JP2001047999A - Vehicle behavior detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly precisely find a slip angle irrespective of a road surface μ, by an inexpensive means not using an expensive sensor such as a master cylinder pressure sensor. SOLUTION: This detector is provided with an input means (a) for generating a signal as to a vehicle behavior, a slip ratio detecting means (b) for finding a slip ratio of a wheel based on the signal from the input means (a), a slip angle detecting means (c) for finding a slip angle of the wheel based on an input from the input means (a), a normalized slip ratio computing means (d) for finding a normalized slip ratio by dividing a present slip ratio by a preset linear slip ratio, a normalized slip angle computing means (e) for finding a normalized slip angle by dividing a present slip angle by a preset linear slip angle, and a vehicle condition estimating means (f) for estimating at least one out of braking force and side force based on the normalized slip ratio and the normalized slip angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for application to a vehicle behavior control device or the like which controls a braking force in accordance with a posture of a vehicle to stabilize the vehicle behavior.
The present invention relates to a vehicle behavior detecting means.

[0002]

2. Description of the Related Art Conventionally, the behavior of a vehicle is detected, and when the vehicle is in an unstable state such as oversteer or understeer exceeding a predetermined level, the hydraulic pressure of a wheel cylinder of each wheel is increased independently. A vehicle behavior control device that suppresses unstable behavior is known. In such a device, it is necessary to accurately detect the vehicle behavior, and in detecting the vehicle behavior, it is desired to accurately detect the braking force and the side force generated at the wheels.

An apparatus for detecting a braking force or a side force as described above is disclosed, for example, in Japanese Patent Application Laid-Open No. 5-20885.
No. 08 is known. This conventional device detects a master cylinder pressure by a master cylinder pressure sensor, and further estimates a wheel cylinder pressure by integrating pressure increase / decrease pulses output to the wheel cylinder.
Thereby, it is configured to estimate the braking force.

Another conventional technique is disclosed in Japanese Unexamined Patent Publication No.
The technique described in Japanese Patent No. 286598 is known. This technique determines the slip angle β of the vehicle and calculates the slip angle β
And values such as lateral acceleration (hereinafter referred to as lateral G), yaw rate, and steering angle, it is possible to determine what behavior the vehicle is currently exhibiting.

[0005] As one of the methods for calculating the slip angle β, there is known a method for calculating the slip angle β from the braking force difference between the wheels, particularly during execution of the vehicle behavior control. Therefore, also in this case, the braking force is determined from the master cylinder pressure as described above.

[0006]

However, the present inventor has found that the following problem arises when the braking force difference is estimated based on the brake fluid pressure obtained by the master cylinder pressure sensor. .

When there is a difference in brake hydraulic pressure between the left and right wheels, on a road surface having a high road surface friction coefficient (hereinafter referred to as road surface μ), this brake hydraulic pressure difference directly becomes a braking force difference.
On a low μ road, the brake hydraulic pressure is limited to the limit braking force based on the road surface μ on the high-pressure wheel, so that the brake hydraulic pressure difference does not directly correspond to the braking force difference. Therefore, when the slip angle β is estimated based on the brake fluid pressure difference, the slip angle β may not be accurately obtained.

Further, in the above-mentioned prior art, a sensor for detecting a brake pressure such as a master cylinder pressure sensor is required, and there has been a problem that the apparatus becomes expensive.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, to obtain a slip angle with high accuracy irrespective of the road surface μ, and to use an expensive master cylinder pressure sensor or the like. It is intended to be able to achieve this by inexpensive means without using sensors.

[0010]

According to the first aspect of the present invention, there is provided an input means a for generating a signal relating to vehicle behavior as shown in the claim correspondence diagram of FIG.
A slip rate detecting means b for obtaining a slip rate of a wheel based on a signal from the input means a; a slip angle detecting means c for obtaining a slip angle of the vehicle based on an input from the input means a; A normalized slip ratio calculating means d for obtaining a normalized slip ratio from the divided linear slip ratio and the current slip ratio, and a normalized slip angle from a division between a preset linear slip angle and the current slip angle. The vehicle includes a normalized slip angle calculating means e and a vehicle state estimating means f for estimating at least one of a braking force and a side force based on the normalized slip rate and the normalized slip angle.

According to a second aspect of the present invention, in the vehicle behavior detecting device according to the first aspect, a road surface friction coefficient estimating unit g for estimating a road surface friction coefficient is provided, and the normalized slip ratio calculating unit d is provided. May be configured to refer to a linear slip ratio corresponding to the estimated road surface coefficient, while the normalized slip angle calculation means e may be configured to use a predetermined value set as a linear slip angle.

Alternatively, in the vehicle behavior detecting device according to the first aspect of the present invention, a road surface friction coefficient estimating unit g for estimating a road surface friction coefficient is provided, and the normalized slip ratio calculating unit d is provided. Is configured to refer to the linear slip ratio according to the estimated road surface coefficient, and the normalized slip angle calculation unit e is configured to refer to the linear slip angle based on the estimated road surface coefficient. Is also good.

According to a fourth aspect of the present invention, in the vehicle behavior detecting device according to the second or third aspect, the vehicle state estimating means f is based on a normalized slip rate and a normalized slip angle. In determining the braking force, SLIN: peak slip ratio βLIN: peak slip angle SN0: normalized slip ratio = slip ratio / SLIN βNO: normalized slip angle = slip angle / βLIN Wheel load: load applied to the wheel μ: road surface friction coefficient, braking force = wheel load × road surface μ × normalized slip ratio / (normalized slip ratio ² + normalized slip ² ) ^1/2 Is also good.

As in the fifth aspect of the present invention, the second aspect
Or in the vehicle behavior detecting device according to 3, wherein the vehicle state estimating means f calculates a side force based on the normalized slip rate and the normalized slip angle, where SLIN: peak slip rate βLIN: peak slip angle SN0. : Normalized slip ratio = Slip ratio / SLIN βNO: Normalized slip angle = Slip angle / βLIN Wheel load: Load applied to wheel Road surface μ: Road surface friction coefficient Side force = Wheel load × Road surface μ × Normalized slip Corner /
(Normalized slip ratio ² + Normalized slip angle ² ) It may be configured to be obtained based on an arithmetic expression represented by ^1/2 .

[0015] As in the sixth aspect of the present invention, the first aspect
In the vehicle behavior detecting device according to any one of (4) to (4), the vehicle state estimating means f corrects the stationary wheel load based on the currently obtained side force, and uses the corrected value for the next calculation of the braking force or the side force. It may be.

[0016] As in the invention of claim 7, claim 6
In the vehicle behavior detection device described above, the side force used by the vehicle state estimating means f to correct the stationary wheel load may be a side force calculated based on a normalized slip ratio and a normalized slip angle.

[0017] As in the invention described in claim 8, as in claim 7,
In the vehicle behavior detecting device described in the first aspect, in the first cycle of the detection control, the side force used by the vehicle state estimating means f to correct the stationary wheel load is a lateral acceleration detected by a lateral acceleration sensor and a yaw rate sensor. And the side force calculated based on the yaw rate.

According to another aspect of the present invention, there is provided an input unit including a lateral acceleration sensor, a yaw rate sensor, a wheel speed sensor, and a steering angle sensor.
Vehicle state estimating means for estimating a slip angle by an observer with a steering angle and a braking force difference as inputs, wherein the vehicle state estimating means comprises a predetermined linear slip ratio and a current slip ratio. Normalized slip ratio calculating means for obtaining a normalized slip ratio from division of the normal slip angle, normalized slip angle calculating means for obtaining a normalized slip angle from division of a preset linear slip angle and a current slip angle, Vehicle state estimating means for calculating the braking force based on the normalized slip rate and the normalized slip angle,
The braking force difference △ Qt of each wheel is calculated based on the braking force calculated by the vehicle state estimating means. Qffr: braking force of the front right wheel Qffl: braking force of the front left wheel Qfrr: braking force of the rear right wheel Qfrl : The braking force of the rear left wheel is calculated based on the following equation: ΔQt = Qffr−Qffl + Qfrr−Qfrl.

According to a tenth aspect of the present invention, there is provided a vehicle behavior detecting device according to the ninth aspect, comprising: a brake unit capable of supplying brake fluid to braking means for each wheel of the vehicle; Control means for operating the brake unit based on the vehicle behavior control device comprising:
The vehicle behavior estimation means may be configured to process the braking force as 0 when the vehicle behavior control is not being executed.

[0020]

The relationship between the road surface μ, the braking / driving force Fx and the side force Fy has characteristics as shown in FIG. 2 depending on the slip ratio S and the slip angle β. In the drawing, Fxmax is the maximum braking force, and Fymax is the maximum side force.

Here, in FIG. 2, the braking / driving force Fx and the side force Fy are represented by the slip ratio S and the slip angle β, as separate parameters. The force generated in the tire is originally one, and it is observed that the force is divided into component forces in the x and y directions called braking / driving force / side force. Therefore, the number of peak points at which the braking / driving force / side force occurs is originally one, and in order to make this common, normalization is performed using the slip ratio peak value SLIN and the slip angle peak value βLIN.

In the present invention, based on the slip rate peak value SLIN and the slip angle peak value βLIN at this time, as shown by a dotted line in FIG. Time peak value S
When LIN and βLIN are uniquely determined by the road surface μ, the tire characteristics are estimated by approximation, and based on the tire wear circle, braking force = [(slip rate / SLIN) / ｛(slip rate / SLIN) ² + (Slip angle / βLI
N) ² ｝ ^1/2 ] × wheel load × road surface μ side force = [(slip angle / SLIN) / ｛(slip rate / SLIN) ² + (slip angle / βLI
N) ² ｝ ^1/2 ] × wheel load × road surface μ The braking force and the side force are determined.

As described above, according to the present invention, since the vehicle behavior such as the braking force and the side force is estimated based on the slip ratio and the slip angle, the estimation can be performed with high accuracy without using the wheel cylinder pressure or the master cylinder pressure. Therefore, the effect that the vehicle behavior can be detected with high accuracy using low-cost means is obtained.

Here, the tire friction circle will be described. Considering a friction ellipse as shown in FIG. 2 (c), consider a case where the normalized slip ratio σ is all directed in the front-rear direction or the lateral direction. If Fx and Fy at this time are pure Fx and Fy,
Each value is obtained by the above-described linear approximation as follows.

[0025] Here, when σ is greater than 1, the diameter of the friction ellipse is
Since it should be between pure Fx and pure Fy, Fx diameter and F
The y diameter is approximated by dividing by the ratio of SNOR and βNOR. When σ is smaller than 1, the braking / driving force / side force can be sufficiently generated without interference between S and β.
The y diameter may be pure Fx or pure Fy. Also, SNOR and βN
When dividing by the ratio of OR, σ ² = SNOR ² + βNOR ^2. Therefore, considering division by the square ratio, the Fx diameter Fx0 and the Fy diameter Fy0 of the friction ellipse are determined by the following equations. (See FIG. 2 (d)) Fx0 = | pure Fx | -ε (| pure Fx |-| pure Fy |) (β
NOR / σ) ² Fy0 = | pure Fy | -ε (| pure Fx |-| pure Fy |) (S
NOR / σ) ² Note that ε = σ (σ <1), ε = 1 (σ ≧ 1) Here, in order to calculate the braking / driving force and the side force, the friction ellipse shown in FIG. Fx direction component force, Fy
The component force ratio is divided, and the component force ratio is determined by the normalized slip ratio SNOR and the normalized slip angle β based on the definition of the friction ellipse.
Determined by NOR. Here, the direction constant λ is calculated as shown in FIG.
As shown in (e), assuming that the angle between the force applied to the tire and the component force in the Fx direction is: λ = ATN (βNOR / SNOR) Therefore, the braking / driving forces Q and Fy which are the component forces in the Fx direction
The side force SF, which is a component force in the direction, is calculated by Q = Fx0cosλ, SF = Fy0sinλ. To summarize the above, if the maximum value of the force generated in the front-rear direction of the tire (Fxmax) is equal to the maximum value of the force generated in the lateral direction (Fymax), the tire friction circle radius is calculated as F
The following expression holds as Tmax. {(S / Slim) ² + (β / βLim) ² } ^1/2 ≦
When 1, the braking / driving force; Q = FTmax · (S / Slim) Side force; SF = FTmax · (β / βLim) Also, {(S / Slim) ² + (β / βLim) ² } ^1/2 >
When 1, the braking / driving force; Q = {FTmax · (S / Slim)} /
｛(S / Slim) ² + (β / βLim) ²サ イ ド^1/2 side force; SF = ｛FTmax · (β / βLi)
m)｝ / {(S / SLim) ² + (β / βLim) ² }
^1/2 = {(β · Slim) / (S · βLim)} · Q The above is the basic idea of the present invention.

Further, the slip angle peak value does not fluctuate greatly in the actual running conditions of the vehicle, such as lateral grip due to the snow compaction. Even if it is fixed to, the estimation can be performed with high accuracy, and thus the effect of reducing the software without lowering the estimation accuracy can be obtained.

According to the fourth and fifth aspects of the present invention, braking force = wheel load × road surface μ × normalized slip ratio / (normalized slip ratio ² + normalized slip angle ² ) ^1/2 or side force = Wheel load x road μ x normalized slip angle /
(Normalized slip ratio ² + normalized slip angle ² ) The braking force or the side force is calculated based on the equation of ^1/2 , that is, based on the idea of the tire friction circle. , The braking force or the side force can be accurately calculated.

According to the sixth aspect of the present invention, the correction value of the stationary wheel load obtained based on the side force obtained this time is:
It is used for calculating the next braking force or side force. That is, the wheel load applied to each wheel at the time of turning or acceleration / deceleration is different from the wheel load at rest.For example, at the time of turning, the wheel load of the turning inner wheel becomes smaller, the wheel load of the turning outer wheel becomes larger, and acceleration occurs. In some cases, the wheel load on the front wheel decreases while the wheel load on the rear wheel increases. Conversely, when decelerating, the wheel load on the front wheel increases while the wheel load on the rear wheel decreases. Therefore, even if the wheel load at rest is used as it is for the calculation of the braking force or the side force, it is not possible to perform an appropriate calculation according to the situation of the vehicle.

On the other hand, the vehicle behavior can be properly estimated by sequentially calculating the wheel loads and using the obtained wheel loads for the next calculation of the braking force and the side force.

According to the seventh aspect of the present invention, the side force used for correcting the stationary wheel load is a side force calculated based on the normalized slip ratio and the normalized slip angle. Load correction can be performed. In the invention according to claim 8, in the first cycle of the detection control, the side force used for correcting the stationary wheel load is based on the lateral acceleration and the yaw rate detected by the lateral acceleration sensor and the yaw rate sensor. Since the calculated side force is used, the correction can be performed with high accuracy from the first control.

According to the ninth aspect of the present invention, the information necessary for estimating the slip angle by the observer is:
Since the difference between the braking forces of the left and right wheels is calculated based on the slip ratio, an expensive hydraulic pressure sensor or the like is not required, and the effect that the slip angle can be obtained at low cost and with high accuracy can be obtained.

According to the tenth aspect of the present invention, since the braking force is forcibly set to 0 when the vehicle behavior control is not being executed, it is possible to avoid an estimation error of the braking force difference. Thus, an inexpensive and highly robust vehicle behavior detecting device can be obtained.

[0033]

Embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) First, FIG. 3 is a configuration diagram showing an embodiment of the present invention. In the figure, reference numerals 1 to 4 denote wheel speed sensors (vehicle behavior detecting means) for detecting the rotation speed of the wheels.
For example, a pickup coil or the like is used to output a frequency signal corresponding to the rotation speed of the wheel.

Reference numeral 5 denotes a steering angle sensor (steering angle detecting means: vehicle behavior detecting means) for detecting a steering angle of the steering wheel. For example, a frequency signal corresponding to the steering angular velocity is output by a phototransistor or the like, and this is integrated. This detects the steering angle.

6 is a yaw speed sensor (yaw speed detecting means:
For example, a vehicle behavior detecting means) detects a yaw speed by receiving a Coriolis force from a tuning fork type strain gauge or the like.

Reference numeral 7 denotes a lateral acceleration (hereinafter referred to as lateral G) sensor, and reference numeral 8 denotes a longitudinal acceleration (hereinafter referred to as longitudinal G) sensor, for example, which measures lateral force and longitudinal force by a cantilever type strain gauge or the like. Detection of the receiving lateral G and the front and rear G is performed.

Reference numeral 9 denotes a control unit, which receives signals from the respective sensors 1 to 8 and performs various arithmetic processing to detect vehicle behavior. In addition, according to the detected vehicle behavior, a brake hydraulic control actuator 13 is provided. Each valve 1
By controlling the operations of 3a to 3h, switching of a hydraulic supply source to be described later to the wheel cylinder 20 of each wheel and control of the brake fluid pressure supplied to each wheel cylinder 20 are performed, and the braking force of each wheel is reduced. Controlling.

The brake hydraulic control actuator 13
Is for supplying brake fluid pressure to the wheel cylinders 20 of each wheel and controlling the brake fluid pressure, and is provided in the middle of the brake pipes 21, 22, 23. That is, the brake pipes 21 to 23 are connected to the brake pipes 21 that connect the wheel cylinders 20 of the right front wheel and the left rear wheel.
And a brake pipe 22 connecting the wheel cylinders 20, 20 for the left front wheel and the right rear wheel, a master cylinder 14 for generating a brake operating fluid pressure in response to the driver's pedal operation, and pipes 21, 22. And a brake pipe 23. And the brake hydraulic control actuator 1
Reference numeral 3 denotes hydraulic control valves (control valves) 13a to 13d which are provided in the middle of the brake pipes 21 and 22 and control the brake fluid pressure supplied to each wheel cylinder 20.
A control hydraulic source 13i such as a hydraulic pump capable of arbitrarily increasing pressure according to a signal from the control unit 9, a control hydraulic source 13i and a brake pipe 23.
And a brake pipe 24 connecting the brake pipes 23 and 2
A shut-off valve 13e and a shut-off valve that are provided in the middle of 4 and switch between the hydraulic pressure supplied to the brake pipe 21 and the hydraulic pressure generated by the master cylinder 14 or the hydraulic pressure of the control hydraulic power source 13i. 13g,
A control for switching the pressure supply source to the wheel cylindrors 20 one by one in accordance with a signal from the control unit 9, comprising a shutoff valve 13 f and a shutoff valve 13 h that perform the same switching with respect to the brake pipe 22. The brake fluid pressure of each wheel cylinder 20 is controlled. In addition, each shut-off valve 13e, 13
f, 13g and 13h are normally the master cylinder 14
The brake operation fluid pressure generated in each of the brake pipes 21 and
2, the shutoff valves 13g and 13h on the master cylinder 14 side are opened, and the shutoff valves 13e and 13f on the hydraulic supply pump 13i side are closed.

Next, the vehicle behavior detection of the control unit 9 will be described with reference to the flowcharts shown in FIGS.

The part shown in FIG. 4 is a part for processing signals indicating vehicle behavior detected by various sensors.
In step 10, the tire rolling angle δ is calculated from the steering angle detected by the steering angle sensor 5, in step 20, the lateral acceleration YG detected by the lateral G sensor 7 is calculated, and in step 30, the lateral acceleration YG is detected by the yaw rate sensor 6. The calculated yaw rate YAW is calculated.

Next, in step 40, the wheel speed Vw of each wheel detected by the vehicle speed sensors 1, 2, 3, 4 is calculated, and in the following step 50, for example, four wheels are selected based on each wheel speed Vw. High signal (4 wheel speed Vw
The vehicle speed Vx is calculated by processing such as applying a limiter to (the highest value among the above).

Next, at step 60, the road surface μ is estimated.
Is set as the deceleration XG, and the road surface μ is estimated by μ = (XG ² + YG ² ) ^1/2 .

Next, in step 70, the μ peak-time slip ratios SLINF and SLINR are calculated from the road surface μ independently before and after. This is determined by referring to a predetermined set value that changes according to the road surface μ shown in FIG.

Next, in step 80, step 7
0, the slip angle βLINF, β at the μ peak
Find LINR. However, as mentioned above, this value is road surface μ
Since a good estimated value can be obtained without a large change, it is also possible to substitute a fixed value that is determined in advance.

Next, at step 90, the wheel slip ratio SLIP of each wheel is calculated from the wheel speed Vw and the vehicle speed Vx. At this time, in order to prevent the vehicle speed error due to the inner wheel difference, VxFR = VxRR = Vx + YAW × (tread / 2) VxFL = VxRL = Vx−YAW × (tread / 2) By calculating the wheel slip ratio SLIP, the slip ratio calculation accuracy can be improved.

Next, the routine proceeds to step 100, where the wheel slip ratio SLIP and the μ calculated in step 70 are calculated.
The normalized slip ratio SNO for each wheel is calculated by dividing the peak slip ratios SLINF and SLINR.

Next, proceeding to FIG. 5, in step 110, the vehicle body slip angle β is calculated. The vehicle body slip angle β can be calculated, for example, by calculating an integrated value of [(lateral G / vehicle speed) -yaw rate].

In step 120, based on the vehicle body slip angle β, the front wheel tire slip angle βF and the rear wheel slip angle βR are corrected and calculated by the steering angle δ and the yaw rate YAW based on the following equation. I have. βF = β + (Lf / Vx) × YAW-S βR = β− (Lr / Vx) × YAW Here, Lf and Lr indicate the distance between the front and rear wheel axes and the center of gravity of the vehicle.

Next, the routine proceeds to step 130, where a normalized slip angle BNO of each wheel is calculated by dividing the tire slip angles βF, βR and the μ peak slip angles βLINF, βLINR calculated in step 80 previously. .

Next, in step 140, the wheel loads of each wheel are calculated with the side forces SFF and SFR calculated last time.
It is corrected and calculated based on the balance of the moment with the static wheel load WSF. Here, the correction coefficients KWFF and KWFR are as follows: KWFF = (distance between front wheel axle roll center and center of gravity) / (front wheel tread / 2) KWFR = (rear wheel axle roll center and center of gravity distance) / (rear wheel tread / 2) Is shown. That is, as shown in FIG. 9, if the wheel load changes due to a change in posture at the time of cornering or the like, the side force of each wheel also changes accordingly.
Correction is performed according to this to improve the accuracy.

Next, in steps 150 to 170, a tire slip friction circle shown in FIG. 10 is estimated.
First, at step 150, the normal slip ratio SNO
And the friction circle is estimated based on the square root of the sum of squares of the normalized slip angle βNO, and step 16 is performed so that this value does not take the tire grip range (maximum braking force) = 1 or less.
At 0 and 170, a limiter process is performed so that the lower limit value becomes 1.

Next, steps 180 and 190 shown in FIG.
Then, the final braking force QF and the final side force SF are calculated by multiplying the calculated values of the normalized slip ratio SNO, normalized slip angle βNO, and tire friction circle by the wheel load W and the road surface μ.

Finally, next time, the front wheel side force SFF and the rear wheel side force SFR for obtaining the wheel load W will be described.
Is calculated from the sum of the left and right wheel side forces.

In the first embodiment described above, the lateral G generated in the vehicle body is detected, and is made variable by the road surface μ by the difference between the vehicle speed Vx and the wheel speed Vw and the tire slip angles βF and βR. The normalized slip angle βNO and the normalized slip ratio SN0 are calculated based on the μ peak value, and the braking force QF and the side force SF are thereby detected, whereby the wheel cylinder pressure is limited to the limit braking force based on the road surface μ. Even if the relationship between the braking force and the braking force becomes inconsistent, the braking force QF / side force SF with high accuracy can be obtained.
Can be estimated. As described above, the first embodiment has an effect that the braking force QF and the side force SF can be estimated at low cost and with high accuracy without separately adding an expensive sensor such as a master cylinder pressure sensor. In addition,
In the embodiment, the sensor for detecting the master cylinder pressure is not provided, thereby enabling a more inexpensive configuration.However, in executing the control based on the slip ratio and the slip angle, the master cylinder pressure is reduced. Use of the detection signal of the sensor is also included in the present invention.

(Modification of First Embodiment) FIG. 7 shows a modification of the flowchart of the first embodiment. In the first embodiment, when estimating the wheel load W in step 140, the sum SFF of the side forces of the front left and right wheels and the sum SFR of the side forces of the rear left and right wheels are used. When calculating the sum of the wheels, from the lateral G and the yaw acceleration (d ² ψ / dt ² ), W · YG = SFF + SFR IZ (d ² ψ / dt ² ) = Lf · SFF−Lr · SFR W: vehicle weight , IZ: vehicle inertia moment, SFR = KSF (W · YG-KYAW (d ² ψ / d)
t ² )) SFF = W · YG-SFR It can be directly calculated from the following equation. Note that KSF =
Lf / (Lf + Lr), KYAW = IZ / Lf.

Here, the yaw rate acceleration is a differential value of the yaw rate signal. Here, the calculation is performed using the first-order difference value.

In this modification, by using the values obtained as described above for the side forces SFF and SFR in step 140, the same effect as in the above embodiment can be obtained without performing recursive calculation. .

(Embodiment 2) In this embodiment 2, the lateral velocity Vy is estimated by an observer type, and the slip angle β
Is calculated by β = Vy / Vx. The basic configuration of the second embodiment is the same as that of the first embodiment, and a description thereof will not be repeated. Also, in this flowchart, steps for executing processes common to the first embodiment are denoted by the same reference numerals as in the first embodiment, and description thereof is omitted.

In FIG. 11, in step 201 following step 30, the yaw rate Y detected in step 30 is set.
The yaw acceleration DYAW is calculated from the first-order difference of the AW.

In steps 202 and 203 following step 60, the slip rates SLINF and SLIN at peak μ for obtaining the normalized slip rate SNO and the slip angles βLINF and βLINR are calculated from the road surface μ obtained in step 60, for example, using a map. Refer to and calculate independently for the front and rear wheels. Here, the reason why the calculation is performed independently before and after is because the μ peak changes depending on the wheel load. In particular, in the case of a front-wheel drive vehicle, the difference between the front and rear load distribution is large, so that the μ peak varies. is there.

The following steps 90 and 100 correspond to the first embodiment.
And the subsequent step 20 shown in FIG.
In step 4, a normalized slip angle βNO is calculated from the front wheel slip angle βf and the rear wheel slip angle βr previously calculated, and the linear slip angle βLIN.

Next, at step 140, the first embodiment
The wheel load W of each wheel is obtained in the same manner as in
The tire slip friction circle is estimated by 160 and 170. First, in step 205, a friction circle is estimated from the square root of the sum of squares of the normalized slip ratio SNO and each of the normalized slips βNO.
In step 160 and step 170, a limiter process is performed so that the lower limit value of the slip friction circle βSNO becomes 1.

Next, steps 206 to 2 shown in FIG.
08 is the left-right braking force difference ΔQ for determining the slip angle β.
This is a routine for determining T. First, step 206
, It is determined whether or not the posture control is currently being performed. If the posture control is being performed, it is determined that the brake hydraulic pressure of each wheel is independently controlled by the brake hydraulic control actuator 13, and the process proceeds to step 207. Then, the braking force difference ΔQT is calculated. In other cases, for example, when the vehicle is not controlled and the brake is operated, substantially the same hydraulic pressure is supplied to each wheel, and it is considered that there is almost no difference in control force. Therefore, in step 208, △ QT = 0 is processed. .

Next, at step 209, calculation of front and rear wheel side forces SFF, SFR is performed. This is given by the following equation of motion: W · YG = SFF + SFR IZ (d ² ψ / dt ² ) = Lf · SFF−Lr · SFF
+ (T / 2) · {QT W: vehicle weight, IZ: vehicle moment of inertia, (d ² } / dt
² ): yaw acceleration, Lf, Lr: distance between axle and center of gravity,
T: Tread.

SFR = {W · YG− (IZ / Lf) (d ² } / d
t ² ) + (1 / Lf) (T / 2) · {QT} × [1 /
{1+ (Lr / Lf)}] The yaw acceleration DYAW, the lateral G, and the braking force difference ΔQT are calculated by SFF = W · YG−SFR.

Next, at step 210, the cornering stiffness Kf, necessary for the observer gain calculation is calculated.
Kr is calculated as (side force / previously calculated βf,
βr), and in steps 211 to 214, an observer calculation is performed. First, step 2
At 11, each observer gain is calculated. This approximates the system equation of the vehicle as Equation 1 below.

[0067]

[Formula 1] Here, a11 = (1 / (IZ · Vx)) (Kf · Lf ² + Kr
· Lr ² ) a12 = (1 / (IZ · Vx)) (Kf · Lf-Kr ·
Lr) a21 = (1 / (W · Vx)) (Kf · Lf−Kr · L
r) -Vx a22 = (1 / (W · Vx)) (Kf + Kr) b11 = (− 1 / IZ) · Kf · Lf b12 = (1 / IZ) (T / 2) b21 = (− 1 / W) · Kf b22 = 0 These ann and bnn are calculated using the cornering stiffnesses Kf and Kr determined in step 210, and the lateral velocity Vy is estimated by the observer configuration shown in FIG.

First, at step 212, the yaw acceleration estimation value SDYAW and the lateral acceleration estimation value are calculated from the previous yaw rate estimation value SYAW- ₁ , the lateral speed estimation value SVy- _{1, the} steering angle δ, and the left / right braking force difference ΔQT. SDVy is calculated, and in step 213, the yaw rate estimated value SDYAW and the lateral direction estimated value SDVy are integrated with a value obtained by adding a yaw rate error feedback amount SYAWE and a lateral speed error feedback amount SVyE, which will be described later, to obtain the yaw rate estimated value. The SYAW and the estimated lateral speed SVy are reconstructed.

Next, the process proceeds to step 214, where step 2
13. The yaw rate estimation value SYAW obtained in step 13 and step 30
Is multiplied by the predetermined observer error feedback gains h11 and h12 to calculate the error feedback correction amounts SYAWE and SVyE in step 213 in the next calculation, and in step 215, step 213 The slip angle estimation value β and the front and rear tire slip angles βf, βr are calculated from the lateral speed estimation value SVy calculated in step (1).

As described above, when the slip angle is estimated by the observer, the difference between the left and right wheel braking forces △ Q required as information is calculated from the slip ratio and the slip angle. Expensive sensors and the like become unnecessary. At this time, in order to avoid the estimation error of the braking force difference accompanying this, during the non-control of the vehicle behavior control, the braking force difference estimated value is forcibly set to zero and the slip angle is estimated. An inexpensive and highly robust slip angle detector can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims showing the present invention.

FIG. 2 is an explanatory diagram showing braking force characteristics, side force characteristics, and tire friction circles of the present invention.

FIG. 3 is an overall view showing the first embodiment of the present invention.

FIG. 4 is a flowchart illustrating a control flow according to the first embodiment.

FIG. 5 is a flowchart showing a control flow according to the first embodiment.

FIG. 6 is a flowchart illustrating a control flow according to the first embodiment.

FIG. 7 is a flowchart illustrating a control flow according to a modification of the first embodiment.

FIG. 8 is a characteristic diagram showing characteristics of a normalized slip ratio according to the first embodiment.

FIG. 9 is a characteristic diagram showing a relationship between a wheel load and a side force.

FIG. 10 is an explanatory diagram showing a tire friction circle.

FIG. 11 is a flowchart illustrating a control flow according to the second embodiment.

FIG. 12 is a flowchart illustrating a control flow according to the second embodiment.

FIG. 13 is a flowchart showing a control flow according to the second embodiment.

FIG. 14 is an explanatory diagram illustrating an observer according to the second embodiment;

[Explanation of symbols]

 a input means b slip rate detecting means c slip angle detecting means d normalized slip rate calculating means e normalized slip angle calculating means f vehicle state estimating means g road surface friction coefficient estimating means 1-4 wheel speed sensor 5 steering angle sensor 6 yaw Speed sensor 7 lateral acceleration sensor 8 longitudinal acceleration sensor 9 control unit 13 brake hydraulic control actuator 13a-d hydraulic control valve 13e-h shutoff valve 13i hydraulic supply pump 14 master cylinder 20 wheel cylinder 21 brake pipe 22 brake pipe 23 brake pipe 24 brake Piping

Claims (10)

[Claims] An input means for generating a signal relating to vehicle behavior, a slip rate detecting means for obtaining a slip rate of a wheel based on a signal from the input means, and a slip angle of the vehicle based on an input from the input means. Slip angle detection means to be obtained, normalized slip rate calculation means to obtain a normalized slip rate from division of a preset linear slip rate and the current slip rate, and a predetermined linear slip angle and a current slip angle. And a vehicle state estimating means for estimating at least one of a braking force and a side force based on the normalized slip rate and the normalized slip angle. A vehicle behavior detecting device, comprising: 2. A road surface friction coefficient estimating unit for estimating a road surface friction coefficient, wherein the normalized slip ratio calculating unit is configured to refer to a linear slip ratio according to the estimated road surface coefficient. 2. The vehicle behavior detecting device according to claim 1, wherein the normalized slip angle calculating means is configured to use a fixed value set in advance as the linear slip angle. 3. A road surface friction coefficient estimating unit for estimating a road surface friction coefficient is provided, wherein the normalized slip ratio calculating unit is configured to refer to a linear slip ratio according to the estimated road surface coefficient. The vehicle behavior detecting device according to claim 1, wherein the normalized slip angle calculating means is configured to refer to the linear slip angle based on the estimated road surface coefficient. 4. The vehicle state estimating means calculates a braking force based on a normalized slip ratio and a normalized slip angle, wherein SLIN: peak slip ratio βLIN: peak slip angle SN0: normalized slip ratio = Slip ratio / SLIN βN0: Normalized slip angle = Slip angle / βLIN Wheel load: Load applied to the wheel Road surface μ: As road surface friction coefficient, braking force = wheel load × road surface μ × normalized slip ratio / (normalized slip The vehicle behavior detecting device according to claim 2 or 3, wherein the vehicle behavior detecting device is configured to be calculated based on an arithmetic expression represented by a ratio ² + a normalized slip ² ) ^1/2 . 5. The vehicle state estimating means calculates a side force based on the normalized slip ratio and the normalized slip angle, wherein SLIN: peak slip ratio βLIN: peak slip angle SN0: normalized slip ratio = Slip ratio / SLIN βNO: Normalized slip angle = Slip angle / βLIN Wheel load: Load applied to the wheel Road surface μ: Road surface friction coefficient: Side force = wheel load × road surface μ × normalized slip angle /
4. The vehicle behavior detecting device according to claim 2, wherein the vehicle behavior detecting device is configured to be calculated based on an arithmetic expression represented by (normalized slip ratio ² + normalized slip angle ² ) ^1/2 . 6. The vehicle state estimating means corrects the stationary wheel load based on the side force obtained this time, and uses the correction value for the next calculation of the braking force or the side force. A vehicle behavior detecting device according to any one of claims 1 to 5. 7. The vehicle behavior detecting device according to claim 6, wherein the side force used by the vehicle state estimating means to correct the stationary wheel load is a side force calculated based on a normalized slip ratio and a normalized slip angle. A vehicle behavior detecting device, characterized in that: 8. The vehicle behavior detecting device according to claim 7, wherein in the first cycle of the detection control, the side force used by the vehicle state estimating means for correcting the stationary wheel load is a lateral acceleration sensor and a yaw rate sensor. A side force calculated based on the lateral acceleration and the yaw rate detected by the vehicle behavior detecting device. 9. An input means including a lateral acceleration sensor, a yaw rate sensor, a wheel speed sensor, and a steering angle sensor, and a vehicle state estimating means for estimating a slip angle by an observer using a steering angle and a braking force difference as inputs. In the vehicle behavior detecting device, the vehicle state estimating means includes: a normalized slip rate calculating means for calculating a normalized slip rate from a division of a preset linear slip rate and a current slip rate; and a preset linear slip angle. And a current slip angle, and a normalized slip angle calculating means for calculating a normalized slip angle from the division of the current slip angle, and a vehicle state estimating means for calculating a braking force based on the normalized slip rate and the normalized slip angle. The braking force difference ΔQt of each wheel is calculated based on the braking force calculated by the vehicle state estimating means, Qffr: braking force of the right front wheel Q fl: braking force of the left front wheel Qfrr: braking force of the right rear wheel Qfrl: braking force of the left rear wheel The vehicle is characterized in that it is calculated based on the following formula: ΔQt = Qffr-Qffl + Qfrr-Qfrl. Behavior detection device. 10. A vehicle behavior detecting device according to claim 9, wherein: a brake unit capable of supplying a brake fluid to braking means of each wheel of the vehicle; and control for operating the brake unit based on the detected vehicle behavior. Means for detecting a vehicle behavior, wherein the vehicle behavior estimation means is configured to process the braking force as 0 when the vehicle behavior control is not executed. apparatus.