JP2001004650A - Apparatus for estimating vehicle body side slip angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To estimate side slip angle with high precision even if vehicle speed changes during turning in estimating the vehicle body side slip. SOLUTION: Front/rear vehicle body speed Vx, lateral acceleration Gy, and yaw rate θ(.) are detected by a front/rear vehicle body speed detector 10, a lateral G detector 12, and a yaw rate detector 14 respectively. Using these detected values, an integrator 26 estimates a vehicle body side slip angle by [Gy-Vx(.).β(t-1)]/Vx-θ(.)} dt. By calculating the side slip angle in view of the time change Vx(.) in front/rear vehicle body speed Vx, it is possible to calculate the vehicle body side slip angle with high precision even if the vehicle body speed Vx is not constant while turning.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle slip angle estimating device, and more particularly to a device for estimating a vehicle slip angle based on a vehicle speed, a vehicle lateral acceleration and a vehicle yaw rate.

[0002]

2. Description of the Related Art Conventionally, there has been known a technique for estimating a side slip angle of a vehicle body in order to stabilize a posture of the vehicle during turning. Note that the vehicle body side slip angle generally refers to an angle between the traveling direction of the vehicle and the left and right central axes of the vehicle body during turning.

FIG. 4 shows, for example, JP-A-59-10550.
FIG. 1 is a block diagram showing a configuration of a vehicle slip angle estimation disclosed in Japanese Unexamined Patent Application Publication No. 6-206. Front and rear body speed detecting device 10, lateral acceleration (lateral G) detecting device 12, and yaw rate detecting device 14
Are provided, respectively, a front-rear body speed VX, a lateral acceleration Gy, and a yaw rate dθ / dt (hereinafter, a time differential d of a certain physical quantity P).
(P / dt is represented as P (•) using dot (•) as appropriate)
Is detected. The vehicle speed VX and the lateral acceleration Gy are supplied to a divider 22, where Gy / VX is calculated and output to an adder 24. On the other hand, the detected yaw rate θ (·) is also
Supplied to The adder calculates Gy / VX-θ (·) and outputs the result to the integrator 26. Gy / VX-θ (•) is an estimated time change value β (•) of the vehicle body slip angle as described later.
It is.

An integrator 26 calculates and outputs an estimated value β (＾) of the vehicle body slip angle by integrating β (·) supplied from the adder 24. (＾) indicates an estimated value.

In the prior art, if the integrand contains an error, the integration error accumulates. Therefore, when integrating by the integrator 26, the lateral acceleration Gy or the yaw rate θ (·) becomes substantially zero. If the value is regarded as 0, the estimated value β (＾) of the vehicle body side slip angle is set to 0, and the time integration is started when the value of the lateral acceleration Gy or the yaw rate θ (·) exceeds a value considered to be 0. I have.

That is, the operation in the integrator 26 is as follows.

(Equation 1) And the time integral is the lateral acceleration Gy or the yaw rate θ
It is executed from the time when (•) exceeds a predetermined threshold.

[0007]

However, in the above prior art, since the vehicle body slip angle is estimated by the equation (1), the vehicle speed changes, for example, when the driver turns off the accelerator pedal during turning. In this case, there is a problem that the estimation accuracy is reduced. Hereafter, regarding this problem (1)
This will be described in detail, including the process of deriving the equation.

FIG. 5 shows a coordinate system XY of the vehicle motion. Assuming that the position vector of the vehicle center of gravity is R, the speed vector dR / dt = R (·) is as follows.

[0009]

(Equation 2) Here, i and j are unit vectors in the x and y directions, respectively, and u and v are velocities (scalar amounts) in the x and y directions. When both sides of the equation (2) are differentiated with respect to time, an acceleration vector R (··) at the center of gravity of the vehicle is obtained, and the following equation is obtained.

[0010]

(Equation 3) However,

(Equation 4) It is. When formula (4) is rearranged for unit vectors i and j,

(Equation 5) Becomes Here, u and v are expressed by the following equation, using the vehicle speed V (= VX) and the slip angle β, assuming that β is small.

[0011]

(Equation 6)

(Equation 7) Then, the equations (6) and (7) are differentiated with respect to time. At this time, assuming that the vehicle speed V (= VX) is constant, dV / dt =
Assuming 0

(Equation 8)

(Equation 9) Becomes Substituting equations (8) and (9) into equation (5) and rearranging, the acceleration vector becomes

(Equation 10) Becomes Since the acceleration in the Y direction in equation (10) is nothing but the lateral acceleration Gy detected by the lateral acceleration detecting device 12,
From equation (10)

[Equation 11] Is obtained. Solving equation (11) for β (•) gives

(Equation 12) Thus, an estimated time change value of the vehicle body side slip angle is obtained.
The expression (1) is obtained by integrating both sides of the expression (12) with time.

As is apparent from this derivation process, in estimating the vehicle body slip angle β, the prior art assumes that the vehicle body speed V is uniformly constant.

However, during turning, the vehicle speed generally changes (particularly, decelerates). Therefore, when the vehicle body slip angle is estimated by using the equation (1), an error occurs due to a time change of the vehicle body speed, and it is difficult to estimate the vehicle body slip angle with high accuracy.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the related art, and an object of the present invention is to provide an apparatus capable of estimating a vehicle body slip angle with higher accuracy than ever before.

[0015]

To achieve the above object, the present invention provides a vehicle speed detecting means, a vehicle lateral acceleration detecting means, a vehicle yaw rate detecting means, a detected vehicle speed, a lateral acceleration and a yaw rate. Calculating means for calculating a vehicle body slip angle based on the change value of the vehicle speed.

Here, when the vehicle speed is V, the lateral acceleration is G, and the yaw rate is dθ / dt, the calculating means calculates the vehicle body side slip angle β (t) at time t.
To

(Equation 13) It is preferable to calculate with.

It is also preferable that the calculating means sets the initial value of the vehicle body side slip angle to 0 and sequentially calculates the vehicle body side slip angle thereafter. Here, the initial value of the vehicle body side slip angle may be set to an initial value 0 in a straight-ahead state where the steering angle, the lateral acceleration, the yaw rate, and the like are near zero.

In the present invention, the vehicle speed V
(= VX) is not assumed to be constant during turning, but the vehicle body side slip angle is estimated by treating the vehicle body speed V as a physical quantity that can be changed so as to match the actual traveling. Hereinafter, a method for estimating a vehicle body slip angle according to the present invention will be described.

Expressions (2) to (5) for deriving the vehicle body slip angle are the same as those in the prior art. However, according to the present invention, in equations (8) and (9), u
When calculating the time derivative of v and v, the vehicle speed V is calculated as being not constant but varying with time. That is, u = V
from cosβ

[Equation 14] And v = Vsinβ

(Equation 15) Becomes In the equations (14) and (15), dV / d
t = V (·) is a term that considers the time change of V. In Expressions (14) and (15), β was small and cos β was approximated to 1 and sin β was approximated to β. Therefore, by substituting the equations (14) and (15) into the equation (5), the acceleration R (··) at the vehicle center of gravity can be obtained by the following equation.

[0020]

(Equation 16) From the equation (16), since the acceleration in the Y direction is the lateral acceleration Gy, the following relational expression is obtained.

[0021]

[Equation 17] Here, comparing equation (17) with equation (11) of the prior art, the lateral acceleration Gy in equation (17) is the product V (の) of the time differential value V (·) of the vehicle speed V and the vehicle side slip angle β.・) ・ Β is newly added. This term V (•) · β
This is exactly the error that occurs when V is assumed to be constant in the prior art. As is apparent from this section, the estimation accuracy of the side slip angle β decreases particularly in a region where the vehicle speed changes greatly or the slip angle β is large. It will do.

In the present invention, the vehicle side slip angle can be estimated with high accuracy even if the vehicle speed V changes during turning by taking into account this term which was ignored in the prior art.

By solving equation (17) for β (·),

(Equation 18) The time integral of equation (18) gives (13)
The equation, that is, the vehicle body slip angle can be obtained.

As is apparent from the equation (13), the vehicle body slip angle β (t) at a certain time t is calculated based on the skid angle β (t−1) one operation time before. Therefore, when calculating the vehicle body slip angle, it is necessary to obtain its initial value. However, immediately after the start of turning where the steering angle, the lateral acceleration, the yaw rate, etc. deviate from values near 0, the skid angle is substantially zero. Therefore, the initial value can be set to 0.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of this embodiment. This is a configuration for executing the above equation (13).

Front / rear vehicle speed detecting device 10, lateral G detecting device 1
2 and the configuration of the yaw rate detecting device 14 are the same as those of the prior art, and respectively detect the longitudinal vehicle speed VX, the lateral acceleration Gy, and the yaw rate θ (·). The detected front and rear vehicle speeds VX are supplied to the differentiator 16 and also to the divider 22. The detected lateral acceleration Gy is supplied to the adder 20. The differentiator 16 differentiates the supplied VX with time. The obtained VX (•) is supplied to the multiplier 18. The previous estimated slip angle value β (t−1) (横) supplied from the integrator 26 is also supplied to the multiplier 18.
Then, these are multiplied and VX (•) · β (t-1) (＾)
And outputs it to the adder 20. In the adder 20, the lateral acceleration Gy supplied from the lateral acceleration detection device 12 and the multiplier 1
8 is subtracted from VX (•) · β (t−1) (＾) to obtain Gy−VX (•) · β (t−1) (＾), and the result is output to the divider 22. . The divider 22 divides VX from the front and rear vehicle speed detection device 10 and the output from the adder 20 to obtain (Gy−VX (·) · β (t−1) (＾) /
VX is output to the adder 24. The yaw rate θ (·) detected by the yaw rate detecting device 14 is also supplied to the adder 24, and the adder 24 subtracts the yaw rate θ (·) and performs the subtraction.
Output to Therefore, the physical quantity input to the integrator 26 is (Gy−VX (·) · β (t−1) (＾)) / VX−
θ (·), which is a time change value of the vehicle body side slip angle represented by the equation (18). Therefore, by integrating with the integrator 26, the estimated slip angle value β (t) at the time t is obtained.
(＾) can be obtained.

When the integration is performed by the integrator 26, the lateral acceleration Gy or the yaw rate θ (·) is used in the same manner as in the prior art.
May be started when the threshold value is equal to or larger than a predetermined threshold value.

The integrator 26 needs an initial value β (0) of the vehicle side slip angle in order to calculate the vehicle side slip angle by sequentially executing the integration operation. The initial value is, for example, β (0). = 0. Immediately after the start of a turn, the vehicle traveling direction and the left and right central axes generally coincide with each other, and such an assumption is realistic. of course,
The initial value β is calculated by using the equation (1) in the related art,
Using this β as an initial value, the vehicle body slip angle can also be sequentially calculated using equation (13) (however, the initial value of β is almost equal to 0 even using equation (1)).

FIG. 2 shows β estimated by the method of the present embodiment.
The time variation of Gy-VX (•) · β (・) obtained using (得) is shown. For comparison, a value when β is a true value and a temporal change of the lateral G value are also shown. In the figure, the horizontal axis is time (s) and the vertical axis is horizontal G value. A true value is indicated by a solid line, a change in the present embodiment is indicated by a chain line, and a lateral G value is indicated by a broken line. As can be seen from the figure, Gy−VX (·) · β (＾) in the present embodiment matches well with the true value Gy−V (·) · β. This is because, in the present embodiment, the time variation V of the vehicle speed V
This is because the estimation is also made in consideration of (•).

FIG. 3 shows the change over time of the vehicle body slip angle estimated by the method of the present embodiment. In addition, the true value and the estimated value of the prior art are also shown for comparison. In the figure, the horizontal axis is time (s), and the vertical axis is the vehicle side slip angle (deg). The true value is indicated by a solid line, the estimated value according to the present embodiment is indicated by an alternate long and short dash line, and the estimated value according to the related art is indicated by a broken line. Until the time = about 2.7 s, both the prior art and the method of the present embodiment agree well with the true value, but about 2.7 s
Thereafter, the estimated value of the prior art is far from the true value and the accuracy is reduced, whereas the method of the present embodiment is about 4.5.
It can be seen that the true value is well matched up to s. This is because the vehicle speed V changes (decelerates) after about 2.7 s, for example, the driver turns off the accelerator pedal, and the method according to the present embodiment estimates the vehicle speed V in consideration of the time change of the vehicle speed V. Therefore, there is no deviation from the true value unlike the related art. FIG. 3 clearly shows the superiority of this embodiment over the prior art.

Although the embodiment of the present invention has been described above, the vehicle slip angle estimated by the method of the present embodiment is supplied to the vehicle attitude control device to control the vehicle slip angle, thereby making it possible to achieve a higher turning speed than before. The vehicle posture can be stabilized.

[0033]

According to the present invention, the vehicle body slip angle can be estimated with high accuracy even if the vehicle speed changes during turning.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of an embodiment of the present invention.

FIG. 2 shows Gy-V (·) · in an embodiment of the present invention.
FIG. 7 is a graph showing a time change of β (＾).

FIG. 3 is a graph showing a change in an estimated vehicle body slip angle according to the embodiment of the present invention and the prior art.

FIG. 4 is a configuration block diagram of a conventional technique.

FIG. 5 is an explanatory diagram showing a coordinate system of a vehicle motion.

[Explanation of symbols]

10 front and rear body speed detecting device, 12 lateral acceleration detecting device,
14 yaw rate detector, 16 differentiator, 18 multiplier, 20 adder, 22 divider, 24 adder, 26
Integrator.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Katsuhiro Asano 41-cho, Chuchu-Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. 41, Yokomichi, Toyoda Central Research Laboratory, Inc. (72) Inventor Akitaka 2-1, Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Kenji Totsu Asahi, Kariya-shi, Aichi 2F029 AA02 AB01 2F, Ishin Seiki Co., Ltd.

Claims (3)

[Claims] 1. A vehicle speed detecting means, a vehicle lateral acceleration detecting means, a vehicle yaw rate detecting means, and a calculation for calculating a vehicle body side slip angle based on a detected vehicle speed, a lateral acceleration and a yaw rate and a change value of the vehicle speed. Means for estimating a vehicle body slip angle, comprising: 2. The apparatus according to claim 1, wherein the calculating means sets the vehicle speed to V, sets the lateral acceleration to G, and sets the yaw rate to dθ / dt. ) Is given by β (t) = ∫ ｛(G−dV / dt · β (t−1)) / V
An apparatus for estimating a vehicle body slip angle, which is calculated by -dθ / dt｝ dt. 3. The vehicle slip angle estimating device according to claim 2, wherein the calculating means sets an initial value of the vehicle slip angle to 0 and sequentially calculates the following vehicle slip angle.