Physical quantity estimating apparatus and tire state determining apparatus, and estimating method of same and determination method of same

• US 20030192375A1
• Filed: 04/10/2003
• Published: 10/16/2003
• Est. Priority Date: 04/11/2002
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Umeno, Takaji, Asano, Katsuhiro, Sugai, Masaru
• Granted Patent: US 6,871,530 B2
• Time in Patent Office: Days
• US Class Current: 73/146
• CPC Class Codes: B60C 11/246 Tread wear monitoring systems
• CPC Class Codes: B60C 23/061 by monitoring wheel speed measuring distance traversed on the ground by vehicles G01C22/00
• CPC Class Codes: B60T 2210/12 Friction
• CPC Class Codes: B60T 2240/04 Tire deformation
• 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
• CPC Class Codes: G01M 17/02 Tyres

Abstract

A physical quantity estimating apparatus and method that detects an acceleration and deceleration rate of a vehicle body and a rotational velocity of a wheel, estimates at least one of a tire radius of each wheel, a road surface μ gradient, and a spring constant of a combination spring which combines spring elements, with a distribution ratio of braking force and driving force to a front and rear wheel and a distribution ratio of a load on each wheel that is corrected according to the detected acceleration and deceleration rate, as known values, based on a wheel speed difference of any two wheels, during acceleration and deceleration of a vehicle, of an ideal vehicle model that takes into consideration a tire torsional spring element and a suspension longitudinal spring element and estimates a tire type based on the estimated road surface μ gradient and spring constant.

Claims

1. A physical quantity estimating apparatus, comprising:

an estimating portion that estimates at least one of a physical quantity relating to a tire radius of each wheel, a physical quantity relating to a road surface friction coefficient, and a physical quantity relating to a spring constant of a combination spring which combines spring elements, using a known value of a distribution ratio of a braking force and a driving force to each wheel and a known value of a distribution ratio of a load on each wheel, based on a wheel speed difference between any two wheels and the acceleration and deceleration rate of the vehicle during acceleration and deceleration of the vehicle.

2. The physical quantity estimating apparatus according to claim 1, wherein the physical quantity relating to the spring constant of the combination spring which combines spring elements of each wheel is estimated using the known value of the distribution ratio of the braking force and driving force to each wheel and the known distribution ratio of the load on each wheel, based on the wheel speed difference between any two wheels and the acceleration and deceleration rate of the vehicle during acceleration and deceleration of the vehicle, of an ideal vehicle model that takes into consideration a tire torsional spring element and a suspension longitudinal spring element of the vehicle.

3. The physical quantity estimating apparatus according to claim 2, further comprising:

a first detector that detects the acceleration and deceleration rate of the vehicle, and

a second detector that detects a wheel speed of the vehicle in order to obtain the wheel speed difference.

4. The physical quantity estimating apparatus according to claim 2, wherein the physical quantity relating to the tire radius is one of a radius ratio of a tire other than a reference tire to a radius of the reference tire and the tire radius obtained from the radius ratio, the physical quantity relating to the road surface friction coefficient is one of a reciprocal of a road surface friction coefficient gradient with respect to a slip rate and the road surface friction coefficient gradient obtained from the reciprocal, and the physical quantity relating to the spring constant is one of a reciprocal of the spring constant of a combination spring standardized by dividing the spring constant of the combination spring by a vehicle body weight and the spring constant of the combination spring obtained from the reciprocal of the spring constant.

5. The physical quantity estimating apparatus according to claim 1, wherein the physical quantity relating the tire radius of each wheel is estimated using a known value of the distribution ratio of the braking force and driving force to each wheel, and the known distribution ratio of the load on each wheel, based on the wheel speed difference between any two wheels and the acceleration and deceleration rate of the vehicle, during acceleration and deceleration of the vehicle, of an ideal vehicle model that takes into consideration a difference in the tire radius of the vehicle.

6. The physical quantity estimating apparatus according to claim 5, further comprising:

a first detector that detects the acceleration and deceleration rate of the vehicle; and

a second detector that detects a wheel speed of the vehicle in order to obtain the wheel speed difference.

7. The physical quantity estimating apparatus according to claim 5, wherein the physical quantity relating to the tire radius is one of a radius ratio of a tire other than a reference tire to a radius of the reference tire and the tire radius obtained from the radius ratio, the physical quantity relating to the road surface friction coefficient is one of a reciprocal of a road surface friction coefficient gradient with respect to a slip rate and the road surface friction coefficient gradient obtained from the reciprocal, and the physical quantity relating to the spring constant is one of a reciprocal of the spring constant of a combination spring standardized by dividing the spring constant of the combination spring by a vehicle body weight and the spring constant of the combination spring obtained from the reciprocal of the spring constant.

8. A tire state determining apparatus, comprising:

an estimating portion that estimates at least one of a physical quantity relating to a tire radius of each wheel, a physical quantity relating to a road surface friction coefficient, and a physical quantity relating to a spring constant of a combination spring which combines spring elements, using a known value of a distribution ratio of a braking force and a driving force to each wheel and a known distribution ratio of a load on each wheel, based on a wheel speed difference between any two wheels and the acceleration and deceleration rate of a vehicle during acceleration and deceleration of the vehicle; and

a determining portion that determines at least one of a tire type, a tire air pressure, and a tire wear state, based on at least one of the physical quantities estimated by the estimating portion.

9. The tire state determining apparatus according to claim 8, wherein the physical quantity relating to the spring constant of the combination spring which combines spring elements of each wheel is estimated using the known value of the distribution ratio of the braking force and driving force to each wheel and the known distribution ratio of the load on each wheel, based on the wheel speed difference between any two wheels and the acceleration and deceleration rate of the vehicle, during acceleration and deceleration of the vehicle, of an ideal vehicle model that takes into consideration a tire torsional spring element and a suspension longitudinal spring element of the vehicle.

10. The tire state determining apparatus according to claim 9, further comprising:

a first detector that detects the acceleration and deceleration rate of the vehicle; and

a second detector that detects a wheel speed of the vehicle in order to obtain the wheel speed difference.

11. The tire state determining apparatus according to claim 9, wherein the physical quantity relating to the tire radius is one of a radius ratio of a tire other than a reference tire to a radius of the reference tire and the tire radius obtained from the radius ratio, the physical quantity relating to the road surface friction coefficient is one of a reciprocal of a road surface friction coefficient gradient with respect to a slip rate and the road surface friction coefficient gradient obtained from the reciprocal, and the physical quantity relating to the spring constant is one of a reciprocal of the spring constant of a combination spring standardized by dividing the spring constant of the combination spring by a vehicle body weight and the spring. constant of the combination spring obtained from the reciprocal of the spring constant.

12. The tire state determining apparatus according to claim 9, wherein the estimating portion estimates two physical quantities from among the tire radius, the road surface friction coefficient, and the spring constant of the combination spring which combines spring elements;

and

the determining portion makes at least one determination from among a tire type determination based on the estimated road surface friction coefficient gradient and spring constant of the combination spring, a tire air pressure determination based on the estimated tire radius and spring constant of the combination spring, and a tire wear state determination based on the estimated tire radius and road surface friction coefficient gradient.

13. The tire state determining apparatus according to claim 9, wherein:

the determining portion determines the tire type based on the road surface friction coefficient gradient when the slip rate is near zero.

14. The tire state determining apparatus according to claim 9, wherein:

the determining portion calculates one of radius ratios k_m and k_rm of a plurality of tires other than the reference tire, to a radius R₀ of the reference tire, and the tire radii;

calculates one of reciprocals 1/β

_n and 1/β

_m of the road surface friction coefficient gradients with respect to slip rates of the plurality of tires, and the road surface friction coefficient gradients and

calculates one of reciprocals 1/k_stn and 1/k_stm of the spring constants of combination springs standardized by dividing the spring constants of the combination springs of the plurality of tires by a vehicle body weight, and the spring constants of the combination springs, based on an expression

$\begin{array}{cc}{R}_0<br><br>\left(k_m<br><br>{\mathrm{\omega <br><br>}}_n-k_{r<br><br>\text{\hspace{1em}<br><br>}<br><br>m}<br><br>{\mathrm{\omega <br><br>}}_m\right)=\left(\frac{k_{f<br><br>\text{\hspace{1em}<br><br>}<br><br>n}<br><br>v_a}{k_{\mathrm{\omega <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>n}<br><br>{\mathrm{\beta <br><br>}}_n}-\frac{k_{f<br><br>\text{\hspace{1em}<br><br>}<br><br>m}<br><br>v_a}{k_{\mathrm{\omega <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>n}<br><br>{\mathrm{\beta <br><br>}}_m}\right)<br><br>g_v+\left(\frac{k_{f<br><br>\text{\hspace{1em}<br><br>}<br><br>n}}{k_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>t<br><br>\text{\hspace{1em}<br><br>}<br><br>n}}-\frac{k_{f<br><br>\text{\hspace{1em}<br><br>}<br><br>m}}{k_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>t<br><br>\text{\hspace{1em}<br><br>}<br><br>m}}\right)<br><br>d_v& \text{\hspace{1em}<br><br>}\end{array}$

where ω

n and ω

m represent angular velocities of the plurality of wheels;

v_a represents an average wheel speed of the four wheels;

g_v represents a ratio of the vehicle body acceleration rate to a gravitational force acceleration rate; and

d_v represents a derivative of the vehicle body acceleration rate that has been standardized by a gravitational acceleration rate.

15. The tire state determining apparatus according to claim 9, further comprising:

a notifying apparatus that notifies an occupant of at least one of the tire type, the value of the tire air pressure, and the tire wear state.

16. The tire state determining apparatus according to claim 8, wherein the physical quantity relating to the tire radius of each wheel is estimated using the known value of the distribution ratio of the braking force and driving force to each wheel and the known distribution ratio of the load on each wheel, based on the wheel speed difference between any two wheels and the acceleration and deceleration rate of the vehicle, during acceleration and deceleration of the vehicle, of an ideal vehicle model that takes into consideration a difference in the tire radius of the vehicle.

17. The tire state determining apparatus according to claim 16, further comprising:

a first detector that detects the acceleration and deceleration rate of the vehicle, and

a second detector that detects a wheel speed of the vehicle in order to obtain the wheel speed difference.

18. The tire state determining apparatus according to claim 16, wherein the physical quantity relating to the tire radius is one of a radius ratio of a tire other than a reference tire to a radius of the reference tire and the tire radius obtained from the radius ratio, the physical quantity relating to the road surface friction coefficient is one of a reciprocal of a road surface friction coefficient gradient with respect to a slip rate and the road surface friction coefficient gradient obtained from the reciprocal, and the physical quantity relating to the spring constant is one of a reciprocal of the spring constant of a combination spring standardized by dividing the spring constant of the combination spring by a vehicle body weight and the spring constant of the combination spring obtained from the reciprocal of the spring constant.

19. The tire state determining apparatus according to claim 16, wherein:

the estimating portion estimates two physical quantities from among the tire radius, the road surface friction coefficient, and the spring constant of the combination spring which combines spring elements; and

the determining portion makes at least one determination from among a tire type determination based on the estimated road surface friction coefficient gradient and spring constant of the combination spring, a tire air pressure determination based on the estimated tire radius and spring constant of the combination spring, and a tire wear state determination based on the estimated tire radius and road surface friction coefficient gradient.

20. The tire state determining apparatus according to claim 16, wherein:

the determining portion determines the tire type based on the road surface friction coefficient gradient when the slip rate is near zero.

21. The tire state determining apparatus according to claim 16, wherein:

the estimating portion calculates one of radius ratios k_m and k_rm of a plurality of tires other than the reference tire, to a radius R₀ of the reference tire, and the tire radii;

calculates one of reciprocals 1/β

_n and 1/β

_m of the road surface friction coefficient gradients with respect to slip rates of the plurality of tires, and the road surface friction coefficient gradients; and

calculates one of reciprocals 1/k_stn and 1/k_stm of the spring constants of combination springs standardized by dividing the spring constants of the combination springs of the plurality of tires by a vehicle body weight, and the spring constants of the combination springs, based on an expression

$\begin{array}{cc}{R}_0<br><br>\left(k_m<br><br>{\mathrm{\omega <br><br>}}_n-k_{r<br><br>\text{\hspace{1em}<br><br>}<br><br>m}<br><br>{\mathrm{\omega <br><br>}}_m\right)=\left(\frac{k_{f<br><br>\text{\hspace{1em}<br><br>}<br><br>n}<br><br>v_a}{k_{\mathrm{\omega <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>n}<br><br>{\mathrm{\beta <br><br>}}_n}-\frac{k_{f<br><br>\text{\hspace{1em}<br><br>}<br><br>m}<br><br>v_a}{k_{\mathrm{\omega <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>n}<br><br>{\mathrm{\beta <br><br>}}_m}\right)<br><br>g_v+\left(\frac{k_{f<br><br>\text{\hspace{1em}<br><br>}<br><br>n}}{k_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>t<br><br>\text{\hspace{1em}<br><br>}<br><br>n}}-\frac{k_{f<br><br>\text{\hspace{1em}<br><br>}<br><br>m}}{k_{s<br><br>\text{\hspace{1em}<br><br>}<br><br>t<br><br>\text{\hspace{1em}<br><br>}<br><br>m}}\right)<br><br>d_v& \text{\hspace{1em}<br><br>}\end{array}$

where, ω

n and ω

m represent angular velocities of the plurality of wheels;

v_a represents an average wheel speed of the four wheels;

g_v represents a ratio of the vehicle body acceleration rate to a gravitational force acceleration rate; and

d_v represents a derivative of the vehicle body acceleration rate that has been standardized by the gravitational acceleration rate.

22. The tire state determining apparatus according to claim 16, further comprising:

a notifying apparatus that notifies an occupant of at least one of the tire type, the value of the tire air pressure, and the tire wear state.

23. A physical quantity estimating method, comprising the step of:

estimating at least one of a physical quantity relating to a tire radius of each wheel, a physical quantity relating to a road surface friction coefficient, and a physical quantity relating to a spring constant of a combination spring which combines spring elements, using a known value of a distribution ratio of a braking force and a driving force to each wheel and a known distribution ratio of a load on each wheel, based on a wheel speed difference between any two wheels and the acceleration and deceleration rate of a vehicle during acceleration and deceleration of the vehicle.

24. The physical quantity estimating method according to claim 23, wherein the physical quantity relating to the spring constant of the combination spring which combines spring elements of each wheel is estimated using the known value of the distribution ratio of the braking force and driving force to each wheel and the known distribution ratio of the load on each wheel, based on the wheel speed difference between any two wheels and the acceleration and deceleration rate of the vehicle, during acceleration and deceleration of the vehicle, of an ideal vehicle model that takes into consideration a tire torsional spring element and a suspension longitudinal spring element of the vehicle.

25. The physical quantity estimating method according to claim 24, wherein the physical quantity relating to the tire radius is one of a radius ratio of a tire other than a reference tire to a radius of the reference tire and the tire radius obtained from the radius ratio, the physical quantity relating to the road surface friction coefficient is one of a reciprocal of a road surface friction coefficient gradient with respect to a slip rate and the road surface friction coefficient gradient obtained from the reciprocal, and the physical quantity relating to the spring constant is one of a reciprocal of the spring constant of a combination spring standardized by dividing the spring constant of the combination spring by a vehicle body weight and the spring constant of the combination spring obtained from the reciprocal of the spring constant.

26. The physical quantity estimating method according to claim 23, wherein the physical quantity relating the tire radius of each wheel is estimated using the known value of the distribution ratio of the braking force and driving force to each wheel, and the known distribution ratio of the load on each wheel, based on a wheel speed difference between any two wheels and the acceleration and deceleration rate of the vehicle, during acceleration and deceleration of the vehicle, of an ideal vehicle model that takes into consideration a difference in the tire radius of the vehicle.

27. The physical quantity estimating method according to claim 26, wherein the physical quantity relating to the tire radius is one of a radius ratio of a tire other than a reference tire to a radius of the reference tire and the tire radius obtained from the radius ratio, the physical quantity relating to the road surface friction coefficient is one of a reciprocal of a road surface friction coefficient gradient with respect to a slip rate and the road surface friction coefficient gradient obtained from the reciprocal, and the physical quantity relating to the spring constant is one of a reciprocal of the spring constant of a combination spring standardized by dividing the spring constant of the combination spring by a vehicle body weight and the spring constant of the combination spring obtained from the reciprocal of the spring constant.

28. A tire state determination method, comprising the steps of:

estimating at least one of a physical quantity relating to a tire radius of each wheel, a physical quantity relating to a road surface friction coefficient, and a physical quantity relating to a spring constant of a combination spring which combines spring elements, using a known value of a distribution ratio of a braking force and a driving force to each wheel and a known distribution ratio of a load on each wheel, based on a wheel speed difference between any two wheels and the acceleration and deceleration rate of a vehicle during acceleration and deceleration of the vehicle; and

determining at least one of a tire type, a tire air pressure, and a tire wear state, based on at least one of the physical quantities estimated by the estimating portion.

29. The tire state determination method according to claim 28, wherein the physical quantity relating to the spring constant of the combination spring which combines spring elements of each wheel is estimated using the known value of the distribution ratio of the braking force and driving force to each wheel and the known distribution ratio of the load on each wheel, based on the wheel speed difference between any two wheels and the acceleration and deceleration rate of the vehicle, during acceleration and deceleration of the vehicle, of an ideal vehicle model that takes into consideration a tire torsional spring element and a suspension longitudinal spring element of the vehicle.

30. The tire state determination method according to claim 29, wherein the physical quantity relating to the tire radius is one of a radius ratio of a tire other than a reference tire to a radius of the reference tire and the tire radius obtained from the radius ratio, the physical quantity relating to the road surface friction coefficient is one of a reciprocal of a road surface friction coefficient gradient with respect to a slip rate and the road surface friction coefficient gradient obtained from the reciprocal, and the physical quantity relating to the spring constant is one of a reciprocal of the spring constant of a combination spring standardized by dividing the spring constant of the combination spring by a vehicle body weight and the spring constant of the combination spring obtained from the reciprocal of the spring constant.

31. The tire state determination method according to claim 29, wherein the estimating process estimates two physical quantities from among the tire radius, the road surface friction coefficient, and the spring constant of the combination spring which combines the spring elements and the determining process makes at least one determination from among a tire type determination based on the estimated road surface friction coefficient gradient and spring constant of the combination spring, a tire air pressure determination based on the estimated tire radius and spring constant of the combination spring, and a tire wear state determination based on the estimated tire radius and road surface friction coefficient gradient.

32. The tire state determination method according to claim 29, wherein the tire type is determined based on the road surface friction coefficient gradient when the slip rate is near zero.

33. The tire state determination method according to claim 29, wherein the estimating process calculates one of radius ratios k_m and k_rm of a plurality of tires other than the reference tire, to a radius R₀ of the reference tire, and the tire radii, calculates one of reciprocals 1/β

_n and 1/β

_m of the road surface friction coefficient gradients with respect to slip rates of the plurality of tires, and the road surface friction coefficient gradients and calculates one of reciprocals 1/k_stn and 1/k_stm of the spring constants of combination springs standardized by dividing the spring constants of the combination springs of the plurality of tires by a vehicle body weight, and the spring constants of the combination springs, based on an expression

34. The tire state determination method according to claim 28, wherein the physical quantity relating to the tire radius of each wheel is estimated using the known value of the distribution ratio of the braking force and driving force to each wheel and the known distribution ratio of the load on each wheel, based on the wheel speed difference between any two wheels and the acceleration and deceleration rate of the vehicle, during acceleration and deceleration of the vehicle, of an ideal vehicle model that takes into consideration a difference in the tire radius of the vehicle.

35. The tire state determination method according to claim 34, wherein the physical quantity relating to the tire radius is one of a radius ratio of a tire other than a reference tire to a radius of the reference tire and the tire radius obtained from the radius ratio, the physical quantity relating to the road surface friction coefficient is one of a reciprocal of a road surface friction coefficient gradient with respect to a slip rate and the road surface friction coefficient gradient obtained from the reciprocal, and the physical quantity relating to the spring constant is one of a reciprocal of the spring constant of a combination spring standardized by dividing the spring constant of the combination spring by a vehicle body weight and the spring constant of the combination spring obtained from the reciprocal of the spring constant.

36. The tire state determination method according to claim 34, wherein the estimating process estimates two physical quantity from among the tire radius, the road surface friction coefficient, and the spring constant of the combination spring which combines spring elements and the determining process makes at least one determination from among a tire type determination based on the estimated road surface friction coefficient gradient and spring constant of the combination spring, a tire air pressure determination based on the estimated tire radius and spring constant of the combination spring, and a tire wear state determination based on the estimated tire radius and road surface friction coefficient gradient.

37. The tire state determination method according to claim 34, wherein the tire type is determined based on the road surface friction coefficient gradient when the slip rate is near zero.

38. The tire state determination method according to claim 34, wherein the estimating process calculates one of radius ratios k_m and k_r of a plurality of tires other than the reference tire, to a radius R₀ of the reference tire, and the tire radii, calculates one of reciprocals 1/β

_n and 1/β

_m of the road surface friction coefficient gradients with respect to slip rates of the plurality of tires, and the road surface friction coefficient gradients and calculates one of reciprocals 1/k_stn and 1/k_stm of the spring constants of combination springs standardized by dividing the spring constants of the combination springs of the plurality of tires by a vehicle body weight, and the spring constants of the combination springs, based on an expression