JP5125328B2 - Steering control device - Google Patents

Description

  The present invention relates to a steering control device capable of switching between a front wheel steering mode and a front and rear wheel in-phase steering mode.

Conventionally, this type of steering control device is known (see, for example, Patent Document 1). In the configuration described in Patent Document 1, three modes are set: a general traveling mode (front wheel steering mode), a parallel traveling mode (front and rear wheel in-phase steering mode), and a small turning mode (front and rear wheel reverse phase steering mode). In addition, a mode changeover switch for switching between these modes is provided.
Japanese Patent Laid-Open No. 3-7676

  However, in the above-mentioned patent document 1, sufficient examination is not made about the turning angle control method during the mode transition when each mode is switched. Therefore, for example, when switching from the normal travel mode to the parallel travel mode is performed under the condition where the vehicle is traveling and the vehicle is being steered, there is a possibility that a sudden change in vehicle behavior may occur due to a sudden change in the rear wheel turning angle. On the other hand, in order to prevent such an inconvenience, a configuration in which mode switching is prohibited while the vehicle is running and steering is conceivable. However, in such a configuration, the conditions for enabling mode switching are limited. Must-have.

  Therefore, the present invention makes it possible to appropriately change the vehicle behavior due to the mode switching under the situation where the vehicle is running and being steered while enabling the mode switching under the situation where the vehicle is running and being steered. An object of the present invention is to provide a steering control device that can be prevented.

In order to achieve the above object, a steering control device according to the first aspect of the present invention includes a steering mode switching means for switching a steering mode of the steering means,
When the steering mode switching means switches the steering mode of the steering means from the front wheel steering mode to the front-rear wheel in-phase steering mode, the vehicle is running and steering is in progress. A mode transition control means for performing steering angle control,
Wherein the mode transition time control means, a change amount of the steering angle of the rear wheels relative to the steering angle, is gradually changing, based on the ratio of the rear wheel turning angle and the front wheel turning angle,
The mode transition control means reduces the change amount of the rear wheel turning angle in a range where the ratio of the rear wheel turning angle to the front wheel turning angle is small, and increases the ratio of the rear wheel turning angle to the front wheel turning angle. The amount of change in the turning angle of the rear wheel is increased as the ratio of the rear wheel is turned, and the amount of change in the turning angle of the rear wheel is reduced as the ratio of the rear wheel turning angle to the front wheel turning angle approaches 1. .

A fourth invention is the steering control device according to any one of the first to third inventions,
The mode transition control means further performs front wheel turning angle slow control for reducing the amount of change in the turning angle of the front wheel with respect to the steering angle compared to that in the front wheel turning mode.

A steering control device according to a fifth aspect of the present invention includes a steering mode switching unit that switches a steering mode of the steering unit,
When the steering mode switching means switches the steering mode of the steering means from the front wheel steering mode to the front-rear wheel in-phase steering mode, the vehicle is running and steering is in progress. A mode transition control means for performing steering angle control,
The mode transition control means performs front wheel turning angle slow control for reducing the amount of change in the turning angle of the front wheels compared to that in the front wheel turning mode.

A sixth invention is the steering control device according to the fourth or fifth invention,
The mode transition control means stops the front wheel turning angle slow control when the steering speed becomes a predetermined value or more.

A seventh invention is the steering control device according to the sixth invention,
When the steering speed becomes a predetermined value or more, the mode transition control means further turns the rear wheel in a direction in which the turning ability is increased according to the steering direction.

An eighth invention is the steering control device according to any one of the first to seventh inventions,
The mode transition control means stops the mode switching when the backward movement of the vehicle is detected.

  According to the present invention, it is possible to perform mode switching under a situation where the vehicle is traveling and being steered, and a sudden change in the vehicle behavior caused by the mode switching under the situation where the vehicle is traveling and being steered is appropriate. Thus, a steering control device that can be prevented easily is obtained.

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

  FIG. 1 is a system configuration diagram showing an embodiment of a steering control device 1 according to the present invention. The steering control device 1 of the present embodiment is configured with a steering control ECU 10 as a center. The steering control ECU 10 has a hardware configuration centered on a microcomputer including a CPU, a ROM, a RAM, and the like connected to each other via a bus (not shown). The ROM stores programs and data for executing various processes described later.

  The steering control ECU 10 receives sensor values from the steering angle sensor 12, the wheel speed sensor 14, and the like, and a mode switching signal from the mode switch 16.

  The steering angle sensor 12 generates a signal corresponding to the steering angle of the steering wheel operated by the driver. The wheel speed sensor 14 is provided on the wheel and generates a signal (vehicle speed pulse) corresponding to the rotational speed of the wheel. The steering control ECU 10 grasps the steering angle θ of the steering wheel (hereinafter referred to as “steering steering angle θ”) based on the information from the steering angle sensor 12.

  The mode switch 16 is a switch for switching the steering mode, and is disposed at an appropriate position that can be operated by the driver, such as a steering column or a steering wheel. The mode change switch 16 is operated by the driver and generates a signal (mode change signal) corresponding to the operation mode. In this example, it is assumed that there are at least two modes of the steering mode, that is, the front wheel steering mode (2WS mode) and the front and rear wheel in-phase steering mode. In this case, the mode switch 16 is operated to switch between the front wheel steering mode and the front and rear wheel in-phase steering mode. As another mode, a front-rear wheel reverse phase steering mode may exist. Further, the current steering mode may be displayed, for example, on a meter or the like so that the driver can grasp it.

  A rear wheel steering actuator 20 is connected to the steering control ECU 10. The steering control ECU 10 controls the rear wheel steering actuator 20 to steer the rear wheels. The rear wheel steering actuator 20 may be shared for the left and right rear wheels, or may be provided independently for the left and right rear wheels. The rear wheel steering mechanism may be of any configuration as long as the left and right rear wheels are mechanically independent from the front wheel steering mechanism and can be steered in the same phase and with a desired turning amount by electronic control. It may be.

The steering control ECU 10 controls the rear wheel steering actuator 20 in principle according to the current steering mode except during the mode transition described later. In the front wheel turning mode, the steering control ECU 10 does not operate the rear wheel steering actuator 20, and therefore the rear wheel turning angle is substantially maintained at zero. The steering control ECU 10 assists by a power steering device (not shown) based on information from a torque sensor (not shown) and a wheel speed sensor 14 for detecting the steering torque of the steering wheel during the front wheel steering mode. Torque control may be performed, or transmission ratio variable control may be performed by a transmission ratio variable device (not shown) based on information from the steering angle sensor 12 and the wheel speed sensor 14. In any case, in the front wheel turning mode, the front wheel turning angle δ _F is δ _F = k · θ with respect to the steering angle θ. Here, k is a steering angle / steering angle ratio, and k may be a fixed value or may be a variable value by the above-described transmission ratio variable control.

In the front-rear wheel in-phase steering mode, the steering control ECU 10 operates the rear wheel steering actuator 20 so that δ _R = k · θ. Here, [delta] _R is the rear wheel turning angle. Therefore, in the front-rear wheel in-phase steering mode, the front wheels and the rear wheels have the same turning angle (= k · θ), and front-rear wheel in-phase steering (translation of the vehicle) is realized.

  In the present embodiment, the mode switch 16 can be operated during steering and while the vehicle is running. That is, the mode switching from the front wheel steering mode to the front and rear wheel in-phase steering mode can be realized even during steering and traveling of the vehicle. As a result, a system that is highly convenient for the driver can be realized without limiting the opportunity for mode switching. However, when switching from the front wheel steering mode to the front and rear wheel in-phase steering mode is immediately performed during steering, the rear wheel steering angle changes substantially from zero to k · θ. There is a risk of sudden changes in vehicle behavior due to the above. Therefore, in this embodiment, as described in detail below, when switching from the front-wheel steering mode to the front-and-rear wheel in-phase steering mode is instructed during steering and while the vehicle is running, the appropriate mode transition control is performed. Then, a sudden change in vehicle behavior is prevented by shifting to the front and rear wheel in-phase steering mode. Details regarding the mode transition control will be described below.

  FIG. 2 is a flowchart showing an example of main processing executed by the steering control ECU 10 of the present embodiment.

  In step 100, it is determined whether or not a mode switching operation from the front wheel steering mode to the front and rear wheel in-phase steering mode has occurred by the mode switch 16. When a mode switching operation from the front wheel steering mode to the front and rear wheel in-phase steering mode occurs, the process proceeds to step 102, and otherwise, the process ends.

In step 102, the steering steering angle θ (hereinafter referred to as “mode switching”) when a mode switching operation from the front wheel steering mode to the front and rear wheel in-phase steering mode occurs based on the output value of the steering angle sensor 12 input in the current cycle. Hour steering angle θ ₀ ”) is stored.

In step 104, the mode switching during steering angle theta ₀ whether greater than a predetermined value is determined. The predetermined value may be a value indicating that steering is in progress, and may be a value corresponding to, for example, a 90-degree rotation of the steering wheel. If the steering angle θ ₀ at the time of mode switching is larger than a predetermined value, that is, if the steering is being performed, the process proceeds to step 106, and otherwise, the process proceeds to step 108.

In step 106, mode transition control is executed. The mode transition control is a control that alleviates a sudden change in the rear wheel steering angle that may occur when switching from the front wheel steering mode to the front and rear wheel in-phase steering mode. That is, in the mode transition control, the rear wheel turning angle is not instantaneously changed from substantially zero to k · θ ₀ , but the ratio of the rear wheel turning angle δ _{R to} the front wheel turning angle δ _F (hereinafter, The rear wheel turning angle is increased stepwise (gradually) from substantially zero based on the “front / rear turning angle ratio δ _R / δ _F ”, and the rear wheel turning angle is set to the subsequent steering steering angle. It is possible to catch up to k · θ according to θ. Such mode transition time control, for example, or gradually increased to wheel steering angle k · theta after corresponding rear wheel steering angle [delta] _R in steering angle theta, and / or, before according to the steering angle theta may be implemented by or reduce relative to wheel steering angle [delta] _F to the front wheels steered mode. Some preferred specific examples of the mode transition control will be described later.

In this step 106, the time of mode transition control is completed (the rear wheel steering angle [delta] _R is k · theta), the process proceeds to step 108.

  In step 108, control in the front and rear wheel in-phase steering mode is performed as usual. That is, as described above, both the front wheels and the rear wheels are controlled so as to be k · θ with respect to the steering angle θ. As a result, the driver can translate the vehicle.

  As described above, according to the present embodiment, at the time of switching from the front wheel steering mode to the front and rear wheel in-phase steering mode during steering, by shifting to the front and rear wheel in-phase steering mode via the mode transition control, A sudden change in vehicle behavior can be prevented appropriately.

  Next, a specific example of control at the time of mode transition suitable as the processing of step 106 will be described. In the following description, when the mode changeover switch 16 is operated in step 100 in FIG. 2 and there is no new operation of the mode changeover switch 16 (that is, the mode changeover is performed again during the mode transition control). If not instructed).

[Specific example 1 of mode transition control]
The embodiment 1 relates to gradual change control of the rear wheel steering angle [delta] _R. In the first specific example, the steering control ECU 10 performs the mode-switching steering angle θ ₀ obtained in step 102 of FIG. 2 described above, the current steering steering angle θ input as needed thereafter, and the current Based on the wheel turning angle δ _R and the current front wheel turning angle δ _F , the rear wheel target turning angle δ _R * (target value to be realized in the current cycle) is determined according to the following relationship, and the determination is made. The rear wheels are steered so that the rear wheel target turning angle δ _R * is achieved (that is, the rear wheel steering actuator 20 is controlled).
δ _R * = k · (θ−θ ₀ ) + k · θ ₀ · α
Here, α is a coefficient of 0 <α ≦ 1, and is set based on the front / rear turning angle ratio δ _R / δ _F as shown in FIG. The rear wheel turning angle δ _R used for calculating the front / rear turning angle ratio δ _R / δ _F can detect the rear wheel turning angle δ _R such as a rotation angle sensor for detecting the rotation angle of the rear wheel steering actuator 20. It may be derived based on a sensor, or may be the rear wheel target turning angle δ _R * of the previous cycle. Further, the front wheel turning angle [delta] _F used for calculating the front-rear steering angle ratio [delta] _{R /} [delta] _F may be derived based on the output value of the steering angle sensor 12 (theta current steering angle).

As shown in FIG. 3, the coefficient α is preferably such that in the range where the front / rear turning angle ratio δ _R / δ _F is small, the change in the rear wheel turning angle δ _R with respect to the steering angle θ becomes smaller, and the front / rear turning angle. As the ratio δ _R / δ _F increases, the change in the rear wheel turning angle δ _R with respect to the steering angle θ increases, and as the front / rear turning angle ratio δ _R / δ _F approaches 1, the rear wheel steering with respect to the steering angle θ as the change of the angular [delta] _R is reduced (as tapering) is determined. Thereby, sudden change and the vehicle behavior during the rear wheel steering angle [delta] a change in _R "slow" → "sudden" → "slow" and mode switching by changing depending on the front and rear steering angle ratio [delta] _{R /} [delta] _F The driver's uncomfortable feeling can be moderated appropriately.

The mode transition control according to the specific example 1 continues until the front / rear turning angle ratio δ _R / δ _F becomes 1, and the front / rear turning angle ratio δ _R / δ _F becomes 1 (that is, The process ends when the rear wheel turning angle δ _R catches up with the front wheel turning angle δ _F ). When the control at the time of mode transition is completed, the control in the front and rear wheel in-phase steering mode at step 108 in FIG. 2 is realized.

[Specific example 2 of mode transition control]
The embodiment 2 relates to the slow control of the front wheel turning angle [delta] _F. Incidentally, the slow control of the front wheel turning angle δ _F described below includes a mechanism for absorbing the rotational difference between the input shaft and the output shaft of the steering, such as a differential mechanism of the transmission ratio variable device, and a front wheel. The present invention is applicable to a steering apparatus including a front wheel steering actuator that can be steered by a desired amount. That is, the present invention can be applied to a steering device including a transmission ratio variable device, a steer-by-wire type steering device, and a steering device that can also function as a steer-by-wire type steering device. There are various types of configurations of this type of steering apparatus. For example, the configuration disclosed in Japanese Patent Application Laid-Open No. 2007-90947 may be used.

In the second specific example, the steering control ECU 10 performs the mode-switching steering angle θ ₀ obtained in step 102 of FIG. 2 described above, the current steering steering angle θ input as needed thereafter, Based on the rear wheel turning angle δ _R and the current front wheel turning angle δ _F , the front wheel target turning angle δ _F * (target value to be realized in the current cycle) is determined according to the following relationship, and the determination is made. The front wheels are steered so that the front wheel target turning angle δ _F * is achieved (that is, a front wheel steering actuator (not shown) is controlled).
δ _F * = k · θ ₀ + k · (θ−θ ₀ ) · β
Here, β is a coefficient of 0 <β ≦ 1, and is set based on the front / rear turning angle ratio δ _R / δ _F as shown in FIG. Incidentally, the front wheel turning angle [delta] _F used for calculating the front-rear steering angle ratio [delta] _{R /} [delta] _F, similar to the rear wheel steering angle [delta] _R, can detect the front wheel turning angle [delta] _F, such as the steering angle sensor 12 sensor Or the front wheel target turning angle δ _F * of the previous cycle may be used.

The coefficient beta, as shown in FIG. 4, in the process of the front and rear steering angle ratio [delta] _{R /} [delta] _F is increased from 0 to 1, in the section up to the vicinity of 0.5 before and after the steering angle ratio [delta] _{R /} [delta] _F is It decreases from 1 to a local minimum value close to 0, and increases from a local minimum value to 1 in a section where the front / rear turning angle ratio δ _R / δ _F is from about 0.5 to 1. Completion Thus, while gently vehicle behavior changes during mode switching, the rear wheel turning angle [delta] _R by causing quickly catch up with the front wheel turning angle [delta] _F, quickly transition to the front and rear wheels in phase steered mode Can be made. In the example shown in FIG. 4, the change characteristic of the coefficient β is such that the minimum value is set to the front / rear turning angle ratio δ _R / δ _F near 0.5 and the front / rear turning angle ratio taking the minimum value is the center. While a symmetrical, change characteristics of the coefficient β is not limited to this, the amount of change in the front wheel turning angle [delta] _F is any in the manner reduced compared to the front wheel steering mode (mode to be slow) That's fine.

The mode transition control according to the specific example 2 continues until the front / rear turning angle ratio δ _R / δ _F becomes 1, and the front / rear turning angle ratio δ _R / δ _F becomes 1 (that is, The process ends when the rear wheel turning angle δ _R catches up with the front wheel turning angle δ _F ). When the control at the time of mode transition is completed, the control in the front and rear wheel in-phase steering mode at step 108 in FIG. 2 is realized.

Incidentally, the slow control of the front wheel turning angle [delta] _F according to the embodiment 2 may be implemented in combination with the gradual change control of the wheel steering angle [delta] _R after the above.

[Specific example 3 of control at the time of mode transition]
This specific example 3 relates to an improved example in consideration of the sudden steering for the slow control (specific example 2) of the front wheel turning angle δ _F described above. In this specific example 3, the steering control ECU 10 monitors the steering speed (the amount of change with respect to the time of the steering angle θ) during the slow control, and when sudden steering is detected at which the steering speed exceeds a predetermined value. The above-described slow control is cancelled.

  FIG. 5 is a flowchart illustrating an example of a process for realizing the third specific example.

  In step 500, it is determined whether or not the steering speed dθ / dt is greater than a predetermined value A. The predetermined value A is a value indicating rapid steering, and a value adapted by experiment or the like is used. If the steering speed dθ / dt is larger than the predetermined value A, that is, if sudden steering is detected, the process proceeds to step 504, and otherwise, the process proceeds to step 502.

In step 502, the coefficient β is determined based on the current front / rear turning angle ratio δ _R / δ _F in the same manner as in the second specific example, and the front wheel target steering is determined based on the determined coefficient β. The angle δ _F * is determined. Then, a front wheel steering actuator (not shown) is controlled so that the determined front wheel target turning angle δ _F * is realized.

In step 504, the coefficient β is set to 1 regardless of the current front / rear turning angle ratio δ _R / δ _F , and based on the determined coefficient β, the front wheel target turning angle δ _F * Is determined. In this case, since the coefficient β is 1, the front wheel turning mode is substantially realized. By the way, during the above-described slow control, the steering response of the front wheels is somewhat deteriorated, but the processing of this step 504 makes it possible to recover (improve) the steering response of the front wheels when sudden steering is detected. The ability to avoid obstacles is restored (improved).

In step 506, it is determined whether the coefficient β is smaller than 1. When the coefficient β is smaller than 1, that is, when the mode transition control is continued, the process returns to Step 500. On the other hand, when the control at the time of mode transition is normally completed and the coefficient β becomes 1, or when the coefficient β becomes 1 through the above step 504 due to sudden steering, the processing of FIG. finish. When the control at the time of mode transition is normally completed, the control in the front-rear wheel in-phase steering mode at step 108 in FIG. 2 is realized. On the other hand, when the coefficient β becomes 1 via the above step 504 due to sudden steering (when the control at the time of mode transition is canceled), for example, the steering speed dθ / dt is smaller than the predetermined value A. The front wheel turning mode may be realized until the steering speed dθ / dt becomes smaller than the predetermined value A, and the mode transition control may be restarted from step 102 in FIG. In this case, the steering steering angle θ when the steering speed dθ / dt has become smaller than the predetermined value A (that is, the steering steering angle θ at the time of resumption) is regarded as the above-described mode switching steering angle θ ₀ ( The subsequent processing may be executed.

[Specific example 4 of control at the time of mode transition]
This embodiment 4 relates to an improved example in consideration of quick steering for gradual change control of the wheel steering angle [delta] _R after the above (Example 1). In this specific example 4, the steering control ECU 10 monitors the steering speed (change speed of the steering angle θ) during execution of the gradual change control, and when sudden steering is detected at which the steering speed becomes a predetermined value or more, Instead of the above-described gradual change control, the rear wheels are steered in a direction in which the turning ability is increased according to the steering direction.

  FIG. 6 is a flowchart illustrating an example of a process for realizing the fourth specific example.

  In step 600, it is determined whether or not the steering speed dθ / dt is greater than a predetermined value A. The predetermined value A is a value indicating rapid steering, and a value adapted by experiment or the like is used. If the steering speed dθ / dt is greater than the predetermined value A, the process proceeds to step 606; otherwise, the process proceeds to step 602.

In step 602, the coefficient α is determined based on the current front / rear turning angle ratio δ _R / δ _F in the same manner as in the first specific example, and the rear wheel target rotation is determined based on the determined coefficient α. The steering angle δ _R * is determined. Then, the rear wheel steering actuator 20 is controlled so that the determined rear wheel target turning angle δ _R * is realized.

  In step 604, it is determined whether the coefficient α is smaller than 1. When the coefficient α is smaller than 1, that is, when the mode transition control is continued, the process returns to step 600. On the other hand, when the mode transition control is normally completed and the coefficient α becomes 1, the process of FIG. 6 ends. When the control at the time of mode transition is normally completed, the control in the front-rear wheel in-phase steering mode at step 108 in FIG. 2 is realized.

  In step 606, it is determined whether or not a change amount Δθ of the steering angle θ (for example, an amount obtained by subtracting the steering angle θ of the previous cycle from the steering angle θ of the current cycle) is greater than zero. When the change amount Δθ of the steering angle θ is larger than 0, that is, when the steering direction of the steering wheel is the cut side, the process proceeds to step 610, and when the change amount Δθ of the steering angle θ is smaller than 0, that is, the steering wheel. If the steering direction is on the switchback side, the process proceeds to step 608.

In Step 608, the rear wheel target turning angle δ _R * is set to the rear wheel maximum turning angle δ _Rmzx of the cut side.

In step 610, gradual change control of the rear wheel steering angle [delta] _R is canceled, the rear wheel target steering angle [delta] _{R *} is set to zero.

  Thus, according to step 608 and step 610, when a sudden steering with a steering speed of a predetermined value or more is detected, instead of the above-described gradual change control, the rear wheel has a turning ability according to the steering direction. Since the vehicle is steered in an increasing direction, the turning ability of the vehicle can be improved, and the ability to avoid obstacles and the like is improved.

  In this specific example 4, both processes of steps 608 and 610 are prepared, but only one of the processes may be executed. That is, for example, the processing in step 608 may be omitted.

Incidentally, also, gradual change control of the rear wheel steering angle [delta] _R according to the embodiment 4 may be implemented in combination with the slow control of the front wheel turning angle [delta] _F according to an exemplary embodiment 2 or 3 above.

[Specific example 5 of mode transition control]
In this specific example 5, the steering control ECU 10 monitors the traveling direction (forward or reverse) of the vehicle based on, for example, the shift position, and prohibits mode transition when vehicle reverse is detected.

  FIG. 7 is a flowchart illustrating an example of a process for realizing the fifth specific example.

In step 700, it is determined whether the vehicle is moving forward. If the vehicle is moving forward is gradual change control and slow control of the front wheel turning angle [delta] _F is the execution of the wheel steering angle [delta] _R after the above step 702 and 704, from the coefficient α is 1 in step 706 Whether or not it is small is determined. If the determination is negative (that is, if the coefficient α is 1 and the control during mode transition is normally completed), the processing of FIG. Return to 700.

On the other hand, for example, if the shift position is R (reverse) and a negative determination is made in step 700, that is, if the vehicle is moving backward, the process proceeds to step 708. In step 708, the mode transition is stopped. For example, it is canceled gradual change control of the rear wheel steering angle [delta] _R, together with the rear wheel target steering angle [delta] _{R *} is set to 0, the slow control of the front wheel turning angle [delta] _F is canceled, the front wheel target rolling The steering angle δ _F * is k · θ.

According to the fifth specific example, when the vehicle is moving backward, it is different from the driver's intention when the mode switching is requested in consideration that the direction in which the driver wants the vehicle to travel and the front wheel turning direction do not necessarily match. it is possible to prevent the rear wheel steering angle [delta] _R is controlled in the direction.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above-described embodiment, mode switching (switching from the front wheel steering mode to the front-and-rear wheel in-phase steering mode) is possible while the vehicle is traveling, but the front wheel steering is performed only when the vehicle speed is lower than a predetermined value. Switching from the mode to the front and rear wheel in-phase steering mode may be permitted.

  The process shown in FIG. 2 is shown to be executed regardless of whether or not the vehicle is running. For example, the process is executed when the vehicle speed is lower than a predetermined value. May be. For example, when the vehicle speed exceeds a predetermined value during the execution of the mode transition control, the mode transition may be prohibited by the same process as in FIG. On the other hand, when the vehicle stops during execution of the mode transition control, the mode transition control is temporarily interrupted to prevent so-called rear wheel stationary steering, and then the vehicle starts moving. It is good also as performing the continuation of control at the time of mode transition.

  Further, in the above-described embodiment, the mode switching is instructed by the driver's operation of the mode switching switch 16, but the mode switching is instructed through other input modes such as voice input and gesture input by the driver. May be.

1 is a system diagram showing an embodiment of a steering control device according to the present invention. It is a flowchart which shows an example of the main processes performed by steering control ECU10 of a present Example. It is a figure which shows the relationship between the front-rear turning angle ratio (delta) _R / (delta) _F and the coefficient (alpha) by the specific example 1 of control at the time of mode transition. It is a figure which shows the relationship between front-rear turning angle ratio (delta) _R / (delta) _F and the coefficient (beta) by the specific example 2 of control at the time of mode transition. 12 is a flowchart illustrating an example of a process for realizing a specific example 3; 12 is a flowchart illustrating an example of a process for realizing a specific example 4; 10 is a flowchart illustrating an example of a process for realizing a specific example 5;

Explanation of symbols

1 Steering control device 10 Steering control ECU
12 Steering angle sensor 14 Wheel speed sensor 16 Mode change switch 20 Rear wheel steering actuator

Claims (6)

Steering mode switching means for switching the steering mode of the steering means;
When the steering mode switching means switches the steering mode of the steering means from the front wheel steering mode to the front-rear wheel in-phase steering mode, the vehicle is running and steering is in progress. A mode transition control means for performing steering angle control,
Wherein the mode transition time control means, a change amount of the steering angle of the rear wheels relative to the steering angle, is gradually changing, based on the ratio of the rear wheel turning angle and the front wheel turning angle,
The mode transition control means reduces the change amount of the rear wheel turning angle in a range where the ratio of the rear wheel turning angle to the front wheel turning angle is small, and increases the ratio of the rear wheel turning angle to the front wheel turning angle. A steering control device that increases the amount of change in the turning angle of the rear wheel as the vehicle moves, and decreases the amount of change in the turning angle of the rear wheel as the ratio of the rear wheel turning angle to the front wheel turning angle approaches 1 . 2. The steering control according to claim 1, wherein the mode transition time control means further performs front wheel turning angle slow control for reducing a change amount of a front wheel turning angle with respect to a steering angle as compared with a front wheel turning mode. apparatus. Steering mode switching means for switching the steering mode of the steering means;
When the steering mode switching means switches the steering mode of the steering means from the front wheel steering mode to the front-rear wheel in-phase steering mode, the vehicle is running and steering is in progress. A mode transition control means for performing steering angle control,
The mode transition control means is a steering control device that performs front wheel turning angle slow control for reducing the amount of change in the turning angle of the front wheels compared to that in the front wheel turning mode. Wherein the mode transition time control unit, when the steering speed is equal to or greater than a predetermined value, stops the front wheel turning angle slow control, steering control apparatus according to claim 2 or 3. 5. The steering control device according to claim 4 , wherein when the steering speed becomes equal to or higher than a predetermined value, the mode transition control unit further turns the rear wheel in a direction in which the turning ability is increased in accordance with the steering direction. . The steering control device according to any one of claims 1 to 5 , wherein the mode transition control unit stops the mode switching when the backward movement of the vehicle is detected.

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