JP3535347B2 - Apparatus and method for estimating road friction coefficient - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on an automobile for use. The present invention relates to an apparatus for estimating a friction coefficient (μ) of a road surface on which an automobile is traveling at present in real time by a calculation of a program control circuit by inputting behavior of wheels. INDUSTRIAL APPLICABILITY The present invention is used for calculation and estimation of a friction coefficient of a road surface given as an input parameter to an automatic braking control device, a posture stabilization control device and the like. The present invention relates to a friction coefficient of a road surface by associating a rotational acceleration when the drive wheel spins with an actual acceleration state of the vehicle when slip occurs on the drive wheel when accelerating the vehicle with an engine drive force. μ) is estimated (at the time of driving). The present invention also relates to at least one of the wheels when applying brake pressure in order to decelerate the vehicle by braking.
When S operates, the friction coefficient (μ) of the road surface is estimated by associating the rotational acceleration (negative value) of the wheel with the acceleration (negative value) of the vehicle (during braking).

[0002]

2. Description of the Related Art In an automatic braking control system for a vehicle, when a slip occurs on a part of the wheel, the braking pressure applied to the wheel is automatically and intermittently controlled to impair the steerability of the vehicle. Control not to. Vehicle attitude stabilization control devices, for example, increase or decrease the braking pressure of some vehicles so that the vehicle does not skid, spin, or drift out when an operation input such as steering is applied. Control is performed to stabilize the vehicle body and prevent rollover.

In these devices, the outputs of various sensors (steering angle, vehicle speed, yaw rate, sideslip angle, etc.) mounted on the vehicle are used as inputs, and real-time arithmetic control is performed by a program control circuit. In controlling these calculations,
It is important to estimate the friction coefficient of the road on which the vehicle is currently traveling. On the other hand, it is not easy to correctly estimate the friction coefficient of the road surface on which the vehicle is currently traveling. Therefore, conventionally, it is known that a driver operates a switch to set the friction coefficient of a road surface on which the vehicle is currently traveling to three levels of "slip-resistant", "slippery", and "extremely slippery".

Conventionally, the following is a device for estimating the friction coefficient (μ) of the road surface in real time by taking in the outputs of the sensors mounted in the vehicle and also in the vehicle and performing the calculation by the program control circuit. There is something like this. (A) Japanese Patent Application Laid-Open No. 6-286630 (Applicant: Nissan Motor Co., Ltd.) discloses a steering angle, a vehicle speed, which are obtained as sensor outputs,
Yaw rate, sideslip angle, etc. are the friction coefficient of road surface (μ)
A method of estimating a road surface friction coefficient (μ) by using a neural network by utilizing the influence of the above is disclosed. (B) Japanese Patent Application Laid-Open No. 7-174689 (Applicant: Nippon Denso Co., Ltd.) uses the property that the turning center of a vehicle moves to the front wheel side as the friction coefficient (μ) of the road surface decreases, and A method of estimating the friction coefficient (μ) of the road surface from the magnitude relation of the rotation speed is disclosed. (C) JP-A-6-3257 (Applicant: Honda Motor Co., Ltd.)
Is the magnitude of the slip that occurs on the driving wheel when the engine driving force is applied to the driving wheel.
The coefficient of friction of the road surface (μ)
A method of estimating is disclosed.

[0005]

What is disclosed in the above (A) is to perform a repetitive operation using a neural network. The accuracy of the estimated friction coefficient (μ) is increased with the lapse of a long time, but the road surface condition that changes rapidly depending on the running condition is not estimated with appropriate accuracy in a short time.

Although the method disclosed in (B) above is an excellent method in principle, it is necessary to detect a small difference in the rotation angles of a plurality of wheels, and to what extent can it be practically implemented. Is still unknown.

The method disclosed in (C) above is an excellent method that matches the driver's feeling as to whether or not the road surface is slippery. It cannot be applied as it is to vehicles with four wheels or more, which are connected by differential gears.

As described above, the value of the road surface friction coefficient (μ) given to the input of the posture stabilization control device or the braking control device does not require so much accuracy, for example, in about three stages, that is, "slip resistant" and "slip". If it can be divided into “easy” and “very slippery”, it is effective in most cases. Rather, it is more important to calculate the road surface friction coefficient (μ) in real time in a very short time.

The present invention has been made against such a background, and has a sufficient degree of accuracy as the value of the road surface friction coefficient (μ) given as an input parameter of the posture stabilization control device and the braking control device. It is an object of the present invention to provide a road surface friction coefficient (μ) estimating device that can be applied to a four-wheel vehicle or a vehicle having more than four wheels and can be calculated in real time.

[0010]

DISCLOSURE OF THE INVENTION The present invention relates to a method in which a vehicle is braked by associating the idling rotational speed of the drive wheels generated when the vehicle is accelerated by an engine driving force with the actual acceleration state of the vehicle. Apply braking pressure to slow down by operation ABS on at least one of the wheels
When the (automatic braking control device) operates, the road surface friction coefficient (μ) is estimated by associating the rotational acceleration (negative value) of the wheel with the acceleration (negative value) of the vehicle. .

[0011] That is, a first aspect of the present invention is the estimation of the road surface friction coefficient when the vehicle acceleration, the detected rotation speed of the rotating speed you and the driven wheels of the left and right drive wheels during acceleration a (.omega.f) respectively means for recording, and means for calculating a rotational speed difference component of the left and right drive wheels, and means for Starring <br/> calculate the time differential value of the difference, the time acceleration by the engine driving force is performed And a means for obtaining a time (ts) at which the time differential value shows the maximum value (a) in the time section of interest, and a rotational acceleration ((t-Δt)) of the driven wheel at a time (ts-Δt) slightly before this time (ts). means for computing dωf / dt),
Means for estimating the value of the road surface friction coefficient (μ) corresponding to the magnitude of the maximum value (a) with respect to the rotational acceleration (dωf / dt) of the driven wheel.

Rotational acceleration of the driven wheel (dωf / dt)
Means for estimating the value of the road surface friction coefficient (μ) corresponding to the magnitude of the maximum value (a) corresponds to the stepwise divided value of the road surface friction coefficient (μ) according to the characteristics of the vehicle. Then, a map stored in advance about the magnitude of the maximum value (a) with respect to the rotational acceleration (dωf / dt) of the driven wheel and the rotational acceleration (dωf / dt) of the driven wheel and the maximum value are referred to with reference to this map. It is desirable to include means for obtaining the road surface friction coefficient (μ) from the magnitude of the value (a).

When the vehicle is accelerated by the engine driving force,
Slip occurs on the drive wheels when the road surface is slippery. The driven wheel does not slip. Rotational speed of the rotating speed you and the driven wheels of the right and left drive wheels from the wheel speed sensor provided in each drive wheel and the driven wheels (.omega.f) and acquisition record, the difference component of the rotational speed occurring in the left and right drive wheels determined First, the time differential value of this rotational speed difference is calculated. This value indicates the rotational acceleration at the time of acceleration for the rotational speed difference between the left and right drive wheels, that is, the rising speed of idling.

On the other hand, the maximum value (a) among the time differential values
Is a time (t) that indicates where is detected in the time section of interest within the time during which the acceleration by the engine driving force is being performed.
s), and the time (ts-Δ) slightly before this time (ts) from the detected and recorded rotational speed (ωf) of the driven wheel.
t), that is, the rotational acceleration (dωf / dt) of the driven wheels immediately before the idling of the driving wheels is calculated. This value indicates the acceleration of the vehicle body caused by the acceleration operation. Corresponding to the magnitude of the maximum value (a) of the time derivative of the rotational speed difference between the left and right drive wheels with respect to the rotational acceleration (dωf / dt) of the driven wheels (the rising speed of the drive wheel idling), the road surface friction coefficient (μ ) Value is estimated.

The value of the road surface friction coefficient (μ) is a value obtained by stepwise dividing the road surface friction coefficient (μ) according to the characteristics peculiar to the vehicle, for example, the road surface friction coefficient (μ) is up to 0.1. The rotational acceleration of the driven wheel (corresponding to a value (very slippery), a value from 0.1 to 0.4 (slippery), and a value from 0.4 to 0.8 (slippery) ( The magnitude of the maximum value (a) with respect to dωf / dt) is stored in advance as a map, and with reference to this map, the rotational acceleration (dωf / dt) of the driven wheel and the magnitude of the maximum value (a) are calculated. You can ask.

A second aspect of the present invention is the estimation of the road surface friction coefficient during braking, which is the wheel rotation speed (ω) during braking.
(p, ωq) is detected and recorded for a plurality of wheels, and ABS (Antilock Break Sys
tem, automatic braking control device), means for calculating the time differential value (dωq / dt) of the rotational speed (ωq) for the wheel (Q) on which the ABS is not activated (P) Of the rotational speed (ωq) of the wheel (Q) operated by the ABS with respect to the time differential value (dωp / dt, which is proportional to the acceleration of the vehicle body) of the rotational speed (ωp, which is proportional to the vehicle body speed (V)) of and a means for estimating the value of the road surface friction coefficient (μ) corresponding to the negative amplitude value (a ′, maximum acceleration value during deceleration) of dωq / dt).

The time differential value (dωq / of the rotational speed (ωq) of the wheel (Q) where the ABS is operated with respect to the time differential value (dωp / dt) of the rotational speed (ωp) of the wheel (P) where the ABS is not operated. dt) negative amplitude value (a ')
The means for estimating the value of road surface friction coefficient (μ) corresponding to
The time differential value (dωp / d) of the rotational speed (ωp) of the wheel (P) in which the ABS does not operate corresponding to the value of the road surface friction coefficient (μ) divided stepwise according to the characteristics of the vehicle.
The map stored in advance for the magnitude of the negative side amplitude value (a ′) of the time differential value (dωq / dt) of the rotational speed (ωq) of the wheel (Q) where the ABS is operated with respect to t), and this map Referring to the time differential value (dωp) of the rotational speed (ωp) of the wheel (P) in which the ABS does not operate.
/ Dt) and the negative side amplitude value (a '), it is desirable to include means for obtaining the road surface friction coefficient (μ).

When the vehicle is braked, the wheel rotation speeds (ωp, ωq) are captured and recorded from the wheel rotation speed sensors provided on each of the plurality of wheels, and the ABS actuated in response to the braking operation input. The time differential value (dωq / dt) of the rotational speed (ωq) of (Q) is calculated, and the rotational speed (ω) of the wheel (P) in which the ABS does not operate is calculated.
The time differential value (dωp / dt) of p) is calculated. ABS
The rotational speed (ωp) of the wheel (P) that does not operate is proportional to the vehicle body speed (V), and its time derivative (dωp / dt) is proportional to the vehicle body acceleration.

A with respect to the time differential value (dωp / dt) of the rotational speed (ωp) of the wheel (P) in which the ABS does not operate
The road surface friction coefficient (μ) is estimated corresponding to the negative side amplitude value (a ′) of the time differential value (dωq / dt) of the rotational speed (ωq) of the wheel (Q) where the BS has operated. The rotation speed (ωp) of the wheel (P) where the ABS does not operate is proportional to the vehicle body speed (V), and its time differential value (dωp / dt) is proportional to the vehicle body acceleration. Further, the negative side amplitude value a ′ of the time differential value (dωq / dt) of the rotational speed of the wheel (Q) in which the ABS has operated represents the maximum acceleration value during deceleration.

Also when estimating the road surface friction coefficient (μ) at the time of braking, according to the characteristics peculiar to the vehicle, as described above, the ABS corresponds to the stepwise divided value of the road surface friction coefficient (μ). Does not work The rotation speed of the wheel (P) (ω
p) with respect to the time differential value (dωp / dt) of the rotational speed (ωq) of the wheel (Q) on which the ABS is operated.
The magnitude of the negative side amplitude value (a ′) of ωq / dt) is stored in advance as a map, and the time differential value (ωp) of the rotation speed (ωp) of the wheel (P) in which the ABS does not operate is stored with reference to this map. It can be obtained from dωp / dt) and the negative amplitude value (a ′).

Thus, as the value of the road surface friction coefficient (μ) given as an input parameter of the posture stabilization control device or the braking control device, there is a sufficient degree of accuracy, that is, "difficult to slip", "slippery", "very slippery". In a precision classification such as “easy”, a value applicable to a four-wheel vehicle or a vehicle having more wheels can be calculated and estimated in real time, and highly accurate posture stabilization control and braking control can be performed.

[0022]

DETAILED DESCRIPTION OF THE INVENTION

[0023]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing a system configuration of a posture stabilization control device according to an embodiment of the present invention, and FIG. 2 is a perspective view showing an example of mounting the posture stabilization control device according to the embodiment of the present invention on a vehicle.

The road surface friction coefficient estimating apparatus 1 according to the embodiment of the present invention is
An ABS (automatic braking control device) 2 is provided and is provided in a posture stabilization control device 3 that performs automatic braking control and also performs posture stabilization control of a vehicle by inputting various control information.

[0025] The road surface friction coefficient estimating device 1, as means for estimating a road surface friction coefficient (mu) at the time of acceleration, the rotational speed of the rotating speed you and the driven wheels of the left and right drive wheels during acceleration a (.omega.f) respectively means for detecting and recording, the means for calculating the rotational speed difference component of the left and right drive wheels, and means for calculating a time differential value of the difference, the time of interest in time of acceleration by the engine driving force is performed Means for obtaining a time (ts) at which the time differential value shows the maximum value (a) in the section;
Means for calculating the rotational acceleration (dωf / dt) of the driven wheel at a time (ts-Δt) slightly before this time (ts) and the maximum value (a) for the rotational acceleration (dωf / dt) of the driven wheel. ), And means for estimating the value of the road surface friction coefficient (μ) corresponding to the magnitude of

The means for estimating the value of the road surface friction coefficient (μ) corresponding to the magnitude of the maximum value (a) with respect to the rotational acceleration (dωf / dt) of the driven wheel includes road surface friction according to the characteristics of the vehicle. Refer to this map 4 and the map 4 stored in advance for the magnitude of the maximum value (a) with respect to the rotational acceleration (dωf / dt) of the driven wheel corresponding to the stepwise divided values of the coefficient (μ). And means for obtaining the road surface friction coefficient (μ) from the rotational acceleration (dωf / dt) of the driven wheel and the magnitude of the maximum value (a).

Further, as a means for estimating the road surface friction coefficient during braking, the wheel rotational speeds during braking (ωp, ω)
q) for a plurality of wheels for detection and recording, and a time differential value (ωq) of the rotational speed (ωq) for the wheel (Q) on which the ABS (Antilock Break System, automatic braking control device) 2 has operated in response to the braking operation input. dωq / dt) and a rotation speed (ωp, proportional to the vehicle body speed (V) of the wheel (P) where the ABS2 does not operate when the ABS2 operates.
The rotational speed (ω) of the wheel (Q) on which the ABS 2 is operated with respect to the time differential value (dωp / dt, which is proportional to the acceleration of the vehicle body) of
and a means for estimating the value of the road surface friction coefficient (μ) corresponding to the negative side amplitude value (a ′, maximum acceleration value during deceleration) of the time differential value (dωq / dt) of q).

AB with respect to the time differential value (dωp / dt) of the rotational speed (ωp) of the wheel (P) in which the ABS 2 does not operate
The means for estimating the value of the road surface friction coefficient (μ) corresponding to the negative side amplitude value (a ′) of the time differential value (dωq / dt) of the rotational speed (ωq) of the wheel (Q) in which S2 has operated is , The time differential value (dωp / d) of the rotational speed (ωp) of the wheel (P) in which the ABS 2 does not operate corresponding to the value of the road surface friction coefficient (μ) divided stepwise according to the characteristics of the vehicle.
Map 4 stored in advance with respect to the magnitude of the negative side amplitude value (a ′) of the time differential value (dωq / dt) of the rotational speed (ωq) of the wheel (Q) at which the ABS 2 has operated with respect to t), and this map 4 Referring to, the time differential value (dωp) of the rotation speed (ωp) of the wheel (P) in which the ABS 2 does not operate
/ Dt) and the amplitude value (a ') on the negative side, a means for obtaining the road surface friction coefficient (μ) is included.

The configuration of this embodiment has been described by taking the two-axis structure vehicle shown in FIG. 1 as an example, but in the case of a large vehicle, a three-axis or four-axis structure is used. The same can be applied to such a three-axis or four-axis structure. That is, the rotational speed of each wheel and other necessary control information are taken in, the road surface friction coefficient (μ) is similarly estimated, and the estimated road surface friction coefficient (μ) is used as control information for automatic braking control,
Posture stabilization control and other controls are similarly performed.

Next, the operation of estimating the road surface friction coefficient of the road surface friction coefficient estimating apparatus 1 of the embodiment of the present invention thus constructed will be described. FIG. 3 is a flow chart showing the flow of the road surface friction coefficient estimating operation during acceleration by the road surface friction coefficient estimating apparatus of the present invention, and FIG. 4 shows the method of estimating the road surface friction coefficient during acceleration by the road surface friction coefficient estimating apparatus of the present embodiment. It is a figure explaining.

When the vehicle is accelerated, the road friction coefficient estimating apparatus 1 rotates the wheels 6 of the left and right driving wheels (left and right rear wheels) and the driven wheels as shown in FIG. 4 (A). From the speed sensor 5 to the rotational speed (ωrl) of the left driving wheel,
The rotation speed (ωrr) of the right drive wheel and the rotation speed (ωf) of the driven wheel are taken and the values are continuously recorded as time passes.

[0032] Next, the recording of a certain time, calculates the rotational speed difference component of the left and right driving wheels, and calculates a time differential value of the rotational speed difference. This is continuously repeated as time passes. Further, in the time section of interest within the time during which the engine driving force is accelerating, the time (t) indicating the maximum value (a) of the time differential value calculated above is displayed.
s), and as shown in FIG.
The rotational acceleration (dωf / dt) of the driven wheel at a time (ts-Δt) slightly before s) is calculated.

Here, the map 4 shown in FIG. 4 (c), that is, the value of the road surface friction coefficient (μ) divided stepwise according to the peculiar characteristics of the vehicle, for example, the road surface is extremely slippery. Corresponding to values up to μ = 0.1, values up to μ = 0.4 where the road surface is considered slippery, and values up to μ = 0.8 where the road surface is considered slippery. Rotational acceleration (dωf / dt) and maximum value (a)
According to the relationship (rotational acceleration of the driven wheels is increased with
Then, the road surface friction coefficient (μ) is obtained from the rotational acceleration (dωf / dt: vehicle body acceleration) of the driven wheel and the maximum value (a) by referring to the map 4 representing the relationship that the maximum value becomes smaller. .

This road surface friction coefficient (μ) is output to the posture stabilization control device 3, and the posture stabilization control and the automatic braking control by the ABS 2 are performed using this value as control information.

Next, the operation of estimating the road surface friction coefficient during braking will be described. FIG. 5 is a flowchart showing the flow of the road surface friction coefficient estimating operation during braking by the road surface friction coefficient estimating apparatus of the present invention, and FIG. 6 shows the road surface friction coefficient estimating method during braking by the road surface friction coefficient estimating apparatus of the present embodiment. It is a figure explaining.

The road surface friction coefficient estimation device 1 uses the wheel rotation speed sensors 5 of the respective wheels 6 of the driving wheels (left and right rear wheels) and the driven wheels (left and right front wheels) to rotate the wheels when the vehicle is braked. Take the velocity (ωp, ωq) and record the value.

Next, as shown in FIG. 6 (A), the time differential value (dωq / dt) of the rotational speed (ωq) of the wheel (Q) on which the ABS 2 is operated in response to the braking operation input is calculated, and at the same time, When the ABS 2 operates, the time differential value (dωp / dt) of the rotation speed (ωp) of the wheel (P) where the ABS 2 does not operate is calculated. The lower the road friction coefficient (μ), the faster the wheel rotation speed decelerates.

Then, as shown in FIG.
When ABS2 is activated, ABS2 is not activated (P)
Time differential value (dωp / dt) of the rotation speed (ωp) of A and A
BS2 seeks <br/> the rotational speed of the wheel (Q) which operated negative amplitude value of the time differential value of (ωq) (dωq / dt) (a '). The larger the negative amplitude value (a ′), the lower the road friction coefficient (μ). Rotational speed (ωp)
Of the time differential value (dωp / dt) of the vehicle body is proportional to the acceleration (deceleration) of the vehicle body, and the negative side amplitude value (a ′) of the time differential value (dωq / dt) of the rotational speed (ωq) of the wheel (Q). ) Indicates the maximum acceleration value during deceleration.

A with respect to the time differential value dωp / dt of the rotational speed (ωp) of the wheel (P) in which the ABS 2 does not operate
A map 4 shown in FIG. 6 (c) in which the magnitude of the negative-side amplitude value (a ') of the time differential value (dωq / dt) of the rotational speed (ωq) of the wheel (Q) on which the BS2 is operated is stored in advance, That is, referring to the map 4 showing the values of the road surface friction coefficient (μ) divided in stages according to the characteristics peculiar to the vehicle, for example, the values divided in three stages similar to the estimation during acceleration, the ABS 2 operates. The road surface friction coefficient is obtained from the time differential value (dωp / dt) of the rotational speed (ωp) of the wheel (P) and the negative side amplitude (a ′).

Now, with reference to FIG. 1, the posture stabilization control device 3 according to the embodiment of the present invention will be described. The posture stabilization control device 3 is an electronic device including a computer circuit that is program-controlled, and receives a driving operation input of a vehicle and behavior data of the vehicle as input, and outputs a motion state of the vehicle, and outputs a driving operation according to this output. It performs stable control of the posture that gives a corrective input that corrects the input and disturbance input to the safe side. That is, it includes a numerical model that holds the physical characteristics of the vehicle as a numerical value, and an observer that takes in the driving operation input of the vehicle as data and refers to the numerical model to estimate the response of the vehicle by a transfer function. The data given to the function is an autoregressive method (AR method) in which the data X (k) at the time point k is represented by a value obtained by multiplying the past data up to the time point before the time point M by the weighting coefficient A (m) at each time point. Calculate the response by.

For example, when the loaded weight is changed, the loaded load is changed, the number of passengers is changed, the seating position of the passengers is changed, etc., the parameters for displaying the characteristics of the vehicle are the actual parameters. Inconsistent with behavior. At this time, the parameters held in advance in the numerical model of the vehicle are automatically changed to match their behavior. This update is executed when the vehicle is safely traveling with the behavior of the vehicle with respect to the driving operation input or the disturbance input being sufficiently smaller than the dangerous degree.

A yaw rate sensor 7, a roll rate sensor 8, a lateral acceleration sensor 9 and a longitudinal acceleration sensor 10 are mounted on this apparatus, and their respective detection outputs are connected to the posture stabilization control apparatus 3. Wheel rotation speed sensors 5 are attached to the four wheels 6, respectively, and their detection outputs are also connected to the posture stabilization control device 3. A brake pressure sensor 12 is attached to the brake booster actuator 11, and its detection output is also connected to the posture stabilization control device 3. A steering angle sensor 14 is attached to the steering wheel 13, and its output is connected to the posture stabilization control device 3. A governor sensor 16 is incorporated in the governor 15 for controlling the internal combustion engine, detects the state of the governor 15, and outputs the detection output thereof to the posture stabilization control device 3.

An example of the control flow of the posture stabilization control device 3 is as shown in FIG. 7 for normal control. The acquisition of this behavior data is executed by the autoregressive method (AR method). That is, it goes backward to the data up to the point M in the past,
It is represented by a value obtained by multiplying the past data by the weighting factor A (m) at each time point.

When the state of the cargo changes, or the number of passengers or the positions of passengers changes, the control illustrated in FIG. 8 is performed and the parameters of the vehicle model are updated. This update is automatically performed by constantly monitoring the need for correction. The acquisition of this behavior data is also executed by the autoregressive method (AR method). The update mode process shown in FIG. 8 is executed in step S9 shown in FIG.

FIG. 9 shows an example of input data according to the embodiment of the present invention, in which steering angle is shown in (a), yaw rate is shown in (b), and side slip angle is shown in (c). The horizontal axis is time (seconds). The horizontal axis is (a), (b), (c)
Is common to. When the steering wheel 13 is operated, the steering angle sensor 14 detects it and sends the input data shown in (a) to the posture stabilization control device 3. Along with this steering operation, the yaw rate sensor 7 detects the yaw rate and sends the input data shown in (b) to the posture stabilization control device 3. At the same time, the lateral acceleration sensor 9 detects the side slip angle and sends the input data shown in (c) to the posture stabilization control device 3. That is, (a) shown in FIG. 9 is an input, and (b) and (c) are responses representing the behavior (behavior) of the vehicle.

The attitude stabilization control device 3 calculates the transfer function of this vehicle based on these data. The transfer function is a complex function, and as a practical example, it can be displayed by displaying frequency on the horizontal axis and amplitude and phase on the vertical axis. Considering with a relatively simple model, the amplitude characteristic will be a gentle downward-sloping curve with respect to frequency,
The phase characteristic has a corresponding downward sloping curve. Figure 10
(A) And (b) is a figure which illustrates the frequency characteristic of an amplitude and a phase about a yaw rate. 11 (a) and 11 (b) are diagrams illustrating the frequency characteristics of the amplitude and the phase with respect to the sideslip angle. These are diagrams showing transfer functions calculated based on actual data.

Now, the attitude control and updating of the vehicle will be described. When the transfer function is determined in this way, the dynamic characteristics of the vehicle are calculated using this transfer function, and when an abnormal motion exceeding a preset standard is predicted,
Attitude control is performed such that different brake pressures are applied to the wheels to suppress abnormal movement of the vehicle. Since this is the same as the method that has been put to practical use in passenger cars, a detailed description thereof will be omitted here. This technology is applied to commercial vehicles (trucks and buses). In commercial vehicles, the transfer function itself, which represents the vehicle's response, fluctuates depending on the loading situation and the number of passengers, so the transfer function is updated. .

FIG. 10 is a diagram for explaining this, and it is assumed that a function having a characteristic indicated by a broken line is already accumulated as a transfer function in the numerical model. This is a model in the case where the load is in a standard form of about one third of the maximum load.
Suppose that a new additional load is loaded in response to this. Then, the total weight and the position of the center of gravity change. This naturally results in different vehicle responses to the same steering. That is, the transfer function already stored must be changed. Therefore, when the transfer function is calculated again according to the behavior of the vehicle appearing in the sensor, a characteristic different from the already accumulated transfer function appears as shown by the solid line. This calculation is automatically executed as described in FIG. When the difference, that is, the area shaded in FIG. 10 is larger than the preset limit value,
As shown by the solid line, the accumulated model itself is updated to a new calculated value indicating the current state. This is done automatically as described in FIG. By updating such a numerical model of the automatically accumulated transfer functions, it becomes possible to execute proper attitude control even when the load changes or when the crew changes. .

[0049]

As described above, according to the present invention, the road surface friction coefficient (μ) given as an input parameter of the posture stabilization control device and the braking control device applicable to a four-wheel vehicle or a vehicle having more than four wheels is provided. ) Can be calculated in real time in a very short time with a degree of accuracy that can be used.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of a posture stability control device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an example of mounting an attitude stabilization control device according to an embodiment of the present invention on a vehicle.

FIG. 3 is a flowchart showing a flow of a road surface friction coefficient estimating operation at the time of acceleration by the road surface friction coefficient estimating apparatus of the embodiment of the present invention.

FIG. 4 is a diagram illustrating a method of estimating a road surface friction coefficient at the time of acceleration by the road surface friction coefficient estimating apparatus according to the embodiment of the present invention.

FIG. 5 is a flowchart showing a flow of a road surface friction coefficient estimating operation during braking by the road surface friction coefficient estimating apparatus according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating a method of estimating a road surface friction coefficient during braking by the road surface friction coefficient estimation device according to the embodiment of the present invention.

FIG. 7 is a flowchart illustrating normal control by the posture stabilization control device according to the embodiment of the present invention.

FIG. 8 is a flowchart for explaining parameter updating of the vehicle model by the posture stabilization control device according to the embodiment of the present invention.

9A, 9B, and 9C are diagrams showing input data of a steering angle, a yaw rate, and a sideslip angle in the control of the attitude stabilization control apparatus according to the embodiment of the present invention.

10A and 10B are diagrams showing an example of a transfer function represented by a gain and a phase in the control of the attitude stabilization control apparatus according to the embodiment of the present invention.

11A and 11B are diagrams showing another example of a transfer function represented by a gain and a position in the control of the attitude stabilization control apparatus according to the embodiment of the present invention.

[Explanation of symbols]

1 Road surface friction coefficient estimation device 2 ABS (Automatic braking control device) 3 Posture stability control device 4 maps 5 Wheel rotation speed sensor 6 wheels 7 Yaw rate sensor 8 Roll rate sensor 9 Lateral acceleration sensor 10 Front-back acceleration sensor 11 Brake booster actuator 12 Brake pressure sensor 13 steering wheel 14 Steering angle sensor 15 Governor 16 governor sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoaki Miyazaki 3-1-1 Hinodai, Hino-shi, Tokyo Inside Hino Motor Co., Ltd. (56) Reference JP-A-4-55156 (JP, A) JP 7-159308 (JP, A) JP 6-3257 (JP, A) JP 7-323753 (JP, A) JP 64-44369 (JP, A) JP 6-286630 (JP , A) JP 7-267067 (JP, A) JP 5-170087 (JP, A) JP 7-174689 (JP, A) JP 3-159862 (JP, A) JP 3-26089 (JP, A) JP-A-7-172278 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60T 8/58 B62D 6/00 G01N 19/02

Claims (4)

(57) [Claims] 1. A means for detecting and recording the rotational speeds of the left and right driving wheels and a rotational speed (ωf) of the driven wheels at the time of acceleration, a means for calculating a rotational speed difference between the left and right driving wheels, and a time of the difference. A means for calculating a differential value, a means for obtaining a time (ts) at which the time differential value shows the maximum value (a) in a time section of interest within a time period during which the engine driving force is being accelerated, ts), a means for calculating the rotational acceleration (dωf / dt) of the driven wheel at a time (ts-Δt) slightly before ts), and as the value of the road surface friction coefficient (μ) increases,
The maximum value for the rotational acceleration (dωf / dt) of the driven wheel
Based on the relationship that the size of the large value (a) becomes smaller
Of the value of the rotational acceleration of the driven wheel and the maximum value (a)
A road surface friction coefficient estimating device comprising means for estimating a value of a road surface friction coefficient (μ) from the size . 2. The rotational acceleration (dωf / d) of the driven wheel
The means for estimating the value of the road surface friction coefficient (μ) from the value of t) and the maximum value (a) is a stepwise divided value of the road surface friction coefficient (μ) according to the characteristics of the vehicle. The rotational acceleration (dω) of the driven wheel corresponding to
f / dt) and a map showing the relationship between the magnitude of the maximum value (a), and referring to this map, the rotational acceleration (dωf / dt) of the driven wheel and the maximum value (a) The road surface friction coefficient estimating device according to claim 1, further comprising means for obtaining a road surface friction coefficient (μ) from the magnitude of 3. A means for detecting and recording wheel rotational speeds (ωp, ωq) during braking for a plurality of wheels, and ABS (Antilock Break System, for the braking operation input).
The automatic braking control device) operates means for calculating a time differential value (dωq / dt) of the rotational speed (ωq) for the wheel (Q) and the ABS increases as the road friction coefficient (μ) increases. Wheels where ABS does not work when activated
At the rotation speed of (P) (ωp, proportional to vehicle speed (V))
To the differential value (dωp / dt, proportional to the vehicle body acceleration)
The rotation speed (ωq) of the wheel (Q) on which the ABS is operated
-Side amplitude value of the time derivative (dωq / dt) of
(A ', the maximum value of acceleration during deceleration) becomes smaller
On the basis of the relationship, the ABS of the wheel (P) not operating
Time derivative of rotation speed and wheel on which the ABS is operated
(Q) with the negative side amplitude value of the time differential value of the rotation speed
And a means for estimating the value of the road surface friction coefficient (μ) from the value . Negative amplitude value of the time differential value of the rotational speed of the time differential value and said wheel ABS is actuated in rotational speed (ωp) (Q) of 4. A wheel the ABS does not operate (P) and
The means for estimating the value of the road surface friction coefficient (μ) from the value of the wheel is a wheel whose ABS does not operate corresponding to the stepwise divided value of the road surface friction coefficient (μ) according to the characteristics of the vehicle.
(P) rotational speed (ωp) time derivative (dωp / d
t) and the rotation speed (ω) of the wheel (Q) on which the ABS is operated.
q) a time differential value (dωq / dt) of the negative side amplitude value (a ′), and a map showing the relationship between the ABS and the wheel (P) rotation speed at which the ABS does not operate.
Degree (ωp) time derivative (dωp / dt) and the ABS
Differential value of the rotational speed (ωq) of the wheel (Q) that operated
Road friction coefficient estimating apparatus according to claim 3, further comprising a means for obtaining a road surface friction coefficient (mu) and a.