JP2009137512A - Rear wheel steering angle control device and rear wheel steering angle control method for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate impairing of natural driving feeling even if longitudinal acceleration/deceleration of a vehicle body is rapidly varied by pitching motion, rapid acceleration, rapid deceleration or the like of the vehicle body in a rear wheel steering angle control device for a vehicle for controlling a rear wheel steering angle such that normative yaw rate transmission characteristic is attained based on a stability factor being subjected to correction of longitudinal acceleration/deceleration. <P>SOLUTION: In the rear wheel steering angle control for the vehicle, the stability factor used for a rear wheel steering angle control regulation is corrected according to longitudinal acceleration/deceleration of the vehicle body to make it proper, and the rear wheel steering angle is controlled based on the stability factor being subjected to correction of longitudinal acceleration/deceleration so as to attain the normative yaw rate transmission characteristic. Restriction is added to a variation amount per a unit time of an acceleration/deceleration correction value Aα of the stability factor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rear wheel steering angle control device and a rear wheel steering angle control method for a vehicle, and particularly includes a requirement of a stability factor that is corrected according to the longitudinal acceleration / deceleration of a vehicle body in a four-wheel vehicle such as an automobile. The present invention relates to a rear wheel steering angle control device and a rear wheel steering angle control method for controlling a rear wheel steering angle.

  In a four-wheeled vehicle such as an automobile, a hub carrier (knuckle) that supports the left and right rear wheels is connected to the vehicle body including an electric or hydraulic linear actuator on the way, and the rear wheel A rear wheel steering device that changes the toe angle separately on the left and right is known (for example, Patent Document 1).

  As a steering angle control law for such a rear wheel steering device, the yaw rate transmission characteristic to be realized with respect to the actual steering angle of the front wheel, that is, the standard yaw rate transmission characteristic is calculated including the stability factor, and the actual steering angle and vehicle speed of the front wheel are calculated. And a control law for calculating a rear wheel rudder angle control target value based on the standard yaw rate transmission characteristic and controlling the rear wheel rudder angle (toe angle) to be the rear wheel rudder angle control target value. .

Stability factor is an index representing the degree of understeer-oversteer characteristics (US-OS characteristics) when turning at a constant rudder angle, front wheel cornering power, rear wheel cornering power, distance from vehicle center of gravity to front wheel axle, It is determined by the distance from the center of gravity of the vehicle to the rear axle.
Japanese Patent Laid-Open No. 9-30438

  The stability factor is a constant when traveling at a constant speed, but when accompanied by acceleration / deceleration in the longitudinal direction of the vehicle body, the longitudinal load movement occurs in the vehicle body, and the cornering power of the front and rear wheels changes. It changes with the longitudinal acceleration / deceleration of the car body.

  For this reason, the stability factor used in the above-mentioned rear wheel steering angle control law is corrected and optimized according to the longitudinal acceleration / deceleration of the vehicle body, and the standard yaw rate transmission is performed based on the stability factor corrected for longitudinal acceleration / deceleration. In order to realize the characteristics, it is considered to control the rear wheel steering angle.

  When the vehicle body pitches, the longitudinal acceleration / deceleration of the vehicle body changes abruptly. Further, the front-rear acceleration / deceleration of the vehicle body also changes abruptly when the accelerator pedal and the brake pedal are stepped on or returned. In such a case, the value of the stability factor that is corrected for longitudinal acceleration / deceleration also changes abruptly, and the standard yaw rate transmission characteristic that is calculated including the stability factor that is corrected for longitudinal acceleration / deceleration also changes abruptly. For this reason, when the longitudinal acceleration / deceleration of the vehicle body changes suddenly due to the pitching motion of the vehicle body, the rear wheel rudder angle (toe angle) that is controlled to achieve the standard yaw rate transmission characteristics changes rapidly, and natural driving Sense is impaired.

  The problem to be solved by the present invention is to control the rear wheel rudder angle in order to realize the standard yaw rate transmission characteristic based on the stability factor corrected for longitudinal acceleration / deceleration. In other words, even if the longitudinal acceleration / deceleration of the vehicle body changes suddenly due to sudden deceleration or the like, the natural driving feeling is impaired.

  The vehicle rear wheel rudder angle control device according to the present invention corrects and stabilizes the stability factor used in the rear wheel rudder angle control law in accordance with the longitudinal acceleration / deceleration of the vehicle body. A vehicle rear wheel rudder angle control device that controls a rear wheel rudder angle so that a standard yaw rate transmission characteristic is realized, wherein a change amount per unit time of an acceleration / deceleration correction value of the stability factor is determined. Has a means to add restrictions.

  A vehicle rear wheel steering angle control device according to the present invention calculates a reference yaw rate transmission characteristic including a stability factor, and controls a rear wheel steering angle based on an actual steering angle of a front wheel, a vehicle speed, and the reference yaw rate transmission characteristic. A vehicle rear wheel rudder angle control device that calculates a target value and controls the rear wheel rudder angle to be the rear wheel rudder angle control target value, and detects front / rear acceleration / deceleration detection for detecting front / rear acceleration / deceleration of the vehicle body And a stability factor acceleration / deceleration for calculating an acceleration / deceleration correction value for correcting the stability factor used for calculating the reference yaw rate transmission characteristic according to the longitudinal acceleration / deceleration of the vehicle detected by the longitudinal acceleration / deceleration detecting means Correction value change amount restriction for restricting a change amount per unit time of the acceleration / deceleration correction value calculated by the correction value calculation means and the stability factor acceleration / deceleration correction value calculation means It has a stage.

  The vehicle rear wheel steering angle control device according to the present invention preferably includes an acceleration / deceleration correction value change amount calculating means for calculating an acceleration / deceleration correction value change amount per unit time of the acceleration / deceleration correction value. The change amount limiting means limits the change amount per unit time of the acceleration / deceleration correction value when the acceleration / deceleration correction value change amount calculated by the acceleration / deceleration correction value change amount calculating means is greater than or equal to a predetermined value.

  The vehicle rear wheel steering angle control device according to the present invention preferably includes front / rear acceleration / deceleration change amount calculating means for calculating a change amount of front / rear acceleration / deceleration per unit time of the front / rear acceleration / deceleration, and the correction value change amount restriction The means limits the amount of change per unit time of the acceleration / deceleration correction value when the amount of change in front / rear acceleration / deceleration calculated by the front / rear acceleration / deceleration change amount calculating means is equal to or greater than a predetermined value.

  In the vehicle rear wheel steering angle control method according to the present invention, the stability factor used in the rear wheel steering angle control law is corrected and optimized according to the longitudinal acceleration / deceleration of the vehicle body, and the stability factor of the longitudinal acceleration / deceleration correction is corrected. A vehicle rear wheel rudder angle control method for controlling a rear wheel rudder angle so that a standard yaw rate transmission characteristic is realized, wherein a change amount per unit time of an acceleration / deceleration correction value of the stability factor is determined. Add restrictions.

  According to the rear wheel steering angle control device and the rear wheel steering angle control method of the present invention, the amount of change per unit time of the stability factor acceleration / deceleration correction value is limited. Even if the front / rear acceleration / deceleration changes rapidly, the standard yaw rate transmission characteristics calculated including the stability factor corrected for front / rear acceleration / deceleration, the rear wheel rudder angle (toe angle) does not change abruptly, A natural driving sensation can be achieved during pitching, sudden acceleration, and sudden deceleration.

  Hereinafter, embodiments of a rear wheel steering angle control device and a rear wheel steering angle control method according to the present invention will be described with reference to FIGS.

  First, a four-wheeled vehicle to which a rear wheel steering angle control device and a rear wheel steering angle control method according to the present invention are applied will be described with reference to FIG.

  The four-wheel vehicle 1 of the present embodiment includes left and right front wheels 4L and 4R and left and right rear wheels 6L and 6R. The front wheels 4L and 4R are fitted with tires 3L and 3R, respectively, suspended by the vehicle body 2 by left and right front suspensions 7L and 7R, and attached to the vehicle body 2 by knuckles 7aL and 7aR so as to be turnable. The rear wheels 6L and 6 are fitted with tires 5L and 5R, respectively, suspended by the vehicle body 2 by left and right rear suspensions 8L and 8R, and attached to the vehicle body 2 by knuckles 8aL and 8aR so as to be turnable.

  The four-wheel vehicle 1 includes a front wheel steering device 10 that directly steers the left and right front wheels 4L and 4R by steering the steering wheel 11. The front wheel steering device 10 includes a pinion 13 that is integrally connected to a steering wheel 11 via a steering shaft 12 and a tooth portion that meshes with the pinion 13 so as to be reciprocally movable in the vehicle width direction. A rack and pinion mechanism having a rack shaft 14 is also provided. Both ends of the rack shaft 14 are connected to the left and right knuckles 7aL and 7aR via tie rods 15. The left and right front wheels 4L, 4R are steered (turned) when the rack shaft 14 is moved in the vehicle width direction by the rotation operation of the steering wheel 11.

  The steering shaft 12 is provided with a steering angle sensor 26 for detecting the steering angle of the steering wheel 11 corresponding to the actual steering angle δr of the front wheels 4L, 4R. Thereafter, the steering angle sensor 26 outputs a sensor signal indicating the actual front wheel steering angle δr.

  The four-wheeled vehicle 1 is a rear wheel steering device (rear wheel toe angle varying device) 20 having one end connected to the vehicle body 2 and the other end connected to the knuckle 8aL of the left rear wheel 6L. And a right linear actuator 21R having one end connected to the vehicle body 2 and the other end connected to the knuckle 8aR of the right rear wheel 6R. The left and right linear actuators 21L and 21R are electrically operated or hydraulic, and expand and contract by a linear operation to individually change the toe angles of the left and right rear wheels 6L and 6R. In the rear wheel steering device 20 configured as described above, the toe angles of the left and right rear wheels 6L and 6R are controlled by the left and right linear actuators 21L and 21R in the same direction in the opposite phase to the front wheel steering direction. Thus, the rear wheel can be steered.

The left and right linear actuators 21L and 21R are controlled by a rear wheel steering control device (ECU) 30. The rear wheel steering control device 30 is of an electronic control type including a microcomputer, and receives a sensor signal indicating the actual front wheel steering angle δr from the steering angle sensor 26 and a vehicle speed sensor 24 that detects the vehicle speed V of the four-wheeled vehicle 1. The sensor signal indicating the vehicle speed V is input from the front / rear acceleration / deceleration sensor 25 for detecting the longitudinal acceleration / deceleration αχ of the vehicle body 2 and the sensor signal indicating the longitudinal acceleration / deceleration αχ of the vehicle body 2 is input. The control target rear steering angle δr ^* is calculated according to the control law.

The ECU 30 converts the control target rear steering angle δr ^* into the control target stroke amount S ^* of the linear actuators 21L and 21R, and uses the stroke sensors 23L and 23R provided in the linear actuators 21L and 21R to execute the actual operations of the linear actuators 21L and 21R. Sensor signals indicating the stroke amounts SL and SR are input so that the control deviation between the control target stroke amount S ^* and the actual stroke amount SL and the control deviation between the control target stroke amount S ^* and the actual stroke amount SR are each zero. In addition, a control target signal is output to each of the linear actuators 21L and 21R.

Thus, feedback control is performed so that the toe angles (rear wheel steering angles) of the left and right rear wheels 6L and 6R become the target rear steering angle (rear wheel steering angle control target value) δr ^* .

  Next, details of the rear wheel steering angle control device 30 according to the present embodiment will be described with reference to FIG. The rear wheel steering angle control device 30 includes a front (front wheel) steering transmission characteristic calculation unit 31, a rear (rear wheel) steering transmission characteristic calculation unit 32, a reference yaw rate transmission characteristic calculation unit 33, and a stability factor acceleration / deceleration correction value. A calculation unit 34, a stability factor correction value change amount limiting unit 35, an acceleration / deceleration correction value change amount calculation unit 36, and a control target rear steering angle calculation unit 37 are included.

When the front wheel steering angle (actual steering angle) is δf and the rear wheel steering angle (actual steering angle) is δr, the yaw rate characteristic γ of the vehicle (four-wheeled vehicle) 1 with respect to the front wheel steering angle δf and the rear wheel steering angle δr is It is represented by Formula (1).
γ = (Gf · δf) − (Gr · δr) (1)
However, Gf is a front steering transmission characteristic, and Gr is a rear steering transmission characteristic.

Assuming that the yaw rate characteristic to be realized with respect to the front wheel steering angle δf, that is, the reference yaw rate transmission characteristic, is set to Gideal, if the rear wheel steering angle δr is set such that γideal = (Gideal · δf) and γideal = γ, the reference yaw rate transmission is performed. The characteristic Gideal can be realized. Based on this, the rear wheel steering angle control device 30 performs the following arithmetic processing to calculate the control target rear steering angle δr ^* that realizes the reference yaw rate transmission characteristic Gideal.

The front steering transfer characteristic calculation unit 31 inputs a sensor signal indicating the front wheel actual steering angle δr from the steering angle sensor 26 and a sensor signal indicating the vehicle speed V from the vehicle speed sensor 24, respectively, as primary and secondary transfer functions, The front steering transmission characteristic Gf is calculated by the following equation (2).
Gf = K (af · s + 1) / (b ₁ · s ² + b ₂ · s + 1) (2)

The rear steering transmission characteristic calculation unit 32 inputs a sensor signal indicating the front wheel actual steering angle δr from the steering angle sensor 26 and a sensor signal indicating the vehicle speed V from the vehicle speed sensor 24, respectively, as primary and secondary transfer functions, The rear steering transmission characteristic Gr is calculated by the following equation (3).
Gr = K (ar · s + 1) / (b ₁ · s ² + b ₂ · s + 1) (3)

The standard yaw rate transfer characteristic calculating unit 33 calculates a sensor signal indicating the front steering angle δr from the steering angle sensor 26 and a sensor signal indicating the vehicle speed V from the vehicle speed sensor 24 by the stability factor acceleration / deceleration correction value calculating unit 34. Each of the signals indicating the stability factor acceleration / deceleration correction value Aα is input, and the standard yaw rate transfer characteristic Gideal is calculated by the following equation (4).
Ideal = (V / L) {1 / (1 + A · Aα · V ² ) (c ₁ · s + 1) / (d ₂ · s ² + d ₁ · s + 1)} (4)

Each parameter of the equations (2) to (4) is calculated by the following equations (5) to (10).
K = (V / L) {1 / (1 + A · V ² )} (5)
A = − (m / L ² ) {(Lf · Kf−Lr · Kr) / (Kf · Kr)} (6)
af = (V / L) (m · Lf / Kr) (7)
ar = (V / L) (m · Lr / Kf) (8)
b ₁ = K (m · V · I) / (Kf · Kr · L) (9)
b ₂ = K {m (Lf · Kf ² + Lr · Kr ² ) + I (Kf + Kr)} / (Kf · Kr · L) (10)
Where m: vehicle mass L: wheel base Lf: center of gravity-front wheel axle distance Lr: center of gravity-rear wheel axle distance Kf: front wheel cornering power Kr: rear wheel cornering power V: body speed s: Laplace operator A: steady Stability factor in state Aα: Stability factor acceleration / deceleration correction value I: Vehicle yaw inertial rotation mass c ₁ , d ₁ , d ₂ : Coefficients to be set arbitrarily

The control target rear steering angle calculation unit 37 receives a signal indicating the front steering transmission characteristic Gf from the front steering transmission characteristic calculation unit 31, a signal indicating the rear steering transmission characteristic Gr from the rear steering transmission characteristic calculation unit 32, and a reference yaw rate transmission characteristic. A signal indicating the standard yaw rate transfer characteristic Gideal is input from the calculation unit 33 and a sensor signal indicating the actual front wheel steering angle δr is input from the steering angle sensor 26, and the control target rear steering angle δr ^* is calculated by the following equation (11).
δr ^* = Gr ⁻¹ (Gf−Gideal) δf (11)

  As described above, the reference yaw rate transfer characteristic calculation unit 33 corrects the stability factor A used for the rear wheel steering angle control law according to the longitudinal acceleration / deceleration αχ of the vehicle body 2 with the stability factor acceleration / deceleration correction value Aα. The standard yaw rate transfer characteristic Gideal is calculated using the stabilized stability factor (A · Aα).

  The stability factor acceleration / deceleration correction value calculation unit 34 receives a sensor signal indicating the longitudinal acceleration / deceleration αχ of the vehicle body 2 from the longitudinal acceleration / deceleration sensor 25, and calculates the stability factor acceleration / deceleration correction value Aα by the following equation (12). To do.

Aα = (Lf · Kf−Lr · Kr) / {{(Lf / (Lf + h · αχ)} Lf · Kf − {(Lr / Lr + h · αχ) Lr · Kr}} (12)
Where h: height of the center of gravity

What is important in the present invention is the unit time of the acceleration / deceleration correction value Aα of the stability factor A in order to avoid a sudden change in the reference yaw rate transfer characteristic Gideal, and in other words, a sudden change in the control target rear steering angle δr ^*. To limit the amount of change per hit.

  On the other hand, the acceleration / deceleration correction value change amount calculation unit 36 per unit time of the acceleration / deceleration correction value Aα by differential calculation of the acceleration / deceleration correction value Aα calculated by the stability factor acceleration / deceleration correction value calculation unit 34. The acceleration / deceleration correction value change amount is calculated, and the calculation result is passed to the stability factor correction value change amount limiting unit 35.

  The stability factor correction value change amount limiting unit 35 receives a signal indicating the stability factor acceleration / deceleration correction value Aα from the stability factor acceleration / deceleration correction value calculation unit 34, and is calculated by the acceleration / deceleration correction value change amount calculation unit 36. When the acceleration / deceleration correction value change amount per unit time of the acceleration / deceleration correction value Aα is less than a predetermined value, the stability factor acceleration / deceleration correction value Aα from the stability factor acceleration / deceleration correction value calculation unit 34 is used as it is. In contrast, when the amount of change in the acceleration / deceleration correction value Aα per unit time of the acceleration / deceleration correction value Aα is equal to or greater than a predetermined value, the reference yaw rate transfer characteristic calculation unit 33 receives the acceleration / deceleration correction value Aα per unit time. The change amount is limited, and the acceleration / deceleration correction value Aα with the change amount limited is passed to the reference yaw rate transfer characteristic calculation unit 33.

  As a result, the stability factor (A) corrected for longitudinal acceleration / deceleration is corrected even if the acceleration / deceleration is performed suddenly by the pitching motion of the vehicle body 2, the accelerator pedal, or the brake pedal being suddenly depressed or returned.・ Standard yaw rate transmission characteristic Gideal calculated including Aα), and the rear wheel rudder angle (toe angle) does not change abruptly, and it feels natural even during pitching, sudden acceleration, and sudden deceleration Can be realized.

  In the above-described embodiment, the acceleration / deceleration correction value change amount per unit time of the acceleration / deceleration correction value Aα is calculated to limit the change amount per unit time of the acceleration / deceleration correction value Aα. Acceleration / deceleration correction calculated by the stability factor acceleration / deceleration correction value calculation unit 34 by limiting the amount of change per unit time of the front / rear acceleration / deceleration αχ input to the deceleration correction value calculation unit 34. A limit may be added to the amount of change per unit time of the value Aα.

  This embodiment will be described with reference to FIG. 3, parts corresponding to those in FIG. 2 are denoted by the same reference numerals as those in FIG. 1, and description thereof is omitted.

  In this embodiment, the front-rear acceleration / deceleration change amount calculation unit 38 that calculates the amount of change in front-rear acceleration / deceleration per unit time of the front-rear acceleration / deceleration αχ detected by the front-rear acceleration / deceleration sensor 25, and the front-rear acceleration / deceleration change amount calculation unit 38 When the calculated longitudinal acceleration / deceleration change amount per unit time is greater than or equal to a predetermined value, the longitudinal acceleration / deceleration change amount limiting unit 39 that limits the change amount per unit time of the longitudinal acceleration / deceleration change amount is provided. The longitudinal acceleration / deceleration αχ detected by the sensor 25 is supplied to the stability factor acceleration / deceleration correction value calculation unit 34 through the longitudinal acceleration / deceleration change amount limiting unit 39.

  Thereby, the longitudinal acceleration / deceleration variation limiting unit 39 functions as a stability factor correction value variation limiting unit, and when the longitudinal acceleration / deceleration variation calculated by the longitudinal acceleration / deceleration variation calculating unit 38 is greater than or equal to a predetermined value. Therefore, the amount of change per unit time of the acceleration / deceleration correction value Aα calculated by the stability factor acceleration / deceleration correction value calculation unit 34 is limited.

1 is an overall configuration diagram showing one embodiment of a four-wheeled vehicle to which a rear wheel steering angle control device and a rear wheel steering angle control method according to the present invention are applied. 1 is a block diagram showing one embodiment of a rear wheel steering angle control device of a vehicle according to the present invention. It is a block diagram which shows other embodiment of the rear-wheel steering angle control apparatus of the vehicle by this invention.

Explanation of symbols

4L, 4R Front wheel 6L, 6R Rear wheel 21L, 21R Linear actuator 24 Vehicle speed sensor 25 Front / rear acceleration / deceleration sensor 26 Steering angle sensor 30 Rear wheel steering angle control device 31 Front steering transmission characteristic calculation unit 32 Rear steering transmission characteristic calculation unit 33 Reference yaw rate Transfer characteristic calculation unit 34 Stability factor acceleration / deceleration correction value calculation unit 35 Stability factor correction value change amount limiting unit 36 Acceleration / deceleration correction value change amount calculation unit 37 Control target rear steering angle calculation unit 38 Front / rear acceleration / deceleration change amount calculation unit 39 Front / rear acceleration / deceleration variation limiter

Claims (5)

The stability factor used in the rear wheel steering angle control law is corrected and optimized according to the longitudinal acceleration / deceleration of the vehicle body, and the standard yaw rate transmission characteristic is realized based on the stability factor corrected for longitudinal acceleration / deceleration A vehicle rear wheel steering angle control device for controlling the rear wheel steering angle as much as possible,
A vehicle rear wheel steering angle control device comprising means for limiting a change amount per unit time of the acceleration / deceleration correction value of the stability factor. The standard yaw rate transmission characteristic is calculated including the stability factor, the control target value of the rear wheel rudder angle is calculated based on the actual steering angle of the front wheel, the vehicle speed, and the standard yaw rate transmission characteristic. A rear wheel rudder angle control device for controlling a rear wheel rudder angle control target value,
Front / rear acceleration / deceleration detecting means for detecting front / rear acceleration / deceleration of the vehicle body;
Stability factor acceleration / deceleration correction value calculation for calculating an acceleration / deceleration correction value for correcting the stability factor used for calculation of the reference yaw rate transmission characteristic according to the longitudinal acceleration / deceleration of the vehicle detected by the longitudinal acceleration / deceleration detection means Means,
Correction value change amount limiting means for limiting a change amount per unit time of the acceleration / deceleration correction value calculated by the stability factor acceleration / deceleration correction value calculation means;
A rear wheel steering angle control device for a vehicle. An acceleration / deceleration correction value change amount calculating means for calculating an acceleration / deceleration correction value change amount per unit time of the acceleration / deceleration correction value;
When the acceleration / deceleration correction value change amount calculated by the acceleration / deceleration correction value change amount calculating means is greater than or equal to a predetermined value, the correction value change amount limiting means sets the change amount per unit time of the acceleration / deceleration correction value. The rear-wheel steering angle control device for a vehicle according to claim 2 to be limited. A front / rear acceleration / deceleration change amount calculating means for calculating a front / rear acceleration / deceleration change amount per unit time of the front / rear acceleration / deceleration;
The correction value change amount limiting means limits a change amount per unit time of the acceleration / deceleration correction value when the front / rear acceleration / deceleration change amount calculated by the front / rear acceleration / deceleration change amount calculating means is a predetermined value or more. The rear-wheel steering angle control device for a vehicle according to claim 2. The stability factor used in the rear wheel steering angle control law is corrected and optimized according to the longitudinal acceleration / deceleration of the vehicle body, and the standard yaw rate transmission characteristic is realized based on the stability factor corrected for longitudinal acceleration / deceleration A vehicle rear wheel steering angle control method for controlling the rear wheel steering angle as much as possible,
A rear wheel steering angle control method for limiting a change amount per unit time of an acceleration / deceleration correction value of the stability factor.

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