JP3454086B2 - Wheel behavior servo control device and limit judgment device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wheel behavior amount servo controller for performing target value follow-up control of wheel behavior amounts such as wheel deceleration, slip ratio and slip speed, and a braking torque characteristic between a wheel and a road surface. The present invention relates to a limit determination device that determines a limit, and more specifically, a wheel behavior amount servo control device that enables better control based on a limit determination of a braking torque characteristic, and a braking torque characteristic based on wheel deceleration and brake torque. The present invention relates to a limit determination device that determines the limit of.

[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 that prevents and controls the braking torque close to the maximum value (torque acting on the wheels as a reaction force from the road surface).

[0003] As an example of the maximum value follow-up control of such braking torque, the Pat Hei 8-218828, techniques such as is disclosed below.

That is, in this prior art, the gradient of the braking torque with respect to the slip speed (hereinafter referred to as "braking torque gradient") is estimated based on the time-series data of the wheel speed during braking of the brake torque, and this is estimated. The lock of the wheels is prevented by controlling the braking torque gradient to follow the target value (0 when the friction coefficient μ peak follows).

FIG. 5 (a) shows a change characteristic of the braking torque with respect to the slip speed (braking torque characteristic). In the figure, the braking torque gradient at a certain slip speed is represented as the slope of the tangent line 1 at this slip speed.

As shown in FIG. 5 (a), the braking torque gradient has a positive value in the region of slip speed smaller than the slip speed S _m which gives the maximum braking torque T _m (region of A1). In the area A1, the tire is in a gripped state on the road surface.

Further, in the slip velocity region (A2 region) near the slip velocity S _m , the braking torque gradient becomes equal to or substantially equal to 0, and the maximum braking torque (peak of friction coefficient μ) is obtained. To be Therefore, it is understood that the peak μ tracking can be realized and the most efficient brake braking can be performed by feeding back the braking torque gradient and tracking it to 0 as in the prior art.

However, in general, when the brake braking is performed over the peak μ, the tire is locked by instantaneously transitioning to the area A3 where the braking torque gradient becomes negative. Therefore, it can be seen that the region A2 is the limit region of the braking torque characteristic, and the brake must be braked so as not to exceed this limit region.

[0009]

[SUMMARY OF THE INVENTION However, according to the prior art, for feeding back only the braking torque gradient, as shown in FIG. 5 (b), across the slip speed near S _m the braking torque is maximum Therefore, there is a problem that good control becomes difficult on a road surface where the braking torque gradient changes abruptly.

That is, in FIG. 5 (b), a large braking torque gradient is obtained even at a slip speed slightly smaller than the slip speed S _m , while the braking torque characteristic is saturated and the braking force is increased in the region above the slip speed S _m. If this is done, the wheel deceleration will increase sharply, making it difficult to control the brakes so that it will fall within the area A2, and in the worst case, there is a possibility of transitioning to the area A3 and locking the wheels.

The problem that the maximum tracking control of the braking torque does not function well on the road surface where the braking torque gradient changes rapidly is not only the tracking control of the braking torque gradient but also the wheel deceleration, the slip ratio, and the slip speed. This is commonly generated in the wheel behavior amount servo control device that performs target value tracking control of the wheel behavior amount such as.

The present invention has been made in view of the above facts, and a wheel behavior amount servo capable of performing excellent target value follow-up control regardless of whether or not the road surface has a rapidly changing braking torque gradient. An object of the present invention is to provide a limit determination device that enables good control of a wheel behavior amount servo control device by determining a limit of a control device and a braking torque characteristic.

[0013]

(Invention of Claim 1) In order to achieve the above object, the invention of Claim 1 is a wheel behavior amount detecting means for detecting a wheel behavior amount which is a physical quantity related to wheel motion. , Using only the wheel speed as a detection target ,
A physical quantity related via the braking torque gradient or the braking torque gradient and the wheel movement is the gradient of the braking torque with respect to the slip rate is calculated as the marginal determination amount, the braking between the wheel and the road surface based on該限boundary determination amount A limit determination means for determining the limit of the torque characteristic, and when the limit determination means determines that the braking torque characteristic is not the limit, a predetermined target value of the wheel behavior amount is calculated, and the braking torque characteristic is determined by the limit determination means. When it is determined that the limit is exceeded, target behavior amount calculation means for calculating a target value of the wheel behavior amount for promptly returning the braking torque to a range that does not exceed the limit, and the wheel detected by the wheel behavior amount detection means Servo control means for controlling the wheel movement so that the behavior amount follows the target value of the wheel behavior amount calculated by the target behavior amount calculation means. It is.

Here, the wheel behavior amount includes, for example, wheel deceleration, slip speed, slip ratio, and the like, and the present invention performs such target value tracking control of the wheel behavior amount.

According to the invention of claim 1, the limit determining means is a vehicle.
Using only wheel speed as a detection target, and calculates the physical quantity related through the gradient at which the braking torque gradient or the braking torque gradient and the wheel movement of the braking torque with respect to the slip speed as limitations determination amount. The braking torque gradient (see FIG.
The physical quantities related to (a) and (b)) via wheel motion include the physical quantity equivalent to the braking torque gradient, as well as the wheel motion equation (see (1) to (3) below). Various physical quantities associated with the torque gradient and the like are included.

The limit determination means determines the limit of the braking torque characteristic based on the calculated limit determination amount.
That is, it is determined whether or not the current motion state has reached the limit of the braking torque characteristic. Note that the braking torque characteristic means a variation characteristic of the braking torque generated between the wheel and the road surface according to the slip speed and the like, as shown in FIGS. 5A and 5B. Further, the limit of the braking torque characteristic refers to the limit of the current characteristic when the braking torque characteristic shifts to a different characteristic, for example, the limit when shifting to the state immediately before the wheel is locked (the braking torque becomes substantially the peak. Area) etc. Therefore, the saturation region where the braking torque characteristic is saturated and the control becomes unstable is also included in the range of this limit.

In such a limit region, the braking torque gradient changes before and after that, so that the braking torque gradient or the limit determination amount related thereto changes as shown in FIGS. 5 (a) and 5 (b).
It is possible to perform extremely accurate limit determination on any of the road surfaces.

Next, the target behavioral amount calculating means determines that the braking torque characteristic is not the limit by the limit determining means .
In this case, a predetermined target value of wheel behavior is calculated and
It is judged by the control means that the braking torque characteristic has exceeded the limit.
The braking torque quickly returns to a range that does not exceed the limit.
The target value of the wheel behavior amount for the calculation is calculated. In addition, the goal
The motion amount calculating means is, as in claim 7, the limit determining means.
When it is determined that the braking torque characteristic exceeds the limit by
Is the limit judgment amount and the reference value from the predetermined target value.
The target value of the wheel behavior is calculated by subtracting the value corresponding to the deviation.
You may add.

In the present invention, the calculation of the target behavioral amount calculating means may be performed as follows, for example. In the case of the limit determination result in which it is determined that the braking torque characteristic is not the limit, the normal target value of the wheel behavior amount is calculated based on the master cylinder pressure or the like. Alternatively, the control stability is emphasized, and the target value of the wheel behavior amount for matching the limit determination amount (braking torque gradient) with the reference value (0 in the case of following the braking torque maximum value) is calculated.

On the other hand, in the case of the limit determination result in which it is determined that the braking torque characteristic has exceeded the limit, it is necessary to quickly return the range to the range in which the limit is not exceeded, and therefore a calculation for changing the normal target value is performed. For example, the target value is calculated by subtracting the value corresponding to the deviation between the limit determination amount and the reference value from the normal target value. Further, the target value of the wheel behavior amount for matching the limit determination amount with the reference value in the vicinity of the limit (0 in the case of following the braking torque maximum value) may be calculated.

Then, the servo control means controls the wheel movement so that the wheel behavior amount detected by the wheel behavior amount detection means follows the target value of the wheel behavior amount calculated by the target behavior amount calculation means. For example, the braking force that acts on the wheels is controlled by controlling the pressure increase / decrease time of the wheel cylinder pressure, and thereby the wheel behavior amount is controlled to follow the target value.

As described above, in the present invention, not only the braking torque gradient is fed back as in the prior art, but the limit of the braking torque characteristic is accurately determined by the limit determination amount related to the braking torque gradient regardless of the road surface condition. When it is determined that the limit is exceeded, calculations such as changing the target value of the wheel behavior amount are performed so that the limit determination amount does not exceed the limit, so even on a road surface where the braking torque characteristic greatly changes from the limit region. Stable control is possible, and wheel locking can be reliably prevented. (Invention of claim 2 and claim 3) Further, the invention relates to a limit determination device according to claim 2, brake
Brake torque detection means for detecting torque and wheel speed
Deceleration detection means for detecting wheel deceleration based on degree
And one of the brake torque and wheel deceleration as the first physical
When the other is the second physical quantity, the first when the equilibrium state in which the slip speed is constant is assumed by the wheel motion .
And actually detected based on the relationship between the second physical quantity and
The second physical quantity corresponding to the first physical quantity is calculated as the limit determination amount, a second physical actually found a該限field determination amount
And having a and determining the limit determination means limits the braking torque characteristics between the wheel and the road surface based on a comparison of the amount.

Further, the invention of claim 3 is that of claim 2.
Limit decision device and the physical quantity related to wheel movement
Wheel movement amount detecting means for detecting the wheel movement amount, and the above-mentioned limit judgment
Depending on the limit judgment result of the device,
Wheels that should be within the range of braking torque characteristics
A target behavioral amount calculation means for calculating a target value of the behavioral amount;
The wheel behavior amount detected by the wheel behavior amount detecting means is
Target of wheel behavior amount calculated by target behavior amount calculation means
Servo control hand that controls the wheel movement to follow the value
And a step .

The determination principle of the limit determination means according to the inventions of claims 2 and 3 will be described below.

(Principle of Judgment of Claims 2 and 3)
When the braking torque acts on each wheel from the road surface, the following equation of motion is established in the motion of the wheel and the vehicle body. Although the number of wheels is four in the following description, the present invention is not limited to this number of wheels.

[0026]

[Equation 1]

However, M: vehicle mass J: wheel inertia _Rc : effective radius of wheel ω _i : wheel speed (i-th wheel, i = 1,2,3,4) ω _v : vehicle speed (corresponding to angular velocity) ω _v −ω _i : Slip speed (i-th wheel) F _i : Braking torque (i-th wheel) T _bi : Brake torque (i-th wheel) y _i : Wheel deceleration (i-th wheel). In the above equation of motion, the braking torque F _i is expressed as a function of the slip speed (ω _v −ω _i ) (actually a non-linear function). Also, · indicates the first derivative with respect to time.

Although the brake torque is used as the operation amount in the present invention, another physical amount related to the brake torque, for example, the wheel cylinder pressure may be replaced as the operation amount.

Here, the slip speed of the i-th wheel (ω _v −ω
Replacing ( _i ) with x _i and rearranging equations (1) to (3),

[0030]

[Equation 2]

It becomes By the way, the i-th detected
The target wheel deceleration is the target wheel deceleration (target deceleration)
In an equilibrium state in which the slip speed of the i-th wheel is considered to be substantially constant,

[0032]

[Equation 3]

Can be approximated by Substituting equation (6) into equations (4) and (5) and rearranging, I is the identity matrix,

[0034]

[Equation 4]

Is satisfied. However,

[0036]

[Equation 5]

It is Further, x _i0: slip speed F _i at equilibrium of the i wheel (x _i0): braking torque T at equilibrium of the i wheel _BI0: braking torque at equilibrium of the i wheel y _i0: the i This is the wheel deceleration when the wheels are in equilibrium.

FIG. 6 shows the relationship between the wheel deceleration and the brake torque in the wheel deceleration servo control. The limit point at which the braking torque is maximum in FIGS. 5A and 5B is represented as a saturation point in FIG. As shown in the figure, in the region of wheel deceleration equal to or lower than the wheel deceleration at the saturation point, there is a margin in the braking torque characteristics, so the wheel deceleration quickly approaches the target deceleration and the equilibrium state where the slip speed is constant. Becomes Therefore, the steady-state value of wheel deceleration in this region increases at a constant rate of increase with respect to the brake torque.
It can be seen that the relationship of equation (8) holds (line L).

On the other hand, in the region of the wheel deceleration exceeding the saturation point, the braking torque characteristic is saturated, so that the relationship of the equation (8) is no longer established, and the increase rate decreases as compared with the straight line L ( Straight line L '). It should be noted that in this region, even if the brake torque is increased even slightly, the wheel deceleration rapidly increases, so that stable follow-up control of the wheel deceleration becomes difficult, and it is understood that the risk of wheel locking is great.

Therefore, the limit determining means of the present invention can be obtained by assuming an equilibrium state in which the wheel speed is constant and the slip speed is constant.
The wheel deceleration y ₀ obtained by substituting the actually detected brake torque T _b0 into the equation (8) is calculated as the limit determination amount. Then, the limit (saturation point) of the braking torque characteristic is determined based on the wheel deceleration y ₀ .

For example, the steady value y ₀ of the wheel deceleration is compared with the actually detected wheel deceleration y, and this wheel deceleration y is compared.
Is larger than the steady-state value y ₀ of the wheel deceleration. In this determination, if the wheel deceleration y is larger than the steady value y ₀ , it is determined that the braking torque characteristic exceeds the saturation point because the relationship of the formula (8) is not established, and the wheel deceleration y is the steady value y. If it is not larger than _0, it is considered that the relationship of equation (8) is established and it is determined that the braking torque characteristic does not exceed the saturation point.

As described above, according to the present invention, it is possible to very accurately determine whether or not the braking torque characteristic exceeds the limit (saturation point) based on the limit determination amount.

In addition, using the wheel deceleration as described above
The method of determining whether Eq. (8) is satisfied has the excellent advantage that the response of the servo control system that makes the wheel deceleration follow the target value can be improved, but it is similar to Eq. (8). The steady value T _b0 of the brake torque obtained by substituting the actually detected wheel deceleration y ₀ into the equation (9) obtained assuming the equilibrium state where the slip speed is constant is calculated as the limit determination amount. You can also In this case, the steady-state value T _b0 of the brake torque is compared with the actually detected brake torque T _b, and the braking torque characteristic reaches the saturation point depending on whether the brake torque T _b is smaller than the steady-state value T _b0 of the brake torque. It is determined whether or not

Next, the calculation principle of the target behavioral amount calculation means according to the invention of claim 3 will be described. (Calculation Principle of Target Behavior Amount of Claim 3) At least one of the four wheels is at the limit (saturation point) by the limit determining means.
When it is determined that the value exceeds ^T , the wheel deceleration and the braking torque detected at the time of the determination are _defined as y _sat = [y _sat1 y _sat2 y _sat3 y _sat4 ] ^T T _bsat = [T _bsat1 T _bsat2 T _bsat3 T _bsat4 ]
When ^{T, the} braking torque _{F sat = [F sat1 F sat2} F sat3 F sat4] T at this time is expressed by _{F sat = -J · y sat +} T bsat (10).

Therefore, in the target behavioral amount calculating means, in order to maintain the equilibrium state in which the slip speed is constant with the braking torque F _sat , the target behavioral amount (the target deceleration in the present invention) is as follows.
Is calculated.

In order to maintain the equilibrium state in which the slip speed is constant with the braking torque F _sat , it is necessary from equation (7) to set the braking torque to T _bopt = A · F _sat (11). Furthermore, this brake torque T _bopt
By substituting the brake torque of equation (11) into the brake torque T _{0 of} equation (8), the target deceleration for realizing

[0047]

[Equation 6]

Is calculated. And the servo control means
The wheel motion is controlled so that the detected wheel deceleration follows the target deceleration y _0opt of the expression (12) calculated by the target behavioral amount calculation means. The braking torque F _sat is maintained by this target value tracking control.

The braking torque F _sat is the braking torque immediately after it is determined that the saturation point has been exceeded.
As shown in (a) and (b), in the limit region of A2 including the peak point of the braking torque, the braking torque gradient substantially matches 0, so the braking torque F _sat is regarded as a substantially peak value. Therefore, the peak μ tracking control of the braking torque is realized in the present invention, and the locking of the wheels can be reliably prevented. (Invention of Claim 4) Moreover, the invention of Claim 4 detects a brake torque.
A rake torque detecting means is further provided, and the limit determining means according to claim 1 is detected by the brake torque detecting means.
Time or series data and the wheel speed of the issued brake torque
The braking torque gradient, which is a limit determination amount, is calculated based on the time-series data of the wheel deceleration calculated from the above, and the limit of the braking torque characteristic is determined based on the limit determination amount.

The principle of calculation of the braking torque gradient according to the invention of claim 4 will be described below. (Principle of Calculation of Braking Torque Gradient of Claim 4) It is assumed that the braking torque of each wheel is a non-linear function of slip speed,
The braking torque F (x _i ) near a certain slip speed x _i is approximated by a straight line as in the following equation.

F (x _i ) = k _i x _i + μ _i (13) Here, the time series data of the slip speed is x _i [j], the time series data of the brake torque is T _b [j], and the wheel deceleration is Let y [j] be the time series data of (j = 0,1,2, ...).
However, each time series data is assumed to be sampled at every predetermined sampling time τ.

When the equations (4) and (5) are discretized for each sampling time τ and represented by the time series data,

[0053]

[Equation 7]

It becomes Here, rearranging equations (14) and (15) gives K · φ = f (16). However,

[0055]

[Equation 8]

It is Note that f is a physical quantity related to the temporal change of the braking torque, and φ is a physical quantity related to the temporal change of the slip speed.

Further, the equation (16) can be expressed as k _i · φ _i = f _i (17) for each wheel. However, f = [f ₁ f ₂ f ₃ f ₄ ] ^T , φ = [φ ₁ φ ₂
φ ₃ φ ₄ ] ^T.

Here, the limit judging means of the present invention is
Time series data y _i [j] of the wheel deceleration of the i-th wheel and the i-th wheel
The i wheels f _i on the basis of the time-series data T _bi [j] of the braking torque of the wheel, and calculates the phi _i, computed f _i, phi _i
The braking torque gradient k _i of the i-th wheel is estimated and calculated by applying, for example, an online system identification method to each data obtained by substituting in the equation (17).

Then, the limit determining means determines the limit of the braking torque characteristic based on the braking torque gradient estimated and calculated as described above, for example, as follows. That is, when the braking torque gradient is below a certain reference value, it is determined that the braking torque characteristic is the limit, and when the braking torque gradient exceeds the reference value, it is not the limit.

Since the braking torque gradient becomes smaller near the limit of the braking torque characteristic, the limit can be determined extremely accurately by the limit determining method of the present invention. (Invention of Claim 5) The invention of Claim 5 is
The limit determining means described above is characterized in that a braking torque gradient, which is a limit determining amount, is calculated based on the time-series data of the wheel speed, and the limit of the braking torque characteristic is determined based on the limit determining amount.

The principle of calculation of the braking torque gradient according to the fifth aspect of the present invention will be described below. (Principle of Calculation of Braking Torque Gradient of Claim 5) The equations of motion of the wheel and the vehicle body of the equations (1) and (2) are described as follows using the braking force F _i 'generated on the i-th wheel. To be done.

[0062]

[Equation 9]

However, v is the vehicle speed. Equation (18), (1
In equation (9), F _i 'is the slip speed (v / R _c −
is shown as a function of ω _i ).

Here, the vehicle body speed is represented by an equivalent angular velocity ω _v of the vehicle body, and the braking torque R _c F _i 'is described as a linear function of the slip velocity (slope k _i , y intercept T _i ).

[0065]       v = R_cω_v                                           (20)       R_cF_i’(Ω_v−ω_i) = K_i× (ω_v−ω_i) + T_i       (twenty one) Furthermore, by substituting equations (20) and (21) into equations (18) and (19), the wheel speed
Degree ω_iAnd vehicle speed ω _vDiscretized at every sample time τ
Time series data ω_i[k], ω_v[k] (k is sample
Sample time in units of τ, k = 1,2, .....)
We get the following expression.

[0066]

[Equation 10]

Here, if the equations (22) and (23) are combined and the equivalent angular velocity ω _{v of the} vehicle body is deleted,

[0068]

[Equation 11]

To obtain By the way, slip speed 3rad / s
Assuming that the maximum braking torque of R _c Mg / 4 (g is gravitational acceleration) is generated under the following conditions,

[0070]

[Equation 12]

To obtain Here, as a concrete constant, τ
= 0.005 (sec), R _c = 0.3 (m), and M = 1000 (kg), max (k _i ) = 245. Therefore,

[0072]

[Equation 13]

Therefore, the equation (24) can be approximated by the following equation.

[0074]

[Equation 14]

It is By organizing like this,
The equation (25) can be described in a linear form with respect to the unknown coefficients k _i and f _i. By applying the online parameter identification method to the equation (25), the braking torque gradient k _i with respect to the slip speed can be calculated. Can be estimated.

That is, by repeating the following steps 1 and 2, the time series data of the braking torque gradient can be estimated from the time series data ω _i [k] of the detected wheel speed.

Step 1:

[0078]

[Equation 15]

I will set it. Note that the first of the matrix φ _i [k] in Eq. (26) is
The element is a physical quantity related to the change of the wheel speed at one sample time, and the expression (27) is a physical quantity related to the change of the wheel speed at one sample time at the one sample time.

Step 2:

[0081]

[Equation 16]

Θ _i is calculated from the recurrence formula of ^ ^, and the first element of the matrix of θ _i is extracted as the gradient of the estimated braking torque. Here, λ is a forgetting factor (for example, λ = 0.98) indicating the degree of removing the past data, and “ ^T ” indicates the transposition of the matrix.

The left side of the equation (28) is a physical quantity representing the history of physical quantities relating to changes in wheel speed and the history of physical quantities relating to changes in wheel speed. (Invention of Claim 6) The invention of Claim 6 is
In the invention described above, a micro-excitation means for micro-exciting the brake pressure at a resonance frequency of a vibration system composed of a vehicle body, wheels, and a road surface is further included, and the limit determination means is constituted by the micro-excitation means. A minute gain, which is the ratio of the minute amplitude of the resonance frequency component of the wheel speed to the minute amplitude of the brake pressure when the brake pressure is excited slightly, is calculated as the limit determination amount, and the limit of the braking torque characteristic is calculated based on the limit determination amount. Is determined.

[0084] Oscillation of the wheel when the vehicle having a vehicle body weight W _v (the principles of the invention of claim 6) is traveling at a vehicle speed omega _v, i.e. constituted by the vehicle body and the wheel and the road surface The vibration phenomenon of the vibration system will be considered with reference to the model shown in FIG. 7, which is equivalently modeled by the wheel rotation shaft.

In the model of FIG. 7, the braking force acts on the road surface via the surface of the tread 115 of the tire that is in contact with the road surface. However, this braking force actually acts on the vehicle body as a reaction (braking force) from the road surface. Therefore, the equivalent model 117 of the vehicle body weight in terms of the rotation axis is provided to the wheel 11 via the friction element 116 (road surface μ) between the tire tread and the road surface.
It will be connected to the opposite side of 3. 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. 7, the inertia of the wheel 113 including the tire rim is J _w , the spring element 11 between the rim and the tread 115.
4, K is the spring constant, R is the wheel radius, J _{t is} the inertia of the tread 115, and the friction element 11 between the tread 115 and the road surface.
Assuming that the friction coefficient of No. 6 is μ and the inertia of the equivalent model 117 of the vehicle body weight W _v converted to the rotation axis is J _V , the transfer characteristic from the brake torque T _b 'caused by the wheel cylinder pressure to the wheel speed ω _w is From the equation of motion,

[0087]

[Equation 17]

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 ω ∞ = √ {(J _w + J _t + J _v ) K / J _w (J _t + J _v )} / 2π (30 ). This state corresponds to the area A1 before shifting to the limit area in FIGS. 5A and 5B.

On the other hand, 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. Wheel resonance system at this time can be regarded as being composed of a wheel and the road surface, its resonant frequency Omega∞ ', in equation (30), a body equivalent inertia J _v 0
It will be equal to That is, ω∞ ′ = √ {(J _w + J _t ) K / J _w J _t )} / 2π (31). This state corresponds to the limit area A2 sandwiching the peak value of the braking torque in FIGS. 5 (a) and 5 (b).

By comparing equations (30) and (31), the equivalent body inertia J
_vIs the wheel inertia J_w, Tread inertia J _tAssume greater than
Then, the resonance frequency of the wheel resonance system in the case of formula (31) ω ∞ '
Is to shift to the higher frequency side than ω∞ than Eq. (30)
become. Therefore, the change in the resonance frequency of the wheel resonance system is reflected.
Determine the limit of braking torque characteristics based on the physical quantity
It is possible to

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

First, when the minute excitation means minutely excites the brake pressure P _b with the resonance frequency ω ∞ (equation (30)) of the vibration system composed of the wheel, the vehicle body and the road surface, the wheel speed ω _w is also an average wheel. It vibrates slightly at a resonance frequency ω∞ around its speed. Here, the limit determination means of the present invention is the brake pressure P at this time.
_When the small amplitude of the resonance frequency ω ∞ of _b is P _v and the small amplitude of the resonance frequency ω ∞ of wheel speed is ω _wv , a small gain G
_{The d} is calculated as G _d = ω _wv / P _v (32). Note that this minute gain G _d is regarded as a vibration component of the resonance frequency ω ∞ of the ratio (ω _w / P _b ) of the wheel speed ω _w to the brake pressure P _b , and G _d = ((ω _w / P _b ) | It can also be expressed as s = jω∞) (33).

This small gain G_dAs shown in equation (33)
To (ω_w/ P_b) Of the resonance frequency ω ∞ of
Then, the wheel motion reached the limit region A2 of the braking torque characteristic.
Then, the resonance frequency shifts to ω∞ '
To do. Therefore, the small gain G _dMoved to the limit area A2
Reference gain G preset as a value when_sAnd minute
Gain G_dAnd a small gain G_dIs the reference gain G
_sIt is judged as the limit of the braking torque characteristic when
be able to.

Next, it will be explained that the minute gain G _d is a physical quantity equivalent to the braking torque gradient.

As shown in FIG. 8, the slip speed Δω and
It is known that the friction coefficient μ between the wheel and the road surface has a functional relationship in which the friction coefficient μ peaks at a certain slip ratio. The friction characteristic of FIG. 8 corresponds to the braking torque characteristic of FIG.

By the way, when the brake pressure is slightly excited by the minute excitation means, the wheel speed is minutely excited, and therefore, the slip ratio is also slightly vibrated around the slip ratio. Now, let us consider a change in the friction coefficient μ with respect to the slip speed Δω when a small vibration occurs around a certain slip ratio on a 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 (34). 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 equation (34) 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 (35) Here, W is the wheel load. Δ on both sides of equation (35)
Differentiating the first order with ω,

[0099]

[Equation 18]

To obtain Therefore, from the equation (36), it was shown that the braking torque gradient (dT _b / Δω) is 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, the micro gain G _d
Is represented by the following equation.

[0102]

[Formula 19]

Generally, in equation (39),       │A│ = 0.012 << │B│ = 0.1 (40) Therefore, from equations (36) and (37),

[0104]

[Equation 20]

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 .

The [0106] above, micro-gain G _d is shown to be braking torque gradient equivalent physical quantity, it is understood that the limit of the braking torque characteristics can be accurately determined based on the micro-gain G _d.

[0107]

BEST MODE FOR CARRYING OUT THE INVENTION Each embodiment of a wheel behavior amount servo control device of the present invention will be described in detail below with reference to the drawings. This wheel behavior amount servo control device is applied to a vehicle and is configured as a servo control device capable of performing maximum value tracking control of braking torque by performing target value tracking control of wheel behavior amount. . (First Embodiment) FIG. 1 is a block diagram showing a configuration in which the wheel behavior amount servo control device of the present invention is applied to a wheel deceleration servo control device.

As shown in the figure, the wheel deceleration servo control apparatus according to the first embodiment is designed so that the wheel speed (hereinafter,
"Wheel speed"), a wheel deceleration detection unit 12 that detects a wheel deceleration, a brake torque detection unit 14 that detects a brake torque acting on the wheel, and a wheel based on the detected wheel deceleration and the brake torque. Determination device 10 for determining the limit in the braking torque characteristic between the road surface and the road surface
a and a normal target value of the wheel deceleration (target deceleration) are set, and when the limit determination device 10a determines a limit point, the target deceleration for realizing the maximum tracking of the braking torque is changed. A target deceleration calculation unit 16 that performs a calculation for performing the calculation, a deviation unit 18 that calculates a deviation obtained by subtracting the detected wheel deceleration from the calculated target deceleration, and a deviation unit 1
The deceleration servo calculation unit 20 that calculates an operation amount (ABS operation amount) for making the deviation calculated by 8 match 0.
And AB for operating the control valve 23 so as to realize the ABS operation amount calculated by the deceleration servo calculation unit 20.
The S-actuator 22 and the S-actuator 22 are controlled by a control unit (not shown) at every control step of a constant cycle.

Of these, the control valve 23 of each wheel constituting the ABS actuator 22 is connected to the master cylinder 27 via the pressure increasing valve 25, and the reservoir 28 as a low pressure source via the pressure reducing valve 26.
Connected to each. A wheel cylinder 24 for each wheel is connected to the control valve 23 for applying the brake pressure supplied by the control valve to the brake disc of each wheel. The ABS actuator 22 operates to open and close the pressure increasing valve 25 and the pressure reducing valve 26 of each control valve 23 based on the ABS operation amount.

When the control valve 23 is controlled so as to open only the pressure increasing valve 25, the hydraulic pressure of the wheel cylinder 24 (wheel cylinder pressure) is proportional to the pressure obtained by the driver depressing the pedal. Up to the hydraulic pressure (master cylinder pressure). On the contrary, if the pressure reducing valve 26 is controlled to be opened, the wheel cylinder pressure is reduced to the pressure of the reservoir 28 (reservoir pressure) which is substantially atmospheric pressure. Further, when both valves are controlled to be closed, the wheel cylinder pressure is maintained.

The average braking force (corresponding to the wheel cylinder pressure) applied to the brake disc by the wheel cylinder 24 is the pressure increasing time during which the high hydraulic pressure of the master cylinder 27 is supplied, and the pressure decreasing during which the low hydraulic pressure of the reservoir 28 is supplied. Time and the ratio of the holding time for which the supplied hydraulic pressure is held,
It is obtained from the master cylinder pressure detected by the pressure sensor and the pressure value of the reservoir 28.

Therefore, the ABS actuator 22 can realize the brake torque (wheel cylinder pressure) corresponding to the ABS operation amount by controlling the pressure increasing / decreasing time of the control valve 23 according to the master cylinder pressure.

Further, the wheel deceleration detecting unit 12 outputs the wheel speed signal ω _i of the i-th wheel (i = 1,2,3,4) detected by the wheel speed sensor 30 attached to each wheel as follows. It can be realized as a filter that derives the wheel deceleration y _i of the i-th wheel by performing the processing of the formula.

[0114]

[Equation 21]

However, s is a Laplace transform operator. Note that the wheel deceleration detection unit 12 can also be configured by using a wheel deceleration sensor that directly detects the wheel deceleration regardless of the wheel speed.

The brake torque detector 14 detects the wheel cylinder pressure of each wheel and multiplies the detected wheel cylinder pressure by a predetermined constant to output the brake torque of each wheel.

Further, the deceleration servo calculation unit 20 follows the target deceleration with the ABS operation amount, that is, the wheel deceleration, such that the deviation between the calculated target deceleration and the detected wheel deceleration matches 0. It can be realized as a so-called PI controller that calculates and outputs the ABS operation amount for each wheel for performing the operation.

Next, the operation of the first embodiment will be described. First, it is assumed that the vehicle to which the wheel deceleration servo control device according to the present embodiment is applied is traveling on a road surface having a braking torque characteristic as shown in FIG.

In the limit determination device 10a, the wheel deceleration detected by the wheel deceleration detection unit 12 is a reference value (for example, 4).
When it is determined that the value exceeds 0 rad / s ² ), it is determined whether or not the following equation is satisfied for each wheel.

Y> y ₀ (43) where y is the current wheel deceleration detected by the wheel deceleration detection unit 12. Further, y ₀ is the brake torque T _b0 detected by the brake torque detection unit 14 in the above equation (8) obtained by assuming that the slip speed is constant in the equilibrium state where the wheel deceleration gradually approaches the target value. Is the wheel deceleration calculated by substituting

When the expression (43) is satisfied, that is,
When the formula (8) is not satisfied, it is determined that the braking torque characteristic is the limit because it is a region beyond the saturation point in FIG. When the expression (43) is not satisfied, that is, when the expression (8) is considered to be satisfied, it is determined that the braking torque characteristic is not the limit (does not exceed the saturation point in FIG. 6).
Then, the limit determination result for each wheel is output to the target deceleration calculation unit 16.

The change in the braking torque characteristic at the saturation point as shown in FIG. 6 is established in both the braking torque characteristics shown in FIGS. 5 (a) and 5 (b). Regardless of the situation, it is possible to accurately determine the limit of the braking torque characteristic by the equation (43).

Next, the target deceleration calculation unit 16 determines the master cylinder pressure corresponding to the driver's operation amount (brake depression amount) for the wheel determined by the limit determination device 10a that the braking torque characteristic is not saturated. A normal target deceleration corresponding to this is calculated, and the calculation result is output as the target deceleration. This target deceleration can be, for example, a wheel deceleration that is substantially proportional to the master cylinder pressure.

Then, the deceleration servo calculation unit 20 calculates the brake torque such that the deviation between the detected wheel deceleration and the target deceleration matches 0, and the ABS actuator 22 is realized so as to realize the brake torque. Control valve 2
Control the pressure increase / decrease time of 3. By this target tracking control,
The wheel deceleration is controlled so as to change according to the master cylinder pressure, which is the driver's operation amount, and the deceleration control in accordance with the driver's feeling can be performed.

On the other hand, when it is determined by the limit determination device 10a that the braking torque characteristic is saturated for at least one wheel (hereinafter referred to as the i-th wheel), the target deceleration calculation unit 16 sets the value. The target deceleration to be calculated is calculated as follows.

The braking torque of the i-th wheel actually detected at the present time when the braking torque characteristic is determined to be the limit is T _bsati , and the detected wheel deceleration of the i-th wheel is y _sati.
Then, the braking torque characteristic at this time is represented by point A in FIG. The wheel deceleration y _sati at the point A is larger than the wheel deceleration y _mi (in the dotted line portion of the straight line L) obtained by substituting the brake torque T _bsati at the point A into the equation (8), and
It can be seen that equation (43) holds.

First, the target deceleration calculation unit 16 calculates the braking torque F _sati for the i-th wheel at the point A using the formula (10) as the following formula.

F _sati = −J · y _sati + T _bsati (44) Next, the target reduction of the i-th wheel for keeping the slip speed in the equilibrium state (dx _i / dt = 0) with the calculated braking torque F _sati. Velocity y _0opti is calculated using equation (12).

[0129]

[Equation 22]

Set to. At this time, the brake torque T _bopti of the i-th wheel is T _bopti = A · F _sati (46) from the equation (11).

Here, in setting the target deceleration y _0opti , the target deceleration calculation unit 16 detects the detected brake torque T _bsati from the normal target deceleration corresponding to the master cylinder pressure at the present time, for example. T according to equation (46)
_The target deceleration may be decreased until the brake torque matches T _bopti by reducing the value corresponding to the deviation of _bopti in each control step of a constant cycle. As a result, the target deceleration y _0opti is finally set. As a result, the wheel deceleration of the i-th wheel follows y _0opti .
For other wheels that are determined not to exceed the saturation point, normal target deceleration follow-up control is performed.

Although the point A in FIG. 6 slightly exceeds the saturation point,
As shown in the braking torque characteristics of FIGS. 5 (a) and 5 (b), the braking torque is kept substantially constant even if the saturation point (the point within the area A2 in FIGS. 5 (a) and 5 (b)) is slightly exceeded. Therefore, the braking torque F _{sati of the} equation (44) at the point A can be regarded as a substantially maximum value of the braking torque. Therefore, as shown in FIG. 6, the wheel deceleration at the saturation point can be regarded as y _0opti by the equation (45), and the brake torque at the saturation point can be regarded as T _bopti by the equation (46), and the maximum braking torque of the i-th wheel can be obtained. Value tracking control is possible.

As described above, in the present embodiment, the limit of the braking torque characteristic can be accurately determined by the equation (42) regardless of the road surface condition, and when it is determined that the limit is exceeded, the maximum control of the braking torque is controlled. Since this is performed, stable control can be performed even on a road surface where the braking torque characteristic greatly changes at the saturation point, and wheel locking can be reliably prevented. (Second Embodiment) Next, the configuration of a wheel behavior amount servo control system according to a second embodiment of the present invention will be described with reference to FIG. The first of the constituent parts of the second embodiment
The same components as those in the embodiment are given the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 2, the wheel behavior amount servo control apparatus according to the second embodiment has a wheel behavior amount detection unit 32 for detecting the wheel behavior amount of each wheel and a brake torque detection unit 1.
Braking torque gradient calculation unit 41 for estimating and calculating a braking torque gradient based on the time series data of the brake torque detected by 4 and the time series data of the wheel deceleration detected by the wheel deceleration detection unit 12, and the braking torque. The determination unit 42 that determines the limit point of the braking torque characteristic based on the gradient, and the normal target value of the wheel behavior amount (target behavior amount) are calculated, and when the determination point 42 determines the limit point, the calculation is performed. The target behavioral amount calculation unit 34 that calculates the target behavioral amount that should cause the calculated braking torque gradient to follow the target value, and the ABS for matching the deviation between the calculated target behavioral amount and the detected wheel behavioral amount to 0 A behavior amount servo calculation unit 36 for calculating an operation amount, and an AB calculated by the behavior amount servo calculation unit 36
The ABS actuator 22 operates a control valve (23 in FIG. 1) so as to realize the S manipulated variable, and these are controlled at every control step of a constant cycle.

Of these, as the wheel behavior amount detected by the wheel behavior amount detecting section 32, in addition to the wheel deceleration similar to that of the first embodiment, for example, a slip ratio and a slip speed can be used. The slip ratio and the slip speed are calculated as follows.

[0136]

[Equation 23]

Where κ _{i is} the slip ratio of the i-th wheel Δω _{i is} the slip speed of the i-th wheel ω _{v is the} vehicle speed (corresponding to angular velocity) ω _i is the wheel speed of the i-th wheel.

The braking torque gradient calculating section 41 and the judging section 42 constitute a limit judging device 10b. Also,
When the wheel behavior amount detection unit 32 detects the wheel deceleration as the wheel behavior amount, the wheel behavior amount detection unit 32 and the wheel deceleration detection unit 12 are one constituent unit.

Next, the operation of the second embodiment will be described. Braking torque gradient calculator 41 according to the second embodiment
Is the time series data T _b [j] of the brake torque sampled at every predetermined sampling time τ and similarly τ.
Time series data y of wheel deceleration sampled for each
[J] (j = 0, 1, 2, ...) Is applied to the above equation (17). Then, the online system identification method is applied to each data of the equation (17) to estimate and calculate the braking torque gradient ki of the i-th wheel, and output to the determination unit 42.

Next, the determination section 42 compares the estimated braking torque gradient k _{i for} the i-th wheel with a predetermined braking torque gradient reference value (for example, 100 Nms / m) to determine the limit of the braking torque characteristic. Make a decision. For example, if the braking torque gradient k _i is equal to or greater than the braking torque gradient reference value, determines that the braking torque characteristics are not critical, if the braking torque gradient k _i is smaller than the braking torque gradient reference value, the braking torque characteristic at a limit Judge that there is.

Here, in the case of a road surface in which the braking torque gradient greatly changes when the braking torque characteristic exceeds the limit point as shown in FIG. 5 (b), the braking torque gradient k _i rapidly changes near the limit point. Since it becomes smaller and smaller than the braking torque gradient reference value, it is possible to accurately determine the limit point. Further, even in the case of a road surface having a normal braking torque characteristic as shown in FIG. 5A, the braking torque gradient becomes small near the limit point, so that the limit point can be similarly determined with high accuracy.

When it is determined that the braking torque characteristic of the i-th wheel is the limit, the target behavioral quantity computing unit 34 sets the estimated braking torque gradient k _i of the i-th wheel to the target value (0 in the case of peak following). ), The target behavior amount of the wheel behavior amount of the i-th wheel to be followed is calculated. In particular, when the braking torque gradient becomes negative, it is necessary to promptly return it to the positive region, so the set target deceleration is changed from the current value to the braking torque gradient and the braking torque gradient reference value for each control step. A relatively large value is subtracted according to the deviation of. Further, in a region where the braking torque gradient is positive, in order to emphasize stability, a target deceleration for matching the braking torque gradient with a reference value is calculated by, for example, PI control or the like.

Then, the behavior amount servo calculating section 36 sets the deviation between the calculated target behavior amount and the detected wheel behavior amount to 0.
The ABS operation amount for making it coincide with is calculated, and the control valve is operated so that the ABS actuator 22 realizes the calculated ABS operation amount. As a result, peak tracking control of the braking torque is realized.

On the other hand, when it is determined that the braking torque characteristic is not the limit, the target behavioral amount calculation unit 34 calculates a normal target behavioral amount according to the master cylinder pressure which is the driver's operation amount. As a result, the target value tracking control according to the driver's intention is realized.

As described above, in the present embodiment, the limit of the braking torque characteristic can be accurately determined regardless of the road surface condition,
In addition, when it is judged that the limit has been exceeded, the maximum tracking control of the braking torque is performed, so stable control is possible even on a road surface where the braking torque characteristics change greatly from the limit point, and it is possible to reliably prevent wheel locking. You can (Third Embodiment) Next, the configuration of a wheel behavior amount servo control system according to a third embodiment of the present invention will be described with reference to FIG. The first of the constituent parts of the third embodiment
The same components as those in the second embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 3, in the wheel behavior amount servo control system according to the third embodiment, the wheel speed sensor 3 for each wheel is used.
0 is connected to the braking torque gradient calculating unit 41 of the limit determination device 10c, and the braking torque gradient calculating unit 41 determines when the wheel speed of each wheel is detected by the wheel speed sensor 30 at every predetermined sampling time τ. The braking torque gradient is estimated based on the series data. A determination unit 42 is connected to the braking torque gradient calculation unit 41, and this determination unit determines the limit of the braking torque characteristic based on the estimated braking torque gradient. Other configurations are similar to those of the second embodiment.

Next, the operation of the third embodiment will be described. Braking torque gradient calculator 41 according to the third embodiment
Is time step data ω _i [j] (j = 0, 1, 2, ...) Of the wheel speed detected for each sampling time τ, and the steps of the above equations (26) to (28) are The time series data of the braking torque gradient k _i of the i-th wheel is estimated and calculated by repeatedly calculating 1 and step 2.

Next, the determination unit 42 compares the estimated braking torque gradient k _{i for} the i-th wheel with a predetermined braking torque gradient reference value (for example, 100 Nms / m) to determine the limit of the braking torque characteristic. Make a decision. The subsequent processing is the same as that of the second embodiment, and thus the description is omitted.

As described above, also in this embodiment, since the braking torque gradient is estimated and the limit of the braking torque characteristic is accurately determined based on the braking torque gradient, the same effect as that of the second embodiment can be obtained. You can (Fourth Embodiment) Next, the configuration of a wheel behavior amount servo control system according to a fourth embodiment of the present invention will be described with reference to FIG. The first of the constituent parts of the fourth embodiment
The same components as those in the third embodiment are designated by the same reference numerals and detailed description thereof will be omitted.

As shown in FIG. 4, the ABS actuator 22 of the wheel behavior amount servo control apparatus according to the fourth embodiment is connected to a micro-excitation command section 58 which gives a micro-excitation command of the braking force. The micro-excitation command section 58 is composed of the vehicle body, the wheels, and the road surface around the average braking force (wheel cylinder pressure) when the brake pedal is depressed and the wheel deceleration exceeds a certain reference value. Resonance frequency of vibration system ω∞ (Equation (30)) Braking force Micro amplitude P _v
A command to apply is output to the ABS actuator 22.

The minute excitation of the braking force can be performed by simultaneously performing the pressure increasing / decreasing control of the control valve 23 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. 9, each mode of pressure increase and pressure decrease is switched at every half cycle T / 2 of the cycle of minute excitation (for example, 24 [ms]) to increase or decrease pressure to the valve. directive moment between the pressure boosting t _i of the mode switching, only the respective time duration of the pressure reduction time t _r and outputs a pressure increase-pressurization command, 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.

Further, in the wheel behavior amount servo control device according to the fourth embodiment, the wheel speed minute amplitude detecting section 50 for detecting the amplitude value ω _wv of the wheel speed minute vibration generated by the minute excitation of the braking force, and brake pressure differential small-amplitude detector 52 for detecting a brake pressure differential small amplitude P _v is provided.

Of these, the wheel speed minute amplitude detection unit 50 can be realized as a calculation unit 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. The wheel speed minute amplitude detection unit 50 can be configured by providing a bandpass filter for performing the full-wave rectification and DC smoothing of the filter output. Also, an integral multiple of the cycle, for example, 24 [m of one cycle
[s], two cycles of 48 [ms] time-series data are continuously captured, and the correlation with the unit sine wave and unit cosine wave of 41.7 [Hz] can be obtained.

Further, the brake pressure minute amplitude P _v is determined by the master cylinder pressure, the length of the valve pressure increasing time t _i shown in FIG. 9 and the pressure reducing time t _{r in} a predetermined relationship. pressure differential small amplitude detector 52 may be a master cylinder pressure, the pressure increasing time t _i and the pressure reducing time t _r constituting a table for outputting the brake pressure differential small amplitude P _v.

Furthermore, the limit determination device 10d according to the fourth embodiment calculates the minute gain G _d based on the detected wheel speed minute amplitude ω _wv and the brake pressure minute amplitude P _v. Section 54 and calculated small gain G
_The determination unit 56 determines the limit of the braking torque characteristic by comparing _d with the reference gain G _s . Of these, the minute gain calculator 54 can be configured as a divider that calculates the equation (32).

The target behavioral quantity computing unit 3 of the present embodiment
5 calculates a target value (target behavior amount) of the wheel behavior amount that should cause the minute gain G _d to follow the target value, according to the limit determination result of the determination unit 56.

Next, the operation of the fourth embodiment will be described. When small gain G _d by fine gain calculation unit 54 is calculated, the determination unit 56 makes a determination limit of the braking torque characteristics by comparison with the micro-gain G _d and the reference gain G _s. For example, when the minute gain G _d is larger than the reference gain G _s , it is determined that the braking torque characteristic is not the limit, and when the minute gain G _d is the reference gain G _s or less, it is determined that the braking torque characteristic is the limit. .

Here, in the case of a road surface in which the braking torque gradient greatly changes when the braking torque characteristic exceeds the limit point as shown in FIG. 5 (b), the minute gain G _d rapidly decreases near the limit point. Since the gain is smaller than the reference gain G _s , the limit point can be accurately determined. Also,
Even in the case of a road surface having a normal braking torque characteristic as shown in FIG. 5A, the minute gain G _d becomes small near the limit point, so that the limit point can be similarly determined with high accuracy.

When it is determined that the braking torque characteristic of the i-th wheel is the limit, the target behavioral amount calculating section 34 sets the estimated minute gain G _d of the i-th wheel to the target value (0 in the case of peak following). The target behavior amount of the wheel behavior amount of the i-th wheel that should be followed is calculated. For example, the set target deceleration is adjusted from the current value for each control step to the minute gain G _d and the reference gain G _s.
A relatively large value is subtracted according to the deviation from.

Then, the behavioral quantity servo computing unit 36 sets the deviation between the calculated target behavioral quantity and the detected wheel behavioral quantity to 0.
The ABS operation amount for making it coincide with is calculated, and the control valve is operated so that the ABS actuator 22 realizes the calculated ABS operation amount. As a result, peak tracking control of the braking torque is realized.

On the other hand, when it is determined that the braking torque characteristic is not the limit, the target behavioral amount calculation unit 34 calculates a normal target behavioral amount according to the master cylinder pressure which is the driver's operation amount. As a result, the target value tracking control according to the driver's intention is realized.

As described above, in this embodiment, the limit of the braking torque characteristic can be accurately determined regardless of the road surface condition,
In addition, when it is judged that the limit has been exceeded, the maximum control of the braking torque is controlled, so stable control is possible even on a road surface where the braking torque characteristics change significantly from the limit point, and wheel locking can be reliably prevented. You can

In particular, in the fourth embodiment, since the minute gain G _d that sharply decreases in the limit region of the braking torque characteristic is used, the limit of the braking torque characteristic can be determined with extremely high accuracy.

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 thereof.

For example, in the first embodiment, (43)
The determination of the saturation point using the formula may be performed by the following formula.

T _b <T _b0 (49) where T _b is the current brake torque detected by the brake torque detector 14 of FIG. Also,
T _b0 is the wheel deceleration y ₀ detected by the wheel deceleration detection unit 12 in the above equation (9) obtained by assuming that the slip speed is constant in the equilibrium state where the wheel deceleration gradually approaches the target value. Is the brake torque calculated by substituting

Further, in the fourth embodiment, the minute excitation means of the brake pressure is realized by adjusting the pressure increasing / decreasing time to the control valve, but the present invention is not limited to this, and it is not limited to this. It is also possible to use a means for directly applying a brake pressure to the brake disc by means of a piezoelectric actuator that expands and contracts according to an excitation command.

[0168]

[Examples] Examples of operating the first and second embodiments under specific conditions will be described below. (First Embodiment) A simulation result in the case where the wheel deceleration servo control device according to the first embodiment performs the target deceleration follow-up control by suddenly braking on a low μ road will be described with reference to FIG.

FIG. 10A shows the temporal changes in the wheel speed (solid line) and the vehicle speed (broken line). As shown in the figure, the wheel speed does not match the vehicle speed from the brake braking start time (1 s). However, except immediately after the brake braking start time, the difference between the wheel speed and the vehicle body speed (slip speed) is kept constant until the wheel speed matches 0, and the wheel deceleration asymptotically matches the target deceleration. It can be seen that an equilibrium state with a constant slip speed has been realized.

Further, FIG. 10B shows a temporal change between the detected wheel deceleration (solid line) and the calculated target deceleration (broken line). As shown in the figure, in the time zone from the brake braking start time (1 s) to around time 1.4 s, there is a slight difference between the wheel deceleration and the target deceleration, but the difference is small. Further, since the wheel deceleration tends to follow the target deceleration, it can be said that the wheel deceleration substantially matches the target deceleration. Then, after the time of 1.4 s, the target deceleration and the wheel deceleration are almost completely in agreement with each other, and it can be seen that the target follow-up control functions well during the sudden braking.

Further, FIG. 10 (c) shows the detected brake torque T _b (solid line) and the brake torque T _b0 (broken line) calculated by the equation (8) using the detected wheel deceleration. Is shown over time. As shown in the figure, during the period from braking start time (1s) to near time 1.6s, T _b is smaller than T _b0. Since this is the same value as the expression (43) is satisfied (the same as the expression (49)), the limit determination device 10a in FIG. 1 determines that the braking torque characteristic is saturated in this time zone. Here, the target deceleration calculating section 16 reduces T _b0 every control step until T _b substantially coincides in T _b0, from the T _b0
The target deceleration y ₀ is calculated based on the equation (8).

Even when the braking torque characteristic is saturated in this way, as described with reference to FIG. 10B, the wheel deceleration substantially matches the target deceleration, so the braking torque characteristic does not exceed the limit. It can be seen that the target value tracking control is functioning well. Furthermore, in FIG.
After 6 s, T _b substantially matches T _b0 .
It has been shown that the peak μ tracking control at the saturation point of is functioning well without causing wheel lock.

Next, a simulation result in the case where the wheel deceleration servo control device according to the first embodiment performs the target deceleration follow-up control by suddenly braking on the high μ road will be described with reference to FIG.

As shown in FIGS. 11A to 11C, high μ
It can be seen that the target value follow-up control functions well on the road as in the case of the low μ road in FIG. Since it is a high μ road, the time until the wheels stop is short, and as shown in FIG. 11C, the time zone (1 s-
1.5 s) is also shorter than that in FIG.

From the above simulation results, according to the wheel deceleration servo control apparatus according to the first embodiment of the present invention, wheel lock occurs regardless of whether the road is a low μ road or a high μ road. It was shown that stable target value tracking can be realized without any problems. (Second Embodiment) A simulation result in the case where the wheel deceleration servo control device according to the second embodiment performs the target deceleration follow-up control by suddenly braking on a low μ road will be described with reference to FIG.

FIG. 12A shows the temporal changes in the wheel speed (solid line) and the vehicle speed (broken line). As shown in the figure, the wheel speed does not match the vehicle body speed from the brake braking start time (1 s), but the difference between the wheel speed and the vehicle body speed (slip speed) becomes a slight difference until the vehicle stops. Which indicates that no wheel lock has occurred.

Further, FIG. 12B shows a temporal change between the detected wheel deceleration (solid line) and the calculated target deceleration (broken line). As shown in the same figure, in the time zone from the brake braking start time (1 s) to the time 1.2 s, there is a slight deviation between the wheel deceleration and the target deceleration, but the difference is small. Further, since the wheel deceleration tends to follow the target deceleration, it can be said that the wheel deceleration substantially matches the target deceleration. Then, after the time 1.2 s, the target deceleration of the wheel deceleration almost completely coincides with the target deceleration, and it is understood that the target follow-up control functions well during the sudden braking.

Further, FIG. 12 (c) shows the change over time of the calculated braking torque gradient. As shown in the figure, the braking torque gradient sharply decreases from the braking start time (1 s), and thereafter maintains a value equal to or less than a certain value until the vehicle stops. That is, it is shown that a small value near the peak μ is held, and the target value tracking control functions well without causing wheel lock.

Next, a simulation result in the case where the wheel deceleration servo control device according to the second embodiment performs the target deceleration follow-up control by suddenly braking on the high μ road will be described with reference to FIG.

As shown in FIGS. 13 (a) to 13 (c), high μ
It can be seen that also on the road, similar to the case of the low μ road in FIG. 12, the result that the target value tracking control functions well is obtained.

From the above simulation results, according to the wheel deceleration servo control apparatus according to the second embodiment of the present invention, stable target value tracking can be realized without causing wheel lock regardless of the condition of the road surface. It has been shown.

[0182]

As described above, according to the first and fourth to seventh aspects of the present invention, the braking torque gradient, which is the gradient of the braking torque with respect to the slip speed, or the braking torque gradient and the wheel movement are represented. a physical quantity related via calculated as marginal determination amount in accordance with the limit determination result of the braking torque characteristics based on該限boundary determination amount, a predetermined target wheel motion amount when the braking torque characteristic is determined not to be a limit The value is calculated, and when it is determined that the braking torque characteristic exceeds the limit, the target value of the wheel behavior amount for quickly returning the braking torque to the range not exceeding the limit is calculated.
Compared with the case of performing target value tracking control by feeding back two physical quantities, it is possible to perform better target value tracking control regardless of whether or not the road surface has a sudden change in the braking torque gradient. The effect is obtained. Also,
According to the inventions of claims 2 and 3, when one of the brake torque and the wheel deceleration is the first physical quantity and the other is the second physical quantity, the equilibrium state in which the slip speed is constant is achieved by the wheel motion. Based on the assumed relationship between the first and second physical quantities, the second physical quantity corresponding to the actually detected first physical quantity was calculated as the limit determination quantity. The excellent effect of being able to determine

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a wheel deceleration servo control device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a wheel behavior amount servo control device according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a wheel behavior amount servo control device according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a wheel behavior amount servo control device according to a fourth embodiment of the present invention.

FIG. 5 is a diagram for showing a change characteristic (braking torque characteristic) of a braking torque with respect to a slip speed, and FIG. 5A is a braking torque characteristic of a road surface where a braking torque gradient changes gently before and after a peak μ; b) shows the braking torque characteristic of the road surface where the braking torque gradient changes abruptly before and after the peak μ.

FIG. 6 is a diagram showing a relationship between wheel deceleration and brake torque when the wheel deceleration servo control is configured.

FIG. 7 is a diagram showing an equivalent model of a vibration system including wheels, a vehicle body, and a road surface.

FIG. 8 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. 9 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. 10 is a simulation result when the wheel deceleration servo control device according to the first embodiment of the present invention is subjected to sudden braking on a low μ road.

FIG. 11 is a simulation result when the wheel deceleration servo control device according to the first embodiment of the present invention is subjected to sudden braking on a high μ road.

FIG. 12 is a simulation result when the wheel behavior amount servo control device according to the second embodiment of the present invention is brake-braked on a low μ road.

FIG. 13 is a simulation result when the wheel behavior dual servo control device according to the second embodiment of the present invention is subjected to sudden braking on a high μ road.

[Explanation of symbols]

10a Limit determination device 10b limit determination device 10c limit determination device 10d limit determination device 12 Wheel deceleration detector 14 Brake torque detector 16 Target deceleration calculator 18 Deviation calculator 20 Deceleration servo calculation unit 22 ABS actuator 23 Control valve 30 wheel speed sensor 32 Wheel behavior amount detector 40 Braking torque gradient calculator 42 Judgment unit 34 Target behavior amount calculation unit 36 Behavior servo calculation unit 50 Wheel speed minute amplitude detector 52 Brake pressure micro amplitude detector 54 Micro gain calculator 58 Micro excitation command section

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Yamaguchi Inventor Hiroyuki Nagakute, Aichi-gun, Aichi Nagalete 1 1 at 41 Yokomichi Toyota Central Research Institute Co., Ltd. (72) Ken Sugai, Aichi-gun Nagakute-cho, Aichi 1 Yokomichi 41 Toyota Central Research Institute Co., Ltd. (56) Reference JP-A-8-318842 (JP, A) JP-A-62-85751 (JP, A) JP-A-8-183439 (JP, A) Special Kaihei 8-239024 (JP, A) JP 8-324414 (JP, A) JP 9-52572 (JP, A) JP 4-224447 (JP, A) JP 3-189338 ( JP, A) JP-A-6-213801 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60T 8/00, 8/32-8/96

Claims (7)

(57) [Claims] 1. A wheel behavior amount detecting means for detecting a wheel behavior amount, which is a physical amount related to wheel motion, and a braking torque gradient, which is a gradient of a braking torque with respect to a slip speed, using only a wheel speed as a detection target. a physical quantity related via the braking torque gradient and the wheel motion is calculated as the marginal determination amount, and limits determining means for determining the limit of the braking torque characteristics between the wheel and the road surface based on該限boundary determination amount, the limit When it is determined by the determination means that the braking torque characteristic is not the limit, a predetermined target value of the wheel behavior amount is calculated,
When it is determined by the limit determination means that the braking torque characteristic exceeds the limit, target behavior amount calculation means for calculating a target value of the wheel behavior amount for quickly returning the braking torque to a range not exceeding the limit, the wheel Servo control means for controlling the wheel movement so that the wheel behavior amount detected by the behavior amount detecting means follows the target value of the wheel behavior amount calculated by the target behavior amount calculating means; apparatus. 2. A brake torque detecting brake torque.
And a wheel deceleration detector that detects the wheel deceleration based on the wheel speed.
Output means and one of the brake torque and wheel deceleration as the first physical quantity
However, when the other one is the second physical quantity , the first and
The first detected actually based on the relationship of the second physical quantity.
Of the braking torque characteristic between the wheel and the road surface is determined based on a comparison between the second physical quantity corresponding to the physical quantity of the vehicle and the second physical quantity actually detected. A limit determination device comprising : 3. The limit determination device according to claim 2 , and a wheel behavior amount which is a physical amount related to wheel motion is detected.
Depending on the wheel behavior amount detection means and the limit determination result of the limit determination device, the limit determination is performed.
Keep a fixed amount within the range that does not exceed the limit of the braking torque characteristics
Target behavioral amount calculator for calculating the target value of the desired wheel behavioral amount
And the wheel behavior amount detected by the wheel behavior amount detecting means.
Of the wheel behavior amount calculated by the target behavior amount calculation means
Servo control that controls wheel movement to follow the target value
Wheel motion amount servo control apparatus characterized by having a control means. 4. A brake torque detecting brake torque.
The brake torque detection means.
Time-series data of the detected brake torque and the vehicle
A braking torque gradient, which is a limit determination amount, is calculated based on time-series data of wheel deceleration calculated from the wheel speed, and the limit of the braking torque characteristic is determined based on the limit determination amount. 1. Wheel behavior amount servo control device described in 1.
Place 5. The limit determination means calculates a braking torque gradient, which is a limit determination amount, based on time-series data of wheel speeds, and determines a limit of the braking torque characteristic based on the limit determination amount. The wheel behavior amount servo control device according to claim 1. 6. A micro-excitation means for micro-exciting the brake pressure at a resonance frequency of a vibration system composed of a vehicle body, wheels and a road surface, wherein the limit determining means applies the brake pressure by the micro-excitation means. A minute gain, which is the ratio of the minute amplitude of the resonance frequency component of the wheel speed to the minute amplitude of the brake pressure when excited slightly, is calculated as the limit determination amount, and the limit of the braking torque characteristic is determined based on the limit determination amount. The wheel behavior amount servo control device according to claim 1, wherein 7. The target behavioral amount calculation means is configured to detect the limit judgment.
It is judged by the control means that the braking torque characteristic has exceeded the limit.
, The limit judgment amount and the reference from the predetermined target value.
The target value of wheel behavior is reduced by subtracting the value corresponding to the deviation from the value.
A wheel behavior according to claim 1, wherein a value is calculated.
Quantity servo controller.