JP2010095153A - Steering angle ratio variable control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering angle variable control device which does not apply a heavy steering burden on a driver even if the driver performs accelerator operation or braking operation during turning movement. <P>SOLUTION: A VGS (variable gear ratio steering) control device 10 performs the variable control of a VGS ratio n(V) between a steering angle θ<SB>s</SB>of a steering wheel and a target pinion angle θ<SB>p</SB>for steering front wheels according to vehicle speed V. In the VGS control device, a correction coefficient setting part 15 sets a correction coefficient k after setting a correction coefficient k<SB>1</SB>corresponding to longitudinal acceleration G in the case of holding the steering wheel at a constant angle during turning movement, and a correction coefficient k<SB>2</SB>corresponding to the longitudinal acceleration G in the case of transiently steering the steering wheel during turning movement. A VGS ratio correction part 13 multiplies the VGS ratio n(V) set by a VGS ratio setting part 11 by the correction coefficient k, thereby preventing the change of a yaw rate caused by the longitudinal acceleration G. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a steering angle ratio variable control device that variably controls a ratio between a steering angle of a steering wheel and a steering angle of a steering wheel in accordance with a vehicle speed, and more specifically, push under / tuck-in at the time of acceleration / deceleration of a vehicle. The present invention relates to a technology that suppresses and improves the stability of turning behavior.

  In recent years, a steering angle ratio variable device that can change the ratio of the steering angle of the steering wheel and the steering angle of the steering wheel (see, for example, Patent Document 1), or mechanically separating the steering system and the steering wheel. A variety of so-called steer-by-wire devices (see, for example, Patent Document 2) that steer front wheels with an actuator or the like according to the steering angle of the steering wheel have been developed, and vehicles equipped with these have been put on the market. .

  In such a steering angle ratio variable control device that variably controls the ratio between the steering angle of the steering wheel and the steering angle of the steering wheel, the ratio is generally set according to the vehicle speed. The turning angle of the steering wheel is set to be relatively small with respect to the steering angle, so that stable turning behavior is ensured, and the steering wheel turning angle is relatively large with respect to the steering angle of the steering wheel during low-speed driving. By setting, agile turning behavior is ensured.

On the other hand, the steering angle of the steering wheel with respect to the steering angle of the steering wheel is variably controlled so that the yaw rate gain (yaw rate / steering angle) of the vehicle is substantially constant, and the lateral acceleration of the vehicle body is limited by the steering wheel turning. A vehicle steering control device or the like that increases the steering reaction force of the steering wheel when exceeding is proposed (see Patent Document 3).
Japanese Patent Laid-Open No. 06-227422 JP 2003-165460 A JP-A-10-315998

  By the way, when the driver performs an accelerator operation or a brake operation during turning, the cornering force of the tire changes with the load change between the front wheels and the rear wheels. Even if it is held, it is known that a phenomenon that the vehicle trajectory swells outside the turn (push under / power under) occurs during acceleration, and a phenomenon that the vehicle trajectory wraps inside the turn (tuck-in) occurs during deceleration. These phenomena are particularly prominent in FF vehicles.

  However, the conventional variable steering angle ratio control device cannot prevent the occurrence of such a phenomenon, and if the accelerator operation or the brake operation is performed during turning, the driver can perform a desired travel locus (for example, a constant travel path). In order to maintain the turning radius during a fast turn, the steering steering must be finely adjusted, and the steering burden on the driver is heavy.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a variable steering angle control device that does not place an excessive steering burden on a driver even if an accelerator operation or a brake operation is performed during turning. .

  In order to solve the above-described problems, the present invention provides a steering angle ratio variable control device that variably controls the ratio of the steering angle of the steering wheel and the steering angle of the steering wheel according to the vehicle speed, and corrects it according to the longitudinal acceleration of the vehicle. A value is set, and the ratio is corrected using the correction value.

  In the steering angle ratio variable control device having the above configuration, when the change speed of the steering angle is smaller than a first predetermined value, the first correction value is set so that the yaw rate change due to the change in the longitudinal acceleration does not occur, The ratio may be corrected using the first correction value.

  In the steering angle ratio variable control device having the above-described configuration, when the change speed of the steering angle is larger than a second predetermined value, the second correction value is set so that the yaw rate change due to the change in the longitudinal acceleration does not occur. In addition, the ratio may be corrected using the second correction value.

  Furthermore, in the steering angle ratio variable control device having the above configuration, when the change speed of the steering angle is smaller than a first predetermined value, the first correction value is set so that the yaw rate change due to the change in the longitudinal acceleration does not occur. When the change speed of the steering angle is larger than a second predetermined value, a second correction value is set so that the yaw rate change due to the change of the longitudinal acceleration does not occur, and the change speed of the steering angle is the first change speed. When the value is between the predetermined value and the second predetermined value, the first correction value and the second correction value are weighted based on the change speed of the steering angle. The ratio may be corrected using a correction value.

  According to the present invention, the ratio of the steering angle to the turning angle is corrected according to the longitudinal acceleration of the vehicle, so that the steering burden on the driver can be reduced even if the accelerator operation or the brake operation is performed during turning. can do.

  Further, when the change speed of the steering angle is smaller than the first predetermined value, that is, when the steering wheel is hardly steered, the steering angle and the turning angle are set so that the yaw rate change due to the change in the longitudinal acceleration does not occur. By correcting the ratio, even if an accelerator operation or a brake operation is performed during turning, push-under or tack-in is suppressed, and the steering burden on the driver can be effectively reduced.

  In addition, when the change speed of the steering angle is larger than the second predetermined value, that is, when the steering wheel is steered quickly, the yaw rate change due to the change in the longitudinal acceleration is not caused except for the steering operation. Further, by correcting the ratio between the steering angle and the turning angle, push-under and tuck-in are suppressed as described above, and the steering burden on the driver can be effectively reduced.

  Further, when the change speed of the steering angle is between the first predetermined value and the second predetermined value, the first correction value and the second correction value are weighted based on the change speed of the steering angle. By correcting the ratio using the correction value obtained by performing the adjustment, push-under and tuck-in during turning are suppressed more effectively regardless of the change speed of the steering angle, and the steering burden on the driver is reduced. Can be further reduced.

<< First Embodiment >>
Hereinafter, a first embodiment of a VGS control device 10 (variable steering angle ratio control device) that variably controls a gear ratio of a variable gear ratio steering (hereinafter referred to as VGS (Variable Gear ratio Steering)) according to the present invention will be described with reference to the drawings. A form is demonstrated in detail. FIG. 1 is a block diagram showing a schematic configuration of a VGS control device 10 according to the first embodiment. Note that the VGS according to the embodiment is mounted on an FF four-wheeled vehicle, and by driving a rudder angle ratio variable means installed on a steering shaft by a motor, an input shaft coupled to the steering wheel and a front wheel (steering wheel) ) Is a device that variably controls the rudder angle ratio with the output shaft provided with a pinion that steers. Since the steering angle ratio varying means is a well-known technique, a description of the configuration of the mechanical system is omitted here.

The VGS control device 10 sets a VGS ratio n (V) (ratio θ _s / θ _p ) between the steering angle θ _{s of the} steering wheel and the target pinion angle (steering wheel turning angle) θ _p according to the vehicle speed V. and VGS ratio setting unit 11, a correction coefficient setting unit 12 for setting a correction coefficient _{k 1} for VGS ratio n (V) in accordance with the longitudinal acceleration G acting on the vehicle speed V and the vehicle body, the correction to the VGS ratio n (V) A VGS ratio correction unit 13 that calculates a VGS ratio n ′ (V) corresponding to the longitudinal acceleration G by multiplying the coefficient k ₁ , and a steering angle θ _{s with} respect to the VGS ratio n ′ (V) corresponding to the longitudinal acceleration G. and a target pinion angle calculating section 14 for calculating a target pinion angle theta _p by dividing.

The VGS ratio setting unit 11 sets the VGS ratio n (V) corresponding to the vehicle speed V by referring to the map shown in FIG. 2 in which the optimum gear ratio having the vehicle speed V as an address is set in advance. VGS ratio n (V), the quick ratio to be 1 or less in the low vehicle speed range, i.e., it is set to the ratio of the pinion angle theta _p increases with respect to the steering angle theta _s, 1 or more values in the high vehicle speed range become throw ratio, i.e., pinion angle theta _p is set to be smaller ratio to the steering angle theta _s.

FIG. 3 is a block diagram showing a schematic configuration of the correction coefficient setting unit 12. The correction coefficient setting unit 12 refers to a predetermined map based on data measured or calculated in advance, and sets a front wheel tire cornering power Kf and a rear wheel tire cornering power Kr corresponding to the vehicle speed V. 21, a stability factor A calculation unit 22 that calculates a stability factor A according to the vehicle speed V based on the front wheel tire cornering power Kf and the rear wheel tire cornering power Kr, and a predetermined value based on data measured or calculated in advance. The cornering power K ′ setting unit 23 for setting the front wheel tire cornering power K′f and the rear tire cornering power K′r according to the vehicle speed V and the longitudinal acceleration G, and the front wheel tire cornering power K are referred to. 'f and rear wheel tire corner A stability factor A ′ calculating unit 24 that calculates a stability factor A ′ corresponding to the longitudinal acceleration G based on the driving power K′r, and a correction coefficient k ₁ based on the vehicle speed V and the stability factors A and A ′. It is comprised from the correction coefficient calculation part 25 which calculates.

但し、Ａ：スタビリティファクタ、ｍ：車体質量、ｌ：ホイールベース、ｌ_ｆ：車体重心−前軸間距離、ｌ_ｒ：車体重心−後軸間距離、Ｋ_ｆ：前輪タイヤコーナリングパワー、Ｋ_ｒ：後輪タイヤコーナリングパワー、である。 The stability factor A corresponding to the vehicle speed V is calculated based on the following equation.

However, A: Stability factor, m: Body mass, l: Wheel base, l _f : Distance between vehicle body center of gravity and front axle, l _r : Distance between vehicle body center of gravity and rear axle, K _f : Front wheel tire cornering power, K _r : Rear wheel tire cornering power.

  Further, the stability factor A ′ according to the longitudinal acceleration G is the value of Kf and Kr in the above equation (1), instead of the front tire cornering power Kf and the rear tire cornering power Kr according to the vehicle speed V. On the other hand, it is calculated by using the front wheel tire cornering power K′f and the rear wheel tire cornering power K′r obtained by multiplying each by an adjustment coefficient corresponding to the longitudinal acceleration G.

但し、Ｖ：車体速度、である。 Further, the correction coefficient k ₁ is calculated based on the following equation.

Where V: vehicle body speed.

ここで、

で表される。
但し、γ（ｓ）：車体ヨーレイト、δ（ｓ）：前輪舵角、ζ：減衰比、ω_ｎ：固有振動数、ｎ（Ｖ）：ＶＧＳレシオ、Ｉ：車体ヨー慣性モーメント、ｎ_ｐ：前輪舵角δとピニオン角θ_ｐとの比、である。 Here, the calculation basis of the above equation (2) will be described. The relationship between the vehicle body yaw rate and the front wheel rudder angle during steady circle turning, that is, when turning at a constant vehicle speed on a circumference with a constant radius is given by the following equation.

here,

It is represented by
Where γ (s): vehicle body yaw rate, δ (s): front wheel steering angle, ζ: damping ratio, ω _n : natural frequency, n (V): VGS ratio, I: vehicle body yaw moment of inertia, n _p : front wheel steering angle δ and the ratio between the pinion angle theta _p, a.

したがって、式（３）、式（１０）より、下式が求められる。

ここで、コーナー旋回時は操舵周波数ωが低いため、近似的に

とすると、式（１１）は下式のように整理される。

このとき、前後加速度Ｇによって車両にヨーレイト変化が生じないように、γ’（ｓ）＝γ（ｓ）、すなわち、左辺が１となるようにしたいので、前後加速度Ｇ発生時のＶＧＳレシオｎ’（Ｖ）は下式のようになる。

したがって、ＶＧＳレシオｎ（Ｖ）に前後加速度Ｇに応動する補正係数ｋ_１（（１＋Ａ’Ｖ^２）／（１＋ＡＶ^２））を掛ければ、前後加速度Ｇ発生時のＶＧＳレシオｎ’（Ｖ）が求められることになる。 Here, when the principle of correcting the VGS ratio when the steering wheel is held at a constant angle during turning (when the steering angular velocity is a first predetermined value (for example, 2 deg / sec) or less) is studied, steady circular turning The time yaw rate-front wheel rudder angle transfer function is given by the above equation (3). On the other hand, the transient yaw rate-front wheel steering angle transfer function when the longitudinal acceleration G is generated is given by the following equation. Note that “′” in the expression indicates a value when the longitudinal acceleration G is generated.

Therefore, the following expression is obtained from Expression (3) and Expression (10).

Here, since the steering frequency ω is low during corner turning,

Then, Formula (11) is rearranged as the following formula.

At this time, in order to prevent the yaw rate from changing due to the longitudinal acceleration G, γ ′ (s) = γ (s), that is, the left side is set to 1, so the VGS ratio n ′ when the longitudinal acceleration G is generated. (V) is as shown below.

Therefore, by multiplying the VGS ratio n (V) by the correction coefficient k ₁ ((1 + A′V ² ) / (1 + AV ² )) that responds to the longitudinal acceleration G, the VGS ratio n ′ (V) when the longitudinal acceleration G is generated is obtained. It will be required.

<Modified Embodiment 1>
Next, a modified embodiment 1 of the first embodiment will be described. FIG. 4 is a block diagram showing a schematic configuration of the correction coefficient setting unit 12 according to the first modified embodiment. In addition, about the element which performs the same process as 1st Embodiment, the same code | symbol is used and the overlapping description is abbreviate | omitted. As shown in FIG. 4, the correction coefficient setting unit 12 includes an adjustment coefficient setting unit 31 and a cornering power K ′ setting unit 32 instead of the cornering power K ′ setting unit 23 of FIG. 3.

  The adjustment coefficient setting unit 31 sets an adjustment coefficient for the front wheel tire cornering power K′f and the rear wheel tire cornering power K′r according to the longitudinal acceleration G based on the vehicle speed V and the longitudinal acceleration G. The adjustment coefficient corresponding to the longitudinal acceleration G is obtained by referring to measurement data or mapped data obtained by calculation in advance. The cornering power K ′ setting unit 32 multiplies the front wheel tire cornering power Kf and the rear wheel tire cornering power Kr set by the cornering power K setting unit 21 by an adjustment coefficient, respectively. A tire cornering power K′f and a rear wheel tire cornering power K′r are set. The stability factor A calculation unit 22, the stability factor A 'calculation unit 24, and the correction coefficient calculation unit 25 perform the same processing as in the first embodiment.

<Modified Embodiment 2>
Next, a modified embodiment 2 of the first embodiment will be described. FIG. 5 is a block diagram illustrating a schematic configuration of the correction coefficient setting unit 12 according to the second embodiment. The correction coefficient setting unit 12 includes a map correction coefficient setting unit 33. Map correction coefficient setting unit 33, based on the vehicle speed V and the longitudinal acceleration G, directly setting the correction coefficient k ₁ by referring to the map shown in FIG. The map shown in FIG. 6 is set as a correction coefficient map based on the vehicle speed V and the longitudinal acceleration G while confirming actual vehicle behavior by an actual vehicle test.

<< Second Embodiment >>
Next, in addition to the correction of the VGS ratio in the case where the steering wheel is steered at a certain angle during the turning, the steering wheel is transiently steered during the turning (the steering angular velocity is a second predetermined value ( For example, a second embodiment for correcting the VGS ratio in the case of 90 deg / sec or higher will be described. The same reference numerals are used for elements other than the correction coefficient setting unit 15 having different processing contents from those in FIG. 1, and the processing by these elements and the correction of the VGS ratio when the steering wheel is held at a constant angle during turning is described. Description is omitted.

  FIG. 7 is a block diagram showing a schematic configuration of the VGS control device 10 according to the second embodiment. The VGS control device 10 includes a correction coefficient setting unit 15 that sets a correction coefficient k for the VGS ratio based on the steering angular velocity, the longitudinal acceleration G, and the vehicle speed V, instead of the correction coefficient setting unit 12 of FIG.

FIG. 8 is a block diagram showing a schematic configuration of the correction coefficient setting unit 15. Correction coefficient setting unit 15, based on the vehicle speed V and the longitudinal acceleration G, the correction for the stationary steering to calculate a correction coefficient k ₁ for steady steering coefficient setting unit 12 (the same as the correction coefficient setting unit 12 shown in FIG. 3) Similarly, based on the vehicle speed V and the longitudinal acceleration G, a transient steering correction coefficient calculation unit 16 that calculates a transient steering correction coefficient k ₂ , a steady steering correction coefficient k ₁ , and a transient steering correction coefficient k ₂ and, based on the steering angular velocity (rate of change of the steering angle), and a correction coefficient adjusting unit 17 for calculating a correction coefficient k. Correction coefficient k ₂ is calculated based on the following equation.

このとき、前後加速度Ｇの変化によって車両のヨーレイトが変化しないように、γ’（ｓ）＝γ（ｓ）、すなわち、左辺が１となるようにしたいので、前後加速度Ｇ発生時のＶＧＳレシオｎ’（Ｖ）は下式のようになる。

したがって、ＶＧＳレシオｎ（Ｖ）に前後加速度Ｇに応動する補正係数ｋ_２（Ｋ_ｆ／Ｋ’_ｆ）を掛ければ、前後加速度Ｇ発生時のＶＧＳレシオｎ’（Ｖ）が求められることになる。 Here, the calculation basis of the above equation (15) will be described. The above formula (11) obtained from the above formulas (3) and (10) can also be used as the correction principle of the VGS ratio when the steering wheel is steered transiently during turning. When steering is actively performed during corner turning, since the value of s = jω increases, the equation (11) is arranged as the following equation.

At this time, γ ′ (s) = γ (s), that is, the left side is set to 1 so that the yaw rate of the vehicle does not change due to the change in the longitudinal acceleration G. Therefore, the VGS ratio n when the longitudinal acceleration G is generated. '(V) is as follows.

Therefore, by multiplying the VGS ratio n (V) by the correction coefficient k ₂ (K _f / K ′ _f ) that responds to the longitudinal acceleration G, the VGS ratio n ′ (V) when the longitudinal acceleration G is generated can be obtained. .

Based on the steering angular velocity, the correction coefficient adjustment unit 17 calculates the correction coefficient k by the following equation that weights the correction coefficient k ₁ for steady steering and the correction coefficient k ₂ for transient steering.
k = (1-w) × k ₁ + w × k ₂ (18)
Where w is a weighting factor.

The weighting coefficient w is obtained by referring to the map shown in FIG. 9 stored in advance in the correction coefficient adjusting unit 17. In this map, a weighting factor w is set with the absolute value of the steering angular velocity as an address based on the vehicle behavior in the actual vehicle test performed in advance. The weighting coefficient w is set to a small value when the steering angular velocity is small and to a large value when the steering angular velocity is large. Thus, the correction coefficient k, so that the weighting of the correction coefficient k ₁ for steady steering becomes large when the change rate of steering angle is small, whereas, the correction coefficient for the transient steering when the change rate of steering angle is large k ₂ The weight is set so as to increase, and push-under and tuck-in during turning are effectively suppressed regardless of the change speed of the steering angle.

  Thus, when the steering wheel is steered at a constant angle during turning, and when the steering wheel is transiently steered during turning, the vehicle yaw rate is not changed by the change in the longitudinal acceleration G. By adjusting the ratio transiently, the driver does not need to make fine adjustments to the steering angle in order to maintain the desired travel trajectory even when the accelerator or brake is operated during turning. Such a steering burden is reduced.

  Although the description of the specific embodiment is finished as above, the present invention is not limited to the above embodiment and can be widely modified. For example, in the above embodiment, the VGS control device 10 that variably controls the gear ratio of the VGS is employed as the steering angle ratio variable control device, but it is naturally possible to adopt a mode in which the gear ratio of the steer-by-wire device is variably controlled. It is. In the above embodiment, the VGS control device 10 is applied to an FF vehicle, but may be applied to an FR vehicle. Furthermore, the specific correction method of the VGS ratio and the specific configuration of the apparatus can be changed as long as they do not depart from the spirit of the present invention.

The block diagram which shows schematic structure of the VGS control apparatus which concerns on 1st Embodiment. The map which shows the relationship of the vehicle speed-VGS ratio which concerns on 1st Embodiment The block diagram which shows schematic structure of the correction coefficient setting part which concerns on 1st Embodiment. The block diagram which shows schematic structure of the correction coefficient setting part which concerns on deformation | transformation Embodiment 1. FIG. The block diagram which shows schematic structure of the correction coefficient setting part which concerns on deformation | transformation Embodiment 2. FIG. Correction coefficient map based on vehicle speed and longitudinal acceleration according to modified embodiment 2 The block diagram which shows schematic structure of the VGS control apparatus which concerns on 2nd Embodiment. The block diagram which shows schematic structure of the correction coefficient setting part which concerns on 2nd Embodiment. Weighting coefficient map based on steering angular velocity according to the second embodiment

Explanation of symbols

10 VGS control device 11 VGS ratio setting unit 12, 15 Correction coefficient setting unit (for steady steering)
13 VGS ratio correction unit 14 Target pinion angle calculation unit 17 Correction coefficient adjustment unit 26 Correction coefficient calculation unit (for transient steering)
21 Cornering power K setting unit 22 Stability factor A calculation unit 23, 32 Cornering power K ′ setting unit 31 Adjustment coefficient setting unit 33 Correction coefficient setting unit

Claims (4)

A steering angle ratio variable control device that variably controls the ratio of the steering angle of the steering wheel and the steering angle of the steering wheel according to the vehicle speed,
A steering angle ratio variable control device, wherein a correction value is set according to a longitudinal acceleration of a vehicle, and the ratio is corrected using the correction value.   When the change speed of the steering angle is smaller than a first predetermined value, a first correction value is set so that a yaw rate change due to a change in the longitudinal acceleration does not occur, and the ratio is calculated using the first correction value. The rudder angle ratio variable control device according to claim 1, wherein correction is performed.   When the change speed of the steering angle is greater than a second predetermined value, a second correction value is set so that a yaw rate change due to a change in the longitudinal acceleration does not occur, and the ratio is calculated using the second correction value. The rudder angle ratio variable control device according to claim 1, wherein correction is performed. When the change speed of the steering angle is smaller than a first predetermined value, a first correction value is set so that a yaw rate change due to a change in the longitudinal acceleration does not occur,
When the change speed of the steering angle is greater than a second predetermined value, a second correction value is set so that a yaw rate change due to a change in the longitudinal acceleration does not occur,
When the change speed of the steering angle is between the first predetermined value and the second predetermined value, the change speed of the steering angle with respect to the first correction value and the second correction value. The steering angle ratio variable control device according to claim 1, wherein the ratio is corrected using a correction value obtained by performing weighting based on the control.

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