JPH11180274A - Attitude control device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy in attitude control by estimating the slip ratio between a wheel and a road surface in a traveling direction of a vehicle by an arithmetic means to obtain the force in a longitudinal direction and that in a lateral direction to be applied to each wheel. SOLUTION: An attitude control device 1 takes the outputs of a yaw rate sensor 6 and a steering angle sensor 14 when the breaking operation is detected by a brake pressure sensor 12, and determines the wheel speed V' on the basis of the wheel rotating speed sensor 10 of the front and rear wheels 8, 9. Then it takes the detecting output Gx from a longitudinal acceleration sensor 18 to calculate the slip ratio sf in a tire force arithmetic part 2. The actual vehicle speed V is calculated by using the obtained value. Simultaneously, the slip ratio of each wheel is calculated on the basis of the actual speed V and the rotating speed of each wheel to be used as the longitudinal force Fx. Further each angle of side slip βf, βr of the front and rear wheels are determined on the basis of the actual speed V, the acceleration Gy in a lateral direction, the yaw rate ω, the steering angle δ or the like, and the force Fy in the lateral direction is determined on the basis of the braking force or the driving force acting on each wheel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used by being mounted on an automobile. The present invention relates to an apparatus for automatically detecting the attitude of a vehicle and calculating and controlling the attitude of the vehicle so as to prevent the skid when the skid is occurring or when the skid is likely to occur. Use as The present invention takes in a value that can be measured by a running car and performs a calculation in real time, so that a driving force or a braking force applied to the wheel so that no slip occurs on the wheel or the slip state of the wheel is controlled. To a device that automatically controls

[0002]

2. Description of the Related Art When a large driving force is applied to a driving wheel on a slippery road surface, the driving wheel slips. At this time, the vehicle may spin in the lateral direction. The same applies to the case of braking. When a large braking force is applied to the wheels on a slippery road surface, the wheels are in a slip state and braking cannot be performed.
Further, on a slippery road surface, steering may cause the vehicle to skid. The loss of the steering stability of the vehicle is often caused by the slipping of the driving wheels, the slipping of the braking wheels, or the sudden steering. Therefore, when driving, to prevent the driving wheels from slipping,
It is desirable that a driving force equal to or less than the slip limit is applied, and a braking force equal to or less than the slip limit is applied so as to prevent the braked wheels from slipping during braking, and control is performed so as not to steer sharply.

Conventionally, an electronic control device for a brake and a vehicle stability control device (VSC, Vehicle Stability Control) have been proposed.
Etc. are known. ABS (Antilock Brake System) is a typical system for electronic control devices related to brakes.
). This is to provide a rotation sensor on the wheel to detect the wheel rotation, and if the wheel rotation stops when the brake pressure is large, the brake pressure is intermittently controlled assuming that there is a slip between the wheel and the road surface. . ABS has become widespread in passenger cars and freight cars, and has become widely known as a device that can handle while braking. As a typical device of the vehicle stabilization control device (VSC), a skid prevention device is known. this is,
From the steering angle (the steering wheel angle) input by the driver, the course that the driver is going to read is read, and if the vehicle speed is too high for that course, the driver will automatically decelerate without having to press the brake pedal. This is a device that performs control such as distributing the left and right brake pressures so as not to deviate from the course.

[0004] A known vehicle attitude stabilizing device (VSC) (JP-A-63-279976, JP-A-2-112755, etc.) will be further described. When this is done, the direction of the vehicle changes and the vehicle rolls. At this time, when the tire of the turning inner wheel due to steering reaches the grip limit of the road surface, the inner wheel tends to be a so-called wheel lift, and the vehicle starts to skid. For example, when the driver steers to the left from a straight running state, the vehicle leans to the right. At this time, the vehicle turns in accordance with the steering in a normal state, but if the steering speed is too high relative to the traveling speed, the vehicle leans to the right and the left wheel is in a floating state, so that the driver Will move to the right from the intended direction. Such a behavior of the vehicle causes a deviation from the traveling lane or, in an extreme case, a rollover of the vehicle.

In a normal running state, the magnitude and speed of steering, the speed of the vehicle, the speed of lateral movement of the vehicle, and the speed of change in the direction of the vehicle (yaw rate, rotation of the vehicle around a vertical axis at the center of gravity of the vehicle) Acceleration) is detected and calculated to predict the start point of the skid of the wheel or the start point of the wheel lift of the inner wheel, and a device for controlling the brake pressure of the wheel before the start of the skid or the wheel lift has been developed. The brake pressure control of the wheels does not necessarily apply the same brake pressure to all the wheels, but applies a large or small brake pressure to one wheel to prevent the vehicle from skidding. Such an apparatus has been well studied not only for its basic structure and design, but also for its economy and durability, and has reached the stage of being mounted on a commercial product for a passenger car.

[0006]

Such a conventional apparatus calculates a yaw rate from parameters relating to the current driving operation including steering and braking and parameters relating to the current behavior of the vehicle, that is, from the current parameters. The brake pressure of the vehicle is automatically controlled when it is determined that the yaw rate has a possibility of skidding which is set and stored in advance for the vehicle. The possibility of this side slip is determined by executing a calculation in real time from the vehicle operation data, which is a driving operation input and various sensor outputs.

For example, when a driver steers to the right while driving through a gentle right curve at a high speed, the vehicle starts to skid, deviates from the lane intended by the driver, and enters the left lane. Assume that a condition has occurred. The driver operates the brakes to apply braking force to the wheels, but at the same time, the attitude control device does not distribute the braking force evenly to each wheel, but automatically increases the braking force of the right wheel. To control. As a result, a force acts on the vehicle so as to be pulled back to the right.

The above description has been made on the assumption that the driver performs the brake operation.
When a sensor provided on the vehicle detects that the vehicle is likely to start skidding, the attitude control device automatically detects this and stabilizes the attitude for some wheels. The braking force is automatically applied in the direction of movement.

However, when there is a slip between the wheel and the road surface in the traveling direction of the vehicle, the change in the direction of the vehicle with respect to the magnitude of the steering becomes small, and the force causing the vehicle to skid is correspondingly weak. Become.

The present invention has been made in view of such a background, and an object of the present invention is to provide a device capable of performing highly accurate vehicle attitude control. An object of the present invention is to provide a device for performing vehicle stabilization control capable of applying a braking force or a driving force so as to predict and calculate a wheel slip limit and control a wheel slip state. . An object of the present invention is to provide an automatic control device that stabilizes a running state of a vehicle. SUMMARY OF THE INVENTION An object of the present invention is to provide a stabilization control device that prevents a dangerous state that may lead to a rollover of a vehicle.

[0011]

SUMMARY OF THE INVENTION The present invention automatically detects a posture of a vehicle when the vehicle is running, and when a side slip occurs,
Alternatively, when there is a possibility of occurrence of sideslip, the attitude of the vehicle is controlled so as to prevent the sideslip by estimating and considering the slip of the wheels.

That is, the present invention includes the mass M of the vehicle, the distance Lf from the center of gravity of the vehicle to the front wheel axle, the distance Lr from the center of gravity of the vehicle to the rear axle, and the moment of inertia I around the center of gravity of the vehicle. Means for storing a constant as a vehicle model, and acceleration G in the longitudinal and lateral directions of the vehicle
x, Gy, vehicle speed V 'obtained from wheel rotation speed
Means for measuring the yaw rate ω of the vehicle as an electric signal, means for calculating the behavior of the vehicle from the vehicle model and the electric signal, and individually and automatically applying to each wheel based on the calculation results of the calculating means. Means for controlling a braking force or a driving force to be applied, wherein the calculating means estimates a slip ratio between a wheel and a road surface in a traveling direction of the vehicle, and calculates a slip ratio under the slip ratio. And a wheel force calculating means for calculating front and rear and lateral forces Fx and Fy applied to each wheel of the vehicle.

The relationship between the longitudinal acceleration Gx of the vehicle and the slip ratio s of the wheel measuring the vehicle speed V 'is known, and the wheel force calculating means calculates the longitudinal acceleration Gx from the measured longitudinal acceleration Gx. The slip rate s of the wheel is obtained, and the vehicle speed V ′ is corrected using the slip rate s to obtain the true vehicle speed V. The slip rate of each wheel is obtained from the true vehicle speed V and the rotation speed of each wheel. It is desirable to include a means for calculating and calculating the front-back force Fx applied to each wheel.

The wheel force calculating means further calculates a true vehicle speed V, a lateral acceleration Gy of the vehicle, a yaw rate ω of the vehicle,
From the respective distances Lf, Lr from the center of gravity of the vehicle to the front wheel axis and the rear wheel axis, and the steering angles δ, the respective sideslip angles βf, βr of the front wheels and the rear wheels are obtained.
It is desirable to include means for determining a lateral force actually acting on each wheel from f and βr and a braking force or a driving force actually acting on each wheel.

The relationship between the longitudinal acceleration Gx of the vehicle and the slip ratio s (hereinafter referred to as "wheel characteristics") differs depending on the coefficient of friction between the wheels and the road surface. Therefore, it is preferable that the wheel characteristics in each case be recorded in advance for a plurality of friction coefficients, and one of the wheel characteristics is selected and used according to the road surface condition. In practice,
It is sufficient to record the wheel characteristics for the three high, medium and low friction coefficients.

In order to determine the actual road surface condition, refer to
The technique disclosed in JP-A-135923 can be used. In other words, based on the braking force or the driving force applied to the wheels, when the wheels slip on the road surface, the state of the road surface is automatically detected in real time. Further, a method and apparatus for estimating a road surface friction coefficient in real time, which the present inventors have further improved and applied for a patent separately from the present application, can be used. This technique is described below.

The lateral acceleration Gy generated in the running vehicle is expressed by the following formula: Gy = V ((dβ / dt) + ω) V: vehicle speed β: vehicle slip angle dβ / dt: time differential value of the slip angle β ω: Since the yaw rate has changed, the lateral acceleration Gy and the vehicle speed V are obtained from the lateral acceleration sensor, the vehicle speed sensor, and the yaw rate sensor.
And the yaw rate ω are taken as an electric signal, a time differential value dβ / dt = (Gy / V) −ω of the vehicle slip angle β is obtained from the equation, and the time differential value dβ / dt of the vehicle slip angle β is integrated over time. To calculate the sideslip angle β. At this stage, the vehicle speed V 'actually obtained from the rotation speed of the wheels is used as the vehicle speed V. From the obtained sideslip angle β and the distance Lf from the center of gravity of the vehicle to the front wheel axis, the sideslip angle βf of the front wheels is determined as βf = β + (Lf / V) ω−δ (δ: front wheel steering angle).

On the other hand, assuming that the lateral force generated on the front wheels is Ff and the lateral force Fr generated on the rear wheels, I (dω / dt) = 2Ff · Lf−2Fr · Lr in the rotational direction about the center of gravity of the vehicle. Since there is a relationship of M · Gy = 2Ff + 2Fr in the lateral direction, the lateral force Ff of the front wheel is calculated from these formulas and the stored numerical value by the formula Ff = (I (dω / dt) + M · Gy · Lr) / 2 (L
f + Lr).

From βf and Ff thus obtained,
The road surface friction coefficient μ of the front wheels of the vehicle is determined by the following equation, where Kf is the constant of the cornering power determined from the tire specifications. Note that the above-described method of estimating the friction coefficient is a desirable example, and the present invention can be similarly implemented by other methods.

As described above, according to the present invention, even when there is a slip between the wheels and the road surface in the traveling direction of the vehicle, it is possible to accurately estimate the force causing the vehicle to skid,
Attitude stabilization control can be performed with high accuracy.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

[0022]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a system configuration of the apparatus of the embodiment of the present invention, and FIG. 2 is a perspective view showing an example of mounting the apparatus of the embodiment of the present invention on a vehicle.

The attitude control device 1 according to the embodiment of the present invention includes a vehicle mass M, a distance Lf from the center of gravity of the vehicle to the front wheel axle, a distance Lr from the center of gravity of the vehicle to the rear wheel axle, and a distance around the center of gravity of the vehicle. Means for storing a constant including a moment of inertia I as a vehicle model, and a longitudinal acceleration sensor 1
8. The output from the lateral acceleration sensor 4, the vehicle speed sensor 5, and the yaw rate sensor 6 is taken in, and the vehicle speed V 'and the vehicle yaw rate (the vehicle speed V' obtained from the longitudinal and lateral accelerations Gx and Gy of the vehicle, the wheel rotational speed) are obtained. ω) as an electrical signal, a means for calculating the behavior of the vehicle from the vehicle model and the electrical signal, and a braking force or drive individually and automatically applied to each wheel based on the calculation result of the calculating means. Means for controlling the force. Further, as a feature of the present invention, the calculating means estimates a slip ratio between a wheel and a road surface in a traveling direction of the vehicle, and applies longitudinal and lateral directions applied to each wheel of the vehicle under the slip ratio. Wheel force calculation means for obtaining the directional forces Fx and Fy is included.

A tire force calculating unit 2 is provided as wheel force calculating means. The tire force calculating unit 2 includes a vehicle longitudinal acceleration Gx and a vehicle speed V '.
The relationship with the slip ratio s of the wheel measuring the wheel speed is known, and the wheel force calculating means calculates the slip ratio s of the wheel from the measured longitudinal acceleration Gx, and uses the slip ratio s The vehicle speed V ′ is corrected to obtain the true vehicle speed V, and the slip ratio of each wheel is calculated from the true vehicle speed V and the rotation speed of each wheel, and the longitudinal force Fx applied to each wheel is calculated. Means to be determined, true vehicle speed V, lateral acceleration Gy of the vehicle, yaw rate ω of the vehicle, and respective distances Lf, L from the center of gravity of the vehicle to the front wheel axis and the rear wheel axis.
r, and the steering angles δ, the respective sideslip angles βf, βr of the front wheels and the rear wheels are determined. From these sideslip angles βf, βr and the braking force or the driving force actually acting on the wheels, the actual values for the respective wheels are calculated. Means for determining a lateral force acting on the

Further, the attitude control device 1 according to the embodiment of the present invention is provided with a wheel rotation speed sensor 10 and a brake booster actuator 11 provided on the front wheel 8 and the rear wheel 9 as a part of the control output device. An ABS (automatic braking control device) 3 that takes in the detection output of the brake pressure sensor 12 and intermittently controls the brake pressure when a slip occurs.

The attitude control device 1 includes, as other control information required for the attitude stabilization control, a steering angle sensor 14 for detecting a steering angle of a steering wheel 13, a governor sensor 16 provided in an electronic governor 15, and a vehicle. The output of the roll rate sensor 17 for detecting the roll rate is connected. Further, control signals are sent from the attitude control device 1 to the brake booster actuator 11 and the electronic governor 15.

In this embodiment, as shown in FIG. 1, the structure of a vehicle having a two-shaft structure is described as an example. However, in the case of a large vehicle, a three-shaft or four-shaft structure is used. The present invention can take in required control information even in a three-axis or four-axis structure, similarly estimate a slip ratio s, and perform automatic braking control in which the slip ratio s is used as control information. Attitude stabilization control and other controls can be performed similarly to a vehicle having a two-axis structure.

Next, the attitude control operation of the attitude control apparatus 1 according to the embodiment of the present invention will be described.

The attitude control device 1 is an electronic device including a computer circuit controlled by a program. The attitude control device 1 calculates and outputs the motion state of the vehicle using the driving operation input of the vehicle and the behavior data of the vehicle as inputs. A correction input for correcting the driving operation input and the disturbance input to the safe side is given to the vehicle, and the posture is stably controlled. That is, a numerical model that holds the physical characteristics of the vehicle as numerical values,
And an observer for taking the driving operation input of the vehicle as data and referring to a numerical model to estimate and calculate the response of the vehicle by a transfer function. Is obtained by an auto-regression method (AR method), which is represented by a value obtained by multiplying the past data by a weighting coefficient A (m) at each time point.

For example, when the load weight changes, when the load appearance changes, or when the number of passengers changes, the actual behavior of the vehicle does not match the behavior of the numerical model. At this time, the parameters stored in advance in the numerical model of the vehicle are automatically changed to match the behavior. This update is executed when the vehicle is running safely, in which the behavior of the vehicle in response to a driving operation input or a disturbance input is sufficiently smaller than a dangerous level.

An example of the control flow of the attitude control device 1 is as shown in FIG. 3 for normal control.

When the state of the cargo changes or the number of passengers changes, the control illustrated in FIG. 4 is performed, and the parameters of the vehicle model are updated. This update is automatically performed by always monitoring whether or not a correction is required. The update of the vehicle data is executed based on the transfer function obtained by the autoregressive method (AR method). The process in the update mode shown in FIG. 4 is executed in step S4 shown in FIG. As described above, by using the autoregressive method (AR method), it is possible to perform control suitable for the current situation.

FIGS. 5A and 5B show examples of input data according to the embodiment of the present invention. FIG. 5A shows a steering angle, FIG. 5B shows a yaw rate, and FIG. 5C shows a side slip angle. 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 this and sends out the operation data shown in FIG. Along with this steering operation, the yaw rate sensor 6 detects the yaw rate and sends operation data shown in (b) to the attitude control device 1. At the same time, the lateral acceleration sensor 4 detects lateral acceleration and sends operation data shown in (c) to the attitude control device 1. That is, (a) shown in FIG. 5 is an input, and (b) and (c) are responses representing the behavior (behavior) of the vehicle.

The attitude control device 1 calculates a transfer function of the vehicle based on these data. The transfer function is a complex function. In a practical example, the transfer function can be displayed by displaying the frequency on the horizontal axis and the amplitude and phase on the vertical axis. Assuming a relatively simple model, the amplitude characteristic has a gentle downward slope curve with respect to the frequency, and the phase characteristic has a corresponding downward slope curve. FIGS. 6A and 6B are diagrams illustrating frequency characteristics of amplitude and phase with respect to the yaw rate. FIGS. 7A and 7B are diagrams illustrating frequency characteristics of amplitude and phase with respect to lateral acceleration. These are diagrams showing transfer functions calculated based on actual data.

Here, the attitude control and updating of the vehicle will be described. When the transfer function is determined in this manner, the dynamic characteristics of the vehicle are calculated using the transfer function, and when an abnormal movement exceeding a predetermined standard is predicted,
Attitude control is performed by applying a different brake pressure to each wheel to suppress abnormal movement of the vehicle. This is the same as a method that has been practically used for passenger cars, and a detailed description thereof will be omitted here. This technology is applied to a commercial vehicle (truck / bus). In a commercial vehicle, the transfer function itself representing the response of the vehicle varies depending on the load status, the number of passengers, and the like, so the transfer function is updated. .

FIG. 6 is a diagram for explaining this, and it is assumed that a function having a characteristic indicated by a broken line is already stored as a transfer function in a numerical model. This is a model when the load is in a standard form of about one third of the maximum load capacity. Suppose that a new additional load is loaded.
Then, both the total weight and the position of the center of gravity change. This naturally results in a different response of the vehicle to the same steering. That is, the transfer function already stored must be changed. Therefore, when the transfer function is newly calculated according to the behavior of the vehicle appearing in the sensor, a characteristic different from the transfer function already stored appears as shown by a solid line. This calculation is automatically performed as described with reference to FIG. When the difference, that is, the area to be shaded in FIG. 6 is larger than the preset limit value, the stored model itself is updated to a new calculated value indicating the current state as shown by a solid line. This is performed automatically as described in FIG. By updating such a numerical model of the transfer function that is automatically accumulated, it becomes possible to execute appropriate attitude control even when the load changes or the number of crew changes. .

Here, the control operation of the braking force or the driving force, which is a feature of the present invention, will be described. This operation is performed in step S4 shown in FIG. FIG. 8 is a flowchart showing a flow of a braking force or driving force control operation by the posture control apparatus according to the embodiment of the present invention.

The attitude control device 1 includes a brake pressure sensor 12
When it is detected that the brake has been operated from the output of, the outputs from the yaw rate sensor 6 and the steering angle sensor 14 are taken in, and the detection outputs from the wheel rotation speed sensors 10 of the left and right front wheels 8 and the left and right rear wheels 9 are obtained. Uptake, front wheel 8
The vehicle speed V 'is determined from the larger one of the wheel rotation speeds.
That is, it is assumed that the vehicle speed V ′ corresponding to the wheel having the higher wheel rotation speed is close to the true vehicle speed V.

Next, the detection output Gx from the longitudinal acceleration sensor 18 is taken in, and the tire force calculator 2 calculates the slip ratio (sf). FIG. 9 is a characteristic diagram showing the relationship between the acceleration Gy generated during braking and the slip ratio sf at a certain road surface friction coefficient. FIG. 1A shows 1G
A method for obtaining a slip ratio sf during braking is shown, and FIG.
Using the same curve, how to determine the slip ratio sf at the time of 0.6G braking will be described. Such a tire characteristic is stored as a map according to the difference in road surface friction coefficient, and the slip ratio sf is obtained from the measured acceleration Gx.

Using the value of the slip ratio sf, the true vehicle speed V is calculated by the following equation.

V = V '/ (1-sf) 0 <sf <10 0: Rolling, 1: Slip Next, using the calculated true vehicle speed, detected lateral acceleration Gy and yaw rate ω, The true sideslip angle β of the vehicle is calculated by the following equation: β = ∫ ((Gr / V) −ω) dt, and further, the obtained front wheel steering angle δ and the stored distance Lf from the center of gravity of the vehicle to the front wheel axis. And the distance Lr from the center of gravity of the vehicle to the rear wheel axle, the front wheel side slip angle (βf) and the rear wheel side slip angle (βr) are calculated by the following formula: βf = β + (Lf / V) ω−δ βr = β− (Lr / V) Calculate by ω.

At the same time, the actual braking force of each wheel is calculated by calculating the slip ratio of each wheel from the true vehicle speed V and the rotational speed of each wheel, and this is used as a longitudinal force Fx as an input to the vehicle model.

FIG. 10 (a) is a characteristic curve showing the relationship between the side slip angle β and the lateral force Fy for each of 0G braking, 0.6G braking and 1G braking, and FIG. 10 (b) shows the characteristic curve at a certain side slip angle. 4 is a characteristic curve showing a relationship between acceleration Gx and lateral force Fy during braking.

From the braking acceleration obtained from the calculated front slip angle βf of the front wheels, the rear slip angle βr of the rear wheels and the longitudinal force Fx (corresponding to the longitudinal acceleration Gx), the loss due to slip is added to this characteristic curve. The obtained lateral force Fr is obtained and used as an input of the vehicle model.

In order to determine the slip ratio s from the measured longitudinal acceleration Gx, it is necessary to know the road surface friction coefficient (μ). A method for estimating this in real time will be described below. FIG. 11 is a flowchart showing the flow of the road surface friction coefficient estimation operation.

For estimating the road surface friction coefficient, the physical constants of the vehicle include the mass M of the vehicle, the distance Lf from the center of gravity of the vehicle to the front wheel axle, and the distance from the center of gravity of the vehicle to the rear wheel axle. Lr and the moment of inertia I around the center of gravity of the vehicle are stored in advance. Further, detection outputs from the lateral acceleration sensor 4, the vehicle speed sensor 5, and the yaw rate sensor 6 are captured as electric signals,
The lateral acceleration Gy, the vehicle speed V, and the yaw rate ω of the vehicle are measured. Here, as the vehicle speed V, a value obtained from the rotation speed of the wheels is sufficient.

The side slip angle of the vehicle is β, and this side slip angle β
Is the time differential value of dS / dt, the lateral acceleration has the relationship of Gy = V ((dβ / dt) + ω). / Dt = (Gy / V) -ω is calculated, and the time differential value of the sideslip angle β is integrated over time to calculate the sideslip angle β.

The moment of inertia I about the center of gravity of the vehicle, the time differential value of the yaw rate ω dω / dt, the lateral force Ff of the front wheel, the distance Lf from the center of gravity to the front wheel axis, the lateral force F of the rear wheel
r, the distance Lr from the center of gravity to the rear wheel axle, the mass M of the vehicle, and the lateral acceleration Gy of the vehicle have a relationship of I (dω / dt) = 2Ff · Lf−2Fr · Lr with respect to the rotation direction of the vehicle. Regarding the translation direction of the vehicle, there is a relationship of M · Gy = 2Ff + 2Fr.

From these two relational expressions, the lateral force Ff generated at the front wheel 8 is given by: Ff = (I (dω / dt) + M · Gy · Lr) / 2 (L
f + Lr).

The net sideslip angle βf of the front wheel 8 is
As shown in FIG. 12, assuming that the yaw rate generated around the center of gravity of the vehicle while the vehicle is traveling at speed V is ω, the side slip angle generated at the front wheels is Lf, which is the distance from the center of gravity of the vehicle to the front wheel axis. When the steering is not performed, the sideslip angle becomes β + (Lf / V) ω. However, when the steering is performed at the steering angle δ, the sideslip angle is obtained by subtracting the steering angle δ from the state where the steering is not performed. βf = β + (Lf / V) ω−δ.

Assuming a constant Kf of the cornering power obtained from the specifications of the tire, the road surface friction coefficient μ of the front wheel 8 can be obtained by the following equation: μ = Ff / (Kf · βf).

[0052]

As described above, according to the present invention, the force that causes the vehicle to skid is accurately estimated in consideration of the slip of the wheels in the traveling direction of the vehicle, and the braking force or the driving force is estimated based on the estimation. Since the force can be adaptively controlled, it is possible to perform highly accurate vehicle attitude stabilization control.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing an example of mounting the device of the present invention on a vehicle.

FIG. 3 is a flowchart illustrating normal control performed by the attitude control apparatus according to the embodiment of the present invention.

FIG. 4 is a flowchart illustrating updating of a vehicle model parameter by the attitude control apparatus according to the embodiment of the present invention.

FIGS. 5A, 5B, and 5C are diagrams illustrating input data of a steering angle, a yaw rate, and a sideslip angle in the control of the attitude control device according to the embodiment of the present invention.

FIGS. 6A and 6B are diagrams illustrating an example of a transfer function represented by a gain and a phase in the control of the attitude control device according to the embodiment of the present invention.

FIGS. 7A and 7B are diagrams showing another example of the transfer function represented by the gain and the phase in the control of the attitude control device according to the embodiment of the present invention.

FIG. 8 is a flowchart showing a flow of a braking force or driving force control operation by the posture control apparatus according to the embodiment of the present invention.

FIGS. 9A and 9B are characteristic diagrams showing a relationship between a slip ratio and a longitudinal force.

10A is a characteristic diagram showing a relationship between a lateral slip angle and a lateral force, and FIG. 10B is a characteristic diagram showing a relationship between [gravity] acceleration and a lateral force.

FIG. 11 is a flowchart showing a flow of a road surface friction coefficient estimating operation performed by the road surface friction coefficient estimating device of the posture control apparatus according to the embodiment of the present invention;

FIG. 12 is a diagram illustrating a sideslip angle used for estimating a road surface friction coefficient in the embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 attitude control device 2 tire force calculation unit 3 ABS (automatic braking control device) 4 lateral acceleration sensor 5 vehicle speed sensor 6 yaw rate sensor 8 front wheel 9 rear wheel 10 wheel rotation speed sensor 11 brake booster actuator 12 brake pressure sensor 13 steering Steering wheel 14 steering angle sensor 15 electronic governor 16 governor sensor 17 roll rate sensor 18 longitudinal acceleration sensor

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Fujio Fujio 3-1-1 Hinodai, Hino-shi, Tokyo Inside Hino Automotive Industry Co., Ltd. (72) Hirokazu Okuyama 3-1-1 Hinodai, Hino-shi, Tokyo Hino Automotive Industry Co., Ltd.

Claims (3)

[Claims] 1. A vehicle model comprising constants including a mass M of a vehicle, a distance Lf from a center of gravity of the vehicle to a front wheel axle, a distance Lr from a center of gravity of the vehicle to a rear wheel axle, and a moment of inertia I around the center of gravity of the vehicle. Means for measuring the vehicle speed V ′ obtained from the longitudinal and lateral accelerations Gx and Gy of the vehicle, the vehicle rotational speed V ′ and the yaw rate ω of the vehicle as electric signals, the vehicle model and the electric vehicle. A vehicle attitude control device comprising: means for calculating the behavior of the vehicle from the signal; and means for individually and automatically controlling the braking force or driving force applied to each wheel based on the calculation result of the calculating means. The calculating means estimates a slip ratio between a wheel and a road surface in a traveling direction of the vehicle, and calculates a slip ratio before applying to each wheel of the vehicle under the slip ratio. Direction and transverse direction of the force F
An attitude control device for a vehicle, comprising a wheel force calculating means for obtaining x and Fy. 2. The relationship between the longitudinal acceleration Gx of the vehicle and the slip ratio s of the wheel measuring the vehicle speed V ′ is known, and the wheel force calculating means determines the measured longitudinal acceleration Gx.
x, the slip rate s of the wheel is obtained, and the vehicle speed V ′ is corrected by using the slip rate s to obtain the true vehicle speed V. From the true vehicle speed V and the rotation speed of each wheel, the true speed V of each wheel is obtained. 2. The vehicle attitude control device according to claim 1, further comprising means for calculating a slip ratio and obtaining a force Fx in a front-rear direction applied to each wheel. 3. The wheel force calculating means calculates a true vehicle speed V, a lateral acceleration Gy of the vehicle, a yaw rate ω of the vehicle, and respective distances L from the center of gravity of the vehicle to the front wheel axis and the rear wheel axis.
From the f, Lr, and the steering angle δ, the sideslip angles βf, βr of the front wheels and the rear wheels are obtained, and these sideslip angles βf,
3. The vehicle attitude control device according to claim 2, further comprising means for obtaining a lateral force actually acting on each wheel from βr and a braking force or a driving force actually acting on each wheel.