Tire wear state estimation apparatus
An estimation apparatus includes a rotation speed acquisition unit, a driving force acquisition unit, a slip ratio calculation unit, a slope calculation unit, and an estimation unit. The rotation speed acquisition unit sequentially acquires rotation speeds of the tires. The driving force acquisition unit sequentially acquires a driving force of the vehicle. The slip ratio calculation unit calculates a slip ratio based on the sequentially-acquired rotation speeds of the tires. The slope calculation unit calculates the slope of the slip ratio with respect to the driving force based on a large number of data sets of the slip ratio and the driving force, as a regression coefficient representing a linear relationship between the slip ratio and the driving force. The estimation unit estimates the wear state of the tires based on the slope.
1. An estimation apparatus for estimating a wear state of tires mounted on a vehicle, comprising:
a rotation speed acquisition unit configured to sequentially acquire rotation speeds of the tires;
a driving force acquisition unit configured to sequentially acquire a driving force of the vehicle;
a turn radius acquisition unit configured to acquire a turn radius of the vehicle;
a slip ratio calculation unit configured to calculate a slip ratio based on the sequentially-acquired rotation speeds of the tires;
a first correction unit configured to correct the slip ratio based on first relationship information indicating a relationship between the turn radius and the slip ratio, and the turn radius at the time of correction;
a slope calculation unit configured to calculate a slope of a corrected slip ratio corrected by the first correction unit with respect to the driving force based on a large number of data sets of the corrected slip ratio and the driving force, as a regression coefficient indicating a linear relationship between the corrected slip ratio and the driving force; and
an estimation unit configured to estimate the wear state of the tires based on the slope.
2. The estimation apparatus according to claim 1 , further comprising
a lateral acceleration acquisition unit configured to sequentially acquire lateral acceleration applied to the vehicle,
wherein according to the sequentially-acquired lateral acceleration, the slip ratio calculation unit sequentially selects and acquires any one from a group consisting of a first slip ratio, a second slip ratio, and a third slip ratio, the first slip ratio being the slip ratio of the tires calculated based on a rotation speed of a left tire among the sequentially-acquired rotation speeds of the tires, the second slip ratio being the slip ratio of the tires calculated based on a rotation speed of a right tire, and the third slip ratio being the slip ratio of the tires calculated based on an average rotation speed of the left and right tires.
3. The estimation apparatus according to claim 2 ,
wherein according to the lateral acceleration, the slip ratio calculation unit selects the first slip ratio when the vehicle performs a right turn, selects the second slip ratio when the vehicle performs a left turn, and selects the third slip ratio when the vehicle travels straight.
4. The estimation apparatus according to claim 3 ,
wherein the first relationship information is information in which the slip ratio is represented by a quadratic function of a reciprocal of the turn ratio.
5. The estimation apparatus according to claim 2 ,
wherein the first relationship information is information in which the slip ratio is represented by a quadratic function of a reciprocal of the turn ratio.
6. The estimation apparatus according to claim 1 ,
wherein the first relationship information is information in which the slip ratio is represented by a quadratic function of a reciprocal of the turn ratio.
7. The estimation apparatus according to claim 6 , further comprising:
a lateral acceleration acquisition unit configured to sequentially acquire lateral acceleration applied to the vehicle; and
a second correction unit configured to correct the corrected slip ratio corrected by the first correction unit based on second relationship information indicating a relationship between the lateral acceleration, the driving force, and the slip ratio, and the lateral acceleration and the driving force at the time of correction.
8. The estimation apparatus according to claim 7 ,
wherein the second relationship information is information in which the slip ratio is represented by a linear function of the driving force and the slope of the slip ratio with respect to the driving force is represented by a quadratic function of the lateral acceleration.
9. The estimation apparatus according to claim 1 , further comprising:
a lateral acceleration acquisition unit configured to sequentially acquire lateral acceleration applied to the vehicle; and
a second correction unit configured to correct the corrected slip ratio corrected by the first correction unit based on second relationship information indicating a relationship between the lateral acceleration, the driving force, and the slip ratio, and the lateral acceleration and the driving force at the time of correction.
10. The estimation apparatus according to claim 9 ,
wherein the second relationship information is information in which the slip ratio is represented by a linear function of the driving force and the slope of the slip ratio with respect to the driving force is represented by a quadratic function of the lateral acceleration.
11. A method for estimating a wear state of tires mounted on a vehicle, comprising:
sequentially acquiring rotation speeds of the tires;
sequentially acquiring a driving force of the vehicle;
acquiring a turn radius of the vehicle;
calculating a slip ratio based on the sequentially-acquired rotation speeds of the tires;
correcting the slip ratio based on relationship information indicating a relationship between the turn radius and the slip ratio, and the turn radius at the time of correction;
calculating a slope of a corrected slip ratio with respect to the driving force based on a large number of data sets of the corrected slip ratio and the driving force, as a regression coefficient indicating a linear relationship between the corrected slip ratio and the driving force; and
estimating the wear state of the tires based on the slope.
12. An estimation apparatus for estimating a wear state of tires mounted on a vehicle, comprising:
a rotation speed acquisition unit configured to sequentially acquire rotation speeds of the tires;
a driving force acquisition unit configured to sequentially acquire a driving force of the vehicle;
a lateral acceleration acquisition unit configured to sequentially acquire lateral acceleration applied to the vehicle;
a slip ratio calculation unit configured to calculate a slip ratio based on the sequentially-acquired rotation speeds of the tires;
a correction unit configured to correct the slip ratio based on relationship information indicating a relationship between the lateral acceleration, the driving force, and the slip ratio, and the lateral acceleration and the driving force at the time of correction;
a slope calculation unit configured to calculate a slope of a corrected slip ratio corrected by the correction unit with respect to the driving force based on a large number of data sets of the corrected slip ratio and the driving force, as a regression coefficient indicating a linear relationship between the corrected slip ratio and the driving force; and
an estimation unit configured to estimate the wear state of the tires based on the slope.
13. The estimation apparatus according to claim 12 , wherein according to the sequentially-acquired lateral acceleration, the slip ratio calculation unit sequentially selects and acquires any one from a group consisting of a first slip ratio, a second slip ratio, and a third slip ratio, the first slip ratio being the slip ratio of the tires calculated based on a rotation speed of a left tire among the sequentially-acquired rotation speeds of the tires, the second slip ratio being the slip ratio of the tires calculated based on a rotation speed of a right tire, and the third slip ratio being the slip ratio of the tires calculated based on an average rotation speed of the left and right tires.
14. The estimation apparatus according to claim 12 ,
wherein the relationship information is information in which the slip ratio is represented by a linear function of the driving force and the slope of the slip ratio with respect to the driving force is represented by a quadratic function of the lateral acceleration.