JP2000088874A - Vehicle behavior detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a detection time and improve a detection accuracy in a vehicle behavior detecting device for detecting a slip angle of a vehicle. SOLUTION: This vehicle behavior detecting device, equipped with a slip angle estimation means (d) for estimating a slip angle of a vehicle, namely, the angle formed between the vehicle traveling direction and the front-to-back direction of the vehicle, based on the inputs from a steering angle sensor (a), a lateral acceleration sensor (b) and a yaw rate sensor (c), is so composed that the slip angle estimation means (d) is equipped with a side force estimation means (e) for estimating a side force generated in tires of front and rear wheels based on the detected yaw velocity and the lateral acceleration, and with a tire stiffness estimation means (f) for estimating a tire stiffness by the division between each side force estimated value on the front and the rear and each tire slip angle at that time, and that the slip angle estimation means (d) will estimate a slip angle at the operation period of this time based on the preceding value of the tire stiffness estimated value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a device for controlling the behavior of a vehicle and the like, and relates to a vehicle behavior detecting device for detecting a vehicle behavior, particularly a slip angle.

[0002]

2. Description of the Related Art In recent years, the braking force and the driving force of each wheel are optimally controlled in accordance with the behavior of a vehicle to prevent the spin due to excessive oversteer and the deterioration of the maneuverability due to excessive understeer to stabilize the running of the vehicle. Control is running. In order to execute such control, it is necessary to accurately detect the behavior of the vehicle without delay, and in particular, it is desired to detect the slip angle β of the vehicle with high accuracy without delay.

[0003] Conventionally, as an apparatus for detecting the vehicle behavior including the above-mentioned slip angle β, for example, Japanese Patent Application Laid-Open No. 5-20860.
An apparatus described in Japanese Patent Publication No. 8 is known. This prior art is a technique for determining a motion variable such as a lateral acceleration, a yaw speed, an attitude angle, a slip angle, and a side force of an automobile. The stiffness is recursively calculated from the output difference between the two types of filter pairs, and the motion variables such as the slip angle are estimated.

[0004]

In the above-mentioned prior art,
When estimating the slip angle, the stiffness is given in advance, and the recursive calculation is performed to estimate the stiffness. Therefore, the stiffness is given in advance by a change in the road surface friction coefficient (hereinafter referred to as road surface μ). When the value is significantly different from the estimated value, it takes time to obtain the stiffness from the difference between the evaluation values, and there is a problem that the estimation error increases.

The present invention has been made in view of the above problems, and has as its object to shorten the detection time and improve the detection accuracy.

[0006]

In order to achieve the above object, the inventor of the present application has detected the vehicle behavior using an observer (vehicle model) model. That is, the behavior of the vehicle can be approximated by the mathematical formula shown in FIG. In the equation, dψ / dt yaw speed, Vy is a lateral speed, and δ is a tire rolling angle.

Therefore, an observer which is the same model as this vehicle is provided, the detected value of the yaw speed in the actual vehicle is compared with the output of the observer, and the behavior of the vehicle is detected by feeding back the result of the comparison. Can be.

Here, a11 to a11 in the mathematical formula shown in FIG.
a22 and b11, b21 can be obtained as follows. 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 b21 = (− 1 / W) Kf where Vx: front-rear direction speed, IZ: vehicle yaw Moment of inertia, Kf: front wheel tire stiffness, Kr: rear wheel tire stiffness, Lf: distance between front wheel axle and center of gravity, L
r: distance between the rear wheel axle and the center of gravity, W: vehicle weight.

From the above relationship, the lateral speed Vy is estimated by the observer model shown in FIG. 2. At this time, the tire stiffness is a known or detectable value except for the tire stiffness Kf and Kr. Kf, K
r is a nonlinear characteristic as shown in FIG.
It changes depending on the road surface μ (road surface friction coefficient).

The inventor of the present application considers that it is necessary to accurately estimate the tire stiffnesses Kf and Kr in order to accurately detect the vehicle behavior, and the tire stiffnesses Kf and Kr are determined by the tire side stiffness Kf and Kr. Based on the force and the current tire slip angle, as shown in FIG. 4, virtual calculation is always performed, the lateral speed Vy is obtained by the observer, and the slip angle β = Vy / Vx is estimated. .

That is, according to the first aspect of the present invention, as shown in the claim correspondence diagram of FIG. 1, a steering angle sensor a for detecting a rolling angle of a tire of a vehicle and a lateral angle sensor for detecting a lateral acceleration of the vehicle. An acceleration sensor b, a yaw rate sensor c for detecting a yaw speed around the center of gravity of the vehicle, and a vehicle traveling direction and a front-rear direction of the vehicle based on inputs from the sensors a, b, and c at a predetermined calculation cycle. And a slip angle estimating means d for estimating a slip angle of the vehicle, the slip angle estimating means d including, based on the detected yaw speed and lateral acceleration,
Side force estimating means e for estimating the side force generated in the front and rear tires, and tire stiffness estimating means f for estimating the tire stiffness by dividing each of the front and rear side force estimated values and each tire slip angle at that time. And the slip angle estimating means d
Are configured to estimate the slip angle in the current calculation cycle based on the previous value of the tire stiffness estimated value. Note that the tire stiffness refers to a side force per unit slip angle.

In the present invention, the side force of the front and rear wheels is estimated by the side force estimating means e, the tire stiffness is constantly estimated by the tire stiffness estimating means f based on the side force, and the slip angle is estimated based on the tire stiffness. Is estimated. Therefore,
The tire stiffness can be obtained with high accuracy in response to a change in the road surface μ or the like, and a highly accurate slip angle can be obtained.

As described in claim 2, claim 1
In the vehicle behavior detecting device described above, the slip angle estimating means d is configured to calculate a slip angle by dividing an estimated value of a lateral speed of a tire by a front-rear speed, and to calculate a slip angle based on the last estimated stiffness value from a previous time. The present estimated final stiffness value may be determined based on the estimated tire stiffness value, and the estimated lateral speed estimated value may be determined based on the final estimated stiffness value.

Further, as described in claim 3, claim 2
In the vehicle behavior detection device described above, the slip angle estimating means d integrates the current lateral speed differential value with the previous lateral speed estimated value to obtain the lateral speed estimated value,
The integrated value may be further obtained by integrating a feedback error value formed based on the difference between the detected value and the estimated value of the yaw speed.

In addition, as described in claim 4, claim 1
4. The vehicle behavior detecting device according to any one of claims 1 to 3, wherein the side force estimating means e calculates a side force SFR of a rear wheel and a side force SFF of a front wheel, YG: lateral acceleration, Kyg: vehicle weight, DYAW: yaw speed, Kyaw: The value obtained by dividing the yaw moment of inertia of the vehicle by the distance from the center of gravity of the vehicle to the front wheel axle, Ksf: the value obtained by dividing the distance from the center of gravity of the vehicle to the front wheel axle by the distance from the front wheel axle to the rear wheel axle, SFR = (YG · Kyg-DYAW ・ Kyaw) ・ Ks
It may be configured to be obtained based on an arithmetic expression of f SFF = −SFR + YG · Kyg.

In addition, as described in claim 5, claim 1
5. In the vehicle behavior detecting device according to any one of Items 4 to 4, the tire stiffness estimating means f may be configured to set a predetermined fixed value when the side force falls below a preset threshold.

Therefore, when the side force is too small and an error may occur, a fixed value is used to
The stability of the observer can be ensured while suppressing the error from becoming too large.

Also, as described in claim 6, claim 1 is
6. The vehicle behavior detecting device according to any one of claims 5 to 5, wherein the tire stiffness estimating means f has two types of time constants, large and small, the tire rolling angle is a predetermined value or more, and the side force estimated value is a predetermined value or more. In this case, the time constant smaller by a predetermined time may be selected to perform low-pass filtering on the tire stiffness.

Therefore, when the steering angle (tire rolling angle) is large, a small time constant is selected, and the stiffness convergence speed is increased.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 is a block diagram showing a vehicle behavior detecting apparatus according to an embodiment of the present invention.
Reference numerals 4 to 4 denote wheel speed sensors that detect the rotation speed of the wheels, and are configured to output a frequency signal corresponding to the rotation speed of the wheels using, for example, a pickup coil.

In the figure, reference numeral 5 denotes a steering angle sensor for detecting a tire rolling angle. For example, a frequency signal corresponding to the steering angular velocity is output by a phototransistor or the like, and the steering angle is detected by integrating the frequency signal.

Reference numeral 6 denotes a yaw speed sensor which detects a yaw speed by receiving a Coriolis force by, for example, a tuning fork type strain gauge.

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, which receives a lateral force and a longitudinal force by, for example, a cantilever type strain gauge. , Lateral acceleration, and longitudinal acceleration.

Reference numeral 9 denotes an arithmetic unit, and each of the sensors 1 to 8
, And performs various arithmetic processing to detect the vehicle behavior.

Next, the behavior detection in the arithmetic unit 9 will be described with reference to the flowcharts of FIGS. In step 10, the tire rolling angle δ is detected based on the signal from the steering angle sensor 5, and in the next step 20, the lateral acceleration YG detected by the lateral G sensor 7 is calculated. The yaw speed YAW detected by the sensor 6 is detected.

In the following step 40, the wheel speed sensor 1
4, the wheel speed VW of each wheel detected is detected, and in step 50, the vehicle speed VX is calculated based on the wheel speed VW. Note that the vehicle speed V
X is, for example, a limiter applied to the select high signal of the wheel speed VW of the four wheels (an upper limit value based on acceleration / deceleration, etc.)
The lower limit is given).

In the following step 60, the yaw acceleration DYAW is calculated based on the first-order difference value of the yaw speed YAW detected in step 30.

The following steps 70 and 80
It calculates the side force SFF / SFR applied to the front and rear wheels, and corresponds to the side force estimating means in the claims. This is, as shown in FIG.
Lr is the distance between the front wheel axle and the center of gravity, the distance between the rear wheel axle and the center of gravity, and IZ: vehicle yaw moment of inertia; DYAW: yaw acceleration. -DYAW = Lf-SFF-Lr-SFR is transformed and SFR = [Lf / (Lf + Lr)] [W-YG-(IZ
/ Lf) · DYAW] SFF = W · YG−SFR, where W = Kyg, Lf / (Lf + Lr) =
Ksf, IZ / Lf = Kyaw Shown in each step based on lateral GYG and yaw acceleration DYAW SFR = (YG · Kyg−DYAW · Kyaw) · Ks
f SFF = −SFR + YG · Kyg The side forces SFF and SFR are calculated based on two equations.

Next, in steps 90 to 120, the estimation of the front tire stiffness KCPFP is performed in step 130.
In steps 160 to 160, the rear wheel stiffness KCPRP is estimated, and a portion for performing such processing corresponds to a tire stiffness estimating means in claims.

First, steps 90, 100 and 13
At 0 and 140, a stiffness calculation permission determination is made. Each tire stiffness KCPFP, KCPRP is
Each is calculated by the side force / tire slip angle. At this time, the side forces SFF and SFR calculated in steps 70 and 80 are small, and the tire slip angles βf and βr described later are small.
When a detection error occurs, a stiffness estimation error increases. For this reason, the side forces SFF, SFR and the slip angles βf, βr are respectively set to corresponding predetermined values SFFKCPI, SFRKCPI, SFFBT, S
If smaller than FRBT, steps 120 and 16
0, the predetermined fixed values KCPFI and KCPRI are used as tire stiffness. Otherwise, in steps 110 and 150, KCPFP = SFF / βf,
KCPRP = SFR / βr. As described above, the side forces SFF and SFR and the slip angles βf and βr are respectively set to the corresponding predetermined values SF.
FKCPI, SFRKCPI, SFFBT, SFRBT
The processing of setting the tire stiffness to predetermined fixed values KCPFI and KCPRI when the tire stiffness is smaller than the predetermined value.
It corresponds to the described invention.

Next, the process proceeds to step 170, and in steps 170 to 360, a flag for determining a stiffness filter coefficient is set / cleared. First, in steps 170 to 210, processing for reducing the filter of the front wheel tire stiffness is performed. First, in step 170, the tire rolling angle δ is larger than a predetermined value KCPSTR, and in the next step 180, the front wheel Side force SFF is a predetermined value SFFKCP
If it is larger than 2, the steering angle may greatly change the slip angle β. In this case, it is necessary to reduce the filter time constant of the stiffness to improve the responsiveness and improve the accuracy of the slip angle β. , Step 200
, The filter coefficient switching flag FSFF is set to 1. Conversely, the tire rolling angle δ and the side force S
When the FF is equal to or smaller than the predetermined values KCPSTR and SFFKCP2, the stiffness change is small. Therefore, the filter time constant is increased with priority given to stability.
At 90 or 210, the filter coefficient switching flag FSFF is cleared to 0.

In steps 220 to 240, a process for reducing the filter of the tire stiffness described above for the rear wheels is performed, that is, the filter coefficient switching flag FS for the rear wheels
Set / clear FR.

The following steps 250 to 360 are operation sections for setting / decrementing the filter time constant switching counter based on the switching flags FSFF and FSFR.
An object of the present invention is to reduce the filter of the tire stiffness for a predetermined time when the rolling angle is large.

First, in steps 250 and 260,
The rising edge of the filter coefficient switching flag FSFF is detected, and at the moment when FSFF = 1, step 27 is executed.
At 0, the filter time constant switching counter CSFF is set to a predetermined value TSFF. At other times, in steps 280 to 300, the counter value CSFF is decremented one by one until CSFF = 0. Thereby, a predetermined time is set. In steps 310 to 360, similar processing is performed for the rear wheels.

Steps 370 to 430 are processing sections for calculating the final stiffnesses KCPF and KKPR.
When F is 0 or more, that is, when the tire rolling angle δ is KCP
STR or more and front wheel side force SFF is SFF
If it is within the TSFF time after KCP2, the process proceeds to step 380 to set the filter time constant SFFTAU to a small time constant SFFTAUH. Otherwise, the process proceeds to step 390 to set a large time constant SFFTAUL. By obtaining the final stiffness KCPF using this filter time constant, the convergence speed of the stiffness calculation at the time of turning is increased, and the detection accuracy of the front wheel slip angle βf is improved. Step 4
In the case of 00 to 420, the same processing is performed for the rear wheel. Further, the processing of setting the time constant in steps 170 to 430 to obtain the stiffness corresponds to the invention of claim 6.

Next, in step 440, the system gains GA11 to GA22, GB11 and GB21 are determined based on the final stiffnesses KCPF and KCPR already determined. These system gains are determined based on vehicle specifications and the like based on the system equation in FIG. 2 described above, and are determined based on the following equation (1).

[Formula 1] GA11 = (1 / (IZ · VX)) (KKPF · Lf ²
+ KCPR · Lr ² ) GA12 = (1 / (IZ · VX)) (KKPF · Lf−
GA21 = (1 / (W · VX)) (KKPF · Lf−K)
CPR · Lr) −VX GA22 = (1 / (W · VX)) (KCPF + KCP
R) GB11 = (− 1 / IZ) KCPF · Lf GB21 = (− 1 / W) KCPF Next, at step 450, the estimated yaw acceleration value SDYA
The W and lateral G estimated values SDVy are calculated, and step 460 is performed.
Are integrated to obtain a yaw rate estimated value SYAW and a lateral speed estimated value SVy.

Next, at step 470, the difference between the yaw speed YAW detected by the yaw speed sensor 6 and the estimated yaw speed value SYAW is multiplied by predetermined feedback gains GH11 and GH21 in order to obtain the error feedback. By adding this to the integration in step 460 at the time of the next calculation, error feedback of the estimated lateral velocity SVy is performed.

Next, at step 480, the slip angle β of the vehicle body is obtained by dividing the estimated lateral speed SVy and the vehicle speed VX.
Further, the front wheel slip angle βf and the rear wheel tire slip angle βr are calculated.

In this embodiment, the slip angle β of the vehicle body, the front wheel tire slip angle βf, and the rear wheel tire slip angle βr are obtained as described above. As described above, the tire stiffness KCPFP, KCPRP is constantly calculated based on the estimated side forces SFF, SFR and the slip angle β, and further, the lateral speed estimation value SVy is obtained by the observer based on the tire stiffness KCPFP, KCPRP. There is an effect that the slip angle β can be estimated.

In this estimation, the values of the side forces SFF and SFR are set to predetermined values SFFKCP,
When the wheel stiffness is smaller than the SFRKCP, the respective wheel stiffnesses KCPFP and KCPRP are fixed. Therefore, it is possible to prevent the error of the subsequent estimated value from increasing due to the detection error and to secure the stability of the observer. It has the effect of being able to.

In addition, when the steering angle becomes large, the convergence speed of the stiffness is increased by reducing the time constant of the low-pass filter for calculating the stiffness, so that the slip angle estimation accuracy is improved. can get.

[0042]

As described above, the inventions according to the first to sixth aspects are characterized in that the steering angle sensor a, the lateral acceleration sensor b,
Based on the input from the yaw rate sensor c, the slip angle estimating means d for estimating the slip angle of the vehicle, which is the angle between the vehicle traveling direction and the front-rear direction of the vehicle, based on the detected yaw speed and lateral acceleration, Side force estimating means e for estimating the side force generated in the front and rear tires, and tire stiffness estimating means f for estimating the tire stiffness by dividing each of the front and rear side force estimated values and each tire slip angle at that time. Since the slip angle estimating means d is configured to estimate the slip angle in the current calculation cycle based on the previous value of the tire stiffness estimated value, the slip angle estimating means d immediately responds to a change in the road surface μ or the like with high accuracy. The effect of obtaining the tire stiffness and obtaining a highly accurate slip angle can be obtained.

Further, in the invention according to claim 5, in the vehicle behavior detecting device according to any one of claims 1 to 4, the tire stiffness estimating means f is set when the side force falls below a preset threshold value. Because it was configured to be a fixed value, if the side force is too small, there is a possibility that an error may occur, using a fixed value,
The effect of suppressing the error from becoming too large and ensuring the stability of the observer can be obtained.

Further, according to the invention of claim 6, according to claim 1,
6. The vehicle behavior detecting device according to any one of claims 1 to 5, wherein the tire stiffness estimating means f has two types of time constants, large and small, when the tire rolling angle is equal to or more than a predetermined value and the side force estimated value is equal to or more than a predetermined value. Is configured to select a smaller time constant for a predetermined time and perform low-pass filtering on the tire stiffness. Therefore, when the steering angle (tire rolling angle) is large, The effect is obtained that the stiffness convergence speed is increased by selecting a constant.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim showing a vehicle behavior detecting device of the present invention.

FIG. 2 is an explanatory diagram of the present invention.

FIG. 3 is a diagram showing a relationship between a side force and a slip angle.

FIG. 4 is an explanatory diagram of an estimated value according to the present invention.

FIG. 5 is an overall view of the vehicle behavior detecting device according to the embodiment.

FIG. 6 is a flowchart illustrating a flow of slip angle detection according to the embodiment.

FIG. 7 is a flowchart illustrating a flow of slip angle detection according to the embodiment.

FIG. 8 is a flowchart showing a flow of slip angle detection according to the embodiment.

FIG. 9 is an explanatory diagram of the embodiment.

[Explanation of symbols]

 a steering angle sensor b lateral acceleration sensor c yaw rate sensor d slip angle estimating means e side force estimating means f tire stiffness estimating means 1 wheel speed sensor 2 wheel speed sensor 3 wheel speed sensor 4 wheel speed sensor 5 steering angle sensor 6 yaw speed sensor 7 lateral acceleration sensor 8 longitudinal acceleration sensor 9 arithmetic unit

Claims (6)

[Claims] 1. A steering angle sensor for detecting a rolling angle of a tire of a vehicle, a lateral acceleration sensor for detecting a lateral acceleration of the vehicle, a yaw rate sensor for detecting a yaw speed around a center of gravity of the vehicle, and a predetermined calculation. A slip angle estimating means for estimating a slip angle of the vehicle, which is an angle formed between the vehicle traveling direction and the front-rear direction of the vehicle, based on an input from each sensor in a cycle. The angle estimating means includes side force estimating means for estimating a side force generated in the tires of the front and rear wheels based on the detected yaw speed and lateral acceleration. Tire stiffness estimating means for estimating tire stiffness by dividing the tire stiffness by a tire slip angle. Vehicle behavior detection apparatus characterized by being configured to estimate a slip angle in the operation period of time based on the previous value of Ifunesu estimate. 2. The slip angle estimating means is configured to calculate a slip angle by dividing an estimated value of a lateral speed of a tire by a speed in a front-rear direction, and calculates a last estimated stiffness value of a previous tire and a current tire stiffness value. 2. The apparatus according to claim 1, wherein the current estimated final stiffness value is determined based on the estimated value, and the lateral speed estimated value is determined based on the final estimated stiffness value.
The vehicle behavior detection device according to any one of the preceding claims. 3. The slip angle estimating means integrates a current lateral speed differential value with a previous lateral speed estimated value to obtain a lateral speed estimated value, and further detects a yaw speed on the integrated value. 3. The vehicle behavior detection device according to claim 2, wherein a feedback error value formed based on a difference between the value and the estimated value is integrated and obtained. 4. The side force estimating means includes a rear wheel side force SFR and a front wheel side force SFR.
FF, YG: lateral acceleration, Kyg: vehicle weight, DYAW: yaw speed, Kyaw: value obtained by dividing the yaw inertia moment of the vehicle by the distance from the vehicle center of gravity to the front wheel axle, Ksf: distance from the vehicle center of gravity to the front wheel axle Is divided by the distance from the front wheel axle to the rear wheel axle. SFR = (YG · Kyg−DYAW · Kyaw) · Ks
4. The vehicle behavior detecting device according to claim 1, wherein the vehicle behavior detecting device is configured to be calculated based on an arithmetic expression of f SFF = -SFR + YG.Kyg. 5. The tire stiffness estimating means is configured to set a predetermined fixed value when the side force falls below a preset threshold value. Vehicle behavior detection device. 6. The tire stiffness estimating means has two types of time constants, large and small, and when the tire rolling angle is a predetermined value or more and the side force estimated value is a predetermined value or more, 6. The vehicle behavior detecting device according to claim 1, wherein a time constant smaller by a set predetermined time is selected, and a low-pass filter process is performed on the tire stiffness.