JP2008273443A - Steering control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain operability and stability according to a sensing characteristic of a driver. <P>SOLUTION: The steering control device is equipped with a speed sensor 11 for detecting the vehicle speed, an electronic control unit 20 for setting a target yaw rate gain or a target lateral acceleration gain as a target vehicle characteristic based on the vehicle speed detected by the speed sensor 11, and a steering actuator 30 for controlling steering of front/rear wheels so as to make a vehicle motion state approach the target vehicle characteristic set by the electronic control unit 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a steering control device.

  Conventionally, there has been proposed a steering device that steers a steered wheel of a vehicle in response to a driver's steering input. Patent Document 1 discloses a steering device that can obtain a desired yaw rate gain characteristic corresponding to a vehicle speed.

  The steering device of Patent Document 1 sets a target yaw rate gain of a vehicle according to a vehicle speed, estimates a yaw rate gain of the vehicle, and based on a difference between the set target yaw rate gain and the estimated yaw rate gain. A target rack axial force of the shaft is set, and the electric motor is controlled based on the set target rack axial force.

Here, as shown in FIG. 4 of the same document, the target yaw rate gain characteristic is large during low-speed traveling (for example, 30 to 80 km / h) and small during high-speed traveling (for example, 100 km / h or more). It is set to non-linear. For this reason, a steering characteristic that achieves both improved turning performance during low-speed traveling and steering stability during high-speed traveling is realized.
Japanese Patent Laying-Open No. 2006-159960 (FIG. 4)

  The steering device of Patent Document 1 improves the turning ability when traveling at a low speed and improves the steering stability when traveling at a high speed. However, since the steering device does not set a target value that matches the sensitivity characteristics of the driver in the entire vehicle speed range, it is difficult to realize ease of driving and comfort in the entire vehicle speed range. For this reason, there exists a problem that the controllability and stability according to the sensitive characteristic of a driver cannot be obtained.

  The present invention has been proposed in order to solve the above-described problems, and an object of the present invention is to provide a steering control device capable of obtaining maneuverability and stability in accordance with a driver's sensitivity characteristics.

  A steering control device according to the present invention includes a vehicle speed detection unit that detects a vehicle speed, a target vehicle characteristic setting unit that sets a target lateral acceleration gain as a target vehicle characteristic based on the vehicle speed detected by the vehicle speed detection unit, and a vehicle motion Steering control means for controlling the steering of at least one of the front and rear wheels so that the state approaches the target vehicle characteristic set by the target vehicle characteristic setting means.

  The target vehicle characteristic setting means sets a target lateral acceleration gain as the target vehicle characteristic based on the vehicle speed. Therefore, when the vehicle speed changes, a target lateral acceleration gain corresponding to the driver's sensitivity characteristics is set. The steering control means controls the steering of at least one of the front wheels and the rear wheels so that the vehicle motion state approaches the target vehicle characteristics.

  Therefore, the steering control device according to the present invention sets the target lateral acceleration gain as the target vehicle characteristic based on the vehicle speed, and steers at least one of the front wheels and the rear wheels so that the vehicle motion state approaches the set target vehicle characteristic. By controlling the control, the maneuverability and stability corresponding to the driver's sensitivity characteristics can be obtained.

  Here, the sensitivity characteristics of the driver tend to increase the recognition sensitivity of the yaw movement by visual information when the vehicle speed is less than a predetermined value, and increase the recognition sensitivity of the lateral movement by the bodily information when the vehicle speed exceeds the predetermined value. is there.

  Therefore, the target vehicle characteristic setting means sets a large contribution rate of the target yaw rate gain when the vehicle speed is equal to or less than a predetermined value based on the vehicle speed detected by the vehicle speed detection means, and the vehicle speed is set to the predetermined value. If it exceeds, increase the contribution rate of the target lateral acceleration gain.

  At this time, when the vehicle speed is less than or equal to a predetermined value, the steering control means controls the steering amount of at least one of the front wheels and the rear wheels so that the vehicle motion state approaches the target yaw rate gain, and the vehicle speed reaches a predetermined value. If it exceeds, the steering of at least one of the front wheels and the rear wheels may be controlled so that the vehicle motion state approaches the target lateral acceleration gain.

  Thereby, since the said invention sets a target vehicle characteristic setting according to the sensitive characteristic of the driver which changes with vehicle speeds, the controllability and stability corresponding to the sensitive characteristic of a driver can be acquired.

  The steering control device according to the present invention can obtain maneuverability and stability corresponding to the sensitivity characteristics of the driver.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[Principle of the Invention]
FIG. 1 is a diagram illustrating a driver's sensitivity characteristics in a planar motion (yaw motion, lateral motion) of a vehicle. In FIG. 1, vehicle motion up to 1 Hz is targeted.

  The physical quantity of recognition is the rotational angular velocity for yaw movement, the sensation of jerk (differential value of acceleration) and the speed of vision for lateral movement. Further, the visual recognition threshold for lateral movement is obtained by converting the speed recognition threshold to vibration of 0.5 Hz. The conversion of vibration will be described later.

  The recognition threshold (a size that allows the driver to perceive whether or not the driver is exercising) differs depending on the difference in the information obtained (body experience information, visual information). That is, the recognition sensitivity based on visual information is high for yaw movement, and the recognition sensitivity based on bodily sensation is high for lateral movement.

  Reference materials for such recognition sensitivity include "Improvement of steering transient response performance based on visual / sway sensitivity characteristics (1st report)", Automotive Technology Academic Lecture Preprint No.10-06 (2006) ), “Handbook of Human Vibration”, and ACADEMIC PRESS.

  Here, when considering the plane motion of the vehicle, the yaw motion in a steady turning motion (turning radius R, vehicle speed v) is expressed as in equation (1), and lateral motion is expressed as in equation (2). Is done.

Note that r: yaw rate, G _y : lateral acceleration. Then, equations (3) and (4) are obtained from equations (1) and (2).

  By substituting the recognition threshold for yaw movement (recognition threshold for visual perception with high recognition sensitivity) and the recognition threshold for lateral movement (recognition threshold for physical perception with high recognition sensitivity) shown in FIG. You can see if you can recognize the movement of the turning radius. This is shown in FIG.

  FIG. 2 is a diagram illustrating motion recognition characteristics of planar motion. This represents a recognizable turning motion threshold value, and the larger the turning radius, the higher the motion recognition sensitivity. In addition, the motion with high recognition sensitivity differs depending on the vehicle speed range. That is, the recognition sensitivity of the yaw movement by visual information is high below a certain vehicle speed (about 70 km / h), and the recognition sensitivity of lateral movement by bodily sensation information is high above that.

(Conversion method for recognition threshold of lateral movement)
In FIG. 1, the recognition threshold value of lateral movement based on the bodily sensation is shown as a value of jerk (acceleration differential value). On the other hand, since equation (2) is indicated by acceleration, conversion is necessary. In this embodiment, the acceleration is converted to an acceleration at 0.5 Hz vibration. Here, the conversion method will be described.

First, considering a sinusoidal vibration (frequency ω) in which the amplitude of the jerk j is a _j , the equation (5) is obtained.

  The acceleration vibration g having such a change in jerk is expressed as shown in Equation (6).

Therefore, by dividing the jerk amplitude _aj by the frequency ω, it can be converted into an acceleration at that frequency.

(Setting target vehicle characteristics)
A target vehicle characteristic is set based on the sensitivity characteristic with respect to the planar motion of the driver as described above. As a setting method, if the motion with higher recognition sensitivity is set to a linear characteristic with respect to the driver's steering or a characteristic close thereto, the vehicle characteristic desired by the driver can be obtained.

  FIG. 3 is a diagram showing (A) yaw rate gain and (B) lateral acceleration gain as target vehicle characteristics with respect to vehicle speed. The yaw rate gain is a value obtained by dividing the yaw rate by the steering angle. The lateral acceleration gain is a value obtained by dividing the lateral acceleration by the steering angle.

  According to FIG. 3, the yaw rate gain is constant in order to generate the yaw rate linearly with respect to the steering of the driver in the low speed region where the recognition sensitivity of the yaw motion is high. Therefore, in the low speed region, if the steering is controlled so as to approach the yaw rate gain, the steering control that matches the sensitivity characteristics of the driver is performed.

  In the high speed region, which is a region where the recognition sensitivity of the lateral motion is high, the lateral acceleration is generated linearly or in a state close to it, so the lateral acceleration gain is constant or increases with a slight gradient according to the vehicle speed. Therefore, in the high speed region, if the steering is controlled so as to approach the lateral acceleration gain, the steering control that matches the sensitivity characteristics of the driver is performed. Next, an embodiment for realizing such steering control will be described.

[Embodiment]
FIG. 4 is a block diagram showing the steering control device according to the embodiment of the present invention. The steering control device includes a vehicle speed sensor 11 that detects a vehicle speed, a steering angle sensor 12 that detects a steering angle, a yaw rate sensor 13 that detects a yaw rate, a lateral acceleration sensor 14 that detects lateral acceleration, and an electronic control that is a computer. A unit 20 and a steering actuator 30 that controls the steering amounts of the front wheels and the rear wheels according to the electronic control unit 20 are provided.

  The steering actuator 30 of the present embodiment controls the steering amounts of both the front wheels and the rear wheels, but may control only one of them.

  FIG. 5 is a block diagram relating to a transfer function of the steering control device. The steering control device sets the target vehicle characteristics (target yaw rate gain / target lateral acceleration gain) based on the vehicle speed, and estimates the real-time yaw rate gain / real-time lateral acceleration gain from the vehicle motion of the steering angle, yaw rate, and lateral acceleration. To do. Then, the steering control device controls the steering actuator so that the real-time yaw rate gain approaches the target yaw rate gain when the vehicle speed is 70 km / h or less. Further, when the vehicle speed exceeds 70 km / h, the steering control device controls the steering actuator so that the real-time lateral acceleration gain approaches the lateral acceleration gain.

  In FIG. 5, the feedback control system is exemplified. However, the present invention is not limited to this, and feed for controlling the control amount of at least one of the front wheels and the rear wheels based on the target vehicle characteristics. A forward control system may be used.

(Setting target vehicle characteristics)
The electronic control unit 20 sets the target vehicle characteristics using the vehicle speed detected by the vehicle speed sensor 11. For example, when the vehicle speed is 70 km / h or less, the electronic control unit 20 sets a target yaw rate gain that is a target vehicle characteristic according to the following equation (7).

here,
r ₀ : Yaw rate gain l: Wheel base l _f , l _r : Distance from the center of gravity to the front or rear axle K _f , K _r : Cornering power of the front wheel or rear wheel v ₀ : Reference vehicle speed (for example, 70 km / h) )
k ₀ : proportionality constant
It is.

  Further, when the vehicle speed exceeds 70 km / h, the electronic control unit 20 sets a target lateral acceleration gain that is a target vehicle characteristic according to the following equation (8).

here,
g _y0: lateral acceleration gain v _s: is a vehicle speed for switching the target characteristic.

  Thus, the electronic control unit 20 sets a constant target yaw rate gain as a target vehicle characteristic in a low speed range of 70 km / h or less, and a constant target lateral acceleration in a high speed range exceeding 70 km / h. Set the gain. The target lateral acceleration gain is not limited to a constant value, and may be a value that increases with a slight gradient as shown in FIG.

(Estimation of real-time yaw rate gain and real-time lateral acceleration gain)
On the other hand, the electronic control unit 20 estimates the real-time yaw rate gain generated in the real-time vehicle by dividing the steering angle detected by the steering angle sensor 12 from the yaw rate detected by the yaw rate sensor 13. Further, the electronic control unit 20 removes the steering angle detected by the steering angle sensor 12 from the lateral acceleration detected by the lateral acceleration sensor 14, thereby obtaining the real-time lateral acceleration gain generated in the real-time vehicle. presume.

(Control of steering actuator)
When the vehicle speed detected by the vehicle speed sensor 11 is 70 km / h or less, the electronic control unit 20 compares the target yaw rate gain with the real time yaw rate gain so that the real time yaw rate gain approaches the target yaw rate gain. 30 is controlled.

  Further, when the vehicle speed detected by the vehicle speed sensor 11 exceeds 70 km / h, the electronic control unit 20 compares the target lateral acceleration gain with the real-time lateral acceleration gain, and the real-time lateral acceleration gain becomes the target lateral acceleration gain. The steering actuator 30 is controlled so as to approach.

  As described above, the steering control device according to the present invention sets a constant target yaw rate gain as the target vehicle characteristic when the vehicle speed is 70 km / h or less, and controls the steering actuator 30 so as to approach the target yaw rate gain. . Further, when the vehicle speed exceeds 70 km / h, the steering control device sets a constant target lateral acceleration gain as the target vehicle characteristic, and controls the steering actuator 30 so as to approach the target lateral acceleration gain. As a result, the steering control device sets the target vehicle characteristic corresponding to the driver's sensation characteristic and controls the steering, so that the controllability and stability of the vehicle can be improved.

  In the present embodiment, the boundary between the low speed region and the high speed region is described as 70 km / h. However, the boundary between the low speed region and the high speed region is not limited to this.

  FIGS. 6A to 6D are diagrams showing the yaw rate gain with respect to the vehicle speed for each subject.

  The figure shows an example of a result obtained by examining what kind of yaw gain is desirable at each vehicle speed through vehicle experiments. Both subjects have desirable characteristics such that the yaw gain is constant in the low speed range and the yaw gain decreases in accordance with the vehicle speed in the high speed range.

  The vehicle speed at which the characteristic is switched varies depending on the subject and is in the range of about 60 to 100 [km / h]. According to FIG. 6, the applicable range is about 60 [km / h] on the low speed side, up to about 100 [km / h] on the high speed side, and preferably 70 to 80 [km / h].

  Note that the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can also be applied to a design modified within the scope of the claims.

It is a figure which shows the sensitivity characteristic of the driver in the plane motion (yaw motion, lateral motion) of a vehicle. It is a figure which shows the movement recognition characteristic of a planar movement. It is a figure which shows (A) yaw rate gain and (B) lateral acceleration gain as the target vehicle characteristic with respect to a vehicle speed. It is a block diagram which shows the steering control apparatus which concerns on embodiment of this invention. It is a figure which shows the block diagram regarding the transfer function of a steering control apparatus. It is a figure which shows the yaw rate gain with respect to a vehicle speed.

Explanation of symbols

11 Vehicle speed sensor 12 Steering angle sensor 13 Yaw rate sensor 14 Lateral acceleration sensor 20 Electronic control unit 30 Steering actuator

Claims (5)

Vehicle speed detection means for detecting the vehicle speed;
Target vehicle characteristic setting means for setting a target lateral acceleration gain as a target vehicle characteristic based on the vehicle speed detected by the vehicle speed detection means;
Steering control means for controlling steering of at least one of the front wheels and the rear wheels so that the vehicle motion state approaches the target vehicle characteristic set by the target vehicle characteristic setting means;
A steering control device comprising: The target vehicle characteristic setting means sets a contribution rate of a target yaw rate gain to be large when the vehicle speed is a predetermined value or less based on the vehicle speed detected by the vehicle speed detection means, and the vehicle speed exceeds the predetermined value. Set the contribution rate of the target lateral acceleration gain to
The steering control means controls the steering amount of at least one of the front wheels and the rear wheels so that the vehicle motion state approaches the target yaw rate gain when the vehicle speed is a predetermined value or less, and the vehicle speed exceeds a predetermined value. 2. The steering control device according to claim 1, wherein the steering control device controls steering of at least one of a front wheel and a rear wheel so that the vehicle motion state approaches the target lateral acceleration gain. Steering angle detection means for detecting the steering angle;
A yaw rate detection means for detecting the yaw rate;
A lateral acceleration detecting means for detecting the lateral acceleration,
The steering control means estimates a real time yaw rate gain obtained by dividing the yaw rate detected by the yaw rate detection means by the steering angle detected by the steering angle detection means when the vehicle speed is a predetermined value or less, and the real time The steering amount of at least one of the front wheels and the rear wheels is controlled so that the yaw rate gain approaches the target yaw rate gain, and when the vehicle speed exceeds a predetermined value, the lateral acceleration detected by the lateral acceleration detecting means is steered. A real-time lateral acceleration gain divided by a steering angle detected by an angle detection means is estimated, and steering of at least one of the front wheels and the rear wheels is controlled so that the real-time lateral acceleration gain approaches the target lateral acceleration gain. Item 3. The steering control device according to Item 2. The steering control device according to claim 2 or 3, wherein the predetermined value is a speed within a range of 60 to 100 km / h. The steering control device according to claim 3, wherein the predetermined value is a speed within a range of 70 to 80 km / h.

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