JP3948076B2 - Estimation method of friction circle radius of wheel - 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

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for estimating a friction circle radius of a wheel, and more particularly to a method for estimating a friction circle radius for each wheel.
[0002]
[Prior art]
As one method of estimating the wheel frictional circle radius in a vehicle such as an automobile, the longitudinal acceleration and lateral acceleration of the vehicle are calculated as described in, for example, Japanese Patent Laid-Open No. 4-331668 concerning the application of the present applicant. A method of detecting and estimating a square sum of squares of longitudinal acceleration and lateral acceleration when a wheel slip occurs is conventionally known.
[0003]
Since 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, the horizontal force is proportional to the square sum of squares of the longitudinal acceleration and lateral acceleration of the vehicle. According to the above-described method, the friction circle radius of the wheel can be estimated as a value corresponding to the friction coefficient of the road surface.
[0004]
[Problems to be solved by the invention]
However, in the conventional method for estimating the frictional circle radius according to the above-mentioned proposal, the frictional circle radius of the wheel is estimated based on the horizontal force of the entire vehicle, so a value corresponding to the friction coefficient of the road surface is set. Although it can be obtained, there is a problem that it is impossible to estimate the friction circle radius for each wheel individually.
[0005]
The present invention has been made in view of the in above-mentioned problems a method of estimating the friction circle radii of the past, the main object of the present invention, acting between the road surface and the wheels in each wheel By estimating the force in the horizontal direction, the friction circle radius is accurately estimated individually for each wheel.
[0006]
[Means for Solving the Problems]
According to the present invention, the main problems as described above are the steps of estimating the lateral force of each wheel and the longitudinal force of each wheel according to the configuration of claim 1, that is, the method of estimating the frictional circle radius of the wheel. A step of estimating, a step of calculating a square sum of squares of the lateral force and the longitudinal force for each wheel, a step of detecting a wheel slip for each wheel, and a wheel slip being detected for each wheel the SSR possess a step of estimating the friction circle radii of the wheel, the sum and the lateral forces of the left and right front wheels on the basis of the yaw rate and lateral acceleration of the vehicle is at a step of estimating the lateral force of each wheel The total lateral force of the left and right rear wheels is calculated, the vertical load of each wheel is calculated based on the longitudinal acceleration and 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. It is calculated based on the sum of the lateral forces of the sum and the left and right rear wheels of the lateral force It is achieved by a method characterized in that.
[0007]
According to the configuration of claim 1, the square sum of the square force of the lateral force and the longitudinal force is calculated for each wheel, and the square sum square root when the wheel slip is detected for each wheel is the friction circle radius of the wheel. Since it 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. In particular, the total lateral force of the left and right front wheels and the total lateral force of the left and right rear wheels are calculated based on the yaw rate and lateral acceleration of the vehicle, and the vertical load of each wheel is calculated based on the longitudinal acceleration and lateral acceleration of the vehicle. Since the lateral force is calculated based on the total lateral force of the left and right front wheels and the total lateral force of the left and right rear wheels as a value proportional to the vertical load of the wheel, the lateral force of each wheel is accurately estimated, The friction circle radius of each wheel is accurately estimated.
[0008]
According to the present invention, in order to effectively achieve the main problems described above, in the configuration of claim 1, the wheel is a drive wheel, and the step of estimating the longitudinal force is performed by the left and right drive wheels. A step of calculating a total driving force, a step of calculating a driving force difference between left and right driving wheels based on a braking / driving force difference between left and right driving wheels and a wheel rotational inertial force difference between left and right driving wheels, and the total driving force and And a step of calculating the longitudinal force of each driving wheel based on the driving force difference (configuration of claim 2).
[0009]
According to this configuration, the total driving force of the left and right driving wheels is calculated, and the driving force difference between the left and right driving wheels is calculated 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. Since it 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 is accurately estimated.
[0010]
Further, according to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 2, the left and right drive wheels are the left and right rear wheels of a rear wheel drive vehicle or the left and right front wheels of a front wheel drive vehicle. The total driving force of the left and right driving wheels is calculated as the product of the longitudinal acceleration of the vehicle and the weight of the vehicle (configuration of claim 3).
[0011]
In general, 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 third aspect of the present invention, 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, so that the total driving force of the left and right driving wheels is reliably estimated. .
[0012]
Further, according to the present invention, in order to effectively achieve the main problem described above, in the configuration of claim 2, the left and right drive wheels are the left and right rear wheels of a rear wheel drive vehicle or the left and right front wheels of a front wheel drive vehicle. The total driving force of the left and right drive wheels is calculated based on the output torque of the torque converter (configuration of claim 4).
[0013]
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, since 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.
[0015]
[Preferred embodiment of the problem solving means]
According to one preferred embodiment of the present invention, in the configuration of the first aspect, longitudinal force of one of the driving wheels is calculated as one-half driving force difference than the sum of the driving force is subtracted value, The longitudinal force of the other driving wheel is configured to be calculated as the sum of the longitudinal force of one driving wheel and the driving force difference (preferred aspect 1 ).
[0016]
According to another preferred aspect of the present invention, in the configuration according to 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 comprised so that it may calculate as an average value of the driving force calculated based on force and the output torque of a torque converter (Preferred aspect 2 ).
[0017]
According to another preferred aspect of the present invention, in the configuration of the preferred aspect 2 described above, the driving force calculated based on the output torque of the torque converter is set to 0 for a predetermined time during and after the shift. (Preferred embodiment 3 ).
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
[0019]
FIG. 1 is a schematic configuration diagram (A) and a block diagram (B) of a control system showing a rear wheel drive vehicle in which an automatic transmission is mounted and a friction circle radius of left and right rear wheels is estimated according to the present invention.
[0020]
In FIG. 1, reference numeral 10 denotes an engine, and the 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 driving wheels are rotationally driven.
[0021]
On the other hand, the left and right front wheels 24FL and 24FR are both driven wheels and steered wheels, which are not shown in FIG. 1, but are rack and pinion type driven in response to steering of the steering wheel by the driver. It is steered via a tie rod by a power steering device.
[0022]
The braking forces of the left and right front wheels 24FL, 24FR and the left and right rear wheels 24RL, 24RR are controlled by controlling the braking pressures of the corresponding wheel cylinders 30FL, 30FR, 30RL, 30RR by the hydraulic circuit 28 of the braking device 26. 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 according to the depression operation of the brake pedal 32 by the driver. It is controlled by the master cylinder 34 and, if necessary, is controlled by a vehicle motion control computer 36 as will be described in detail later.
[0023]
The vehicle motion control computer 36 includes a signal indicating the longitudinal acceleration Gx of the vehicle from the longitudinal acceleration sensor 38, 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, and a vehicle indicating the vehicle speed V from the yaw rate sensor 44. A signal indicating the yaw rate γ, a signal indicating the wheel speeds Vwrl and Vwrr of the left and right rear wheels from the wheel speed sensors 46RL and 46RR, and a pressure Prl and Prr in the wheel cylinders 30RL and 30RR of the left and right rear wheels from the pressure sensors 48RL and 48RR. A signal indicating the shift position SP of the automatic transmission 16 from the shift position sensor 50, a signal indicating the engine rotational speed Ne from the rotational speed sensor 52, and a signal indicating the output rotational speed Nout of the torque converter 12 from the rotational speed sensor 54 are input. Is done.
[0024]
The vehicle motion control computer 36 may actually 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 vehicle acceleration direction as positive, and the lateral acceleration sensor 40 and yaw rate sensor 44 detect lateral acceleration and the like with the vehicle left turning direction as positive. Further, the pressures Prl and Prr in the wheel cylinders 30RL and 30RR for the left and right rear wheels may be estimated based on the pressure in the master cylinder 34, for example.
[0025]
Although not shown in the flowchart, the vehicle motion control computer 36 calculates the target wheel speed Vwt of the left and right rear wheels 24RL and 24RR, which are drive wheels, based on the vehicle speed V, and calculates the deviation between the actual wheel speed and the target wheel speed. The left and right rear wheel drive slip amounts SLrl and SLrr are calculated, and the left and right rear wheel target braking forces Ftrl and Ftrr are calculated as values proportional to the drive slip amounts SLrl and SLrr. The pressure in the wheel cylinders 30RL and 30RR is controlled so as to obtain a braking force.
[0026]
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, calculates the longitudinal forces Fxtrl and Fxtrr of the left and right rear wheels based on the output torque of the torque converter, and averages them. The longitudinal forces Fxrl and Fxrr of the left and right rear wheels are calculated. Further, the computer 36 calculates the ground load Fzj of the four wheels, calculates the cornering force Fyj of the four wheels based on the ground load, and the left and right rear squares of the front and rear forces Fxrl and Fxrr and the cornering forces Fyrl and Fyrr of the left and right rear wheels. The friction circle radii Rmrl and Rmrr of the ring are calculated.
[0027]
In this case, when the target braking forces Ftrl and Ftrr of the left and right rear wheels calculated as values proportional to the driving slip amounts SLrl and SLrr are excessive with respect to the friction circle radii Rmrl and Rmrr, respectively, the vehicle motion control computer 36 makes the target braking force. Is guarded with a friction circle radius to prevent excessive braking force on the left and right rear wheels and optimally control the traction on the left and right rear wheels.
[0028]
Next, a main routine for calculating the frictional circle radius of the wheel in the illustrated embodiment will be described with reference to the 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.
[0029]
First, at step 10, a signal indicating the longitudinal acceleration Gx of the vehicle is read, and at step 20, the longitudinal force Fxgrl of the left and right rear wheels based on the longitudinal acceleration Gx according to the subroutine shown in FIG. Fxgrr is calculated, and in step 30, the front and rear forces Fxtrl and Fxtrr of the left and right rear wheels based on the output torque of the torque converter 12 are calculated in accordance with the subroutine shown in FIG.
[0030]
In step 40, the four-wheel contact load Fzj (j = fl, fr, rl, rr) is calculated according to the subroutine shown in FIG. 5, and in step 50, the subroutine shown in FIG. The four-wheel cornering force Fyj (j = fl, fr, rl, rr) is calculated.
[0031]
In step 60, it is determined whether or not the automatic transmission 16 is shifting based on the SP signal from the shift position sensor 50, that is, during the shift stage of the automatic transmission or after the shift stage is completed. It is determined whether the driving force of the left and right rear wheels is not stable within a predetermined time. If a negative determination is made, the weighting coefficient in the calculation of step 90 is determined in step 70. If Kx is set to 1 and an affirmative determination is made, the weighting coefficient Kx is set to 0 in step 80.
[0032]
In step 90, the longitudinal forces Fxrl and Fxrr of the left and right rear wheels according to the following formula 1 are used as 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. In step 100, the friction circle radii Rmrl and Rmrr of the left and right rear wheels are calculated according to the subroutine shown in FIG.
[Expression 1]
Fxrl = (Fxgrl + Kx · Fxtrl) / 2
Fxrr = (Fxgrr + Kx · Fxtrr) / 2
[0033]
In step 21 of the left and right rear wheel front / rear force Fxgrl and Fxgrr calculation routine shown in FIG. 3, the total front / rear force Fxall of the left and right rear wheels is calculated according to the following equation 2 where M is the weight of the vehicle. In 22, correction values Fxbrl and Fxbrr for the braking force of the left and right rear wheels are calculated according to the following equation 3 using Cpf as the conversion coefficient from the brake hydraulic pressure to the longitudinal force.
[0034]
[Expression 2]
Fxall = M ・ Gx
[Equation 3]
Fxbrl = Cpf ・ Prl
Fxbrr = Cpf ・ Prr
[0035]
In step 23, wheel accelerations Vwdrl and Vwdrr are calculated as time differential values of the wheel speeds Vwrl and Vwrr of the left and right rear wheels, and Cwf is converted into the left and right according to the following equation 4 as a conversion coefficient from the wheel acceleration to the longitudinal force. Correction values Fxirl and Fxirr for the rotational inertia force of the rear wheels are calculated.
[Expression 4]
Fxirl = Cwf ・ Vwdrl
Fxirr = Cwf ・ Vwdrr
[0036]
In step 24, the longitudinal force difference ΔFxr between the left and right rear wheels is calculated according to the following equation 5, and in step 25, the longitudinal forces Fxgrl and Fxgrr of the left and right rear wheels based on the longitudinal acceleration Gx are calculated according to equation 6 below. Calculated.
[0037]
[Equation 5]
ΔFxr = (Fxbrl + Fxirl) − (Fxbrr + Fxirr)
[Formula 6]
Fxgrl = (Fxall−ΔFxr) / 2
Fxgrr = (Fxall + ΔFxr) / 2
[0038]
In step 31 of the left and right rear wheel front / rear force Fxtrl, Fxtrr calculation routine shown in FIG. 4, the torque converter is operated according to the following equation 7 based on the rotational speed Ne of the engine 10 and the output rotational speed Nout of the torque converter 12. A slip ratio Rsl is calculated.
[Expression 7]
Rsl = Ne / Nout (when Ne ≥ Nout)
Rsl = Nout / Ne (when Ne <Nout)
[0039]
In step 32, the capacity coefficient Cp of the torque converter is calculated from a map not shown in the figure for determining the capacity coefficient Cp of the torque converter 12 from the slip ratio Rsl. An input torque Tin of the torque converter is calculated according to Equation 8.
[Equation 8]
Tin = Cp ・ Ne ²
[0040]
In step 34, the torque ratio Rtq of the torque converter is calculated from a map not shown in the figure for obtaining the torque ratio Rtq of the torque converter 12 from the slip ratio Rsl. 9 is used to calculate the output torque Tout of the torque converter.
[Equation 9]
Tout = Tin · Rtq
[0041]
In step 36, the correction values Fxbrl and Fxbrr for the braking forces of the left and right rear wheels are calculated according to the above equation 3, as in step 22 of the flowchart shown in FIG. As in step 23 of the flowchart shown in FIG. 3, correction values Fxirl and Fxirr for the rotational inertial forces of the left and right rear wheels are calculated according to the above equation (4). At step 38, the torque converter is calculated according to the following equation (10). The front and rear forces Fxtrl and Fxtrr of the left and right rear wheels based on the output torque Tout are calculated.
[Expression 10]
Fxtrl = Tout / 2-Fxbrl + Fxirl
Fxtrr = Tout / 2−Fxbrr + Fxirr
[0042]
In step 41 of the four-wheel contact load Fzj calculation routine shown in FIG. 5, H is the center of gravity of the vehicle, L is the vehicle wheel base, and Tr is the vehicle tread. The forward and backward load movement amounts ΔFx and ΔFy resulting from the longitudinal acceleration Gx and the lateral acceleration Gy are calculated.
[Expression 11]
ΔFx = M ・ H ・ Gx / L
ΔFy = M ・ H ・ Gy / Tr
[0043]
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 stiffness distribution ratio of the front wheels (a positive constant less than 1). The ground contact loads Fzfi, Fzfo, Fzri, Fzro of the turning inner front wheel, the turning outer front wheel, the turning inner rear wheel, and the turning outer rear wheel are calculated according to the following equation (12).
[Expression 12]
Fzfi = Mf.g-.DELTA.Fx / 2-.DELTA.Fy.Kf
Fzfo = Mf.g-.DELTA.Fx / 2 + .DELTA.Fy.Kf
Fzri = Mr.g + .DELTA.Fx / 2-.DELTA.Fy. (1-Kf)
Fzro = Mr.g + .DELTA.Fx / 2 + .DELTA.Fy. (1-Kf)
[0044]
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 left, and if an affirmative determination is made, If the four wheel contact load Fzj (j = fl, fr, rl, rr) is set according to the following equation 13 and a negative determination is made, then at step 45, the four wheel contact load Fzj according to the following equation 14: Is set. Note that the turning direction of the vehicle may be determined by determining the sign of the steering angle or yaw rate γ, or a combination thereof.
[0045]
[Formula 13]
Fzfl = Fzfi
Fzfr = Fzfo
Fzrl = Fzri
Fzrr = Fzro
[Expression 14]
Fzfl = Fzfo
Fzfr = Fzfi
Fzrl = Fzro
Fzrr = Fzri
[0046]
In step 51 of the four-wheel cornering force Fyj calculation routine shown in FIG. 6, the lateral acceleration is calculated as a 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. The deviation, that is, the side slip acceleration Vyd of the vehicle is calculated, and the side slip acceleration Vyd is integrated to calculate the side slip speed Vy of the vehicle body. Further, the ratio Vy of the vehicle body side slip velocity Vy to the vehicle body longitudinal speed Vx (= vehicle speed V). The slip angle β of the vehicle body is calculated as / Vx.
[0047]
In step 52, the differential value βd of the slip angle β of the vehicle body and the differential value γd of the vehicle yaw rate γ are calculated, and Lf is the distance in the longitudinal direction of the vehicle between the center of gravity of the vehicle and the front axle. Lr is the vehicle longitudinal distance between the center of gravity of the vehicle and the rear axle, and Iz is the yaw moment of inertia of the vehicle. The total cornering forces Fyf and Fyr for each of the left and right front wheels and the left and right rear wheels are as follows: Calculated.
[Expression 15]
Fyf = {M · V · Lr · (βd + γ) + Iz · γd} / L
Fyr = {M · V · Lf · (βd + γ) −Iz · γd} / L
[0048]
In step 53, the cornering force Fyj (j = fl, fr, rl, rr) of each wheel is calculated according to the following equation (16).
[Expression 16]
Fyfl = Fyf · Fzfl / (Fzfl + Fzfr)
Fyfr = Fyf · Fzfr / (Fzfl + Fzfr)
Fyrl = Fyr · Fzrl / (Fzrl + Fzrr)
Fyrr = Fyr · Fzrr / (Fzrl + Fzrr)
[0049]
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).
[0050]
In step 101 of the subroutine of FIG. 7, the generated force Fxyj of the tire is calculated according to the following equation 17 based on the average longitudinal force Fxj and the cornering force Fyj, and in step 102 shown in FIG. The target wheel speed Vwt is calculated from the map corresponding to the graph.
[Expression 17]
Fxyj = (Fxj ² + Fyj ² ) ^1/2
[0051]
In step 103, it is determined whether Vw1 is a positive constant and whether the actual wheel speed Vwj exceeds the reference value Vwt + Vw1, that is, whether the rear wheel is in an acceleration slip state. When a positive determination is made, the count value Cs of the counter is incremented by 1 in step 104, and when a negative determination is made, the count value Cs of the counter is reset to 0 in step 105.
[0052]
In step 106, it is determined whether or not the count value Cs of the counter is the reference value Cse (a positive constant integer), that is, whether or not the acceleration slip has continued for a predetermined time. When a determination is made, the process proceeds to step 108, and when a negative determination is made, the process proceeds to step 107.
[0053]
In step 107, it is determined whether or not the actual wheel speed Vwj exceeds the reference value Vwt + Vw2 with Vw2 being a positive constant larger than Vw1, that is, whether or not the rear wheel is in an excessive acceleration slip state. When a negative determination is made, the friction circle radius is not updated, and the routine returns to step 10, and when an affirmative determination is made, the count value Cs of the counter is reset to 0 at step 108. In step 109, the frictional circle radius Rmj is updated to the tire generation force Fxyj calculated in step 101, and then the process returns to step 10.
[0054]
Thus, according to the illustrated embodiment, the front / rear forces Fxgrl and Fxgrr of the left and right rear wheels based on the longitudinal acceleration Gx are calculated at step 20, and the front / rear forces of the left and right rear wheels based on the output torque of the torque converter are calculated at step 30. Fxtrl and Fxtrr are calculated, and in step 90, the longitudinal forces Fxrl and Fxrr of the left and right rear wheels are calculated as the weighted average values.
[0055]
In step 40, the ground contact load Fzj of the four wheels is calculated. 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 longitudinal force Fxrl of the left and right rear wheels is calculated. , Fxrr and cornering forces Fyrl and Fyrr are calculated as the square sum of squares of friction circle radii Rmrl and Rmrr of the left and right rear wheels.
[0056]
Therefore, according to the illustrated embodiment, it is possible to accurately estimate the friction circle radii Rmrl and Rmrr of the left and right rear wheels independently of the friction circle radius of the entire vehicle, and thereby the right and left in relation to the friction circle radius. The traction of the left and right rear wheels can be optimally controlled by optimally controlling the driving force of the rear wheels.
[0057]
In particular, according to the illustrated embodiment, the longitudinal forces Fxrl and Fxrr of the left and right rear wheels are calculated as 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, the weight coefficient Kx for the longitudinal force based on the output torque of the torque converter is set to 0 in step 80, so that the automatic transmission In the situation where the driving force of the left and right rear wheels is not stable due to the shift of the left and right, the frictional circle radius of the left and right rear wheels is inaccurate due to the calculation of the longitudinal force of the left and right rear wheels based on these It is possible to reliably prevent calculation.
[0058]
In the case of a vehicle in which the transmission is a manual transmission, steps 30 and 60 to 90 are omitted. In step 100, the friction circle radii Rmrl and Rmrr of the left and right rear wheels are determined based on the longitudinal acceleration Gx. It is calculated as the square sum of squares of the forces Fxgrl and Fxgrr and the cornering forces Fyrl and Fyrr.
[0059]
Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.
[0060]
For example, in the illustrated embodiment, the vehicle is a rear wheel drive vehicle equipped with an automatic transmission, and the friction circle radius of the left and right rear wheels is estimated. It may be applied to estimate the friction circle radius of the left and right front wheels.
[0061]
In the illustrated embodiment, the frictional circle radii of the left and right rear wheels, which are drive wheels, are estimated, but the rolling resistance, the pressure in the wheel cylinder, etc. in consideration of the steering angle of the driven wheels, etc. The longitudinal force of the driven wheel is calculated on the basis of the above, and the frictional circle radius of the driven wheel is estimated as the square sum square root of the longitudinal force and the cornering force of the driven wheel calculated in step 50. .
[0062]
【The invention's effect】
As is clear from the above description, according to the configuration of claim 1 of the present invention, the square sum of squares of the lateral force and the longitudinal force is calculated for each wheel, and the wheel slip is detected for each wheel. Since the square sum of squares is estimated as the friction circle radius of the wheel, the friction circle radius can be accurately estimated individually for each wheel based on the horizontal force acting between the road surface and each wheel, Thus, the vehicle behavior control by controlling the traction control of the driving wheel and the braking / driving force of the wheel can be appropriately performed without excess or deficiency. In particular, the total lateral force of the left and right front wheels and the total lateral force of the left and right rear wheels are calculated based on the yaw rate and lateral acceleration of the vehicle, and the vertical load of each wheel is calculated based on the longitudinal acceleration and lateral acceleration of the vehicle. Since the lateral force is calculated based on the total lateral force of the left and right front wheels and the total lateral force of the left and right rear wheels as a value proportional to the vertical load of the wheel, the lateral force of each wheel can be accurately estimated. Thus, the friction circle radius of each wheel can be accurately estimated.
[0063]
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 rotational inertia force 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. Therefore, the longitudinal force of each driving wheel necessary for estimating the friction circle radius of each driving wheel is accurately estimated. can do.
[0064]
Furthermore, according to the structure of Claim 3 or 4 of this invention, the total driving force of the right-and-left driving wheel required for estimation of the longitudinal force of each driving wheel can be estimated reliably.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram (A) and a block diagram (B) of a control system showing a rear wheel drive vehicle equipped with an automatic transmission and in which the friction circle radius of left and right rear wheels is estimated according to the present invention.
FIG. 2 is a flowchart showing a main routine for estimating a friction circle radius of left and right rear wheels in the embodiment.
FIG. 3 is a flowchart showing a subroutine for calculating front and rear force Fxgrl and Fxgrr of the left and right rear wheels based on the longitudinal acceleration Gx in the embodiment.
FIG. 4 is a flowchart showing a subroutine for calculating front and rear force 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 showing a subroutine for calculating a contact load Fzj of four wheels in the embodiment.
FIG. 6 is a flowchart showing a subroutine of four-wheel cornering force Fyj calculation in the embodiment.
FIG. 7 is a flowchart showing a subroutine for calculating friction circle radii Rmrl and Rmrr of left and right rear wheels in the embodiment.
FIG. 8 is a graph showing a relationship between a vehicle speed V and a target wheel speed Vwt.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Engine 12 ... Torque converter 16 ... Automatic transmission 20 ... Differential 26 ... Braking 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 sensors 46RL, 46RR ... Wheel speed sensors

Claims (4)

A method for estimating the frictional circle radius of the wheel, a step of estimating the lateral force of each wheel, a step of estimating the longitudinal force of each wheel, and the square sum of squares of the lateral force and the longitudinal force for each wheel. a step of calculating, the step of detecting wheel slip for each wheel, and a step of the square root of sum of squares when the wheel slip is detected for each wheel for estimating the friction circle radii of the wheels possess, the In the process of estimating the lateral force of each wheel, the total lateral force of the left and right front wheels and the lateral force of the left and right rear wheels are calculated based on the yaw rate and lateral acceleration of the vehicle, and based on the longitudinal acceleration and lateral acceleration of the vehicle. vertical load of each wheel is calculated, Rukoto is calculated based on the sum of the lateral forces of the sum and the left and right rear wheels of the lateral force of the left and right front wheels as a value the lateral force of each wheel is proportional to the vertical load of the wheel A method characterized by. The wheel is a drive wheel, and the step of estimating the longitudinal force is based on the step of calculating the total drive force of the left and right drive wheels, and the braking / driving force difference between the left and right drive wheels and the wheel rotation inertia force difference between the left and right drive wheels. The method according to claim 1, comprising: calculating a driving force difference between left and right driving wheels; and calculating a longitudinal force of each driving wheel based on the total driving force and the driving force difference. . The left and right drive wheels are the left and right rear wheels of a rear wheel drive vehicle or the left and right front wheels of a front wheel drive vehicle, and the total driving force of the left and right drive wheels is calculated as a product of a vehicle longitudinal acceleration and a vehicle weight. 3. A method according to claim 2, characterized in that 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. 2. The method according to 2.

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