.
As a result, even if a difference in tire moving radius occurs, it is possible to perform appropriate one-sided flow suppression control without erroneously making a straight-ahead determination.
(12) The error estimation means sets the average value of the yaw rate history calculated by the yaw rate calculation means as the error of the yaw rate calculation value.
Thereby, it is possible to correct an error in the calculated yaw rate caused by the difference between the left and right wheel moving radii. As a result, it is possible to appropriately determine whether the vehicle is going straight.

<Modification>
(1) In the first, third, and fourth embodiments, when it is determined No in step S3 of FIGS. 4, 7, and 8, the single flow suppression control process can be ended as it is. Thereby, after acquiring the wheel speed history sufficiently and correcting the deviation of the wheel speed caused by the difference in the tire moving radius, the single flow suppression control can be started.
Similarly, in the sixth embodiment, when it is determined No in step S63 of FIG. 14, the single flow suppression control process can be ended as it is. Thus, after the yaw rate history is sufficiently acquired and the deviation of the yaw rate caused by the difference in the tire moving radius is corrected, the single flow suppression control can be started.

As described above, since the single flow suppression control is maintained until the history is sufficiently acquired, it is possible to prevent the single flow suppression control from being performed using the wheel speed before correction and the yaw rate before correction. Further, it is possible to prevent a single flow of the vehicle from being promoted.
In addition, when INGOFF is set in a state where the tire moving radius is different, it is considered that the tire moving radius is not changed due to tire replacement or the like during IGN OFF. Therefore, until the history is sufficiently acquired, instead of taking over the difference in the tire dynamic radius at the time of the previous INGOFF and carrying out the single flow suppression control, the single flow suppression control is maintained and the generation of the single flow is prevented. Can be prevented.

  (2) In the sixth embodiment, as in the second embodiment, it is also possible to store a difference in tire dynamic radius at the time of INGOFF (estimated error in yaw rate). Further, as in the third embodiment, a function of selecting the wheel speed can be provided. Furthermore, when the tire moving radius is generated in the drive wheel as in the fourth embodiment, the one-way flow suppression torque Tb can be corrected to increase or decrease. Further, as in the fifth embodiment, when the history is not sufficiently acquired, when it is determined that there is a difference in the tire moving radius based on the history acquired at the present time, the single flow suppression control is set to the holding state. You can also.

  (3) In each of the above embodiments, the case where the pinion torque estimating unit 221 estimates the pinion torque Tp based on the steering torque T and the motor current Im has been described. However, the current command value correction is performed instead of the motor current Im. The current command value I output from the unit 23 can also be used. In this case, it is not necessary to provide the motor current sensor 15, and the cost can be reduced accordingly.

(4) In each of the above embodiments, an example of front wheel steering assist using EPS (electric power steering) has been described. However, vehicle steering such as DYC using braking / driving force, left and right independent control of each wheel, and rear wheel steering is performed. It can be applied to other possible systems.
(5) In each of the above embodiments, the case where the present invention is applied to a system in which a steering unit and a steered unit are mechanically connected has been described. However, for example, the present invention may be applied to a steer-by-wire system. it can. In this case, a steering reaction force corresponding to the single flow suppression steering assist torque calculated based on the steering torque history in the straight traveling state is applied to the steering unit.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Front wheel 3 Steering mechanism 4 Steering shaft 5 Torque sensor 6 Reducer 7 Motor 8 Pinion 9 Rack 10 Tie rod 11 Controller 13 Vehicle speed sensor 15 Motor current sensor 16FL-16RR Wheel speed sensor

Claims (13)

Wheel speed detection means for detecting the wheel speed of each wheel;
Based on the wheel speed of each wheel detected by the wheel speed detection means, the yaw rate estimation means for estimating the yaw rate of the vehicle corrected for the error caused by the difference between the left and right wheel moving radii;
Based on the yaw rate estimated by the yaw rate estimating means, straight running state determining means for determining whether or not the vehicle is in a straight traveling state;
Steered torque detecting means for detecting the steered torque of the steered portion that steers steered wheels;
One-flow suppression steering assist that cancels the turning torque during straight running based on the history of turning torque detected by the turning torque detection means when the straight running state determination means determines that the vehicle is in a straight running state A vehicle steering apparatus comprising: single flow suppression control means for performing single flow suppression control for adding torque to a steering unit. The yaw rate estimation means includes
Based on the wheel speed history detected by the wheel speed detection means, an error estimation means for estimating an error of the wheel speed detection value as an error caused by a difference between the left and right wheel moving radii;
Error correction means for correcting an error of the wheel speed detection value estimated by the error estimation means;
Yaw rate calculation means for calculating the yaw rate of the vehicle based on the wheel speed corrected by the error correction means,
2. The vehicle steering apparatus according to claim 1, wherein the yaw rate calculated by the yaw rate calculation unit is a yaw rate in which an error caused by a difference between left and right wheel moving radii is corrected. The yaw rate estimation means includes
A yaw rate calculating means for calculating a yaw rate of the vehicle based on the wheel speed detected by the wheel speed detecting means;
Based on the yaw rate history calculated by the yaw rate calculating means, an error estimating means for estimating an error of the yaw rate calculated value as an error caused by a difference between the left and right wheel moving radii;
Error correction means for correcting an error in the yaw rate calculated value estimated by the error estimation means,
2. The vehicle steering apparatus according to claim 1, wherein the yaw rate corrected by the error correction means is a yaw rate in which an error caused by a difference between the left and right wheel radii is corrected.   The error estimation means calculates an average value of the wheel speed of the right wheel and an average value of the wheel speed of the left wheel based on the wheel speed history detected by the wheel speed detection means, and calculates a difference between these average values. The vehicle steering apparatus according to claim 2, wherein an error of a wheel speed detection value is used.   The error estimation means calculates the average value of the wheel speed of the right wheel and the average value of the wheel speed of the left wheel based on the wheel speed history detected by the wheel speed detection means, and calculates the ratio of these average values. The vehicle steering apparatus according to claim 2, wherein an error of a wheel speed detection value is used.   The vehicle steering apparatus according to claim 3, wherein the error estimation unit sets an average value of the yaw rate history calculated by the yaw rate calculation unit as an error of the yaw rate calculation value. The error estimation means is for estimating an error caused by a difference between left and right wheel moving radii based on the history acquired for a predetermined period,
The yaw rate estimation means directly calculates the yaw rate of the vehicle from the wheel speed detected by the wheel speed detection means until the predetermined period elapses from the start of acquisition of the history. The vehicle steering device according to any one of the above. The error estimation means is for estimating an error caused by a difference between left and right wheel moving radii based on the history acquired for a predetermined period,
The said single flow suppression control means is made into the holding | maintenance state which stops the update of the control amount of the said single flow suppression control until the said predetermined period passes since the acquisition start of the said log | history. The vehicle steering device according to any one of the preceding claims. The error estimation means is for estimating an error caused by a difference between left and right wheel moving radii based on the history acquired for a predetermined period,
Storage means for storing an error caused by a difference between the left and right wheel moving radii estimated by the error estimation means when the ignition switch transits from an on state to an off state;
3. The error correction unit corrects an error caused by a difference between left and right wheel moving radii stored in the storage unit from the start of acquisition of the history until the predetermined period elapses. The vehicle steering device according to any one of? 6. The error estimation means is for estimating an error caused by a difference between left and right wheel moving radii based on the history acquired for a predetermined period,
A difference determining means for determining whether or not a difference has occurred in the left and right wheel moving radii based on the acquired history from the start of acquiring the history until the predetermined period elapses;
When the single flow suppression control means determines that a difference has occurred between the left and right wheel moving radii in the difference determination means, the single flow suppression control means enters a holding state in which updating of the control amount of the single flow suppression control is stopped,
The yaw rate estimating means calculates the yaw rate of the vehicle directly from the wheel speed detected by the wheel speed detecting means when the difference determining means determines that there is no difference between the left and right wheel moving radii. The vehicle steering apparatus according to any one of claims 2 to 6. A sorting means for sorting the wheel speed detected by the wheel speed detecting means;
11. The vehicle steering apparatus according to claim 1, wherein the yaw rate estimation unit estimates a yaw rate of the vehicle based on a wheel speed that satisfies a selection condition of the selection unit. Determining means for determining whether or not a difference between the left and right wheel moving radii has occurred in the drive wheel;
When the determination means determines that the difference between the left and right wheel moving radii is occurring in the drive wheels, the one-flow suppression steering assist torque is corrected in a direction to cancel out the yaw moment generated by the difference in the wheel moving radii of the driving wheels. The vehicle steering apparatus according to claim 1, further comprising: a torque correction unit.   Based on the wheel speed of each wheel, the yaw rate of the vehicle is corrected by correcting the error caused by the difference between the left and right wheel radii, and based on the estimated yaw rate, it is determined whether the vehicle is running straight. Based on the history of steering torque generated in the steering unit when it is determined that the vehicle is traveling straight, a single-flow suppression steering assist torque that cancels the steering torque during straight traveling is added to the steering unit. A vehicle steering method characterized by performing single flow suppression control.

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