JP3435625B2 - Road surface condition calculation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately compute a road surface condition to allow stable vehicle control. SOLUTION: This device is provided with respective tables for respective road surface conditions to give the relation among vehicular speed, braking force and fine gain, and coverters 12, 14, 16 to convert input body speeds and detected values of braking force to fine gains based on the tables. This device is also provided with differencers 18, 20, 22 to calculate respective differences between the fine gains for respective road surface conditions converted by respective converters and detected values of input fine gains, and a minimum value selector 24 selecting minimum value among calculated values by the differencers and outputting information of road surface condition corresponding to the converter giving the minimum value. Since the tables provided in the converters 12, 14, 16 show road surface μ characteristics, road surface condition is accurately computed by comparing mutual relation among the vehicular speed, the braking force and the detected value of fine gain with mutual relation indicated in the tables. As a threshold limit value of wheels becomes clear by the road surface condition, stable vehicle control is conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface condition calculating device for calculating a condition of a road surface on which a vehicle is traveling, and more particularly, to a road surface condition calculation method for determining a mutual relationship between a plurality of wheel behavior quantities representing road surface μ characteristics. The present invention relates to a road surface state calculating device which is provided for each of the above and outputs a road surface state based on the mutual relationship.

[0002]

2. Description of the Related Art Conventionally, a wheel is locked by reducing the brake torque acting on the wheel immediately before the friction coefficient μ between the wheel and the road surface exceeds a peak value and the wheel enters a locked state. An anti-lock brake control device has been proposed which prevents and follows the peak μ value.

By the way, when the vehicle is traveling at a certain speed, slipping occurs between the wheels and the road surface when the brake is applied. The friction coefficient μ between the wheels and the road surface is It is known that the slip ratio λ expressed by the equation) changes as shown in FIG.

Λ = (V−V _w ) / V (1) where V is the vehicle body speed (converted to angular velocity), V _w is the wheel speed, and therefore (V−V _w ) is the slip speed Δω.

As shown in FIG. 21, this μ-λ characteristic (hereinafter referred to as road surface μ characteristic) has a certain slip speed (see FIG. 2).
The friction coefficient μ takes a peak value in the A2 region 1).

Therefore, in Japanese Unexamined Patent Publication No. 1-249559, the slip ratio is calculated from the approximate value of the vehicle speed and the detected wheel speed by the equation (1), and the calculated slip ratio is set in advance. An anti-lock brake control device has been proposed which follows the peak μ by controlling the braking force so as to substantially match the reference slip ratio (slip ratio giving the peak μ).

[0007]

However, it is easily expected that the slip ratio, which is the peak μ, varies depending on the type of road surface on which the vehicle is traveling and the state thereof (road surface state). Therefore, when the fixed reference slip ratio follow-up control is performed as in the prior art described in the above publication, the braking distance becomes too large depending on the road surface, or the tire is locked due to braking exceeding the peak μ. May occur.

As a countermeasure against this, it is necessary to estimate and calculate the road surface state and change the reference slip ratio according to the calculated road surface state. However, conventionally, there is no technique for accurately calculating the road surface state.

The present invention has been made in view of the above facts, and an object of the present invention is to provide a road surface state calculating device capable of accurately calculating a road surface state.

[0010]

(Invention of Claim 1) In order to achieve the above-mentioned object, the invention of Claim 1 exhibits a plurality of wheels exhibiting a coefficient of friction μ between a wheel and a road surface with respect to a slip speed. In a road surface state calculating device provided with a mutual relation between behavior amounts for each road surface state, one of the wheel behavior amounts in which the mutual relation is shown is a gradient of a friction coefficient μ with respect to a slip speed or a physical quantity related to the gradient. And a table showing the interrelationships between multiple wheel behaviors.
Prepare for each slip speed,
The deviation is determined by the table for each slip speed.
Wheel behavior for each slip speed obtained by conversion
Comparison of the converted value of the quantity and the detected value of the same quantity as the wheel behavior quantity
Slip speed is calculated based on
A conversion value of the wheel motion amount obtained for each road surface state by converting the at least any of the detection values of the plurality of wheel movements amount input to the speed by correlation for each of the road surface condition, the wheel behavior A road surface calculating means for calculating and outputting a road surface state based on a comparison between the amount and the detected value of the same amount.

Here, the characteristic of the friction coefficient μ between the wheel and the road surface with respect to the slip speed Δω means the Δω-μ characteristic shown in FIG. 17, and all other characteristics equivalent to the characteristic. (Hereinafter referred to as “road surface μ characteristic”). This Δ
As a characteristic equivalent to the ω-μ characteristic, for example, the characteristic shown in FIG. 21 expressed by a slip ratio instead of the slip speed, and a braking force (μW: W is a wheel load) related to μ instead of the friction coefficient μ, Braking torque (μWr: r is the effective radius of the wheel)
There is a characteristic expressed in. As shown in FIG. 2 (a), the road surface μ characteristic shows that the dry road surface (Dry) and the snow road surface (Sn) are
ow), ice road (Ice). ． ． It shows different characteristics depending on the road condition.

The wheel behavior quantity is a physical quantity related to the wheel motion, which is necessary for expressing the road surface μ characteristic. For example, vehicle body speed, wheel speed, wheel deceleration (acceleration), slip speed, The braking force, the braking torque, the gradient of the road surface μ with respect to the slip ratio, the gradient of the braking torque with respect to the slip speed, the brake pressure (wheel cylinder pressure), and the like.

These wheel behavior quantities are selected so as to be necessary and sufficient for expressing the road surface μ characteristic which has a constant relationship for each road surface state. Therefore, the mutual relationship between the wheel behavior quantities is determined for each road surface state. It directly or indirectly represents the road surface μ characteristic of

For example, the road surface μ characteristic of FIG.
As shown in (b), first, it can be expressed for each road surface state by the mutual relationship between the braking force P _c which is another wheel behavior amount and the slip ratio λ. Then, in FIG. 2A, not only the μ value but also the gradient G _d of the road surface μ with respect to the slip ratio has a unique value depending on the road surface state, and using the relationship of FIG. 2B. , The road surface μ characteristic of FIG. 2A is sufficiently and sufficiently represented by a three-dimensional characteristic for each road surface state represented by the braking force, the vehicle body speed, and the road surface μ gradient G _d , as shown in FIG. 2C. be able to.

Since the slip ratio λ can be expressed from the vehicle body speed and the wheel speed, when the braking force is used as one of the wheel behavior amounts, another other wheel behavior amount is required,
In the example of FIG. 2C, the vehicle speed is used.

In FIG. 2C, this three-dimensional characteristic is represented by the relationship between the braking force and the road surface μ gradient G _d for each of the vehicle body speeds V of 20 km / h, 40 km / h and 60 km / h. From this figure, it is understood that the relationship between these three wheel behavior amounts differs depending on the road surface condition.

In the present invention, such a mutual relationship among a plurality of wheel behavior quantities representing the road surface μ characteristic is provided for each road surface state. Note that this mutual relationship can be represented by, for example, a conversion table between input / output data, and in the case of the characteristic of FIG. 2C, the relationship between the braking force and the road surface μ gradient for each vehicle speed and each road surface state. Is created in advance based on the data obtained by detecting.

When the road surface state is calculated when the wheel behavior amount such as the vehicle speed is constant, it is possible to reduce the number of wheel behavior amounts which show a mutual relationship.

Here, the road surface calculating means of the present invention can be configured so that a plurality of wheel behavior quantities are input.
For example, as shown in FIG. 1, the vehicle speed V detected by the vehicle speed detecting means, the road surface μ gradient G _d detected by the road surface μ gradient detecting means, and the braking force P _c detected by the braking force detecting means are the road surface. It is configured to be input to the calculation means.

When the detected values of the plurality of wheel behavior amounts are input, the road surface calculation means determines at least one (one or more) of the input detected values of the plurality of wheel behavior amounts as a mutual relation for each road surface state. Based on each. as a result,
The conversion value of the wheel behavior amount other than the wheel behavior amount that is the conversion target is obtained for each road surface state. For example, in the configuration of FIG. 1, when converting the vehicle body speed and the braking force according to the mutual relationship of FIG. 2C, the road surface corresponding to the detected value V = 20 km / h of the vehicle body speed and the detected value P _c0 of the braking force. The converted values of μ gradient are G _d1 and G for dry road surface, snow road surface and ice road surface respectively.
It becomes _d2 and G _d3 .

Then, the road surface calculating means calculates the road surface state based on the comparison between the converted value of the wheel behavior amount for each road surface state thus obtained and the detected value of the same amount as the wheel behavior amount. . For example, in the case of the above example, the conversion values G _d1 , G _d2 , and G _d3 of the road surface μ gradient for each road surface state are compared with the detection value G _d0 of the road surface μ gradient detected by the road surface μ gradient detecting means, and this The road condition is calculated and output according to the comparison result.

In this comparison, for example, the difference between the detected value G _d0 and the converted values G _d1 , G _d2 , and G _d3 is calculated, and the road surface state having the smallest difference (absolute value) is calculated. For example G
_When the difference between _d2 and _Gd0 is the smallest, it is calculated that the road surface state is "snow road surface (Snow)".

Further, the invention of claim 1 is characterized in that one of the plurality of wheel behavior quantities in which the mutual relationship is shown is a gradient of a friction coefficient μ with respect to a slip speed or a physical quantity related to the gradient. There is.

Since the gradient of the friction coefficient μ with respect to the slip speed (road surface μ gradient) has a unique value depending on the road surface condition as described above, it is an effective wheel behavior amount when calculating the road surface condition. Further, although it is difficult to directly detect the friction coefficient μ, the road surface μ gradient is an effective method for calculating it using time-series data of wheel speed using an online system identification method (Japanese Patent Application No. 8-218828). Since the invention can be applied, the road surface condition can be calculated more accurately by using the road surface μ gradient.

Here, the friction coefficient μ with respect to the slip speed
As a physical quantity related to the gradient of, for example, braking torque (or braking force) with respect to slip speed (or slip ratio)
There is a gradient of. (Invention of Claim 2) In the invention of Claim 2, in addition to the invention of Claim 1, a micro-excitation means for micro-exciting the braking force at the resonance frequency of the vibration system composed of the vehicle body, the wheels, and the road surface. And a physical quantity related to the gradient of the friction coefficient μ is a ratio of a minute amplitude of the resonance frequency component of the wheel speed to a minute amplitude of the braking force when the minute excitation means minutely excites the braking force. Characterize. Oscillation of the wheel when the vehicle having a vehicle body (claim principles of the invention 2) weight W _v is traveling at a vehicle speed omega _v,
That is, the vibration phenomenon of the vibration system constituted by the vehicle body, the wheels, and the road surface is equivalently modeled by the wheel rotation axis in FIG.
Consider the model shown in FIG.

In the model of FIG. 16, the braking force is
Acts on the road surface via the surface of the tread 115 of the tire in contact with the road surface, the equivalent of this for braking force actually acting on the vehicle body as a reaction (braking force) from the road surface, the rotation shaft conversion of vehicle weight W _v The model 117 is connected to the side opposite to the wheel 113 via a friction element 116 (road surface μ) between the tread of the tire and the road surface. This is similar to the case where a chassis dynamo device can simulate the weight of a vehicle body with a large inertia under a wheel, that is, a mass on the side opposite to the wheel.

In FIG. 16, the inertia of the wheel 113 including the tire rim is J _w , and the spring element 1 between the rim and the tread 115 is shown.
The spring constant of 14 is K, the wheel radius is R, the inertia of the tread 115 is J _t , and the friction element 1 between the tread 115 and the road surface is 1.
Assuming that the friction coefficient of 16 is μ and the inertia of the equivalent model 117 of the weight of the vehicle body in terms of the rotation axis is J _V , the transfer characteristic from the brake torque T _b 'generated by the wheel cylinder pressure to the wheel speed ω _w is From the equation,

[0028]

[Equation 1]

It becomes Note that s is a Laplace transform operator. When the tire grips the road surface, assuming that the tread 115 and the vehicle body equivalent model 117 are directly connected, the sum inertia of the vehicle body equivalent model 117 and the tread 115 and the inertia of the wheel 113 resonate. . That is, this vibration system can be regarded as a wheel resonance system including wheels, a vehicle body, and a road surface. The resonance frequency ω ∞ of the wheel resonance system at this time is expressed by ω ∞ = √ {(J _w + J _t + J _v ) K / J _w (J _t + J _v )} / 2π (3 ). This state is the peak μ in FIG. 17 (FIG. 21).
Corresponding to the area A1 before reaching.

On the contrary, when the friction coefficient μ of the tire approaches the peak μ, the friction coefficient μ of the tire surface is less likely to change with respect to the slip ratio, and the component accompanying the vibration of the inertia of the tread 115 is the vehicle body equivalent model. 117 is no longer affected. That is, the tread 115 and the vehicle body equivalent model 117 are equivalently separated, and the tread 115 and the wheel 113 resonate. It can be considered that the wheel resonance system at this time is composed of the wheels and the road surface, and the resonance frequency ω ∞ ′ is equal to the vehicle body equivalent inertia J _v in Equation (3).
It will be equal to That is, ω ∞ ′ = √ {(J _w + J _t ) K / J _w J _t )} / 2π (4). This state is the peak μ in FIG. 17 (FIG. 21).
It corresponds to the area A2 in the vicinity.

Comparing equations (3) and (4), the equivalent body inertia J
_vIs the wheel inertia J_w, Tread inertia J _tAssume greater than
Then, the resonance frequency ω ∞ ′ of the wheel resonance system in the case of equation (4)
Is to shift to the higher frequency side than ω∞ than Eq. (3)
become. Therefore, the change in the resonance frequency of the wheel resonance system is reflected.
The frictional state between the wheels and the road surface
It becomes possible to judge.

Therefore, in the present invention, the following minute gain G _d is introduced as a wheel behavior amount as a physical amount that reflects such a change in the resonance frequency.

First, when the minute excitation means minutely excites the braking force at the resonance frequency ω∞ (equation (3)) of the vibration system composed of the wheel, the vehicle body and the road surface (here, when the braking pressure P _b is minutely excited). Yes, the wheel speed ω _w also slightly vibrates around the average wheel speed at the resonance frequency ω ∞. Here, the minute amplitude of the resonance frequency ω ∞ of the brake pressure P _b at this time is P
Let _{v be} the minute amplitude of the resonance frequency ω∞ of the wheel speed be ω _wv, and let the minute gain G _d be G _d = ω _wv / P _v (5). It should be noted that this minute gain G _d is applied to the brake pressure P _b.
Resonance frequency ω of the ratio (ω _w / P _b ) of wheel speed ω _w to
It can also be expressed as G _d = ((ω _w / P _b ) | s = jω∞) (6) by regarding it as a vibration component of ∞.

Since this minute gain G _d is an oscillating component of the resonance frequency ω ∞ of (ω _w / P _b ) as shown in the equation (6), when the friction state reaches a region near the peak μ, Since the resonance frequency shifts to ω∞ ', it sharply decreases. That is, it can be said that the minute gain G _d is a wheel behavior amount that sensitively reflects the frictional state that defines the road surface μ characteristic.

Next, it will be explained that the minute gain G _d is a physical quantity equivalent to a braking torque gradient (gradient of braking torque with respect to slip speed), which is one expression of the road surface μ gradient.

As described above, in the characteristic of FIG. 17, the slip speed Δω and the friction coefficient μ between the wheel and the road surface have a functional relationship in which the friction coefficient μ peaks at a certain slip speed. .

By the way, when the brake pressure is slightly excited by the minute excitation means, the wheel speed is minutely excited, so that the slip speed also vibrates slightly around a certain slip speed. Now, let us consider a change in the friction coefficient μ with respect to the slip speed Δω when the vehicle vibrates slightly around a certain slip speed on the road surface having the characteristics shown in FIG.

At this time, the friction coefficient μ of the road surface can be approximated as μ = μ ₀ + αRΔω (7). That is, since the change of the slip speed due to the minute vibration is small, it can be approximated by the straight line of the inclination αR.

Here, by substituting the expression (7) for the braking torque T _b = μWR generated by the friction coefficient μ between the tire and the road surface, T _b = μWR = μ ₀ WR + αR ² ΔωW (8) Here, W is the wheel load. Δ on both sides of equation (8)
Differentiating the first order with ω,

[0040]

[Equation 2]

To obtain Therefore, it was shown from the equation (9) that the braking torque gradient (dT _b / Δω) was equal to αR ² W.

On the other hand, since the brake torque T _b 'is proportional to the brake pressure P _b , the minute gain G _d is the ratio of the wheel speed ω _{w to} the brake torque T _b ' (ω _w /
It has a proportional relationship with the vibration component of the resonance frequency ω ∞ of T _b '). Therefore, due to the transfer characteristics of equation (2), a small gain G _d
Is represented by the following equation.

[0043]

[Equation 3]

Generally, in equation (12),       | A | = 0.012 <<< | B | = 0.1 (13) Therefore, from equations (9) and (10),

[0045]

[Equation 4]

To obtain That is, the gradient of the braking torque T _b with respect to the slip speed Δω is proportional to the minute gain G _d .

[0047] Thus, micro-gain G _d is shown to be equivalent to a physical quantity and the road surface μ gradient (the braking torque gradient), it is understood that the road surface condition can be accurately calculated based on the micro-gain G _d. Moreover, this minute gain G _d
Is a wheel behavior amount that accurately represents the frictional state based on the resonance characteristic of the vibration system, and thus according to the present invention, the road surface state can be calculated more accurately. (Invention of Claims 3 to 6) The invention of Claim 3 is a vehicle speed detection calculation means for detecting a vehicle speed.
And a wheel behavior amount detecting means for detecting a wheel behavior amount, and a road surface.
road surface μ gradient detecting means for detecting μ gradient, road surface μ gradient,
A table showing the relationship between vehicle speed and wheel behavior for each road surface condition.
Based on the vehicle speed detected by the vehicle speed detection means,
With the wheel behavior amount detected by the wheel behavior amount detection means,
Road surface μ gradient that outputs the road surface μ gradient for each corresponding road surface condition
The output means and the road surface μ coefficient detected by the road surface μ detecting means
Distribution and the road surface state output from the road surface μ gradient output means
The road surface condition when the difference between the
And a road surface state selecting means for selecting. Claim 4
According to the invention of claim 3, in the invention of claim 3,
The output means detects the braking force as the wheel behavior amount,
The vehicle speed detection means uses the slip relationship between the road surface μ gradient and the braking force.
Based on the table shown for each wheel speed,
For each slip speed corresponding to the braking force detected by the detection means
Second road surface μ gradient output means for outputting the road surface μ gradient of
The road surface μ gradient detected by the road surface μ detection means and the second
For each slip speed output from the road surface μ gradient output means
The relevant slip speed when the difference from the road surface μ gradient becomes minimum
And a slip speed selecting means for selecting
The wheel speed can be added to the slip speed selected by the means.
And a vehicle speed calculation means for calculating the vehicle speed with
To collect. The invention of claim 5 is the invention of claim 3 or 4.
Shows the relationship between maximum braking force and vehicle speed for each road surface condition.
Detected by the vehicle speed detection means based on the table
Output the maximum braking force for each road surface condition corresponding to the vehicle speed.
Output from the large braking force output means and the maximum braking force output means
From the maximum braking force for each road surface condition
The maximum braking force corresponding to the road surface condition selected by the selection means
And a maximum braking force selecting means for selecting.
To collect. The invention of claim 6 is the same as the invention of claim 5.
The maximum of the predetermined wheels selected by the maximum braking force selection means.
Predetermined vehicle detected by the large braking force and the wheel behavior amount detection means
Based on the difference with the braking force of the wheels,
Further, a braking force allowance calculation means for calculating the allowance is further provided.
Is characterized by. Other aspects 1 (Other embodiments of the present invention) The present invention includes a second table showing the correlation between the two wheel movements of other vehicles velocities for each slip speed, and the two wheel movements Based on a comparison between the converted value of the wheel behavior amount for each slip speed obtained by converting any of the amounts by the second table for each slip speed, and the detected value of the same amount as the wheel behavior amount. A plurality of wheel behavior quantities which further include a vehicle speed calculating means for calculating a slip speed and calculating a vehicle body speed based on the calculated slip speed and the input detected value of the wheel speed. One of them is the vehicle body speed, and the road surface calculating means calculates the road surface state using the vehicle body speed calculated by the vehicle speed calculating means.

The vehicle speed calculating means of the first aspect includes a second table for each slip speed, which shows a mutual relationship between two wheel behavior amounts other than the vehicle body speed. This second table is
When the two wheel behavior amounts other than the vehicle body speed are the braking force P _c and the road surface μ gradient G _d , they can be created by the following procedure.

First, when the change of the slip speed Δv with respect to the braking force P _{c is} obtained in each case where the road surface condition and the vehicle body speed (vehicle speed) are variously changed, the relationship shown in FIG. 4 is obtained. Next, in each case where the road surface state and the vehicle speed are variously changed as parameters, the change in the road surface μ gradient G _d with respect to the slip speed Δv is calculated.
5 (a) (Dry) and FIG. 5 (b) (Snow).

From the relationships shown in FIGS. 4 and 5, P _c and G _d for the same slip speed Δv are obtained for each vehicle speed, and as shown in FIGS. 6 (a) and 6 (b) for each road surface condition. It becomes a relationship. P _{c for} each slip speed shown in FIG. 6
And the relationship between G _d and the second table. The line of each Δv in FIG. 6 is fixed regardless of the vehicle speed and the road surface.

Further, based on FIGS. 6 (a) and 6 (b), FIGS. 7 (a) to 7 (c) are shown for each vehicle speed (20 km / h, 40 km / h, 60 km / h).
The relationship between P _c and G _d is shown for each road surface condition.
The relationship shown in FIG.
It corresponds to the table for each road surface condition when _c and G _d are set.

In the first aspect, for example, the road surface μ gradient G for each slip speed obtained by converting the detected value of the braking force P _c by the second table for each slip speed.
_The slip speed is calculated based on the comparison between the converted value of _{d and} the detected value of the road surface μ gradient G _d . That is, the detected P
The relationship between _c and G _d is calculated to which Δv line in FIG. 6 is closest, and the Δv value of the line that is closest is calculated as the slip speed.

Since the slip speed can be calculated in this manner, the vehicle speed calculating means of the first aspect calculates the vehicle speed based on the calculated slip speed and the input detected wheel speed value. Then, the road surface calculating means calculates the road surface state based on the table, using the vehicle body speed calculated by the vehicle speed calculating means. I.e., the case of the table of FIG. 7, the relationship between the detected P _c and G _d are, of relationship between P _c and G _d, which corresponds to the vehicle speed which is calculated, closest to the relationship which the road surface condition Is calculated to obtain the road surface state corresponding to the closest relationship.

As described above, in the present mode 1, the vehicle speed is set to the vehicle speed.
Despite having a table that is one of the wheel movement quantities,
You don't have to detect body speed, instead wheel speed
Will be detected. That is, the road surface calculation of the first aspect
For example, as shown in FIG.
Detected wheel speed V_w, Road surface μ gradient detection means
Detected road gradient μ_d, And braking force detection means
Detected braking force P _cIs input to the road surface calculation means
Can be configured as

Since it is difficult to accurately estimate the vehicle body speed as compared with the wheel speed, by estimating the vehicle body speed based on the second table and the wheel speed as in the first aspect,
As compared with the case of FIG. 1 in which the vehicle speed is input as the detected value, more accurate calculation of the road surface state becomes possible.

Further, in the present mode 1, since an accurate slip speed can also be obtained, by applying it to an anti-lock brake control device for controlling the slip ratio to match the reference slip ratio, a more accurate control can be achieved. Is possible.

In each of the above inventions, the road surface condition is calculated. However, the road surface calculating means converts the peak μ value (μmax value) for each road surface condition previously stored as data into the calculated road surface condition. The corresponding peak μ value may be further obtained together with the road surface condition.

As a result, the road surface condition and the peak μ value can be known, so that the limit value of the wheel becomes clear, and VSC, A
It is possible to change the control gain in vehicle stabilization control such as BS (anti-lock brake control) and TRC (traction control), set a control target value, and warn the driver of the road surface condition.

Further, the maximum braking force corresponding to the road surface state and the vehicle body speed calculated by the road surface calculating means is obtained from the road surface state and the maximum braking force for each vehicle body speed which are previously stored as data, and the maximum braking force is calculated. It is also possible to configure the road surface state calculating device so as to further include a braking force margin calculating means for calculating and outputting the difference between the detected braking force and the detected braking force (the other aspect 2 of the present invention).

Here, the invention of the second aspect can be configured as shown in FIG. 8, for example. As shown in the figure, the road surface calculating means includes a vehicle body speed V, a road surface μ gradient G _d , and a braking force P _c.
Is input, and as described above, the road surface calculation means calculates the road surface state based on these wheel behavior amounts and the table. Then, the road surface condition is transmitted to the braking force margin calculating means of the present invention.

The braking force allowance calculation means converts the maximum braking force for each road surface state and vehicle body speed, which is provided in advance as data, to the road surface state calculated by the road surface calculation means and the vehicle body speed detected by the vehicle speed detection means. The maximum braking force selecting means for obtaining the corresponding maximum braking force and the difference means for subtracting the braking force detected by the braking force detecting means from the obtained maximum braking force can be configured.

Here, the maximum braking force has a unique value for each road surface condition, and the unique value also differs for each vehicle speed.
For example, road condition (Dry, Snow, Ice), vehicle speed (40km / h, 60k
Maximum braking force (PcMax1, PcMax2, PcMax3) according to m / h)
Changes as shown in FIG. The maximum braking force selecting means is previously provided with the maximum braking force for each road surface state and vehicle body speed as shown in FIG. 9, and the maximum braking force corresponding to the input road surface state and vehicle body speed is obtained. You can Then, the difference means subtracts the detected braking force from the obtained maximum braking force to obtain the braking force margin. This margin is an index of how much braking force can be applied to the wheels.

When the second aspect is applied to the invention of the first aspect, a more accurate maximum braking force can be obtained by using the vehicle body speed calculated by the vehicle speed calculating means.

As described above, according to the other aspect 2 of the present invention, it is possible to know the margin of the braking force.
By performing control to distribute the braking force and the driving torque preferentially to the wheel having a high margin, more stable vehicle traveling becomes possible.

[0065]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a road surface state calculating device of the present invention will be described in detail below with reference to the drawings. In the embodiment, it is assumed that the road surface state calculating device is applied to a vehicle. (First Embodiment) FIG. 10 is a block diagram showing the configuration of a road surface state calculating device according to the first embodiment of the present invention. The configuration of the first embodiment is a concrete implementation of the configuration of FIG.

As shown in FIG. 10, the road surface condition calculating apparatus 10 according to the first embodiment has a slope ∂μ / ∂Δv of the road surface μ with respect to the slip speed Δv (or slip ratio) (in the present embodiment, Minute gain G _d ), braking force P _c ,
And the relationship between the vehicle body speed V and the three wheel behavior quantities ∂μ /
∂Δv table for dry road (Dry), snow road (Snow),
The conversion unit 12, which stores the ice road surface (Ice),
14 and 16 are provided.

When the vehicle body speed and the braking force are input, the conversion units 12, 14, and 16 use the functional relationship table (see FIG. 2 (c)) stored therein as shown in FIG. Micro gains G _d1 , G _d2 corresponding to this input value,
G _d3 (In FIG. 10, with ∧ indicating estimation; ∧ is omitted below)
Are output respectively.

It should be noted that this conversion unit can be configured as a ROM that stores all conversion values for input values in a predetermined range in advance and, when data is input, outputs conversion values corresponding to the values of the data. . Further, it may be configured by a neural network capable of learning a non-linear function such as a ∂μ / ∂Δv table, or an applied filter.

Further, the road surface state computing device 10 converts the detected value G _d of the minute gain input to the device into the conversion unit 12,
Micro gains G _d1 , G _d2 , and G converted by 14 and 16
By subtracting _d3 respectively, the difference G _d −G _d1 , G
_d -G _d2, G _d -G _d3 each operation to the differentiator 18,2
0 and 22 are provided.

Further, the road surface state calculating device 10 is provided with a minimum value selecting section 24 for selecting the minimum value from the absolute values of the differences calculated by the difference units 18, 20, 22.
The minimum value selection unit 24 identifies the conversion unit that has output the minute gain with the minimum value, and outputs the road surface state information corresponding to this conversion unit.

Outside the road surface condition computing device 10,
A vehicle speed detecting unit 26 for detecting a vehicle speed, a braking force detecting unit 34 for detecting a braking force acting on wheels, and a minute gain calculating unit 36 as a road surface μ gradient detecting unit of FIG. 1 are prepared. The vehicle speed detection unit 26 and the braking force detection unit 34 are connected to the conversion units 12, 14, 16 respectively, and the minute gain calculation unit 36 is connected to the difference units 18, 20, 22 respectively.

Among these, the vehicle speed detection unit 26 detects the wheel speed, the wheel speed sensor 28, the braking start determination unit 30 that determines when the driver depresses the brake pedal as the braking start time, and the detection at the determined braking start time. The braking start vehicle speed determining unit 32 outputs the determined wheel speed V _w as the vehicle body speed V. That is, the vehicle speed detection unit 26 of the present embodiment estimates the vehicle body speed by assuming that the wheel speed at the start of braking is substantially equal to the vehicle body speed. The vehicle speed detection unit 26 may be directly configured as a vehicle speed sensor that detects the vehicle speed.

Further, the braking force detector 34 estimates the braking force acting as a frictional force on the wheels from the road surface according to the mechanical model of the wheels as follows.

That is, the brake torque T _B acting on the wheel in the direction opposite to the wheel rotation direction, and the tire torque T _f due to the braking force F acting on the wheel in the wheel rotation direction as a frictional force are applied to the wheel. , Act. The brake torque T _B is derived from the braking force acting on the brake disc of the wheel so as to prevent the rotation of the wheel, and the braking force F and the tire torque T _f are the friction coefficient between the wheel and the road surface. Where μ _{B is} the wheel radius is r and the wheel load is W, it is expressed by the following equation.

F = μ _B W T _f = F × r = μ _B Wr Therefore, the equation of motion of the wheel is

[0076]

[Equation 5]

It becomes However, I is the moment of inertia of the wheel, and ω is the rotational speed (wheel speed) of the wheel.

If the wheel acceleration (dω / dt) is detected and the brake torque T _B is obtained based on the wheel cylinder pressure applied to the brake disc, the braking force F can be estimated based on the equation (15). Specifically, a dynamic model equivalent to equation (15) in which the driving torque of the wheel obtained from the accelerator opening and the braking force F as a disturbance acts on the wheel is configured as an observer. In this observer, (15)
The disturbance and the rotation speed of the equivalent model are corrected for each control cycle so that the deviation between the rotation position obtained by second-order integration of the equation and the actually detected rotation position matches 0, and the corrected disturbance is Estimated as braking force.

Further, the fine gain calculation section 36 is arranged to
-Vibration composed of vehicle body, wheels, and road surface around pressure
Micro-excitation of brake pressure with system resonance frequency ω∞ (Equation (3))
Wheel speed V when_wResonance frequency of ω ∞ Small amplitude
(Wheel speed minute amplitude ω_wv) Wheel speed minute amplitude detection
And the minute amplitude P of the brake pressure at the resonance frequency ω∞ _v
Brake pressure minute amplitude detecting section 42 for detecting
Wheel speed minute amplitude ω_wvBrake pressure small amplitude P_vDivide by
By setting a small gain G_dDivider 44 for outputting
It consists of and.

Of these, the wheel speed minute amplitude detection section 40 can be realized as a calculation section for performing a filter process for extracting a vibration component of the resonance frequency ω∞. For example, since the resonance frequency ω ∞ of this vibration system is about 40 [Hz], one cycle is set to 24 [ms] and about 41.7 [Hz] in consideration of controllability, and this frequency is set as the center frequency. A band pass filter is provided, and the output of this filter is subjected to full-wave rectification and DC smoothing to output a small wheel speed amplitude. In addition, an integral multiple of the cycle, for example, one cycle of 24 [ms] and two cycles of 48 [m
[s] time series data is continuously taken in, and 41.7 [H
It can also be realized by obtaining the correlation with the unit sine wave and the unit cosine wave of z].

[0081] Here, a description will be given small excitation means for applying a brake pressure differential small amplitude P _v of the resonance frequency around the mean braking pressure P _m. First, as shown in FIG. 18, the portion (valve control system) that converts the average brake pressure command and the minute excitation command into the braking torque for the actual wheel is a master cylinder 48, a control valve 52, a wheel cylinder 56, and a reservoir 58. And an oil pump 60.

Of these, the brake pedal 46 is a master cylinder 48 whose pressure is increased according to the pedaling force of the brake pedal 46.
It is connected to the pressure increasing valve 50 of the control valve 52 via. Further, the control valve 52 is connected to a reservoir 58 as a low pressure source via a pressure reducing valve 54. Furthermore, the control valve 52 is connected to a wheel cylinder 56 for applying the brake pressure supplied by the control valve to the brake disc. The control valve 52 controls opening / closing of the pressure increasing valve 50 and the pressure reducing valve 54 based on the input valve operation command.

The control valve 52 is the pressure increasing valve 5.
When controlled to open only 0, wheel cylinder 5
The hydraulic pressure of 6 (wheel cylinder pressure) is proportional to the hydraulic pressure of the master cylinder 48 (master cylinder pressure) obtained by the driver depressing the brake pedal 46.
Rise to. On the contrary, when the pressure reducing valve 54 is controlled to open only, the wheel cylinder pressure is reduced to almost the atmospheric pressure of the reservoir 58 (reservoir pressure). Further, when both valves are controlled to be closed, the wheel cylinder pressure is maintained.

The braking force (corresponding to the wheel cylinder pressure) applied to the brake disc by the wheel cylinders 56 is the pressure increasing time during which the high hydraulic pressure of the master cylinder 48 is supplied, the pressure decreasing time during which the low hydraulic pressure of the reservoir 58 is supplied,
And the ratio of the holding time for which the supplied hydraulic pressure is held, and the master cylinder pressure and the reservoir pressure detected by the pressure sensor or the like.

Therefore, by controlling the pressure increasing / decreasing time of the control valve 52 according to the master cylinder pressure, a desired brake torque can be realized. Then, the minute excitation of the brake pressure can be performed by simultaneously performing the pressure increasing / decreasing control of the control valve 52 for realizing the average braking force and the pressure increasing / decreasing control at a cycle corresponding to the resonance frequency.

As a concrete content of control, as shown in FIG. 19, each mode of pressure increase and pressure decrease is switched every half cycle T / 2 of the cycle of minute excitation (for example, 24 [ms]), and the valve is turned on. decrease pressure command, the moment between the pressure boosting t _i of mode switching, and outputs the respective just time period the pressure increase, pressure reduction command decompression time t _r, the rest of the time, and outputs the held command. The average braking force, as well as determined by the ratio of the pressure increasing time t _i corresponding to the master cylinder pressure and the decompression time t _r, by switching the pressure-increasing-decreasing mode of the half period T / every 2 corresponding to the resonance frequency, the average Small vibrations are applied around the braking force.

The brake pressure minute amplitude P_vIs the master
Cylinder pressure, valve pressure increase time t shown in FIG._iThe long
And decompression time t_rDepending on the length of the
Therefore, the brake pressure minute amplitude detection unit 42 in FIG.
Star cylinder pressure, pressure increase time t _iAnd decompression time t_rKarabu
Rake pressure small amplitude P_vAs a table that outputs
You can

Further, in the road surface state computing device 10 of the first embodiment, the peak μ search unit 61 as shown in FIG.
Can be provided. The peak μ search unit 61 stores the peak μ value and the slip ratio data for giving the peak μ for each road surface condition, and the address table 63 showing the address of the data for each road condition based on the memory 61. And a data search unit 62 for searching data.

Next, the operation of the first embodiment will be described.
It The vehicle speed V detected by the vehicle speed detector 26 and the control
Braking force P detected by power detector 34_cBut the road surface
It is input to each conversion unit 12, 14, 16 of the state calculation device 10.
Then, each conversion unit is assigned to each ∂μ / ∂Δv
With the table, the two input detection values are converted and
Micro gain G corresponding to these detected values_d1, G _d2, G_d3To
Output each.

When the minute gains G _d1 , G _d2 , and G _d3 that have been converted and the minute gains G _d calculated by the minute gain calculator 36 are input to the differentiators 18, 19 and 20, respectively, these differences are calculated. The difference is G _d −G _d1 , G _d −
G _d2 and G _d −G _d3 are respectively calculated, and the minimum value selection unit 24
Output to.

The minimum value selection unit 24 selects the difference with the smallest absolute value from the calculated differences, and specifies the conversion unit that gave the selected minimum difference value. Then, the road surface state corresponding to the specified conversion unit is output as an information code in a predetermined format. The information code represented in this format corresponds to any of Dry, Snow, and Ice, and is represented in a format that can be recognized by the control unit of the vehicle to which the road surface state calculation device 10 is applied. For example, if the G _d -G _d3 becomes the minimum value, the road surface condition is to output the information code of "Ice". Since the ∂μ / ∂Δv table showing the mutual relationship among the vehicle speed, the braking force, and the minute gain accurately shows the road surface μ characteristic, the ∂μ / ∂Δv table can be obtained as in the present embodiment. By comparing the relationship between the wheel behavior amounts shown and the relationship between the actual detected values, the road surface condition can be obtained extremely accurately. Further, in the present embodiment, the minute gain G that sensitively represents the friction state based on the resonance characteristic of the vibration system.
_{Since d} is used, it is possible to more accurately obtain the road surface condition as compared with the case where other wheel behavior quantities are used.

In the peak μ search unit 61, the data search unit 62 interprets the road surface state information code output by the minimum value selection unit 24, and from the address table 63,
The address corresponding to the information code is read. And
The data search unit 62 searches and outputs the peak μ value and the slip ratio of the corresponding address in the memory 64. That is,
The output data is the peak μ value of the currently running road surface,
And the slip ratio that gives the peak μ on the road surface.

As described above, according to the present embodiment, the road surface condition and the peak μ value of the road surface on which the vehicle is currently traveling can be accurately obtained. Therefore, the stabilization control of the vehicle such as VSC, ABS, TRC and the like to the driver can be performed. By using this calculation result for a warning or the like, safe traveling can be performed regardless of the road surface condition.

In the example of FIG. 10, the vehicle body speed, the braking force, and the minute gain are used as the wheel behavior amount, but the present invention is not limited to this. For example, in FIG.
It is also possible to configure as follows.

In FIG. 11, the slip speed is used as one of the wheel behavior quantities instead of the braking force. Therefore, FIG.
The conversion units 13, 15, and 17 are each provided with a ∂μ / ∂Δv table showing the relationship among the vehicle body speed, the slip speed, and the minute gain. Then, instead of the braking force detection unit 34, a slip speed calculator 38 that calculates a slip speed from the wheel speed detected by the wheel speed sensor 28 and the vehicle body speed determined by the braking start vehicle speed determination unit 32 is provided, and the slip The speed calculator 38 is connected to the conversion units 13, 15, and 17, respectively.

Also in the configuration of FIG. 11, the slip speed,
Since the road surface μ characteristic can be expressed from the vehicle speed and the minute gain, the road surface state can be accurately calculated.
Further, since the braking force detection unit 34 may be omitted and a slip speed calculator configured by a simple arithmetic unit may be provided instead of the braking force detection unit 34, the entire apparatus can be simplified. (Second Embodiment) FIG. 12 is a block diagram showing the configuration of a road surface state calculating device according to a second embodiment of the present invention, which embodies the configuration of FIG. The same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 12, the road surface state computing device 10b according to the second embodiment includes the wheel speed V _w detected by the wheel speed sensor 65 and the braking force P detected by the braking force detector 34. A vehicle speed calculation unit 70 that calculates the vehicle body speed V from _c and a road surface state calculation that calculates the road surface state from the vehicle body speed V calculated by the vehicle speed calculation unit 70, the detected braking force P _c, and the minute gain G _d. It is composed of the unit 80.

Of these, the vehicle speed calculation unit 70 shows Δv indicating the relationship between the braking force and the minute gain for each constant slip speed (0.1 m / s, 0.4 m / s, 0.8 m / s, ...). The conversion units 71, 72, 73 ,. ． ． ． ． Is equipped with.

The conversion units 71, 72, 73 ,. ． ． Is
When the detected braking force is input, the Δv table (FIG.
(A) and (b)), the minute gains G _d1 , G _d2 , G _d3 ,. ． ． ． ． (In FIG. 12, ∧ indicating estimation; hereinafter, ∧ is omitted) is output.

Further, the vehicle speed calculation unit 70 converts the detection value G _d of the minute gain input to the device into the conversion units 71, 72,
73 ,. ． ． ． ． Micro gains G _d1 , G converted by
_d2 , G _d3 ,. ． ． ． By subtracting from each other, the differences G _d −G _d1 , G _d −G _d2 , G _d −G _d3 ,. ． ． ． Is provided with differentiators 74, 75 and 76, respectively.

Further, the vehicle speed calculation unit 70 includes a difference unit 74,
75, 76 ,. ． ． The minimum value selection unit 77 is provided for selecting the minimum value from the absolute values of the differences calculated by. The minimum value selection unit 77 identifies the conversion unit that has output the minute gain to which the minimum value has been given, and outputs the slip speed Δv corresponding to this conversion unit.

A vehicle speed calculator 78 is connected to the minimum value selection unit 77. The vehicle speed calculator 78 calculates the vehicle body speed V by adding the wheel speed V _w detected by the wheel speed sensor 65 to the slip speed Δv output by the minimum value selection unit 77.

As shown in the figure, the slip speed Δv output by the minimum value selecting unit 77 and the vehicle body speed V calculated by the vehicle speed calculator 78 can be output to the outside of the road surface computing device 10b. Further, a divider 81 that outputs the slip ratio λ by dividing the slip speed Δv output by the minimum value selection unit 77 by the vehicle body speed V calculated by the vehicle speed calculator 78.
It is also possible to provide.

Road surface condition calculation unit 8 according to the second embodiment
1 is the same as the road surface state calculation device 10 of FIG. 10 except that the vehicle speed calculated by the vehicle speed calculation unit 70 is used instead of the vehicle speed detection unit 26, and thus detailed description thereof will be omitted. In addition,
The road surface condition calculation unit 81 is configured to use the vehicle speed and the slip speed like the road surface condition calculation device 10 of FIG. 11, and the vehicle speed V and the slip speed Δ calculated by the vehicle speed calculation unit 70.
You may comprise so that v and v may be input into the road surface state calculating part 81.

Next, the operation of the second embodiment will be described. The braking force P _c detected by the braking force detector 34 is
Each conversion unit 71, 72, 73, ... Of the vehicle speed calculation unit 70. ． ． Is input to each of the conversion units,
The input detection value is converted by the table, and the minute gains G _d1 , G _d2 , G _d3 ,. ． ． ． Are output respectively.

The converted minute gains G _d1 , G _d2 ,
G _d3 ,. ． ． At the same time, the minute gain G _d calculated by the minute gain calculator 36 is calculated by the difference units 74, 75, 7
6 ,. ． ． ． When input to each of the above, these differencers generate differences G _d −G _d1 , G _d −G _d2 , and G _d −.
G _d3 ,. ． ． ． Are calculated and output to the minimum value selection unit 77.

The minimum value selection unit 77 selects the difference having the smallest absolute value from the calculated differences, and specifies the conversion unit that has given the selected minimum difference value. Then, the slip speed Δv corresponding to the specified conversion unit is output.
For example, when G _d −G _d2 is the minimum value, the slip speed is output as 0.4 m / s corresponding to the conversion unit 72.

Then, the vehicle speed calculator 78 detects the slip speed Δv output by the minimum value selection unit 77 and the wheel speed sensor 65.
Is added to the wheel speed V _w detected by the vehicle speed V
Is calculated and output to the road surface state calculation unit 80. When the vehicle speed V and the braking force are input, the road surface state calculation unit 80 calculates and outputs the road surface state of the currently running road surface by the same operation as that of the first embodiment.

Further, the slip speed Δv output by the minimum value selection unit 77 and the vehicle speed V calculated by the vehicle speed calculator 78 are output to the outside of the apparatus and the divider 81 calculates Δv /
V is calculated, and the calculation result is output as the slip ratio λ.

As described above, in the second embodiment, it is not necessary to directly detect the vehicle body speed in spite of having the ∂μ / ∂Δv table in which the vehicle body speed is one of the wheel behavior amounts. The wheel speed is detected at. Accurate estimation of the vehicle body speed is difficult as compared with the wheel speed. Therefore, the detected vehicle body speed is calculated by estimating the vehicle body speed based on the Δv table and the wheel speed as in the present embodiment. It is possible to more accurately calculate the road surface state as compared with the first embodiment used.

Particularly, in the example of the vehicle speed detecting unit 26 of FIG.
Since the assumption is made that the wheel speed at the start of braking is almost equal to the vehicle speed, the road surface condition can be accurately calculated only within the range where this assumption holds, but in the present embodiment, Δv
By setting the table finely, the vehicle speed as accurate as possible can be obtained.

Further, in the present embodiment, since the accurate slip ratio is obtained by accurately estimating the vehicle speed, various applications are possible using this slip ratio.
For example, as shown in FIG. 20, a road surface state calculation device 10b
Using the road surface condition calculated by, the peak μ search unit 61 searches the peak μ _{0 on} the road surface and the slip ratio λ ₀ that gives the peak μ ₀ .

When applied to the anti-lock brake control, the braking force is controlled so that the current slip ratio λ calculated by the road surface condition calculation device 10b matches the retrieved slip ratio λ ₀ . As a result, even if the road surface condition changes, the calculated value of the slip ratio λ ₀ also changes accordingly, so that stable anti-lock brake control is always possible regardless of the road surface condition.

Further, the system of FIG. 20 is provided with a road surface μ table showing the relationship of the road surface μ with respect to the slip ratio for each road surface state, and a road surface μ table is selected according to the input road surface state, and the selected table is selected. Therefore, the road surface μ calculating unit 82 that outputs the μ value corresponding to the calculated slip ratio may be prepared.

When the road surface μ calculation unit 82 obtains the road surface μ value of the road surface on which the vehicle is currently traveling, the current frictional state is determined by comparing the road surface μ value with the peak μ ₀ value on the road surface. It is possible to estimate in which region of the road surface μ characteristic.

As a parameter representing this frictional state, for example, μ ₀ −μ can be used. When this parameter (μ ₀ −μ) has a negative value, the wheels may be locked. Therefore, by configuring a system that issues a warning to that effect to the driver, safe driving becomes possible. Note that λ ₀ −λ may be used as a parameter representing such a frictional state.

In the present embodiment, not only the road surface condition but also
Since the peak μ value and the current friction state can be known, the limit values of the wheels become clearer, and by using these parameters, by changing the control gain and setting the control target value in vehicle stabilization control, More stable control can be realized. (Third Embodiment) FIG. 13 is a block diagram showing the configuration of a road surface state calculating device according to a third embodiment of the present invention, which is a concrete example of the configuration of FIG. The same components as those in the first and second embodiments are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 13, the road surface condition calculating device 10c according to the third embodiment is adapted to detect the detected wheel speed V.
A road surface calculation unit 83 that calculates a road surface state and a vehicle speed V based on _w , a small gain G _d , and a braking force P _c , and a maximum braking force that calculates a maximum braking force on a currently running road surface based on the calculated road surface state and a vehicle speed. The selector 84 and a subtracter 89 that outputs the braking force margin ΔP _c by subtracting the detected braking force from the calculated maximum braking force.
The braking force margin ΔP _c is calculated for each wheel.

Of these, the maximum braking force selection unit 84 has conversion units 85, 86 having a maximum braking force table (see FIGS. 9A and 9B) that gives the maximum braking force for each vehicle speed for each road surface condition. Equipped with 87. These converters respectively calculate the maximum braking forces corresponding to the input vehicle speed V based on the maximum braking force table, and output the obtained maximum braking forces to the table selecting unit 88 in the subsequent stage. The table selection unit 88 selects and outputs only the maximum braking force converted by the conversion unit corresponding to the calculated road surface state.

The road surface calculation unit 83 can be constructed similarly to the road surface state calculation device 10b shown in FIG.

Next, the operation of the third embodiment will be described. In the third embodiment, the braking force allowance ΔP _c is calculated for each wheel. Therefore, for example, a large braking force or drive torque is distributed to the wheels having a high allowance so that the braking force of each wheel is made uniform. By performing such control, spin or the like can be prevented and more stable vehicle traveling can be realized.

The above is the respective embodiments of the present invention, but the present invention is not limited to the above-mentioned examples, and can be suitably changed within a range not departing from the gist of the present invention.

For example, in the embodiment, the road surface condition is classified into three types, that is, a dry road surface, a snow road surface, and an ice road surface. However, other types of road surface, such as a jagged road, a sand road surface, and a rain road surface, are used. It is also possible to calculate the road surface or to calculate more than three types of road surface states in more detail.

Further, in FIGS. 10 and 11, the vehicle speed and the braking force are converted into a minute gain by each table and the conversion value of this minute gain and the detected value are compared. It is also possible to calculate the road surface condition by converting the gain and the braking force into the braking force or the vehicle body speed by each table and comparing the converted value with the detected value of the same wheel behavior amount. The same applies to the Δv table in FIG.

Further, in the embodiment, the minute gain is used to represent the road surface μ gradient, but a braking torque gradient or the like may be used.

[0126]

As described above, according to the present invention,
The interrelationship between a plurality of wheel behavior quantities that represent road surface μ characteristics,
An excellent effect that an accurate road surface state can be calculated based on the detected values of the plurality of wheel behavior amounts and that the vehicle stabilization control can be performed more accurately based on the calculated road surface state is obtained. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration (corresponding to the first embodiment) of a road surface state computing device of the present invention.

2A and 2B are graphs showing a mutual relationship between wheel behavior amounts representing road surface μ characteristics, where FIG. 2A is a relationship between a slip ratio and a road surface μ, FIG. 2B is a relationship between a slip ratio and a braking force, and FIG. ) Indicates the relationship between the braking force for each vehicle speed and the road surface μ gradient G _d .

FIG. 3 is a block diagram showing a schematic configuration (corresponding to the second embodiment) of a road surface state computing device of the present invention.

FIG. 4 is a graph showing a relationship between a braking force P _c and a slip speed Δv for each road surface state and vehicle speed.

FIG. 5 is a graph showing a relationship between a road surface condition and a slip speed Δv for each vehicle speed and a road surface μ gradient G _d , where (a) is a dry road surface and (b) is a snow road surface.

FIG. 6 is a graph showing the relationship between the braking force P _c and the road surface μ gradient G _d when the slip speed Δv is used as a parameter for each vehicle speed, where (a) is a dry road surface and (b) is snow. It is a graph about a road surface.

7 is a graph showing the relationship between the braking force P _c and the road surface μ gradient G _d for each vehicle speed and road surface state based on FIG. 6, where (a) is vehicle speed V = 20 km / h, (b) ) Is the vehicle speed V =
40 km / h, (c) is a graph when the vehicle speed V = 60 km / h.

FIG. 8 is a block diagram showing a schematic configuration (corresponding to the third embodiment) of a road surface state computing device of the present invention.

FIG. 9 is a graph showing the maximum braking force for each vehicle speed and road surface state, where (a) is a vehicle speed V = 40 km / h and (b) is a vehicle speed V = 60 km / h graph.

FIG. 10 is a block diagram showing a configuration (first example) of a road surface state calculating device according to the first embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration (second example) of a road surface state calculating device according to the first embodiment of the present invention.

FIG. 12 is a block diagram showing a configuration of a road surface state calculating device according to a second embodiment of the present invention.

FIG. 13 is a block diagram showing a configuration of a road surface state calculating device according to a third embodiment of the present invention.

FIG. 14 is a block diagram showing a configuration of a peak μ search unit according to the embodiment of the present invention.

FIG. 15 is a block diagram showing a configuration of a minute gain calculation unit according to the embodiment of the present invention.

FIG. 16 is a diagram showing an equivalent model of a vibration system including wheels, a vehicle body, and a road surface.

FIG. 17 shows a change characteristic of a friction coefficient μ with respect to a slip speed and shows that a change in μ around a center of a minute vibration can be approximated by a straight line in order to explain that a minute gain is equivalent to a braking torque gradient. It is a figure.

FIG. 18 is a block diagram showing a hardware configuration of a brake unit.

FIG. 19 is a diagram showing a command to a control valve in the case of simultaneously performing minute excitation of brake pressure and control of average braking force.

FIG. 20 is a diagram showing an example of a system configuration when a parameter indicating a frictional state is obtained from the calculated road surface state and slip ratio in the second embodiment of the present invention.

FIG. 21 is a diagram showing a characteristic of a friction coefficient μ between a tire and a road surface with respect to a slip ratio S.

[Explanation of symbols]

10 Road surface condition calculation device 10b Road surface condition calculation device 10c Road surface condition calculation device 36 Micro gain calculator 61 Peak μ search section 70 Vehicle speed calculator 84 Maximum braking force selector

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Umeno, Nagakute-cho, Aichi-gun, Aichi-gun, Nagakage-ji, 41, Yokochi Central Research Institute Co., Ltd. (72) Eiichi Ono Nagakute-cho, Aichi-gun, Nagakute-machi 1 in Yokojimichi 41 Toyota Central Research Institute Co., Ltd. (56) Reference JP-A-4-224447 (JP, A) JP-A-7-112659 (JP, A) JP-A-8-334454 (JP, A) JP-A-7-186928 (JP, A) JP-A-62-255284 (JP, A) JP-A-1-249559 (JP, A) JP-A-8-324414 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60T 8/00 B60T 8/32-8/96 B60R 16/02 G01N 19/02

Claims (6)

(57) [Claims] 1. A road surface state calculating device comprising, for each road surface state, a mutual relationship between a plurality of wheel behavior quantities representing characteristics of a friction coefficient μ between a wheel and a road surface with respect to a slip speed. Is a gradient of the friction coefficient μ with respect to the slip speed or a physical quantity related to the gradient, and a table showing correlations among a plurality of wheel behaviors is displayed.
Is provided for each turn-up speed, and any of the plurality of wheel behavior amounts
Converted by the table for each slip speed
Of the wheel behavior for each slip speed obtained by
Based on the comparison between the converted value and the detected value of the same amount as the wheel behavior amount.
Calculate the slip speed based on the calculated slip speed
A conversion value of the wheel motion amount obtained for each road surface state by a plurality of at least any of the detection value of the wheel motion amount to convert each by correlation for each of the road surface condition that is input with, the wheel motion amount And a road surface state calculating means for calculating and outputting the road surface state based on a comparison with the detected value of the same amount. 2. A micro-excitation means for micro-exciting a braking force at a resonance frequency of a vibration system composed of a vehicle body, wheels, and a road surface, wherein the physical quantity related to the gradient of the friction coefficient μ is: 2. The ratio of the minute amplitude of the resonance frequency component of the wheel speed to the minute amplitude of the braking force when minutely exciting the braking force by the minute excitation means.
The road surface condition calculation device described. 3. A vehicle speed detecting / calculating means for detecting a vehicle speed, a wheel behavior amount detecting means for detecting a wheel behavior amount, a road surface μ gradient detecting means for detecting a road surface μ gradient, a road surface μ gradient, a vehicle speed and a wheel behavior amount. Relationship for each road surface condition
Based on the table shown, it is detected by the vehicle speed detection means.
Vehicle speed and the wheel detected by the wheel movement amount detecting means
Output the road surface μ-gradient for each road surface condition corresponding to the behavior amount
Road surface μ gradient output means, road surface μ gradient detected by the road surface μ detection means and the road surface μ gradient
Road slope μ slope for each road surface state output from μ slope output means
The road surface that selects the relevant road surface condition when the difference between
A road surface condition calculating device comprising a condition selecting means . 4. The wheel movement amount detecting means is configured to detect the wheel movement.
The braking force is detected as the dynamic amount, and the vehicle speed detecting means detects the relationship between the road surface μ gradient and the braking force.
Based on the table shown for each lip speed,
Slip speed corresponding to the braking force detected by the motion amount detecting means
Second road surface μ gradient output means for outputting the road surface μ gradient for each degree
And the road surface μ gradient detected by the road surface μ detection means and
Slip speed output from the second road μ gradient output means
The slip when the difference from the road surface μ gradient is minimum
Slip speed selecting means for selecting a speed, and the slip
Add the wheel speed to the slip speed selected by the selection means
Vehicle speed calculating means for calculating a vehicle speed by
The road surface state calculation device according to claim 3. 5. The relationship between the maximum braking force and the vehicle speed is calculated for each road surface condition.
Detected by the vehicle speed detection means based on the table shown in
The maximum braking force for each road surface condition corresponding to the specified vehicle speed is output.
Maximum braking force output means and the maximum braking force output means for each road surface condition output from the maximum braking force output means.
Selected from the large braking force by the road surface condition selection means
Maximum braking force selection to select the maximum braking force corresponding to the road condition
4. The method according to claim 3, further comprising selection means.
Is a road surface condition calculation device described in 4. 6. A position selected by the maximum braking force selecting means.
The maximum braking force of the constant wheel and the wheel movement amount detection means
The predetermined wheel based on the difference between the braking force of the predetermined wheel
The braking force allowance calculation means for calculating the braking force allowance of
The road surface condition calculating device according to claim 5, further comprising:
Place