Method of calculating deflection of rotating tire, method of accumulating data of rotating tire, method of calculating contact length of rotating tire

• US 8,437,905 B2
• Filed: 04/20/2007
• Issued: 05/07/2013
• Est. Priority Date: 04/21/2006
• Status: Active Grant

• Current Assignee: Yokohama Rubber Company Limited
• Original Assignee: Yokohama Rubber Company Limited
• Inventors: Koguchi, Noritaka, Miyashita, Naoshi, Matsuda, Jun, Kitazaki, Tsuyoshi
• Primary Examiner(s): Tarcza, Thomas
• Assistant Examiner(s): TISSOT, ADAM D
• Application Number:
  US11/916,811
• Publication Number:
  US 20090118891A1
• Time in Patent Office: 2,209 Days
• Field of Search: 701/1, 701/29, 701/30, 701/35, 701/36, 701/41, 701 70- 72, 701/74, 701/75, 701/80, 701/93, 731/46, 731/462, 731/465, 735/70, 280/5.52, 280/5.521, 280/86.75, 280/86.751, 702/138, 702/141, 702/142, 702145-147, 702/155, 702/157, 702/158, 702/167
• US Class Current: 701/29.1
• CPC Class Codes: B60C 23/064 comprising tyre mounted deformation sensors, e.g. to determine road contact area
• CPC Class Codes: G01B 21/32 for measuring the deformation in a solid
• CPC Class Codes: G01M 17/02 Tyres

Abstract

A method of calculating deflection of a rotating tire, through high speed data processing, based on measurement time series data of acceleration on a tire tread portion has the following steps. A step of acquiring measurement time series data of acceleration on a tire circumference in a radial direction of a rotating tire; a step of extracting acceleration data in a vicinity of a contact region from the acquired measurement data and subjecting the extracted acceleration data to least-square regression using a second-order differential function expression of a deflection function expression that represents a peak shape having a peak value and a curve gradually approaching to zero on both sides thereof, whereby a deflection function parameter values are determined; and a step of calculating a contact deflection from the deflection function expression determined by the deflection function parameter values.

Claims

1. A method of calculating deflection of a rotating tire that calculates a distribution of deflections at a tire tread portion in a radial direction of the tire when the tire is rotating on a road surface, the method comprising:

an acquiring step of acquiring measurement time series data of acceleration in a radial direction at a predetermined position on a tire circumference of a rotating tire;

a least-square regression step of extracting acceleration data in a vicinity of a contact region of the tire from the acquired measurement time series data of acceleration at the predetermined position on the tire circumference, and, using a deflection function expression that represents a peak shape having a peak value and a curve which is gradually approaching to zero on both sides of the peak shape as a function expression for reproducing the distribution of deflections at the tire tread portion, subjecting the extracted acceleration data to least-square regression using a second-order differential function expression of the deflection function expression to determine deflection function parameter value of the deflection function expression, solely from the acquired time series data of acceleration; and

a calculation step of calculating reproduced distribution of deflections of the rotating tire from the deflection function expression the deflection function parameter values of which have been determined.

2. The method of calculating deflection of a rotating tire according to claim 1, wherein the deflection function expression that represents the peak shape and reproduces an asymmetric shape of the distribution of deflections during cornering, braking, and driving of the tire is an asymmetrical Gaussian type function expression having a curve representing an asymmetrical shape on both sides of a peak, in accordance with the parameter values.

3. The method of calculating deflection of a rotating tire according to claim 1, wherein the deflection function expression is any one of formulas (1-1), (1-2), (1-3), (1-4) and (1-5) below:

4. The method of calculating deflection of a rotating tire according to claim 1, wherein the measurement time series data of acceleration in the radial direction is data acquired by an acceleration sensor mounted on the tire tread portion, the acceleration sensor being adapted for measuring acceleration in the radial direction.

5. The method of calculating deflection of a rotating tire according to claim 4, wherein the acceleration sensor is mounted at a center in a width direction of the tire tread portion, on a liner portion, on an outer periphery of a belt ply, or inside a cap tread.

6. The method of calculating deflection of a rotating tire according to claim 4, wherein as the acceleration sensor, a plurality of acceleration sensors are mounted on the tire tread portion in the width direction, and measurement time series data of acceleration in the radial direction is obtained from each of the plurality of acceleration sensors.

7. The method of calculating deflection of a rotating tire according to claim 5, wherein as the acceleration sensor, a plurality of acceleration sensors are mounted on the tire tread portion in the width direction, and measurement time series data of acceleration in the radial direction is obtained from each of the plurality of acceleration sensors.

11. The method of calculating deflection of a rotating tire according to claim 1, further comprising:

a smoothing processing step of performing smoothing processing on the measurement time series data of acceleration in the radial direction acquired by the acquiring step to remove noise components of the acquired measurement time series data of acceleration and obtain the smoothed measurement time series data of acceleration before the least-square regression step.

12. The method of calculating deflection of a rotating tire according to claim 1, wherein the least-square regression step selects a time t at which radial acceleration becomes minimum as a contact center time to in the measurement time series data Az(t) of acceleration in the radial direction,

extracts the measurement time series data Az(t) of acceleration in the radial direction within a range corresponding to a predetermined angle range a center of which is a tire rotation phase angle in case of a time t equal to the contact center time t_c (t=t_c) as acceleration data in the vicinity of the contact region of the tire in data region to be regressed,

subjects the extracted acceleration data in the data region to be regressed to the least-square regression by using following formulas (2-1) and (2-2) represented by the deflection function expression T(t) and a polynomial B(t) representing low frequency background acceleration components due to tire rotation which are other than acceleration due to deflection deformation of the tire and are contained in the measurement time series data Az(t) of acceleration in the radial direction,

S=t−

t_c 

 

(2-1)

AZ(s)=d²T(s)/ds²+B(s) 

 

(2-2),

obtain coefficients of the deflection function expression T(t) and the polynomial B(t) as parameters to determine the deflection function parameter values of the deflection function expression T(t), and

removes the low frequency background acceleration components contained in the measurement time series data Az(t) of acceleration in the radial direction to determine the deflection function expression T(t).

13. The method of calculating deflection of a rotating tire according to claim 12, wherein, when the deflection function expression T(t) is represented by using a following formulas (3-1) and the polynomial B(t) is represented by using a following formulas (2-3),

$\begin{array}{c}T\end{array}$

(t)=a·

exp⁡

(-t2ct+d)⁢

(3⁢

-⁢

1)
B(t)=e₀t⁵+e₁t⁴+e₂t³+e₃t²+e₄t+e₅ 

 

(2-3)

Wherein a, c, d, and e₀ to e₅ denote the parameters, and a, c and d denote the deflection function parameter values of the deflection function expression T(t).

8. A method of accumulating data of a rotating tire, comprising:

an acquiring step of acquiring measurement time series data of acceleration in a radial direction at a predetermined position on a tire circumference of a rotating tire;

a least-square regression step for extracting acceleration data in a vicinity of a contact region of the tire from the acquired measurement time series data of acceleration at the predetermined position on the tire circumference, and, using a deflection function expression that represents a peak shape having a peak value and a curve which is gradually approaching to zero on both sides of the peak shape as a function expression for reproducing the distribution of deflections at the tire tread portion, subjecting the extracted acceleration data to least-square regression using a second-order differential function expression of the deflection function expression to determine deflection function parameter value of the deflection function expression, solely from the acquired time series data of acceleration; and

an accumulating step of accumulating the deflection function parameter values of the deflection function expression determined in the least-square regression step as data at every round of tire rotation.

14. The method of accumulating data of a rotating tire according to claim 8, wherein the least-square regression step

selects a time t at which radial acceleration becomes minimum as a contact center time t_c in the measurement time series data Az(t) of acceleration in the radial direction,

extracts the measurement time series data Az(t) of acceleration in the radial direction within a range corresponding to a predetermined angle range a center of which is a tire rotation phase angle in case of a time t equal to the contact center time t_c (t=t_c) as acceleration data in the vicinity of the contact region of the tire in data region to be regressed,

subjects the extracted acceleration data in the data region to be regressed to the least-square regression by using following formulas (2-1) and (2-2) represented by the deflection function expression T(t) and a polynomial B(t) representing low frequency background acceleration components due to tire rotation which are other than acceleration due to deflection deformation of the tire and are contained in the measurement time series data Az(t) of acceleration in the radial direction,

S=t−

t_c 

 

(2-1)

AZ(s)=d²T(s)/ds²+B(s) 

 

(2-2),

obtain coefficients of the deflection function expression T(t) and the polynomial B(t) as parameters to determine the deflection function parameter values of the deflection function expression T(t), and

removes the low frequency background acceleration components contained in the measurement time series data Az(t) of acceleration in the radial direction to determine the deflection function expression T(t).

15. The method of accumulating data of a rotating tire according to claim 14, wherein, when the deflection function expression T(t) is represented by using a following formulas (3-1) and the polynomial B(t) is represented by using a following formulas (2-3),

$\begin{array}{c}T\end{array}$

(t)=a·

exp⁡

(-t2ct+d)⁢

(3⁢

-⁢

1)
B(t)=e₀t⁵+e₁t⁴+e₂t³+e₃t²+e₄t+e₅ 

 

(2-3)

Wherein a, c, d, and e₀ to e₅ denote the parameters, and a, c and d denote the deflection function parameter values of the deflection function expression T(t).

9. A method of calculating a contact length of a rotating tire, comprising:

an acquiring step of acquiring measurement time series data of acceleration in a radial direction at a predetermined position on a tire circumference of a rotating tire;

a least-square regression step for extracting acceleration data in a vicinity of a contact region of the tire from the acquired measurement time series data of acceleration at the predetermined position on the tire circumference, and, using a deflection function expression that represents a peak shape having an peak value and a curve which is gradually approaching to zero on both sides of the peak shape as a function expression for reproducing the distribution of deflections at the tire tread portion, subjecting the extracted acceleration data to least-square regression using a second-order differential function expression of the deflection function expression to determine deflection function parameter value of the deflection function expression, solely from the acquired time series data of acceleration;

a calculation step of calculating the reproduced deflection in a vicinity of the contact region from the deflection function expression the deflection function parameter values of which have been determined; and

a contact length calculating step for calculating a contact length of the rotating tire based on the deflection of the tire which is calculated in the calculation step.

10. The method of calculating a contact length of a rotating tire according to claim 9, includes:

determining, in a tire rotation orbit represented by the curve of the deflection function expression that is determined by the deflection function parameter values, intersections between a horizontal line touching to a lowest point of the tire rotation orbit and an arcuate shaped rotation orbit representing zero deflection as A, B;

determining a center of tire rotation as O;

determining points on the horizontal line as point C and point D, provided that an angle ∠

COD which is created by the points C and D, and the center of tire rotation O has a certain angle from 50 to 95% of an angle ∠

AOB which is created by the intersections A, B and the center of tire rotation O; and

determining the length between the point C and the point D as the contact length of the rotating tire.

16. The method of calculating a contact length of a rotating tire according to claim 9, wherein the least-square regression step selects a time t at which radial acceleration becomes minimum as a contact center time t_c in the measurement time series data Az(t) of acceleration in the radial direction,

extracts the measurement time series data Az(t) of acceleration in the radial direction within a range corresponding to a predetermined angle range a center of which is a tire rotation phase angle in case of a time t equal to the contact center time t_c (t=t_c) as acceleration data in the vicinity of the contact region of the tire in data region to be regressed,

subjects the extracted acceleration data in the data region to be regressed to the least-square regression by using following formulas (2-1) and (2-2) represented by the deflection function expression T(t) and a polynomial B(t) representing low frequency background acceleration components due to tire rotation which are other than acceleration due to deflection deformation of the tire and are contained in the measurement time series data Az(t) of acceleration in the radial direction,

S=t−

t_c 

 

(2-1)

AZ(s)=d²T(s)/ds²+B(s) 

 

(2-2),

obtain coefficients of the deflection function expression T(t) and the polynomial B(t) as parameters to determine the deflection function parameter values of the deflection function expression T(t), and

removes the low frequency background acceleration components contained in the measurement time series data Az(t) of acceleration in the radial direction to determine the deflection function expression T(t).

17. The method of calculating a contact length of a rotating tire according to claim 16, wherein, when the deflection function expression T(t) is represented by using a following formulas (3-1) and the polynomial B(t) is represented by using a following formulas (2-3),

$\begin{array}{c}T\end{array}$

(t)=a·

exp⁡

(-t2ct+d)⁢

(3⁢

-⁢

1)
B(t)=e₀t⁵+e₁t⁴+e₂t³+e₃t²+e₄t+e₅ 

 

(2-3)

Wherein a, c, d, and e₀ to e₅ denote the parameters, and a, c and d denote the deflection function parameter values of the deflection function expression T(t).