JP2010132205A - Vehicular steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular steering device for accurately detecting a tire nonlinear region, and simulating a steering reaction force characteristic of a conventional steering device. <P>SOLUTION: A controller 15 generates a target steering reaction force Th depending on only a tire lateral force Fy in a linear region wherein the tire lateral force Fy linearly changes with respect to a tire slip angle β. The controller 15 reduces a steering reaction force depending on the tire lateral force Fy of the target steering reaction force Th as the tire lateral force Fy becomes larger in the nonlinear region wherein the tire lateral force Fy nonlinearly changes with respect to the tire slip angle β, and increases the steering reaction force depending on a steering axial force Fr. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a so-called steer-by-wire vehicle steering apparatus in which a steering wheel and a steering mechanism that steers a steered wheel are mechanically separated.

There is a so-called steer-by-wire steering device that mechanically separates (separates) the steering wheel from the steering wheel that steers the steered wheel and drives the steered wheel by the steering mechanism based on the steering angle of the steering wheel. Are known. In such a steer-by-wire type steering device, since the steering reaction force is not directly transmitted to the steering wheel, the steering reaction force characteristic of a conventional steering device in which the steering wheel and the steering mechanism are mechanically connected is generally used. Is provided with a reaction force motor (steering reaction force applying means) for applying a steering reaction force to the steering wheel. However, in a steer-by-wire steering system equipped with such a reaction force motor, the driver recognizes that the steered wheels (tires) are at the turning limit (also called the grip limit) as a reduction in the steering reaction force. It is difficult to let
Then, when the vehicle reaches the turning limit, it is considered to inform the driver of the turning limit of the tire by applying the technique described in Patent Document 1 that intentionally reduces the steering reaction force.
JP 2000-264237 A

  However, in the technique described in Patent Document 1, the tire reaction limit is determined by using the estimated values of the road surface μ and the tire slip angle to reduce the steering reaction force. However, the road surface μ and the tire slip angle are accurately determined. Therefore, it is difficult to accurately estimate the turning limit of the tire by the steering reaction force to the driver.

  An object of the present invention is to provide a vehicle steering apparatus that can more accurately simulate the steering reaction force characteristic of a conventional steering apparatus and can accurately transmit the turning limit of the tire to the driver by the steering reaction force. is there.

  In order to achieve the above-described object, the present invention detects tire lateral force and turning axial force, generates a target steering reaction force according to the detected tire lateral force and turning axial force, In the linear region where the tire linearly changes with respect to the tire slip angle, the target steering reaction force is generated only according to the tire lateral force, and in the nonlinear region where the tire lateral force changes nonlinearly with respect to the tire slip angle, As the force increases, the steering reaction force corresponding to the tire lateral force is reduced among the target steering reaction force, while the steering reaction force corresponding to the turning axial force is increased.

  Therefore, in the present invention, in the linear region where the tire lateral force changes linearly with respect to the tire slip angle based on the actual tire lateral force and the turning axial force, the target steering is performed according to only the tire lateral force. In the tire non-linear region, the steering force and steering are reduced in order to reduce the steering reaction force according to the tire lateral force and to increase the steering reaction force according to the turning axial force. It is possible to more accurately simulate the steering reaction force characteristic of a conventional steering device mechanically connected to the mechanism, and to accurately transmit the turning limit of the tire to the driver by the steering reaction force.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

First, the configuration will be described.
FIG. 1 is an overall configuration diagram of a steer-by-wire system to which a vehicle steering apparatus according to a first embodiment is applied. The vehicle steering apparatus according to the first embodiment includes a handle 1 and front wheels (steered wheels) 2 and 2. This is a so-called steer-by-wire (SBW) system in which the steering mechanism 3 that steers is mechanically separated.

  A column shaft 4 that supports the handle 1 includes a reaction force motor (steering reaction force applying means) 5 that applies a steering reaction force to the handle 1, a rotation angle sensor 6 that detects a rotation angle of the column shaft 4, and a column shaft. A steering torque sensor 7 that detects a steering torque from a torsion angle of a torsion bar provided at 4 and a reaction force motor angle sensor 8 that detects a rotation angle of the reaction force motor 5 are provided.

  The steering mechanism 3 includes first and second steering motors 9a and 9b for applying a steering torque for turning the front wheels 2 and 2 to the pinion gears 13a and 13b, and rotation angles of the front wheels 2 and 2 from a straight traveling state. The first and second turning motor angle sensors 10a and 10b for detecting the rotation angles of the first and second turning motors 9a and 9b are provided as turning angles. The first steering motor 9a is mechanically connected to the front wheels 2 and 2 via the rack 11 and the pinion gear 13a, and the second steering motor 9b is mechanically connected to the front wheels 2 and 2 via the pinion gear 13b. The turning angle of the front wheels 2 and 2 can be detected by detecting the rotation angle of the second turning motors 9a and 9b.

  The hub portion (not shown) of the front wheels 2, 2 has a first force that detects lateral force acting on the tires of the front wheels 2, 2 (in the following description, the tire is the tire of the front wheels 2, 2). , Second tire lateral force sensors (tire lateral force detecting means) 12a, 12b are provided. “Lateral force (side force, lateral force)” refers to a component that acts at right angles to the center surface of the tire among frictional forces generated on the contact surface when the tire turns with a certain slip angle. “Slip angle (side slip angle)” refers to an angle formed by the traveling direction of the tire and the direction of the tire center plane when the tire in a turning state is viewed from above.

The reaction force motor 5 and the first and second steering motors 9a and 9b are controlled by first, second and third controllers (steering reaction force control means) 14, 15 and 16, respectively.
The second controller 15 includes a column shaft rotation angle from the rotation angle sensor 6, a steering torque from the steering torque sensor 7, a reaction force motor angle from the reaction force motor angle sensor 8, and the first and second tire sideways. The tire lateral force from the force sensors 12a and 12b is input. In addition, vehicle information such as wheel speed is input to the second controller 15 via a CAN communication line (not shown).

The second controller 15 generates the target turning angle of the front wheels 2 and 2 based on the reaction force motor angle (that is, the steering angle) from the reaction force motor angle sensor 8 and the vehicle speed from the CAN communication line. 3 Send to controller 14,16. The first controller 14 generates a command current that eliminates the deviation between the target turning angle sent from the second controller 15 and the actual turning angle of the front wheels 2 and 2 detected by the first turning motor angle sensor 10a. 1 Output to the steered motor 9a to control the steered angle. The third controller 16 outputs a command current that eliminates the deviation between the target turning angle sent from the second controller 15 and the actual turning angle of the front wheels 2 and 2 detected by the second turning motor angle sensor 10b. 2 Output to the steered motor 9b to control the steered angle.
In the present embodiment, the reaction force motor angle from the reaction force motor angle sensor 8 is used as the steering angle of the handle 1, but the column shaft rotation angle from the rotation angle sensor 6 may be used as the steering angle.

  Further, the second controller 15 is configured to calculate the steering angular velocity of the steering wheel 1 calculated from the reaction force motor angle from the reaction force motor angle sensor 8, the tire lateral force from the first and second tire lateral force sensors 12a and 12b, A target steering reaction force to be applied to the steering wheel 1 is generated based on the current values of the first and second steering motors 9a and 9b and the vehicle speed from the CAN communication line, and the target current and the reaction force motor based on the target steering reaction force are generated. A command current that eliminates the deviation from the actual current detected by a current sensor (not shown) that detects the current supplied to 5 is output to the reaction force motor 5 to control the steering reaction force.

  The first, second, and third controllers 14, 15, and 16 operate by receiving power from the battery 17. The first, second, and third controllers 14, 15, and 16 share input / output information with each other via the communication line 18, and even if a failure occurs in the second controller 15, the remaining The first and third controllers 14 and 16 generate the target turning angle and the target steering reaction force, and the first and second steering motors 9a and 9b and the two first and third controllers 14 and 16 Control of the reaction force motor 5 can be continued.

  [N1]

  Hereinafter, for the sake of simplicity, the first and second steered motors 9a and 9b are referred to as the steered motor 9 and the first and second steered motor angle sensors 10a, unless it is necessary to explain each separately. The steering motor angle sensor 10b, the first and second tire lateral force sensors 12a and 12b are referred to as the tire lateral force sensor 12, and the first, second and third controllers 14, 15 and 16 are referred to as the controller 15. That is, description will be made assuming that the steered motor 9, the steered motor angle sensor 10, the tire lateral force sensor 12, and the controller 15 are one.

Next, a method for generating the target steering reaction force by the controller 15 will be described.
In the first embodiment, from the actual tire lateral force Fy detected by the tire lateral force sensor 12 and the turning axial force Fr calculated from the current value of the turning motor 9 (force acting in the axial direction of the rack 11). The target steering reaction force Th is generated with reference to the following equation. The turning axial force Fr is calculated by converting the current value of the turning motor 9 into the output torque of the turning motor 9 (the total output torque value of the turning motors 9a and 9b) (the turning axial force detecting means).
Th = K1 × Fr + K2 × Fy
Here, K1 is a turning axial force gain, and K2 is a turning axial force gain. These two gains K1 and K2 are determined with reference to the map shown in FIG. 2 according to the tire lateral force Fy detected by the tire lateral force sensor 12.

  FIG. 2 is a setting map of the tire lateral force gain K1 and the turning axial force gain K2 of the first embodiment. The tire lateral force gain K1 is a constant value when the tire lateral force Fy is equal to or less than the first threshold value Fy1, and the tire lateral force Fy is equal when the tire lateral force Fy is between the first threshold value Fy1 and the second threshold value Fy2. Has a characteristic that the tire lateral force Fy becomes constant in a region where the tire lateral force Fy exceeds the second threshold value Fy2.

  On the other hand, the steered axial force gain K2 is zero when the tire lateral force Fy is equal to or less than the first threshold value Fy1, and the tire lateral force Fy is equal to the tire lateral force when the tire lateral force Fy is between the first threshold value Fy1 and the second threshold value Fy2. The larger Fy is, the larger the tire lateral force Fy becomes in a region where the second threshold value Fy2 is exceeded.

Next, the first threshold value Fy1 and the second threshold value Fy2 will be described.
As shown in FIG. 3, the first threshold value Fy1 is the maximum value of the tire lateral force in a linear region in which the tire lateral force Fy changes linearly with respect to the tire slip angle β. The second threshold value Fy2 is within a non-linear region where the tire lateral force Fy changes nonlinearly with respect to the tire slip angle β, and the saturated value of the tire lateral force Fy (when the tire lateral force Fy becomes substantially constant). Value).
Since the first threshold value Fy1 and the second threshold value Fy2 are values determined by the specifications of the tire, they are obtained and stored in advance through experiments or the like.

Next, the operation will be described.
(Reaction force generation in tire linear region)
When the steering wheel 1 is operated, the turning axial force input in the axial direction of the rack 11 from the front wheels 2 and 2 is the self-aligning torque SAT, the tire lateral force Fy × the caster rail (more precisely, each is a cos (caster angle)) The moment is applied around the kingpin. “Cast rail” refers to the angle between the kingpin axis and the vertical direction when the tire is viewed from the side.

  Here, the self-aligning torque SAT is tire lateral force Fy × pneumatic trail. A “pneumatic trail” is a tire that rolls with a slip angle β, and a straight line connecting the point of application of the tire lateral force Fy and the ground contact center of the tire is the direction of tire travel or tire orientation. This is the distance when projected onto a vertical plane parallel to.

  As shown in FIG. 3, in the tire linear region where the tire lateral force Fy is smaller than the first threshold value Fy1, the tire lateral force Fy and the self-aligning torque SAT change linearly with respect to the tire slip angle β. Therefore, in the tire linear region, it can be said that the turning axial force Fr is a value whose magnitude is determined in proportion to the tire lateral force Fy. The turning axial force Fr includes the reaction force corresponding to the viscosity and inertia of the steering system, but it is negligible because it is very small compared to the reaction force corresponding to the tire lateral force Fy. is there.

  In the steering device of the first embodiment, the target steering reaction force Th is generated according to the tire lateral force Fy and the turning axial force Fr, and in the linear region where the tire lateral force Fy linearly changes with respect to the tire slip angle β. A value obtained by multiplying the tire lateral force Fy by the tire lateral force gain K1 is defined as a target steering reaction force Th. That is, the target steering reaction force Th is generated only according to the tire lateral force Fy measured by the tire lateral force sensor 12.

  By the way, in Example 1, although the steered axial force Fr is calculated by converting the current value of the steered motor 9 into the output torque, the linearity is inferior to the tire lateral force Fy. For some reason, the error is large with respect to the actual change characteristic of the turning axial force. On the other hand, the tire lateral force Fy actually detected by the tire lateral force sensor 12 is closer to the actual turning axial force change characteristic than the estimated turning axial force Fr.

  Therefore, in the tire linear region, by generating the target steering reaction force Th based only on the tire lateral force Fy detected by the tire lateral force sensor 12, the steering reaction force that matches the actual change characteristic of the turning axial force is obtained. It can be given to the handle 1. That is, it is possible to accurately simulate the steering reaction force characteristic of the conventional steering device in which the steering wheel and the steering mechanism are mechanically connected.

  In the first embodiment, since the tire lateral force sensor 12 is provided to detect the actual tire lateral force Fy, it is accurately determined whether the tire lateral force Fy is in the tire linear region or the tire nonlinear region. It can be detected.

(Reaction generation in tire non-linear region)
In the tire non-linear region where the tire lateral force Fy is equal to or greater than the first threshold Fy1 (ie, the region beyond the tire turning limit), the tire lateral force Fy does not increase in proportion to the tire slip angle β, unlike the tire linear region. Saturates at a certain value (second threshold Fy2). Further, the self-aligning torque SAT is sharply decreased from the first threshold value Fy1 in the tire nonlinear region while the tire lateral force Fy is increased from the first threshold value Fy1 to the second threshold value Fy2 in the tire nonlinear region. This is because the pneumatic trail moves to the front side of the vehicle when the tire lateral force Fy is equal to or greater than the first threshold value Fy1.

  For this reason, the actual turning axial force is not a value according to the tire lateral force Fy, for example, when the target steering reaction force Th is generated only according to the tire lateral force Fy as in the tire linear region, Steering reaction force can not simulate the decrease of the self-aligning torque SAT and the driver (driver) has the tire lateral force Fy in the tire nonlinear range, that is, the tire is at or near the turning limit. Cannot be notified. That is, when the target steering reaction force Th is generated only according to the tire lateral force Fy, it becomes difficult for the driver of the vehicle to detect that the tire is at the turning limit or near the turning limit based on the steering reaction force.

  On the other hand, in the steering device of the first embodiment, the tire lateral force Fy increases in a non-linear region where the tire lateral force Fy changes nonlinearly with respect to the tire slip angle β (region where the tire lateral force becomes Fy1 or more). Of the target steering reaction force Th, the steering reaction force (K1 × Fy) corresponding to the tire lateral force Fy is reduced, while the steering reaction force (K2 × Fr) corresponding to the turning axial force Fr is increased.

  That is, since the decrease in the self-aligning torque SAT in the tire non-linear region is reflected in the turning axial force Fr calculated from the current value of the turning motor 9, the reaction force corresponding to the turning axial force Fr is increased. Thus, it is possible to simulate the steering reaction force characteristic of a conventional steering device in which the steering reaction force decreases with a sudden decrease in the self-aligning torque SAT, and to inform the driver that the tire lateral force Fy is in the tire nonlinear region.

  In the steering device of the first embodiment, when the tire lateral force Fy is equal to or greater than the second threshold Fy2, that is, when the tire lateral force Fy is saturated, the tire lateral force gain K1 and the turning axial force gain K2 are fixed, and the tire lateral force is fixed. The steering reaction force (K1 × Fy) corresponding to the force Fy and the steering reaction force (K2 × Fr) corresponding to the turning shaft force Fr are made constant.

  The self-aligning torque SAT decreases as the tire lateral force Fy exceeds the first threshold Fy1, and decreases as the tire slip angle β increases. Depending on the tire characteristics, the self-aligning torque SAT is negative when the tire lateral force Fy exceeds the second threshold Fy2. May be the value of. At this time, the steering reaction force according to the turning axial force Fr becomes a negative value. On the other hand, since the tire lateral force Fy is saturated and constant above the second threshold Fy2, the steering reaction force according to the tire lateral force Fy does not change.

  That is, in the region where the tire lateral force Fy is equal to or greater than the second threshold value Fy2, the steering motor 9 is driven in a direction in which the target steering reaction force Th is a negative value, that is, the steering wheel 1 is further increased, and the vehicle is more unstable. There is a possibility.

  Therefore, in the first embodiment, when the tire lateral force Fy is equal to or greater than the second threshold value Fy2, the steering motor 9 is driven in the direction in which the steering wheel 1 is increased by keeping the target steering reaction force Th constant. This can prevent the vehicle from becoming more unstable.

Next, the effect will be described.
The vehicle steering apparatus according to the first embodiment has the following effects.
(1) The steering wheel 1 that is steered by the driver and the steering mechanism 3 that is connected to the front wheels 2 and 2 and that drives the front wheels 2 and 2 are mechanically separated from each other. In the vehicle steering apparatus having the reaction force motor 5 that drives the front wheels 2 and 2 by the steering mechanism 3 and applies a steering reaction force to the steering wheel 1, the first and second tire lateral forces that detect the tire lateral force Fy are detected. Sensors 12a and 12b, a steering axial force detecting means (controller 15) for detecting a steering axial force Fr acting on the rack shaft 11 of the steering mechanism 3, and a steering reaction force applied to the handle 1 by the reaction force motor 5 A target steering reaction force Th that is a target value is generated according to the tire lateral force and the turning axial force, and a controller 15 that controls the reaction force motor 5 based on the generated target steering reaction force Th is provided, The controller 15 In the linear region where the lateral force Fy changes linearly with respect to the tire slip angle β, the target steering reaction force Th is generated only according to the tire lateral force Fy, and the tire lateral force Fy is nonlinear with respect to the tire slip angle β. In the non-linear region that changes with time, the larger the tire lateral force Fy, the smaller the steering reaction force corresponding to the tire lateral force Fy out of the target steering reaction force Th, while the steering reaction force corresponding to the turning axial force Fr is increased. . Thereby, the steering reaction force characteristic of a conventional steering device can be simulated more accurately.

  (2) When the tire lateral force Fy is saturated, the controller 15 saturates the steering reaction force according to the tire lateral force Fy and the target steering reaction force Th according to the turning axial force Fr, and the tire lateral force Fy is saturated. In order to maintain the target steering reaction force Th at that time, the target steering reaction force Th becomes a negative value, preventing the steering motor 9 from being driven in a direction to increase the steering wheel 1, and the vehicle becomes more unstable. Can be prevented.

  The vehicle steering apparatus according to the second embodiment is different from the first embodiment only in the setting method of the tire lateral force gain K1 and the turning axial force gain K2, and the other configurations are the same, so the illustration and description of the same parts are omitted. .

  FIG. 4 is a setting map of the tire lateral force gain K1 and the turning axial force gain K2 of the second embodiment. The tire lateral force gain K1 is a constant value in a region where Fy> SAT, in which the absolute value | Fy−Fr | of the difference between the tire lateral force Fy and the turning axial force Fr is equal to or smaller than the first threshold value ΔF1, | Fy−Fr | becomes smaller as the tire lateral force Fy increases in the region between the first threshold ΔF1 and the second threshold ΔF2, and becomes constant in a region where | Fy−Fr | exceeds the second threshold ΔF2. Has characteristics.

  On the other hand, the turning axial force gain K2 is zero in the region where Fy> SAT, and the absolute value | Fy−Fr | of the difference between the tire lateral force Fy and the turning axial force Fr is zero in the region where the first threshold value ΔF1 or less. Yes, | Fy−Fr | increases as the tire lateral force Fy increases in the region between the first threshold ΔF1 and the second threshold ΔF2, and | Fy−Fr | is constant in the region exceeding the second threshold ΔF2. It has the characteristic which becomes.

  The first threshold value ΔF1 tends to decrease after the self-aligning torque SAT reaches the maximum value as the tire slip angle β increases in FIG. 3, and the predetermined value when the first threshold value ΔF1 becomes smaller than the lateral force Fy by a predetermined value. And That is, a value by which it can be determined that the tire lateral force Fy is a non-linear region and the self-aligning torque SAT is decreasing is obtained in advance through experiments or the like and set to the first threshold value ΔF1. The second threshold ΔF2 is an absolute value of the difference between the tire lateral force Fy and the turning axial force Fr when the tire lateral force Fy is saturated.

  In the second embodiment, the controller 15 calculates the turning angular velocity of the front wheels 2 and 2 from the amount of change in the rotation angle detected by the first and second turning motor angle sensors 10a and 10b (steering angular velocity detection). Means), the turning axial force Fr is corrected according to the turning angular velocity. The correction method is performed by applying a turning axial force correction coefficient set according to the turning angular velocity to the turning axial force Fr calculated from the current value of the turning motor 9.

  FIG. 5 is a correction map of the turning axial force correction coefficient according to the turning angular speed, and the turning axial force correction coefficient has a characteristic that decreases as the turning angular speed increases. The upper and lower limit values of the turning axial force correction coefficient are provided with limit values for avoiding the turning axial force Fr from being excessive or small.

Next, the operation will be described.
The absolute value of the difference between the tire lateral force Fy and the turning axial force Fr (self-aligning torque SAT) is greater than or equal to the first threshold value ΔF1, which means that the tire lateral force Fy is in a non-linear region and is self-aligning. This shows that the torque SAT is decreasing. Further, the fact that the absolute value of the difference between the tire lateral force Fy and the turning axial force Fr is equal to or larger than the second threshold value ΔF2 indicates that the tire lateral force Fy is saturated.

  Therefore, in the steering device according to the second embodiment, the steering reaction force characteristic of the conventional steering device in which the steering wheel and the steering mechanism are mechanically coupled can be accurately simulated in the tire nonlinear region.

  In the steering device of the second embodiment, the steered axial force Fr calculated from the current value of the steered motor 9 is corrected to decrease as the steered angular velocity increases. This is because when the turning angular velocity is high, the friction of the turning motor 9 is increased, so that the load on the turning motor 9 is increased, and the turning axial force Fr larger than the actual turning axial force is calculated. Because. That is, the difference between the tire lateral force Fy and the turning axial force Fr can be accurately calculated by correcting the turning axial force Fr to decrease as the turning angular velocity increases.

Next, the effect will be described.
The vehicle steering apparatus according to the second embodiment has the following effects.

  (3) The steering wheel 1 that is steered by the driver and the steering mechanism 3 that is connected to the front wheels 2 and 2 and drives the front wheels 2 and 2 to be steered are mechanically separated. In the vehicle steering apparatus having the reaction force motor 5 that drives the front wheels 2 and 2 by the steering mechanism 3 and applies a steering reaction force to the steering wheel 1, the first and second tire lateral forces that detect the tire lateral force Fy are detected. Sensors 12a and 12b, a steering axial force detecting means (controller 15) for detecting a steering axial force Fr acting on the rack shaft 11 of the steering mechanism 3, and a steering reaction force applied to the handle 1 by the reaction force motor 5 A target steering reaction force Th that is a target value is generated according to the tire lateral force and the turning axial force, and a controller 15 that controls the reaction force motor 5 based on the generated target steering reaction force Th is provided, The controller 15 If the absolute value of the difference between the lateral force Fy and the turning axial force Fr is a value indicating a linear region in which the tire lateral force Fy varies linearly with respect to the tire slip angle β, only the tire lateral force Fy And the absolute value of the difference is a value indicating a non-linear region in which the tire lateral force Fy changes nonlinearly with respect to the tire slip angle β, the tire lateral force Fy is The larger the value, the smaller the steering reaction force corresponding to the tire lateral force Fy in the target steering reaction force Th, while increasing the steering reaction force corresponding to the turning axial force Fr. Thereby, the tire non-linear region can be accurately detected, and the steering reaction force characteristic of the conventional steering device can be simulated.

  (4) A turning angular velocity detecting means (controller 15) for detecting the turning angular velocity of the tire is provided, and the controller 15 reduces the turning axial force Fr as the turning angular velocity is higher. The difference from the rudder axial force Fr can be calculated accurately.

[Other Examples]
Although the best mode for carrying out the present invention has been described based on the embodiments, the specific configuration of the present invention is not limited to the configurations shown in the embodiments.
For example, in the embodiment, the example in which the current value of the steered motor is converted into the output torque to calculate the steered axial force is shown, but the shaft that can directly detect the steered axial force acting on the rack shaft of the steering mechanism It is good also as a structure which provided the force sensor.
In the second embodiment, the controller 15 calculates the turning angular velocity of the front wheels 2 and 2 and applies the turning axial force correction coefficient set according to the turning angular velocity to the turning axial force Fr. Although Fr is corrected, this may be applied to the steering device described in the first embodiment.

1 is an overall chart of a steer-by-wire system to which a vehicle steering apparatus according to a first embodiment is applied. 3 is a setting map of a tire lateral force gain K1 and a turning axial force gain K2 according to the first embodiment. FIG. 6 is a characteristic diagram of tire lateral force Fy and self-aligning torque SAT with respect to tire slip angle β. 6 is a setting map of a tire lateral force gain K1 and a turning axial force gain K2 according to the second embodiment. 7 is a correction map of a turning axial force correction coefficient according to the turning angular velocity of the second embodiment.

Explanation of symbols

1 Handle 2 Front wheel 3 Steering mechanism 4 Column shaft 5 Reaction force motor (steering reaction force applying means)
6 Rotation angle sensor 7 Steering torque sensor 8 Reaction force motor angle sensor 9a, 9b Steering motor 10a, 10b Steering motor angle sensor 11 Rack 12a, 12b Tire lateral force sensor (tire lateral force detection means)
13 Pinion shaft 14 1st controller (steering reaction force control means, turning axial force detection means, turning angular velocity detection means)
15 Second controller (steering reaction force control means, turning axial force detection means, turning angular velocity detection means)
16 Third controller (steering reaction force control means, turning axial force detection means, turning angular velocity detection means)
17 Battery 18 Communication line

Claims (4)

A steering wheel steered by the driver and a steering mechanism connected to the steered wheels and driving the steered wheels are mechanically separated, and the steered wheels are steered by the steering mechanism according to the steering angle of the handle. In a vehicle steering apparatus having a steering reaction force applying means for driving and applying a steering reaction force to the steering wheel,
Tire lateral force detecting means for detecting tire lateral force;
A turning axial force detecting means for detecting a turning axial force acting on a rack shaft of the steering mechanism;
A target steering reaction force, which is a target value of the steering reaction force applied to the steering wheel by the steering reaction force applying means, is generated according to the tire lateral force and the turning axial force, and the generated target steering reaction force A steering reaction force control means for controlling the steering reaction force application means based on:
Provided,
The steering reaction force control means generates the target steering reaction force according to only the tire lateral force in a linear region where the tire lateral force changes linearly with respect to a tire slip angle, and the tire lateral force is In the non-linear region that varies nonlinearly with respect to the tire slip angle, the larger the tire lateral force, the smaller the steering reaction force corresponding to the tire lateral force out of the target steering reaction force, while depending on the turning axial force. A steering apparatus for a vehicle characterized by increasing the steering reaction force. The vehicle steering apparatus according to claim 1,
When the tire lateral force is saturated, the steering reaction force control means has saturated the tire lateral force with a steering reaction force according to the tire lateral force and a target steering reaction force according to the turning axial force. The vehicle steering apparatus is characterized in that the target steering reaction force is maintained. A steering wheel steered by the driver and a steering mechanism connected to the steered wheels and driving the steered wheels are mechanically separated, and the steered wheels are steered by the steering mechanism according to the steering angle of the handle. In a vehicle steering apparatus having a steering reaction force applying means for driving and applying a steering reaction force to the steering wheel,
Tire lateral force detecting means for detecting tire lateral force;
A turning axial force detecting means for detecting a turning axial force acting on a rack shaft of the steering mechanism;
A target steering reaction force, which is a target value of the steering reaction force applied to the steering wheel by the steering reaction force applying means, is generated according to the tire lateral force and the turning axial force, and the generated target steering reaction force A steering reaction force control means for controlling the steering reaction force application means based on:
Provided,
In the steering reaction force control means, the absolute value of the difference between the tire lateral force and the turning axial force is a value indicating a linear region in which the tire lateral force changes linearly with respect to a tire slip angle. The target steering reaction force is generated only in accordance with the tire lateral force, and the absolute value of the difference is a value indicating a nonlinear region where the tire lateral force changes nonlinearly with respect to the tire slip angle. In this case, the larger the tire lateral force, the smaller the steering reaction force corresponding to the tire lateral force out of the target steering reaction force, while increasing the steering reaction force corresponding to the turning axial force. A vehicle steering device. The vehicle steering apparatus according to any one of claims 1 to 3,
A steering angular velocity detecting means for detecting a steering angular velocity of the tire is provided;
The vehicle steering apparatus according to claim 1, wherein the steering reaction force control means corrects the turning axial force to decrease as the turning angular velocity increases.

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