Wheel condition estimating apparatus

• US 6,264,292 B1
• Filed: 07/17/1998
• Issued: 07/24/2001
• Est. Priority Date: 07/18/1997
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Umeno, Takaji, Ono, Eiichi, Asano, Katsuhiro, Yamaguchi, Hiroyuki, Sugai, Masaru
• Primary Examiner(s): Oberleitner, Robert J.
• Assistant Examiner(s): SY, MARIANO ONG
• Application Number:
  US09/118,016
• Time in Patent Office: 1,103 Days
• Field of Search: 303/163, 303/149, 303/150, 303/148, 303/194, 303/195, 303/196, 303/112, 303/191, 303/146
• US Class Current: 303/196
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 8/172 Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence

Abstract

In a wheel condition estimating apparatus for estimating a wheel condition in a wheel resonance system including a frictional characteristic between a tire and a road surface, a transfer characteristic of the wheel resonance system from the vibration input to the output response is expressed by a transfer function including, as an unknown component of a wheel condition, a physical quantity relating to ease of a slipping between the tire and the road surface, an output response with respect to the vibration input to the wheel resonance system is detected and the unknown component which substantially satisfies the detected output response is estimated on the basis of the transfer function.

Claims

1. A wheel condition estimating apparatus for estimating a wheel condition in a wheel resonance system including a frictional characteristic between a tire and a road surface, comprising:

a detector configured to detect an output response to a vibration input to the wheel resonance system; and

an estimator configured to express a damping characteristic of said wheel resonance system during non-braking and braking from the vibration input to the output response by a vibration transfer characteristic model including at least a physical quantity relating to ease of a slipping between the tire and the road surface as an unknown component of a wheel condition, and to estimate at least said unknown component which substantially satisfies the output response detected by said detector on the basis of the vibration transfer characteristic model.

2. A wheel condition estimating apparatus according to claim 1, wherein said vibration transfer characteristic model is a transfer function of said wheel resonance system from the vibration input to the output response, and said estimator estimates said unknown component by identifying said transfer function.

3. A wheel condition estimating apparatus according to claim 2, wherein said estimator expresses said transfer function as a function of a parameter that expresses said physical quantity as said unknown component, estimates said parameter on the basis of said function and the output response detected by said detector, and estimates said unknown component on the basis of the estimated parameter.

4. A wheel condition estimating apparatus according to claim 1, further comprising a modifier configured to modify said vibration transfer characteristic model on the basis of the output response detected by said detector.

5. A wheel condition estimating apparatus according to claim 1, wherein said vibration transfer characteristic model further includes said physical quantity relating to a constant of a torsion spring of the tire as said unknown component of the wheel condition.

6. A wheel condition estimating apparatus according to claim 1, further comprising a vibration source configured to apply said vibration input to said wheel resonance system.

7. A wheel condition estimating apparatus according to claim 6, further comprising a vibration input detector configured to detect the vibration input applied to said wheel resonance system by said vibration source.

8. A wheel condition estimating apparatus according to claim 1, wherein said vibration input is at least one of a vibration torque to said wheel resonance system and a road surface vibration torque from a road surface to said wheel resonance system.

9. A wheel condition estimating apparatus according to claim 1, wherein said output response is a wheel speed.

10. A wheel condition estimating apparatus according to claim 1, further comprising:

a calculator configured to calculate a determining value to determine whether or not the output response detected by said detector is a periodical output; and

a selector configured to select a selected output response to be input to said estimator from the output response detected by said detector based on the basis of the determining value calculated by said calculator, wherein

said estimator uses the selected output response selected by said selector to estimate said unknown component.

11. A wheel condition estimating apparatus according to claim 10, wherein said calculator calculates a correlation coefficient, said correlation coefficient describing a correlation between the output response detected by said detector and a converted value obtained by converting said selected output response such that the periodical portion of said output response changes in correspondence to the change of said output response, as said determining value.

12. A wheel condition estimating apparatus according to claim 11, wherein said conversion is performed by any of an even number of differentiation operations, an even number of difference operations, an even number of integration operations, and an even number of summation operations.

13. A wheel condition estimating apparatus according to claim 12, wherein said calculator calculates a relative coefficient σ

from the following formula;

$\mathrm{\sigma <br><br>}=\frac{-\underset{k=1}{\overset{N}{\sum <br><br>}}<br><br>{\mathrm{\rho <br><br>}}_c^{N-k}<br><br>{\mathrm{\xi <br><br>}}_{\mathrm{y0}}<br><br>\left(k\right)<br><br>{\mathrm{\xi <br><br>}}_{\mathrm{y2}}<br><br>\left(k\right)}{\sqrt{\left(\underset{k=1}{\overset{N}{\sum <br><br>}}<br><br>{\mathrm{\rho <br><br>}}_c^{N-k}<br><br>{\mathrm{\xi <br><br>}}_{\mathrm{y0}}<br><br>\left(k\right)<br><br>{\mathrm{\xi <br><br>}}_{\mathrm{y0}}<br><br>\left(k\right)\right)<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\underset{k=1}{\overset{N}{\sum <br><br>}}<br><br>{\mathrm{\rho <br><br>}}_c^{N-k}<br><br>{\mathrm{\xi <br><br>}}_{\mathrm{y2}}<br><br>\left(k\right)<br><br>{\mathrm{\xi <br><br>}}_{\mathrm{y2}}<br><br>\left(k\right)\right)}}$

wherein;

ξ

_y0 is the output response;

ξ

_y2 is the converted value;

ρ

_c is a forgetting factor;

N is a number of the output responses detected by said detector; and

σ

is the relative coefficient.

14. A wheel condition estimating apparatus according to claim 10, wherein said calculator calculates said determining value when a predetermined number of output responses are detected by said detector.

15. A wheel condition estimating apparatus according to claim 10, further comprising a modifier configured to modify said vibration model on the basis of the output response detected by said detector.

16. A wheel condition estimating apparatus according to claim 10, wherein said vibration model further includes, a physical quantity relating to a constant of a torsion spring of the tire as said unknown component of the wheel condition.

17. A wheel condition estimating apparatus according to claim 10, further comprising a vibration source configured to apply a vibration input to said wheel resonance system.

18. A wheel condition estimating apparatus according to claim 17, further comprising a vibration input detector configured to detect the vibration input applied to said wheel resonance system by said vibration source.

19. A wheel condition estimating apparatus according to claim 10, wherein said vibration input is at least one of a vibration torque to said wheel resonance system and a road surface vibration torque from a road surface to said wheel resonance system.

20. A wheel condition estimating apparatus according to claim 10, wherein said output response is a wheel speed.

21. The wheel condition estimating apparatus according to claim 1, wherein said estimator carries out a comparative examination of said transfer characteristic of the wheel resonance system near the resonance frequency of the wheel.

22. The wheel condition estimating apparatus according to claim 21, wherein the resonance frequency of the wheel is around 40 Hz.

23. A wheel condition estimating apparatus for estimating a wheel condition in a wheel resonance system including a frictional characteristic between a tire and a road surface, comprising:

a detector configured to detect an output response with respect to a vibration input to the wheel resonance system;

an estimator configured to express a damping characteristic of said wheel resonance system from the vibration input to the output response by a vibration transfer characteristic model including at least a physical quantity relating to ease of a slipping between the tire and the road surface as an unknown component of a wheel condition, and to estimate at least said unknown component which substantially satisfies the output response detected by said detector on the basis of the vibration transfer characteristic model;

a calculator configured to calculate a determining value to determine whether or not the output response detected by said detector is a periodical output on the basis of said output response;

a selector configured to select an output response to be input to said estimator from among the output responses detected by said detector on the basis of the determining value calculated by said calculator; and

a vibration source configured to apply a vibration input to said wheel resonance system, wherein

said estimator uses the output response selected by said selector at a time of estimating said unknown component.

24. A wheel condition estimating apparatus for estimating a wheel condition in a wheel resonance system including a frictional characteristic between a tire and a road surface, comprising:

a detector configured to detect an output response to a vibration input to the wheel resonance system; and

an estimator configured to express a damping characteristic of said wheel resonance system during non-braking from the vibration input to the output response by a vibration transfer characteristic model including at least a physical quantity relating to ease of a slipping between the tire and the road surface as an unknown component of a wheel condition, and to estimate at least said unknown component which substantially satisfies the output response detected by said detector on the basis of the vibration transfer characteristic model.