JP7011998B2 - Vehicle control device - Google Patents

Description

The present invention relates to a vehicle control device that controls for suppressing slippage of drive wheels in a vehicle.

A vehicle traction control device that controls the output of a drive source to make the slip of the drive wheels follow a reference slip so that the drive wheels driven by the drive source generate optimum traction is described in, for example, Patent Document 1 below. It is well known as it is.

By the way, in the traction control of a conventional vehicle, when the front wheels and the rear wheels are slipping at the same time, the true value of the ground speed is unknown, so the error becomes large and it is difficult to accurately detect a minute slip. Is.

Even if slip can be detected accurately, when a vehicle equipped with front wheels and rear wheels as wheels turns, the wheels on the side of the driving wheels are cornered in addition to the driving force or braking force. Force (force in the direction perpendicular to the direction of travel of the wheels when the vehicle is viewed from above) also acts. Then, the load on the drive wheels becomes large, and the slip amount of the drive wheels increases. In this case, it was necessary to control the behavior of the vehicle to be stable.

Japanese Patent No. 5945571

The present invention has been made in view of the above points, and an object of the present invention is to provide a vehicle control device that controls to stabilize the behavior of a vehicle when turning.

In order to solve the above problems, the vehicle control device according to the present invention uses the drive source (E), the front wheels (WfR, WfL), the rear wheels (WrR, WrL), and the power from the drive source (E) as the front wheels. A power transmission member (D) that transmits to at least one of (WfR, WfL) or a rear wheel (WrR, WrL), and a tire (T) attached to the front wheels (WfR, WfL) and the rear wheels (WrR, WrL). , And the front wheel steering angle (δ ₁ ), which is the steering angle of the front wheels (WfR, WfL), is a tire (1) with respect to the vehicle (1) operated by the actuator (9). A vehicle control device having a control means (U) for controlling the running of the vehicle (1) while determining the slip state of the T). In the control means (U), the slip state of the tire (T) is the tire. The tire (T) of the front wheel (WfR, WfL) or the rear wheel (WrR, WrL) is in an elastic slip state in which the tire (T) apparently slips on the road surface due to the elastic deformation of (T), or the tire (T). It is determined whether T) is in a moving slip state in which it actually slips on the road surface, and which of the tires (T) attached to the front wheels (WfR, WfL) and the rear wheels (WrR, WrL) When it is determined that the slip state of the tire (T) has changed from the elastic slip state to the moving slip state, the rear wheel (WrR, It is characterized in that the rear wheel steering angle (δ ₂ ), which is the steering angle of WrL), is changed.

As described above, when the slip state of the tire transitions from the elastic slip state to the moving slip state, it is preferable to reduce the slip of the tire transitioned to the moving slip state. In this case, the cornering force of the front wheels and the cornering force of the rear wheels can be distributed at an appropriate ratio by changing the steering angle of the rear wheels so that the sliding state of the tire becomes the elastic sliding state. This reduces the load on the drive wheels and reduces the slippage of the tires that have transitioned to the moving slip state on the road surface, thereby minimizing the energy consumption of the drive source required for running. Further, by reducing the slip, an appropriate frictional resistance can be obtained from the road surface, and the behavior of the vehicle can be stabilized.

Further, in the vehicle control device, the control means (U) determines that the transition from the elastic slip state to the moving slip state is caused by the rotation fluctuation of the power transmission member (D) and the front wheels (WfR, WfL) or the rear wheels. The rotation fluctuation of the wheel (W) of the wheel (WrR, WrL) is detected, and the amplitude ratio (m) of the rotation fluctuation amplitude of the wheel (W) to the rotation fluctuation amplitude of the power transmission member (D) and the power transmission member (D). The slip identification amount (ζ ₂ ), which is an index of the slip state of the tire (T), is calculated from the phase delay (Ψ ₁ ) of the rotation fluctuation of the wheel (W) with respect to the rotation fluctuation of), and the slip discrimination amount (ζ ₂ ). Is compared with the reference value (ζ _S ) corresponding to the elastic slip limit of the tire (T) to determine the moving slip state, and when the slip discrimination amount (ζ ₂ ) <reference value (ζ _S ) is satisfied, the moving slip state is determined. It may be determined that the vehicle is in a slipped state.

Thereby, the boundary between the elastic slip and the moving slip can be appropriately determined.

Further, in the vehicle control device, the control means (U) calculates the center of gravity skid angle (β), which is the skid angle of the center of gravity of the vehicle (1), and the center of gravity skid angle (β) is out of the predetermined range. In this case, the rear wheel steering angle (δ ₂ ) is fixed so as to be parallel to the front-rear direction of the vehicle (1), or the amount of change of the rear wheel steering angle (δ ₂ ) from the parallel state. May be restricted.

As described above, when the center-of-gravity skid angle is out of the predetermined range, there is no room for increasing the center-of-gravity skid angle. In this case, the yaw angular velocity is increased by fixing the rear wheel steering angle so as to be parallel to the front-rear direction of the vehicle or limiting the amount of change of the rear wheel steering angle from the parallel state. Then, the center of gravity skid angle is reduced until the center of gravity skid angle is within a predetermined range. As a result, the vehicle behavior (turning) with respect to the operation of the operator is achieved by maintaining the center of gravity side slip angle within a predetermined range while stabilizing the vehicle behavior by reducing the slip of the tire transitioned to the moving slip state on the road surface. The responsiveness can be improved.

Further, in the vehicle control device, the front wheels (WfR, WfL) are composed of the right front wheel (WfR) and the left front wheel (WfL), and the rear wheels (WrR, WrL) are the right rear wheel (WrR) and the left. It is composed of a rear wheel (WrL), and the control means (U) calculates the center of gravity skid angle (β), which is the skid angle of the center of gravity of the vehicle (1), and the center of gravity skid angle (β) appears in the left direction. In this case, the driving force of the left front wheel (WfL) or the left rear wheel (WrL) is made smaller than that of the right front wheel (WfR) or the right rear wheel (WrR), and the center of gravity skid angle (β) appears in the right direction. In this case, the driving force of the right front wheel (WfR) or the right rear wheel (WrR) may be made smaller than that of the left front wheel (WfL) or the left rear wheel (WrL).

In this way, when the center of gravity skid angle appears to the left, the driving force of the left front wheel or the left rear wheel is made smaller with respect to the right front wheel or the right rear wheel, and when the center of gravity skid angle appears to the right, By reducing the driving force of the right front wheel or the right rear wheel with respect to the left front wheel or the left rear wheel, an increase in the center of gravity skid angle is suppressed. This makes it possible to improve the responsiveness of the vehicle behavior (turning) to the operation of the operator while stabilizing the behavior of the vehicle.

Further, in the vehicle control device, when the rear wheel steering angle (δ ₂ ) is changed, the control means (U) operates the rear wheel steering angle (δ ₂ ) and the actuator (9) (θ _H ). ), And the front wheel steering angle (δ ₁ ) may be corrected according to the control gain (i) between the operation amount (θ _H ) and the yaw angle velocity (γ) of the vehicle (1).

In this way, when the rear wheel steering angle is changed, the front wheel steering angle is corrected according to the value of the control gain between the rear wheel steering angle, the steering wheel operation amount, the steering wheel operation amount, and the yaw angle speed. If so, even if the rear wheel steering angle is changed, the operation amount of the operator becomes constant, and the driver can easily operate the steering wheel.

The reference numerals in the above parentheses indicate the reference numerals of the corresponding components of the embodiments described later as an example of the present invention.

According to the vehicle control device according to the present invention, the behavior of the vehicle at the time of turning can be stabilized.

It is a figure which shows the driving means and the braking means in the vehicle provided with the vehicle control device which concerns on 1st Embodiment. It is a figure which shows the modeled wheel. It is a figure explaining the elastic slip with rolling of a tire. It is a graph which shows the static torsion characteristic of a tire. It is a graph which shows the elastic slip characteristic of a tire. It is a graph which shows the relationship of the slip ratio of a tire with respect to a drive torque. It is a graph which shows the relationship of the slip ratio of a tire with respect to the coefficient of friction between a tire and a road surface. It is a figure which shows the dynamic model in a drive wheel. It is a graph which shows the rotation fluctuation transmission characteristic between a differential device and a drive wheel. It is a figure which shows the relationship between the slip state of a tire, and the vibration mode. It is a figure which shows the root locus of elastic sliding mode and moving sliding mode. It is a figure which shows the wheel steering composition and various detection means in the vehicle provided with the control device for a vehicle. It is a figure which shows the angle which a wheel and the center of gravity of a vehicle make with respect to the traveling direction of a vehicle. It is a block diagram which shows the schematic structure of an electronic control unit. It is a flowchart explaining the outline of the control which concerns on 1st Embodiment. It is a flowchart which shows FIG. 15 in more detail. It is a figure which shows the relationship between the front wheel cornering force and the yaw angular acceleration and the rear wheel cornering force. It is a flowchart explaining the control which concerns on 2nd Embodiment. It is a flowchart explaining the control which concerns on 3rd Embodiment.

[First Embodiment]
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following description, first, a method of obtaining the slip state of the tire T, which is an index of control by the vehicle control device of the present embodiment, specifically, the slip state identifier ID _Slip (= ζ _S / ζ ₂ ). Explain how to find. Next, a method of estimating the center of gravity skid angle β, which is an index of control by the vehicle control device of the present embodiment, will be described. Then, using these slip state identifier ID _Slip (= ζ _S / ζ ₂ ) and the index of the center of gravity side slip angle β, a specific method of slip suppression control of the front wheels, which are drive wheels, by the vehicle control device will be described.

Further, in the explanation, the four wheels and the members arranged for them are each provided with subscripts indicating front, back, left and right. For example, it is described as left front wheel WfL, right front wheel WfR, left rear wheel WrL, and right rear wheel WrR. In addition, when generically referred to, L and R are omitted as necessary, such as front wheel Wf, rear wheel Wr, and the like.
[How to obtain the slip state identifier ID _Slip ]

FIG. 1 is a diagram showing driving means / braking means in a vehicle provided with a vehicle control device according to the first embodiment. As shown in FIG. 1, a four-wheeled vehicle using an internal combustion engine E as a driving source is a pair of left and right front wheels Wf and Wf (specifically, left front wheel WfL and right front wheel WfR) which are driving wheels. , A pair of left and right rear wheels Wr, Wr (specifically, left rear wheel WrL, right rear wheel WrR), which are driven wheels, are provided, and the driving force of the internal combustion engine E is the transmission M and the differential device D. It is transmitted to the left and right front wheels Wf and Wf via the left and right drive shafts Sd and Sd.

The master cylinder Cm, which is operated by the brake pedal P1 to generate brake fluid pressure, is applied to the left and right front wheel brake calipers Cf, Cf and the left and right rear wheel brake calipers Cr, Cr via the hydraulic pressure modulator H with a built-in electric oil pump. Be connected. The hydraulic pressure modulator H arbitrarily increases or decreases the brake hydraulic pressure generated by the master cylinder Cm and supplies the left and right front wheel brake calipers Cf and Cf and the left and right rear wheel brake calipers Cr and Cr to control the four wheels. The power can be controlled individually, and anti-lock brake control that suppresses wheel lock during deceleration and sideslip prevention control that suppresses sideslip during turning are performed.

The electronic control unit U (ECU: Electronic Control Unit), which is a control means consisting of a microcomputer, includes a brake operation amount detecting means S1 for detecting the brake hydraulic pressure generated by the master cylinder Cm from the pedaling force of the brake pedal P1 and an accelerator pedal. Accelerator opening detection means S2 that detects the amount of operation of P2, differential device rotation speed detection means S3 that detects the rotation speed of the differential device D, and front wheel speeds that detect the wheel speeds of the left and right front wheels Wf and Wf. The detecting means S4 and S4 are connected to the rear wheel speed detecting means S5 and S5 for detecting the wheel speeds of the left and right rear wheels Wr and Wr.

When the driver operates the brake pedal P1 and the master cylinder Cm generates the brake fluid pressure, the brake fluid pressure is transmitted to the front wheel brake calipers Cf, Cf and the rear wheel brake calipers Cr, Cr via the hydraulic pressure modulator H. , Front wheels Wf, Wf and rear wheels Wr, Wr are braked. When performing anti-lock brake control, the hydraulic pressure modulator H is operated by a command from the electronic control unit U, and the brake hydraulic pressure transmitted to the front wheel brake calipers Cf, Cf and the rear wheel brake calipers Cr, Cr is arbitrarily set. adjust.

Further, the electronic control unit U not only operates the throttle valve based on the accelerator opening detected by the accelerator opening detecting means S2 to perform drive-by-wire control for generating a predetermined driving force in the internal combustion engine E, but also performs an internal combustion engine. Traction control is performed to reduce the driving force of E and suppress the slip of the front wheels Wf and Wf, which are the driving wheels.

Next, the friction characteristics of the tire T will be described using the simple model shown in FIG. Normally, the wheel W is made of metal such as aluminum or steel and has an annular structure, so that it is sufficiently rigid as compared with the rubber tire T. That is, when the driving torque is applied to the wheel W, the sidewall portion and the tread portion of the tire T are deformed. In order to express this elastic deformation, the tread surface (ring of the ground plane) of the wheel W and the tire T is represented by a rigid body mass, and a state in which a spring force acts in a direction of suppressing twisting of both is considered. At the ground contact portion between the tire T and the road surface, the tire T is deformed due to the mass of the vehicle, and the tire T and the road surface are in contact with each other (ground contact surface) within a certain width (ground contact width). A frictional force F acts between the rubber and the road surface on the ground contact surface, and this frictional force F is expressed by the following equation.

F = μN ... (1)

μ is the coefficient of friction between the rubber and the road surface (changes depending on the aging of the tire T, the road surface, environmental conditions, etc.), and N is the ground contact load of the tire T. The frictional force F needs to be a force required to drive the vehicle (acceleration, deceleration, constant speed running) against the running resistance, that is, the driving force and the magnitude of the resultant force must be balanced.

Next, based on FIG. 3, consider a state in which a drive torque is applied to the wheel W, the tire T rolls, and the vehicle runs.

At the moment when the drive torque is applied to the wheel W, the torque is not transmitted to the tire T, and the tire T does not roll yet. At this time, the tire T is elastically deformed and a helix angle is generated between the wheel W and the tire T (see FIG. 3A). In this state, the tire T is in a static torsion state in which a helix angle is generated in proportion to the drive torque of the wheel W, and exhibits the characteristics as shown in FIG. 4 (for simplicity, non-linearity such as viscoelasticity is ignored).

When the helix angle is generated, torque is transmitted to the tire T as a reaction force thereof, and the tire T starts rolling (see FIG. 3B). One element of the tire T, which has undergone elastic deformation as the tire T rolls, leaves the contact patch and the elastic strain is released. At this time, the reaction force corresponding to the released elastic strain is insufficient for the magnitude required to transmit the drive torque of the wheel W, so that the rolling of the tire T tends to stop temporarily. However, one element of the tire T that has left the ground contact surface and a new element come into contact with the road surface to generate elastic strain, and the reaction force lost is recovered and the tire T rolls again. Such a case where the boundary conditions related to individual elements are not unique to each element and move with the movement of the elements is particularly called a moving boundary. Since the above phenomenon occurs continuously when the actual tire T continuously rolls (see FIG. 3C), the rolling angle of the tire T at a constant ratio to the rotation angle of the wheel W. Decreases. Since the rotation angle of the wheel W per unit time is proportional to the rotation speed (rotational angular velocity), the rotation angle of the tire T also decreases in proportion to the rotation speed of the wheel W, and a constant rotation transmission loss occurs (FIG. 3). (D)). This phenomenon is called elastic slip because apparent slip occurs between the wheel W and the road surface due to elastic deformation. By the way, since the elastic slip amount is generated at a constant ratio with respect to the rotation speed of the wheel W, the ratio of the rotation speed loss Δω due to slip to the rotation speed ω _wheel of the wheel W S _r = Δω / ω _wheel .
It is convenient to express with. This ratio _Sr is called the slip ratio.

S _r = Δω / ω _wheel … (2)

FIG. 5 shows the characteristics of the elastic slip of the tire T when the friction coefficient between the tire T and the road surface is sufficiently high (or the ground contact load of the tire T is sufficiently large). As a matter of course, there is a limit to the frictional force between the tire T and the road surface, so as the driving torque of the wheel W is increased, the ground contact surface and the road surface of the tire T finally start to slip. This is called moving slip to distinguish it from elastic slip. That is, as the drive torque of the wheel W is increased, elastic slip first develops as shown in FIG. 6, and finally movement slip is reached, and the drive wheel loses its grip.

The friction coefficient obtained by making the drive torque shown in FIG. 6 dimensionless using the equation (1) is generally used as the friction characteristic of the tire T (see the broken line in FIG. 7). By the way, these are the characteristics in an ideal state, and in addition to the non-linearity of elastic deformation due to the structure of the tire T and the viscoelasticity of rubber, the friction coefficient generally decreases when the ground contact surface is in a sliding friction state. The actual friction characteristics are as shown by the solid line in FIG. However, the frictional mechanism and physical properties resulting from state changes (called slip states) from elastic slip to mobile slip are similar.

From the above, in order to obtain the maximum grip force of the tire T, it is desirable to maintain the sliding state at the boundary between the elastic sliding state and the moving sliding state. Further, since the ground contact surface does not slip in the elastic slip state, it is desirable to maintain the slip state within the limit of the elastic slip state (boundary with the moving slip state) from the viewpoint of improving wear resistance. However, since the characteristics of the solid line (slip rate and friction coefficient) in FIG. 7 change due to individual differences of the tire T, secular variation, and changes in environmental conditions such as the road surface, the conventional method for detecting the slip rate captures the progress of the slip rate. Even if it is, the boundary (elastic slip limit) cannot be determined, and only a clear moving slip state can be determined. Therefore, in order to solve the above problems, a slip state detection method is required.

The principle of detecting the slip state of the present invention will be described. In the elastic slip state as shown in FIG. 3, a twist angle _φE is generated between the wheel W and the tire T due to elastic deformation, and the contact patch moves by the contact patch (the tire T rolls by the contact length). (The state where the ground contact surface has just been replaced). At this time, strain energy (k _T φ _E ^2/2 ) due to elastic deformation is stored in the ground plane before rolling, and this strain energy is released by rolling. Since this strain energy does not work on the running of the vehicle, it can be considered that the drive energy given from the wheel W is dissipated in the cycle of strain generation and release. If it is considered that such energy dissipation is caused by apparent slip (elastic slip), the frictional force acting on the ground plane can be written as F as the following equation.

k _T φ _E ^2/2 = FR φ _E = T _f φ _E … (3)

That is, the energy dissipation can be replaced with a virtual work due to frictional force and apparent slip as in the equation (3). k _T is the torsional rigidity of the tire T, R is the radius of the tire T, and T _f corresponds to the friction torque generated on the ground contact surface. On the other hand, when the tire T rolls corresponding to the helix angle _φE , if the rotation angle of the wheel W including the helix angle _φE is _φwheel , the slip ratio _Sr is based on the geometrical relationship.

S _r = φ _E / φ _wheel … (4)
Will be. From equation (2) and equation (4)

φ _E = (φ _wheel / ω _wheel ) Δω… (5)
And substituting this into equation (3),

T _f = (k _T φ _wheel / 2ω _wheel ) Δω = c _T Δω… (6)
The friction torque T _f is expressed by the viscous resistance force proportional to the slip (rotation speed loss) Δω generated between the wheel W and the road surface. Here, c _T corresponds to the viscosity coefficient and is proportional to the tire rigidity k _T. Therefore, the mechanical model from the differential device D to the tire contact surface can be represented as shown in FIG.

When the drive shaft Sd is driven from the differential device D at a constant rotation speed and is in a state of being balanced with the driving force of the tire T, the equilibrium point of the rigid body points corresponding to the differential device D, the wheel W, and the tire T is present. Assuming that the displacements (angles) from are θ ₁ , θ ₂ , and θ ₃ , respectively, the differential equation becomes the following equation.

Here, the equation (7) is

の変数変換により無次元化し、状態変数ｘ（ベクトル量）を、

The state variable x (vector quantity) is made dimensionless by the variable transformation of

と表すことにすると、式（７）の状態方程式表現は次式となる。

Then, the equation of state expression in Eq. (7) becomes the following equation.

The frequency response of the rotation speed of the wheel W to the rotation speed fluctuation of the differential device D is obtained from the equation (8) as shown in FIG. FIG. 9A shows the amplification ratio (amplitude ratio m) of the rotation fluctuation amplitude of the wheel W with respect to the rotation fluctuation amplitude of the differential device D, and FIG. 9B shows the rotation of the wheel W with respect to the rotation fluctuation of the differential device D. The phase delay of the fluctuation (Ψ ₁ ).

From the equation (6), the slip state approaches the moving slip state as the value of the friction viscosity coefficient c _T becomes smaller. In FIG. 9, (a) represents the response of the elastic slip state, and (c) represents the response of the moving slip state. Further, (b) corresponds to the boundary between the two slip states (elastic slip limit). Comparing (a) and (c) in FIG. 9, it can be seen that the peak (amplitude ratio) of the response shifts to the low frequency side as the moving slip state occurs. The vibration modes in which the response at this time peaks are referred to as the elastic sliding mode (a) and the moving sliding mode (c), and the difference between the respective vibration modes is shown in FIG.

In the elastic slip mode, the driving force is transmitted to the road surface by the elastic deformation of the tire _T , so that the elastic force generated by the tire rigidity (kt) also acts as a reaction force on the wheel W. Therefore, the wheel W vibrates under the resultant force of the elastic forces generated by the drive shaft rigidity (k ₁ ) and the tire rigidity (k _T ).

In the moving slip mode, the elastic force generated by the tire rigidity (k _T ) is released by the slip because the tire T and the road surface dynamically slide, and the reaction force acting on the wheel W also disappears. Therefore, the wheel W and the tire T are integrated and receive only the elastic force generated by the drive shaft rigidity (k ₁ ) and vibrate in the same phase.

From the above, the elastic sliding mode disappears and the moving sliding mode appears as the elastic sliding state shifts to the moving sliding state. Therefore, the moving slip state can be determined by monitoring the rotational fluctuation of the differential device D in the frequency band corresponding to this moving slip mode and the rotational fluctuation of the wheel W. In the moving slip mode, the amplitude ratio increases sharply, and the phase lag approaches 90 deg from 0 deg as shown in FIG. Therefore, the moving slip state can be determined by at least one of a sharp increase in the amplitude ratio and a phase lag of 90 deg approaching in the frequency band corresponding to the moving slip mode. The frequencies corresponding to the moving slip mode are the design specifications of the model shown in FIG. 8, that is, the drive shaft rigidity (k ₁ ), the tire rigidity (k _T ), the moment of inertia of the wheel W (I ₂ ), and the moment of inertia of the tire T (k 1). It is determined by I ₃ ) and can be obtained by calculating the eigenvalues and eigenvectors of the Jacobi matrix A shown in equation (8).

By the way, torque fluctuation generally occurs in the internal combustion engine E which is a drive source of the vehicle, and this torque fluctuation is also transmitted from the differential device D to the tire T. Factors of torque fluctuation include fluctuation of the in-cylinder pressure in the case of the internal combustion engine E and cogging torque due to the number of poles in the case of an electric motor. Rotational fluctuations due to the input torque fluctuations occur simultaneously in the differential device D. At this time, the rotational fluctuation of the differential device D is

で表されたとすると、式（８）は上記境界条件での強制加振と捉えることができる。Ａ_１は差動装置Ｄの回転変動振幅、Ωは加振力（内燃機関Ｅのトルク変動）の角振動数、ｔは時間である。このような強制加振状態において、式（８）に示す状態方程式は次式となる。

If it is expressed by, the equation (8) can be regarded as a forced vibration under the above boundary condition. A ₁ is the rotational fluctuation amplitude of the differential device D, Ω is the angular frequency of the exciting force (torque fluctuation of the internal combustion engine E), and t is the time. In such a forced vibration state, the equation of state shown in equation (8) is as follows.

From the equation (9), B represents an external force (vibration input), and the natural vibration mode (hereinafter referred to as the natural mode) of the original system is determined by the Jacobian determinant A. The parameters that determine the Jacobi matrix A are ρ, ω ₁ , ω ₂ , and ζ ₂ , but since ρ, ω ₁ , and ω ₂ are design specifications (known numbers), the eigenmode is the present invention. It is determined by the dimensionless quantity ζ ₂ corresponding to the slip discrimination amount of (which mode of the eigenmodes is excited depends on the excitation input B). Therefore, if the dimensionless quantity ζ ₂ can be known in some way, the above-mentioned slip state should be able to be indexed. Here, the periodic solution of Eq. (9) is assumed as follows.

By substituting this into Eq. (9) and determining the coefficients based on the Galerkin method, the following relational expression is obtained.

Since m is the amplification ratio (amplitude ratio) of the rotation fluctuation amplitude of the wheel W with respect to the rotation fluctuation amplitude of the differential device D, and Ψ ₁ is the phase delay of the rotation fluctuation of the wheel W with respect to the rotation fluctuation of the differential device D. By measuring the rotation fluctuation of the differential device D and the rotation fluctuation of the wheel W, the dimensionless quantity ζ ₂ can be obtained from the equation (10). Here, since there are two relational expressions in the equation (10), a maximum of two unknowns can be obtained. Therefore, in addition to the dimensionless quantity ζ ₂ , ω ₂ can be obtained at the same time, and even if the tire rigidity and the coefficient of friction change due to individual differences, aging, road surface conditions, etc., values suitable for the current situation can be obtained.

Next, the relationship between the dimensionless quantity ζ ₂ and the eigenmode will be described. The behavior of the eigenmode can be described by finding the eigenvalue λ of the Jacobian determinant A. FIG. 11 shows the behavior (root locus) of the eigenvalue λ corresponding to the above-mentioned moving slip mode. 11 (a) to 11 (c) correspond to (a) to (c) of FIG. 9 and (a) and (c) of FIG.

In FIG. 11, the horizontal axis represents the real axis, the vertical axis represents the imaginary axis, and the imaginary part indicates the vibration solution. It is shown that the roots are on the real axis and there is no vibration solution in the elastic sliding state (see (a) of FIG. 11). On the other hand, it is shown that the root has an imaginary part and vibration is generated in the moving slip state (see (c) of FIG. 11). That is, it can be seen that the moving slip mode appears when the dimensionless quantity ζ ₂ <0.86 (see (b) in FIG. 11). Therefore, the slip state can be determined as follows based on the value of the dimensionless quantity ζ ₂ .

Elastic slip state when dimensionless quantity ζ ₂ > 0.86

Elastic slip limit (grip limit) when dimensionless quantity ζ ₂ = 0.86

When dimensionless quantity ζ ₂ <0.86, moving slip state

However, the value of the dimensionless quantity ζ ₂ that is the elastic slip limit is ζ ₂ = 0.86 in the case of this embodiment, and this value differs depending on the design specifications.

From the above, the dimensionless quantity ζ ₂ is obtained by measuring the rotation fluctuation of the differential device D and the rotation fluctuation of the wheel W, and the magnitude relationship between the value of the dimensionless quantity ζ ₂ and the reference value ζ _S is obtained. It is possible to determine the slip state by comparing. ζ _S is ζ ₂ at the elastic slip limit, and in the above example, ζ _S = 0.86.

In the vehicle shown in FIG. 1, the rotation fluctuation of the differential device D detected by the differential device rotation speed detecting means S3 and the rotation fluctuation of the wheels W of the front wheels Wf and Wf detected by the front wheel speed detecting means S4 and S4. Based on this, the electronic control unit U monitors the value of the dimensionless quantity ζ ₂ , determines the transition to the moving slip state when ζ ₂ <ζ _S , and determines the transition to the moving slip state, and the internal combustion engine E via the electronically controlled throttle valve. Traction control is performed to limit the driving force, or anti-lock brake control is performed to limit the braking force of the front wheel brake calipers Cf and Cf via the hydraulic pressure modulator H.
Instead of limiting the driving force of the internal combustion engine E, the driving force may be limited by limiting the downshift of the transmission M. As a result, acceleration / deceleration that maximizes the grip performance of the tire T can be obtained, and at the same time, unnecessary wheel spin can be prevented to avoid a situation in which the behavior of the vehicle becomes unstable. Furthermore, the wear of the tire T can be suppressed by minimizing the occurrence of moving slip.

Using the relationship of equations (4) to (6),

ω ₂ / ζ ₂ = k _T / c _T = 2Δω / φ _E … (11)
Therefore, the slip Δω generated between the wheel W and the road surface can be expressed by using a dimensionless quantity.

Assuming that we are at the elastic slip limit and Δω = Δω _S ,

Δω _S = φ _E ω ₂ / _2ζS … (12)
Therefore, from equations (11) and (12),

Δω / Δω _S = ζ _S / ζ ₂ … (13)
Therefore, the ratio of the current slip to the elastic slip limit can be obtained by obtaining the dimensionless quantity ζ ₂ . Thereby, in addition to the determination of the slip state, the current slip margin with respect to the elastic slip limit can be quantitatively expressed.

Therefore, the value of ζ _S / ζ ₂ (slip state identifier ID _Slip ), which is the ratio of the dimensionless quantity ζ ₂ and ζ _S obtained by measuring the rotation fluctuation of the differential device D and the rotation fluctuation of the wheel W, is 1. The driving force or braking force can be increased / decreased (feedback control) so as to be. This makes it possible to control the elastic slip limit according to the excess or deficiency of the current driving force or braking force, accurately maintain the grip limit of the tire T, obtain the maximum acceleration / deceleration, and at the same time, the behavior of the vehicle. Can be stabilized. Furthermore, the wear of the tire T can be suppressed by minimizing the occurrence of moving slip.
[Estimation method of center of gravity skid angle β]

Next, a method of estimating the center of gravity skid angle β of the vehicle 1 will be described. First, the configuration required for estimating the center of gravity skid angle β of the vehicle 1 will be described. FIG. 12 is a diagram showing a wheel steering configuration and various detection means in a vehicle 1 provided with a vehicle control device.

As shown in FIG. 12, the vehicle 1 is a steering-by-wire four-wheel steering vehicle. The vehicle 1 includes a front wheel steering control device 4 used for steering the front wheels Wf and Wf, and rear wheel steering control devices 5R and 5L used for steering the rear wheels Wr and Wr. The front wheels Wf, Wf and the rear wheels Wr, Wr are rotatably supported by the respective knuckles 6. The knuckle 6 is supported by a suspension 7 including a suspension arm, a spring, a damper, and the like.

On the driver's seat side of the vehicle 1, a steering shaft 11 to which a steering wheel 9 (steering wheel: operator) is attached is installed at the rear end. A reaction force actuator 13 that gives a steering reaction force to the driver is installed on the steering shaft 11.

The front wheel steering control device 4 includes a steering gear 15 to which front wheel side knuckles 6fR and 6fL are connected to both ends thereof, a front wheel steering actuator 16 for driving the steering gear 15, and the like.

The rear wheel steering control devices 5R and 5L are provided with rear wheel steering actuators 8R and 8L between the vehicle 1 and the knuckles 6rR and 6rL, respectively. The rear wheel steering actuators 8R and 8L are linear electric actuators provided with an output rod driven in the axial direction by a motor. The tip of each output rod is connected to the knuckles 6rR and 6rL, respectively, and the steering angles (toe angles) of the rear wheels WrR and WrL change as the rear wheel steering actuators 8R and 8L expand and contract. The rear wheel steering control devices 5R and 5L can steer the left and right rear wheels WrR and WrL in the same direction (in the same phase) by extending one of the left and right rear wheel steering actuators 8R and 8L and contracting the other. can.

The electronic control unit U is connected to the front wheel steering actuator 16, the rear wheel steering actuators 8R, 8L, the reaction force actuator 13, and the like described above. The electronic control unit U is composed of a CPU, ROM, RAM, peripheral circuits, input / output interfaces, various drivers, and the like.

Further, various sensors that transmit detection signals to the electronic control unit U are arranged and connected to the vehicle 1. Specifically, the above-mentioned brake operation amount detecting means S1, accelerator opening degree detecting means S2, differential device rotation speed detecting means S3, front wheel speed detecting means S4, S4, rear wheel wheel speed detecting means S5, S5 , Connected to the electronic control unit U.

In addition, the vehicle 1 detects the steering angle detecting means S6 for detecting the operation amount θ _H (steering angle of the steering wheel) of the steering wheel 9 and the vehicle speed V which is the traveling speed of the center of gravity of the vehicle 1 as various sensors. Vehicle speed detecting means S7, lateral acceleration detecting means S8 for detecting lateral acceleration _ay (lateral G), yaw angle speed detecting means S9 for detecting yaw angle velocity γ (yaw rate), and front wheel rudder for detecting front wheel rudder angle δ ₁ . The angle detecting means S10, S10, the rear wheel steering angle detecting means S11, S11 for detecting the rear wheel steering angle δ ₂ , and the stroke detecting means S12, S12 for detecting the stroke positions of the rear wheel steering actuators 8R, 8L are arranged. Will be done. In addition, a front-back acceleration detecting means for detecting the front-back acceleration _Gx (not shown) is arranged.

A method of estimating the center of gravity skid angle β in the vehicle 1 having the detection means as described above will be described with reference to FIG. FIG. 13 is a diagram showing an angle formed by the center of gravity of the wheel and the vehicle with respect to the traveling direction of the vehicle. In FIG. 13, the front-rear direction of the vehicle 1 is the x direction, and the direction orthogonal to the x direction is the y direction. As described above, in the present embodiment, an example in which the front wheel Wf is used as a driving wheel and the rear wheel Wr is used as a driven wheel is shown.

As shown in FIG. 13, the front wheel Wf is separated from the center of gravity by _a distance l1 in front of the vehicle, and the rear wheel Wr is separated from the center of gravity by a distance _l2 in the rear of the vehicle. Further, the figure shows a case where the vehicle 1 turns to the left, and the state quantity on the front wheel Wf side in this case is the front wheel traveling speed _Vf which is the traveling speed of the front wheel Wf and the front wheel which is the steering angle of the front wheel Wf. The steering angle δ ₁ and the front wheel side slip angle α ₁ which is the side slip angle of the front wheel Wf. The front wheel steering angle δ ₁ is the angle formed by the front-rear direction of the front wheel Wf when the vehicle ₁ is viewed from above with respect to the front-rear direction (x direction) of the vehicle 1. The vector of the front wheel traveling speed when viewed is the angle formed with respect to the front-rear direction of the front wheel Wf. The state quantities on the rear wheel Wr side are the rear wheel traveling speed Vr, which is the traveling speed of the rear wheel _Wr , the rear wheel steering angle δ ₂ , which is the steering angle of the rear wheel Wr, and the rear slip angle of the rear wheel Wr. The wheel side slip angle is α ₂ . The rear wheel steering angle δ ₂ is the angle formed by the front-rear direction of the rear wheel Wr when the vehicle 1 is viewed from above with respect to the front-rear direction (x direction) of the vehicle 1, and the rear wheel side slip angle α ₂ is the vehicle 1. Is the angle formed by the vector of the rear wheel traveling speed when viewed from above with respect to the front-rear direction of the rear wheel Wr. The state quantities at the center of gravity of the vehicle 1 are the vehicle speed V, which is the traveling speed of the center of gravity of the vehicle 1, the side slip angle β of the center of gravity, which is the skid angle of the center of gravity of the vehicle 1, and the yaw angular velocity γ. The center of gravity skid angle β is an angle formed by the vector of the vehicle speed when the vehicle 1 is viewed from above with respect to the front-rear direction (x direction) of the vehicle 1. In the following description, these state quantities will be used.

When estimating the center of gravity skid angle β, first, the detected values of the rear wheel steering angle δ ₂ , the yaw angular velocity γ, and the rear wheel wheel speed _Vrw are acquired. The rear wheel speed _Vrw is the rotational speed of the rear wheel Wr (the peripheral speed of the rear wheel Wr on the contact patch between the tire and the road surface), and the rear wheel Wr is rolling without slipping on the road surface. The rear wheel traveling speed _{Vr corresponds to the rear wheel speed Vrw .} In general, the relations of equations (14) and (15) are geometrically established between the velocities in the x and y directions. The x-direction speed V _x is the x-direction component of the vehicle speed V, and the y-direction speed V _y is the y-direction component of the vehicle speed V.

Substituting equation (14) into equation (15) gives equation (16).

Here, since the rear wheel Wr is a driven wheel, if it is assumed that the influence of slippage can be ignored (V _r cos α ₂ ≈ V _rw , α ₂ ≈ 0), the equation (17) can be approximately obtained.

In this way, the center of gravity skid angle β is estimated (calculated) based on the rear wheel steering angle δ ₂ , the yaw angular velocity γ, the rear wheel wheel speed V _rw , and the distance l ₂ from the center of gravity of the vehicle 1 to the rear wheels Wr. ..
[Driving wheel slip suppression control]

Next, the electronic control unit U of the vehicle 1 is a front wheel based on the estimated values of the slip state identifier ID _Slip (= ζ _S / ζ ₂ ) and the center of gravity side slip angle β, which are the two indexes obtained as described above. Wf slip suppression control is performed. FIG. 14 is a block diagram showing a schematic configuration of the electronic control unit U.

As shown in FIG. 14, the electronic control unit U of the present embodiment has a tire slip state determination unit 21 that determines whether or not the slip state identifier ID _Slip is greater than 1, and a skid angle that estimates the center of gravity skid angle β. Target for setting the target front wheel cornering force CF _1t in the front wheel Wf, which is the driving wheel, based on the estimation unit 22, the slip state identifier ID _Slip (= ζ _S / ζ ₂ ), and the calculated value (estimated value) of the center of gravity side slip angle β. The cornering force setting unit 23, the target steering angle setting unit 24 that sets the target steering angle of the front wheel Wf or the rear wheel Wr using the value of the target front wheel cornering force CF _1t , and the drive current according to the target steering angle are set. It has a drive current setting unit 25. Detection signals from various sensors are input to the tire slip angle determination unit 21, the side slip angle estimation unit 22, the target steering angle setting unit 24, and the drive current setting unit 25, respectively, as necessary. Details will be described later.

With such a configuration, the set value of the drive current set by the drive current setting unit 25 is output to the front wheel steering actuator 16, the right rear wheel steering actuator 8R, and the left rear wheel steering actuator 8L. As described above, in the present embodiment, the steering-by-wire system is used, and the front wheel Wf and the rear wheel Wr can be controlled independently.

First, the outline of the control in the first embodiment will be described. FIG. 15 is a flowchart illustrating an outline of the control according to the first embodiment. As shown in FIG. 15, when the vehicle 1 is traveling, the electronic control unit U calculates the slip state identifier ID _Slip (= ζ _S / ζ ₂ ) and the center of gravity skid angle β by the above method (step s1).

Then, when the slip state identifier ID _Slip > 1, that is, when the movement slip occurs, and the center of gravity skid angle β is within the range of the center of gravity skid angle allowable value β _S (| β | ≦ β _S , It is determined whether β _S ≧ 0) or outside the range of the center-of-gravity side slip angle tolerance β _S (| β |> β _S , β _S ≧ 0) (steps 2, step s3).

When any of the conditions is satisfied, it can be said that the slip state of the front wheels is a moving slip, and the center of gravity side slip angle β still has a margin. In such a case, the electronic control unit U controls to increase the value of the rear wheel steering angle δ ₂ (step s10). Increasing the rear wheel steering angle δ ₂ leads to an increase in the rear wheel cornering force CF ₂ in the rear wheel Wr which is the driven wheel, while decreasing the front wheel cornering force CF ₁ in the front wheel Wf which is the driving wheel. As a result, the slip of the front wheel Wf is suppressed.

On the other hand, if any of the above conditions is not satisfied, it can be said that the slip state of the front wheel is either an elastic slip state or a state in which the center of gravity side slip angle β has no margin. In this case, the electronic control unit U controls to reduce the value of the rear wheel steering angle δ ₂ (step s20). By reducing the rear wheel steering angle δ ₂ in this way, the increase in the center of gravity skid angle β is suppressed.

When the center of gravity skid angle β is outside the range of the permissible center of gravity skid angle β _S (outside the predetermined range), the control for reducing the value of the rear wheel steering angle δ ₂ is to set the rear wheel steering angle δ ₂ to 0. It may be fixed so as to be (parallel to the front-rear direction of the vehicle 1), and the parallel position where the rear wheel steering angle δ ₂ becomes 0 (the rear wheel Wr parallel to the front-rear direction of the vehicle 1). The amount of change of the rear wheel steering angle δ ₂ from the position) may be limited.

After that, the electronic control unit U reflects the value of the rear wheel steering angle δ ₂ set as in step s10 or step s20 on the rear wheel Wr, and travels the vehicle 1 (step s4).

Next, the method of determining the value of the rear wheel steering angle δ ₂ in the above steps s10 and s20 will be described more specifically with reference to FIGS. 16 and 17. FIG. 16 is a flowchart showing FIG. 15 in more detail. FIG. 17 is a diagram showing the relationship between the front wheel cornering force CF ₁ and the yaw angular acceleration and the rear wheel cornering force CF ₂ .

In steps s2 and s3 shown in FIG. 16, the condition of the slip state identifier ID _Slip > 1 is satisfied, and the center of gravity skid angle β is within the range of the center of gravity skid angle allowable value β _S (| β | ≦ β _S , β. If both of the conditions that _S ≧ 0) are satisfied, the process proceeds to step s10.

In step s10, first, the absolute value of the target front wheel cornering force CF _1t is reduced (step s11). The absolute value of the target front cornering force CF _1t is the absolute value of the front cornering force CF ₁ and the absolute value of the rear cornering force CF ₂ on the line of the absolute value of all cornering force CF _A as shown in the upper figure of FIG. While comparing with, set the absolute value of the front wheel cornering force CF ₁ to a smaller value.

Next, it is confirmed whether or not the lateral acceleration _ay is 0 or a positive value (step s12). Here, when the lateral acceleration _ay is 0 or a positive value, since the vehicle is turning left, the absolute value of the target front wheel cornering force CF _1t is negatively added to obtain the target front wheel cornering force CF _1t . (Step s13). On the other hand, when the lateral acceleration _ay is a negative value, since the vehicle is turning to the right, the absolute value of the target front wheel cornering force CF _1t is used as it is as the target front wheel cornering force CF _1t (step s14).

Then, using the determined target front wheel cornering force CF _1t value, the value of the rear wheel steering angle δ ₂ is calculated using the equation (18) (step s15).

In the equation (18), in addition to the target front wheel cornering force CF _1t , the lateral acceleration _ay , the center of gravity side slip angle β, the yaw angular velocity γ, the vehicle speed V, and the front wheel steering angle δ ₁ are input. Here, as the physical property values, the weight m ₁ of the vehicle 1, the elastic modulus K ₂ of the tire T (CF ₂ = K ₂ α _2. The rear wheel side slip angle α ₂ is as described above), and the center of gravity of the vehicle 1. The distance l ₂ from the rear wheel Wr to the rear wheel Wr is used. The driving force (or braking force) F _f of the front wheels Wf and the driving force (or braking force (braking force in this embodiment)) Fr of the rear wheels _Wr are the output torque and ratio of the drive source and the brake fluid. Estimated from pressure. However, the influence may be small in the normal steering angle range, and in that case, it may be set to 0.

As described above, when the value of the rear wheel steering angle δ ₂ is calculated using the equation (18) in step s15, the value of the rear wheel steering angle δ ₂ is increased (step s10).

On the other hand, in step s2 and step s3 shown in FIG. 16, the condition of the slip state identifier ID _Slip > 1 or the center of gravity skid angle β is within the range of the center of gravity skid angle allowable value β _S (| β | ≦ β _S , β. If any of the conditions that _S ≧ 0) is not satisfied, the process proceeds to step s20.

In step s20, first, the absolute value of the target front wheel cornering force CF _1t is increased (step s21). The absolute value of the target front cornering force CF _1t is the absolute value of the front cornering force CF ₁ and the absolute value of the rear cornering force CF ₂ on the line of the absolute value of all cornering force CF _A as shown in the upper figure of FIG. While comparing with, set the value so that the absolute value of the front wheel cornering force CF ₁ becomes larger.

Next, it is confirmed whether or not the lateral acceleration _ay is 0 or a positive value (step s22). Here, when the lateral acceleration _ay is 0 or a positive value, since the vehicle is turning left, the absolute value of the target front wheel cornering force CF _1t is negatively added to obtain the target front wheel cornering force CF _1t . (Step s23). On the other hand, when the lateral acceleration _ay is a negative value, since the vehicle is turning to the right, the absolute value of the target front wheel cornering force CF _1t is used as it is as the target front wheel cornering force CF _1t (step s24).

Then, using the determined target front cornering force CF _1t value, the value of the rear wheel steering angle δ ₂ is calculated using the equation (18) (step s25).

As described above, when the value of the rear wheel steering angle δ ₂ is calculated using the equation (18) in step s25, the value of the rear wheel steering angle δ ₂ is reduced (step s20).

As described above, according to the vehicle control device of the present embodiment, when the slip state transitions from the elastic slip state to the moving slip state, the slip of the tire T transitioned to the moving slip state is reduced. Is preferable. In this case, by changing the rear wheel steering angle δ ₂ , the front wheel cornering force CF ₁ and the rear wheel cornering force CF ₂ can be distributed at an appropriate ratio. This reduces the load on the front wheels Wf, which are the drive wheels, and reduces the slippage of the tire T, which has transitioned to the moving slip state, on the road surface, thereby minimizing the energy consumption of the internal combustion engine E, which is the drive source required for running. It can be suppressed. Further, by reducing the slip, an appropriate frictional resistance can be obtained from the road surface, and the behavior of the vehicle 1 can be stabilized.

Further, in the present embodiment, the slip state is determined by the value of the slip state identifier ID _Slip (= ζ _S / ζ ₂ ), and the slip identification amount (ζ ₂ ) <reference value (ζ _S ), that is, When the slip state identifier ID _Slip > 1, it is determined that the tire T is in the moving slip state. Thereby, the boundary between the elastic slip and the moving slip can be appropriately determined.

Further, in the present embodiment, when the center of gravity skid angle β is out of the predetermined range (when the absolute value of the center of gravity skid angle β is not equal to or less than the permissible value of the center of gravity skid angle β _S ), there is room for increasing the center of gravity skid angle β. It will not be. In this case, the rear wheel steering angle δ ₂ is fixed so as to be parallel to the front-rear direction of the vehicle 1, or the amount of change of the rear wheel steering angle δ ₂ from the parallel state is limited. , The yaw angular velocity γ is increased, and the center slip angle β is reduced until the center slip angle β is within a predetermined range. As a result, the vehicle behavior with respect to the operation of the steering wheel 9 is maintained by maintaining the center of gravity side slip angle β within a predetermined range while stabilizing the vehicle behavior by reducing the slip of the tire T that has transitioned to the moving slip state on the road surface. The responsiveness of turning) can be improved.

[Second Embodiment]
A second embodiment of the present invention will be described. The same or corresponding components as those in the above-described embodiment are designated by the same reference numerals, and detailed description of the components will be omitted below. In the present embodiment, after the control of the first embodiment, the braking force of either the left front wheel WfL or the right front wheel WfR is increased depending on the situation. This is called drive wheel braking force increase control (step s30).

Next, the drive wheel braking force increase control will be specifically described. FIG. 18 is a flowchart illustrating control according to the second embodiment. As shown in FIG. 18, the electronic control unit U calculates the slip state identifier ID _Slip (= ζ _S / ζ ₂ ) and the center of gravity side slip angle β (step s1), and determines whether or not the slip state identifier ID _Slip > 1. Further, it is determined whether or not the center of gravity skid angle β is within the range of the center of gravity skid angle allowable value β _S (step s2, step s3). After that, the rear wheel steering angle δ ₂ is calculated (step s10, step s20) and reflected (step s4) in the same procedure as in the first embodiment.

After that, the process shifts to drive wheel braking force increase control (step s30). In step s30, first, the center of gravity skid angle β is calculated, and it is confirmed whether or not the center of gravity skid angle β is 0 or a positive value (step s31). Here, when the center of gravity side slip angle β is 0 or a positive value, the front of the vehicle faces the outside of the turning track of the center of gravity (headout) when turning left, and the vehicle is turning right. The front is facing the inside of the turning trajectory of the center of gravity (head-in). In this case, the braking force of the left front wheel WfL is adjusted to increase (step s32). As a result, the absolute value of the center of gravity skid angle β can be reduced. On the other hand, when the center of gravity side slip angle β is a negative value, the front of the vehicle faces the inside of the turning track of the center of gravity (head-in) when turning left, and the front of the vehicle is the center of gravity when turning right. It is in a state of facing the outside of the turning trajectory (head out). In this case, the braking force of the right front wheel WfR is adjusted to increase (step s33). As a result, the absolute value of the center of gravity skid angle β can be reduced.

By controlling the increase in the driving wheel braking force in this way, it is possible to suppress an increase in the center of gravity skid angle β. Then, in the first embodiment, when the rear wheel cornering force CF ₂ is increased, the state can be continued, and the slip state of the front wheel Wf can be reduced even in a long-time turning state. .. Further, by suppressing the side slip angle β of the center of gravity, it is possible to improve the responsiveness of the vehicle behavior (turning) to the operation of the steering wheel 9.

In the second embodiment, when the center of gravity skid angle β is 0 or a positive value, the braking force of the left front wheel WfL is adjusted to increase, and when the center of gravity skid angle β is a negative value, the braking force is adjusted to increase. The braking force of the right front wheel WfR was adjusted to increase, but it is not limited to this. That is, when the driving wheel is the front wheel Wf and the center of gravity skid angle β appears in the left direction, the driving force of the left front wheel WfL is made smaller with respect to the right front wheel WfR, and the center of gravity skid angle β appears in the right direction. In this case, the same effect can be obtained by setting the driving force of the right front wheel WfR to be smaller than that of the left front wheel WfL.

When the driving wheel is the rear wheel Wr, if the center of gravity side slip angle β appears in the left direction, the driving force of the left rear wheel WrL is set to be smaller than that of the right rear wheel WrR, and the center of gravity side slip angle β is on the right. If it appears in the direction, the driving force of the right rear wheel WrR may be smaller than that of the left rear wheel WrL.

As described above, in the present embodiment, in the electronic control unit U, when the center of gravity side slip angle β appears in the left direction, the driving force of the left front wheel WfL or the left rear wheel WrL is relative to the right front wheel WfR or the right rear wheel WrR. When the center of gravity side slip angle β appears in the right direction, the driving force of the right front wheel WfR or the right rear wheel WrR is made smaller than that of the left front wheel WfL or the left rear wheel WrL. As a result, the center of gravity side slip angle β can be suppressed, the behavior of the vehicle 1 can be stabilized, and the responsiveness of the vehicle behavior (turning) to the operation of the steering wheel 9 can be improved.

[Third Embodiment]
A third embodiment of the present invention will be described. The same or corresponding components as those in the above-described embodiment are designated by the same reference numerals, and detailed description of the components will be omitted below. In the present embodiment, the control for correcting the steering angle of the drive wheels is performed after the control of the first embodiment and before the control of increasing the driving wheel braking force of the second embodiment. This is called drive wheel steering angle correction control (step s40).

Next, the drive wheel steering angle correction control will be specifically described. FIG. 19 is a flowchart illustrating control according to the third embodiment. As shown in FIG. 19, the electronic control unit U calculates the slip state identifier ID _Slip (= ζ _S / ζ ₂ ) and the center of gravity side slip angle β (step s1), and determines whether or not the slip state identifier ID _Slip > 1. Further, it is determined whether or not the center of gravity skid angle β is within the range of the center of gravity skid angle allowable value β _S (step s2, step s3). After that, the rear wheel steering angle δ ₂ is calculated (step s10, step s20) and reflected (step s4) in the same procedure as in the first embodiment.

Next, using the values of the control gain i between the rear wheel steering angle δ ₂ , the steering wheel operating amount θ _H , the steering wheel operating amount θ _H , and the yaw angular velocity γ, the corrected front wheel steering angle is obtained from Eq. (19). Find δ ₁ . The steering wheel operation amount θ _H is the amount of operation of the steering wheel 9 by the driver.

Then, the corrected front wheel steering angle δ ₁ obtained by the equation (19) is reflected in the front wheel Wf (step s40). After that, the control shifts to the driving wheel braking force increase control shown in the second embodiment (step s30).

The steering system of the present embodiment is a steering-by-wire system in the present embodiment, and the front wheels Wf and the rear wheels Wr can be controlled independently. Therefore, the front wheel steering angle δ ₁ can be freely corrected as compared with the case where the steering wheel 9 and the front wheel Wf are mechanically connected.

As described above, in the present embodiment, when the rear wheel steering angle δ ₂ is changed, the rear wheel steering angle δ ₂ , the steering wheel operating amount θ _H , which is the operating amount of the steering wheel 9, and the steering wheel operating amount θ _H are used. The front wheel steering angle δ ₁ is corrected according to the control gain i with the yaw angle velocity γ of the vehicle 1. Therefore, even when the rear wheel steering angle δ ₂ is changed, such as when the rear wheel steering angle δ ₂ is controlled to increase or decrease, the steering wheel operation amount θ _H by the steering wheel 9 becomes constant, and the driver determines. The handle is easy to operate.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the present invention is not limited to the above embodiments, and various aspects are described within the scope of claims and the technical ideas described in the specification and drawings. It can be transformed.

Further, the application of the tire slip state determination method of the present invention is not limited to the traction control and the anti-lock brake control of the embodiment.

Further, the drive source of the present invention is not limited to the internal combustion engine E of the embodiment, and may be another type of drive source such as an electric motor.

Further, the drive wheel of the present invention is not limited to the front wheel Wf of the embodiment, and may be a rear wheel Wr or a four-wheel drive.

Further, since the purpose of the drive wheel braking force increase control of the present invention is to generate a drive force difference between the left and right drive wheels, in a vehicle having a left and right wheel drive force distribution mechanism and independent in-wheel motors for the left and right wheels, the vehicle has an independent in-wheel motor. The braking force increase is not limited to that of the embodiment, and a driving force difference may be generated between the left and right driving wheels by the driving force distribution.

1 ... Vehicle 9 ... Steering wheel (steering wheel: operator)
D ... Differential device (power transmission member)
E ... Internal combustion engine (drive source)
m ... Amplitude ratio T ... Tire U ... Electronic control unit (control means)
W ... Wheels Wf, WfR, WfL ... Front wheels Wr, WrR, WrL ... Rear wheels β ... Center of gravity skid angle β _S ... Center of gravity skid angle allowable value (predetermined value)
γ ... Yaw angle velocity δ ₁ ... Front wheel steering angle δ ₂ ... Rear wheel steering angle ζ ₂ ... Dimensionless quantity (slip discrimination quantity)
ζ _S … Reference value θ _H … Handle operation amount Ψ ₁ … Phase delay

Claims (5)

A drive source, front wheels, rear wheels, a power transmission member that transmits power from the drive source to at least one of the front wheels or the rear wheels, tires attached to the front wheels and the rear wheels, and an operator. For a vehicle having a control means for controlling the running of the vehicle while determining the slipped state of the tire for a vehicle in which the front wheel steering angle, which is the steering angle of the front wheels, is operated by the operator. It ’s a control device,
The control means is
The rotation fluctuation of the power transmission member and the rotation fluctuation of the front wheel or the rear wheel are detected, and the amplitude ratio of the rotation fluctuation amplitude of the wheel to the rotation fluctuation amplitude of the power transmission member and the rotation fluctuation of the power transmission member. The slip discrimination amount, which is an index of the slip state of the tire, is calculated from the phase delay of the rotation fluctuation of the wheel with respect to the above.
The slipped state of the tire is an elastic slipped state in which the tire of the front wheel or the rear wheel apparently slips on the road surface due to the elastic deformation of the tire, or the tire is on the road surface. On the other hand, it is determined based on the slip discrimination amount whether or not the tire is in a moving slip state in which the tire actually slips.
When it is determined that the slip state of any of the tires attached to the front wheels and the rear wheels has changed from the elastic slip state to the moving slip state.
A vehicle control device characterized in that the rear wheel steering angle, which is the steering angle of the rear wheels, is changed so that the sliding state of the tire is the elastic sliding state. The control means is
The moving slip state is determined by comparing the slip discrimination amount with a reference value corresponding to the elastic slip limit of the tire.
The vehicle control device according to claim 1, wherein the movement slip state is determined when the slip identification amount <the reference value. A drive source, front wheels, rear wheels, a power transmission member that transmits power from the drive source to at least one of the front wheels or the rear wheels, tires attached to the front wheels and the rear wheels, and an operator. For a vehicle having a control means for controlling the running of the vehicle while determining the slipped state of the tire for a vehicle in which the front wheel steering angle, which is the steering angle of the front wheels, is operated by the operator. It ’s a control device,
The control means is
The center of gravity skid angle, which is the skid angle of the center of gravity of the vehicle, is calculated.
The slipped state of the tire is an elastic slipped state in which the tire of the front wheel or the rear wheel apparently slips on the road surface due to the elastic deformation of the tire, or the tire is on the road surface. On the other hand, it is judged whether it is a moving slip state that actually slips, and
When it is determined that the slip state of any of the tires attached to the front wheels and the rear wheels is the elastic slip state, and the center of gravity side slip angle is out of the predetermined range. teeth,
The rear wheel steering angle is fixed so as to be parallel to the front-rear direction of the vehicle, or the amount of change of the rear wheel steering angle from the parallel state is limited.
The rear wheel steering angle, which is the steering angle of the rear wheels, is changed so that the sliding state of the tire is the elastic sliding state.
A vehicle control device characterized by this. A drive source, front wheels, rear wheels, a power transmission member that transmits power from the drive source to at least one of the front wheels or the rear wheels, tires attached to the front wheels and the rear wheels, and an operator. For a vehicle having a control means for controlling the running of the vehicle while determining the slipped state of the tire for a vehicle in which the front wheel steering angle, which is the steering angle of the front wheels, is operated by the operator. It ’s a control device,
The front wheel is composed of a right front wheel and a left front wheel.
The rear wheel is composed of a right rear wheel and a left rear wheel.
The control means is
The center of gravity skid angle, which is the skid angle of the center of gravity of the vehicle, is calculated.
The slipped state of the tire is an elastic slipped state in which the tire of the front wheel or the rear wheel apparently slips on the road surface due to the elastic deformation of the tire, or the tire is on the road surface. On the other hand, it is judged whether it is a moving slip state that actually slips, and
When it is determined that the slip state of any of the tires attached to the front wheels and the rear wheels has changed from the elastic slip state to the moving slip state.
The rear wheel steering angle, which is the steering angle of the rear wheels, is changed so that the sliding state of the tire is the elastic sliding state.
Further, when the center of gravity skid angle appears in the left direction, the driving force of the left front wheel or the left rear wheel is set to be smaller than that of the right front wheel or the right rear wheel.
Claim 1 to claim 1, wherein when the center of gravity skid angle appears in the right direction, the driving force of the right front wheel or the right rear wheel is made smaller than that of the left front wheel or the left rear wheel. Item 6. The vehicle control device according to any one of Item 3. A drive source, front wheels, rear wheels, a power transmission member that transmits power from the drive source to at least one of the front wheels or the rear wheels, tires attached to the front wheels and the rear wheels, and an operator. For a vehicle having a control means for controlling the running of the vehicle while determining the slipped state of the tire for a vehicle in which the front wheel steering angle, which is the steering angle of the front wheels, is operated by the operator. It ’s a control device,
The control means is
The slipped state of the tire is an elastic slipped state in which the tire of the front wheel or the rear wheel apparently slips on the road surface due to the elastic deformation of the tire, or the tire is on the road surface. On the other hand, it is judged whether it is a moving slip state that actually slips, and
When it is determined that the slip state of any of the tires attached to the front wheels and the rear wheels has changed from the elastic slip state to the moving slip state.
The rear wheel steering angle, which is the steering angle of the rear wheels, is changed so that the sliding state of the tire is the elastic sliding state.
The control means is
When the rear wheel steering angle is changed, the front wheel steering angle is corrected according to the rear wheel steering angle, the operating amount of the operator, and the control gain between the operating amount and the yaw angular velocity of the vehicle. A vehicle control device characterized by

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