Automatic control method, usable in particular for maintaining the slip of a tire at an optimum level

• US 20040024514A1
• Filed: 06/12/2003
• Published: 02/05/2004
• Est. Priority Date: 06/13/2002
• Status: Active Grant

• Current Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Original Assignee: Michelin Recherche et Technique SA (Compagnie Generale DES Etablissements Michelin SCA)
• Inventors: Levy, Georges, Fangeat, Nicolas
• Granted Patent: US 6,923,050 B2
• Time in Patent Office: Days
• US Class Current: 701/82
• 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
• CPC Class Codes: G05B 13/024 in which a parameter or coefficient is automatically adjusted to optimise the performance

Abstract

Automatic control method for a phenomenon of which a parameter Y varies as a function of a parameter X according to a course exhibiting a rise, an extremum and a fall, in which the value of the parameter X is automatically controlled to maintain the value of a parameter Y at an optimum value, comprising the following steps:

Determining estimations or measurements (X_i, Y_i) for at least one pair of values in a coordinate system having an origin;

Determining the corresponding values of the slope α_i of the straight line passing through the origin and through (X_i, Y_i);

Calculating coefficients A_p by direct calculation or by a regression from a sufficient number of pairs with (α_i, X_i) so as to model a variation curve α_i=(X_i, A_p);

Calculating a target value X^Target by using a predetermined Invariant “Invt”.

Application to tests and the functioning of the tire on a vehicle, for example for controlling the grip on braking, with Y being the coefficient of friction and X being the slip of the tire under torque.

Claims

1. An automatic control method for a phenomenon of which a parameter Y varies as a function of a parameter X according to a course exhibiting a rise, an extremum and a fall, in which the value of the parameter X is automatically controlled to maintain the value of a parameter Y at an optimum value, comprising the following steps:

(a) determining estimations or measurements (X_i, Y_i) for at least one pair “

i”

of values in a coordinate system having an origin;

(b) determining the corresponding values of the slope oc of the straight line passing through the origin and through (X_i, Y_i);

(c) calculating coefficients A_p by direct calculation or by a regression from a sufficient number of pairs with (α

_i, X_i) so as to model a variation curve α

_i=f(X_i, A_p); and

(d) calculating a target value X_max by using a predetermined Invariant “

Invt”

.

2. An automatic control method according to claim 1, in which the value of the parameter X is automatically controlled so as to maintain the value thereof at X_max.

3. An automatic control method according to claim 1, in which the Invariant is determined as follows:

4. An automatic control method according to claim 3, in which the value of p is between 0.25 and 0.75.

5. An automatic control method according to claim 4, in which p is 0.5.

6. An automatic control method according to claim 1, in which the slope a(is determined by direct calculation α

_i=Y_i/X_i.

7. An automatic control method according to claim 1, in which the slope α

_i is determined by carrying out a suitable regression.

8. An automatic control method according to claim 1, in which a linear regression is carried out:

9. An automatic control method according to claim 1, in which two particular coefficients A_p, the coefficients A and B, are calculated by the following linear regression, applied to “

n”

measured or estimated points;

10. An automatic control method according to claim 1, in which the two particular coefficients A_P, the coefficients A and B, are calculated by the following exponential regression, applied to “

n”

measured or estimated points;

11. An automatic control method according to claim 9, in which X_max is calculated as follows:

12. An automatic control method according to claim 10, in which X_max is calculated as follows:

13. An automatic control method according to claim 9, in which in addition Y_max is determined as follows, where Y^coeff_—

^lin is an experimentally adjusted coefficient;

Y_max=Y<sup>Coeff_—

lin</sup>·

X_max·

(A^Lin·

X_max+B^Lin)

14. An automatic control method according to claim 10, in which in addition Y_max is determined as follows, where Y^coeff_—

^exp is an experimentally adjusted coefficient;

Y_max=Y<sup>Coeff_—

exp</sup>·

X_max·

e<sup>AExp·

X</sup>_max+B^EXP

15. An automatic control method according to claim 1, further comprising the step of using the Invariant “

Invt”

as an adjustment variable to refine the method.

16. A ground contact system in which a characteristic parameter Q of the functioning of a tire on a vehicle in movement varies as a function of a parameter P according to a course exhibiting a rise, an extremum and a fall, the value of said parameter P being imposed by a controller, acting on at least one of the elements chosen from the group comprising the torque applied to the tire, the steer angle of the tire, the camber angle of the tire and the vertical force applied on the tire, in order to maintain the value of the parameter Q at a chosen value, in which the controller includes means for:

(a) determining estimations or measurements (P_i, Q_i) for at least one pair “

i”

of values in a coordinate system having an origin;

(b) determining the corresponding values of the slope β

_i of the straight line passing through the origin and through (P_i, Q_i);

(c) calculating coefficients A_p by direct calculation or by a regression from a sufficient number of pairs with (β

_i, P_i) so as to model a variation curve β

_i=f(P_i, A_p);

(d) calculating a target value P^Target by using a predetermined Invariant “

Invt”

; and

(e) changing into “

active”

mode when the absolute value of the difference between P^{Instantaneous} and P^Target is more than a predetermined threshold.

17. A ground contact system according to claim 16, wherein the controller further comprises means for using the Invariant “

Invt”

as an adjustment variable to refine the system.

18. A method for controlling the functioning of a tire in terms of slip, comprising the following steps:

(a) determining estimations or measurements (G_i, μ

_i) for at least one pair “

i”

of values in a coordinate system having an origin;

(b) determining the corresponding values of the slope α

_i of the straight line passing through the origin and through (G_i, μ

_i); and

(c) calculating coefficients A_p by direct calculation or by a regression from a sufficient number of pairs with (α

_i, G_i) so as to model a variation curve α

_i=f(G_i, A_p).

19. A method for controlling the functioning of a tire in terms of slip according to claim 18, in which an estimation of an optimum slip G^Opt is made by using a predetermined Invariant “

Invt”

.

20. A method for controlling the functioning of a tire in terms of slip according to claim 19, further comprising the step of using the Invariant “

Invt”

as an adjustment parameter to refine the method.

21. A method for controlling the functioning of a tire in terms of slip according to claim 19, in which the slip G is automatically controlled so as to maintain it at G^Opt.

22. A method for controlling the functioning of a tire in terms of slip according to claim 19, in which the value of “

Invt”

is substantially 0.58.

23. A method for controlling the functioning of a tire in terms of slip according to claim 19, in which the Invariant is determined as follows:

24. A method for controlling the functioning of a tire in terms of slip according to claim 23, in which the value of p is between 0.25 and 0.75.

25. A method for controlling the functioning of a tire in terms of slip according to claim 24, in which p is 0.5.

26. A method for controlling the functioning of a tire in terms of slip according to claim 19, in which the slope α

_i is determined by direct calculation α

_i=μ

_i/G_i.

27. A method for controlling the functioning of a tire in terms of slip according to claim 19, in which the slope α

_i is determined by carrying out a suitable regression.

28. A method for controlling the functioning of a tire in terms of slip according to claim 19, in which a linear regression is carried out:

29. A method for controlling the functioning of a tire in terms of slip according to claim 19, in which the two particular coefficients A_p, the coefficients A and B, are calculated by the following linear regression, applied to “

n”

measured or estimated points;

30. A method for controlling the functioning of a tire in terms of slip according to claim 19, in which the two particular coefficients A_p, the coefficients A and B, are calculated by the following exponential regression, applied to “

n”

measured or estimated points;

31. A method for controlling the functioning of a tire in terms of slip according to claim 29, in which G^Opt is calculated as follows:

32. A method for controlling the functioning of a tire in terms of slip according to claim 30, in which G^Opt is calculated as follows:

33. A method for controlling the functioning of a tire in terms of slip according to claim 29, in which in addition the value of μ

corresponding to G^Opt is determined as follows;

μ

=μ

<sup>Coeff_—

lin</sup>·

G^Opt·

(A^Lin·

G^Opt+B^Lin)

34. A method for controlling the functioning of a tire in terms of slip according to claim 30, in which in addition μ

_max is determined as follows;

μ

_max=μ

<sup>Coeff_—

exp</sup>·

G^Opt·

e<sup>AExp·

GOpt+BExp</sup>

35. A method for controlling the functioning of a tire, including a phase for predicting the value of the drift angle δ

of a tire where the lateral force is maximal, comprising the following steps;

(a) determining estimations (δ

_i, F_i) for at least one pair “

i”

of values in a coordinate system having an origin;

(b) determining the corresponding values of the slope α

_i of the straight line passing through the origin and through (δ

_i, F_i); and

(c) calculating coefficients A_p by direct calculation or by a regression from a sufficient number of pairs with (α

_i, δ

_i) so as to model a variation curve α

_i=f(δ

_i, A_p).

36. A method for controlling the functioning of a tire according to claim 35, including in addition the following steps:

(d) calculating a _value of the drift angle δ

^Opt by using a predetermined Invariant “

Invt”

; and

(e) producing a warning signal when the drift angle δ

is close to δ

^Opt.

37. A method for controlling the functioning of a tire according to claim 36, in which a selected parameter is automatically controlled so as to maintain it at δ

^Opt.

38. A method for controlling the functioning of a tire according to claim 36, as in which, in the event of the occurrence of the warning signal, a selected parameter is automatically controlled so as to reduce the drift angle δ

.

39. A method for controlling the functioning of a tire according to claim 36, in which the Invariant is determined as follows:

40. A method for controlling the functioning of a tire according to claim 39, in which the value of p is between 0.25 and 0.75.

41. A method for controlling the functioning of a tire according to claim 40, in which p is 0.5.

42. A method for controlling the functioning of a tire according to claim 36, in which the slope α

_i is determined by direct calculation α

_i=F_i/δ

_i.

43. A method for automatically controlling the drift angle δ

of a tire according to claim 36, in which the slope α

_i is determined by carrying out a suitable regression.

44. A method for controlling the functioning of a tire according to claim 36, in which a linear regression is carried out:

45. A method for controlling the functioning of a tire according to claim 36, in which the two particular coefficients A_p, the coefficients A and B, are calculated by the following linear regression, applied to “

n”

measured or estimated points;

46. A method for controlling the functioning of a tire according to claim 36, in which the two particular coefficients A_p, the coefficients A and B, are calculated by the following exponential regression:

47. A method for controlling the functioning of a tire according to claim 36, including the additional step of using the Invariant “

Invt”

as an adjustment variable to refine the method.

48. A method for controlling the functioning of a tire according to claim 45, in which δ

^Opt is calculated as follows;

49. A method for controlling the functioning of a tire according to claim 46, in which δ

^Opt is calculated as follows;

50. A method for controlling the functioning of a tire according to claim 45, in which in addition F^Target is determined as follows:

F^Target=F<sup>Coeff_—

lin</sup>·

δ

^Opt·

(A^Lin·

δ

^Opt+B^Lin)

51. A method for controlling the functioning of a tire according to claim 46, in which in addition F^Target is determined as follows:

F^Target=F<sup>Coeff_—

exp</sup>·

δ

^Opt·

e<sup>AExp·

δ

Opt+BExp</sup>

59. A test method according to one of claims 52 and 56, for automatically controlling the drift angle δ

of a tire according to claim 35, in which the value of p is between 0.25 and 0.75.

60. A test method according to one of claims 53 and 56, for automatically controlling the drift angle δ

of a tire according to claim 36, in which p is 0.5.

52. A method for testing a tire in terms of slip comprising the following steps:

(a) causing the tire to roll on a selected ground;

(b) applying a predetermined load F_Z1 to the tire;

(c) applying a predetermined slip to the tire;

(d) measuring or estimating the longitudinal force F^X1 of the tire;

(e) calculating a value of the coefficient of friction μ

₁=F_X1/F_Z1;

(f) repeating the previous steps for calculating at least one other value “

i”

of the coefficient of friction μ

_i for at least one other pair “

i”

of stresses F_Xi/F_Zi and measuring the associated slip G_i;

(g) determining for each of the calculated values of the coefficient of friction the slope α

_i of the straight line passing through the origin and through (G_i, μ

1);

(h) calculating coefficients A_p by direct calculation or by an appropriate regression from a sufficient number of pairs with (α

_i, G_i) so as to model a variation curve α

_i=f(G_i, A_p); and

(i) calculating an optimum slip enabling a predetermined value of the coefficient of friction G^Opt to be attained, by using a predetermined Invariant “

Invt”

.

53. A test method according to claim 52, in which the Invariant is determined as follows:

54. A test method according to claim 52, in which the Invariant “

Invt”

is used as a adjustment parameter to refine the method.

58. A test method according to one of claims 52 to 56, in which the coefficients A_p are calculated by a regression chosen from the group consisting of a linear regression and an exponential regression.

55. A method for testing a tire in terms of drift comprising the following steps:

(a) causing the tire to roll on the ground;

(b) applying a predetermined load F_Z1 to the tire;

(c) applying a predetermined drift angle δ

_i to the tire, such that the tire remains below the grip limit, and measuring or estimating the drift thrust F_i corresponding to said drift angle δ

_i;

(d) repeating the previous steps for calculating at least one other pair “

i of values (δ

_i, F_i);

(e) determining the corresponding values of the slope α

_i of the straight line passing through the origin and through (δ

_i, F_i);

(f) calculating coefficients A_p by direct calculation or by an appropriate regression from a sufficient number of pairs (α

_i, δ

_i) so as to model a variation curve α

_i=f(δ

_i, A_p); and

(g) calculating a value of the drift angle δ

^Opt by using a predetermined Invariant “

Invt”

.

56. A test method according to claim 55, in which the Invariant is determined as follows:

57. A test method according to claim 55, in which the Invariant “

Invt”

is used as an adjustment parameter to refine the method.

61. A method for automatically controlling the functioning of a tire in a given configuration, aimed at maintaining the functioning of a tire at a predetermined value of the coefficient of friction A, comprising the following steps:

(a) determining estimations or measurements (G_i, μ

_i) for a plurality of pairs “

i”

of values;

(b) calculating an estimation of the optimum slip of the tire G^Opt as a function of the intrinsic physical characteristics of the tire and the existing actual functioning configuration; and

(c) automatically controlling the configuration as a function of the difference between G_{instantaneous} and G^Opt.