JPH1191538A - Estimation method for wheel friction circle radius - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate the friction circle radii of respective wheels individually. SOLUTION: The longitudinal forces of right and left rear wheels Fxgrl, Fxgrr based on longitudinal acceleration are computed (S20), the longitudinal forces Fxtrl, Fxtrr of the right and left rear wheels based on the output torque of a torque converter are computed (S30), the longitudinal forces Fxrl, Fxrr of the right and left rear wheels are computed as weighted mean values (S90). The vertical load Fzj of four wheels is computed (S40), and the cornering force Fyj of the four wheels is computed based on these (S50). When an automatic transmission is not in gear changing (S60 to 80), friction circle radii Rmrl, Rmrr are computed as the root sum squares of the longitudinal forces Fxrl, Fxrr and the cornering forces Fyrl, Fyrr (S100), and when in gear changing, the weight of the longitudinal forces based on the output torque of the torque converter is set to zero (80).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for estimating the radius of a friction circle of a wheel, and more particularly to a method of estimating a radius of a friction circle for each wheel.

[0002]

2. Description of the Related Art As one of methods for estimating the radius of a friction circle of a wheel in a vehicle such as an automobile, for example, as described in Japanese Patent Application Laid-Open No. Hei 4-331668 filed by the present applicant, the front and rear of the vehicle are described. 2. Description of the Related Art A method of detecting acceleration and lateral acceleration and estimating a root-sum-square of longitudinal acceleration and lateral acceleration when a wheel slip occurs as a friction circle radius of a wheel has been conventionally known.

[0003] The horizontal force acting between the road surface and the vehicle when the wheel is slipping is proportional to the friction coefficient of the road surface, and the horizontal force is calculated as the root-sum-square of the longitudinal acceleration and the lateral acceleration of the vehicle. Since it is proportional, according to the above-described method, it is possible to estimate the friction circle radius of the wheel as a value corresponding to the friction coefficient of the road surface.

[0004]

However, in the conventional method of estimating the radius of the friction circle according to the above-mentioned proposal, the radius of the friction circle of the wheel is estimated based on the horizontal force of the entire vehicle. Although it is possible to obtain a value corresponding to the friction coefficient of the road surface, there is a problem that the friction circle radius cannot be individually estimated for each wheel.

The present invention has been made in view of the above-mentioned problems in the conventional method of estimating the radius of the friction circle in the conventional damping force control apparatus. By estimating the horizontal force acting between the wheel and the wheel, the friction circle radius is accurately estimated individually for each wheel.

[0006]

According to the present invention, there is provided a method for estimating a radius of a friction circle of a wheel according to the present invention, wherein lateral force of each wheel is estimated. A step of estimating the longitudinal force of each wheel, a step of calculating the root-sum-square of the lateral force and the longitudinal force of each wheel, a step of detecting a wheel slip for each wheel, Estimating the root-sum-square when the wheel slip is detected as the friction circle radius of the wheel.

According to the first aspect of the present invention, the root-sum-square of the lateral force and the longitudinal force is calculated for each wheel, and the root-sum-square when wheel slip is detected for each wheel is determined by the friction of the wheel. Since the circle radius is estimated, the friction circle radius is accurately estimated individually for each wheel based on the horizontal force acting between the road surface and each wheel.

According to the present invention, in order to effectively achieve the above-mentioned main object, in the above-mentioned structure of the first aspect, the wheel is a driving wheel, and the step of estimating the front-rear force includes the right and left. Calculating the total driving force of the driving wheels; calculating the driving force difference between the left and right driving wheels based on the braking / driving force difference between the left and right driving wheels and the wheel rotational inertia force difference between the left and right driving wheels; Calculating the longitudinal force of each driving wheel based on the force and the driving force difference (the configuration according to claim 2).

According to this configuration, the total driving force of the left and right driving wheels is calculated, and the driving of the left and right driving wheels is performed based on the braking / driving force difference between the left and right driving wheels and the wheel rotational inertia difference between the left and right driving wheels. The force difference is calculated, and the longitudinal force of each driving wheel is calculated based on the total driving force and the driving force difference, so that the longitudinal force of each driving wheel is accurately estimated.

According to the present invention, in order to effectively achieve the above-mentioned main object, in the structure of the above-mentioned claim 2, the left and right drive wheels may be left and right rear wheels of a rear wheel drive vehicle or a front wheel drive vehicle. And the total driving force of the left and right driving wheels is calculated as a product of the longitudinal acceleration of the vehicle and the weight of the vehicle.

Generally, when the vehicle is a rear wheel drive vehicle or a front wheel drive vehicle, the longitudinal acceleration of the vehicle is equal to the total driving force of the left and right drive wheels. According to the configuration of the third aspect, since the product of the longitudinal acceleration of the vehicle and the weight of the vehicle is calculated as the total driving force of the left and right driving wheels, the total driving force of the left and right driving wheels is reliably estimated. .

According to the present invention, in order to effectively achieve the above-mentioned main object, in the configuration of the above-mentioned claim 2, the left and right drive wheels may be left and right rear wheels of a rear wheel drive vehicle or a front wheel drive vehicle. And the total driving force of the left and right driving wheels is calculated based on the output torque of a torque converter.

Since the left and right driving wheels are driven by the output torque of the torque converter, the total driving force of the left and right driving wheels corresponds to the output torque of the torque converter. According to the configuration of the fourth aspect, the total driving force of the left and right driving wheels is calculated based on the output torque of the torque converter.
The total driving force of the left and right driving wheels is reliably estimated.

[0014]

According to a preferred aspect of the present invention, in the configuration of the first aspect, the sum of the lateral forces of the left and right front wheels and the lateral force of the right and left rear wheels are determined based on the yaw rate and the lateral acceleration of the vehicle. The sum of the forces is calculated, the vertical load of each wheel is calculated based on the longitudinal acceleration and the lateral acceleration of the vehicle, and the lateral force of each wheel is calculated as a value proportional to the vertical load of the wheel (preferable). Aspect 1).

According to another preferred aspect of the present invention, in the configuration of the first aspect, the longitudinal force of one of the driving wheels is a half of a value obtained by subtracting the driving force difference from the total driving force. It is configured to be calculated as one, and the longitudinal force of the other driving wheel is calculated as the sum of the longitudinal force of one driving wheel and the driving force difference (preferred mode 2).

According to another preferred embodiment of the present invention, in the configuration of claim 3 or 4, the total driving force of the left and right driving wheels is calculated as a product of the longitudinal acceleration of the vehicle and the weight of the vehicle. It is configured to be calculated as an average value of the driving force calculated based on the driving force and the output torque of the torque converter (preferred mode 3).

According to another preferred embodiment of the present invention, in the configuration of the above-mentioned preferred embodiment 3, the driving force calculated based on the output torque of the torque converter is 0 during a predetermined time during and after a shift. (Preferred mode 4).

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram (A) showing a rear wheel drive vehicle equipped with an automatic transmission and in which the friction circle radii of the left and right rear wheels are estimated according to the present invention, and a block diagram (B) of a control system. .

In FIG. 1, reference numeral 10 denotes an engine, and a driving force of the engine 10 is transmitted to a propeller shaft 18 via an automatic transmission 16 including a torque converter 12 and a transmission 14. The driving force of the propeller shaft 18 is transmitted to the left rear wheel axle 22L and the right rear wheel axle 22R by the differential 20, whereby the left and right rear wheels 24RL and 24RR, which are the driving wheels, are driven to rotate.

On the other hand, the left and right front wheels 24FL and 24FR are both driven wheels and steering wheels, and although not shown in FIG. 1, a rack-and-wheel driven in response to the driver turning the steering wheel. It is steered via a tie rod by a pinion type power steering device.

The braking force of the left and right front wheels 24FL, 24FR and the left and right rear wheels 24RL, 24RR is controlled by a hydraulic circuit 28 of the braking device 26.
Wheel cylinders 30FL, 30FR, 30
It is controlled by controlling the braking pressure of RL and 30RR. Although not shown in the drawing, the hydraulic circuit 28 includes a reservoir, an oil pump, various valve devices, and the like, and the braking pressure of each wheel cylinder is normally driven in response to the driver's depressing operation of the brake pedal 32. It is controlled by a master cylinder 34 and, if necessary, by a vehicle motion control computer 36 as will be described in detail later.

A signal indicating the longitudinal acceleration Gx of the vehicle is sent from the longitudinal acceleration sensor 38 to the vehicle motion control computer 42.
A signal indicating the lateral acceleration Gy of the vehicle from the lateral acceleration sensor 40, a signal indicating the vehicle speed V from the vehicle speed sensor 42, a signal indicating the yaw rate γ of the vehicle from the yaw rate sensor 44, and the wheel speeds Vwr of the left and right rear wheels from the wheel speed sensors 46RL and 46RR.
l, the signal indicating Vwrr and the pressure P in the left and right rear wheel cylinders 30RL, 30RR from the pressure sensors 48RL, 48RR.
signals indicating rl and Prr, a signal indicating the shift position SP of the automatic transmission 16 from the shift position sensor 50,
A signal indicating the engine speed Ne from the speed sensor 52;
A signal indicating the output rotation speed Nout of the torque converter 12 is input from the rotation speed sensor 54.

The vehicle motion control computer 36 may be a microcomputer having a known configuration including a CPU, a ROM, a RAM, and an input / output port device. The longitudinal acceleration sensor 38 detects longitudinal acceleration with the acceleration direction of the vehicle as positive, and the lateral acceleration sensor 40 and the yaw rate sensor 44 detects lateral acceleration and the like with the left turning direction of the vehicle as positive. Further, the pressures Prl and Prr in the wheel cylinders 30RL and 30RR of the left and right rear wheels may be estimated based on, for example, the pressure in the master cylinder 34 and the like.

Although not shown in the flowchart, the vehicle motion control computer 36 calculates the target wheel speeds Vwt of the left and right rear wheels 24RL and 24RR as drive wheels based on the vehicle speed V, and calculates the actual wheel speed, the target wheel speed, The driving slip amounts SLrl and SLrr of the left and right rear wheels are calculated as the deviations of the left and right rear wheels, and the target braking forces Ftrl and Ftrr of the left and right rear wheels are calculated as values proportional to the driving slip amounts SLrl and SLrr. The pressure in the wheel cylinders 30RL and 30RR is controlled so as to achieve the corresponding target braking force.

The vehicle motion control computer 36 calculates the longitudinal forces Fxgrl and Fxgrr of the left and right rear wheels based on the longitudinal acceleration Gx, and calculates the longitudinal forces Fxtrl and Fxtrr of the right and left rear wheels based on the output torque of the torque converter. The longitudinal force Fxrl, Fxrr of the left and right rear wheels is calculated as an average value. The computer 36 also calculates the four-wheel contact load Fzj, calculates the four-wheel cornering force Fyj based on the contact load, and calculates the front-rear force Fxrl, Fxrr of the left and right rear wheels and the square root of the sum of squares of the cornering forces Fyrl, Fyrr. The wheel friction circle radii Rmrl and Rmrr are calculated.

In this case, the driving slip amounts SLrl and SLrr
Target braking force F for the left and right rear wheels calculated as a value proportional to
When trl and Ftrr are excessive in light of the friction circle radii Rmrl and Rmrr, respectively, the vehicle motion control computer 36 performs a guard process on the target braking force based on the friction circle radius to prevent the braking force of the left and right rear wheels from becoming excessive. To optimally control the traction of the left and right rear wheels.

Next, a main routine for calculating a friction circle radius of a wheel in the illustrated embodiment will be described with reference to a flowchart shown in FIG. The calculation according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals.

First, in step 10, a signal indicating the longitudinal acceleration Gx of the vehicle is read, and in step 20, the left and right rear wheels based on the longitudinal acceleration Gx are read in accordance with the subroutine shown in FIG. Front and rear force Fxgrl, Fxg
rr is calculated, and in step 30, the longitudinal forces Fxtrl and Fxtrr of the left and right rear wheels based on the output torque of the torque converter 12 are calculated according to a subroutine shown in FIG.

In step 40, the ground contact load Fzj (j = fl, f) of the four wheels according to the subroutine shown in FIG.
r, rl, rr) are calculated, and in step 50, the four-wheel cornering force Fyj (j = fl, fr, rl, rr) is calculated according to the subroutine shown in FIG.

In step 60, it is determined whether or not the automatic transmission 16 is shifting gears based on the SP signal from the shift position sensor 50, that is, during or during gear shift of the automatic transmission. It is determined whether or not it is within a predetermined time after completion and during a period during which the driving force of the left and right rear wheels is not stable, and if a negative determination is made, the process proceeds to step 70 in step 90. The weighting coefficient Kx is set to 1 and when a positive determination is made, the weighting coefficient Kx is set to 0 in step 80.

In step 90, the longitudinal acceleration Gx
The longitudinal force Fxrl, Fx of the left and right rear wheels according to the following equation 1 as a weighted average value of the longitudinal force Fxgrl, Fxgrr based on the torque and the longitudinal force Fxtrl, Fxtrr based on the output torque of the torque converter.
xrr is calculated, and in step 100, the friction circle radius Rmr of the left and right rear wheels according to the subroutine shown in FIG.
l and Rmrr are calculated.

## EQU1 ## Fxrl = (Fxgrl + Kx.Fxtrl) / 2 Fxrr = (Fxgrr + Kx.Fxtrr) / 2

The longitudinal force Fxgrl of the left and right rear wheels shown in FIG.
In step 21 of the Fxgrr calculation routine, the total longitudinal force Fxall of the left and right rear wheels is calculated in accordance with the following equation (2), where M is the weight of the vehicle. In step 22, Cpf
Is a correction coefficient Fxbrl for the braking force of the left and right rear wheels according to the following Equation 3 as a conversion coefficient from the brake hydraulic pressure to the longitudinal force.
Fxbrr is calculated.

[0034]

## EQU2 ## Fxall = M · Gx

## EQU3 ## Fxbrl = Cpf.Prl Fxbrr = Cpf.Prr

In step 23, the wheel acceleration Vwd is calculated as a time differential value of the left and right rear wheel speeds Vwrl, Vwrr.
rl and Vwdrr are calculated, and correction values Fxirl and Fxirr for the rotational inertia force of the left and right rear wheels are calculated according to the following Equation 4 using Cwf as a conversion coefficient from the wheel acceleration to the longitudinal force.

## EQU4 ## Fxirl = Cwf.Vwdrl Fxirr = Cwf.Vwdrr

In step 24, the longitudinal force difference ΔFxr between the left and right rear wheels is calculated according to the following equation (5).
In step 5, the longitudinal forces Fxgrl and Fxgrr of the left and right rear wheels based on the longitudinal acceleration Gx are calculated according to the following equation (6).

[0037]

ΔFxr = (Fxbrl + Fxirl) − (Fxbrr + Fxirr)

Fxgrl = (Fxall−ΔFxr) / 2 Fxgrr = (Fxall + ΔFxr) / 2

The longitudinal force Fxtrl of the left and right rear wheels shown in FIG.
In step 31 of the Fxtrr calculation routine, the slip ratio Rsl of the torque converter is calculated according to the following equation 7 based on the rotation speed Ne of the engine 10 and the output rotation speed Nout of the torque converter 12.

Rsl = Ne / Nout (when Ne ≧ Nout) Rsl = Nout / Ne (when Ne <Nout)

In step 32, the slip ratio Rsl
The capacity coefficient Cp of the torque converter is calculated from a map (not shown) for obtaining the capacity coefficient Cp of the torque converter 12, and in step 33, the input torque Tin of the torque converter is calculated according to the following equation (8). Is calculated.

[Equation 8] Tin = Cp · Ne ²

In step 34, the slip ratio Rsl
The torque ratio Rtq of the torque converter is calculated from a map (not shown) for obtaining the torque ratio Rtq of the torque converter 12, and in step 35, the output torque Tout of the torque converter is calculated according to the following equation (9). Is done.

## EQU9 ## Tout = Tin.Rtq

In step 36, as in step 22 in the flowchart shown in FIG.
Correction values Fxbrl, F for the braking force of the left and right rear wheels according to
xbrr is calculated, and in step 37, similarly to step 23 of the flowchart shown in FIG. 3, the correction value F for the rotational inertia of the left and right rear wheels is calculated according to the above equation (4).
xirl and Fxirr are calculated, and in step 38, the output torque Tout of the torque converter is calculated according to the following equation (10).
, Front-rear forces Fxtrl and Fxtrr of the left and right rear wheels are calculated.

Fxtrl = Tout / 2−Fxbrl + Fxirl Fxtrr = Tout / 2−Fxbrr + Fxirr

In step 41 of the four wheel ground contact load Fzj calculation routine shown in FIG. 5, H is the height of the center of gravity of the vehicle, L is the wheelbase of the vehicle, and Tr is the tread of the vehicle. 11 the longitudinal acceleration G of the vehicle
The load movement amounts ΔFx and ΔFy in the front-rear direction and the lateral direction due to x and the lateral acceleration Gy are calculated.

ΔFx = M · H · Gx / L ΔFy = M · H · Gy / Tr

In step 42, Mf and Mr are the weights of the vehicles carried by the left and right front wheels and the left and right rear wheels, g is the gravitational acceleration, and Kf is the roll rigidity distribution ratio of the front wheels (a positive constant less than 1). ), Ground contact loads Fzfi, Fzfo, Fzri, and Fzro of the turning inside front wheel, turning outside front wheel, turning inside rear wheel, and turning outside rear wheel are calculated according to the following Expression 12.

## EQU12 ## Fzfi = Mf.g-.DELTA.Fx / 2-.DELTA.Fy.KfFzfo = Mf.g-.DELTA.Fx / 2 + .DELTA.Fy.KfFzri = Mr.g + .DELTA.Fx / 2-.DELTA.Fy. (1-Kf) Fzro = Mr.g + .DELTA.Fx / 2 + .DELTA.・ (1-Kf)

In step 43, it is determined whether or not the lateral acceleration Gy of the vehicle is positive, that is, whether or not the vehicle is turning to the left. In step 44, the four-wheel contact load Fzj (j = fl, fr, rl, rr) is set according to the following equation (13), and if a negative determination is made, the following equation (14) is determined in step 45.
, The ground load Fzj of the four wheels is set. The turning direction of the vehicle may be determined based on the sign of the steering angle or the yaw rate γ, or may be determined based on a combination thereof.

[0045]

Fzfl = Fzfi Fzfr = Fzfo Fzrl = Fzri Fzrr = Fzro

Fzfl = Fzfo Fzfr = Fzfi Fzrl = Fzro Fzrr = Fzri

In step 51 of the four-wheel cornering force Fyj calculation routine shown in FIG. 6, the deviation Gy−V · γ between the lateral acceleration Gy of the vehicle and the product V · γ of the vehicle speed V and the yaw rate γ is calculated. The deviation of the lateral acceleration, that is, the side slip acceleration Vyd of the vehicle is calculated, and the side slip speed Vy is calculated by integrating the side slip acceleration Vyd. Further, the side slip speed Vy of the vehicle with respect to the longitudinal speed Vx (= vehicle speed V) of the vehicle is calculated. Is calculated as the ratio Vy / Vx of the vehicle body.

In step 52, the differential value βd of the slip angle β of the vehicle body and the differential value γd of the yaw rate γ of the vehicle
Lf is the distance between the center of gravity of the vehicle and the front wheel axle in the longitudinal direction of the vehicle, Lr is the distance between the center of gravity of the vehicle and the rear axle in the longitudinal direction of the vehicle, and Iz is the yaw of the vehicle. The total cornering forces Fyf and Fyr are calculated for each of the left and right front wheels and the left and right rear wheels as the moment of inertia according to Equation 15 below.

Fyf = {MV Lr (βd + γ) + Iz
・ Γd｝ / L Fyr = {MV ・ Lf ・ (βd + γ) -Iz ・ γd} /
L

In step 53, the cornering forces Fyj (j = fl, fr, r
l, rr) are calculated.

Fyfl = Fyf · Fzfl / (Fzfl + Fzfr) Fyfr = Fyf · Fzfr / (Fzfl + Fzfr) Fyrl = Fyr · Fzrl / (Fzrl + Fzrr) Fyrr = Fyr · Fzrr / (Frr)

Next, the calculation of the friction circle radii Rmrl and Rmrr of the left and right rear wheels will be described with reference to the flowchart shown in FIG. The calculation according to the flowchart shown in FIG. 7 is executed individually for the left rear wheel (j = rl) and the right rear wheel (j = rr).

In step 101 of the subroutine of FIG. 7, the average longitudinal force Fxj and the cornering force Fyj
, The tire force Fxyj is calculated according to the following equation (17), and in step 102, the target wheel speed Vwt is calculated from the map corresponding to the graph shown in FIG.

## EQU17 ## Fxyj = (Fxj ² + Fyj ² ) ^1/2

In step 103, it is determined whether or not the actual wheel speed Vwj exceeds the reference value Vwt + Vw1, using Vw1 as a positive constant, that is, whether or not the rear wheel is in an acceleration slip state. Is performed, and when a positive determination is made, the count value Cs of the counter is determined in step 104.
Is incremented by 1 and a negative determination is made in step 105 that the count value Cs of the counter is 0.
Is reset to

In step 106, it is determined whether or not the count value Cs of the counter is a reference value Cse (a positive constant integer), that is, whether or not the acceleration slip has continued for a predetermined time. When the determination is affirmative, the process proceeds to step 108, and when the determination is negative, the process proceeds to step 107.

In step 107, the actual wheel speed Vwj is set to the reference value Vw2 by setting Vw2 as a positive constant larger than Vw1.
It is determined whether or not the value exceeds wt + Vw2, that is, whether or not the rear wheel is in an excessive acceleration slip state.
When a negative determination is made, the process returns to step 10 without updating the friction circle radius. When an affirmative determination is made, the count value Cs of the counter is reset to 0 in step 108, and the friction value is determined in step 109. After the circle radius Rmj is updated to the tire generating force Fxyj calculated in step 101, the process returns to step 10.

Thus, according to the illustrated embodiment, the longitudinal forces Fxgrl and Fxgrr of the left and right rear wheels based on the longitudinal acceleration Gx are calculated in step 20, and the left and right rear wheels based on the output torque of the torque converter are calculated in step 30. The longitudinal forces Fxtrl and Fxtrr of the right and left rear wheels are calculated in step 90 as an average of these weights.
Is calculated.

In step 40, the ground contact load Fzj of the four wheels is calculated, and in step 50, the cornering force Fyj of the four wheels is calculated based on the ground load of each wheel.
In step 100, the front-rear force Fxrl, Fxr of the left and right rear wheels
The friction circle radii Rmrl and Rmrr of the left and right rear wheels are calculated as the square root of the sum of squares of r and the cornering forces Fyrl and Fyrr.

Therefore, according to the illustrated embodiment, the friction radius R of the left and right rear wheels is not the radius of the friction circle of the entire vehicle.
mrl and Rmrr can be individually and accurately estimated, whereby the driving force of the left and right rear wheels can be optimally controlled in relation to the friction circle radius, and the traction of the left and right rear wheels can be optimally controlled.

In particular, according to the illustrated embodiment, the longitudinal forces Fxrl and Fxrr of the left and right rear wheels are weighted average values of the longitudinal forces Fxgrl and Fxgrr based on the longitudinal acceleration Gx and the longitudinal forces Fxtrl and Fxtrr based on the output torque of the torque converter. When it is determined in step 60 that the automatic transmission is shifting, a weight coefficient Kx for the longitudinal force based on the output torque of the torque converter is determined in step 80.
Is set to 0, the front-rear force of the left and right rear wheels is calculated based on these in a situation where the driving force of the left and right rear wheels is not stable due to the shift of the automatic transmission. Incorrect calculation of the friction circle radii of the left and right rear wheels can be reliably prevented.

If the transmission is a vehicle of a manual type, step 30, steps 60 to 90 are omitted, and in step 100, the friction circle radii Rmrl and Rmrr of the right and left rear wheels are determined by the longitudinal acceleration Gx. Longitudinal force Fxgr based on
Calculated as the square root of the sum of squares of l, Fxgrr and cornering forces Fyrl, Fyrr.

In the above, the present invention has been described in detail with respect to a specific embodiment. However, the present invention is not limited to the above embodiment, and various other embodiments are included in the scope of the present invention. It will be clear to those skilled in the art that is possible.

For example, in the illustrated embodiment, the vehicle is a rear-wheel drive vehicle equipped with an automatic transmission, and the radius of the friction circle of the right and left rear wheels is estimated. It may be applied to the estimation of the friction circle radius of the left and right front wheels of the front wheel drive vehicle.

In the illustrated embodiment, the friction circle radii of the left and right rear wheels, which are the driving wheels, are estimated. However, the rolling resistance and the wheel cylinder in consideration of the steering angle of the driven wheels are taken into consideration. The frictional radius of the driven wheel is estimated as the square root of the sum of squares of the front and rear forces of the driven wheel and the cornering force of the driven wheel calculated in step 50. You may.

[0062]

As is apparent from the above description, according to the first aspect of the present invention, the root-sum-square of the lateral force and the longitudinal force is calculated for each wheel, and the wheel slip is calculated for each wheel. Since the square root of the sum of squares at the time of detection is estimated as the friction circle radius of the corresponding wheel, the friction circle radius is accurately estimated for each wheel individually based on the horizontal force acting between the road surface and each wheel. Accordingly, the vehicle behavior control by controlling the traction control of the drive wheels and the braking / driving force of the wheels can be appropriately performed without excess or deficiency.

According to the second aspect of the present invention, the total driving force of the left and right driving wheels is calculated, and the left and right driving wheels are driven based on the braking / driving force difference between the left and right driving wheels and the wheel rotation inertia difference between the left and right driving wheels. Since the driving force difference between the wheels is calculated, and the longitudinal force of each driving wheel is calculated based on the total driving force and the driving force difference, the longitudinal force of each driving wheel necessary for estimating the friction circle radius of each driving wheel is calculated. It can be accurately estimated.

Further, according to the third or fourth aspect of the present invention, it is possible to reliably estimate the total driving force of the left and right driving wheels required for estimating the longitudinal force of each driving wheel.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram (A) showing a rear wheel drive vehicle equipped with an automatic transmission and in which the friction circle radii of left and right rear wheels are estimated according to the present invention, and a block diagram (B) of a control system.

FIG. 2 is a flowchart illustrating a main routine of estimating a friction circle radius of right and left rear wheels in the embodiment.

FIG. 3 is a flowchart showing a subroutine for calculating the front and rear forces Fxgrl and Fxgrr of the left and right rear wheels based on the front and rear acceleration Gx in the embodiment.

FIG. 4 is a flowchart showing a subroutine for calculating the front and rear forces Fxtrl and Fxtrr of the left and right rear wheels based on the output torque of the torque converter in the embodiment.

FIG. 5 is a flowchart illustrating a subroutine for calculating a four-wheel ground contact load Fzj in the embodiment.

FIG. 6 is a flowchart illustrating a subroutine of a four-wheel cornering force Fyj calculation in the embodiment.

FIG. 7 shows a friction circle radius Rmrl of the left and right rear wheels in the embodiment.
, Rmrr is a flowchart showing a subroutine of calculation.

FIG. 8 is a graph showing a relationship between a vehicle speed V and a target wheel speed Vwt.

[Description of Signs] 10 ... Engine 12 ... Torque Converter 16 ... Automatic Transmission 20 ... Differential 26 ... Brake Device 28 ... Hydraulic Circuit 30FL-30RR ... Wheel Cylinder 36 ... Vehicle Motion Control Computer 38 ... Longitudinal Acceleration Sensor 40 ... Lateral Acceleration Sensor 42: Vehicle speed sensor 44: Yaw rate sensor 46RL, 46RR: Wheel speed sensor

Claims (4)

[Claims] 1. A method for estimating a friction circle radius of a wheel,
Estimating the lateral force of each wheel, estimating the longitudinal force of each wheel, calculating the root sum square of the lateral force and the longitudinal force for each wheel, and calculating the wheel slip for each wheel. Detecting, for each wheel, estimating the root-sum-square when wheel slip is detected for each wheel as the radius of the friction circle of the wheel. 2. The method according to claim 1, wherein the step of estimating the longitudinal force includes calculating a total driving force of the left and right driving wheels, and calculating a difference in braking / driving force of the left and right driving wheels and a wheel rotation of the left and right driving wheels. The method according to claim 1, further comprising: calculating a driving force difference between left and right driving wheels based on an inertial force difference; and calculating a longitudinal force of each driving wheel based on the total driving force and the driving force difference. 2. The method according to 1. 3. The left and right driving wheels are left and right rear wheels of a rear wheel driving vehicle or left and right front wheels of a front wheel driving vehicle, and the total driving force of the left and right driving wheels is a product of a longitudinal acceleration of the vehicle and a weight of the vehicle. 3. The method according to claim 2, wherein the operation is performed. 4. The vehicle according to claim 1, wherein the left and right drive wheels are left and right rear wheels of a rear wheel drive vehicle or left and right front wheels of a front wheel drive vehicle, and a total driving force of the left and right drive wheels is calculated based on an output torque of a torque converter. 3. The method according to claim 2, wherein the method comprises: